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A study on hydraulically pressed microwave oven dried onionsproximate analysis - sensory evaluations

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CHAPMAN
DEPARTMENT
A_ STUDY
ON
OF
SCIENCE
HYDRAULICALLY
OVEN
PROXIMATE
FOOD
COLLEGE
DRIED
AND
PRESSED
NUTRITION
MICROWAVE
ONIONS
ANALYSIS - SENSORY
EVALUATION
A thesis submitted in partial fulfillment of the
requirments of the Degree of Master of Science
in
Science and Nutrition
by
Vassiliki I. Saliverou
May
1987
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Food
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The thesis of Vassiliki I. Saliverou has been approved
by:
Walter L. Clark, Ph.D
Fred
Caporaso, Ph.D
UL_£/>?.
Louis B. Rockland, Ph.D
Chapman
May
College
1987
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Dedicated to my Father
Ioannis Saliveros
who inspired me in the ambition
of
acquiring knowledge.
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Acknowledgements
I
Dr.
would
Walter
throughout
like
Clark
this
Dr. Fred Caporaso
advice. Also, I
Inc. and
to
for
express my
his
project.
sincere
support,
Moreover, I
help
gratitude to
and
guidance
would like to thank
and Dr. Louis Rockland for their valuable
acknowledge the
generosity
of Gilroy Foods
Dr. Otmar Silberstein for providing the raw onion
sample and the commercially dehydrated product.
i
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Abstract
This study attempted to obtain a flavor improved
hydraulically pressed microwave oven dried onion product. It
was compared with commercially dried onions, pressed air
dried onions and fresh onions. Studies included comparisons
of proximate analysis,
(moisture, ash, fat, protein), water
activity and sensory evaluation. A flavor profile test, a
ranking test and an intensity scaling test applied on a
trained panel, and a hedonic scaling consumer test were
conducted.
The pressed microwave oven dried onion sample was of
comparable compositional quality to the fresh, commercially
dried and pressed air dried samples in respect to moisture,
ash and protein content. Fat determination showed increased
fat values in both pressed samples. Water activity experiment
indicated that the pressed microwave oven dried sample was
potentially stable. The trained sensory panel concluded
that there was no significant difference between the three
dried onion samples in respect to their aroma intensity.
These results were verified by a consumer test. Flavor
improvement was not observed, but the pressed microwave oven
dried samples were comparable with the commercially dried
onion samples.
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Table of contents
Acknowledgements........................................
Page
i
Abstract.................................................
ii
Table of Co ntents........
iii
List of Fi gur es ......................................
iv
List of T a b l e s ..........................................
v
Chapter
1
Introduction.....................................
1
2
Review of Literature............................
3
I
Commercially Processed Onion Fo rms ........
3
II
Onion Composition...........................
7
III The Lacrimatory F a c t o r .....................
11
3
Objectives................. ......................
15
4
Material and M et h o d s ............................
16
I
Primary Procedures.........................
16
II
Proximate Ana l y s i s ..........................
19
III Water Activit y..............................
23
IV
24
Sensory Evaluation.........................
5
Experimental Data, Results
and Discusion......
30
6
Summary^ Conclusions
andRecomMendations.......
54
List of References......................................
56
App endix.................................................
58
iii
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List of Figures
Figures
Page
1
Sulfur Compounds Extracted from O nio ns ........... 13
2
Moisture Content of Dried Onion Samples
Adjusted to a Water Activity of 0 . 5 7 5 .....
iv
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41
List of Tables
Table
Page
1
Onion Composition
.................................
7
2
Onion Mineral Composition.........................
9
3
Onion Vitamin Composition.........................
10
4
Pressed Microwaved Air Dried Onion Samples......
18
5
Onion Weight Loss After Pressing and Air Drying..
6
Fresh Pressed Onions Dried by Microwave Energy...
7
Moisture Determination of Oni ons .................
33
8
Ash Determination of O nion s.......................
34
9
Crude Fat Determination of Onions................
36
10
Crude Protein Determination of O n i o n s............
38
11
Moisture Content of Dried Onion Samples Having
30
31
0.575 Water Ac tivity.............................
40
12
Aroma Profile Evaluation..........................
42
13
Color Ranking Scores...............................
43
14
Aroma Intensity Ranking Scores....................
43
15
Partical Size and Shape Ranking S cores
....
44
16
Off Aroma Ranking Scores..........................
44
17
Aroma Closer to Fresh Ranking S cores..............
45
18
Texture Ranking Scores.............................
45
19
Overall Appearance Ranking Scores................
46
20
Aroma Intensity Scaling Scores....................
47
21
Aroma Intensity Scaling Analysis Of V a r i a n c e
47
22
Color Intensity Scaling Scores....................
48
23
Color Intensity Analysis of Var iance ..............
49
v
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24
Off Aroma Intensity Scaling Scores...............
50
25
Off Aroma Intensity Analysis of Variance........
50
26
Hedonic Scaling Evaluation Scores................
51
27
Hedonic Scaling Analysis of Variance
......
53
28
Cellulose Experimental Results...................
58
vi
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CHAPTER
1
Introduction
It is unknown when people discovered that the removal of
water can increase the shelf-life of a food. There are
indications that Inca Indians were the first, 3.000 years
ago, to produce sun-dried food. Dried grapes and figs are
mentioned in the Bible. Universally, farmers sun-dry
many of their crops.
Drying was promoted by military need for foods with low
volume and weight.
After
World War II, hot air replaced sun drying.
However, the official U.S. Agriculture manuals on dehydration
were published in 1941. The primary products of dehydration
included potatoes, onions, garlic and chili peppers.
Onion technology goes back to the early 1900's, when
dehydration was carried out in cabinet dryers, which yielded
poor quality products. In 1953, the Proctor and Schwartz Co
developed a three-stage dryer. Most of the onion dehydrators
use multistage dryers which reduce energy cost by air
recirculation.
Statistics show that drying food in the future is not
going to grow at the same rate as in the past. Good quality
products which can solve the problems of time preparation,
camping, and instant cooking, are going to be in demand.
Dehydrators basicly face increased energy costs, so that
1
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their methods will be restudied, along with studies on
solar and microwave drying.
It is understood that the dehydration industries may
adopt expensive drying techniques if such methods provide
high quality products and which have a high market value
and demand (Labuza, 1976) .
2
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CHAPTER
2
Review of Literature
I. Commercially Processed Onion Forms
A. In General
The Allium cepa, the onion, has been an important
vegetable for many years. Onions are easily shipped between
countries, where they are used for seasoning of prepared
canned, frozen or dehydrated foods. Major onion-producing
countries include the United States, Egypt, Japan, Taiwan,
Turkey, Italy, Mexico, China and Sudan. In California, there
is a production of 750 million pounds of fresh onion (1973) ,
half of which became dehydrated (Luh and Woodroof, 1978) .
A good quality raw material is of special importance in
the dehydration industry. Onions to be dehydrated must have
the following special characteristics:
1. A high solids content (5-20%), because the cost of
the processing is determined from the weight of the product.
2. High pungency, because the dehydrated product is
usually used as flavoring agent and some of the original
pungency is lost through processing.
3. White flesh to give product with quality color (Luh
and Woodroof, 1978).
Bulbs can be stored better at temperatures 0-7 or 25-35
degrees Celsius for 3-6 months. Storage at 15-21 degrees
results in sprouting (Yamaguchi, 1983) .
3
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B. Dehydration
The dehydration of onions begins with sorting. Primarly
the roots and tops are cut off from the bulb, then the onions
pass through high-pressure washers which remove the outer
skin. Some other methods use a flame-peeler which burns off
the outer shells and the roots. After peeling, the onions are
sliced parallel to the vertical axis. Slicing knives are kept
sharp to avoid crushing the onion tissue to avoid the
begining of the enzymatic odor reaction and loss of pungency.
Later, the slices are spred on multi-stage continuous belt
conveyors, where hot air is blown upward or downward to the
sections. The temperature of the hot air is reduced from 180
to 130 degrees Fahrenheit. The product leaves the dryer with
moisture 6%-9% at about 6-16 hours. The final product moves
to a finishing bin where air of 110 degrees F blows
vertically and reduces the moisture content of the dried
onion to 4%. It is then packaged and stored.
Commercially, dried onions can be chopped, minced,
granulated and powdered (Luh and Woodroof, 1978) .
C. Toasted Dehydrated Onion
Onions contain reducing sugars which can participate in
a Maillard reaction at the last steps of dehydration. High
drying temperatures create an over—brown product which has a
characteristic toasted flavor. This type is used for sauted
onion flavored products and is available with lightly or
4
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heavily toasted quality.
The previously dehydrated onions are further heated at
100-175 degrees Celsius for about 30 hours. Due to varying
sugar co nte nt, some onions give unevenly colored toasted
products
(Heath, 1981) .
D. Onion Salt
It is a mixture of onion powder and salt. Sometimes, it
contains an anticaking agent like starch, tricalcium
phosphate or silicon oxide (Heath, 1981) .
E. Encapsulated Onion Flavors
Onion oil encapsulated by spray drying in gum acacia or
a starch is produced to be used as a flavoring ingredient.
For example, onion puree' is mixed with dextrin and dried at
65-68 degrees C for 4 min. This product is 20% stronger than
the onion powder
(Heath, 1981) .
F. Onion Oil
It is a brownish yellow mobile liquid, obtained by the
distillation of crushed fresh onions or from expressed juice.
It is used exclusively in flavors, in the canning industry,
for soups, meat, table sauces and dressings.(Arctander, 1960)
G. Onion Juice/Extract
(Oleoresin)
Onion juice has the flavor and the potential to be a
5
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base for an onion flavoring. It is obtained by multiple
hydraulic pressing of washed onions. Usually, the juice is
heated at 140-160 degrees Celsius and immediately cooled to
40 degrees. This way it is preserved until sufficient amount
of concetrated juice is collected for further concentration
in a vacuum falling film evaporator, to obtain a product with
75% dry solids. The concentrated juice has a pale-brown
color, strong fresh onion odor, and it can be further
evaporated in a vacuum stirrer-pan to have 80-85% solids
content. This extract has dark brown color and cooked/toasted
onion character. For.better handling the extract can be mixed
with propylene glycol, lecithin and glucose to give a stable,
semifluid onion oleoresin which has ten times a stronger
flavor than the onion powder
(Heath, 1981) .
The oleoresin contains the essential oil and also
certain non-volatile aromatic flavorings, plant colors and
glycosides, it is a product with richness and "body", and is
highly appreciated in the canning industry for pickles,
seasonings, meat sauces, etc. Moreover, the high calorie
value of onions
88% water)
(50 calories per 100 gr. of onions containing
promotes the onion extract in the place of the
vegetable itself (Artctander, 1960).
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II.
Onion Composition
The general onion composition appears in the
following table:
Table
1
Onion Composition
a
Moisture
b
Dry Basis
Wet Basis
%
%
4.0
89.1
Protein
7.7-12.0
1.5
Fat
0.9-1.6
0.1
75.9-82.1
8.7
4.3
0.6
3.1-4.0
0.6
Carbohydrates
Fiber
Ash
a
Gilroy Foods, Inc Lab results, 1987.
b
B. K. Watt and A. L. Merrill, 1963.
A. Onion Oil
The analysis of the onion oil,
(Heath, 1981)
shows it to
have the following compounds:
methyl-l-propyldisulfide
di-l-propyl trisulfide
methy1-1-propyl trisulfide
3,4 dimethyl thiophene
cis methyl-l-propenyl disulfide
trans methyl-l-propenyl disulfide
cis-l-propyl propenyl disulfide
7
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In contrast with the garlic oil, the onion oil contains no
allyl compounds.
More compounds are reported being present in the onion
oil such as hydrogen sulfide,
isopropyl alcohol, methyl
trisulfide, n-propyl mercaptan, propionaldehyde, methyl ethyl
ketone, ethyl alcohol, n-butyraldehyde, acetone, n-propyl
alcohol
(Heath, 1981).
B. Onion Carbohydrates
The content and the quantity of the reducing sugars in
onions depends on the variety and the storage conditions. The
bulbs contain sucrose, glucose, fructose, fructosan and some
times starch. The total carbohydrates are 79.1% of which
64.23% are soluble sugars. From the soluble sugars, the
reducing sugars are 11.34% and the non reducing sugars
52.89%. Also there are about 4.45% pectic substances, 1.88%
hemicellulose, 1.4% furfural and 27.0% polysaccharides
(Gilroy Foods, Inc Lab, 1987).
C. Protein
The amino acids present in the onion bulbs
arginine (256), lysine (63), phenylalanine
valine
(30) , isoleucine
methionine
(mg/100g)
(38), leucine (37)
(20), threonine (20) , tryptophan
(16) and histidine (14),
are
(20)
(Considine, 1982).
More detailed information about the onion composition is
presented in Tables 2 and 3. Dry basis values are
8
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taken from Gilroy Foods, Inc Lab, 1987 and the wet basis
values from B.K. Watt and A.L. Merrill, 1963.
Table
2
Onion Mineral Composition
Dry Basis
Wet Basis
mg%
mg%
Calcium
238.0
27 .0
Phosphorous
301.0
36 .0
4.4
0.5
94.0
10 .0
Potassium
1085.0
157 .0
Magnesium
108 .0
Iron
Sodium
*
Manganese
0.65
*
Copper
0.56
*
Zinc
4.6
*
<1.0
*
350 .0
*
Sulfur
307 .0
*
Iodine
0 .7
*
Barium
0.7
*
Strontium
1.2
*
Boron
0.9
*
<0.4
*
Aluminum
Chlorides
(as NaCL)
Chromium
not available values.
9
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Table
3
S
Onion Vitamin Composition
Dry Basis
mg%
Niacin
Ascorbic Acid
1.1
33.0
Wet Basis
mg%
0.2
10.0
Pantothenic Acid
0.74
*
Riboflavin
0.14
0.04
Thiamine
0.24
0.03
Inositol
700.0
*
Vitamin A
117 IU
*
40 IU
not available values.
10
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III. The Lacrimatory Factor
Fresh uncut onions have little odor. Cutting an onion
bulb releases a number of volatile organic molecules that
containe sulfur. These dissolve in the small quantities of
water present in the eye and produce sulfuric acid which acts
as an irritant and produces tears
(Maugh, 1979).
The onion odor is due to thiosulfinates
(RSSOR)
which change to disulfides:
R-S-SO-R + R-S-SO-R
— >
The major reaction
R-S-SO -R
2
involves
+ R-S-S-R
(Heathf 1981)
is:
H
I
I
s
/
C-H
||
C
C-H
s=o
\
allinase
C-H
I 2
CH-COOH
I
NH
+ water
/
>
C-H
||
CH -C-H
+ CH-CO-COOH + NH
3
3
Pyruvate
Ammonia
T r a n s (+)S-(1-propenyl)Lcysteine sulfoxide
(lacrimatory precursor)
\ /
hydrogen sulfide R-S-H
disulfides
R-S-S-R
thiosulfinates
R-SO-SR
thiosulfonates
R-SO-SR
polysulfides
R-(S)nR
dimethyl sulfide CH-S-CH
3
3
thiophenes
11
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Allinase, acting on the lacrimatory precursor, produces
the onion smell, and is also responsible for a bitter after
taste and pink decoloration of the cut onions. The pyruvic
acid produced can be used to measure the aroma intensity
colorimetrically, knowing that the 95% of it is produced 6
minutes after the reaction started (Heath, 1981) .
The sulfur compounds can be recovered as oil of onion
by extraction, their type depend on the conditions of the
extraction.
Steam distillation gives propionaldehyde and dipropyl
disulfide. Freon gives the lacrimatory factor at its both syn
and anti forms. Pure ethyl alcohol gives the lacrimatory
precursor. The lacrimatory precursor is a structural isomer
of alliin (garlic) and is converted enzymatically into the
lacrimatory factor. The lacrimatory factor exists 95% in the
syn form (Maugh, 1979).
12
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Figure 1
Sulfur Compounds Extracted From Onions (Block, 1985)
H C___
Steam
3
C
--------- >
>C=0
100C
H
C
S
C
C H
H C / \ / \ / \ /
3
3
C
S
C
+
Propionaldehyde
H C
Freon
3
--------- >
0C
Dipropyl Disulfide
0C
H C____
3
C
/
>C=S+
+
H
H
>C=S+
\
O-
Syn Form
Anti Form
Lacrimatory Factor
0Ethanol
C
>
<0C
I
S+
H
I
C*— NH
/ \ /*\ / \
2
H C
C
C
COOH
3
Lacrimatory Precursor
By heating, the thiosulfinates disappear and the flavor
potential decreases.
13
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During postharvest storage, the flavor potential of
onions increases due to the action of gamma-glutamyl
transferase and/or substrate degradation by active oxygen
such as .OH, and *0 . On the other hand irradiated onions,
during storage, appear to be decreased in flavor potential
due to the enzyme inactivation (Schwimmer, 1981).
•
14
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CHAPTER
3
Objectives
There were three objectives. The primary objective was
to determine if a possible flavor and aroma improvement could
be obtained from a hydraulically pressed/microwave oven dried
onions in relation to fresh onions with respect to aroma
intensity.
The second objective was to determine if these same
onion samples had the same quality in comparison to both
hydraulically pressed/air dried onions and commercially
dehydrated onions (multi stage air drying)
with respect to
moisture, ash, fat and protein content.
The third objective was to determine if the
hydraulically pressed/microwave oven dried onions were
comparable with the other two types
of dried onions in
respect to stability, and if the three
processed onions had
the same sensory characteristics or were different
in a soup base food system compared
to fresh onions in the
same soup base food system.
'
’
,
*' 1 5'• j
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CHAPTER
4
Materials and Methods
I.
Primary Procedures
A. Water Removal by Hydraulic Pressure
Material:
Fresh market onions,
(var. White Keepers), having an
average solids content of 11.8%, grown in Parma-Idaho,were
used throughout these studies, including the commercially
dehydrated samples.
Equipment:
Carver Laboratory Press model B, with cylinder assembly
Kitchen Aid Multifunction Food Processor
Triple Beam Ohaus Ainsworth Balance
Aluminum Foil
Fabric, Sparkle Organza B F B 6 , 100% Nylon (FN 8516 EST
441N FC-35)
Procedure:
Described below is the established procedure to
partially dehydrate fresh onions, based on a preliminary
experiment presented in Appendix IA.
Approximately 380 g of onion bulbs were cleaned, flaked
via the food processor and transfered to the sparkle organza
holder. The sample was rolled in the holder and set in the
cylinder of the hydraulic press. Pressure was applied in
advance and then released to avoid the damage of the fabric
16
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due to the internal pressure of the water released from the
sample. When a hydraulic pressure of a 17,000 psi was
reached, there was a 5 minute hold period to allow additional
water to be extracted. The sample was separated into two
layers; this procedure was repeated. Each layer was placed
between paper towels to absorb water by contact under
pressure. The process was repeated by changing the wet
paper towels with dry ones. The process was finished when the
paper towels remained dry. The sample was weighed and left to
dry in the air and room temperature or was dried in a
microwave oven.
B. Pinal Water Removal By Microwave Heating
Material:
Same as Chapter 4, IA
Equipment:
Same as Chapter 4, IA
Plastic Wrap (Handi-Wrap II)
Microwave: General Electric Dual Wave Microwave System
Dispo Weigh Boat Polystyrene Dishes, No B2045-10
Before describing the established microwave processing
procedure for final water removal, it is necessary to
describe the preliminary experiments leading to it.
Small amounts of previously pressed onion samples (83.2%
weight loss) were weighed on plastic dishes. Each one was
placed individually in the microwave for different times and
then left to air dry. One dish was left as a control to be
17
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airdried. The results appear in the following table:
Table
4
Pressed Microwaved Air Dried Onion Samples
Wt(g)
Min
Wt(g)
Pressed
Sample
1
5.3
3.9
2
5.3
3
%Wt Loss
Wt(g)
%Wt Loss
%Wt Loss
b
b
26.4
1.55
60.3
70.8
3.7
30.2
1.45
60.8
72 6
5.3
3.2
39.6
1.35
57 .8
74.5
4
5 .3
2.6
50.9
1.20
46 .2
73.6
6
4.3
1.6
62.8
0.45
28.1
73.3
10
4.1
1.4
65.9
0.35
25.0
74.4
30
4.3
changed to undesirable !
b rown
R*
4.3
———
65.1
65.1
a
a
1.50
c
a. Sample after microwave heat treatment
b. Same sample as a, after air drying
c. Total %wt loss from pressed sample after microwave heat
treatment and air drying
R* Pressed sample after air drying only
Calculations-examples as in Appendix IB
From the above samples only the one treated for 30
minutes changed color. The values of the table 5 indicated
that prehaps a microwave treatment of 10 minutes would be a
suitable time. However, when 61 g pressed onions from a 365 g
fresh onion sample (wt loss 83.3%)
was placed in the
microwave, the entire sample was burned before 7 minutes of
•
-
" V .
'
1 8
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microwave processing. Knowing that the physical geometry of
the sample could not be modified, it was decided to treat the
next pressed onion samples as follows:
The pressed
in the microwave
sample was weighed on plastic wrap, placed
for 30 seconds, removed and allowed to cool
for 60 seconds. It was placed again in the microwave, for 30
seconds, removed and allowed to cool for 60 seconds. The
process was repeated 14 times, until the samples accumulated
a total microwave processing time of 7 minutes. No color
changes were observed.
II. Proximate Analysis
The purpose
was to determine the moisture, ash, crude
fatand protein content
of fresh, commercially dehydrated,
pressed-air dried and pressed-microwaved flaked onions.
A.
Moisture Determination
Equipment:
Fisher Isotemp Vacuum Oven Model 281
Desiccator
Ainsworth type 10V Analytical Balance
Aluminum Weighing Dishes
Tongs
Procedure:
The oven was preheated and purged. Twelve aluminum
dishes were preheated at 100 degrees C for 1 hour, cooled in
•f;
'I*
v
.
-
19I
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desiccator and weighed. About 2 g of a well mixed
representative sample was weighed in each dish. The samples
were placed in the vacuum oven for six hours at 22mm Hg and
100 degrees C. Later, they removed from the oven, cooled in
desiccator, and weighed by handling them with tongs
(AOAC,
1978).
B. Ash Determination
Equipment:
Fisher Isotemp Vacuum Oven Model 281
Fisher Isotemp Muffle Furnace Model 184A
Ainsworth type
Analytical Balance
Porcelain Ashing Crucibles with Lids
Desiccator
Tongs
Procedure:
Twelve porcelain crucibles with their lids were
preheated in the muffle furnace at 550-600 degrees C, cooled
in desiccator and
weighed. About 2g of predried (for 1hour
in the vacuum oven)
sample was weighed
on each crucible. The
samples were placed in cool muffle furnace and heated
following this program:
a.
3h at 300
degrees C
b.
2h at 400
degrees C
c.
lh at 500
degrees C
d. overnight at 550-600 degrees C
e. cool down
to 100-120 degrees C for 24h
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
The samples were cooled in desiccator and weighed (Osborne
and Yoogt, 1978).
C. Crude Fat Determination
Equipment:
Fisher Isotemp vacuum Oven Model 281
Fiber Extraction Tubes
Boiling Flasks (250 ml round-bottom)
Condenser
(with 45/50 tapered jont to fit Soxhlet
extractor)
Heating Mantle and Rheostat for control of live voltage
Fatless Filter Paper
Solvent: Hexane
Procedure:
About lg of predried (for lh in vacuum oven)
onion
sample, was placed on fatless filter paper, folded and placed
in thimbles. Almost 150 ml hexane was placed in each of 12
flasks. The mantle, flask, extraction apparatus and condenser
were assembled to create a Soxhlet extractor. The hexane was
boiled for 90 minutes. The thimbles were removed and dried in
the vacuum oven for 30 minutes at 100 degrees C. The samples
were cooled and weighed
(Osborne and Yoogt, 1978) .
D. Protein Determination
Equipment:
Fisher Isotemp Vacuum Oven Model 281
Digestion Tubes
Receiver Flasks
, .
...
•
: -■ ;
21
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Heat Resistant Gloves
Digestion Unit
Distillation Unit
Catalyst: Kjeltab
Reagents: Boric Acid (saturated, with indicator for
Kjeldahl nitrogen determinations)
Sulfuric Acid, Technical
(93%)
Sodium Hydroxide, 40%
Hydrochloric Acid, 0.0465 N
Procedure:
The onion samples were predried in a vacuum oven for lh
About lg of each sample was weighed and each placed in a
digestion tube. One Kjeltab was added. Ten ml of sulfuric
acid was added to each tube, mixed and placed into preheated
(100 degrees C) digester. After 3 hours of digestion, when
solution was clear pale yellow, the samples were allowed to
cool.
Fifteen ml distilled water was added, mixed with the
solution and allowed to cool. Later, 25ml boric acid was
measured in receiver flasks; 10ml sodium hydroxide into each
digestion tube, and placed in distilling unit for 3 minutes.
After distillation, samples were titrated with hydrochloric
acid to neutral gray. Blank determination was run for
possible presence of nitrogen in the distilled water
(Osborne and Yoogt, 1978).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
III. Water Activity
Due to the fact that water activity (aw) is the latest
modern method for determining the shelf life of a product
and also can indicate the types of suitable packaging
, it
was considered important to conduct the following experiment.
Equipment:
Fa bri c, Sparkle Organza B F b 6 , 100% Nylon (FN 8516 EST
441N FC-35
Bethlehem Dri-Jar
S o d i u m Bromide, J.T. Baker Chemical Co.,Phillipsburg,
NJ.
Procedure:
One hundred grams of sodium bromide and 50ml water were
placed in the bottom of the water activity jar and were mixed
to a slurry. Ten grams of each onion sample were transfered
to a nylon fabric holder. The three holders were placed on
the jar divider, one upon the other, leaving space between.
The jar was hermetically sealed. After one week, the
position of the nylon holders rearanged as shown below:
From
A
to
B
C
C
B
to
A
At the end of the second week, moisture was determined.
23
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
IV
Sensory Evaluation
For this part the IFT Sensory Guideline was followed
(IFT, 1981) .
The purpose of this evaluation was to determine if the
three dried onion samples, processed with three different
procedures were of the same quality and similar to or
different from the fresh onions.
The evaluation was undertaken with both a trained panel
and a consumer panel. The objective of the trained panel
evaluation was primaraly to investigate the aroma quality of
the three dried onion samples in comparison with the fresh
onions, and secondly to determine the variation of specified
characteristics, such as color, texture and flavor. The
objective of the untrained or consumer panel was to measure
the likeness or dislikeness of the three onion samples in a
soup base, and also to test if these samples can be
discriminated from the fresh onions in the same soup base.
I.
Experimental Methods
The dehydrated onion samples were processed at Gilroy
Foods, Inc as described in p. 4 and at Chapman College as
described in p.16-17 and 19.
To provide the necessary information about the
qualification of the panelists, before any evaluation test
the potential panelists answered the questionnaire as found
in the Appendix III A.
24
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I. A
Sensory Test Methods
1) Trained Panel
After answering the above, the trained panelists were
asked to participate in an analytical descriptive flavor
profile test. The first investigation was to determine the
effect, if any, of storage on these dried onion samples.
The commercially dried onion sample was received in November
1986, having been processed in October 1986. The laboratory
hydraulically pressed onion air dried and microwaved samples
were prepared from November 1986 through February 1987. The
six panelists were asked to report any aroma unfamiliar with
the fresh onion one, and to determine if the products were
free from any objectinable odors of any kind. The coded
samples for the aroma profile, test #2, are as follows and
the score sheet is found in Appendix III B:
312 commercially dried
563 pressed air dried
478 pressed microwave dried
Later the same day, the panelists were asked to rank the
three dried onion samples according to specified
characteristics, to determine if there was any difference
among the samples in relation to the fresh onions. The
evaluation included color, aroma intensity, particle size and
shape, off aroma, texture, arid overall appearance.
For the analytical discriminative ranking test, test #3,
the samples were marked as follows and the score sheet is
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
found in Appendix III C:
723 commercially dried
591 pressed air dried
286 pressed microwave dried
To verify the results of the ranking test and also to
have a clear comparison of the three samples and the fresh
onions at their most important characteristics for this
research, the discriptive intensity scaling test #4 was made.
The samples were coded as follows and the score sheet is
found in Appendix III D.
582 commercially dried
756 pressed air dried
431 pressed microwave drid
R
fresh onion
2) Untrained Panel
One week later a consumer panel test was conducted the
affective hedonic scaling preference test #5, in which
consumers were asked to indicate how much they liked or
disliked dried onion samples in an onion soup base. One of
the test soup samples was made from fresh onions, to serve as
a reference in case that the four samples had significant
differences between them. The four samples were as follows
and the score sheet is found in Appendix III E.
762 pressed microwave dried
593 fresh onion sample
415 commercially dried
128 pressed air dried
26
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
I . B Panel
All panelists participated in the trained panel were
food flavor chemists, working at Globe West Extracts -Los
Angeles, in the Research laboratory for more than one year.
There were three males and three females, having ages between
23-50 years. They came from the followig countries: India,
Pakistan, Philipines, United States and Taiwan.
The consumer panel consisted of 26 panelists of
which 65% were Americans, 12% Asians, 3% Filipino, 3%
English, 3% Korean, 3% Japanese, and 11% Hispanic. There were
58% females and 42% males, from which 54% were between ages
23-35, 27% between 35-50, 11% were 50 and more, and 8% under
the age of 22. About 58% of the panelists were single and 42%
were married.
I. C Environmental Conditions
1. Test Location
The trained panel's sensory evaluation tests occured in
Globe West Extracts Laboratory, Los Angeles. The consumer
panel's test took place in the Sensory Evaluation Laboratory
at Chapman College, Orange, where the panelists conducted
their evaluation in individual booths under room day light.
2. Test Material
It consisted of dehydrated white onions, variety White
Keepers, produced in Parma-Idaho, processed as described
previously.
All samples were kept in plastic containers until the
27
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moment of evaluation.
Test #2 was conducted by placing 3g of each sample in
its dried flaked form in polyester container, served on a
dish. The samples for test #3 were prepared by putting lg of
dried onion flakes in a beaker having 20ml hot water. Also 8g
of fresh cut onions were placed in another beaker. After
reconstitution, the samples were served (covered)
at room
temperature. The test #4 had lg of dry onion sample in
powdered form reconstituted in 10ml water. The sample named R
was 8g fresh onion puree'. The test #5 consisted of dried
onions in a soup base. The recipe used was the following:
2 ozs reduced calorie Weight Watchers margarine
5 g salt
24 ozs grade A Knudsen milk
40 g all purposes Pillsbury's flour
17.5 g dried onions rehydrated in 4 oz water or for the
fresh onion sample 137g flakes.
The margarine was melted, the flour and salt was
a d d e d > stirred, cold milk and onions were added at once, and
the mixure was heated until boiled.
3. Test procedure
a) Coding
All samples were coded with three digit random numbers.
The test #5 had random balanced order.
b) Serving Amount
The serving amount of the onion soup samples was one oz
28
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served in two ozs Anchor Hocking plastic transparent cups.
c)
Special Considerations
Two Sunshine unsalted crackers, and a cup of water at
room temperature were served parallel with the onion soup
samples.
29
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CHAPTER
5
Experimental
Data
Results
and
Discussion
The application of hydraulic pressure to fresh flaked
onions not only removed the water, but also water soluble
constituents and essential oils. Therefor weight loss
represented the changes due to pressure in water removal.
Weight loss data are found in Table 5
Table 5
Onion Weight Loss After Pressing and Air Drying
Wt (g)
sample
Wt(g)
a
%Wt Loss
a
Wt(g)
b
%Wt Loss
b
%Total Wt Loss
c
560
35
93.8
21.1
39.7
96.2
200
18
94.0
8.0
44.4
96.0
301
21
93.0
13.5
35.7
95.5
583
50
91.4
33.4
33.2
94.3
382
24
93.7
15.0
37 .5
96 .1
A v = 9 3 .2%
Av=3 8 .1%
Av=95
a. Samples after pressing
b. Same samples as a after air drying
c. Samples after pressing and air drying
Calculations same as in Appendix IB
The hydraulic pressing procedure showed that the most
desirable amount of onion sample for this particular
operation was between 200-400g. Larger amounts of flaked
onion increased the time and the inconvenience of the
pressing operations.
30
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The desired applied pressure was found to be 17,000psi.
It was observed that pressures greater than 17,000psi
resulted in the actual onion mass passing through the nylon
fabric (holder).
The following results were obtained from the established
microwave drying procedure:
Table 6
a
Fresh Pressed Onions Dried by Microwave Energy
Wt (g) Wt (g) %Wt Loss Wt (g) %Wt Loss Wt(g)
c
c
d
b
Sample b
%Wt Loss %Wt Total
d
e
300
46
84.7
25
45.7
17
32.0
380
50
86.8
30
40.0
21
30.0
94.5
400
51
87.3
32
37 .3
20
37 .5
95.0
350
44
87.4
25
43 .2
18
28.0
94.9
A v = 3 1 .9%
A v = 9 4 .7%
A v = 8 6 .6%
A v = 4 1 .6%
94.3
Accumulated energy eguivelent to 7 minutes
b. Samples after pressing
c. Same samples as b after microwaving
d. Same samples as c after air drying
e. Samples after pressing, microwaving and air drying
Calculations same as in Appendix IB
The time needed to air dry the microwave dried
samples was a maximum of 2 hours. The samples were not
processed by microwave for longer times, because the
generation of heat is continuous and there is a continuous
rise of temperature of the onion samples. The longer the
microwaves are applied the higher the temperature. When the
.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
■
,
sample is wet, microwaves raise the temperature to 100
degrees C, and the continued generation of heat boils off
free water (Sale, 1976) . With the free water gone, the
temperature of the "nearly dry" onion sample can rise rapidly
with the risk of scorching and burning it. The risk of
burning was greater with the fresh pressed onion samples
where the water was not equally removed from each flake.
During heating, a color change in the onion samples
occured, due to the reaction between proteins-carbohydrates
and/or fat-carbohydrates. The fresh onion samples had the
darkest color of all samples, the commercial had ununiform
dark colored particles, while the pressed samples had lighter
color, because during pressing the soluble carbohydrates were
removed partially with the onion juice, and the reactions
were at a slower rate.
Table 7 shows the results of the moisture determinations:
32
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Table 7
Moisture Determination of Onions
Fresh
Wt(g)
Sample
Wt(g) Dry Sample
Moisture %
1
2.3705
0.3052
87 .1
2
2.0229
0.2637
87 .0
3
1.9053
0.2399
4
1.7953
1.6483
8 .2
5
1.6245
1.4753
9.2
6
2.0077
1.8021
7
1.5822
1.4551
8.0
8
2.0739
1.9280
7 .0
9
1.4390
1.3120
8.8
A v = 7 .9%
10
1.8026
1.6803
6.8
11
1.7612
1.6436
6.7
12-
1.8111
1.6688
7.9
A v = 7 .1%
87 .4
A v = 8 7 .2%
Commercial
10 .2
A v = 9 .2%
Air dried
Microwaved
Calculations-examples as in Appendix IIA
All dried samples had higher moisture content than 4%
which is indicated in Table 1. The storage conditions
increased the moisture content of the dried onion samples.
The accurate determination of moisture content is
complicated by a number of factors as the level of moisture
in the sample, the ease with which that moisture can be
removed, the possible weight loss through thermal
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
decomposition or a possible gain weight due to oxidation, the
rheology of the sample, and the possible loss of volatiles
other than water from the sample (Osborn and Yoogt, 1978).
The ash determinations are in the following table:
Table 8
Ash
Determination
of
Onions
% Ash
Dry Basis
% Ash
Wet Basis
Fresh
Wt(g)
Sample
Wt(g)
Dry Sample
1
2.0768
0 .0874
4 .2
0 .5
2
1.6246
0.0607
3.7
0 .5
3
2.3975
0.0969
4.0
0.5
Av=4 .0%
Av=0 .5%
Commercial
4
1.9958
0.0926
4.6
0.6
5
2.3800
0.0956
4.0
0.5
6
1.7553
0.0668
3.8
0.5
Av=4 .1%
A v = 0 .5%
Air dried
7
1.3983
0.0403
2.9
0.4
8
2.0128
0.0641
3 .2
0.4
9
1.5124
0.0472
3.1
0.4
A v = 3 .1%
A v = 0 .4%
Microwaved
10
1.5200
0.0493
3.2
0.4
11
1.5487
0.0478
3.1
0.4
12
1.9391
0.0634
3.3
0.4
A v = 3 .2%
A v = 0 .4%
Calculations-example as in Appendix IIB
34
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When the samples are heated to 500-600 degrees C, the
water and other volatile compounds escape as vapors, the
organic matter is burned in the presence of oxygen to CO
2
and oxides of nitrogen, and also eliminated with hydrogen as
water.
The results of the ash determination were in the range
of 4% dry basis and 0.5% wet basis. However, the pressed
samples had less ash content, 3.1% dry basis and 0.4% wet
basis, as a result of the juice removal, which contained a
portion of the minerals.
The following table portrays the results of the Soxhlet
extractions:
35
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Table 9
Crude
Pat
Determination
of Onions
Fresh
Wt(g)
Sample
Wt(g)
Fatless sample
% Fat
Dry Basis
1
0.9685
0.9525
1.7
0 .2
2
0 .9774
0 .9604
1.7
0 .2
3
0 .9929
0 .9769
1 .6
0 .2
% Fat
Wet Basis
Av=l .7%
A v = 0 .2%
Commercial
4
1.0190
1.0030
1.6
0 .2
5
1.0162
0.9982
1.8
0 .2
6
0.9645
0.9472
1.8
0 .2
A v = l .7%
Av=0 .2%
Air dried
7
0.9666
0 .9294
3.8
0 .5
8
0 .9906
0.9517
3.9
0 .5
9
1.0160
0.9851
3.0
0.4
Av=3 .6%
A v = 0 .5%
Microwave
10
0.9686
0.9387
3.1
0 .4
11
0 .9824
0.9544
2.9
0 .4
12
0.9568
0.9312
2.7
0.3
A v = 2 .9%
Av=0.4%
Calculations-example as in Appendix IIC
The Soxhlet apparatus permits the passage of the
solvent's vapors into the condenser, where they are
liquified, and in turn contacting the sample and extracting
the fat. The values in Table 9 indicate that the pressed-air
'.-iv.*.
‘■’7 ■
-v-i
36::
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
dried and the pressed-microwaved samples have increased fat
values. That is partially because the other two samples were
processed by heat and the volatile oil was vaporized at the
higher temperatures. However, the Soxhlet extraction is an
approximate technique, because it is not known when the
extraction is completed. It has the advantage that the sample
extracted at low temperatures is in complete contact with the
solvent, while it has the disadvantage that if water exists
in the dried sample, it can be incorporated into the lipid
material.
The protein determination was made by using the microKjeldahl method, which is based on the determination of
reduced nitrogen species like -NH , =NH after sulfuric acid
2
digestion and liberation of NH . When the sample is subjected
3
to wet oxidation, the protein nitrogen is converted to
SO (NH ) , which is decomposed with NaOH and NH is distilled
4
4 2
3
into saturated boric acid solution and titrated with HC1.
The use of the micro-Kjeldahl method provides the
protein results found in Table 10:
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Table 10
Crude
Protein
Determination of Onions
Wt(g)
ml HC1 Dry Basis Dry Basis Wet Basis Wet Basis
Fresh Sample 0.0465 N
N%
Protein
N%
Protein
1
1.0402
20.1
1.3
7.9
0.16-0.2
1.25
2
1.0459
19.3
1.2
7.5
0.15-0.2
1.25
3
1.0077
21.2
1.4
8.6
0.18-0.2
1.25
A v = 8 .0%
A v = l .25%
Commercial
4
1.0358
23.0
1.4
9.0
0.19-0.2
1.25
5
1.0371
20.9
1.3
8.2
0.17-0.2
1.25
6
1.0330
21.7
1.4
8.6
0.18-0.2
1.25
A v = 8 .6%
A v = l .25%
Air dried
7
1.0215
20 .8
1.3
8 .1
0.17-0 .2
1.25
8
1.0369
19.9
1.3
8.1
0.16-0.2
1.25
9
1.0486
20 .7
1.3
8.1
0.17-0.2
1.25
A v = l .25%
A v = 8 .1%
Microwaved
i
I ta
1H
J
1
1.0385
19.7
1.2
7.5
0.16-0.2
1 .25
11
1.0152
20.2
1.3
7.8
0.17-0 .2
1.25
12
0.9950
21.5
1.4
8.8
0.18-0.2
1.25
A v = 8 .1%
Av=l .25%
Blank determination gave 0 nitrogen value.
Calculations-example as in Appendix IID
«*•
Table 10 demonstrates that there is no variance in the
protein
> i
values among the four samples, and that the numbers
are in agreement with the values in Table 1. Also, it was
*■..,?/ •
; - . ;.:V .,
38
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observed that the changes in fat and protein were not
significant for samples treated by microwave energy. It is
known that microwaves are a low energy form and might act as
a catalytic agent (Lorenz, 1976).
The variation between the various experimental results
and the literature can be due to the fact that the literature
does not indicate the exact type of onion used or the time of
year that the determinations took place. It is known that the
same plant has a different composition at different times of
the year.
During the water activity experiment, the temperature of
the environment was 24 degrees C, indicating that the samples
in the closed jar, after fifteen days, had about 57.5% water
activity (Rockland and Nishi, 1980).
The moisture determinations of the dried onion samples
having an aw about 57.5%, gave the results appearing in the
following Table 11:
■ v
r , . /...
V ' ;-
39
‘
v--
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Table 11
Moisture Content of Dried Onion Samples Having
0.575 Water Activity
Wt (g)
Sample
Wt (g)
Dry sample
1
1.9076
1.5885
16.73
2
2.0299
1.7434
14.10
3
2.1760
1.8087
16 .88
Commercial
%
Moisture
A v = 1 5 .9%
Air Dried
4
1.9865
1.7534
11.73
5
1.4600
1.3024
10 .79
6
2.0343
1.7755
12.72
A v = l l .8%
Microwave
7
1.7625
1.5561
11.71
8
2.0287
1.7740
12.55
9
1.7931
1.5867
11.51
A v = l l .9%
Calculations as in Appendix II A
The results of Table 11 are pictured in Figure 2:
40
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Figure
2
Moisture Content of Dried Onion Samples Adjusted to
a Water Activity of 0.575
/ 1\
1
16
%
15
m
o
i
s
t
u
r
e
14
13
12
11
10
1
1
1
|
1
|
1
1
1
|
1
|
1
1
j
|
1
I
1
commercial
1
1
1
|_microwave
|-air dried
1
1
I
1
I.............................. I............
aw
0.575
>
Figure 2 shows that at aw=57.5%, the three dry onion
samples had different moisture contents. When closed in the
jar, the commercial samples absorbed larger amounts of
moisture than the pressed samples. The pressed samples had
lower moisture content probably because their combining
activity was decreased due to their lower solids content, and
particularly lower sugar content. Also, due to high pressure
application the cells of these samples lost their structure
and some of the capillaries pores were destroyed. For these
reasons, the microwave dried and air dried samples appear to
be more stable than the commercial, which, during storage,
will have higher potential of browning reaction and higher
potential of oxidation (Rockland and Nishi, 1980).
,, , ....
... ....
, -
- xv
41
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The sensory evaluation panelists were informed from the
beginning that these tests concern a thesis project.
The aroma profile, gave
the
results appearing
in
Table 12.
Table 12
Aroma Profile Evaluation
Dried Onion Samples
Commercial
312
Off odors
1
Air Dried
Microwaved
563
478
9
7
Cooked aroma
6
3
5
Aged product odor
5
7
8
The results indicated that the commercially dried and
the microwaved were recognized as "cooked", and that
the pressed samples developed off aroma. All the
samples had
a partially aged product odor. The comments described that
the commercial sample had the most pleasant aroma resembling
the fresh onion aroma. Most of the panelists mentioned that
they did not like the pressed samples because of their strong
aroma.
The results obtained from ranking, test #3, were
different:
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Table 13
Color Ranking Scores
Dried Onion Samples
Commercial Air Dried Microwaved
Judges
723
591
286
1
1
2
3
1
3
2
2
4
2
1
5
3
2
1
6
2
2
1
13
9
Sum rank
1
1
2
2
1
8
Table 14
Aroma Intensity Ranking Scores
Dried Onion Samples
Commercial Air Dried Microwaved
Judges
723
591
286
1
1
2
3
2
2
1
3
3
3
4
1
5
3
6
1
Sum rank
11
1
3
2
1
2
2
1
2
H
12
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Table 15
Partical size and Shape Ranking Scores
Dried Onion Samples
Commercial Air Dried Microwaved
Judges
723
591
286
1
3
1
2
2
1
3
2
3
2
3
3
4
3
1
2
5
3
2
1
6
3
1
1
15
11
Sum rank
11
Table 16
Off Aroma Ranking Scores
Dried Onion Samples
Commercial Air Dried Microwaved
723
591
286
1
0
0
0
2
3
2
2
3
2
2
2
4
2
1
1
5
3
1
2
6
1
2
2
l
1H
1H
1
8
9
Judges
Sum rank
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Table 17
Aroma Closer to Fresh Ranking Scores
Dried Onion Samples
Commercial Air Dried Microwaved
723
591
286
1
1
2
3
2
3
1
2
3
3
3
3
4
3
2
1
5
3
1
2
6
1
2
2
11
13
Judges
Sum rank
14
Table 18
Texture Ranking Scores
Dried Onion Samples
Commercial Air Dried Microwaved
723
591
286
1
2-
1
2
2
2
1
3
3
3
3
2
4
3
2
1
5
1
2
3
6
2
1
2
10
13
Judges
Sum rank
13
45
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Table 19
Overall Appearance Ranking Score
Dried Onion Samples
Commercial Air Dried Microwaved
591
286
1
2
2
2
2
1
3
2
3
2
3
2
4
3
2
1
5
3
2
1
6
1
2
2
Sum rank
The Chart 5,
12
1
H 1
•0- 1
1
723
Judges
10
(Larmond, 1977), indicates that for three
samples and six judges the tabular entries are 8-16.The
lowest insignificant rank sum is 8 and the highest
insignificant rank sum is 16. None of the sum rank results of
the Tables 13, 14, 15, 16, 17, 18 and 19 is lower than 8 or
higher than 16 which indicates that there was no significant
differences among the samples at the 5% level.
..-..46
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
The intensity scaling Test #4, resulted in the
following:
Table 20
Aroma Intensity Scaling Scores
Onion Samples
Comm.
Air Dr
Micr.
Presh
582
756
431
R
1
3.80
0 .85
1.70
9 .70
16 .05
2
1.40
2 .25
0 .70
9.75
14.10
3
5.20
1.40
1.05
8.90
16.55
4
4.80
2.75
1.50
8 .30
17.35
5
1.10
3.20
1.70
9.20
15.20
6
5.95
4.70
3.40
8 .80
22.85
22.25
15.15
10 .05
54 .65
102 .1
Judges
Totals
Total
The statistical analysis of variance is given in Table
21:
Table 21
Aroma Intensity Scaling Analysis of Variance
Df
Ss
Ms
F
Samples
3
201.02
67.00
41.88
Judges
5
11.77
2.35
1.47
Error
15
24.09
1.60
Total
23
236.88
With three degrees of freedom in the numerator and 15
degrees of freedom in the denominator, the P value must
exceed 3.29 to be significant at the 5% level, Chart 3,
■ ■’ 1
„ 47
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
and 5.42 to be significant at 1% level (Larmond, 1977).
Table 21 shows that the samples are significantly different
at 1% level. Using the Tukey's test, for four treatments and
15 df for error, the value 4.08 ,obtained from Chart 4,
indicates that any two sample means differ by 2.12 or more
are significantly different at 5% level (Larmond, 1977).
Samples according to their aroma intensity:
R
582
756
431
9.1a
3.7b
2.5b
1.7b
Calculations as in Appendix III F
Table 22
Color Intensity Scaling Scores
Onion
Comm.
Samples
Air Dr.
Micro
582
756
1
7.60
5.05
6.40
2.10
21.15
2
1.90
3 .05
4.00
9.50
18.45
3
5.55
4.07
1.90
0 .65
12.80
4
7.40
6.15
4.85
2.70
21.10
5
3.00
2.65
7 .40
9.30
22.35
6
4.25
5.09
8.00
3.35
21.50
29.70
27 .50
32.55
27 .60
117 .35
Judges
Totals
431
Fresh
R
Totals
The analysis of variance for Table 22 is given in
Table 23:
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Table 23
Color Intensity Analysis of Variance
Df
Ss
Ms
Samples
3
2.81
0 .94
0 .12
Judges
5
15.85
3.17
0 .39
Error
15
120 .76
8.05
Total
23
139.42
F
Calculations as in Appendix III G
As described before, for three degrees of freedom in the
numerator and fifteen degrees of freedom in the denominator
the F value must exceed 3.29 to be significant difference at
5% level among the samples, and 5.42 for 1% level. Table 23
shows that the color intensity of the four samples is not
significantly different at 1% level:
582
756
431
4.95a
4.58a
5.40a
4 9 ...
R
4.60a
C H A P M A N C O L L E G E LIBRARY
n O R A N G E , CALIFORNIA
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Table
24
Off Aroma Intensity Scaling Scores
Onion
Commer.
Samples
Air Dr. Micro
Fresh
582
756
431
R
Totals
1
8.00
4 .60
2.90
0 .40
15.90
2
8.90
1.20
1.75
0 .40
12.25
3
6.95
4.40
2.80
0
14.15
4
3.20
4.85
6.55
0
14.60
5
1.00
8.20
6 .35
0 .25
15.80
6
6.75
5 .40
3 .10
8 .5
23.75
34.80
28.65
23 .45
9 .55
96.45
Judges
Totals
The analysis of variance of Table 24 appears in Table 25:
Table
25
Off Aroma Intensity Analysis of Variance
Df
Ss
Ms
F
Samples
3
57.89
19.29
2 .23
Judges
5
19.89
3.98
0 .46
Error
15
129.58
8.64
Total
23
207.36
Calculations as in Appendix III H
As previously described the F value must exceed 3.29 to
have significant difference at 5% level and 5.42 to have
significant difference at 1% level. The samples do not differ
significantly at 1% level:
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
582
756
431
R
5.8a
4.8a
3.9a
1.6a
The intensity scaling test showed that the three dried
samples do not differ one from another, but all differ from
the fresh onions as far as the aroma intensity concerns.
All samples have the same color intensity, at 99% confidence
level. Also, the four samples do not differ according to
their off aroma intensity, and due to the fact that fresh cut
onions was one of the samples, it can be concluded that the
dried samples did not have off aroma.
The Chart 3 (Larmond, 1977)
indicates that for six
judges and fifteen degrees of freedom in the denominator the
judges can be significant different at 5% level if the F
value exceeds the value of 2.79 and significant at 1% level
if it exceeds 4.32. The analysis of variance Tables 21, 23
and 25 show that there is no significant difference between
the judges at 5% or 1% level.
The consumers scored as following:
Table
26
Hedonic Scaling Evaluation Scores
Onion
Fresh
Judges
Samples
Micro Air Dr.
Comm.
593
762
128
415
Totals
1
7
8
7
9
31
2
8
3
6
7
24
" (Continued ) m
,
.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
"(Table 26, continued)"
3
6
4
4
7
21
4
8
5
4
7
24
5
7
6
9
3
25
6
9
7
8
8
32
7
8
7
4
6
25
8
7
6
5
4
22
9
8
8
4
5
25
10
5
6
7
6
24
11
6
7
4
5
22
12
5
6
4
3
18
13
9
7
3
5
24
14
7
3
2
8
20
15
9
1
8
8
26
16
5
4
4
4
17
17
5
4
7
6
22
18
4
5
6
8
23
19
4
3
7
8
22
20
9
7
3
5
24
21
4
6
5
4
19
22
6
4
3
4
17
23
4
8
4
7
23
24
3
5
4
7
19
25
. 5
5
5
6
21
26
5
6
8
3
22
Totals
163
141
135
153
592
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
The
statistical analysis of variance gave the results
shown in Table 27:
Table 27
Hedonic Scaling Analysis of Variance
Df
Samples
Ss
Ms
F
3
17.99
5.99
1.76
Judges
25
80.15
3.21
0.94
Error
75
256.01
3.41
Total
103
354.15
Calculations
as in Appendix III J
For three degrees of freedom in the numerator and 75
degrees of freedom in the denominator,
(Charts 3 and
4)the
value must exceed 2.76 to be significant at 5% level
and4.13
to be significant at 1% level (Larmond, 1977). Table
27
F
indicates that the four onion soup samples were not
significatly different at 1% level:
593
6.27a
762
5.42a
128
415
5.19a
5.88a
The same Charts show that the judges to be significant
at 5% level the F value for judges must exceed 1.70, and 2.12
for 1% level. The judges having F value 0.94 were not
significantly different at 1% level.
53
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C HA PT ER
6
Summary/ Conclusions and Recommendations
With the wide spread use of dehydrated onions in the
food industry/ an attempt was made via hydraulic pressing and
microwave oven drying/ to produce an onion product with a
stronger aroma intensity than the commercially dehydrated
onions and as close to the aroma of the fresh onions as
possible.
The established microwave drying method gave a dried
onion product with protein and moisture content comparable
with the commercially dehydrated and hydraulically pressed
air dried onions. The fat content of the microwave dried
product was increased in comparison with the commercial and
the fresh onions. Due to greater heat treatment the volatile
oils escaped from the commercially dehydrated onions.
However/ the ash content of the hydraulically pressed onions
was decreased due to lower solids content.
The pressed microwave oven dried onion sample proved to
be potentially stable with less probability of brov?vif/yj^
reactions and oxidation during storage. This means it will
have longer shelf life in comparison with the commercially
dried onion sample.
The trained sensory evaluation panel showed that the
pressed microwave dried onion sample was comparable as far as
aroma and color intensity with the commercial onion and the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
pressed air dried samples, but not compatable with the fresh
onion sample. None of the samples developed off aroma from
the moment of production (either commercial or laboratory)
to
the moment of evaluation. The consumer evaluation indicated
that the four different onion samples could not be
distinguished when they were tasted in a soup base.
While flavor improvement was not obtained, the pressed
microwave dried onion product can be used in different ways
than the commercial product. Because a considerable portion
of the soluble solids escape with the expressed juice during
pressing, this onion product has fewer calories. It could,
therefor, be a component in a diet food product. Also, it can
be used in the powder form. As a powder it can be used on
products which require heat and not a burnt onion color.
The expressed juice can be collected, concentrated and
used to produce onion essence, onion extract, oleoresin or
onion oil. Also, onion essence can be sprayed on the onion
powder or onion flakes to potentiate the onion aroma and
flavor.
Further investigation is recommended on the sensory and
compositional value of the expressed onion juice.
55
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References
AOAC, 1984. "Official Methods of Analysis", 14th, Williams,
S., Published by the Association of Official Analytical
Chemists,I n c ., Arlington, Virginia, p.152.
Arctander, S. 1960. "Perfume and Flavor Material of Natural
Origin". Arctander, E., N.J., U.S.A., pp.468-469.
Block, E. 1985. Chemistry of garlic and onions. Scientific
American, 252(3): 114.
Considine, M.D. 1982. "Foods and Food Production
Encyclopedia". Considine, D., Nan Nostrand Reinhold
Company, New York, p.1378.
Gilroy Foods, Inc., 1987. Laboratory results.
Heath, B. 1981. "Source Book of Flavors". Avi Publishing
Company Inc., Westport, Connecticut, pp.99-101, 153-155.
I F T . 1981. Guidelines for the preparation and review of
papers reporting sensory evaluation data. Sensory
Evaluation Division, Institute of Food Technologists. Food
Technology. 35(4):16.
Labuza, T.P. 1976. Drying food: technology improves on the
sun. Food Technology, 30(6): 37.
Larmond, E. 1977. "Laboratory Methods for Sensory Evaluation
of Food", Publication
1637, Research Branch, Canada
Department of Agriculture, Ottawa, Ontario, pp.65-68.
Lorenz, K. 1976. Microwave heating of foods-changes in
nutrient and chemical composition. CRC critical reviews in
food science and nutrition, 7(4):339.
'
'• ■
■-
56
' 'f- •
Reproduced with permission o f the copyright owner. Further reproduction prohibited without permission.
■' ‘i -
Luh, S.B. and
Woodroof, J.G. 1978. "Commercial Vegetable
Processing", 3rd ed., Avi Publishing Company Inc.,
Westport, Connecticut, pp.397-401.
Maugh, T.H. 1979. Its nothing to cry about. Science
204(4390): 293.
Osborne, D.R. and
Yoogt, P. 1978. "The Analysis of Nutrients
in Foods", Academic Press, N.Y.,New York, pp.113-116, 155156, 166-167.
Rockland, L.B. and
Nishi, S.K., 1980. Influence of water
activity on food product quality and stability. Food
Technology, 34(4): 42.
Sale, A.J.H. 1976. A review of microwaves for food
processing. J. Fd Technol, 11: 319.
Schwimmer, S. 1981. "Source Book of Food Enzymology", the Avi
Publishing Co, Inc., Westport, Connecticut, p.378.
Watt, B.K. and Merrill, A.L. 1963. "Composition of Foods".
Agriculture Handbook No. 8, Consumer and Food Economics
Research Division Agricultural Research Service, United
States Department of Agriculture, p.41.
Yamaguchi, M. 1983. "World Vegetables, Principles Production
and Nutritive Values", Avi Publishing Company, Inc.,
Westport, Connecticut, p.192.
F7
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
APPENDIX
IA
Cellulose
Experiment
Cellulose was placed in a desiccator full of water.
After two days, the wet cellulose was weighed and placed in
the hydraulic press. Pressure of 24,000psi was applied. The
cellulose was weighed, placed in the cylinder, repressed and
reweighed. When after the sixth pressing no weight loss
appeared, the cellulose left to dry in the air.
The following table shows the weight loss after each
pressing of cellulose sample equal to 233.7g
Table 28
Cellulose Experimental Results
Pressing
From Previous Pressing
wt(g) Sample %Wt Loss
0
% Total Wt Loss From
Initial Sample
0
1
233.7
93 .8
93 .8
2
14.5
4.8
94.1
3
13.8
5.8
94.4
4
13 .0
2.3
94.5
5
12.7
3.9
94.7
6
12.5
0
94.7
a
11.9
4.8
94.9
a. Sample after 6th pressing left to air dry
Calculations-Example:
233.7-14.5=219.2 wt loss
(219.2/233.7)*100=93.8% wt loss from initial sample
.. ■ , ,
58
'•
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
The first pressing is the critical step, when the
largest amount of the water is removed.
Onions having 87-90% moisture content, can be pressed
as the cellulose.
I B
From Table 4:
5.3-3.9=1.4g weight lost after microwave drying
(1.4/5 .3)*100=26.4% weight loss
3.9-1.55=2.35g weight lost after the microwave dried
left for further drying in the air.
(2 .35/3.9)*100=60.3% wt loss
5.3-1.55=3.75g weight loss from initial pressed sample
after microwave drying and air drying.
(3.75/5.3)*100=70.8% total weight loss from initial
pressed sample.
59
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II A
Moisture:
% moisture={[sample wt(g)-dry sample wt(g)] / [sample
wt(g)]}*100
Example from Table 7:
1.
[(2.3705-0.3052)/2.3705]*100=87.1% moisture
II B
Ash:
a) % ash (DB)={[wt(g)
ash]/[wt(g)
dry sample]}*100
Example from Table 8:
1.
(0 .0874/2.0768)*100=4.2% ash dry basis
b) For % ash at wet basis worked as follow:
The experimental moisture is 87.2%. The dry part of the
sample for 100g it will be 12.8%. From the Table 9, the same
sample 1:
(2.0768/0.128)=16.225g is the fresh sample corresponding
to 2.0768g dry sample.
(0.0874/16.225)*100=0.5% ash wet basis
11 c
Crude Fat
a) % fat (DB)={[wt(g)
fat]/[wt(g)sample]}*100
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Example from Table
1.
9:
[(0.9685-0.9525)/0 .9685]*100=1.7% crude fat dry basis
b) For % fat wet basis worked as in II
B b)
(0.9685/0.128)=7.5664g fresh sample corresponding to
0.9685g dry sample.
[(0 .9685-0.9525)/ 7 .5664]=0.2% crude fat wet basis
II D
Protein:
a) % N (DB)={[ml HC1*N acid * 0 .01401)/[wt(g)
sample]}*100
Example from Table 10:
1.
[(20.1*0.0465*0.01401)/1.0402]*100=1.3% nitrogen (DB)
% protein
(DB)=1.3*6.25=7.9
b) For wet basis worked as previously:
1.0402/0.128=8.1266g fresh sample corresponding to
1.0402g dry sample.
[(20.1*0.0465*0.0140)/8.1266]*100=0.16~0.2% N wet basis
0.2*6.25=1.25% protein wet basis
61
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Ill A
Test #1
DEMOGRAPHIC QUESTIONNAIRE
To match your product preference, usage, and sensory
skills to the samples to be evaluated, please complete this
questionnaire. All information will be maintained
confidential.
Name_____________________
Female_________________
Male________________
Ethnical background__________________
Occupation__________________
Age 0—22_______
Single_______
23—35_________
35—50_____
50 or older_____
Married_______ Other______
Children 0____ 1_____ 2______ 3_____ 4 or_more_____
Please indicate, if any of the following foods disagree with
you (allergy, discomfort, dislike, etc.)
Onions,:
Onion soup______ Vegetable oil (any type)_____
Salt_____
Please indicate if you are on a special diet.
Diabetic_____ High calorie_____ Low calorie______ Low salt___
No special diet_____ Other_____
Do you have any physical or psychological disorders(s)
that
will limit or alter your sensory perception evaluation(s)?
Yes_____ No_____
If yes, please explain__________________________________________
62
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Are you willing to participate on a test panel concerning
onion soup?
Yes
No_____
As a normal consumer, how many times do you eat vegetable
soup?
0-1 times a month_____ 4-5 times a month_____
2-3 times a month_____ 6 or more times a month_____
Do you prefer vegetable soup than onion soup?
Yes
No
The same____
Why?__________________________________________________________
Thank you
63
*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Ill B
Test #2
Date: ____________
Name: ____________
AROMA
PROFILE
You have received three dried onion samples. Please
define the intensity of the following characteristics, if any
exists in the samples, using the descriptions threshold, 1,
2.
312
Off o
d
o
Cooked aroma
r
s
563
478
_______________________ „____________
____________________________________
Aged product o d o r _______________ ;
____________________
Comments:
Thank you
64
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Ill
c
Test #3
Date:________
N a m e :________
RANKING
TEST
You have received four onion samples. The sample marked
as F containes fresh onions. Please rank the other samples to
the following characteristics using the numbers 1,2,3, when
number 1 indicates the best sample.
723
591
Color
_____
_____
_____
Aroma intensity
_____
_____
_____
Partical size and shape__________________
_____
_____
Off aroma
_____
_____
_____
Aroma closer to fresh onions
_____
_____
_____
_
_____
_____
_____. _____
_____
Texture
286
Overall appearance closer to
fresh onions
Comments:
Thank you
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Ill D
Test
INTENSITY
#4
SCALING
N a m e :_
Date:
Please evaluate the four onion samples according to
their onion aroma intensity, their color intensity and their
off aroma. Make horizontal lines on the vertical line to
indicate your rating of the intensity of each sample. Label
each horizontal line with the code number of the sample it
represents. Please place them with the following order:
R, 582, 756, 431.
Onion Aroma
Intense
Color
Intense
None
None
Off Aroma
Intense
None
Comments:
Thank you
66
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Ill E
Test #5
HEDONIC SCALING PREFERENCE TEST
Date:__________
Name:_______________
Taste these samples at the following order
and check how much you like or dislike each one
Like extremely
Like very much
Like moderately
Like slightly
Neither like nor dislike
Dislike slightly
Dislike moderately
Dislike very much
Dislike extremely
Comments:
Thank You
67
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Ill
F
Aroma Intensity
From Table 20, statistical analysis of variance:
CF=102.1 ~2/(4*6)=434.35
Sum square samples=[(22.25~2+15.15~2+10.05~2+54.65~2)/6]
—CF=201.02
Sum square judges=[ (16 .05A2+14 .1^2+16 .55'v2+17 .35^2+
15.2~2+22.85~2)/4]-CF=ll.77
Sum square total=(3 .8^2+1.4~2+5 .2~2+4 .8~2+l.l~2+5 .95~2+
0 .85~2+2.25~2+l.4~2+2.75~2+3.2~2+
4.7~2+l.7~2+0.7~2+l.05*2+1.5*2+1.7*2+
3.4*2+9.7*2+9.75*2+8.9*2+8.3*2+9.2*2+
8.8*2)-CF=236.88
Note: the symbol *2 represents square.
Sum square error=236.88-11.77-201.02=24 .09
Degrees of freedom samples=4-l=3
Degrees of freedom judges=6-l=5
Degrees of freedom total=24-l=23
Degrees of freedom error=23-5-3=15
Mean square samples=201.02/3=67.0
Mean square Judges=ll.77/5=2 .35
Mean square error=24.09/15=1.6
F samples=67.0/1.6=41.88 samples different at 5% level
F judges=2.35/1.6=1.47
judges no different
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means
582
756
431
R
3.7
2.5
1.7 9.1
Applying Tukey's test:
Standar error=(l.6/6)~ 0 .5=0.52
Note: the symbol ~0.5 represents square root.
Least significant difference=0 .52*4 .08=2 .12
The samples
must differ 2.12 or
R
582
756
431
9.1
3.7
2.5
1.7
more to be significant
R-431=9.1-1.7=7.4 >2.12
R-756=9.1-2.5=6.6 >2.12
R-5 82=9.1-3.7=5.4 >2.12
582-431=3.7—1.7=2.0
582-756=3.7-2.5=1.2
756-431=2.5-1.7=0 .8
The sample R is significantly different from samples
582, 756 and 431.
Ill
G
Color Intensity
Worked as before, from Table 22:
CF=573.79
Sss=2.81
Ssj=15•85
Sst=139.42 :
, Sse=120.76
,
;
69
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Dfs=3
Df j=5
Dft=23
Dfe=15
M s s = 0 .94
M s j = 3 .17
M s e = 8 .05
III
Fs=0.12
samples no different
Fj=0.39
judges no different
H
Off Aroma Intensity
Worked as before, from Table 24:
CF=387.6
Ss's=57.89
Ssj=19.89
Sst=207.36
Sse=129.58
Df s=3
Df j=5
Dft=23
Dfe=15
Mss=19.29
Msj=3.98
Mse=8.64
70
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
III
Fs=2.23
samples no different
Fj=0.46
judges no different
J
Hedonic Scaling
Worked as before, from Table 26
CF=3 ,369.85
Sss=17.99
Ssj=80 .15
Sst=354 .15
Sse=256 .01
Df s=3
Dfj=25
Dft=103
Dfe=75
Mss=5.99
Ms j=3.21
Mse=3.41
Fs=1.76
samples no different
Fj=0.94
judges no different
71
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
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