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Journal of the Science of Food and Agriculture
J Sci Food Agric 80:705±710 (2000)
Influence of intramuscular fat content on lipid
composition, sensory qualities and consumer
acceptability of cured cooked ham
X Fernandez,1* J Mourot,2 B Lebret,2 S Gilbert3 and G Monin1
1
INRA, Meat Research Centre, Theix, F-63122 Saint-Genès Champanelle, France
INRA, Pig Research Centre, F-35590 L’Hermitage, France
3
ADIV, Association pour le Développement des Industries de la Viande, 2 Rue Chappe, F-63000 Clermont-Fd, France
2
Abstract: The present study is part of a project which aims to examine the in¯uence of intramuscular
fat (IMF) content on the sensory attributes and consumer acceptability of pork. An experiment was
conducted to evaluate the in¯uence of IMF level in muscle semimembranosus (SM) on the
composition of its lipid fraction and on the sensory qualities and consumer acceptability of cured
cooked hams. Thirty-two carcasses were selected 24 h after slaughter from 125 Duroc Landrace
castrated male pigs showing large variability in SM muscle IMF content and were assigned to four IMF
groups: 2%, 2±3%, 3±4% and >4%. Cured cooked ham slices were evaluated by a trained expert panel
of 12 members and by a group of 56 consumers. Results from lipid analyses indicate that (i) an increase
in IMF content was almost entirely re¯ected by an increase in the triglyceride content of the muscle
and (ii) higher IMF levels were associated with higher free fatty acid and monoglyceride and lower
cholesterol levels. The sensory evaluation of marbling signi®cantly increased with IMF level, whereas
other sensory qualities were unaffected. High IMF levels signi®cantly depreciated the consumer
perception of fat, aspect, taste and smell of ham slices. Overall, slices with the highest IMF levels got
the least favourable rating by consumers. The present study indicates that increased IMF levels in
muscle semimembranosus do not have signi®cant effects on the sensory attributes of cured cooked
hams, apart from the perception of marbling. However, high IMF levels have detrimental effects on the
acceptability by consumers.
# 2000 Society of Chemical Industry
Keywords: pig meat; cooked ham; sensory qualities; intramuscular fat; consumer acceptability
INTRODUCTION
It is generally accepted that an increased level of
intramuscular fat (IMF) has a positive in¯uence on the
sensory qualities of pig meat. However, a careful
examination of the literature reveals contradictory
results. Some studies indicate, or suggest, a positive
effect of IMF level on the sensory attributes of pork,1±6
whereas others do not show any in¯uence.7±12 Some
works reveal a negative in¯uence of IMF level on pork
sensory qualities.13,14 We recently demonstrated that
increased levels of IMF in muscle longissimus lumborum
could have detrimental effects on fresh meat acceptability by consumers owing to the in¯uence of visible
fat on the willingness to eat and to purchase the
meat.15 However, the results also showed that, as long
as the variations in IMF levels were not visually
detected, pork chops with higher IMF levels were
better appreciated by consumers. Increasing the level
of IMF without increasing the level of visible fat, could
be a way to improve the acceptability of fresh pork.
However, since cured cooked ham has a high
economic importance, at least in France, the in¯uence
of increased IMF levels on its acceptability by
consumers needs to be carefully evaluated. Indeed,
cooked ham is generally considered as a lean meat
product in France and higher IMF levels in this
product could have a detrimental effect on its
acceptability.
Previous results have shown that between pig
muscles of varying metabolic types the differences in
IMF levels were mostly due to differences in triglyceride level.16 However, to our knowledge there is a lack
of information concerning the relationship between
the variability in IMF level of a given muscle and the
variability of the composition of its lipid fraction.
Therefore in the present work the composition of the
lipid fraction was determined.
The present study is part of a project which aims to
examine the in¯uence of IMF level on the sensory
attributes of pork and on its acceptability by consumers. In this project, care has been taken to ensure
that the in¯uence of IMF level was assessed under
conditions where other factors likely to affect sensory
qualities, such as the rate and extent of post-mortem
* Correspondence to: X Fernandez, INRA, Meat Research Centre, Thiex, F-63122 Saint-Genès Champanelle, France
(Received 19 May 1999; revised version received 29 September 1999; accepted 10 December 1999)
# 2000 Society of Chemical Industry. J Sci Food Agric 0022±5142/2000/$17.50
705
X Fernandez et al
pH fall, were kept to a minimum level of variation.
This paper reports the results concerning cured
cooked ham. Results concerning fresh pork have been
presented in previous papers.6,15
MATERIALS AND METHODS
Animals
Animals were 125 castrated male pigs from a crossbreed between Duroc boars and Landrace sows. They
originated from the same farm and were reared in
collective pens on straw bedding, with ad libitum
feeding up to a live weight of 100±110 kg. The number
of pigs per pen (n = 32, 55 and 38) corresponds to the
number of pigs per slaughter day (one pen slaughtered
per day).
A sample (approximately 1 g) of muscle longissimus
thoracis (LT) was taken at 70 kg live weight using the
biopsy technique described by Talmant et al. 17 This
sample was used for the determination of glycolytic
potential18 in order to identify the pigs carrying the
RN- allele.19 In addition, a blood sample was taken for
the determination of halothane genotype using the
PCR technique.20
Sampling and measurements at slaughter
The pigs were delivered at the abattoir in the afternoon
preceding the slaughter day and were bled out after
manual low-voltage (250 V) electrical stunning for
approximately 10 s. They had free access to water
during the overnight lairage.
At 40 min post mortem a 2 g sample of LT was taken
at the level of the last rib for the measurement of pH
after homogenisation in 18 ml of 5 mM iodoacetate
(pH40). The pH was measured using a combined glass
electrode (Metler Toledo, Switzerland) connected to a
portable pH meter (Schott-GeraÈte, Germany).
At 24 h after slaughter the left-half carcass of each
animal was cut according to the usual French
practice21 and the following measurements were
carried out on the semimembranosus (SM):
. ultimate pH (pHu), directly in the muscle, using the
apparatus described above;
. re¯ectance spectra between 400 and 700 nm using a
Minolta spectrophotometer (Minolta Camera Ltd,
Japan). The colour coordinates (lightness L*, redness a*, yellowness b*) were calculated in the
CIELAB system.
A 50 g sample of the SM was taken for the
determination of intramuscular fat content according
to Folch et al. 22 The entire ham was then vacuum-
Group limits
m SEM
Table 1. Characteristics of the four IMF groups
(IMF given as %; n = 8 per group)
706
packed in polyethylene bags, stored at 4 °C for 2 days
and frozen at ÿ20 °C until processing.
Selection of experimental animals
A group of 32 experimental pigs was selected in order
to obtain a signi®cant variability in IMF content in SM
muscle. Apart from IMF content, several criteria were
retained for the selection of the 32 pigs among the
slaughtered animals. The criteria to ful®l were the
following:
. homozygote normal for the halothane gene (HALNN);
. non-carrier of the RN- allele, on the basis of
glycolytic potential;19
. pH40 > 6.1 in the LT muscle (to exclude PSE
carcasses);
. pHu < 6.0 in the SM muscle (to exclude DFD
hams).
Each of the 32 selected animals was assigned to one
of the four IMF groups determined on the basis of
IMF variability in the corresponding population
(Table 1).
Determination of lipid composition
The lipid composition was assessed by high-performance liquid chromatography coupled to an evaporative light-scattering detector (Sedere, Paris, France)
according to Leseigneur-Meynier and Gandemer23
and Stolywho et al. 24 The concentrations of the
different components were expressed as mg per 100 g
fresh muscle tissue.
Cured cooked ham processing
Vacuum-packed hams were thawed for 24±36 h at
4 °C. The hams were then deboned and trimmed of
skin and external fat. The brine, containing 2.7%
nitrited salt, was injected (8%) and the hams were
vacuum-packed and placed in individual moulds.
After a resting period of 12 h at 3 °C the hams were
steam-cooked in an oven for 7±8 h at a ®nal core
temperature of 67 °C.
Sensory analyses
Sensory analyses were carried out on entire ham slices.
The samples were evaluated individually by a trained
panel of 12 members. The order of presentation
followed a factorial rotation in order to take into
account the effect of rank. The following criteria were
evaluated: colour, smell and ¯avour intensities, marbling, dryness and toughness. Sensory attributes were
Group 1
Group 2
Group 3
Group 4
pa
2%
1.4 0.1a
2±3%
2.5 0.1b
3±4%
3.5 0.07c
> 4%
4.7 0.25d
***
a
Signi®cance level of the effect of IMF group: ***, p < 0.001.
Means lacking a common superscript differ signi®cantly at a = 0.05.
J Sci Food Agric 80:705±710 (2000)
IMF and cooked ham quality
Table 2. Quality traits of muscle
semimembranosus according to the level of
intramuscular fat (IMF) in experimental pigs
(m SEM; n = 8 per group)
pHu
L*
a*
b*
a
Group 1 ( 2%)
Group 2 (2±3%)
Group 3 (3±4%)
Group 4 (>4%)
pa
5.62 0.01
53.4 1.3
6.2 0.6
4.1 0.4
5.55 0.02
57.1 1.1
6.6 0.4
4.9 0.4
5.55 0.03
55.9 1.5
6.9 0.9
5.2 0.4
5.58 0.01
58.2 1.3
6.1 0.7
4.9 0.3
NS
NS
NS
NS
Signi®cance level of the effect of IMF group: NS, p > 0.10.
scored on a seven-point discrete scale from 1 = very
low to 7 = very high intensity.
In one session, each member of the jury received one
sample from each IMF group with two replicates.
Thus, after four sessions, 48 responses were collected
per IMF group.
Tests of acceptability by consumers
A random sample of 56 subjects, based on target
means for sex (28 men and 28 women) and age range
(18±25 (seven subjects per sex), 25±45 (14 subjects
per sex) and > 45 years old (seven subjects per sex)),
was selected from the reference ®le of ADIV (Association pour le DeÂveloppement des Industries de la
Viande). All consumers had already been involved in
surveys on pork acceptability and were regular
shoppers and/or consumers of cured cooked ham.
Each consumer evaluated a sample from each IMF
class, and each sample was evaluated by seven
consumers. The tests were carried out under laboratory conditions at ADIV.
Entire slices of ham, trimmed of external fat, were
evaluated by consumers. The consumers were asked to
express their willingness to purchase and consume the
product on a three-point scale (yes, maybe, no). They
were also asked to evaluate the amount of visible fat
and the aspect of the slice and to appreciate smell, taste
and texture. In addition, they expressed an overall
rating of the samples (from 1 = least favourable to
5 = most favourable).
Statistical analysis
Analyses of variance were performed using the GLM
procedure of SAS.25 The model included the main
effect of slaughter day and IMF group. When variance
analysis revealed a signi®cant effect, differences
between IMF groups were tested using Duncan's
multiple range test. The in¯uence of IMF class on the
distribution of consumer responses was tested using
the Friedman non-parametric test. When the Friedman test revealed a signi®cant effect, the Wilcoxon
non-parametric test was used for comparison of
means.
RESULTS AND DISCUSSION
Quality traits
The fact that meat quality indicators at slaughter (pH
and colour; Table 2) did not differ between IMF
groups allows us to conclude that the effect of IMF
level on sensory qualities and consumer acceptability
does not interfere with factors known to strongly affect
sensory qualities, such as rate and extent of postmortem pH fall (see eg Ref 26).
Composition of the lipid fraction
A marked effect of IMF group on the amount of
triglycerides (TG) was observed (Table 3). In group 4
(IMF > 4%) the amount of TG was four-fold higher
than that obtained in group 1 (IMF 2%). The data
are in accordance with previous works on pigs16,23
Group 1 ( 2%) Group 2 (2±3%) Group 3 (3±4%) Group 4 (>4%)
TG
DG
CHOL
MG
FFA
CL
PE
PI
PS
PC
SM
Table 3. Composition of the lipid fraction
according to the level of intramuscular fat (IMF)
in muscle semimembranosus of experimental
pigs (m SEM; n = 8 per group)
J Sci Food Agric 80:705±710 (2000)
1074 75a
ND
35.8 3.0a
1.5 0.3a
72.0 21.2ab
28.1 15.1a
19.2 8.6
3.2 2.6
3.5 2.6
211 42
2.7 0.9a
2158 142b
ND
38.2 3.1a
2.6 0.6a
39.3 26.1a
51.4 20.8ab
20.7 8.1
3.1 1.9
2.0 1.3
225 30
0.3 0.2b
2888 83c
3.5 2.3
30.5 1.7ab
6.1 1.9b
176 39bc
27.3 14.6a
21.9 7.7
1.7 1.0
0.7 0.5
317 99
1.2 0.7ab
4143 249d
ND
27.1 2.5b
13.1 4.3b
233 57c
111 37b
7.1 2.3
5.3 3.9
7.2 4.9
179 16
0.3 0.2b
pa
***
Ð
*
**
**
p = 0.06
NS
NS
NS
NS
*
Data are given as mg per 100 g muscle tissue.
a
Signi®cance level of the effect of IMF group: NS, p > 0.10;*, p < 0.05;**, p < 0.01;***, p < 0.001.
ND, non-detectable.
TG, triglycerides; DG, diglycerides; CHOL, cholesterol; MG, monoglycerides; FFA, free fatty acids; CL,
cardiolipin; PE, phosphatidylethanolamine; PI, phosphatidylinositol; PS, phosphatidylserine; PC, phosphatidylcholine; SM, sphingomyelin.
Within a row, means lacking a common superscript differ signi®cantly at a = 0.05.
707
X Fernandez et al
Table 4. Significance level of the effect of IMF
group on the sensory attributes of cured
cooked ham
Signi®cance level a
Marbling
Colour intensity
Smell intensity
Taste intensity
Dryness
Toughness
***
***
NS
NS
NS
NS
a
Signi®cance level of the effect of IMF group:
NS, p > 0.10;***, p < 0.001.
showing that triglycerides are the main components of
muscle lipids. Our data show that the increase in IMF
level in SM muscle is mostly due to an increase in
triglyceride content. To our knowledge, data comparing the lipid composition of a given muscle showing
variable IMF levels are not available. Nevertheless,
some authors have compared several muscles showing
different IMF levels.16,23 According to the muscles
considered, they also usually report that differences in
IMF content between muscles are mostly due to
differences in triglyceride content.
Increased IMF levels were associated with lower
cholesterol content and higher monoglyceride (MG)
and free fatty acid (FFA) levels. Higher MG and FFA
levels could indicate a higher lipolytic rate and/or a
lower capacity of lipid storage in the triglyceride form.
This is an interesting feature that deserves further
investigation. Signi®cant variations in cardiolipids and
sphingomyelin were noted between groups, but no
clear relationship with IMF level was proved.
Sensory qualities
As shown in Table 4, only marbling and colour
intensity were signi®cantly affected by IMF group.
Perception of marbling continuously increased with
IMF level (Fig 1), whereas the relationship between
IMF group and colour intensity was not clear (Fig 1).
The present data indicate that variability in semimembranosus IMF content within the observed range is
visually detectable on the entire slice of ham. It would
be of interest to study the concomitant variability in
IMF levels in other ham muscles. It is likely that IMF
content varies in the same manner between the
different muscles. IMF level was not an important
Figure 1. Effect of IMF level in muscle semimembranosus on the sensory
evaluation of marbling and colour intensity of cured cooked ham slices
(n = 8 per group) (vertical bars show the standard deviation).
708
Figure 2. Effect of IMF level in muscle semimembranosus on consumers’
willingness to eat (A) and to purchase (B) cured cooked ham slices (n = 8
per group).
source of variation in taste intensity and texture, by
contrast with the situation we observed in fresh meat of
the same pigs.6
Acceptability by consumers
The willingness to eat (Fig 2A) and to purchase (Fig
2B) the product was not signi®cantly affected by IMF
group. However, there was a trend towards a negative
relationship between the willingness to eat or to
purchase the product and IMF level when expressed
after tasting the ham.
The appreciation of texture by the consumer panel
was not signi®cantly affected by IMF group (not
shown). IMF level signi®cantly affected the perception
of fat (Table 5). The percentage of consumers who
found the product too fatty increased from 18 to 31%
Table 5. Influence of IMF class on consumer rating of cured cooked ham
slices
IMF class
Fat aspect
Not fatty enough
Convenient
Too fatty
Aspect of slices
4 ‡ 5 scores (most favourable)
3 score
1 ‡ 2 scores (less favourable)
Appreciation of taste
4 ‡ 5 scores (most favourable)
3 score
1 ‡ 2 scores (less favourable)
Appreciation of smell
4 ‡ 5 scores (most favourable)
3 score
1 ‡ 2 scores (less favourable)
<2%
2±3%
3±4%
>4%
15a
67
18
9ab
64
27
2bc
60
38
11c
58
31
58a
26
16
50ab
31
19
49bc
21
30
50c
25
25
67a
12
21
55ab
18
27
42ab
29
29
44b
22
34
56a
18
26
43ab
29
28
38b
35
27
43ab
33
24
Data are expressed as percentage of answers
Between columns, different superscripts indicate signi®cant differences
(p < 0.05) in the distribution of answers.
J Sci Food Agric 80:705±710 (2000)
IMF and cooked ham quality
Figure 3. Effect of IMF level in muscle semimembranosus on the overall
rating of cured cooked ham slices by consumers (n = 8 per group).
from group 1 to 4, whereas the percentage of
consumers who found the product convenient on this
aspect fell from 67 to 58%. This is in agreement with
the data obtained with the trained sensory panel.
As IMF level increased, the perception of the
appearance of the slices and the appreciation of taste
and smell were signi®cantly depreciated (Table 5).
This was shown by a decrease in the percentage of the
most favourable scores (4 ‡ 5) and a concomitant
increase in the percentage of the less favourable scores
(1 ‡ 2). It is particularly interesting to note that, by
contrast to what is usually reported for fresh meat,
high IMF levels have detrimental effects on the
perception of smell and ¯avour of cured cooked
ham. This probably contributed to the lower overall
score of the samples containing high amounts of IMF.
Indeed, the percentage of the most favourable scores
fell from 67 to 45%, whereas the percentage of the less
favourable scores increased from 13 to 26% (Fig 3),
with increased IMF levels.
CONCLUSIONS
Overall, the present study indicated that increased
IMF levels in muscle semimembranosus did not have
signi®cant effects on the sensory attributes of cured
cooked hams, apart from the perception of marbling.
However, high IMF levels had detrimental effects on
the acceptability by consumers. This must be kept in
mind before any long-term strategy is initiated to
increase the sensory qualities of fresh meat via an
increase in IMF level, if a part of the carcass is used for
production of cured cooked products.
ACKNOWLEDGEMENTS
The authors are indebted to P Vernin (INRA, Meat
Research Centre) and A Mounier (INRA, Porcine
Research Centre) for technical assistance. We wish to
thank D Malter (SELPA) for providing and taking
care of the animals.
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