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Analysis of Foodstuffs with Particular Reference to Quality Control.

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C O N F E R E N C E REPORTS
Analysis of Foodstuffs with Particular Reference to Quality Control
The Foodstuff and Juridical Chemistry Group of the Gesellschaft Deutscher Chemiker and the Selskabet for Levnedsmiddelteknologi og -hygiejne, anerkendt selskab under Dansk
Ingenimforening, held a joint meeting in Kiel from 17 to 19
September 1968. Four of the fourteen lectures are reported
below.
Recent Results concerning the Fate of
Sulfurous Acid in the Organism
By W. Diemair (Lecturer) and G . t'fleidererI*l
In order to follow the fate of sulfite in the organism we first
prepared 35SO:-, by Criess's method, namely, by evaporating
copper sulfate and carrier-free Na23%04 solution on a water
bath to complete dryness (87% yield). The yield measured
with a Packard liquid scintillation spectrometer was 94 %.
Sulfite can be determined in biological material by Engelhardt's method, namely, distillation in a modified ReithWillems apparatus with Tillmann's reagent. For determination of 3 5 s the organic tissues were freeze-dried. Combustion
in pure oxygen and absorption of the radioactive gaseous
combustion residues permits the very tedious chemical oxidation of the 35s compound to be avoided. The apparatus
described by Kalberer and Rufschmann was used.
I t was observed that sulfite taken perorally is oxidized rapidly
but not completely in the ileum. All ions resobed in the ileum
proceed first to the liver; the rapid diminution in the amount
of sulfite indicates a sulfite oxidase activity in Lung's sense.
The proportion of sulfite oxidized in the ileum is smaller the
emptier are the stomach and ileum. After 40 min most of the
sulfite in the jejunum is already oxidized to the extent of 40 %.
The residual sulfite is excreted almost wholly through the
kidneys. Sulfite can be detected only in traces in the liver. At
least in the liver the total activity is accounted for as sulfate;
introduction of 3 5 s from sulfite is not observed.
['I Prof. Dr. W. Diemair and Prof. Dr. G. Pfieiderer
Institut fur Lebensmittelchemie der Universitat
6 Frankfurt/Main, Georg-Voigt-Strasse 16 (Germany)
Studies of the Occurrence of Aflatoxin B1,
Migration and Changes in Content in the
Preparation of Some Foods
By E. Hanssen [*I
Aflatoxin B1 can be formed by Aspergillus[l-41 and other
types of mold [21, being contained both in the mycelium and
in the spores of this mycotoxin. That means that foodstuffs
may have toxic action even if not visibly contaminated with
mold. Penicillium species seem particularly liable to form
aflatoxin. In Penicillium species discovered on preserved
gherkins, stored at a temperature of 4"C, we found 0.150
ppm of aflatoxin B1, and in orange peel on which Penicilliirm
was growing we found 0.010 ppm.
The medium must fulfil definite requirements for growth of
Aspergillusflavus[51. We found that there is a minimum of
vitamin B content necessary for its growth. It could not be
956
grown on white bread dough o r biscuit dough (vitamin B1
content 0.50 ppm), though it grows very well o n whole wheat
dough (vitamin B1 content 3.00 ppm). We have followed the
separation of aflatoxin in the interior of the attacked material,
in a foodstuff whose cell structure had been destroyed
(whole wheat dough), and in a foodstuff with undamaged cell
structure (opened coconut). After about one week the content of aflatoxin B1 in the mycellium was 0.250 ppm; in the
layer 7 mm below the mycellium it was about 0.085 ppm,
both for cellular and non-cellular material. In the lowest
layers (between 2 and 7 cm) we found a very high content of
aflatoxin (about 0.800 ppm).
The aflatoxin B1 content of peanuts is decreased by 40% o n
dry roasting (130 "C, 5 min); it is reduced by about 20% of
the original content o n oil roasting (12O-15O0C, 6 min).
[*I Dr. E. Hanssen
H. Bahlsens Keksfabrik KG
3 Hannover, Podbielskistrasse 11 (Germany)
[I] E. Bodin and L. Gaufier,Ann. 1'Inst. Pasteur 20, 209 (1906).
[2] D.A . A . Mossel, Goldschmidt informiert I , 21 (1967).
[3] K . H. Frank, Arch. Lebensmittelhyg. 17, 237 (1966).
[4] F. Bur, Med. Ernahrung 7, 180 (1966).
[5] R . I. Mateles and J . C . Adye, J. appl. Microbiol. 13, 208
(1965).
Fluorimetric Determination of Some Antioxidants
By H.-P. Thier[*]
Alkyle sters of gallic acid, dihydronorguaiaretic acid (NDGA),
and the mixture of 2- and 3-fert-butyl-4-hydroxyanisole
(BHA) (2- and 3-tert-butyl-4-methoxyphenol)are used in
many countries as antioxidants for fats and fatty foodstuffs.
Sensitive fluorimetric methods have been worked out for
their quantitative determination.
Treatment in dimethylformamide/water (85: 15) with 1 % of
ethylene diamine is suitable for the determination of 0.01 to
10 pg/ml of the gallic esters. A blue fluorescence (A,
=
455 nm) is formed, which is measured after 2-3 h; its intensity is greatest for the propyl ester.
Condensing the guaiaretic acid with 5 % of ethylene diamine
in methanol/water (7: 3) leads to a product that fluoresces
green (Amax = 530nm). The intensity of fluorescence is
measured after 7-24 h, enabling 0.1-5 pg/ml of the acid to
be determined quantitatively. Gallic esters must be removed
previously.
When dissolved in acetonitrile and oxidized with cerium(rv)
sulfate in sulfuric acid, both the methoxyphenols gave 2tert-butyl-p-benzoquinone. When taken up in chloroform,
this quinone reacts with a 0.02% solution of potassium
cyanide in dimethyl sulfoxide/water (96:4) in 20 min, yielding
5-tert-butyl-2,3-dicyanohydroquinone,
which fluoresces blue
(Amax = 475nm), whence 0.5-5 [pg/ml of total methoxyphenol
can be determined.
[ * ] Dr. H.-P. Thier
Institut fur Angewandte Chemie
der Wniversitat Erlangen-Nurnberg
852 Erlangen, Schuhstrasse 19 (Germany)
Angew. Chem. infernat. Edit. 1 Vol. 7 (1968) /NO.
I2
Trypsin and Chymotrypsin Inhibitors in Foodstuffs
By J. Weder (Lecturer) and H.-D. Belitz[*]
Trypsin and chymotrypsin inhibitors have been shown to be
present in a very large number of foodstuffs, e.g., in milk, in
egg-white, in some animal organs, and in legumes, potatoes,
root crops, and cereals. Disturbances in which these inhibitors seem to have played a part have been observed from time
to time when these materials were fed to animals or man. The
inhibitors can be completely destroyed by sufficient heat
treatment. Data in the literature and our own observation111
show that, for instance in legumes, the thermal stability of
the trypsin and chymotrypsin inhibitors can vary very greatly
from species to species.
To obtain more precise information about this differing
behavior, we have isolated the trypsin and chymotrypsin
inhibitors from the legumes Pisum sativum var. balticum,
P. sativum var. Schneebergeri, Phaseolus vulgaris var. nanus,
Ph. coccineus, Lathyrusodoratrts, and Viciafaba, by extraction
of the ground seeds with HzS04 and fractional precipitation
with ammonium sulfate or, for Viciafaba, with acetone. The
specific activities of these crude inhibitors were 0.2 to 1.6 TIE
caslmg[**l and 0.3 to 0.8 CTIE cas/mg, or, for Viciafaba,
83 TIE ==/mg and 54 CTIE cas/mg. The pure inhibitor obtained, as described by Werle et nl. 121, from Lathyrus odoratus
by use of an insoluble trypsin derivative had 30 times the
activity of the crude preparation.
The following molecular weights were found by gel filtration
on Sephadex G 50 (sequence as above): 10800 and 15800
(2 fractions), 10900, 17100, 14600, 11700, and 10200. No
correlation could be found between thermal stability and
molecular weight.
The pure inhibitor from Lathyrus odoratus had a strikingly
high cysteine content, and an excess of acidic over basic
amino acids, but methionine was absent.
[VB 173 IE]
German version: Angew. Chem. 80, 1003 (1968)
[*I Dr.-Ing. J. Weder and Prof. Dr. H.-D. Belitz
Institut fur Lebensmittelchemie der Technischen Hochschule
8 Miinchen 2, Lothstr. 17 (Germany)
[**I TIEcas are trypsin inhibitor units and CTIEcas are chymotrypsin inhibitor units determined with casein as substrate, see
ref. [l].
[l] H.-D. Belirz, H. P. Wassner, and J . Weder, Z. LebensmittelUnters. u. -Forsch. 137, 211 (1968).
[2] H. Fritz, H. Schult, M. Hutzel, M . Wiedemann, and E. Werle,
Hoppe-Seylers 2. physiol. Chem. 348, 308 (1967).
SELECTED ABSTRACTS
The growth of anodic mercuric sulfide films on a mercury
electrode in solutions containing sulfide and the effect of
such films on the anodic dissolution of mercury have been
studied by R. D . Armstrong, D . F. Porter, and H. R. Thirsk
by measurement of potentiostatic switching curves. In the
initial stage of film formation, black mercuric sulfide (metacinnabarite, identified by electron diffraction) is deposited
on the electrode surface in two successive monolayers. Each
of these layers considerably reduces the rate of dissolution
of mercury to form HgSZz-. The current-voltage curve shows
a discontinuity for the formation of each monolayer of HgS.
It is mentioned that passivation processes on solid metal
electrodes could be similar in nature. / J. physic. Chemistry
72, 2300 (1968) / -Hz.
[Rd 921 IE]
The reaction of mercury atoms with chlorine atoms has been
investigated by D . G. Horne, R . Gosavi, and 0.P. Strausz.
The chlorine atoms were obtained by Aash photolysis of
CF3Cl sensitized by mercury vapor; the kinetics of the reaction were deduced from the absorption of HgCl at 2790 A.
The extinction coefficient of HgCl at 2790 was determined
as (1.6 rt 0.6). lo5 mole-' cm-1; the rate constant (second
order) of the reaction amounts to 3.1010 mole-1 sec-1 in
720 torr CF3CI and 0.9 * 1010 mole-1 sec-1 in 10 torr CF3CI f
710 torr Ar, and it is temperature-independent between 110
and 170 ' C . The rate constant (second order) of dimerization
of HgCl in the gas mixtures named has the value (3.0 f 1.8) .
1011 or (1.9 1.3) * 1011 mole-1 sec-1. / J. chem. Physics 48,
4758 (1968) / -Hz.
[Rd 925 IE]
*
The superconducting properties of ternary intermetallic compounds having a P-tungsten structure were studied by G. Otro.
The samples, which all had the composition Nb3(XI_,Mx)
with X = Al, Sn. or Ga and M Ga, Ge, In. or Sn, were
obtained by melting the powder-form elements under argon
in an electric arc and were studied in the quenched and in the
tempered state. In order to relate the transition temperature
-
Angew. Chem. internat. Edir.
Vol. 7 (1968)1No. 12
to other quantities that were not directly dependent on superconductivity, the lattice constants and micro-hardness of the
samples were measured. The highest transition temperature
was found for Nb3(Alo.7Geo.3) at 20.05 OK. As x varies in a
mixed-crystal series the transition temperature passes through
a maximum when a valence electron density of 0.26 A-3 is
reached. Further, the lowest micro-hardness and the highest
transition temperature occur together in one mixed-crystal
series. Tempering raises the transition temperature over that
of the quenched sample by a maximum of 1.3 "C. / Z. Physik
215, 323 (1968) / -Hz.
[Rd 926 IE]
The course of the synthesis of cyclooctatetraene by tetramerization of acetylene in the presence of nickel compounds has
been the subject of attempted quantum-chemical explanation
by E.-A. Reinsch. As well as fixing the geometrical relations
of the four acetylene molecules in a complex c ~ s - ~ N ~ ( C ~ H Z ) ~ X ~ ]
where X is a further unidentate iigand, the nickel has the
function of orienting two unpaired electrons spatially to two
acetylene ligands in such a way that a new C-C bond can be
formed. The orbitals necessary for this catalytic assistance
are singly occupied only in magnetically normal d8 complexes
(high spin); other electron configurations do not come into
consideration for this purpose. The special feature of paramagnetic nickel complexes in catalysis of this reaction is thus
explained. / Theor. chim. Acta 11, 296 (1968) / -Hz.
[Rd 927 IE]
Amide ions NH; as color centers in crystallme KCI, KBr, and
KI were investigated by R. Windheim. In an electric field or
under uniaxial mechanical strain the crystals show peculiarities due to the fact that the color centers are not centrosymmetric; the oscillator strengths of the UV bands at 295 nm
are larger in the HNH plane than perpendicular to it. The
NH; ions orient themselves, so far as possible, with their
dipoles in the (100) direction. The orientation favored under
uniaxial strain is that where the protons are separated as
957
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