摘要:

SUMMARYA kinetic procedure employing D values was used instead of the usual end‐point method to study heat inactivation of peroxidase in whole‐kernel sweet corn. Results at 150–200°F indicated that a heat‐labile fraction and a heat‐stable fraction were being inactivated. The resistant fraction represented 5% of total enzyme activity, and was concentrated in the pericarp. Increasing the blanch time at 200°F from 2 to 5 min decreased residual enzyme activity from 3.3% to 1.7%.Inactivation of the heat‐resistant fraction at 210–290°F also followed a first‐order reaction. The phantom inactivation‐time curve showed that an HTST process based on microbial destruction could leave resi

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00069.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYPeroxidase was regenerated in samples of peas that had been blanched just sufficiently to destroy the original peroxidase activity. The regeneration occurred after a few months in peas stored at −18° C, or within a few hours in thawed peas held at room temperature. The maximum activity regenerated was about 4% of the original activity. No regeneration occurred in peas given substantially more heat treatment than was needed for inactivation. Peroxidase regeneration during frozen storage, or after thawing, did not affect the quality of pe

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00070.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYAscorbic acid oxidation was studied in relation to the natural copper level and to lipid peroxidation in milks produced by cows receiving alfalfa bay or pasture. Correlations were highly significant (r = 0.79**) between ascorbic acid oxidation rate and natural copper for both alfalfa and pasture milks. The correlation between lipid peroxidation (by the TBA test) and ascorbic acid oxidation rate was very highly significant (r = 0.87***) in alfalfa milks but nonsignificant in pasture milks.Some postulated mechanisms for the action of copper and ascorbic acid in producing oxidized flavor were studied. The results do not support the theories of the role of the ascorbic acid radical, or of hydrogen peroxide, in the initiation of oxidized flavor.The kinetics of ascorbic acid oxidation by light, hydrogen peroxide, and ascorbic acid oxidase were examined. Zero‐order kinetics was found for light, and first‐order for the other age

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00071.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYTotal lipids, lipid phosphorus, and total polyenes extracted from mullet tissues with chloroform‐methanol show a progressive decrease in oxidizing mullet tissue. Thiobarbituric acid values from chloroform‐methanol extracts of oxidized tissues are approx 30–50% of those obtained from the unextracted tissue. Much of the TBA‐reactive material becomes concentrated in the inter‐facial fluff during the washing of such extracts. Chloroform alone extracts only about 10% of the TBA‐reacti

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00072.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYIn an attempt to determine the effect of oxygen and elevated temperature on freeze‐dried beef in a moisture‐free atmosphere, two series of storage experiments were conducted on freeze‐dried beef slices. In one longissimus dorsi muscle, and in the other semitendinosus, was packaged under commercially feasible conditions where the residual gas contained 2.5 ± 0.5% oxygen and no atmospheric moisture. An in‐can desiccant, calcium oxide (CaO), and an oxygen scavenger, Oxyban (glucose oxidase), were added in some instances, and the cans were stored up to 6 months at 100°F.In each series there was marked loss in extractability of actomyosin, and in activity of actomyosin ATPase after 1 month, but only a 40% loss of sarcoplasmic proteins. The residual aldolase activity decreased progressively to 8% at 6 months, whereas the residual water‐soluble proteins decreased progressively only to 56%. There was a marked difference between the two series in percent rehydration at 6 mouths: 81.1 in one, and only 26 in the second. Electrophoresis of the sarcoplasmic proteins showed gross denaturation after 1 mon

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00073.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYIt is shown that the washed muscle fibrils obtained from watery pork have a lower water retention at low ionic strength, and much lower extract‐ability at high ionic strength, than the fibrils from normal pork. These changes are accompanied by a gain of protein by the washed watery fibrils, and this protein originates from the soluble sarcoplasmic proteins. All the changes, including the characteristic gain of protein, can be artificially induced in normal meat by allowing it to pass into rigor at 37° C. The isoelectric region, or region of minimum swelling of watery fibrils, whether washed or unwashed, is similar to or slightly lower than that of normal fibrils. There is a broad isoelectric zone in both cases, extending from ∼pH 5 to ∼5.70. On the other hand, the IP of fully coagulated fibrils lies between 5.6 and 6.1. Washed and unwashed fibrils of watery meat show about the same degree of swelling at all pH values. Normal fibrils, however, show a higher water retention in the unwashed state than the washed. This effect is not due to the Mg or Ca ions included in the unwashed samples, but may result from interaction between the sarcoplasmic and fibrillar proteins. In the unwashed state, the swelling of normal fibrils is nearly double that of the watery fibrils at all pH values.It is shown that the rise of pH in intact carcasses of watery meat as they cooled from 37 to 10° C was probably due to the effect of temperature on the pK of ionizable groups of the proteins and buffering substances. It can be reproduced artificially and reversibly in native and coagulated minced meat, merely by raising or lowering the temperature. The titration curves of watery fibrils show similar titration constants (pK') to those of normal fibrils, but a loss of ratable groups. Heat coagulation, on the other hand, results not only in a bigger loss of titratable groups but in a much larger shift in the titration constants. These results can be interpreted to show that the fibrillar proteins of the watery fibrils are not denatured or aggregated in the usual sense, but are probably covered by a layer of denatured sarcoplasmic protein that is firmly‐bound to the surface of the myo

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00074.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00075.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYVolatile compounds in the aroma of five varieties of roasted and unroasted (raw) cocoa beans have been identified by mass spectral analysis and gas chromatography. The five common varieties selected for this study all contain the following compounds usually in this order of abundance: isovaleraldehyde, isobutyraldehyde, propionaldehyde, methyl alcohol, acetaldehyde, methyl acetate,n‐butyraldehyde, and diacetyl. An additional eight compounds appear in smaller amounts. As evidenced by gas chromatographic analysis, the raw bean aroma contains the same components but in lower concentrations. The principal differences between varieties are shown to be due to the ratios of these compounds rather than new compounds. The effect of roasting period on the concentration of four aldehydes in the aroma of the ground bean is show

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00076.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYThe carotenoids have been examined in the peel and pulp (the edible portion) of Meyer lemons. The principal carotenoid in the pulp was cryptoxanthin. The peel carotenoids included a number of unusual substances, including cryptoxanthin mono‐ and diepoxides and fractions tentatively identified as hydroxy derivatives of phytoene, phytofluene, and zeta‐carotene. An unusual polyene was also found. Apparently it contains two allylic hydroxyl groups, one of which is allylic to the conjugated double bond sys

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00077.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYA relationship between the degree of brownness produced by deep‐fat frying or by evaporating to dryness in a 100°C electric oven was established. Fresh pork as chops, in a water slurry, or a water extract developed varying degrees of brownness on heating. The amount of brown color development was related to the level of reducing sugars in the tissues. The degree of color development could be measured spectrophotometrically at a wavelength of 375 mμ. The development of brownness in buffered solutions was pH‐dependent, with maximum color being produced between pH 5.60 and

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00078.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY