摘要:

ABSTRACT.Concentrations of trans isomers of 18:2w6 and 18:3w3 were measured in soybean and canola oils purchased in the U. S. Fatty acid methyl esters were prepared by BF3catalyzed transesterification and separated using gas chromatography with Omegawax and CPSil88 capillary columns. Fatty acids were identified by comparing retention times with standards and with isomers of 18:2w6 and 18:3w3 in elaidinized linseed oil. Isomers identified included 18:2ct, 18:2tc, 18:3tct+ctt, 18:3cct, 18:3ctc, and 18:3tcc. The degree of isomerizations of 18:2w6 and 18:3w3 ranged from 0.3% to 3.3% and 6.6% to 37.1%, respectively. The trans contents were between 0.56% and 4.2% of the total fatty acids. Consumers will obtain isomerized essential fatty acids from vegetable oils currently marketed in the U. S.

ISSN:1065-7258    

DOI:10.1111/j.1745-4522.1994.tb00244.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.Pentanal and hexanal were the dominant volatile aldehydes generated from cooked pork during 3 weeks of refrigerated storage. Moreover, hexanal concentrations may serve as an index of meat flavor deterioration (MFD) during the early stages of storage; its concentration increased more rapidly than any other aldehyde. During the first 6 days, contribution of pentanal and hexanal to the total volatile aldehydes increased linearly by 350 and 650%, respectively, after which, their concentrations declined quite markedly. Reactions of pentanal and hexanal with meat components and/or their further oxidation may be responsible for this observation. Therefore, caution should be exercised when using hexanal as an indicator of lipid oxidation and MFD since a given hexanal level may correspond with two different points during storage of cooked meats.

ISSN:1065-7258    

DOI:10.1111/j.1745-4522.1994.tb00245.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.Moisture content (20–30%), temperature (100–200 C), screw speed (100–300 RPM), and degree of lipid unsaturation affected lipid‐macromolecule interaction during twin‐screw extrusion of corn meal. Interactions of indigenous corn meal lipids and added oils with the endosperm carbohydrates and proteins were evaluated by the availability of lipid to hexane extraction. A decrease of 61.1–88.5% lipid availability occurred at different moisture levels as a result of extrusion. The added oils apparently were more likely to bind to macromolecules during extrusion. The magnitude of this decrease was affected mostly by moisture content, degree of lipid unsaturation, and moisture content‐barrel temperature interaction. Maximum loss of lipid availability was observed when extrusion was carried out under low moisture, high temperature conditions, while the minimum was observed under high moisture, high temperature conditions. The more unsaturated lipid was less available for hexane extraction of corn meal dur

ISSN:1065-7258    

DOI:10.1111/j.1745-4522.1994.tb00246.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.Physical properties of lipid fractions isolated from anhydrous butter oil under various experimental conditions using supercritical carbon dioxide (SC‐CO2) extraction, intereseterification or their combination, together with thermal modification were assayed in terms of triacylglycerol and fatty acid profiles. SC‐CO2process, at 35C and 2000 psi, preferentially extracted the low‐molecular‐weight triacylglycerols, did not result in any separation of cholesterol and extracted an approximately constant fraction (7%) of the material in each 2h interval. Combination of SC‐CO2extraction with thermal fractionation yielded a butter oil fraction with improved spreadability at refrigerator temperatures. At higher pressure and longer extraction time SC‐CO2resulted in decreased solvent selectivity without increased extraction yield. The triacylglycerol and fatty acid profiles of high pressure 6000 psi extracts were remarkably similar to those of the butter itself. Chemical interesterification of butter oil randomized the constituent fatty acids, giving products which contained higher proportions of the middle‐range constituents. Thermal fractionation of interesterified butter yielded products only slightly enriched in higher molecular weight triacylglycerols, but interesterification of a solid obtained from thermal fractionation of butter gave a product greatly enriched in these compounds. Thus, modified lipid samples with distinct triacylglycerol and fatty acid compositions were prepared which may be used in different industrial

ISSN:1065-7258    

DOI:10.1111/j.1745-4522.1994.tb00247.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.A mixture of trilinolein isomers that contain one trans double bond was isolated from lightly processed carrots stored at low temperature in plastic bags. The mixture isolated was similar to the product synthesized from partial isomerization of trilinolein with the free radical isomerization catalyst p‐toluenesulfinic acid. Although the mixture contained at least 2 trilinolein isomers with c‐t and t‐c geometry, determination of the complete structure of the individual compounds was not possible because of the close similarity of their chromatographic properties. Under reduced oxygen storage conditions, significant quantities of unsaturated triglycerides with trans double bonds may be produced in lightly processed carrots by a nonenzymatic free radical rearrang

ISSN:1065-7258    

DOI:10.1111/j.1745-4522.1994.tb00248.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.This study was undertaken to determine detection thresholds of selected volatile organics known to be produced during the oxidation of food lipids. Gelatin was chosen to simulate a complex thermally‐sensitive food system. Stock solutions of pentanal, hexanal, t‐2‐hexenal, heptanal, t‐2‐octenal, and t,t,‐2,4‐decadienal were prepared using distilled water. A gelatin (3%) dispersion was prepared with distilled water, cooled (22C) then organic stock solutions were added to it at parts per billion (ppb) concentrations. A 16‐member panel was acquainted with the use of the sniffing apparatus with suprathreshold concentrations of the organics used in the study. Samples were presented in ascending order of concentration; judges indicated detectable point of specified stimulus. Odor characters are reported for these organics at each temperature. The detectable odor thresholds (DOT) were positively correlated with viscosity, and negatively correlated with temperature. DOT values ranged from 22 to 170 ppb. DOT values increased in the order of pentanal

ISSN:1065-7258    

DOI:10.1111/j.1745-4522.1994.tb00249.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY