摘要:

ABSTRACTHybrid striped bass were fed four diets containing 0, 4, 8, and 12% menhaden fish oil (MFO) for 18 weeks during final growth to determine (1) omega‐3 (n‐3) fatty acid uptake and its effect on fish and postharvest quality, and (2) the effects of selected antioxidants on oxidation and sensory quality of fish enhanced with n‐3 fatty acids. Lipid content was significantly higher in the two highest MFO treatments: 3.2, 3.5, 3.9 and 4.4% in the 0, 4, 8 and 12% MFO treatments, respectively. During this study EPA(eicosapentaenoic acid) significantly increased with increasing dietary MFO: 5.4 ± 0.93, 6.9 ± 0.15, 8.0 ± 0.45 and 8.1 ± 0.35 for the 0, 4, 8 and 12% MFO diets, respectively. The following fatty acids in muscle increased 1% or more in fish fed 12% MFO compared to fish fed 0% MFO: 14:0, 16:1n‐7, 22:6n‐3, and total polyunsaturates, total n‐3, and the n‐3/n‐6 ratio. Changes in individual fatty acids in fish muscle reflected the concentrations of fatty acids in the diet. Hybrid striped bass fed 8 and 12% MFO had twice as much n‐3 fatty acids (1.0 g/100 g tissue) as fish culture

ISSN:1065-7258    

DOI:10.1111/j.1745-4522.1995.tb00026.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTAnalytical supercritical fluid extraction (SFE) has been utilized to characterize the volatile content of oxidized vegetable oils. A major advantage of SFE is that the temperatures employed in the extraction reduce the probability of hydroperoxide decomposition. To test the SFE‐based method, canola, corn, soybean and sunflower oils were stored at 60C for 16 days in loosely capped bottles. The volatiles content of each oil was then desorbed by using supercritical CO2for extraction directly onto a gas chromatographic column where they were subsequently analyzed by gas chromatography‐mass spectrometry. Extraction conditions of 50C and 1500 psi were utilized for both the zero‐time oils and the oxidized oils to determine the change in concentration of the individual volatile compounds. Peroxide values (PV) were also determined for each oil and these ranged from 0.4 to 1.1 meq/kg for the zero‐time oils and from 52 to 82 meq/kg for the samples aged 16 days. These PV values all correlated well with the increase in concentration of several volatile compounds. Hexanal, the largest volatile peak found in the zero‐time oils, measured 0.4–0.6 ppm but increased to 52–366 ppm in the highly oxidized oils. Corn oil was the only oil that had measurable amounts of 2,4‐decadienal isomers at the initial sampling time. However, after storage, the decadienal isomers were found to be major volatile components in the total volatiles profile for all of the oils. The described SFE method proved to be a rapid and benign technique and very effective for determining the extent of oxidation in

ISSN:1065-7258    

DOI:10.1111/j.1745-4522.1995.tb00027.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTThe catechins, including epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG), and the theaflavins, including theaflavin (TF), theaflavin monogallate (TF‐1), and theaflavin digallate (TF‐2), were extracted from green tea and black tea, respectively. The 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical‐scavenging ability, superoxide‐scavenging efficiency, and lipid oxidation‐inhibition ability of the pure compounds listed above as well as epicatechin (EC), carnosol, carnosic acid, and butylated hydroxytoluene (BHT) were investigated.The DPPH radical‐scavenging ability of the catechins was EGCG>ECG>EGC>EC and of the theaflavins was TF‐2>TF‐1>TF. EGCG, ECG, EGC, TF‐2, TF‐1, and TF showed higher DPPH radical‐ and superoxide‐scavenging abilities than carnosol, carnosic acid, and BHT. EGCG, ECG, EGC, carnosol, and carnosic acid showed higher lipid oxidation‐inhibition activity, as measured by the Rancimat m

ISSN:1065-7258    

DOI:10.1111/j.1745-4522.1995.tb00028.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTA crude mixture of catechins was isolated from Chinese green tea leaves using a hot water extraction. Individual catechins were then separated by chromatographic means using Sephadex LH‐20 followed by semi‐preparative HPLC. The antioxidant activity of crude and individual catechins was then determined in a β‐carotene‐linoleate model system. Results indicated that (−)‐epicatechin‐3‐gallate (ECG) possessed the strongest antioxidative activity and (−)‐epigallocatechin (EGC) showed the weakest effect. The antioxidative efficacy of (−)‐epicatechin (EC) and (−)‐epigallocatechin‐3‐gallate (EGCG) was similar and in between those of ECG and EGC. Furthermore, the antioxidant activity of a reconstituted catechin mixture in the proportions present in the crude extract was lower than that of the crude mixture itself, thus indicating that noncatechin components in the mixture possessed their own antioxidant activity or acted sy

ISSN:1065-7258    

DOI:10.1111/j.1745-4522.1995.tb00029.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTConjugated linoleic acid (CLA) is a potential anticarcinogenic compound found in beef. The ability of antioxidants and hydrogen donors to influence CLA concentrations in ground beef during cooking (broiled, 80C) and storage was determined. Addition of food additives such as carnosine, cysteine, ascorbate, whey protein concentrate or beef plasma to ground beef did not result in any significant increases or decreases in CLA concentrations in freshly cooked beef. Additives which inhibited formation of thiobarbituric acid reactive substances in stored meat including 2.0% WPC, 0.5 and 2% beef plasma, ascorbate (0.5%) and carnosine (0.5%) were not any more effective at increasing or decreasing total CLA concentrations than additives which did not inhibit lipid oxidation during storage (0.5% WPC and 0.5% cysteine). Lack of changes in CLA in the presence of antioxidants suggests that these additives could be used to inhibit flavor deterioration of cooked beef products without decreasing CLA concentrations.

ISSN:1065-7258    

DOI:10.1111/j.1745-4522.1995.tb00030.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTThe potential role of α‐tocopherol in protecting the muscle lipids of smoked, farmed Atlantic salmon (Salmo salar) and of Atlantic mackerel (Scomber scombrus) from oxidative degradation was examined over a period of 12 weeks. One smoked salmon sample had much more α‐tocopherol than the other, but this higher tocopherol level dropped in parallel to the decrease in α‐tocopherol in the mackerel, a species known to be very susceptible to the development of rancidity. The other salmon sample started with less α‐tocopherol but showed no decrease in α‐tocopherol. The salmon samples developed a similar level of peroxides over 12 weeks, both being less than the peroxides in the 12‐week sample of the mackerel lipid where α‐tocopherol could not be mea

ISSN:1065-7258    

DOI:10.1111/j.1745-4522.1995.tb00031.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY