Lipids. Food Chemistry. Berlin: Springer Berlin Heidelberg; 1999. pp. 152-236. [DOI: 10.1007/978-3-662-07281-3_4]

Effect of high stearic acid containing fat on markers forin vivolipid peroxidation

The objective of this study was to determine the effect of high stearic acid (SA) diets versus high polyunsaturated fatty acid (PUFA) diets on several measures of lipid peroxidation in vivo. Sprague-Dawley rats were fed diets that differed only in the fat source (8% by weight) for 19 weeks. High SA fats were beef tallow (BT) and cocoa butter (CB), high PUFA fats were soybean oil (SO) and menhaden oil (MO). Urine was analyzed for lipophilic aldehydes, the secondary products of lipid peroxidation, by HPLC. Decreases (P<0.05) were found for 4 nonpolar lipophilic aldehydes and related carbonyl compounds (NPC) and 4 polar lipophilic aldehydes and related carbonyl compounds (PC) when the BT-fed group was compared to the SO-fed group. Decreases were also found to be significant for total NPC (P<0.01) and total PC (P<0.05) between BT and SO-fed groups. Serum increase in resistance to oxidation (P<0.01) was found in the BT group when compared to the SO group. The differences in urine and serum measurements in the present experiment indicate lower level of lipid peroxidation in vivo due to the consumption of high SA containing BT diet compared to high PUFA containing SO diet without raising serum triglycerides and cholesterol levels significantly for the BT-fed groups.

Thermal oxidation of 9'-cis-neoxanthin in a model system containing peroxyacetic acid leads to the potent odorant beta-damascenone

The potent odorant beta-damascenone was formed directly from 9'-cis-neoxanthin in a model system by peroxyacetic acid oxidation and two-phase thermal degradation without the involvement of enzymatic activity. Beta-damascenone formation was heavily dependent on pH (optimum at 5.0) and temperature, occurring over the two sequential phases. The first was incubation with peroxyacetic acid at 60 degrees C for 90 min, and the second was at above 90 degrees C for 20 min. Only traces of beta-damascenone were formed on application of only one of the two phases. Formate and citrate solutions produced a much better environment for beta-damascenone formation than acetate and phosphate. About 7 microg/L beta-damascenone was formed from 5.8 mg/L 9'-cis-neoxanthin under optimal experimental condition. The detailed pathway by which beta-damascenone is formed remains to be elucidated.

Significance of volatile compounds produced by spoilage bacteria in vacuum-packed cold-smoked salmon (Salmo salar) analyzed by GC-MS and multivariate regression

Changes were studied in the concentration of 38 volatile compounds during chilled storage at 5 degrees C of six lots of commercially produced vacuum-packed cold-smoked salmon and sterile cold-smoked salmon. The majority of volatile compounds produced during spoilage of cold-smoked salmon were alcohols, which were produced by microbial activity. Partial least-squares regression of volatile compounds and sensory results allowed for a multiple compound quality index to be developed. This index was based on volatile bacterial metabolites, 1-propanol and 2-butanone, and 2-furancarboxaldehyde produced by autolytic activity. Only a few of the volatile compounds produced during spoilage of cold-smoked salmon had an aroma value high enough to indicate contribution to the spoilage off-flavor of cold-smoked salmon. These were trimethylamine, 3-methylbutanal, 2-methyl-1-butanol, 3-methyl-1-butanol, 1-penten-3-ol, and 1-propanol. The potency and importance of these compounds was confirmed by gas chromatography-olfactometry. The present study provides valuable information on the bacterial reactions responsible for spoilage off-flavors of cold-smoked salmon, which can be used to develop biosensors for on-pack shelf-life determinations.