Lipid degradation

The lipase-catalyzed fatty acid ester hydrolysis and the lipoxygenation of free polyunsaturated fatty acids are involved in the same lipid degradation pathway. They are respectively the first and second reaction in the lipoxygenase pathway (Fig. 3) [87-91]. The pathway produces volatile products of considerable importance in food technology including Cg[92, 93] or Cg- 94—96 aldehydes and alcohols from polyunsaturated fatty... 

There are a huge number of applications of GC/MS to lipid analysis in cultural heritage reported in the literature. Lipid characterization, together with the study of lipid degradation processes, is an important research area in conservation science [1 31]. 

Figure 5 Degradable PEG-lipid degradability via the orthoester function, the vinylether, or the disulfide group. Abbreviation PEG, poly(ethylene glycol). Source From Refs. 31, 35 0.

Potatoes contain a small amount of lipid, comprising approximately 0.1% of the fresh weight of the tuber (Galliard, 1973). Despite the minute quantity, lipids play an important role in the stability of processed potato products, since lipid degradation can lead to off-flavors and rancidity. 

Pancreatic enzymes required for dietary lipid degradation... 

Lipids are susceptible to oxidation and, as such, require analytical protocols to measure their quality. As described in vnitd2.i, autoxi-dation is one of the chief processes by which lipids degrade. The primary products from this reaction are hydroperoxides. These odorless and colorless transient species break down by various means to secondary products, which are generally odoriferous by nature. Being able to measure secondary oxidation products by simple spectrophotometric means is important for the food scientist so that he or she is able to characterize the extent of lipid oxidation. However, the researcher should be cautioned that one assay (e.g., TBA test) does not provide all the answers. To get a better picture of the story, both primary and secondary products of lipid oxidation should be assessed simultaneously by the different methods available (unitdu). 

Salih, A.M., Price, J.F., Smith, D.M., and Dawson, L.E. 1989. Lipid degradation in turkey breast meat during cooking and storage. Poultry Sci. 68 754-761. 

I. 1999b. Synthesis of deuterated volatile lipid degradation products to be used as internal standards in isotope dilution assays. 2. Vinyl ketones. 

Visioli F., Rodriguez de Turco E. B., Kreisman N. R., and Bazan N. G. (1994). Membrane lipid degradation is related to interictal cortical activity in a series of seizures. Metab Brain Dis. 9 161-170. 

The precursors used for process meat flavors are reviewed and also discussed will be non-Maillard interactions of ribose-5-phosphate and lipid degradation products with sulfur giving a real meaty odor and meat specie specific odor compounds, respectively. 

In this paper the relative importance of the Maillard reaction is discussed as well as the interaction of this with ribose-5-phosphate and lipid degradation products. 

In view of the ease with which H2S reacts with polyunsaturated aldehydes it is tempting to assume that during the cooking of meat interaction of these protein and lipid degradation products occurs. The reactive H2S-addition products initially formed can then easily react further with aldehydes and NH3 to give a vast variety of odorous compounds which would have a major contribution to the flavor of cooked meat. 

In some recent research on flavor formation during deep-fat frying at Rutgers University, a number of heterocyclic compounds with long-chain alkyl substituents were found the volatiles of fried chicken (15) and fried potato (16). These included pyridines, thiazoles, oxazoles, trithiolanes and a pyrazine. Only the involvement of lipids or lipid degradation products in the formation of... 

Effect of Phospholipids on Reaction Volatiles. As would be expected, the inclusion of phospholipids in the reaction mixtures produced many volatiles derived from lipid degradation these included hydrocarbons, alkylfurans, saturated and unsaturated alcohols, aldehydes and ketones. However, two other important observations were made. First, the concentrations of most of the hetero- cyclics, formed by the amino acid + ribose Maillard reaction, were reduced. For most of the major volatiles this reduction was of the order of 40 - 50%, but in the case of thiophenethiol and methyl- furanthiol the reduction was over 65%. This appears to support the findings that in meat and coconut, lipids exert a quenching effect on the amount of heterocyclic compounds formed in Maillard reactions during heat treatment (11,12). Second, and perhaps more important, the addition of phospholipid to the reaction mixtures resulted in the production of large amounts of compounds derived from the interaction of the lipid or its degradation products with Maillard reaction intermediates. 

Acetyl-CoA can be derived directly from metabolism, especially lipid degradation, or by the acetate thiokinase reaction ... 

Thiazoles with long alkyl chains in the 2-position provide evidence of the interaction of lipid oxidation products with Maillard intermediates. The presence of such thiazoles has been reported for fried chicken, roast beef, and fried potatoes (see Mottram152). Thiophens with long alkyl chains in the 2-position have also been encountered. They were obtained when phospholipid was added to a cysteine-ribose system.153 Lipid degradation to the 2,4-dienal, followed by reaction with H2S, was thought to be responsible.154... 

Nitric oxide-induced apoptosis in human leukemic lines requires mitochondrial lipid degradation and cytochrome c release, Blood 93 2342-2352. 

Nitric-oxide-induced apoptosis in human leukemic lines requires mitochondrial lipid degradation and cytochrome c mlease. Blood, 93 2342-2352 Wendel, A., 1981, Glutathione peroxidase. Methods Enzymol. 77 325-333... 

Voziyan PA, Metz TO, Baynes JW, and Hudson BG (2002) A post-Amadori inhibitor pyri-doxamine also inhibits chemical modification of proteins by scavenging carbonyl intermediates of carbohydrate and lipid degradation. Journal of Biological Chemistry 277, 3397- 03. 

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