Graduate Thesis Or Dissertation
 

Total fatty acid composition of autoxidized anchovy meal and studies of related model systems

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/6q182n86q

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  • The variation in fatty acid composition between the "bound" and "free" lipid in stored anchovy meal was determined using gas-liquid chromatographic analysis. A model system of fresh anchovy oil on powdered lactalbumin was also studied to determine the changes in extractability and fatty acid composition which occur during oxidation. All of the lipid-protein systems examined were first extracted with hexane. The extracted protein was then extracted with choroform:: methanol (2:1 v/v), and finally digested in HCl and the hydrolysate extracted with diethyl ether. The chloroform : methanol extract and HCl digestion represented oil which was bound to the protein. Each lipid extract was interesterified with methanol to yield the corresponding methyl esters, and these esters were then analyzed by gas-liquid chromatography. Both quantitative and qualitative analysis was carried out using a diethylene glycol succinate packed column in a gas chromatograph equipped with a hydrogen flame detector. The results of these investigations showed that the oil from anchovy meal differed markedly in fatty acid composition from the corresponding fresh oil. Although the types of fatty acids found were identical to those in the fresh oil, there was considerable quantitative variation. These differences were characterized by smaller amounts of polyunsaturated fatty acids in the meal, and correspondingly larger amounts of saturated and monoenoic fatty acids. The greatest change occurred in the acid, 20:5. Anchovy meal contained a "bound" lipid fraction which varied in quantitative fatty acid composition with the readily extractable lipid. The fractions associated with the protein had higher proportions of 22:4, 22:5, and 22:6, with the acid digest fraction considerably lower in the monoenoic fatty acids. The oxidation of anchovy oil and anchovy oil methyl esters on lactalbumin produced a reduction in hexane extractable lipid with a corresponding increase in lipid which was soluble only in chloroform : methanol or after HCl hydrolysis. These changes were more drastic when untreated anchovy oil was used. The oxidation of anchovy oil methyl esters on lactalbumin produced a reduction in the amounts of polyunsaturated fatty acids present in the hexane extract. The other solvent extractions, however, yielded only higher molecular weight compounds which could not be analyzed by GLC. These observations led to the conclusion that the fatty acids formed compounds which interacted before being bound to the protein.
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