الفهرس 
Cover Page Title in EnglishOnly 14 pages are availabe for public view
 |  | from | 80 |  |  |
| | | from | 80 | | |
Abstract
Consumer concerns on the quality of meat and meat products have greatly increased during past decades. ”Quality” and ”healthfulness” were reported to be one of the most important factors for influencing consumers choice for food Lipid peroxidation is a major problem in the food industry. It leads to quality deterioration, rancidity and accumu¬lation of potentially toxic compounds in foods as malondialdhyde, cholesterol oxidation products and oxidation of fatty acids The fatty acid composition and cholesterol levels in meat have received increasing attention owing to their implications in human health and product quality The aim of this study was to monitor lipid peroxidation parameters of fresh and frozen beef and mutton in Alexandria, markets and effect of freezing on meat quality through determination of the following parameters: Hydrogen Ion Concenteration (pH) - Acid Value (AV) and Free Fatty Acid (FFA) content 3-Malondialdehyde (MDA 4-Total Cholesterol, Triacylglycerols, High Density Lipoproteins (HDL-c), Low Density Lipoproteins (LDL-c) and Very Low Density Lipoproteins (vLDL-c )5-Fatty Acid analysis by Gas chromatography The study was done on brisket meat collected randomly from local butchers presents in Alexandria directly after slaughtering Meat samples were dissected and put in a moisture proof, protecting, transparent polyethylene bags and with an identification code then, taken immediately in ice boxes to the laboratory where they were divided to six groups each of three replicates: Group I : Fresh brisket beef meatGroup II: Fresh brisket mutton meat Group III: Brisket beef meat after freezing for 1 Month at -20°C Group IV: Brisket mutton meat after freezing for 1 Month at -20°C.Group V: Brisket beef meat after freezing for 2 Months at -20°C. Group VI: Brisket mutton meat after freezing for 2 Months at -20°C. Data obtained from this study were statistically analyzed and revealed the following: Effect of freezing on Meat pH: In our results we noticed that meat pH did not significantly (p<0.05) change as it keept within good pH range. So, we can say that freezing up to two months does not alter meat pH and keeps it within normal accepted range so keeps meat with good quality Effect of freezing on Fat rancidity: We noticed that acid value and free fatty acids content did not significantly change except mutton meat after two months decreased significantly as it was in beef and mutton. So, fat rancidity does not occur during freezing up to two months Effect of freezing on lipid peroxidation of meat: Our results showed that there is significant increase in MDA value after freezing for two months, while fresh and one month frozen samples showed no significant increase . This clearly demonstrates that the MDA seen in frozen samples was due to extended storage. Studies have shown that cold storage increases lipid peroxidation and thiobarbituric acid – reactive substances in food Paradoxically, freezing appears to have very little inhibitory effect on lipid peroxidation. Indeed studies have shown that freezing leads to timedependent increases in accumulation of lipid peroxidation products Effect of freezing on Meat Cholesterols: In fact, cholesterol is converted to cholesterol peroxyl radicals that, instead of propagating the peroxidative chain, largely decompose to a variety of non-radical products that are found commonly as oxysterols in membranes and LDL Freezing storage of meat leads to high decrease in cholesterol content In fat cells of both adipose tissues and muscle fibers, triacylglycerols (TAGs) are hydrolyzed by two important lipase systems: Lipoprotein lipase and hormone sensitive lipase producing FFAs, monoacylglycerols (MAGs) and diacylglycerols (DAGs) The data previously mentioned explain what we found in table 4 which shows significant decreaseof TC in beef and in mutton and also TAGs decreased significantly by freezing as decreased in beef and in mutton, on the other hand LDL-c increased significantly in beef and in mutton Effect of freezing on Meat Fatty Acids: During freezing storage, lipids are subject to some changes, mainly autooxidative and hydrolytic changes. This explains what we found as C20:3w3, C20:5 (EPA) was found only in fresh meat and disappear by freezing as freezing cause oxidation to PUFAs The significant increase of unsaturated fatty acids may suggest that during frozen storage processes other than oxidation may occur in meat fat and be responsible for the observed changes in the fatty acids profile Frozen meat samples can be stored for three months without significant changes to the fatty acid profile, provided that appropriate packing that limits the exposure to atmospheric oxygen is used. Freezing as a method of meat preservation causes only a small decrease in nutritive value, and natural health-promoting sub¬stances such as unsaturated fatty acids, are largely retained. As there is no significant(p<0.05) difference in fatty acids like (C10:0, C12:0, C14:0, C14:1,C15:1, C16:0, C18:2and C18:1) concentration in fresh and frozen meat .