| Fat (or lipid) is one of three main nutritional substances, and fatty acids are the main component of fat. Fatty acid nutrition, composition, and metabolism correlated with tissues growing and some diseases such as obesity, diabetes, cardiovascular disease, and inflammation. Beef is the main source of meat, fatty acids profiles of beef has a great significance on human health. Chinese Yellow cattle were used in present project to research the relationship between beef intramuscular fatty acids and serum indices, fatty acids changes of different beef tissues, and, the intramuscular fatty acids changes under different processing and treatments as well. The contents and results are listed below:PARTâ… SERUM INDEX AND FATTY ACIDSChapter 1. Relationship between serum index and fatty acids composition of beef muscle from Chinese Yellow cattle. Thirty eight Chinese Yellow Cattle were slaughtered, blood and muscle were taken to measure total cholesterol (TC), LDL-C, HDL-C, triglyceride (TG) and fatty acid, respectively, and to build the relationship between serum bio-chemistry index and fatty acid. The results obtained show that intramuscular fat content and saturated fatty acid (SFA) in storage fraction were positively correlated with age of Yellow cattle. TG as well as LDL-C content in serum had no correlation with fatty acid, while HDL-C and TC correlated with SFA composition in total lipid fraction positively, but correlated with unsaturated fatty acid composition negatively.PARTâ…¡FATTY ACIDS PROFILES OF DIFFERENT FACTORS PRESLAUGHTERINGChapter 2. Fatty acids profiles of different adipose tissues from Chinese Yellow cattle. Liver, epiploic fat, mesentery fat, perinephrit fat, subcutaneous fat, and intramuscular fat from beef spinalis dorsi (n=28) were used to determine fatty acids difference between liver and different adipose tissues. The results obtained show SFA composition of neutral fat fraction in liver was the highest (of 88.09%), followed by epiploic fat (83.34%) and mesentery fat (83.30%), SFA composition in perinephrit fat (62.04%), subcutaneous fat (62.76%), and intramuscular fat (61.06%) were the lowest. MUFA composition of neutral fat fraction in different tissues changed contrarily comparing with SFA changes, that MUFA composition in liver was the lowest (2.86%), while in intramuscular was the highest (30.95%). In total lipid, palmitic acid percentage hold constant, while, stearic acid percentage decreased from liver to intramuscular fat tissues with oleic acid increased step wisely. The conclusions lies that the route that stearic acid transferring into oleic acid and produce other polyunsaturated fatty acid was the main metabolization in fatty acids among different tissues.Chapter 3. Changes of fatty acids profiles in beef intramuscular fat with different gender. Twenty four bull calves of Chinese Yellow cattle breed were randomly assigned to two groups: castrates and intact males. Castration was done at weaning (6 to 8 months of age). After slaughtering, fatty acid composition of the intramuscular fat was analyzed in samples of muscle Longissimus dorsi taken after 2 days of ageing. The conclusion lies that, entire males had significant higher values of 17:0, 18:1 trans-9, 18:2 cis-9,12, P/S, and n-6/n-3 ratios and lower values of 16:0 and 18:1 cis-9, indicating that castration has an effect on the fatty acid composition of intramuscular fat of Longissimus dorsi.Chapter 4. Relationship between beef marbling standard and fatty acid composition of longissimus dorsi. Thirty beef longissimus dorsi from bulls of Chinese Yellow Cattle with marbling grade of 2, 3, and 4 were used to determine fatty acids changes with different intramuscular fat content. The results obtained show that water content and intramuscular fat content (IMF) correlated with beef marbling. Percentages of 16:0, 18:0 and SFA did not correlate with IMF, which showed that percentage of 16:0, 18:0 and SFA in beef longissimus dorsi were absolutely the same with subcutaneous fat. Percentages of 18: 1cis-9, MUFA and ratio of M/S were positively correlated with IMF, with beef marbling increased from Grade 4 to Grade 2, percentages of 18: 1cis-9 and MUFA and the ratio of M/S increased. However, percentages of 18: 2cis-9,12, PUFA and n-6PUFA and the ratio of P/S, n-6/n-3 were negatively correlated with IMF, and with beef marbling increased, percentages of 18: 2cis-9,11, PUFA, n-6PUFA and the ratio of P/S, n-6/n-3 decreased significantly. Composition of n-3PUFA in subcutaneous fat was lower significantly than that of beef intramuscular fat. PARTâ…¢FATTY ACIDS PROFILES OF BEEF WITH DIFFERENT FACTORS POST-MORTENChapter 5. Effect of cooking and microwave heating on the fatty acid composition of beef intramuscular lipid. Ten beef semitendinosus muscles from bulls of Chinese Yellow Cattle were used to determine fatty acids changes with beef cooked or microwave heated to different internal temperature (60℃, 70℃or 80℃). The results obtained show a great variability in the percentages of fatty acids in NL, PL and TL. Generally, PUFA of neutral fraction increased, while SFA did not change with beef cooked, which caused an increased ratio P/S in NL. However, PUFA content decreased and SFA content increased in PL and TL after beef cooking, which resulted in P/S ratio decrease. SFA increased with beef microwave heated in NL, PL and TL, while PUFA decreased in NL and TL, but not significant decreased in PL. These changes resulted in P/S decreased in NL, PL and TL with beef microwave heated. M/S ratios unchanged with two heating treatments in NL, PL and TL. Value of n-6/n-3 PUFA was increased significantly when beef internal temperature reached 80℃comparing with 60℃or 70℃despite of cooking or microwave heating. Results suggested that beef with storage (neutral)fat influent should be treated with cooking not microwave heating as P/S increased with cooking in NL and conjugated linoleic acid reduced significantly in NL, PL and TL.. And, beef should not be overcooked (=80℃) as n-6/n-3, IA (index of atherogenicity) and IT (index of thrombogenicity) increased significantly at the internal temperature of 80℃, which caused great changes of fatty acids and were not good for human health.Chapter 6. Effect of salt bloating combined with ultrasonic preparation on the fatty acid composition of beef semitendinosus muscle. Seven beef semitendinosus muscles from bulls of Chinese Yellow Cattle were used to determine fatty acids changes of intramuscular fat with beef NaC1 bloating (with concentration of 2%, 4%, and 6%) or NaCl bloating combined with ultrasonic (with 4 days of reservation under the circumstance temperature of 4℃). The results obtained show a great variability in the percentages of fatty acids in NL, PL and TL. Generally, salt bloating combined with ultrasonic preparation or not decreased percentage of palm acid as well as SFA. Whilst, salt bloating increased most of PUFAs, which resulted in ratio of P/S increased significantly. Salt bloating combined with ultrasonic preparation increased more of PUFA percentages and P/S ratio than salt bloating individually. Results suggested that beef prepared with salt bloating decreased SFA composition, indices of atherogenicity and indices of thrombogenicity, but increased PUFA and P/S. Salt bloating combined with ultrasonic preparation obtain prime bloating effect, and increase beef nutrition value as well.Chapter 7. Effect of low dose gamma irradiation on beef quality and fatty acid composition of beef intramuscular lipid. Eight semitendinous muscles obtained from Chinese Yellow Cattle were irradiated at 0, 1.13, 2.09, or 3.17 kGy using a 60Co irradiation source and then stored at 7℃for 10 days to estimate fatty acid changes of NL, PL and TL fractions, and beef quality changes with different gamma irradiation dose (0, 1.13, 2.09, or 3.17 kGy) and storage time (0 day or 10 days at 7℃). Composition of polyunsaturated fatty acid (PUFA), n-3 PUFA, and n-6 PUFA, decreased after irradiation, and these compositions unchanged with 10 days of storage. In TL value of P/S was lower in irradiated than non-irradiated beef with or without 10 days of storage. Purge loss and TBARS increased with irradiation dose increasing from 0 to 3.17 kGy in day 0. However, after 10 days of storage, purge loss and TBARS value decreased with irradiation dose increasing, and samples had the lowest purge loss and TBARS value at the dose of 3.17 kGy. Total bacterial counts decreased significantly with beef irradiated, and the reduction of total bacterial counts was proportional with irradiation dose increasing. It can be concluded that fatty acid percentages, compositions, ratios or indices changed with beef irradiated, however, no great change occur with irradiation dose increasing from 1.13 to 3.17 kGy within 10 days of storage. Low dose of 3 kGy gamma irradiation is recommended to apply in fresh beef before storage.
|
PDF Full Text Request