鸡肉蛋白酶解产物稳定性的研究

为研究鸡肉蛋白酶解产物抗氧化活性的稳定性,采用木瓜蛋白酶水解鸡肉蛋白,研究灭酶方法、蒸发浓缩、干燥以及贮藏时间对鸡肉蛋白酶解产物抗氧化活性的影响。研究表明：灭酶方法、蒸发浓缩、干燥对鸡肉蛋白酶解产物的DPPH自由基清除活性、还原力影响均不显著（P〉0.05）;鸡肉蛋白酶解产物无论是以冷藏液、冷冻液还是干燥粉末形式贮藏,其DPPH自由基清除活性和还原力在半年内均无明显变化（P〉0.05）,证明鸡肉蛋白酶解产物的抗氧化活性具有良好的热稳定性和贮藏稳定性。     

LIPID OXIDATION IN A CHICKEN MODEL SYSTEM: ROLE OF LIPID AND PROTEIN FIBERS

Chicken muscle model systems were exposed to varying concentrations of lipid and protein fibers to clarify the role of these constituents in lipid oxidation. In this study, the lipid substrates examined included triacylglycerols, membrane phospholipid fractions, isolated phospholipid fractions, and free fatty acids. In iron-ascorbate catalyzed systems, increases in lipid concentration failed to lead to enhanced levels of oxidation at the examined times. Lipid was therefore not considered a rate limiting factor in the oxidation of muscle systems. Protein fibers accelerated oxidation only in sarcoplasmic reticulum (SR) membrane systems when catalyzed by iron-ascorbate. Enhanced interaction of the low molecular weight iron with the membrane lipids may be responsible for this unique response. Preferential oxidation of sulfhydryl groups in protein fibers, on the other hand, could account for the antioxidant effect displayed by protein fibers in methemoglobin catalyzed systems.     

ANTIOXIDANT EFFECTIVENESS IN INTERMEDIATE MOISTURE CONTENT MODEL SYSTEMS

The effectiveness of antioxidants was studied in methyl linoleate-carbohydrate model systems at the intermediate moisture content. Systems showing sorption hysteresis were used in the range of A_w0.68–0.84. Metal chelating agents were found to be more effective than free radical chain terminators. The antioxidant effectiveness of EDTA (a chelator) was greater in the higher moisture desorption systems since more would be expected to be in solution. The work also showed that metal catalyst activity is responsible for the rapid oxidation rates in intermediate moisture systems as compared to dry systems.     

ANTIOXIDANT ACTIVITY OF PROTEIN HYDROLYZATES FROM BY-PRODUCTS OF THE FOOD INDUSTRY

Hydrolyzate was obtained from cracklings (CEH) using Alcalase. Hydrolyzates were also prepared from cracklings (CAH) and chicken feathers (FAH) using hydrochloric acid. Antioxidative activity of the above hydrolyzates was evaluated by spectroscopic methods. The oxidative stability of lard with the addition of hydrolyzates was tested using a Rancimat and an Oxidograph apparatus set at 110C. Hydrolyzates were analyzed using RP-HPLC method. The highest antioxidative efficacy of hydrolyzates examined was found for CEH at an addition level of 0.25 and 0.50% N_tot using spectroscopic methods. The antioxidant effect of BHT at a level of 0.01% N_tot was stronger than that of all Hydrolyzates tested. The strongest antioxidant effects evaluated using the Rancimat method were noted for both acid hydrolyzates applied at level of 0.5% N_tot. Antioxidant activity of BHT, added to lard at a 0.02% level, was lower than those of CEH, CAH and GAH at a level of 0.5% N_tot. Superior antioxidant activity determined under conditions of the Oxidograph test was observed for CAH at a level of 0.5% N_tot. Antioxidant activities observed from synthetic antioxidants added to lard at a 0.02% level were higher than those from any of the three hydrolyzates tested. RP-RP-HPLC chromatograms of the acid hydrolyzates (CAH and FAH) were similar. A completely diferent looking chromatogram was obtained for the enzymatic hydrolyzate (CEH). It was characterized as having many, not well-separated peaks originating from peptides.     

EFFECT OF GAMMA IRRADIATION ON THE LIPID PEROXIDATION IN CHICKEN, LAMB AND BUFFALO MEAT DURING CHILLED STORAGE

Chicken, lamb and buffalo meat were subjected to low-dose gamma irradiation (2.5 kGy) and stored at 0–3C. Lipid peroxidation in terms of thiobarbituric acid (TBA) number and carbonyl content were monitored during storage. While irradiated meat showed slight increase in TBA number and carbonyl content on storage as compared to nonirradiated meat, this did not affect the sensory qualities of meat. Free fatty acid content decreased markedly on irradiation. Irradiated meats were microbiologically safe and sensorily acceptable up to 4 weeks in the nonfrozen state (0–3C) while nonirradiated meat had a shelf-life of less than 2 weeks .     

ANTIMICROBIAL AND ANTIOXIDANT ACTIVITIES OF CORN GLUTEN MEAL SUBSTANCES IN AN EMULSIFIED MEAT MODEL SYSTEM

Corn gluten meal (CGM) and pH adjusted (6.6)/particle size-reduced (∼7μm-MC7; ∼38μm-MC38) CGM increased oxidative and microbiological shelf-life of a model emulsified meat system. After 14 days, TBARS were significantly lower for samples containing MC7 and MC38 when compared to controls, and samples containing soy protein isolate (SPI) or native CGM. Based on aerobic plate counts, MC38 and CGM increased product shelf-life by ∼7days compared to SPI- and MC7-containing products and controls. These results suggest that the use of corn gluten meal substances in an emulsified meat product could create a more shelf stable product. These functional characteristics may make the incorporation of corn gluten meal into foods more feasible.