| Tibetan sheep meat with Sichuan characteristics were used to study the effects of different heat-processing methods on protein oxidation and in vitro digestibility of protein in simulated digestion.Microwaving,pan-frying,deep-oil frying,steaming and boiling methods were used,and texture characteristics,protein oxidation and Maillard reaction of cooked mutton products were evaluated by texture analyzer,color difference analyzer and spectrophotometer.The protein in vitro digestibility of mutton products with different heat treatments and the subsequent oxidation of protein during simulated digestion were investigated.The researches and the results were as follows:1.The effects of microwaving,pan-frying,deep-oil frying,steaming and boiling on the eating quality and protein oxidation of mutton cake were studied.The texture characteristics,protein oxidation index and HMF content of mutton products were determined to evaluate the edible quality and protein oxidation degree of mutton products.The results showed that the hardness,shearing force and chewiness of steaming and boiling treatment were lower than those of pan-frying,deep-oil frying and microwave treatment(p < 0.05),the meat color was good and the edible quality was higher.The hardness and shearing force of mutton samples were greater than those of other processing methods(p < 0.05).The color of mutton gradually darkened and turned to burnt red with the increase of the central temperature of the meat samples.The loss rate of mutton samples after frying and frying was the highest(p < 0.05).Steaming and boiling had little effect on the loss rate of mutton samples.When the central point temperature was 90 C,the water loss rate of deep-oil frying treatment was 49.33%,and that of pan-frying was 53.71%,which is higher than that of microwaving,steaming and boilinging at the same central point temperature.Steaming and cooking treatments have less influence on the meat loss rate.Steaming and boiling treatments make the changes of meat protein oxidation index minimum,while pan-frying and deep-oil frying treatments aggravate the oxidation of meat protein.,The carbonyl content of pan-frying and deep-oil frying proteins increased to 12.10 nmol/mg and 11.69 nmol/mg at the central point temperature of 90 C,respectively,which was nearly 6 times higher than that of the sample control.Among the meat samples processed by different heat treatments,the content of HFM in the pan-frying and deep-oil frying treatment groups was significantly higher than that in other heating groups,followed by the microwave treatment group,and the steaming and boiling treatment groups were the smallest.Comprehensive analysis showed that excessive heating could lead to the deterioration of the texture and nutritional quality of mutton cake.Under the conditions of steaming and boiling,the quality of food and nutrition of mutton products was the highest,and the degree of protein oxidation was low.2.The protein oxidation and digestibility of mutton products with different central temperatures(50,60,70,80 and 90?)treated by microwave heating in vitro were studied.The results showed that the digestibility of gastric digestive protein and intestinal digestive protein was 46.88% and 72.15% respectively at the central point temperature of 80 ?,the heat-treated mutton protein oxidation deepened during simulated gastrointestinal digestion,and changed more dramatically during intestinal digestion.After digestion in stomach and intestine,the digestibility of protein,carbonyl content of protein and free amino content in microwave-treated meat samples were significantly higher than those in unheated meat samples(p < 0.05),and after digestion in intestine,these indexes were significantly higher than those in gastric digestion stage(p < 0.05).After gastric digestion,the sulfhydryl content decreased to 73.63 nmol/mg at the central point temperature of 90 C.After intestinal digestion,the free sulfhydryl content decreased significantly,even significantly lower than that before digestion(p < 0.05).After microwave heating,the content of protein sulfhydryl group in meat digested by stomach was significantly higher than that in undigested meat(p < 0.05).With the increase of temperature at the center of meat sample,the content of protein sulfhydryl group increased first and then decreased.After intestinal digestion,the number of free sulfhydryl groups in meat samples decreased significantly,even significantly lower than that before digestion(p < 0.05).SDS-PAGE electrophoresis and free amino content showed that microwave heating could improve the digestibility of mutton protein to a certain extent,and the digestibility of mutton protein decreased with the heating time.3.The protein oxidation and digestibility of mutton products prepared by panfrying and deep-oil frying with different central temperatures during simulated digestion in vitro were studied.The results showed that the degree of protein oxidation of mutton products increased after pan-frying and deep-oil frying,and further intensified after gastric digestion,after gastric digestion,the digestibility of pan-frying protein was 50.91% and that of deep-oil frying protein was 54.93% at the central point temperature of 80?.The degree of protein oxidation was the highest after intestinal digestion.The digestibility of protein in meat samples after intestinal digestion was higher than that during gastric digestion.After digestion,the content of free sulfhydryl group in meat samples decreased,the carbonyl content of pan-frying and deep-oil frying protein decreased to about 40 nmol/mg,even significantly lower than that before digestion(p < 0.05).During the gastric digestion stage,with the prolongation of heating time during pan-frying and deep-oil frying,the macromolecule proteins(48~135 kDa)in meat samples were oxidized to form dense structure,which reduced the digestibility of protein.4.The protein oxidation and digestibility of mutton products steamed and boiled at different temperatures during simulated digestion in vitro were studied.The results showed that the digestibility of protein in steamed and boiled meat increased first and then decreased with the increase of temperature at the center of the meat sample,and the digestibility of protein in intestinal digestion was significantly higher than that in gastric digestion(p < 0.05),after gastric digestion,the digestibility of protein in steaming treatment reached 65.58% when the central point temperature was 70?,and that in boiling treatment increased to 61.74% when the central point temperature was 80?,after intestinal digestion,when the central point temperature was 70?,the digestion rate of protein reached 83.10% in steaming treatment and 79.89% in boiling treatment.In intestinal digestion stage,the oxidation degree of protein in steamed and boiled mutton products was more serious than that in gastric digestion stage.The carbonyl content and free amino content of protein in meat samples after intestinal digestion were significantly higher than those in gastric digestion stage(p < 0.05),while the sulfhydryl content in meat samples during gastric digestion stage was significantly lower than that in meat samples before digestion(p < 0.05),and even significantly lower than that before digestion(p < 0.05).After gastric digestion,small molecular weight protein bands were observed in SDS-PAGE electrophoresis.Combining with the change of free amino content,the digestibility of mutton product was better under the two treatments of steaming and boiling.With the increase of heating time,the digestibility of meat protein was worse.In conclusion,steaming and boiling mutton products have better meat color quality and higher edible quality,and have less effect on protein oxidation.After in vitro simulated digestion,the protein digestibility is higher.However,with the increase of the temperature at the center point of the meat sample and the prolongation of heating time,the protein digestibility will be worse.Therefore,the best temperature from the steaming and boiling heated mutton products to the center point is 70?.Mutton products are of the best quality and easy to be absorbed by human body.Compared with steaming and boiling,microwave treatment has a greater impact on protein oxidation of mutton products.Pan-frying and deep-oil frying have the most significant impact on protein oxidation and digestibility,while digestibility is the worst. |
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