Application of Bromelain Extract for Muscle Foods Tenderization

This study investigates the tenderizing effects of bromelain extract (BE) obtained from the top phase of an aqueous two-phase system comprising of 18% PEG 6000–17% MgSO4 in muscle foods. Uniform-sized chunks of beef, chicken, and squid were marinated with different concentrations of BE (0, 3, 7%, and 20%, w/w) for 1 h at room temperature. The physico-chemical and quality characteristics of the marinated samples were determined. Decreases in pH and moisture content were observed in the samples BE treated, but the TCA-soluble peptides content significantly increased (p < 0.05). Water holding capacity and cooking yields were observed in all of the tested samples, especially when the concentration of BE increased. In addition, a reduction of meat firmness and toughness were also observed in all of the samples when compared to the control (p < 0.05). Electrophoretic patterns also revealed extensive proteolysis and a reduction in number and intensity of the protein bands in all of the treated samples. At the microstructural level, tissue fibers were broken, cell membranes were more strongly degraded, the connections between the sarcolemma and the myofibrils were disappeared, and the generation of numerous gaps could be clearly observed when 20% (w/w) BE was added. The results show that the bromelain extract derived from the two-phase extraction of a pineapple peel could be used as an effective meat tenderizer.

Impact of particle size of pulverized citrus peel tissue on changes in antioxidant properties of digested fluids during simulated in vitro digestion

To examine the effect of mechanical processing for plant-based materials on antioxidant properties during digestion,relationships between the size of pulverized plant tissue and changes in antioxidant activities during simulated in vitro digestion were investigated.The citrus peel tissue was pulverized and classified into four powder fractions followed their particle size distributions as 125−180m,180−355m,355−500m and 500−710m.These fractions were regarded as a plant tissue model with various degrees of cell damages.Powder samples were collected during the digestion and measured their particle sizes and colors.Besides,total phenolic content and antioxidant activities of digested fluid were also evaluated.The results showed that the powder color of smaller particles were significantly changed than the bigger ones.The bio-properties of digested fluid for the bigger particle sizes comparatively retained more than smaller ones at the simulated gastric stage.It also showed mostly stable during simulated gastric or small intestinal digestion stage.This suggested that the release of bioactive compounds from plant tissues during digestion could be related to their structural attributes such as degrees of cell damages which could be affected by processing methods and conditions.

Effect of digestive enzymes and pH on variation of bioavailability of green tea during simulated in vitro gastrointestinal digestion

To exam ine the effect of digestive attributes such as digestive enzymes and pH on changes in phenolic compound content and antioxidant activity during digestion,the bioavailability of green tea infusion was investigated using a simulated in vitro gastrointestinal digestion model.The total polyphenol content(TPC)decreased to 65%–70%throughout the mimicked normal digestion(MD)compared to the initial value.The total flavonoid content(TFC)decreased to approximately 25%after starting the gastric stage(pH 1.2);however,it regained to approximately 60%in the intestinal stage(pH 6.8).The mimicked digestive condition without digestive enzymes(WOE),which followed only the pH conditions of MD,showed significantly lower TPC and TFC values than MD.The percentage of antioxidant activity based on the initial values indexed by DPPH,ABTS,and FRAP gradually declined from approximately 60%at the gastric stage to approximately 40%at the final digestion stage.Meanwhile,the percentage of residual MIC was around 50%at the gastric stage.However,it gradually increased at the intestinal stage.The significantly lower antioxidant activity showed for WOE than MD throughout the simulated digestion.This study demonstrated that digestive enzymes and pH play a crucial role in the bioavailability of green tea infusion.

Effect of heat-moisture treatment to raw paddy rice(Oryza sativa L.)On cooked rice properties

Heat moisture treatment is safe and non-chemical use method for modifying physicochemical properties and digestibility of starch.Slow starch digestion in rice product would provide numerous health benefi ts for the consumers.This study investigated the heat-moisture treatment to the raw paddy rice at 60 and 80ºC for 4 and 24 h,and their effects on the attributes of cooked rice.The fi rmness,adhesiveness,starch hydrolysis and morphological changes during in vitro digestion were examined.Results showed that heat-moisture treatment to raw paddy rice for 24 h signifi cantly reduced the moisture content and could increase the total starch content of the rice grain.The apparent amylose content ranged from 23.83%to 25.65%at the variation in the values between treated and untreated rice.Enhancement in the firmness and reduction in the starch hydrolysis was found in rice treated by longer heating time of 24 h.Meanwhile,the adhesiveness of cooked rice was decreased when increasing the heating temperature.The morphological observation showed that the treated rice exhibited a honey-comb-like structure during simulated gastric digestion,while the untreated rice displayed a non-uniform structure.Noteworthy,the porous structure observed in all digested rice grains during simulated small intestinal digestion could favor the starch hydrolysis.This study showed that the heat-moisture treatment to the raw paddy rice at certain conditions obviously influenced the attributes of cooked rice,especially on the starch hydrolysis,which would provide a fundamental knowledge to enable development and improvement of slow digestion rice products.