Protease Properties And ACE Inhibitory Peptide Preparation From Wheat Germ And Development Of Bread

Wheat germ is rich in variety of nutrients,and endogenous enzyme system is complex.By activating endogenous enzyme activity and degrading storage materials to generate some functional materials such as ACE inhibitory peptides with the function of reducing blood pressure.In this study,wheat germ was partially purified and the main properties was identified and investigated.Endogenous proteases play the important roles for functional peptides formation during wheat germ incubation.In this study,wheat germ protease was purified patially and the main properties were charictarized firstly.After that,the incubation dondition was optimized by the regulation of time,temperature,pH and solid to liquid ratio.At last,the wheat germ incubation rich in ACE inhibitory peptides and wheatmeal were as the main raw material,and the functional wheat germ bread was developed.The main results are as follows:Endogenous protease of wheat germ was purified partially using ammonia sulfate.Proteases Proteolytic enzymes in the wheat genn extract were concentrated in the 20-60%saturation of ammonium sulfate precipitate.Using casein as substrate,the preliminarily purified protease had optimal activity at 50 ? and the maximal temperature stability at 30 ?.The protease had higher activity at pH 5.5 and pH 7.5,with the maximum activity for at pH 5.5.The protease was inhibited by Mg²⁺,Mn²⁺,Ba²⁺,pepstatin A,IAA,PMSF and EDTA,stimulated by Li+,Ca²⁺,Cu²⁺,2-ME and DTT.In addition,pepstatin A.IAA,PMSF and EDTA decreased protease activity significantly at pH 7.5.At pH 5.5 and 7.5,the enzyme had Km of 0.562 mg/mL and 4.935 mg/mL,respectively with casein as substrate.The protease had a higher affinity to casein than bovine serum albumin,ovalbumin and gelatin.Wheat germ proteases mainly are cysteine protease and serine protease.The effects of individual factor such as incubation time,temperature,initial pH and liquid to solid ratio on ACE inhibitory rate and peptide concentration of incubation medium were evaluated,respectively.The combinations of four factors were further optimized using a Box-Behnken design.Under the best incubation condition?pH 4.4 with a liquid to solid ratio 8.14 mL/g at temperature 47 ?,for 7 h?,maximum ACE inhibitory rate?92.16%?and peptide concentration?88.12 mg/g?were obtained,which were 6.2-folds and 2.4-folds respectively comparing to the un-incubated wheat germ.After incubation,wheat germ was rich in ACE inhibitory peptides.The incubation material was added to wheat flour and make bread with functions.The results showed that with the increase of wheat germ powder addition,the content of wet gluten reduced and bread changed to dark and thick aroma.When wheat germ addition was 5%,the colour,volume and structure of bread had no difference compared with bread made with pure wheat flour.In addition,we also investigated the effect of wheat germ fineness on quanlity of bread.When wheat gem was smashed to 120 mesh.Bread obtained a good quanlity.The best ingredients of wheat germ bread was adding 5%of wheat germ with 120 mesh.The produced bread in appearance,color,taste,smell,and other sensory characteristics,etc.are better than the ordinary bread.