Effect Of Protein Enzyme Hydrolysates On Promotion Of Yoghurt Cultures

With development of domestic economic and increase of consumer healthy concept,food owning probiotic function gained much. attention. LAB as one of the probiotic bacterials is used and applied widely, and play an important role in food produce and consumer health. Based on research of LAB, enhancing the number of viable cells of LAB is a difficult problem in domestic research.It is urgent to resolve this problem to reduce the difference between domestic and foreign status, as well as to promote the ability of developing DVS independently.The nutrion LAB needed is complicated, protein as one of energy source plays an important role in LAB growth.Through prious research literatures, it is easily to find that LAB perfer peptides to free amino acids.Three kinds of proteins are hydrolyzed by another three kinds of proteases to get various types of hydrolysates and to culture yoghurt culture, at the same time to test their effects on promotion of yoghurt culture and choose the optimum nitrogen source for LAB, which would change dependence on import of DVS and promote development of dairy industry.This study contains research of yoghurt basic growth condition,hydrolysis degree of different proteins used various enzymes,effect of protein hydrolysates on promotion of LAB and components of these hydrolysates by analysis of protein chromatography.In the first part, enzyme activity and protein content have been researched.Under the optimum temperature and pH conditions, three enzymes are used to hydrolyze all proteins respectively and test degree of hydrolysis (DH).The results showed that all the proteins are effectly hydrolyzed by enzymes and can be used for following researches.In the Second part, protein hydrolysates are added to MRS or M17medium to evaluate OD value,pH and titration acidity of medium to text effect of hydrolysates on promotion of yoghurt cultures.The result showed that both baterials can grow well in modified medium.Whey protein hydrolysates can best promote the growth of S18,pepsine and alkaline protease can enhance the number of viable cells as one magnitude.Effects of casein and soy bean become weaker in sequence.Effect of protein hydrolysates on promotion of L15gratually become weak as following sequence:casein hydrolysates,whey hydrolysates and soybean hydrolysates.In short, protein hydrolysates put greater effect on increasing number of viable cells of S18.In the third part,measuring the range of molecular weight of protein hydrolysates and components of peptides by protein chromatography and automatic amino acids analyzer could help infer the length of hydrolysates. Automatic amino acids analyzer can tell the constitution and content of amino acids.The result showed that except whey protein hydrolysates of pepsin and trypsin as well as soy bean protein hydrolysates of alkaline protease having few kinds of amino acids,the kind of amino acids of other hydrolysates is nearly15.It is found that even if the same protein can have different compositions and contents of amino acids, which showed that the specity of protease can make huge effect on moleculer weight of hydrolysates and constitution of amino acids.