Study On Influence Of Lactobacillus Helveticus KLDS 1.0432 On Physical, Chemical And Microbial Characters Of Gouda Cheese

Milk and milk products are the best animal protein foods for human and are an important resource of human dietary protein.Results show that they not only provide rich nutrients with human but also are an important resource of a range of bioactive peptides,including opioid peptide that can calm and soothe the nerves,antihypertensive peptides,immunostim(?)lating peptides, caseinophosphopeptides that can bound metal ions,antithrombotic peptide,glycomacropeptide, casein macropeptide,and antimicrobial peptide etc.Milk-derived bioactive peptices are becoming hotspots in dairy products research because these bioactive peptides are discovered.Among all bioactive peptides,antihypertensive peptides are studied the most systemically and deeply,and they have the most potential application value.Recently,it has been demonstrated that antihypertensive peptides derived from milk protein were safe and had no side-effects,so the peptides are important both in theory and in practice to prevent hypertension.Lb.helveticus is one of lactic acid bacteria and its ability to hydrolyze protein is very strong.It can produce many kinds of b(?)oactive peptides by fermenting milk.A doctor of our laboratory has screened the Lb.helveticus strain that can produce strong ACE inhibitory activity by fermenting milk.The Lb.helveticus s()rain is added to Gouda cheese and its influence on physical and chemical indicators of cheese,the survival of bacteria,proteolytic,ACE inhibitory activity and sensory evaluation during cheese ripening are evaluated.Four Gouda cheese samples(two control samples with only starter lactococci,two experimental samples with lactococci and Lb.helveticus KLDS 1.0432) were prepared.Then the cheese samples ripened at 4℃for four months.This study included the following five aspects:1.Physical and chemical indicator of cheeseGross composition was determined in 3-day old cheeses,except for NaCl and pH,in which case 30-day old cheeses were analysed.No significant differences were observed in composition (fat,protein,moisture,salt content),but pH is significantly lower in experimental samples.2.The survival of bacteria during cheese ripeningThe viability of Lb.helveticus,starter lactic acid bacteria and non-starter lactic acid bacteria are detected during ripening period of 4 months at 4℃.The Lb.helveticus remained viable in Gouda cheese during the 4 months period,reaching 7.5 log₁₀cfug^-1 at the end of ripening.The viability of starter lactic acid bacteria is influenced by Lb.helvetieus.The viable numbers of Starter lactic acid decreased rapider in experimental samples during ripening.The viable counts of non-starter lactic acid bacteria had a falling trend during 4 months ripening.3.Assessment of proteolysisSN-pH4.6,SN-TCA,SN-PTA and SDS-PAGE in cheese samples are detected at intervals during ripening.No significant differences were observed in SN-pH4.6 and SDS-PAGE(P＞0.05), but SN-TCA and SN-PTA are significantly higher in experimental samples(P＜0.05),suggesting that the influence of Lb.helveticus on the primary proteolysis is neglectable,but its influence on the levels of secondary proteolysis is significant.4.ACE inhibitory activity during ripeningACE inhibitory activity of the cheese samples are analyzed at intervals during ripening.ACE inhibitory activity is significantly higher in experimental samples(P＜0.05),suggesting that the influence of Lb.helveticus on ACE inhibitory activity of cheese is significant.5.Sensory evaluationThe sensory evaluations of the cheese samples are performed at the end of ripening.The influence of Lb.helveticus on sensory attributes is significant.The acceptance scores of cheeses with the addition of Lb.helveticus were significantly different(P＜0.05) from the control,and the former received lower acceptance scores.Cheeses with the addition of Lb.helveticus received significantly higher scores for bitterness and sour-acid taste when compared with those without Lb. helveticus.In conclusion,Gouda cheese is an effective vehicle for delivery of Lb.helveticus.Addition of Lb.helveticus influence proteolytic patterns of cheese,and ACE inhibitory activity in cheese is inceased.