Accelerated Ripening Of Cheddar Cheese With Lactobacillus Plantarum Selected By Genome Shuffling

Adjunct culture belong to cheese exogenous microorganisms,and adjunct culture is a uniqueflora in cheese,adjunct cultures can accelerate cheese ripening and improve development of cheesesensory quality. Genome shuffling based on cross mating was used to improve the aminopeptidaseactivity and autolytic activity of Lactobacillus plantarum,and low acid was assessed as adjuncts inCheddar cheese.The formation and regeneration of protoplasts were studied.We studied Cheddarcheese slurry proteolysis of the isolates compared with Lb. plantarum KLDS1.0351duringripening.And eventually they were applied to cheese, and discussed about the influence ofaccelerating cheese ripening.The purpose of the study is to screening out adjunct culture by genome shuffling. Whenbacteria were cultured with1.2%glycine in advance and training time is4h is optimumcondition,the best time of protoplasm body heat inactivated is90min, the best time of protoplasmuv inactivated is30min.First lactobacillus plantarum was mutagenesis by UV and NTG,fivepopulations of high Aminopeptidase activity were obtained. Parental protoplasts were inactivatedand fused by polythyiene glycol6000. The fusants grew at the RM plates were the shuffledstrains.The results of switching over generation four show that they were genetic stability,producing3.09times as content of Lactobacillus plantarum A-1.Autolysis68.42%degrees,producing4.04times as content of Lactobacillus plantarum A-1. Thus the strain F-4wasscreened for the test strain. The research on biology characteristic of strain F-4showed it can growin MRS broth which contained pH4to6and NaCl concentration of3%to9%, the strain F-4couldtolerate low temperature environment too.Cheese slurry was made aseptically using fresh cheese curd was used to rapidly evaluatedeffect of strain F-4on cheese ripening. pH4.6WSN and12%TCA-SN as the proteolysis index wereregarded as ripening index.Samples were collected at0,2,4,6,8,10d in cheese ripening.The value ofpH4.6WSN in cheese slurry indicated F-4had no influence on casein primary proteolysis. Thevalue of12%TCA-N in experimental cheese was higher than other groups of cheese, The resultsshowed that strain F-4accelerated the hydrolysis of proteins in the cheese system, and promotedcheese mature process.Cheddar cheeses were manufactured in open vats to study the influence of adjunct culture oflactobacillus F-4on proteolysis during ripening. Non-protein nitrogen of four weeks old Cheddar cheeses treated with F-4strain was equal to control group matured eight weeks, their sensorycharacteristics were preserved or improved, and they did not show any defects. Above all, thegenome shuffling is a useful method to treat with adjunct cultures in cheese ripening.