| Cream cheese is a kind of fresh soft cheese which mixed with cream and milk that can be consumpted immediately without waiting to ripe. It can be easily accepted by people with its soft taste, soft texture and rich nutrition, and it has the flavor both of the sour milk and butter. It is just because the rich nutrients and the soft texture that made it easy to be polluted by Listeria monocytogenes which is Monocyte hyperplasia bacteria. With the outbreaks of several disease related to cheese consumption that caused by Listeria monocytogenes and People’s respection to green food, the safety problem of cheese is getting more and more attention. So control the Listeria monocytogenes in the cheese with non-toxic and safe way has became the focus of the cheese safety problem.This experiment has studied the key processing technology parameters that includes the fat content of raw milk, sterilization temperature, the addition of rennimum and the cut length of clot, which influence the qualities of cream cheese and yield. Then do the optimization of response surface methodology on the single factor study, optimize the processing technic of cream cheese and make sure that it has the high productivity, the high sensory evaluation and be loved by the consumers and so on. It also do some analysis of the control function application of the bacteria produced by two strains of Enterococcus faecalis that KLDS6.0610and KLDS6.0611in the Laboratory of dairy.The experimental results show that:The real yield of the cream cheese is increasing with the increasing of fat content’s and the water content, protein content will reduce. The recovery of protein, solids reaches the highest when the fat content of raw milk gets12%. With the thermal death points’s increasing and cream cheese shows the growing trend. The cream cheese that produces under63℃,30min and serialization conditions can taste smooth, dense ester aroma and be more popular. The cream cheese that produces under75℃,15s and serialization conditions has high grade and even has excellent texture but the taste is little worse. The cream cheese that produces under92℃,15s and serialization conditions has higher sense grade. It contains more water, relatively soft texture and gritty-textured. Firstly, the yield of cream cheese increases and then decease afterwards with the rennin’s increasing, it gets the highest under30mg/L condition. With the rennin increasing, the content of whey decease firstly and then increases afterwards, it gets the lowest under30mg/L condition. With the increase of the size of the clot cut, cheese yield increases, clot in protein content decreased, whey protein, solids content and moisture content are increased.Through the surface response experiment, the fat quantity in the raw milk,the rennet amount and the clot cud size effect to cream cheese’product yield and sensory evaluation can be revealed within the experimental range. The experimental results show that when there are12.03%fat in the raw milk and the clot cutting edge length is15mm, and rennet amount is28.8mg/L, the cream cheese yield is the highest that predicted of34.91%. It also show that when fat quantity in raw milk is11.54%, clot cutting edge length is10.46mm and the rennet amount is29.12mg/L, the model prediction of the cream cheese has the highest sensory score with14.21%.Both the two strains of Enterococcus facials can produce bacteriocins in MRS medium when cultured under37℃. The KLDS6.0610reaches the highest yield after inoculated20h, and the KLDS6.0611reaches the highest yield after inoculated16h. Though testing the moisture quantity and protein quantity of the sample of the cheese within the storage period, we know that the water quantity in all the sample is about53%which can achieve the USA Department of agriculture’ request on cream cheese. When the samples are kept for5days in4℃, the living bacteria number in the cheese sample that add with bacteriocins and bacteriocin-producing bacteria is less than in the control group. And the L. monocytogenes amounts in the sample that only add with baceriocins is less than that only add with bacteriocin-producing bacteria. And the cream cheese adds with two bacteria is less than only add with one bacterium. If the40AU/ml bacteriocins is put into the cream cheese, the L. monocytogenes can be delayed growing for9days at4℃. At this time, the amount of bacteria can be decreased on3.98×105... |
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