Study On Critical Procedures Of Cottage Cheese Processing

Cottage cheese is a soft unripened, mildly acid cheese, made from skim milk. The cottage cheese should be easily accepted by consumers in our country. This paper studied the main factors affecting cottage cheese quality, focused on the selection of starter LAB, impact on compositional, textural properties and yield of cottage cheese curd due to process conditions, optimization of critical technologic parameters, formulation of cottage cheese dressing, etc.One preferable bacterium, which was preliminarily identified as Lactococcus lactis ssp. cremoris CH₅, was selected from 20 bacteria by a series of experiments including fermentation, and proteolysis.The results of one factor experiment showed that: with increase of total solids in skim milk, percentage of total solids in curd and curd yield increased, but yield efficiency of the cheese decreased; the higher total solids in skim milk had an adverse impact on appearnce of cheese curd. The firmness of curd increased significantly(p<0.05)with increase of cutting pH; when cutting at pH 4.6, the yield of curd reached the highest, the amount of protein and total solids lost in whey were the least. The percent total solids and firmnesss of curd increased significantly (p<0.01) with increase of heating temperature; heating rate had an influence on curd microstructure, with increasee of heating rate, the extent of protein matix contraction increased, the pore-size became smaller.Crucial process parameters of cottage cheese, which were cutting pH (4.6), heating rate (0.5 ℃/min), cooking out temperature (63℃), were optimized by using three factors quadratic design. Cooking out temperature had a significant (p<0.01) influence on yield and firmness of curd, the effect of cutting pH is smallest. There was interaction between cutting pH and heating rate for total solids in curd.At the same time, the formulation and process for dressing manufacture was studied. The results showed that: the addition amount of stabilizer had the highest influence on dressing viscosity and retention amount by cottage cheese curd, the fat content of dressing was one of the main factors which affected the retention of dressing by curd. Combined with the sensory evaluation scores, the optimum formulation of creaming dressing was: stabilizer addition 0.35%, salt addition 3%, pH6.5, and the fat content 13%.