COMPARATIVE EVALUATION OF THE PRODUCTION PROCESSES AND QUALITY OF CHEESE FROM COWMILK AND SOYMILK

Abstract

Cheese (wara) is an excellent source of protein, fat and minerals such as calcium, iron and phosphorus thereby making it a good diet for both old and young people. This study evaluated and compared the potential of ginger extract with sodium benzoate on the microbiological quality, proximate composition, sensory evaluation and shelflife of cowmilk cheese and soymilk cheese stored at ambient (28±2oC) and refrigeration temperature (7±2oC). Three different coagulants namely alum, steeping corn water and sodom apple leaf were used and their effects on the milk coagulating time, cheese yield, whey volume and organoleptic properties of cheese were determined. Fresh cowmilk and soymilk were processed into cheese and preservatives were added at different concentrations and stored at ambient and refrigeration temperature and evaluated for 120 hours. Standard methods were used to carry out isolation, identification and analysis of sample which includes pH, total titratable acidity, proximate composition, effect of coagulants on the clotting time, curd yield, volume of whey and sensory evaluation. The cheese preserved with ginger had the lowest bacteria count of 0.10 x 103 cfu/g, the lowest fungal count was 0.10 x 103 cfu/g, while the control had the highest bacterial and fungal counts after 120 hours of storage (9.50 x 10 cfu/g and 4.20 x 103 cfu/g respectively). The isolates were characterized and identified as L. acidophilus, L. casei, L. brevis, L. bulgaricus, Lactococcus lactis, Micrococcus luteus, Staphylococcus aureus, Bacillus subtilis, Pseudomonas fluorescens. The fungi isolated includes Aspergillus niger, A. flavus, Mucor mucedo, M. racemosus, Penicillium sp. and Saccharomyces cerevisiae. Lactic acid bacteria occurred most, followed by Saccharomyces cerevisiae for fungi. The soymilk cheese showed a higher moisture content of 65.82% than cowmilk cheese which had 49.47%. The preserved cheeses showed no clear difference in chemical composition among the samples during fresh or storage period. Soymilk cheese preserved with ginger had the highest protein content (20.26%), while the cowmilk cheese had the lowest (17.95%). Also, cowmilk cheese preserved with ginger had the highest fat content (19.92%) while that of soymilk cheese was lower (6.50%). Physicochemical analysis of the samples showed a gradual drop in pH from 6.0 to 5.0 and an increase in total titratable acidity (TTA) from 0.068 to 0.219. Minerals were analyzed by atomic absorption spectrophotometer and showed that most of the minerals such as sodium, calcium, potassium, zinc were significantly higher at p≤0.05 in cowmilk cheese than soymilk cheese, but iron was higher in soymilk cheese. The average milk clotting time, cheese yield and whey volume ranged from 272 to 1088 secs, 115 to 217g/l and 370 to 750ml/l respectively. The coagulating time of cowmilk cheese was significantly shorter than that of soymilk cheese. The yield of cheese was significantly (p<0.05) higher among cowmilk cheese as compared to soymilk cheese. Soymilk cheese coagulated with sodom apple leaf was rated the best, followed by cowmilk cheese preserved with sodom apple leaf. The results indicated the efficacy of ginger and low temperature in the storage of cheese.