QUALITY ANALYSIS OF FRESH CHEESE PREPARED USING PARTIALLY PURIFIED MILK CLOTTING PROTEASE FROM GINGER RHIZOME

Abstract

The aim of the present study was to extract, partially purify and utilize the proteolytic enzyme from ginger (Zingiber officinale) rhizome for making fresh cheese. The pulp of ginger rhizome was blended with 20mM sodium phosphate buffer (pH 7.0) in the ratio of 1:1(w/v) under cool condition and the extract was centrifuged at 5000 rpm for 10 min at 4℃. The partial purification of the crude extract was obtained by ammonium sulphate precipitation at the concentration of 30-80%. The optimum saturation was selected on the basis of milk clotting activity (MCA). The optimum temperature and pH of milk in the cheesemaking, for maximum MCA and minimum time of coagulation (TOC), were determined by response surface methodology using “Design Expert” software. The physicochemical and microbiological properties of prepared cheeses were compared with rennet cheese. Storage stability of the protease was also determined. The highest milk clotting activity was observed in the 50% ammonium sulfate precipitation. Numerical optimization study revealed that the optimum condition for milk clotting in cheesemaking was found to be at 55°C and pH 6.5. The optimized TOC and MCA were 28 s and 857.14 unit respectively. The sensory analysis showed that there were significant differences (P<0.05) in texture, spreadability, flavor and aftertaste except overall acceptance among rennet cheese and ginger protease coagulated cheese. The analysis of both cheeses revealed significant differences (P<0.05) in physico-chemical composition, and cheese yield. There was no significant difference (P>0.05) in yeast and mold count between the two cheeses, but there was a significantly higher level of total plate count in ginger protease coagulated cheese. Enzyme activity of protease was decreased gradually during 7 days storage at frozen condition