Abstract:
The aim of the present study was to extract, partially purify and utilize the proteolytic
enzyme from kiwi fruit (Actinidia deliciosa) for making soft cheese. The pulp of kiwi fruits
was blended with sodium phosphate buffer (pH 7.0) in the ratio of 1:1 and the juice obtained
was centrifuged at 4000 rpm for 10 min under cool condition (4°C). The partial purification
of the suspended (crude extract) was obtained by ammonium sulphate precipitation at the
saturation of 30, 40, 50, 60, 70 and 80%. The optimum saturation was selected on the basis
of milk clotting activity (MCA). Optimum conditions of temperature and pH of milk for
maximum MCA and minimum time of coagulation (TOC) were determined by response
surface methodology. Milk clotting activity (MCA), proteolytic activity (PA) and protein
content of the extracted protease were measured. The partially purified protease was used as
milk coagulant in soft cheese preparation at optimized conditions. The physicochemical and
microbiological properties of prepared cheeses were compared with rennet cheese.
Out of the fractions obtained by precipitation, the highest milk clotting activity was
observed in the 50% fraction. Numerical optimization study revealed that the optimum
condition for milk clotting was found to be at 55°C at pH 6.5. The optimized TOC and MCA
for partially purified kiwi protease was found to be 30 s and 841.65 unit. The cheese
manufactured by kiwi protease showed similar textural properties and physico-chemical
compositions to rennet cheese. The physico-chemical analysis showed non-significant
(P>0.05) difference in protein content between soft cheeses prepared by kiwi protease and
rennet. However, significantly (P<0.05) higher level of moisture, ash content, acidity and
calcium content, and lower level of fat were observed in kiwi protease cheese as compared
to rennet cheese. Microbiological analysis revealed significantly (P<0.05) higher level of
total plate count in kiwi cheese. There was no significant difference (P>0.05) in yeast and
mold count between kiwi protease and rennet cheeses
Description:
A dissertation submitted to the Department of Food Technology, Central Campus of
technology, Tribhuvan University, in partial fulfilment of the requirements for the
degree of B. Tech. in Food Technology
