Abstract:
The main objective of this work was to compare the effect of extraction methods
(ammonium sulphate, acetone and acetone TCA precipitation) on protease yield from
starfruit of different maturity stages (unripe, semiripe and ripe). Proteolytic activity (PA)
and protein were measured spectrophotommetrically. Optimum hydrolysis condition:
temperature and pH of protease for maximum proteolytic activity was determined by
response surface methodology. Protease were incubated for 12 h in different buffers in the
pH range of 3.5 to 8.5 before the determination of proteolytic activity. In order to determine
the effect of temperature, the protease was incubated at different temperatures in the range
of 40 to 90°C. Storage stability of the proteases were also determined for one week storage
period at <4°C.
Higher yield and proteolytic activity were observed for protease using ammonium sulfate
(40%) than acetone and acetone with TCA precipitations. As for maturity stages, PA and
protein concentration yield from unripe stage were significantly (p<0.05) higher than those
of semi ripe and ripe. Numerical optimization study revealed that the optimum temperature
and pH for proteolytic activity were 65°C and 6.5 respectively. The optimized proteolytic
activity was found to be 0.862±0.05 units/ml. Enzyme activity was significantly decreased
during 7 days storage period at <4°C. This study suggested that ammonium sulfate
precipitation is effective method for extraction of starfruit protease compared to acetone and
acetone with TCA precipitations. In order to obtain higher protease activity, unripe starfruit
will be better raw material for protease production.
Description:
A dissertation submitted to the Department of Food Technology, Central Campus
of Technology, Tribhuvan University, in partial fulfillment of the requirements
for the degree of B.Tech in Food Technology
