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Extraction, Purification and Characterization of Apricot Seed β-Galactosidase for Producing Free Lactose Cheese

HebaEzz el Din Yossef and Alaa El Dein El Beltagey

β-Galactosidase was extracted (with acetate buffer pH 5) from apricot seeds, partially purified by ammonium sulphate (30-70%) and dialyzed for 24 hr. The crude extract had a higher specific activity (9.93 U/mg proteins) which indicates a high enzyme yield. Purification of crude extract with ammonium sulphate (30-70%) increased the specific activity and purification fold to 29.07 U/mg proteins and 2.92, respectively which was improved by dialysis to 32.68 U/mg proteins and 3.29, respectively. The extracted enzyme exhibits an optimum temperature at 70°C and 5 pH optima. The enzyme activity was almost stable between pH 5.0 and 6.5, where more than 90% of its activity was remained with incubation at the previous pH for 30 min. Further more; it was thermostable when incubated for 30 min. at temperature ranges of 55-70°C with a complete loss of activity at 80°C. The activity of β-galactosidase was enhanced by different concentration of Ca+2. There were no significant (P>0.05) changes in flavor, body texture, and overall acceptability between free lactose white cheese treated by apricot seeds β –galactosidase (9865 U/ 500 ml milk) and untreated cheese.