Drying and storage of crude beta-galactosidase extracts from Lactobacillus delbrueckii ssp. bulgaricus 11842

摘要

The retention of beta-galactosidase activity in crude cellular extract (CCE) preparations from Lactohacillus delbrueckii subsp. bulgaricus ATCC 11842 was investigated after spray drying at three different outlet air temperatures (40, 50 or 60 deg C), freeze drying, and after 30 days storage. Lactose, skim milk and whey protein preparations in concentrations ranging from 5 to 30 percent (w/w) were used as drying adjuncts. To further investigate the protective role of sugars in the enzyme activity preservation, cellobiose and sucrose were also employed in 5 and 10 percent concentrations during spray-drying at 60 deg C or freeze-drying. The addition of lactose or skim milk in all examined concentrations resulted in significantly (P < 0.05) higher beta-galactosidase activity retention in comparison to all other CCE spray dried at 60 deg C. The effect was less pronounced at lower spray drying temperatures and increased whey protein concentrations, especially during freeze drying, when almost completerecovery of the enzyme activity upon reconstitution was achieved. Cellobiose provided less beta-gal protection in comparison to lactose or sucrose. Lactose was more effective than sucrose at 5 percent concentration, but both sugars were equal at 10 percent. The beta-gal activity retention in dry CCE preparations during storage at 7 deg C over 30 day period was related to the initial water activity; higher initial a_w of powders obtained at lower spray drying temperature was correlated with significant (P < 0.05) beta-gal activity loss. Freeze dried and spray dried (60 deg C) preparations were more stable in comparison to all other samples, retaining high beta-gal activity during storage up to 30 days.