Tatik Khusniati

Immobilization of Lactobacillus plantarum B134 Cells using Sodium Alginate for Lactose Hydrolysis in UHT Milk

Hydrolysis of lactose in milk by β-galactosidase from immobilized bacterial cells has the potential to alleviate the problem of lactose intolerance. The present study was aimed to immobilize cells of L. plantarum strain B134 and evaluate their efficiency in hydrolyzing lactose in ultra high temperature (UHT) milk. Immobilized cells were generated by mixing cell suspensions with solutions of sodium alginate and calcium chloride. The β-galactosidase activity of the immobilized cells was tested by determining their ability in hydrolyzing lactose in UHT milk (whole milk and skimmed milk). Results showed that cells of L. plantarum strain B134 were entrapped optimally using a combination of 1 % sodium alginate, 100 mM calcium chloride and 12 % w/v cell suspension. The highest β-galactosidase activity was achieved at pH 6.5 and a temperature of 45 oC for 5 minutes incubation time. The immobilization efficiency achieved was 28.95 %. The immobilized cells could reduce lactose by up to 85.45 % in UHT whole milk and 91.26 % in UHT skimmed milk. The times required for that reduction of lactose in UHT whole milk and UHT skimmed milk were 12 hours and 9 hours respectively. The immobilized cells could be re-used up to 4 times for efficient lactose hydrolysis for both types of milk. Therefore, immobilized cells of L. plantarum B134 have the potential to be used for lactose hydrolysis in UHT milk.

The Organoleptic and Physic Characteristics and Lactic Acid Contents of Yoghurt with Commercial Starter Added Bifidobacteria bifidum

Bifi dobacteria bifi dum is probiotic bacteria which inhibit negative bacteria in human ulcer. Adding B. bifi dum in commercial yoghurt starter, may increase yoghurt quality. To know yoghurt quality, organoleptic and physic characteristics and lactic acid contents of yoghurt with commercial starter added B. bifi dum was observed. B. bifi dum concentrations added were 1:4, 2:4, 3:4 (v/v). Organoleptic characteristics were conducted by 18 panelists, physics were visually detected and lactic acid contents were by titration method. The results show that accepted yoghurt characteristics were yoghurt with commercial starter added B. bifi dum 1:4 (v/v), and fat yoghurt were more acceptable than that skim. The higher B. bifi dum concentrations used, the stronger fl avours (after expiry date) and colours (at and after expiry date) of yoghurt, while yoghurt homogenity decreased (at and after expiry date). Fat yoghurt fl avours were stronger than that of skim. The higher B. bifi dum concentrations and storage times, the higher yoghurt lactic acid contents. Lactic acid contents of fat yoghurt with various starters, were higher than that skim at storage 0-15 days. The fat yoghurt lactic acid contents were 0.99%-1.44%, while that skim were 0.95-1.20%. Based on organoleptic and physic characteristics and lactic acid contents, fat yoghurt were more acceptable that that skim.