Study on optimal biotechnological parameters of cells immobilization in yoghurt ferment on modified gelatin

Abstract

. The big demand for sour milk products, including yoghurt, requires use of raw materials of good quality. However, the factors in milk that have negative effect on microorganisms in yoghurt ferment, need application of biotechnological methods for their immobilization. For the study a modified gelatin was used, on which various doses of yoghurt ferment were immobilized (from 5 mg to 100 mg) being dissolved in different dissolvent volumes (0.2 cm 3 , 0.3 cm 3 and 0.4 cm 3 ) of distilled water. The carrier’s mass remained constant: 1000 mg. The fresh preparations were immediately dried out by means of active ventilation and mixing. The humidity content in immobilized ferments was investigated after 15 min of drying as well as the time of drying out for reaching the humidity level of 7–9%. It was experimentally found out that the humidity of the yoghurt ferment immobilized on modified gelatin (with application of 0,2 cm 3 dissolvent) was about 11.5–12.6% after 15 min drying. The humidity of the ferments immobilized by 0.3 and 0.4 cm 3 distilled water after 15 min drying was correspondingly 17.2% – 18.3% and 22.4% – 24.8%. The increase of distilled water volume for dissolving different doses of ferment resulted, after 15 min drying, into increase of humidity in the preparations accordingly up to 22.4% – 24.8% of the total mass. During works on the immobilization technology of microorganisms’ cells in yoghurt ferment on modified gelatin, it was found that the quickest drying of preparations (32.4–37.2 min) occurred with application of 0.2 cm 3 dissolvent per 1 g of carrier. The augmentation of dissolvent volume to 0.3 cm 3 resulted into increase of drying time up to 43.5–54.2 min. The drying of immobilized ferment samples to the humidity level of 7–9% with application of 0.4 cm3 distilled water lasted more than one hour. It was proved that the more ferment mass was immobilized on modified gelatin, the more was the drying time of preparations. Therefore, from technological point of view, the dissolving of 5–100 mg of yoghurt ferment in 0.2 cm 3 distilled water is optimal.