Research Of Bioactive Galacto-oligosaccharides Rich Milk

Optimization of galacto-oligosaccharide (GOS) rich milk conditions using Biolactase L was studied in this paper, and the kinetic analysis of enzymatic reaction as well as the analysis of physicochemical indexes and sensory properties of the GOS rich milk were also included.The composition and content of sugars were analyzed by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The preparation conditions such as reaction time were studied in the range from 20 min to 60 min; the reaction temperatures were studied in the range from 30℃to 50℃; and Biolactase L added were from 0.01% (w/w) to 0.03% (w/w). When the GOS conversion rate reached to the highest level, about 17%, the optimal GOS production conditions was as follows: 0.015% (w/w) biolactase L was added into cow milk and cultured at 40℃for 40 min. The interaction between three parameters had no significant impact on the GOS conversion rate. From the result of oNPG method, the activity ofβ-galactosidase before UHT was 4200U/g, while it has no significant difference from the negative control after UHT. The maximum reaction rate of Biolactase L Vmax was 0.267μmol/min, and the Michaelis constant Km was 1.45 mmol/L.From the results of physiochemical indexes , the fat in the GOS milk was 0.10%, the protein was 3.26%, the non-fat milk solids was 8.68%, and the lactose was 4.42%. All the amount of ingredients were in compliance with national standards of sterilized milk product (GB 5408.2—1999). Acidity in GOS milk after UHT was 15.3°T and there was no any bacterica, which has met the national standards of sterilized milk product. The color of GOS milk is light yellow with homogeneous appearance. Its brightness and red-green chromatic aberration were significant different from the raw milk (p<0.05), and the total color and yellow-blue chromatic aberration were extremely significant different from the raw milk (p<0.01). From the basic sensory evaluation results, there was no significant difference between the GOS milk and the raw milk in taste, smelling and texture, while the color and sweetness were significantly different (p<0.01). However, the GOS content and conversion rates in the bioactive milk were significantly different (p <0.01) before and after UHT, which means that industrial production need to consider the other final sterilization treatment.