Study On The Properties Of Caprine Milk And Its Proliferation Fermentation Efficiency For Lactobacillus Acidophilus

The high valuable nutrient of bovine and caprine milk is spoken highly of based on plenty of fundamental researches. Yet the further exploration will be continued due to the discrepancies existing between the properties of the nutrients of the bovine and caprines'milk and the features of the processing, especially the study on the nutritious caprine milk merits and its application in Lactobacillus acidophilus (L.A.) are still vacant. There are a great abundance of caprine milk resources in Shaanxi province. The quantities of heads and the productivities of caprine milk have ranked priority domestically. The formed economic specialties have been ranked steadily and continuously. The main producing areas of caprine milk distribute in places like FuPing, LanTian, QianYang, SanYuan, JingYang and YangLing and so on. And the species of caprines are chiefly ShaNeng and GuanZhong caprines. However, the remaining preliminary level of processing in Shaanxi resulted in typical deficiency utilization by advantageous resources; more than 90% of the processed milk powder is exported to domestic and abroad too. To seek the new methods and advanced spirits taking use of the caprine milk, to realize the perfect combination between the effects of caprine milk nutrients and maximum economic profits, it's highly necessary to make a comparative analysis of caprine milk and cow milk, coming with the deeper research on fermentation efficiency for Lactobacillus acidophilus. The precious conclusion and inspiration is concluded from the relatively comparisons between caprine milk and cow milk on different characteristics of nourishment, textural properties, processes, flavor and microbiology fermentation. It provides the latest referent for the scientific utilization of the caprine resources in Shaanxi. The primary conclusions are the following:1. The quality of caprine milk is quite stable in Shaanxi; there is a slight wave of nutrient compositions among the provincial yearly standards. The main physiochemical items resulted as follows: density( D2 40,20℃/4℃)1.0282±0.0019×103kg·m-3, pH 6.694±0.018, titratable acidity 11.86±0.203°T, crude protein 31.92±1.96 g·L-1, lipid 38.94±0.97 g·L-1, lactose 43.54±6.58 g·L-1,mineral content 7.655±0.388 g·L-1, total solids(TS)123.96±2.16 g·L-1, non-fat solids(NFS)84.63±2.77 g·L-1.The yearly varies of nutrient compositions, with the exception of lactose; abide by the regulation as follows: The content of nutrition items is higher in spring and winter, it's lower in summer and autumn, and it remains the lowest in July and August. Yet as for lactose, the regularity is just opposite. The physical items of caprine milk are as follows: viscosity (η)1.37±0.16 mPa?s(20℃),electrode conductivity(K) 4.715±0.25 mS/m(20℃), the surface tension (P)50.370±4.096 mN/m(20℃), the refraction index (nD)1.3462±0.0014(20℃). The physical properties of caprine and cow milk is no significance (P>0.05).2. The textural properties of caprine set yoghurt are as follows: firmness 108.73±4.15g, consistency 2139.31±90.88g·s, cohesiveness 43.70±8.79g, index of viscosity 34.89±14.42 g·s. Compared to the bovine set yoghurt, the firmness and index of viscosity exist significance (P<0.05). The textural properties of caprine stirred yoghurt are as follows: firmness 93.42±9.85g, consistency 691.58±110.10g·s, cohesiveness 35.15±5.83g, index of viscosity 20.79±10.10g·s. Compared to the bovine stirred yoghurt, the index of viscosity exist significance (P<0.05). The textural properties of caprine cheese are as follows: hardness 2269.28±246.97g, Stickiness 214.95±31.33g. Compared to bovine cheese, the hardness and stickness exist significance(P<0.05).3. before homogenizing, the particles of fat globule of bovine and caprine revealed in various sizes. The diameter range of caprine fats globule is within 0.183~8.544μm,the average diameter is 2.6580μm;The diameter range of bovine fats globule is within 0.277~9.552μm, the average diameter is 3.4573μm. The particles of fat globule of caprines and bovines conforms normal distribution. The caprylic acid and the capric acid are the characteristics fatty acids of caprine. The sum of contents is 11.60%. After processing, the contents of the long chain of saturated fatty acids are decreased, but the contents of the short chain of saturated fatty acids are increased. The nutrition valve will be upgraded after it's processed. And the supplement of the short chain of fat acids is easier for Human body to digest and absorb. The contents of unsaturated fat acids in colostrums of caprines'and cows'reach as high as 36.91% and 33.06% respectively. The ratio of SFA:MUFA:PUFA of bovine colostrums, caprine cheese and caprine colostrums are 5.58:2.86:1 , 9.20:3.77:1 and 9.34:3.93:1 comparatively. Their nutrition values are relatively higher than other analyzed dairy products. The colostrums both bovine and caprine are ideally healthy food resources.4. Under the synthetic analysis of amino acid nutrition evaluation items, proved by the ratio of TEAA/TAA,AAS,RC,SRC,EAAI, the quality of caprine proteins are superior to that of the bovine's, but it will be inferior to the bovine's after it's heated. However after fermented by the microorganism, the quality of caprine proteins will be better than that of the bovine's. The poor performance of heat-resistance of caprine milk is more adapted to be produced as fermented dairy. The nutrition evaluation results of bovine milk and their products in turns are: bovine yoghurt, bovine cheese, pasteurized milk, UHT milk and pure bovine milk. And that of the caprine milk series are caprine cheese, pure caprine milk, caprine yoghurt, pasteurized caprine milk and UHT caprine milk.5. There is a complexity in flavor substances of bovine and caprine milk and their products. They are rich in carboxylic acids, alcohols and furans, aldehydes, ketones, esters, hydrocarbons and others. The result of the flavor compounds of bovine and caprine and their products shows that there are 52 kinds in bovine milk, 53 in caprine milk, 52 in pasteurized bovine milk, 53 in pasteurized caprine milk, 53 in UHT caprine milk, 54 in UHT bovine milk, 53in UHP bovine milk, 50 in UHP caprine milk, 52 in bovine yoghurt, 53 in caprine yoghurt, 53 in bovine cheese, 52 in caprine cheese. There is a basic similarity between the constituents of flavor substances of bovine and caprine milk and their products. The contents of flavor constituents and their distribution ability have a slight difference. Each of the flavors runs a different feature.6. The optimized ingredients, of enriched incubating of L.A. in caprine substrate, is: 1.0% fructo-oligosaccharides (FOS), 1.2% whey, 5.0% carrot juice, 2.0% honey, 1.0% inulin, 1.0% lactose, 1.0% casein phosphopeptide(CCP), The important order comes by whey, FOS, honey, CPP, inulin, lactose and carrot juice. The highest living counts in caprine milk substrate reaches to 9.955×1011 Cfu·mL-1. The optimized ingredients, of enriched incubating of L.A. in bovine substrate medium, is FOS 1.5%, 1.8% whey, 7.5% carrot juice, 2.0% honey,1.5% inulin, 1.0% lactose, and 1.0% CPP. The important order comes by CCP, FOS, inulin, honey, whey, carrot juice and lactose. The highest living counts in bovine substrate reaches to 9.875×1011 Cfu·mL-1. The living counts of the freeze-dried L.A. powder of these two sorts of dairy substrate media reach to the grade of 1012 Cfu·g-17. The optimum formula of protectants in caprine milk substrate is: with the addition of 4.0% glycerin, 0.30% L-cysteine, 0.75% ascorbic acid, 1.0% trehalose, it affects the same result as in bovine substrate. The important order follows by ascorbic acid, glycerin, trehalose, L-cysteine. The verifying test shows the survival rate of L.A. powder reaches to 85.55% and living counts reach to 8.877×1012 Cfu·g-1 after adding optimized protectants.The optimum formula of protectants in bovine milk substrate are: with the addition of 4.0% glycerin, 0.30% L-cysteine, 0.75% ascorbic acid, 3.0% trehalose, effects best in making bacterial suspension. It protects L.A. cells more efficiently; decrease the hurt from freezing, the survival rate of L. A. is the highest. The important order follows by ascorbic acid, trehalose, glycerin, L-cysteine. The verifying test shows the survival rate of L.A. powder reaches to 85.60% and living counts reach to 7.283×1012 Cfu·g-1 after adding optimized protectants. 8. The regression model of the L.A. augment fermentation in MRS medium is YMRS(t)= 3.45888/(1+12.92378*exp(-0.35632*t)), the determination coefficient is DC=0.9934,the relative index is R=0.9967, there is significance(P<0.01). The regression model of LA in caprine substrate is YCAP(t)=33.2056/(1+0.437297* exp(-0.080136*t)) DC=0.9981, R=0.9989, P<0.01;The regression model of LA in bovine substrate is YB0V(t) = 33.5013/ (1+0.442989*exp(-0.075401*t)), DC=0.9919, R=0.9959, P<0.01.