Research On Physical And Chemical Properties Of Laoshan Diary Goat Milk Entire Lactation Period And Heat Stability

In this paper, using Laoshan diary goat milk as material, the main nutritional components of goat milk within the entire lactation of goat was analyzed, including dry substance, ash, protein, fat, lactose and calcium. It was aimed to analyze objectively the nutritional value of goat milk and the relation between basic contents and lactation time. The research results were showed that the difference of lactation time of Laoshan diary goat was significant due to the individual differences among goats. And the composition of basic contents changed with the lactation prolonging while goat colostrums were more nourishing than ordinary milk. As lactation time increased, the dry substance content, protein content, fat content both decreased on different levels then remained stable during ordinary milk lactation period. The ash content of goat milk was tested to show0.8%to1%while declined with advancing lactation. Moreover, the content of lactose increased during early lactation then decreased with prolonging lactation. The result was also showed that the calcium content declined as lactation time went by. The calcium content of Laoshan diary goat milk was about0.8~1.2mg/100g. Besides, the ash content positively related to the calcium content by contrasting the data of ash content and calcium content. Last but not least, the result showed a significant difference among nutritional components content of goat milk of the first day after parturition, especially protein content and dry substance content. It might be related with the ewe’s individual health, calving number, age and other reasons.Secondly, analyzed the general physical and chemical properties of Laoshan diary goat milk and figured that goat milk was white and a little yellow which hold sweet tasting and goat flavor when it was heated. The result showed that pH of goat milk was close to neutral with titration acidity of11~23°T, and it positively correlated with lactation period. The clot-on boiling test proved that the thermal stability of colostrums was bad during early lactation while went better with advancing lactation. The alcohol coagulation test of goat milk was positive which indicated poor alcohol stability of colostrums.Finally, the general physicochemical properties of Laoshan diary goat milk were analyzed and the heat stability of goat milk was discussed. The effects of lactation period, heating temperature, pH and additives on the heat stability of goat milk were studied by analyzing the heat coagulation time (HCT) of the milk. The heat stability of goat milk enhanced along with the extension of lactation period and sharply reduced with the temperature increased. The influence of pH was enormous on heat stability, and HTC value was increased with pH increased. The solidification did not appear in the milk samples when pH＞6.5. Some additives such as citrate, phosphate and EDTA (0.01~0.20mol/L) were used to overcome destabilization and the higher concentration of additives, the greater improvement of heat stability. On the contrary, calcium content had a negative impact on heat stability of milk. In addition, the result showed a special relationship between heat stability and sucrose concentration. With the increasing of sucrose concentration, the heat stability of milk ascended first and then descended. The heat stability and HTC value exhibited the highest by addition of35%sucrose.