Study On The Changes Of Epidermal Growth Factor (EGF) Concentration In Goat Milk And Its Influencing Factors

Goat milk are rich in nutrients and have certain health-care function. Modern research has shown us that goat milk contain a variety of biologically active ingredients, in which epidermal growth factor (EGF) not only can promote the gastrointestinal growth and development in infants, but also have the efficacy of beauty in adults. So this study systematic researched the concentrations of EGF in goat milk and the factors that influence EGF levels in goat milk, providing the basis for developing goat milk functional products.This paper consists four parts concerning goat milk EGF:Part one:the investigation on variation of EGF concentration in goat milk, including the influence of breed, lactation, milking interval, lactation parity, lactation and lactation stage on the EGF concentrations. The results showed that EGF concentration is the highest in Guanzhong goat milk; The levels of EGF in goat's milk are highest in 30-90 days after delivery; Milking intervals had no significant effect on EGF concentrations; Goat milk yield is less, EGF concentration is higher; EGF concentration in second to fifth parities goat milk is higher; EGF concentration in colostrum was highest at first day and less in common milk. Therefore, in order to develop functional goat milk products that rich in EGF, we can collect lactation for 30-90 days, small daily milk yield,2-5 parities, Guanzhong goat milk samples.Part two:the effect of physical and chemical factors on the concentrations of EGF in goats'milk, including temperature, thawing, ultraviolet, pH and metal ions. The results showed that goat milk was treated by 20-100 ?, when the temperature is higher than 60 ?, the concentration of EGF decreased obviously; Ultraviolet radiation has a certain influence on the concentration of EGF in goat milk, when the treatment time is more than 30 min, the concentration of EGF in goat milk is significantly decreased; Thawing methods had no significant effect on EGF concentration in goat milk; Effect of pH on EGF concentration in goat milk is greatly, EGF is more stable in strong acid and neutral environment than near the isoelectric point of 4.6 and alkaline environment. The effect of metal ions on EGF concentration in goat milk related its species, Fe3+ could enhance EGF concentration in goat milk, there are different degrees of decreasing effect on goat milk EGF concentration by Na+?K?Ca2+?Zn2+? Cu2+?Mn2+?Mg2+?Al3+.Part three:the effect of processing methods on goat milk EGF concentration, including homogeneous,stirring, sterilization, fermentation and storage conditions. The results showed that homogeneous had no effect on goat milk EGF concentration; EGF concentrations increased and then decreased by low-speed strring, stirring at high speed goat milk EGF concentration decreased gradually; High-temperature short-time pasteurization (75?/15 s and 85?/10 s) had little effect on EGF concentration in goat milk, but low-temperature long-time pasteurization (63 ?/30 min) and ultra-high temperature sterilization (137?/2 s) significantly reduced goat milk EGF concentration; Fermentation process could also influence goat milk EGF concentrations, goat milk EGF concentration decreased rapidly during the fermentation time, but had no significant change during refrigerated storage. Storage conditions almost had no effect on EGF concentration both in EGF enhance goat milk and EGF enhance whole goat milk powder.Part four:the study of goat milk EGF in vitro gastrointestinal digestive stability. On the basis digestion stability study of goat milk EGF and EGF standard in artificial gastric, intestinal juice and artificial gastrointestinal, also studies goat milk composition and food borne protease inhibitors on the stability of EGF standard in artificial gastrointestinal fluid. The results showed that EGF concentration in goat milk decreased rapidly by digestion of artificial gastric, intestinal juice and artificial gastrointestinal within 1 h, which is basically stable after 1 h, but compared with the pure EGF, EGF digestion rate was significantly lower in goat milk; Whey and whey liquid had protective effect on the digestion of EGF in the artificial gastric juice while casein and whey protein had no protective effect, whey, whey liquid, casein and whey protein all had protective effect on the digestion of EGF in artificial intestinal juice; Goat milk-soluble fraction had protective effect on the digestion of EGF in artificial gastric juice while soya bean trypsin inhibitor, lima bean trypsin inhibitor and egg white trypsin inhibitor had no protective effect, soya bean trypsin inhibitor, lima bean trypsin inhibitor, egg white trypsin inhibitor and goat milk-soluble fraction all had protective effect on EGF in artificial intestinal juice.