The Preliminary Study Of Application For Lactoperocidase System In Goat Milk And Prolong Of Shelf Life

There are so much advantage in goat milk such as affluent nutriment and good digestibility,it is also a kind of natural food which contains protein, amino acid, vitamin, mineral and so on. At the other side it also provides proper condition for reproduction of bacteria and microorganisms at common temperature, and resulted in deteriorating of goat milk and certain economical loss, otherwise, it could induce serious problem for food security. It has become the most influential step for development of goat milk. Therefore, it is crucial to develop a practical and economical method of preservation at common temperature for the goat milk storage and keeping fresh.The method of Lactoperocidase system(LPS) for milk preservation, it was easily operated and kept high efficiency of preservation under less cost without any refrigeration installation equipment and complex technology. It also has no side effect on human body. Now, this technology has been widely used to preserve raw milk quality in areas where it is not possible to use mechanical refrigeration for technical and/or economic reasons and made great point in practice, it was thought the most effective and safe way for preservation exclude freezing as far at present, and is very important for milk production. LPS is a natural anti-bacterial combination in milk, which is made up of LPO, SCNˉand H₂O₂. There were many reports about the effect of different concentrations of SCNˉand H₂O₂ could work well in bovine milk at present, but little report in the application of this system in goat milk domestically. At the other side, the method mentioned foreign couldn't be used directly for different breeds and condition of production. Because the difference of breed and metabolish between cattle and goat lead to great difference in milk component, the refreshing case suited for cattle is hardly work in goat milk.The objectivity of this study is to analyze find the reason why traditional LPS failed in preservation of goat milk, on which a method suit for preservation of goat milk is selected based. And it also provides reference for goat milk refreshing technology Aimed at investigating the activity and concentration of LPO, SCNˉand H₂O₂ from August to October, 8 multiparous Xinong Saanen goat were randomly selected for two factors random block experiment, and take enhancing the concentration of SCNˉ, the ratio of H₂O₂ and SCNˉas experimental factor. The effect on acidity of SCNˉ, the ratio of H₂O₂ and SCNˉworking on goat milk stored at 25℃for 24h, and then offer the reasonable additional proportion for goat milk preservation. The groups supplemented with preservatives in bovine and goat milk as control group compared with blank group, at the same time contrast the effect of sodium percarbonate and H₂O₂ for the preservation in goat milk at the aspect of the residual of preservation agent, the curve of acidity, standard plate count, and the loss of ascorbic acid to illustrate the effect of different programs on the quality milk.1. The analysis of difference for LPS related components. We found that enzyme activity of LPO is 1.88U/mL, the concentration of SCNˉis 1.57mg/L and H₂O₂ is 0.83mg/L after analysis of the components of LPS in goat milk between July and October. But other presentation indicated enzyme activity of LPO is 2.3-5.3U/mL, the concentration of SCNˉis 2-7mg/L which were higher than goat milk, and antibacterial ability show positive correlation with the enzyme activity of LPO. The potential reason for goat milk more easier rancid is enzyme activity of LPO relatively low.2. The analysis of refreshing effect for the dose used in bovine LPS applicated in raw goat milk. The result indicated that titrated acidity of goat milk is 36.8°T under 25℃after 24h storage when goat milk was stored with bovine criteria according to GB/T 15550-95, it can decrease the total number of bacteria to 0.63 log cfu/mL and prolong shelf time about 4h at least compared with control group. The potential reasons for traditional added dose failed preservation in goat milk is: first, the activity of LPO in goat milk is lower than bovine milk, resulted in needing a longer LPS reacting time to reach balance than bovine milk, and more H₂O₂ lost simultaneously, second, the content of SCNˉin goat milk is lower than bovine milk too. When added the dose for bovine milk, the concentration of SCNˉcan't reach to 15mg/L for the antibacterial effect, so it can't work in goat milk.3. Screening proper added dose and proportion for LPS application in goat milk. The result indicated the acidity of goat milk stored at 25℃for 24h get lower with the concentration of SCNˉenhancing in the range of 12.5mg/L to 16.5mg/L, through two factors random block experiment and multiple comparison. At the same time the acidity get lower first, then increased when the ratio of H₂O₂ and SCNˉvarying range 1 to 1.4. When SCNˉadded 13.5mg/L and the ratio of H₂O₂ and SCNˉreach to 1.1, the acidity of goat milk can get properly lower with the list dose. The titrated acidity is 25.9°T under 25℃after 24h,it can decrease the total number of bacteria to 1.21 log cfu/mL and prolong shelf time about 6h.4. When H₂O₂ alternated by Sodium percarbonate as the activator, it will enable more SCNˉparticipate in preservation, lead to improving the antibacterial effect of LPS extending the shelf life of goat milk, but with more ascorbic acid lost possibly. It can prolong the shelf life for about 8h when SCNˉadded 13.5mg/L and sodium percarbonate added 35.2mg/L.5. The analysis of security for LPS application in goat milk. The concentration of residual SCNˉmust less than 15mg/L according to national standard. The result indicated concentration of SCNˉdecreased to 10.51mg/L consistent with national standard, when LPS antistaling agent applied in goat milk about 2h, it is lower than that in baby's ptysma. It is much safer way to utilize LPS in extending the shelf life of goat milk. After application with LPS the concentration of SCNˉis about 15mg/L and H₂O₂ return to the normal level of regular milk within 2h in goat milk.