Establishment Of The Protein Risk Index System Of Milk And Dairy Procucts

Currently, adulterate pHenomenon of milk protein is more and more serious, an effective method used to solve this problem is necessary. This paper established a system for preventing the adulteration of dairy protein to control the quality and safety of milk and dairy products.The protein adulterant in milk and dairy products is mainly divided into two categories, acid soluble nitrogenous substance and acid sinking of nitrogenous substance. So, firstly, through determining the content of nonprotein nitrogen, we can get whether there is adulteration of acid soluble nitrogenous substance in milk protein.chosing the precipitation agent and its optimal dosage,and then chose the 15% trichloramine acetic acid as the agent for protein precipitation, through the determination of nitrogen content in the supernatant, and compared with normal to judge whether the samples are of adulteration. add various exogenous nitrogenous substance, such as isolated soy protein, urea, protein hydrolysate, soybean peptide, glycine and so on to get the recovery from 82% to 112%,and good reproducibility.The result of nitrogen content in whole milk powder is from 4% to 7%,and 5-15% in infant formula milk.Secondly, we use casein as the basis for solve the adulteration by acid sinking of nitrogenous substance. This paper use the result of pHospHorus content in casein of milk and dairy products for the first time to judge whether the dairy adulterated by acid sinking of nitrogenous substance. We add trichloramine acetic acid into the dairy products, collect the precipitate and digest it,and then using molybdopHospHoric blue method to determine the pHospHorus content. Throuth using orthogonal test, we get the optimal digestion conditions:sulfuric acid 10 mL,digestive 60 min, and after its temperature down slightly, add hydrogen peroxide 10 mL. The recovery rate from 90.75% to 107.44% This method measured the full-cream milk casein content of 76%～83%; casein content of the samples added in melamine are 42.8%,54.5% and 64.8%, and casein content of the samples added in soybean protein isolated are 56.6%,47.3% and 62.6%, the casein content of the sample is 78.9%, experimental results show that the method can be used for determined the sample adulterated by acid precipitated nitrogenous substance. Add in melamine and water-soluble wheat protein and the proportion of nitrogen are 0%, 20%,40%,60%,80%,100%, then we get the adulterate dairy products. And the results of applied experiments show that,the casein contents of adulterate dairy products add in melamine are 24.50%,19.44%,14.45%,9.555%,4.889%,0.0632%, and add in wheat protein's are 24.50%,19.43%,14.05%,9.122%,4.894%,0.2059%. the result show that the more exogenous nitrogenous substance added, the lower the content of casein is, therefore, the content of pHospHorus of casein as the index can effectively prevent the adulteration of dairy protein.Many kinds of raw milk are determined, and the result of casein content are in 76%-83%, close to 80%. and the results of other dairy products are also in the The normal range.If the first two basis cannot solve the problems, such as adulterate the acid soluble nitrogenous substance whose nitrogen content equivalent with supernatant's and adulterate acid precipitated nitrogenous substance whose nitrogen content equivalent with precipitation and adulterate pHospHorylated exogenous proteins, we chose the determination of amino acid content, containing 18 kinds of amino acid content, and calculate to get the milk protein approximate content, and establish the amino acid pattern to prevent the protein adulteration. Experimental results show that the total content of amino acid are close to the protein's.The total content of amino acid of infants formula powder are 12.06 g/100 g to 15.1 g/100g, following-up infants formula powder's are 13.89 g/100g～20.51 g/100g, and the growing-up infant formula powder's are 18.32 g/100g-21.13 g/100g; total content of amino acid of raw material powder and whey protein are close to the theoretical content of protein. and it can prevent the adulteration of dairy effectively. The contents of all amino acids of milk and dairy products are in a certain range. the content of Serine, cystine, tryptopHan change in a wider rang in the infant formula powder, the contents of threonine, proline and cystine change greatly in following-up infants formula powder, in the growing-up infants formula powder are proline, cystine, and alanine, pHenylalanine and tyrosine in raw milk powder; all amino acids content in whey powder are relatively close. Therefore, establishing the amino acid anti-fakes model can solve the problem of protein adulteration effectively. Therefore, this paper utilized the determination of nonprotein nitrogen content to prevent the adulteration of acid soluble nitrogenous substance. Accoroding to the pHospHorus content of casein we can prevent the adulteration of acid precipitated nitrogenous substance, and the amino acid pattern can solve all problem, so we get the comprehensive system to prevent the adulteration of protein.