Feasibility Of An Authenticating Special Livestock Milk Based On Species Specificity Of IgG

Special livestock milk is highly favored by consumers because of its peculiar taste,nourishing and certain functionalities.However because of its low yield,high price,it is very vulnerable to adulterated by low price cow milk.To date,there still lacks mature methods or test kits to discriminate the authenticity of special livestock milk.Immunoglobulin G(IgG)is a major immune molecular protein,which widely exists in tissue fluid and other body fluids,while the content in milk is relatively stable with species specificity.The purpose of the study was aiming IgG of cow milk as target/marker protein to establish authentication method to identify cow milk that adulterated in horse and camel milk.Firstly,the IgG content of 64 samples of cow milk was determined by single immunodiffusion assay.The range of its contents was estimated and its stability in a week of was also evaluated.Furthermore,the cross reaction titer of rabbit anti bovine IgG serum with horse milk and camel milk was detected by double immunodiffusion assay,while the strategy to avoid cross reactivity and theoretical detection limit of adulteration were also studied.Moreover,the detection limit and robustness of adulterated special livestock milk were evaluated based on by double immunodiffusion assay with preparation of adulterated samples in different proportions.The results showed that the average content of IgG in mature bovine milk was0.626±0.147mg/m L.while the maximum and minimum contents were 1.08mg/m L and 0.31mg/m L respectively.There was no significant change of the content within 7days at 4℃,indicating that it was also suitable as target protein to conduct adulteration detection experiment for its property of keeping stability in mature bovine milk.The rabbit anti-bovine IgG serum had cross-reaction with horse milk and camel milk in dilution below 2~3and the cross-reaction could be avoided when the dilution was up to 2~4.The theoretical detection limit of adulteration was 2%.Adulterated samples were prepared by mixing cow milk at 1%,2%,5%,10%,20%and 50%with horse milk and camel milk respectively to evaluate the adulteration detection limit by double immunodiffusion assay.Results suggested that the detection limits of adulterated samples were 2%,which was in line with expectations.Actually,considerable illegal profits would be obtained when the adulteration was 5%～10%or higher.Therefore,the method can fully meet the identification requirements of special livestock milk with strong stability and reliability.In summary,it is a sensitive,convenient and cheap way to identify special livestock milk for the usage of the agarose gel immunodiffusion test by using of IgG as target protein.Meanwhile,the results indicated that IgG can be the target protein for establishing more sensitive and accurate immunolabeling assays to identify adulteration of special livestock milk.