Study On The Loss And Control Of Bioactive Proteins In Camel Milk Powder Processing

Camel milk contains a large number of bioactive proteins and enzymes,which have high nutritional value and potential medicinal properties for treating human diseases.Currently,there are still limited studies that trace the changes in bioactive proteins and their biological function with sequential unit operation during the industrial production of camel milk powder.Non-thermal pasteurization treatments cause less damage to protein structures and better preserve functional proteins and nutrients.The diameter of the casein micelles in camel milk is larger than that in bovine and goat milk,which makes camel milk different from other milk in terms of microfiltration.Therefore,it is of great importance to analyze the mechanisms and regularities of changes in bioactive proteins and physicochemical properties in the traditional unit operations of camel milk powder,and to develop non-thermal treatments as alternative processes.In this study,fresh camel milk was used as the study objective.The pasteurization treatment was selected as the key unit operation most severely affecting the bioactive proteins of camel milk using label-free techniques and quantitative techniques.The pasteurization stage was optimized by comparing the effects of non-thermal and thermal pasteurization on microbial removal,bioactive protein retention,and in vitro digestion.The main results of this study are as follows:(1)The effects of traditional camel milk unit operations on the protein profile,thermal stability and biological function of whey were studied busing label-free techniques.After pasteurization and concentration,the number of types and abundance of camel whey protein decreased more than that of standardization and spray drying.Bioactive proteins in highabundance proteins lay in an evolution branch that was less thermally stable than other branches.Sterilization and concentration had the largest number of differential proteins,and the main biological functions of down-regulated proteins included macrophage function,cell activity,immune regulation,and improving heart function.The GO analysis and gene function analysis of the missing proteins showed a decline in synthesis,antibacterial and other functions.The immune system,disease and signal transduction pathways were severely damaged.Pasteurization was chosen as the key unit operation affecting the bioactive protein content in the traditional unit operations of camel milk powder.(2)LC-MS/MS method,enzyme-linked immunoassay and other methods were used to detect the content of major whey protein,high abundance bioactive proteins such as lactoferrin(LF),immunoglobulin G(Ig G),lactoperoxidase(LPO),polyamine oxidase(PAO),and insulin(INS),and protein oxidation of camel milk in the traditional unit operations of camel milk powder.It was further verified that pasteurization was the key unit operation affecting the bioactive protein content in the traditional unit operations of camel milk powder.(3)Fresh camel milk was divided into skim milk and cream.Skim milk was treated by microfiltration,ultraviolet-c radiation(UVC)and pasteurization(HTST),and cream was treated by high temperature treatment.The results showed that microfiltration and UVC were able to achieve more bacterial and spore reduction than pasteurization.Compared with HTST,1.4 μm microfiltration and UVC retained more LF,Ig G and LPO.The retention of native whey protein by microfiltration was higher than that by HTST.Compared with 0.8 μm microfiltration,the membrane flux and permeability of protein was higher in 1.4 μm microfiltration.In the high temperature sterilization of mixed cream,125℃ 5 s could completely kill bacteria and spores,and lead to a low degree of protein and lipid oxidation.Results from in vitro static infant model digestion showed that microfiltered camel milk had a similar rate of digestion as raw milk.The method of first dividing the whole camel’s milk into skim and cream,and then mixing them after sterilization treatments,ensures the overall sterilization efficiency and improves the overall retention of the active components.In summary,the number of types and contents of active proteins decreased after pasteurization in the traditional unit operations of camel milk powder.Non-thermal pasteurization techniques such as microfiltration and ultraviolet were superior to pasteurization and retained more biologically active proteins in the milk.The major proteins in microfiltered milk had similar digestive properties to raw milk.The results of this study can provide a theoretical basis for the preparation of highly active camel milk powder.