Effect Of Milk Fat Globule Membrane Lipids On Milk System And Its Application In Modified Milk

Modified milk usually have fat floating during storage,which significantly affects consumers' desire to purchase.The fat floating of milk is closely related to the stability of milk fat globule membrane(MFGM),and the stability of MFGM depends on its structure and composition.MFGM lipids act as a skeleton of the outer lipid bilayer membrane structure composed of phospholipids and proteins,meanwhile,their changes also affect the stability of the milk system.MFGM lipids have the functions of enhancing memory,preventing senile dementia.This paper aims to study the effects of different processing conditions on the stability of MFGM lipids and milk system,and to screen the best processing parameters.On this basis,the effects of adding phospholipids on the milk system and the addition of MFGM lipids on the stability of the middle-aged and elderly modified milk systems are investigated to develop modified milk products,which are suitable for physiological characteristics of the middle-aged and elderly people.The heating method used in this study simulated the industrial production line,the primary sterilization(pasteurized milk)parameters was 75?/15 s and secondary sterilization(high temperature long-term sterilized milk)parameters was 121?/15 min.By measuring the turbiscan stability index(TSI)of the milk system?the absorbance ratio before and after centrifugation?the fat floating rate?the milk fat globule(MFG)particle size?the surface morphology of MFG observed by scanning electron microscopy(SEM)of the pasteurized milk and high temperature long-term sterilized milk,selecting 25 MPa was the optimal homogenization parameters.To explore the conditions for the qualitative analysis of lipids in MFGM by thin layer chromatography(TLC):Chosing chloroform:methanol:glacial acetic acid:acetone:water(35:25:4:14:2,v/v/v/v/v)as the developing agent A which was upward 5cm.Chosing n-hexane:diethyl ether(4:1,v/v)as the developing agent B which spreaded up to 1 cm from the top.The developer was 5%phosphomolybdic acid and the thin layer chromatography plate was baked at 121? for 15 min.Clear spots of cholesterol?PE?PC and PI were obtained,indicating that the above-mentioned lipids were contained in MFGM of pasteurized milk and high temperature long-term sterilized milk under this condition,which was provided a theoretical basis for quantitative analysis.High performance liquid chromatography(HPLC)was used to quantitatively analyze the changes of MFGM phospholipids in pasteurized milk and high temperature long-term sterilized milk under different homogenization pressures.In the range of 0 MPa?30 MPa,the total phospholipids content in MFGM was decreasing.But the content of total phospholipids in MFGM which the homogenization pressure was 25 MPa was more than 20 MPa.Using TSI as an indicator,the effects of phospholipids addition on the stability of pasteurized milk and high temperature long-term sterilized milk were investigated by single factor test and response surface test.Adding PC:1.4%,PE:0.2%,PI:0.09%,the pasteurized milk was the most stable.Adding PC:1.8%,PE:1.0%,PI:0.11%,the high temperature long-term sterilized milk was the most stable.Using TSI as an indicator,the effects of adding MFGM lipids,monoglycerides and sucrose esters on the stability of middle-aged and elderly modified milk were investigated by single factor test and response surface test.When the amount of MFGM lipid,monoglyceride and sucrose ester was 0.0100 g/100 mL,0.0500 g/100 mL,0.0700 g/100 mL,the middle-aged and elderly modified milk products have good stability and the shelf life was 170 days at 25?.