The Research Of Milk Protein-lactose Model System Variation In A Microwave Field

Milk (milk powder) is a kind of universal nutrients, which is important to humanhealth and the growth of baby. Microwave is often used for sterilization of milkpowder and the reheating of milk, Maillard reaction affect the safety and nutritionalquality of milk (milk powder), which is easily occured during the process of milk(milk powder) treated by microwave. Maillard reaction occurs mainly in milk (milkpowder) between the main components of casein, whey protein and lactose. Due tothe complex composition of milk (milk powder) and in order to simplify the reactionsystem. Then casein, whey protein and lactose were adapted as raw materials to buildthe model according to the composition of milk and milk powder. These research wasfocus on the functional properties, physiological activity during digestion andstructure characteristics of casein-lactose model system after microwave treatment.The main research contents and conclusions are as follows:(1) The functional properties variation of casein-lactose (milk model system)after microwave treatment: adapted casein-lactose (1:1.6) model to construct the milkmodel. After microwave heating, the content of amino group decreased slightly, thesolubility of casein significantly improved at pH5.0and7.0. This system is theNewton fluid model, after microwave treatment, dynamic rheology and staticrheological property system were changed;(2) The microstructure result of casein-lactose model: after microwave treatment,the particles increases gradually from leveling regular small particles to irregularrough microstructure. Particle size determination results showed that particles size ofcasein-lactose model increases gradually, the results was in consistent withenvironmental scanning electron microscopy;(3) The variation of antioxidant activity, digestive rate and molecular weight ofcasein lactose model system treated by microwave during in vitro simulatedgastrointestinal digestion process: after microwave treatment, system digestibilityincreased and then decreased, antioxidant performance during digestion withextension of time, the antioxidant activity of Maillard reaction system were firstincreased and then decreased, to a certain degree, microwave treatment can promote the ABTS+scavenging ability, Fe2+chelating ability and reducing power of Maillardreaction system;(4) The infuence of microwave treatment on the structure characteristic ofcasein-lactose model system, the influence of microwave treatment on caseinstructure of casein-lactose model system, amino acid analysis indicates that the mainamino acid involved in Maillard reaction were lysine and arginine, the content oflysine decreased from0.303to0.280, arginine decreased from0.121to0.085aftermicrowave treatment for800w10min, other amino acids showed no regularity, andtotal amino acid content showed a downward trend, the reason may be microwaveand Maillard reaction work together to achieve these results; Infrared spectrumanalysis showed carbonyl was introduced under the condition of microwave treatmentfor800w and560w10min, the appearance of new absorption peak and characteristicpeak of glycosylation products emerged, further proved the Maillard reactionhappened; DSC analysis showed that the formation of Maillard reaction productspromoted the thermal denaturation temperature and the product became more stable.(5) Casein-lactose system (1:1.6)(milk model) and casein whey protein andlactose system (1:0.2456:1.579)(milk powder model) in microwave field400w15min, the casein was modified, the antioxidant activity and the function properties ofcasein were changed: functional properties were improved significantly, especiallythe solubility, significant increase in the vicinity of isoelectric point, and acidicconditions PH6.6compared to pH8.0is more conducive to the Maillard reaction inthe powdered milk. Antioxidant activity in the digestive process has a significantincrease (digestion for3h reducing power increased from0.15to0.55, ABTS+scanvenging activity increased from0.92mmol/L TEAC to about1.15mmol/L TEAC,DPPH+scanvenging activity increased from about10%to about40%), the Maillardreaction assisted by microwave of milk powder system can be used as the effectivemeans of producing a new type of milk powder additive. In general, after microwave treatment, the functional properties of the milkmodel changed significantly, but mainly adverse effects, and the change of the milkmodel in the digestive process also showed significant effects; The microwave canimprove the functional properties of milk powder model, especially solubility, thenmicrowave treatment can be used as a effective method to improve the solubility ofcasein, and extend the applied range of casein.