The Research On Gel Properties Of Casein Modified By Maillard Reaction

Casein was a full value protein and nutritious. However, some functional properties of casein can not meet the needs of food processing well. In this article casein was modified by Maillard reaction to study gel properties and preliminary inquiry mechanism aims to provide a reference for the development and research of functional food ingredients and additives. Maillard reaction with an amino compound with a carbonyl compound is a spontaneous non-enzymatic reaction under heating conditions to improve certain functional properties of the protein to some extent. This study aims to study casein modified by dry-heating Maillard reaction to improve the gel properties and study Maillard reaction mechanism preliminarily in order to provides theoretical reference for the study on the gel properties of casein.Firstly, the gel properties of casein-glucose and casein-maltose conjugates were studied. The effects of temperature, relative humidities, heating time, the weight ratio of casein to glucose were investigated. In order to optimize the gel strength index, the orthogonal test was used to optimize the process. The most optimum conditions were as follows:temperature 60℃, relative humidities 79%, heating time 3h, weight ratio of casein to glucose 1:1. Casein gel strength obtained under optimal conditions reached 1.4 times the non-modified casein gel strength.The effects of different reaction time on the functional properties of the Maillard reaction Graft were investigated. The results showed that the functional properties of the casein through the Maillard reaction modifications have improved. Solubility, viscosity, emulsification activity showed increases firstly then decreases trend with prolonged reaction time, which is consistent with the trend of the gel strength.The physicochemical properties of casein and Maillard mechanism were discussed. Absorbance measured at a wavelength of 420nm and the degree of grafting were increased with the reaction time. It can be seen, the level of Maillard was deeper with reaction time. Determination of absorbance at 294nm graft characterized that the generateion of intermediate product, substantially no increase in the intermediate product obtained after the reaction for 12 hours. From fluorescence spectra, the conjugates have the strongest florescence intensity when emission was 340nm and the excitation was 415nm. The result was consistented with fluorescence characteristics of Maillard reaction products and ensured that the Maillard reaction was happened. SDS-PAGE results showed that after the grafting reaction, the molecular of casein changes, macromolecules begain to generate after 3 hours. The structure of casein gels graft more closely and surface hydrophobicity of conjugates rised with increasing reaction time. Determination of mercapto group results showed that mercapto group packaged in the inner structure exposed through reaction, but amercapto groups did not transform to disulfide bond.