Enzymatic Modification Of Caseins And Whey Proteins And Application Of Their Hydrolysates In Food Formulations

Proteins are essential food components because they are a source of amino acids needed for growth and maintenance and provide functional properties to foods. Modification of a protein usually refers to physical, chemical, or enzymatic treatments changing its conformation and structure and consequently its physicochemical and functional properties. The peptides produced by proteolysis have smaller molecular sizes and less secondary structure than proteins and may be expected to have increased solubility near the isoelectric point, decreased viscosity, and significant changes in the foaming, gelling, and emulsifying properties from those of original proteins. The peptides may be useful in various food-processing operations. Moreover, apart from the nutritional change (e.g. improved digestibility), hydrolysis may result in liberation of bioactive peptides.In this study, sodium caseinate (SC) and whey protein concentrate (WPC 80) were hydrolyzed by a series of enzymes from different sources (Trypsin, Pepsin, Alcalase 2.4L, Protamex, Papain, Flavourzyme, Neutrase, Immobilized Trypsin and Immobilized Papain) under a defined set of reaction conditions to produce casein and whey hydrolysates at different DH levels. Some analyses were done in order to provide evidence for their enzymatic modification.The results showed that all hydrolysates produced at various DH were different from unmodified protein (WPC 80 or SC) in protein, moisture and ash content. Free amino groups increased with increasing DH and TNBS determinations showed no significant difference in free amino groups for both SC and WPC hydrolysates from Alcalase 2.4L and Protamex at same DH level. Alcalase 2.4L produced little higher free amino groups compared to Protamex and free amino group content was higher in SC hydrolysates than in WPC hydrolysates. The IR absorption spectra of unmodified protein (SC and WPC 80) were different from those of their respective hydrolysates indicating that the hydrolysates have undergone some structural changes following the enzymatic hydrolysis.The molecular weight (Mw) distributions of SC, WPC 80 and their hydrolysates were determined by using two different chromatographic methods (SEC-HPLC and gel filtration chromatography) and compared in order to provide evidence for the effect of enzymatic modification on the resulting hydrolysates highlighted by their respective peptide size profiles.The chromatographic results confirmed that the peptides produced by proteolysis have smaller molecular sizes and the Mw distributions of the peptides from unmodified proteins (SC and WPC 80) were different from those of their respective hydrolysates. This study also demonstrated that the molecular size distribution depends on DH.SC, WPC 80 and their hydrolysates generated by different enzymes at various DH levels were used for measuring and comparing some techno-functional properties. The results indicated that all hydrolysates were different from unmodified protein (WPC 80 and SC) in determined techno-functional properties. All SC and WPC hydrolysates were able to form very low viscosity solutions even at high concentrations allowing them to be applied in development of high protein soft drinks and juice-based beverages. Enzymatic hydrolysis of WPC 80 and SC improved the solubility of their hydrolysates indicating potential useful applications in a variety of food formulations. In general, all hydrolysates showed poor emulsifying and foaming...