Soft gels from bovine colostrum

Abstract

Colostrum puddings are widely popular in India as well as in some European countries. To prepare these desserts fresh colostrum from the first or second day of lactation is heated and flavoured by adding spices and sugar. Depending on the day of lactation the colostrum is mixed with normal milk in order to achieve a thinner consistency. However, no thickening agents like starch or different polysaccharides need to be added since, in contrast to drinking milk, the early milk of cows and other mammals, called colostrum, forms gels without adding gelling agents when heated.The aim of this study is to understand the mechanisms involved in colostrum gel formation. In order to learn about the fat distribution in colostrum and the melting of the fat, initially, differential scanning calorimetry (DSC) and optical microscopy were performed. Furthermore, the colostrum gel formation was investigated by carrying out rheological measurements. Temperature and time sweep were used to characterize the gel formation of colostrum under heating and an amplitude sweep was performed to understand the forces and molecular interactions involved in the formation of the gel network. Taking into account the different composition of milk and colostrum and comparing their distinct behavior under heating, conclusions could be drawn about which mechanisms cause the formation of a colostrum gel.The gel formation of colostrum is caused by its significantly higher concentration of different proteins, especially β-lactoglobulin. During the heat treatment these proteins denature and subsequently rearrange themselves. Consequently, soft elastic gels are formed by β-lactoglobulin in combination with other proteins, such as IGF-1 (insulin-like growth factor 1), IGF-2 (insulin-like growth factor 2), N-acetylgalactosaminyltransferase 1 (GALNT1) and lactoferrin.