Neutrons and Food 8 at MLZ

Caseinates are functional protein ingredients derived from milk, which form small, nanometer-sized aggregates in solution. They form stable gel networks upon acidification, which can be strengthened by cross-linking using enzymes such as transglutaminase.

While the acid-induced gel formation of cross-linked caseinates has been studied in detail in the past, the conformational changes of the caseinate nanoparticles induced by cross-linking remain largely unexplored. Light scattering indicated some changes in size, density and shape (doi:10.1016/j.foodhyd.2019.01.043), but these might be artefacts from dilution. SAXS, however, allows to study the conformation of caseinates in undiluted systems.

In this study, caseinate (27g/L) with varying degrees of enzymatic cross-linking was investigated using SAXS before and after dilution. SAXS of the undiluted solutions revealed minimal conformational changes. However, upon dilution to 10 g/L protein and, especially, upon addition of urea, the differences became more apparent, indicating dissociation of un- and less cross-linked casein.

In the presentation, the conformation of caseinates cross-linked using transglutaminase will be discussed and related to their acid gelation properties. With the rise of new technologies such as precision fermentation, new protein ingredients such as microbial caseins will enter the market soon, and understanding of their structure-function interrelations is needed to exploit their potential in food.