Ball milling alters the extractability and colloidal state of oat proteins

Oat protein must be extractable to play a functional role in liquid and semi-solid foods. Also relevant in this context is the colloidal state of the extracted oat protein, which is however rarely considered. Here, the impact of ball milling of defatted oat whole meal (DOW) on its protein extractability, composition and colloidal state in water, in a 1.0 M NaCl solution and in a medium at pH 9.0 was investigated. Overall, ball milling caused a decrease in DOW particle size and an increase in protein extractability, i.e. the protein recovery in the supernatant after extraction and centrifugation. Interestingly, for both control and ball milled DOW, increasing the applied centrifugal force after extraction led to a decreased protein extractability. Thus, a fraction of proteins – mainly 12S globulins as revealed by chromatography – remained in suspension at lower centrifugal force but precipitated at higher centrifugal force. This effect was more pronounced for ball milled DOW. These findings indicate that part of the 12S globulins in oat protein extracts, especially after prior ball milling, occur as protein aggregates. In conclusion, ball milling and altered centrifugation conditions after extraction can result in oat extracts with pronounced differences in protein level, composition and colloidal state.