Modification of the functional and bioactive properties of camel milk casein and whey proteins by ultrasonication and fermentation with Lactobacillus delbrueckii subsp. lactis

This study aimed to assess the effects of ultrasonication and lactic acid fermentation with Lactobacillus delbrueckii subsp. lactis on the functional and bioactive properties of camel milk whey proteins and caseins. For each protein fraction, sonication at 30 kHz modified the distribution of particle sizes by increasing the proportions of moderate-size particles (200-300 nm), which resulted in a 50% reduction of the z-average diameter of the particles. The negative surface charge of the whey protein particles remained unchanged after sonication, while the negative surface charge of the casein particles was significantly enhanced. Sonication and fermentation both significantly increased the antioxidant activity and angiotensin I-converting enzyme (ACE) inhibitory activity of whey proteins and caseins. The antioxidant activity of both fractions positively correlated with total aromatic content and ACE inhibition. These findings indicate that important functional and biological characteristics of camel milk whey and casein proteins, including antioxidant and antihypertensive potential, can be enhanced by sonication and fermentation with L. delbrueckii, possibly through sonication-induced structural modifications of the proteins and the release of bioactive peptides generated during fermentation.