The buttermilk was selected as a wall material to deliver the docosahexaenoic acid (DHA) in this current research, including algal oil encapsulating with pure buttermilk (BMO) and its mixture (buttermilk and maltodextrin (BMMO)). The results showed that the particle growth rate of BMO and BMMO was slower than that of commercial algal oil powders (CMOs) during simulated digestion in vitro. Moreover, in the Morris water maze experiment, the mice in BMO and BMMO groups took less time to find the platform compared to that in CMO group, and their DHA content in the brain was significantly higher. The immunoglobulin detection revealed that feeding BMO and BMMO could improve the immune function of rats. Therefore, buttermilk will be a potential wall material which are able to improve the digestion characteristics of algal oil and the DHA bioavailability, and these results also promote the value-added utilization of by-products in the dairy industry.

In this study, ion exchange chromatography was employed to prepare high-purity α-lactalbumin from whey protein powder obtained from raw cow’s milk by sequential membrane separation and spray drying. The results showed that α-lactalbumin constituted 21.04% of the true protein in the permeate obtained using a 50-nm pore-sized ceramic membrane with three-fold concentration, one cycle of microfiltration and two cycles of washing, which was higher than that obtained using a 100-nm pore-sized ceramic membrane (15.84%). The permeate was spray dried and separated by ion exchange chromatography. Good chromatographic separation of α-lactalbumin and β-lactoglobulin was achieved with increasing NaCl concentration from 0 to 0.5 mol/L at up to 10 column volumes, and 98.18% pure α-lactalbumin and 97.82% pure β-lactoglobulin were obtained. The results of this study provide support for the industrial preparation of high-purity α-lactalbumin.