Improved in vitro digestibility of rapeseed napin proteins in mixtures with bovine beta-lactoglobulin.

Mixing of different protein sources can lead to either predictable, synergistic, or antagonistic effects on the protein digestibility. This study investigated the in vitro protein digestibility (IVPD) of protein mixtures between a napin-rich rapeseed (Brassica napus L.) protein concentrate (RP2) and bovine milk whey proteins (WPs; α-LA, alpha-lactalbumin; β-LG, beta-lactoglobulin) at mixing ratios of 20:80, 40:60, 60:40, and 80:20 w/w protein. Enzymatic hydrolysis consisted of pepsin digestion (1 h) followed by short- (+1 h), medium- (+3 h), or long-term (+24 h) pancreatin digestion. IVPD was differentially affected by the WPs type, mixing ratios, and total hydrolysis times. RP2/β-LG protein mixtures showed a partially synergistic effect at mixing ratios of 40:60 and 60:40 w/w, leading to an increased short-term IVPD of 7-10%. LC-MS analysis revealed a markedly improved short-term digestibility of the napin proteins when combined with bovine β-LG. This study demonstrated that specific mixtures between animal and plant protein sources exhibit an improved digestibility due to synergistic protein-protein interactions.