Whey and soy proteins as wall materials for spray drying rosemary: Effects on polyphenol composition, antioxidant activity, bioaccessibility after in vitro gastrointestinal digestion and stability during storage

A straightforward protocol was developed to produce rosemary particles using whey and soy protein carriers. The post-processing retention of carnosic acid (CA), carnosol (CR) and rosmarinic acid (RA), their bioaccessibility, in vitro antioxidant activity, and storage stability were investigated in protein-rosemary particles compared to rosemary extract (RME). Solids recovery was highest for whey protein or whey-inulin blend complexed with rosemary (R–WPI, R–WIN, ~90%), followed by soy protein or soy-inulin (R–SPI, R–SIN, 60% and 70%); all were higher than rosemary alone (RME, 52%). Protein or protein/inulin carriers significantly enhanced retention of CR (36.8–50.7 mg/g) and CA (17.1–19.6 mg/g) compared to RME (19.8 mg/g and 8.3 mg/g, respectively). In vitro digestibility showed that whey protein isolate increased the bioaccessibility of CA and CR, with no effect on RA, which was highly bioaccessible in all formulations. The rosemary-protein-treatments retained high antioxidant activity measured by ROS and NO assays. CR and CA were particularly stable during 20 weeks of storage in protein-rosemary particles, and stayed at their higher concentration compared to RME. Water activity was below 0.5 and remarkable color stability was observed during storage. Overall, spray dried protein-rosemary particles constitute a creative solution to deliver preserved phytochemicals in a high-protein food format.