Microencapsulation of a green microalga (Chlorella vulgaris) by complex coacervation for its valuation as a feasible ingredient in pear snacks

Abstract

The nutritional and bioactivity values of Chlorella vulgaris make this green microalga a potential functional food ingredient. However, its unpleasant taste and smell, as well as dark green color, have been considered restrictive for its consumers' acceptability. Here, it was hypothesized that complex coacervation can be used to produce microcapsules able to mitigate the sensory weaknesses of C. vulgaris in think pear snacks, while ensuring their acceptance and intention to buy. For this, two proteins with similar isoelectric points were used, the pea protein isolate (PPI) and the bovine serum albumin (BSA), while the partially-sulfated carrageenan (C) was the selected polysaccharide to encapsulate C. vulgaris (6 % w/w), at pH 3. Higher encapsulation yield (79 %) and efficiency (75 %) were obtained for PPI/C coacervates due to these polymers' higher electrostatic interaction at pH 3, contrasting with the higher repulsion promoted by some negatively charged BSA amino acids. Despite this, both microcapsules exhibited an amorphous structure and low water activity (a_w around 0.3). However, PPI/C microcapsules had significantly lower moisture and water solubility (11 % and 57 %, respectively), as well as continuous shells. Moreover, PPI/C avoided the early release of C. vulgaris compounds at gastric conditions ensuring its later release in the intestinal tract. When incorporated into think pear snacks, the higher sensory scores and buying intention were obtained for snacks with PPI/C microcapsules containing C. vulgaris. Therefore, complex coacervation, particularly of PPI/C, allowed to mitigate non-valued microalga sensory attributes contributing for the future acceptance and consumption of algae-based food products.