In vitro digestibility and Caco-2 cell bioavailability of sea lettuce (Ulva fenestrata) proteins extracted with pH-shift technology

Abstract Seaweed is a promising sustainable source of vegan protein as its cultivation do not require arable land, pesticides/insecticides, or freshwater supply. Here, we aimed to assess the influence of pH-shift processing on protein degree of hydrolysis (%DH), protein/peptide size distribution, accessibility, and cell bioavailability of Ulva fenestrata proteins following in vitro gastrointestinal digestion. pH-shift processing of Ulva, which concentrated its proteins 3.5-times, significantly improved the %DH from 27.7±2.6% to 35.7±2.1% and the amino acid accessibility from 56.9±4.1% to 72.7±0.6%. Regarding bioavailability, the accessible amino acids of all samples were as bioavailable as casein. However, based on the higher amino acid accessibility resulting from pH-shift processing, the amount of most amino acids transported across the cell monolayers was higher in Ulva protein extracts. The protein/peptide molecular size distribution after digestion did not disclose a clear association with bioavailability. Altogether, the nutritional quality of seaweed proteins can be improved after protein extraction.