Effect of lactic acid fermentation on the quality and phytochemical constituent in smoothies made from the leaves of different sweet potato (Ipomoea batatas L.) cultivars

Abstract

This study investigated the effect of fermentation by Lactiplantibacillus plantarum 75 (L75) on the physicochemical properties, survival of L75, sensory, antioxidants and their activities in leaf smoothies of six sweet potato cultivars [Orange-fleshed (OFSP): ‘Bophelo’, and ‘Beauregard’; cream-fleshed (CFSP): ‘Blesbok’ and ‘Ndou’; and purple-fleshed (PFSP): ‘08.21p’ and ‘Purple-purple’]. Fermentation significantly affected the physiochemical properties. Fermentation for 24 h improved the carotenoid (TCC), ascorbic acid (AA) (6.8, 6.0 mg 100 g−1) and total phenolic (4435 mg 100 g−1) significantly in, ‘Bophelo’ smoothies. Whilst 48 h fermentation significantly increased the TCC, AA, organic acids, valine and alanine levels in ‘Blesbok’ smoothies'. Principal component analysis separated the unfermented ‘Bophelo’ and Purple-purple’ leaf smoothies from fermented leaf smoothies of OFSP, CSFP, and PFSP. DPPH scavenging activity and alpha-carotene were effective markers for separating fermented from unfermented leaf smoothies in the variable importance study. Survival of L75 was influenced by fermentation duration and cultivar type. Fermented and unfermented smoothies were equally acceptable.