Functional beverage production using acetous fermentation of soursop: Physicochemical, toxicity and organoleptic properties

Abstract Soursop (Annona muricata L.) is a highly perishable fruit and is often rejected by the market due to external injury or rapid aging process that leads to unacceptable senescence for further processing. A previous study has optimised the alcoholic fermentation of soursop to produce soursop wine using an alternative fermentative starter culture. Therefore, this study was aimed to produce soursop vinegar using an acetous fermentation and investigate the physicochemical, toxicity and organoleptic properties. Soursop vinegar showed significantly (p≤0.05) higher acetic acid (3.5 ± 0.3%), total phenolic content (220 ± 20 ppm gallic acid equivalence) and FRAP (ferric reducing antioxidant power) activity (222 ± 2 μM ascorbic acid equivalence), with lower pH, sugar, ethanol and DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging activity while retaining ascorbic acid, compared to those of soursop wine. A toxicity assay carried out using the fish embryos toxicity (FET) showed that the median lethality concentration (LC50) for fish embryos was 11.8 mg/mL, which was considered as non-toxic. Meanwhile, toxicity with human liver tissue (HepG2) using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay suggested that the cells’ survivability increased when the concentration of soursop vinegar was ≤6.25%. Sensory evaluation was carried out using quantitative descriptive analysis and the soursop vinegar was less sour and sweeter than commercial vinegar. This study offers an alternative way of reducing wastage of soursop fruit by the conversion of soursop into vinegar using a combination of alternative alcoholic and acetous fermentations.