Alcoholic fermentation of soursop (Annona muricata) juice through alternative fermentation technique.

Wines are produced through alcoholic fermentation of suitable substrates, usually sugar (sugar cane, grapes) and carbohydrates (wheat, grain). However, the conventional alcoholic fermentation is limited by the inhibition of yeast by ethanol produced, usually at about 13-14%. Aside from that, soursop fruit is a very nutritious fruit, but it is highly perishable, and thus produces a lot of wastage. Therefore, the objectives of this study were to produce fermented soursop juice (soursop wine), using combination of two starter cultures, i.e., mushroom (Pleurotus pulmonarius) and yeast (Saccharomyces cerevisiae) and to determine the effects of fermentation on the physicochemical and antioxidant activities of fermented soursop juice. Optimisation of four factors (pH, temperature, time, culture ratio) using response surface methodology (RSM) were performed to maximise ethanol production.The optimised point for alcoholic fermentation were pH 4.99, 28.29°C, 131hr and 0.42 culture ratio (42:58, P. pulmonarius mycelia:S. cerevisiae) with predicted value of ethanol concentration of 22.25%. Through verification test, soursop wine with 22.29±0.52% of ethanol was produced. The antioxidant activities (DPPH and FRAP) showed significant (p<0.05) increase from the soursop juice to soursop wine.The alternative fermentation technique using yeast and mushroom has successfully been optimised, with increased ethanol production in soursop wine and higher antioxidant activities. Ultimately, this finding has high potential to be applied in the brewing industry to enhance the fermentation process as well as to come up with innovative niche product, and reduces wastage by converting the highly-perishable fruit into wine with more stable and longer shelf-life. This article is protected by copyright. All rights reserved.