Proximate composition and sensory evaluation of anthocyanin-rich purple sweet potato (Ipomoea batatasL.) wine

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Purple sweet potato (PSP) is a special type of sweet potato having high anthocyanin pigment in the root. The starch contents of PSP (root/water homogenised in 1:1 ratio) were enzymatically saccharified [using commercial thermostable enzymes Termamyl® (0.2%) and Dextrozyme®GA (1%)] to fermentable sugars, and the filtrate was ameliorated with cane sugar to achieve 20° Brix, for subsequent fermentation into a red wine using 2% yeast (Saccharomyces cerevisiae) as starter culture. The wine had the following proximate compositions: total soluble sugar (TSS), 2.25° Brix; starch, 0.15 g per 100 mL; total sugar, 1.35 g per 100 mL; TA, 1.34 g tartaric acid per 100 mL; phenol, 0.36 g (caffeic acid equivalent) per 100 mL; anthocyanin, 55.09 mg per 100 mL; tannin, 0.64 mg per 100 mL; lactic acid, 1.14 mg per 100 mL; ethanol, 9.33%(v/v); and pH, 3.61. 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging activity of the wine was 58.95% at a dose of 250 μg mL−1. Principal component analysis reduced the eleven original analytical and proximate variables (TSS, starch, total sugar, TA, phenol, anthocyanin, tannin, lactic acid, ethanol, pH, DPPH) to four independent components, which accounted for 76.65% variations. Sensory evaluation was carried out by sixteen trained panellists on various attributes such as clarity, colour, viscosity, odour, flavour, spritz and finish. Independent ‘t’ test confirmed that all the sensory attributes of the PSP wine scored closely (within 10% variation) to that of a commercial grape wine. The red wine produced contains essential antioxidants and acceptable sensory qualities.

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