Chemical Preservatives-Based Storage Studies and Ethanol Production from Juice of Sweet Sorghum Cultivar, ICSV 93046

Abstract

Sweet sorghum is an ideal feedstock for ethanol production, in view of the increased global demand for biofuels. Sweet sorghum juice is a perishable commodity and the stalk juice has a short shelf life (4-5 h) postcrushing due to its high fermentable sugar content and the rapid sugar degradation during storage is due to the metabolic activities of contaminating spoilage bacteria. Hence, the preservation of the juice is required for quality retention and to extend the storage shelf life of the juice. In the present study, the effect of chemical preservatives to extend the storage stability of sweet sorghum juice and its later bioconversion to ethanol was studied. Among the chemical preservatives evaluated, the juice samples spiked with sodium benzoate and sorbic acid delayed the increase in reducing sugars and thus prevented browning of juice during storage. Sodium benzoate and sorbic acid-spiked samples showed a decrease in the total sugar content from 13.03 to 10.7 % and 11.35 to 10.16 %, respectively, over a storage period of 96 h. Ethanol yield was in the range of 0.425-0.475 g g-1 and 0.405-0.445 g g-1 with optimal efficiency of 93 and 92 % for sodium benzoate and sorbic acid, respectively, while the control showed a reduction in yield from 0.36 to 0.26 g g-1 and efficiency by 57 %. Sodium benzoate (at 1,000 ppm concentration) was identified as suitable preservative to retain the quality and extend the storage shelf life of fresh sweet sorghum juice up to 2 days at 37°C.