Storage stability of sweet sorghum juice after high-pressure homogenizing treatment

Abstract

As fuel ethanol market expands, sweet sorghum has been identified as a promising alternative feedstock for ethanol production in the Southeast and Midwest States in the United States. The most challenging issue for using sweet sorghum as feedstock is the long-term storage of sweet sorghum juice for year around supply for the fuel ethanol industry. As much as 20% of the fermentable sugars could be lost in three days after harvesting due to the activities of bacteria in the juice. The purpose of this research was to evaluate some novel and cost-effective treatments to stabilize sweet sorghum juice for year-around supply for the fuel ethanol industry. Sweet sorghum juice was homogenized at 32 kpsi and storage stability was evaluated by monitoring the chemical composition (fermentable sugar profile, organic acids and ethanol contents) and microbial characteristics (total aerobic count and lactic bacterial count) of the treated juices stored at room temperatures. Results from this research showed that high-pressure homogenizing of sweet sorghum juice could significantly reduce both aerobic bacterial counts and lactic acid bacterial counts (2.5 log reduction in ABC and more than 3 log reduction in LAB) as evaluated using the 3M Petri film. After storage for three months at room temperature, the microbial counts of the treated juice were still ~3 log lower than those in the untreated juices. The untreated juice became thick and sticky. The sugar profile of the untreated juice changed significantly and retained only around 30% of its original sugar content. Although the sugar profiles changed, the high-pressure homogenized juices retained 80% to 92% of the original sugar contents.