Stabilization of Sweet Sorghum Juice for Long-Term Storage

Abstract

<abstract><title><italic>Abstract.</italic></title> Sweet sorghum is considered a promising alternative feedstock for ethanol production in the U.S. Southeast and Midwest. The most challenging issue in using sweet sorghum as a feedstock is the long-term storage of sweet sorghum juice for year-round supply of the fuel ethanol industry. As much as 20% of its fermentable sugars can be lost in three days after harvest due to bacterial activity. The purpose of this research was to evaluate some novel treatments to stabilize sweet sorghum juice for long-term storage. Sweet sorghum juice was homogenized at 32 kpsi and treated with ozone gas, 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 temperature. Results from this research showed that high-pressure homogenizing and ozone treatment 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 3M Petrifilm. After storage for three months at room temperature, the microbial counts of the treated juice remained ~3 log lower than those in the untreated juices. The untreated juice became thick and sticky, and its sugar profile changed significantly, retaining only around 30% of its original content. Although the sugar profiles of high-pressure homogenized juices changed, they retained 80% to 92% of their original sugar contents.