Post-Harvest Deterioration In Sweet Sorghum.

Sweet sorghum is a potential feedstock for sugar-based biofuel production since high concentrations of sugars accumulate in the stalk.  To better understand how harvesting options influence processing parameters, sweet sorghum was hand-cut and stripped, and cut into four sizes: shredded, 20-cm billets, 40-cm billets, or whole stalks.  The sorghum was then stored for up to 4 days at ambient temperature before processing to extract the juice.  Quality parameters measured included juice pH, titratable acidity, Brix, and simple sugars.  Juice pH and titratable acidity were the most rapid and easiest measures of juice deterioration.  Juice pH dropped from 5.5 to 3.5 within 24 h after harvest in the shredded treatment, while titratable acidity increased from 3 mL to 18 mL 0.1 N NaOH per 10 mL juice in the same time period.  Juice Brix was not a good measure of deterioration, since it either increased or remained the same during the 4-day storage period, even in deteriorated juice.  Sucrose decreased with storage, while glucose and fructose increased in juice from billets and whole-stalks.  In freshly harvested juice, glucose concentrations were about twice the fructose concentrations.  However, in deteriorated juice, glucose and sucrose disappeared, while a residue of fructose remained.  There were no significant differences in sugars among the two sizes of billets and whole stalks during the post-harvest period.