Preliminary study on the use of inexpensive, unsaturated vegetable oils as surface sealants in the long- and short-term storage of syrup feedstocks from sweet sorghum

Authors: Eggleston, Gillian; Boone, Stephanie; Triplett, Alexa; HECKEMEYER, MATTHEW - Heckemeyer Mill; POWELL, RANDALL - Biodimensions Delta Bio-Renewables, Llc; Wright, Maureen

Submitted to: Sugar Tech
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2017
Publication Date: 5/1/2018
Citation: Eggleston, G., Boone, S., Triplett, A., Heckemeyer, M., Powell, R., Wright, M., 2018. Preliminary study on the use of inexpensive, unsaturated vegetable oils as surface sealants in the long- and short-term storage of syrup feedstocks from sweet sorghum. Sugar Tech. 20(3):235-251.

Interpretive Summary: Fundamental processing needs identified by industry for the large-scale manufacture of biofuels and bioproducts from sweet sorghum include the long-term storage of syrups. Syrups containing 65 percent soluble solids are vulnerable to mold spoilage during storage. Three unsaturated vegetable oils which are inexpensive and readily available were evaluated as surface sealants (0 to 1.7 cm depth layers) on sweet sorghum syrups. Soy bean, canola, and sunflower oil sealants at 1.7 cm layers all preserved the syrups containing 65% soluble solids for up to 1 year. There was generally a strong surface oil layer effect. In strong contrast, soy bean oil (up to 0.5 cm depth layers) did not preserve syrups containing only 28% soluble solids against severe microbial deterioration.

Technical Abstract: Fundamental processing needs identified by industry for the large-scale manufacture of biofuels and bioproducts from sweet sorghum (Sorghum bicolor L. Moench) biomass feedstocks, include the long-term storage of 65 Brix (% dissolved solids) syrups for year-round supply and operation, efficient transport, and acceptable end-product yields. Additionally there is the need for the shorter-term storage of lower Brix syrup feedstocks of up to ~30 Brix (% dissolved solids) that can be fermented directly with no dilution at the industrial site. Sweet sorghum syrup of 65 Brix is vulnerable to mold spoilage during storage, especially on the surface, and this represents a major technical challenge. The storage (up to 1 year at ~25 °C) of pilot plant and industrial scale manufactured clarified syrups from sweet sorghum were evaluated. Three commodity, unsaturated vegetable oils which are inexpensive and readily available were evaluated as surface sealants (0 to 1.7 cm depth layers) on 65 Brix sweet sorghum syrups. Soy bean, canola, and sunflower oil sealants all preserved the 65 Brix syrups for up to 1 year. There was generally a strong surface oil layer effect, with 1.7 cm deep layers providing the most significant (P<0.05) protection. In strong contrast, soy bean oil (up to 0.5 cm depth layers) did not preserve 28 Brix syrups against severe microbial deterioration, particularly lactic acid bacterial deterioration, and loss of fermentable sugars even over 7 days of storage and, therefore, other stabilization technologies need to be investigated.