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United States Department of Agriculture

Agricultural Research Service

Research Project: Postharvest Quality and Processing of Sugarcane and Sweet Sorghum for Sugar and Ethanol Production

Location: Commodity Utilization Research

2012 Annual Report

1a. Objectives (from AD-416):
The overall objective of this project is to enhance the value of sugarcane and sweet sorghum, and their major commercial products sugar and ethanol, respectively, by improving postharvest quality and processing. Develop markers of low quality harvested sugarcane and sweet sorghum to predict sugar factory/distillery processing. 1) Characterize and improve sugar industry process units to minimize the impact of sugarcane trash on factory performance, including sucrose losses. 2) Identify and develop commercially viable processing technologies for the production of very high pol (VHP) and very low color (VLC) raw sugars in sugar factories. 3) Improve postharvest processing of sweet sorghum and sugarcane for syrup and bioethanol production.

1b. Approach (from AD-416):
Undertake field and factory trials to characterize the affect of green sugarcane trash on processing and manufacture of VHP and VLC raw sugars. Undertake laboratory, pilot plant, and factory studies to reduce the negative impact of green trash impurities on industrial processing of sugarcane by improving process controls, designs, and the use of processing aids. Develop and deliver methods to sugarcane breeders and sugar processors that can be used to measure sugarcane quality indicator compounds, which in turn can predict future processing problems. Develop and deliver methods to sweet sorghum processors to predict processing problems and final bioethanol yields. Improve the harvesting and factory delivery protocol for sweet sorghum for the manufacture of syrup at existing sugarcane factories and the storage of sugarcane and sweet sorghum syrup for the manufacture of bioethanol.

3. Progress Report:
Large studies across two Louisiana processing seasons were completed to ascertain the effects of harvest date and variety on sugarcane juice quality parameters as they affect high quality raw sugars for supply to refineries. The maturity characteristic of the variety played a critical role in seasonal variation of quality parameters, especially starch. Later maturing varieties deliver relatively higher amounts of starch across the whole season and have contributed to the much higher levels of starch being delivered to Louisiana sugar factories in recent years. Overall, for all parameters studied the type of tissue had the strongest effect, followed by variety, then date of harvest; the varietal effect was greatest in the stalk than other tissues. This strongly suggests that breeding programs could include quality parameters as selection criteria. In collaboration with scientists from ARS-USDA-Houma, Louisiana, we showed that forage harvesting of sweet sorghum into shredded stalks creates too much deterioration and loss of fermentable sugars between industrial cut-to-crush times. Final recommendations to sweet sorghum growers in the Mississippi Delta Region are 8 to 16 inch billets (short pieces of stalk). How clarification of sweet sorghum juice affects the quality of syrups was not known. In new studies, we investigated the use of heat, lime, coagulants including proteins, and flocculants to produce clarified juice which was then evaporated under vacuum into syrup. Juice clarification greatly improved the quality of syrup and amount of fermentable sugars produced.

4. Accomplishments
1. Developed an industrial sweet sorghum clarification method. The industrial clarification method developed includes heating sweet sorghum juice to 85┬░ centigrade (C) to create natural flocs that are then enlarged by adding milk of lime solution to form calcium-phosphate bridges (larger flocs). The sweet sorghum juice is limed to 6.5 to prevent unnecessary degradation of fermentable reducing sugars. Finally, polyanionic flocculant at 5 parts per million is added to add molecular weight to the flocs, which aids precipitation of flocs and impurities. ARS researchers at the Southern Regional Research Center in New Orleans, Louisiana, successfully scaled the clarification method up to the pilot plant level and it is being used by a biorefinery plant near Memphis, Tennessee. Furthermore, a strong sweet sorghum cultivar effect was discovered for juice quality, clarification performance, and clarified juice quality, which strongly indicates that sweet sorghum breeding programs are need in the USA.

2. Determined how different speeds of the extractor fans on sugarcane combine harvesters affect trash levels of in product. Total trash levels were 12.1, 18.9 and 22.7% at 1050, 850, and 650 revolutions per minute fan speeds, respectively. There was extra trash than hand-cut field cane at 850 and 650 rpm because of slight layers of mud on the trash adding to the weight and weedy plant material. ARS researchers at the Southern Regional Research Center in New Orleans, LA, showed that most cane quality and processing parameters, including fiber, soluble solids, sucrose concentration and purity, starch, color, percent extraction, processing rate, and mud volume became progressively worse with increased trash levels and decreased fan speed. Net proceeds to the grower were optimal for both growers and processors at the 850 rpm setting.

3. Developed a specific and sensitive method to quantitatively measure residual amylase activity in industrial sugars. Phadebus® tablets containing cross-linked starch with blue dye were used for the work. The incidences of residual amylases in sugars have been increasing in the U.S. and when they occur can cause devastating starch degradation problems in end products such as starch puddings, barbeque sauces, etc. ARS researchers at the Southern Regional Research Center in New Orleans, LA, overcame difficulties in measuring the very low activity of the residual amylases in sugar by greatly enhancing sensitivity by dissolving the sugar in a calcium chloride buffer adjusted to pH 6.0 and keeping the reaction time to only 45 min after which the enzyme reaction decreased. This method will be of great help to factory processors, refiners, and end-product users to check batches of sugars they produce.

Review Publications
Lingle, S.E., Thomson, J.L. 2012. Sugarcane internode composition during crop development. BioEnergy Research. 5:168-178.

Eggleston, G., Birkett, H., Gay, J., Legendre, B., Jackson, W., Schudmak, C., Monge, A., Andrzejewski, B., Viator, R., Charlet, T. 2012. How combine harvesting of green cane billets with different levels of trash affects production and processing. Part I: Field yields and delivered cane quality. International Sugar Journal. 114(1358):83-90.

Lingle, S.E., Tew, T.L., Rukavina, H., Boykin, D.L. 2012. Post-harvest changes in sweet sorghum I: brix and sugars. BioEnergy Research. 5:158-167.

Eggleston, G., Huet, J.-M. 2012. The measurement of mannitol in sugar beet factories to monitor deterioration and processing problems. Zuckerindustrie. 137(1):33-39.

Eggleston, G., Birkett, H., Gay, J., Legendre, B., Jackson, W., Schudmak, C., Monge, A., Andrzejewski, B., Viator, R., Charlet, T. 2012. How combine harvesting of green cane billets with different levels of trash affects production and processing. Part II: Pilot plant processing to sugar. International Sugar Journal. 114(1359):169-178.

Eggleston, G., Wu Tiu Yen, J., Alexander, C., Gober, J. 2012. Measurement and analysis of the mannitol partition coefficient in sucrose crystallization under simulated industrial conditions. Carbohydrate Research. 355:69-78.

Kavas, M. Fusun, Eggleston, G., Parkin, G., White, B., Sezer, G., Pardoe, K. 2008. Comparitive study of copper reduction, chromatographic and enymatic methods to determine reducing sugars in molasses. Zuckerindustrie. 133(3):129-134.

Last Modified: 06/27/2017
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