Change in Fermentable Sugars in Sugar Beets Stored Anaerobically

Abstract

High-yielding sugar beets are becoming an attractive feedstock for the production of ethanol in the Red River Valley region of the United States. Long-term storage methods are necessary to preserve fermentable sugars in beets and allow successful yearlong operation of beet ethanol plants. Anaerobic storage of sugar beets was evaluated as an alternative to conventional pile storage currently used in sugar processing factories. Preliminary results indicated a loss of <15% in total fermentable sugars in sugar beets stored anaerobically for 14 wk at 4°C. After 14 wk of storage, 99±3.6% of the initial total fermentable sugars was preserved in beets stored aerobically at 4°C. Sugar beets stored aerobically and anaerobically at 25°C preserved 82±8.5% and 48±10.8% of their initial total fermentable sugars, respectively. After 7 wk of anaerobic storage at 25°C, a CO2 concentration of 61.1±1.7% was detected within the storage units. The CO2 reached a maximum concentration of 97.1±2.7% after 10 wk of storage before dropping to approximately 78.7±0.7% by week 12 and remained stable at week 14. The results suggested an improvement in storage by temperature reduction; however, the elimination of oxygen in the storage atmosphere resulted in a decrease of total fermentable sugars. Future ethanol quantification in both, the beet tissue and exudate within the anaerobic storage units, will provide valuable information to determine if the overall ethanol yield from stored sugar beets is preserved.