Potential Value-Added Products from Industrial Sweetpotato Syrup Processing

Due to their high starch content, industrial sweetpotatoes can serve as feedstocks for the manufacture of biofuels and value-added chemicals, with sugar syrup being a viable intermediate product. The potato remnants are also useful as a potential supplement for animal feed or as feedstocks for anaerobic digestion into biogas. In the present study, CX-1 variant industrial sweetpotatoes were converted into flour and enzymatically saccharified at a concentration of 20% (w/v). The sugar-rich liquid fraction was separated and concentrated through evaporation to a final density of 1.26 g/mL. The process had a yield of 0.85 kg syrup/dry-kg potato. Using the mass and sugar profile of the syrup, an estimated 81% of the total glucose available in the potato starch was extracted into the syrup. The residual solids were also evaluated for methane potential via anaerobic digestion, resulting in 428 LNCH4/kg VS added which correlates to 100% of the theoretical yield on a chemical oxygen demand (COD) basis. The recovered CX-1 glucose syrup residue was lower in fiber and richer in total protein and most of the essential amino acids compared to the original CX-1 feedstock, which makes it an attractive supplementary ingredient for animal feeds. The CX-1 industrial sweetpotato is not only a valuable feedstock for bio-based fuels, but syrup processing and the syrup residuals provide value-added products from this industrial crop.