Study On Alcohol Fermentation Of Sweet Potato Residue And The Physico-chemical Properties Of Dietary Fiber From Its Mash

With the production of sweet potato starch, a large amount of waste residues were brought out which was discarded as waste or simply used as feed usually, resulting in waste of resources and environmental pollution. How to develop and utilize the potato residue resources had become tough problem which urgently need to solve in starch industry in China. In this topic, sweet potato residue was used as raw material for ethanol production, and then extracted dietary fiber from the mash after fermentation, provided a theoretical basis for the comprehensive utilization of sweet potato residue.First, the sweet potato residue was used for the alcohol fermentation,9 factors (α-amylase dosage, liquefaction temperature, liquefaction time, glucoamylase dosage, inoculation ratio, (NH4)2SO4, pH value, fermentation temperature, fermentation time) which influenced on simultaneous saccharification and fermentation were chosed for Plackett-Burman design. Glucoamylase dosage, inoculation ratio, fermentation temperature were selected as significant factors. Based on the selected results, the path of steepest ascent was used to approach the optimal region and response surface analysis were adopted to identify the optimal values of significant factors. The optimal process parameters for alcohol fermentation were:diastase (150.70IU/g), inoculum size (0.3%, w/w) and fermentation temperature (36.1℃). Under this condition, the alcohol concentration increased from 11.3%(v/v) to 16.17%(v/v), starch utilization ratio was 89.35%, reality alcohol productivity was 28.6 (g alcohol/100g sweet potato residue).Secondly, the alcohol fermentation mash of sweet potato residue was chosed as raw material for the preparation of dietary fiber by physical screening. The extraction rate of AFDF was 8.75%, the purity was 82.46%, insoluble and soluble dietary fiber were 59.67% and 23.16% separately, water swelling (13.26mL/g),water holding capacity (11.84g/g) and oil holding capacity (1.85g/g) were better, showing flaky porous structure with dark color and cation exchange capacity and emulsifying properties。Finally, the comparison of the basic physical and chemical properties among four different plant dietary fibers:AFDF.potato dietary fiber (SPDF). dietary fiber (SDF) and oat dietary fiber (ODF). Through the comparison, the the swelling capacity order was AFDF>SPDF>SDF>ODF; water-holding capacity order was SPDF>AFDF>SDF>ODF; oil-holding capacity order was AFDF>SPDF>SDF>ODF; cation exchange capacity order was ODF>SDF>AFDF>SPDF. ODF had best emulsifying properties, next were AFDF, SPDF and SDF.The results showed that the sweet potato residue was a cheap and high quality raw material for starchy alcohol fermentation, and a potential and available dietary fiber resource. It could increase its value through comprehensive utilization.