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The sweetpotato [Ipomoea (L.) Lam.] has approximately 90% carbohydrate of its dry matter, which makes it ideal for glucose syrup production. However, data regarding the isolation and use of sweetpotato starch (SPS) in syrup production are scanty. The objectives of this study were to: i) develop a syrup from SPS; and ii) determine the physicochemical (refractive index and color), and viscometric properties during storage of the sweetpotato syrup. SPS was isolated from Hillbilly variety field-grown sweetpotatoes. The SPS was rehydrated, heated to 102°C, treated with -amylase at 90°C for five hours, cooled, and further treated with glucoamylase at 62.5°C for 12 hours. The syrup was filtered, evaporated and cooled. The refractive index and color were measured. To determine the viscometric properties of the syrup during storage, the syrups were stored between 21±4°C (room temperature) and 4°C. An AR-2000 Rheometer was used to measure the viscometric properties of the syrup.

The objective of this study was to determine the effect of storage on the physicochemical properties of a sweetpotato beverage (SWPB) produced through centrifugation. The SWPBs were formulated using 19, 22, and 26% pureed sweetpotato and other ingredients. Each SWPB was centrifuged at 3,500 rpm for 10 minutes. The beverages were stored for 14 days at 5°C. Colony forming units were enumerated every 48h. SWPBs were diluted to 10-5 and distributed on Petrifilm plates in duplicate. ºBrix, color, pH, and ascorbic acid were measured. Analysis of variance (ANOVA) was used to determine whether there were differences among the means for ºBrix, color, pH, and ascorbic acid. Negligible microbial growth (0-42 CFU/mL) was observed for the beverages during storage. Solids contents in the SWPBs were constant, ranging from 15.2±0.3 to 15.3± 0.7. Lightness values were from 62.7, 63.3, and 63.9, for the 19%, 22% and 26% SWPB, respectively. The mean pH of the beverages ranged from 4.2 to 4.3.

The sweetpotato (Ipomoea batatas [L.] Lam) is a candidate crop for future space missions. However, sweetpotatoes are highly perishable and difficult to store, therefore, novel avenues for processing the surplus roots into value-added products that are commercially viable are needed. Technology was developed on a laboratory scale for the production of sweetpotato syrup and: i) the effect of varying levels of α-amylase on syrup quality determined; and ii) the storage stability and consumer acceptance of the syrup evaluated. Three levels of thermostable bacterial α-amylases (1.5, 3.0, 4.5 mL) were used for conversion of sweetpotato starch (SPS) into glucose syrup. The 1.5 mL α-amylase-treated was dropped from the experiment because there was no hydrolysis. The enzymatic conversion of SPS into glucose was significantly higher (P<0.05) for the 4.5 mL α-amylase-treated compared to the 1.5 and 3.0 mL levels.