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J. STOJANOVIC and J. L. Silva. Dept. of Food Science, Nutrition and Health Promotion, Mississippi State Univ., 110 Herzer Bldg., Mailstop 9805, Mississippi State, MS 39762-9805 In the U.S.A., production and per capita consumption of sweet potato decreased 74 and 90 % from 1932, respectively. Lack of convenient and valued added products could be one of the reasons for this decline. As an inexpensive, non-seasonal and nutritionally comparable to fruits, sweet potatoes can be used to produce a beverage that can be used by itself or in combination with other fruits and flavors. Decreasing starch content of sweet potato would be crucial step in the processing of such beverage. Our objective was to use different pretreatments using endogenous amylases and commercial enzyme mixes to decrease starch and increase sugar content of the sweet potato for the production of an acceptable beverage. Sweet potatoes were peeled, minced, mixed with water (75:25), heated and held at 70° C for 30 min. After treatment, the slurry was acidified with 0.12% citric acid to obtain a pH less than 4.5. Reducing sugars, expressed as maltose, were determined using DNSA color reagent, proteins using Bradford assay and total amylase activity was assayed by a method described by Bernfeld using soluble starch as a substrate. The commercially obtained enzyme preparation contained α-amylase and glucoamylase. Starch debranching enzyme pullulanase was not present in the sweet potato when assayed using highly specific substrate pullulan. Fresh sweet potato contained 2.9g of reducing sugars expressed as maltose, 1.5g of protein and total amylase activity was 150KU per 100g. Endogenous amylases increased reduced sugars to 5.5g and the total amylase activity decreased by 40% due to inactivation of the heat unstable β-amylase. The treatment with commercial enzyme preparation produced highest amount of reducing sugars. These results suggest that both pretreatments of sweet potato prior to extraction of juice can increase sugars and decrease starch thus adding value and new possibilities for the production of an acceptable beverage.
Session 84, Fruit & Vegetable Products: General I
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |