Carbohydrate-digested rice (CDR) residue, the production waste of electrolyte drinks, contains high levels of proteins (approximately 50% of dry matter). Methods for effectively extracting protein from CDR were investigated in this study by comparing alkaline and enzymatic extraction. Alkaline extraction was performed using different concentrations of sodium hydroxide (NaOH). Enzymatic extraction was performed with either commercial Alcalase ® or Flavourzyme ®. Protein recovery and solubility, and total soluble protein obtained via each method were compared to determine extraction effectiveness. In addition, extraction factors affecting protein recovery were adjusted to determine the optimal conditions for each method. Alcalase provided the maximum protein recovery (30.04%), while less protein recovery was achieved with 0.1 N NaOH (55 C), 1 N NaOH (55 C), and Flavourzyme. Although the protein recovery achieved by 0.1 N NaOH (27.43%) was close to that of the Alcalase method, protein solubility by extraction with 0.1 N NaOH was much lower (23.46%) than that achieved via the enzymatic method (100%). Hence, the total soluble protein resulting from Alcalase extraction was higher than that obtained using either of the alkaline methods. Consequently, Alcalase extraction was determined to be the most effective method for extracting protein from CDR.

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Sports drinks are developed to improve performance and prevent or treat dehydration, heatstroke, and muscle cramps. The osmolality and pH of sports drinks affect fluid retention and restoration of fluids lost due to dehydration. This study aimed to compare the effects of a new rice-based sports drink (hypertonic, D group) on performance and related sports physiology with that of four other drinks (control, group A; isotonic, group B; hypotonic, group C; commercial, group E), and to develop a range of rice-based sports drinks. The pH, total titratable acidity, nutritional value, and osmolality of the five drinks were measured in vitro. The association between the osmolality of sports drinks and performance was determined in 20 football players. Tests were performed using a cycle ergometer, after which the blood samples were obtained. Blood glucose levels were significantly higher in groups B, C, D, and E than in the control group (p < 0.05). Blood lactate levels were significantly lower in group D than in the other groups after exercise (p < 0.05). The osmolality of the hypertonic rice sports drink was 402.34 mOsmol/kg, indicating that this drink is expected to enhance endurance performance. Consumption of hypotonic rice drinks affects endurance performance in a similar manner to isotonic drinks and may be more beneficial to endurance performance relative to water and hypotonic drinks that lack sodium. Rice hypertonic drinks can even improve performance by drawing fluid from the circulation into the gut. Understanding osmolality and sports performance values can be useful in commercial beverage production and sports nutrition.