Solid–Liquid Extraction of Carbohydrates from Defatted Rice Bran Using Green Techniques: An Optimization Study

Defatted rice bran (DRB), a by-product of rice processing primarily used as animal feed, holds potential for food and pharmaceutical production applications due to its carbohydrate content. This study aimed to optimize and compare two solid–liquid carbohydrate extraction methods: ultrasound-assisted extraction (UAE) and hydrothermal treatment. A progressive experimental design strategy was employed for both methods. Carbohydrates were quantified using the Anthrone method, and FTIR analysis was conducted to identify functional groups. Optimal UAE conditions included a DRB-to-water ratio of 65 g·L−1, ultrasonic power of 350 W, and an extraction time of 20 min, yielding 60 gCHO·100 gDRB−1 with an extraction efficiency of 98.30%. For the hydrothermal method, the optimal conditions were a DRB-to-water ratio of 100 g·L−1, a pH of 6.0, and an extraction time of 35 min, achieving a yield of 48 gCHO·100 gDRB−1 with a 78.30% efficiency. The UAE method demonstrated higher efficiency, faster processing time, and lower operating temperatures compared to the hydrothermal treatment. FTIR analysis confirmed the successful identification of carbohydrate functional groups with spectral similarities to standard sugars. This study highlights the potential of DRB as a carbohydrate source and demonstrates the value of optimizing extraction methods to enhance yield and efficiency.