Ultrasonic extraction, structural characterization, and antioxidant activity of oligosaccharides from red yeast rice

Abstract

Red yeast rice is consumed as a medicinal food to lower blood lipids. Besides, it is used to color food, make wine, etc. In this study, water‐soluble oligosaccharides in red yeast rice were extracted by ultrasonic‐assisted extraction method. The parameters to extract oligosaccharides from red yeast rice were optimized by the Box‐Behnken design under the following optimal extraction conditions: extraction temperature, 60°C; extraction time, 97 min; and liquid/material ratio, 25 ml/g. The structure and the antioxidant activity of the new oligosaccharide were preliminarily investigated. Total carbohydrates extracted from red yeast rice with 80% ethanol–water solution (v/v) were first removed from pigments using D101 macroporous adsorption resin. The total sugar contents were then purified by DE52 resins and Sephadex G‐25 resins to obtain red yeast rice oligosaccharides, coded as RYRO1. Structural characterization experiments indicated that RYRO1 is an oligosaccharide with a weight average molecular weight of 874 Da and a theoretical degree of polymerization of 4.86. RYRO1 is composed of mannose, glucosamine, glucose, and galactose with a molar ratio of 0.248:0.019:1:0.026. The ABTS, DPPH, and hydroxyl free radical scavenging assays showed antioxidant nature of RYRO1.

Effects of roasting temperature and duration on color and flavor of a sesame oligosaccharide-protein complex in a Maillard reaction model

“…Protein is one of the most important macromolecules in food, which has been confirmed to be closely associated with flavor formation ( Zhang, Kang, Zhang, & Lorenzo, 2021 ). Oligosaccharides are a class of water-soluble sugars that are abundant and widely distributed in nature; they commonly consist of 2–10 monosaccharides connected by α- and β- glycosidic linkages ( Liu et al, 2022 , Xiong et al, 2021 ). Water-soluble sugars generally play key roles in flavor formation during food processing; for example, they produce furfural and pyrones which give food what consumers recognize as a caramel flavor ( Li, Shi, Li, Luo, & Li, 2022 ).…”

Extraction process, physicochemical properties, and digestive performance of red yeast rice starch

“…This may be because with the increase in the extraction solution, it will make the RYR powder fully contacted the extraction solution and promoted the leaching of RYR starch, reaching saturation when the liquid-to-solid ratio was 6 mL/g. 27 At this time, if the amount of extraction solution continues to increase, it may dissolve some other substances in the RYR, resulting in a decrease in the purity and yield of starch, thus hindering the extraction and separation of starch, and also causing a waste of solvent and energy, so the better liquid-to-solid ratio is 6 mL/g. 28 As shown in Figure 1B, during the gradual increase of the sodium hydroxide concentration from 0.05 to 0.15 mol/L, the starch extraction was the first to increase, with the highest RYR starch extraction at a sodium hydroxide concentration of 0.075 mol/L, and then gradually decreased again.…”

“…As shown in Figure 1A, the starch extraction rate increased and then decreased as the liquid–to‐solid ratio gradually increased from 2 to 10, and the starch extraction rate of RYR was the highest when the liquid–to‐solid ratio was 6. This may be because with the increase in the extraction solution, it will make the RYR powder fully contacted the extraction solution and promoted the leaching of RYR starch, reaching saturation when the liquid–to‐solid ratio was 6 mL/g 27 . At this time, if the amount of extraction solution continues to increase, it may dissolve some other substances in the RYR, resulting in a decrease in the purity and yield of starch, thus hindering the extraction and separation of starch, and also causing a waste of solvent and energy, so the better liquid–to‐solid ratio is 6 mL/g 28 …”

“…5,6 According to statistics, there are more than 100 types of nutraceuticals containing RYR in the Chinese market. 7 RYR-based lipid-lowering proprietary Chinese medicines, such as Xuezhikang and Zhibituo, which have been approved by the State Drug Administration, are also popular in China. 8,9 RYR has also been used as an alternative treatment option for patients with statin intolerance in the United States.…”

“…Currently, RYR has been widely studied and developed as a nutraceutical and lipid‐lowering drug 5,6 . According to statistics, there are more than 100 types of nutraceuticals containing RYR in the Chinese market 7 . RYR‐based lipid‐lowering proprietary Chinese medicines, such as Xuezhikang and Zhibituo, which have been approved by the State Drug Administration, are also popular in China 8,9 .…”