Abstract
This study explored the optimal preparation and the antioxidant levels of rice/adzuki bean mixtures. We compared the quality and physicochemical characteristics of cooked mixtures of rice and adzuki beans prepared using normal and high-pressure rice cookers, with and without the addition of alcohol (15%, v/v). The water-binding capacity and swelling power decreased upon addition of adzuki beans, but water solubility increased. The peak, trough, final, and setback viscosities decreased, but the breakdown viscosity increased. The total polyphenol and flavonoid contents increased after addition of adzuki beans. Total polyphenol contents in cooked rice/20% (w/w) Arari and Geomguseul bean mixtures in a normal cooker with addition of alcohol were 3.00 and 3.09 times higher than plain rice. The flavonoid contents were 10.33 and 8.90 times higher than plain rice. The predominant phenolic acids in cooked rice/Arari bean mixtures were p-coumaric acid and trans-3-hydroxycinnamic acid, and in cooked rice/Geomguseul bean mixtures, they were syringic acid and trans-3-hydroxycinnamic acid. Overall, phenolic acid levels were higher in mixtures cooked in plain water. The DPPH- and ABTS-radical-scavenging activities increased upon addition of adzuki beans. DPPH radical-scavenging activities in cooked rice/20% (w/w) Arari and Geomguseul bean mixtures in a normal cooker with addition of alcohol were 9.09 and 9.22 times higher than plain rice. ABTS radical-scavenging activities were 8.74 and 9.01 times higher than plain rice. Moreover, rice/adzuki bean mixtures prepared in a normal cooker, with addition of alcohol, exhibited higher antioxidant levels than other samples. We present the antioxidative properties of rice/adzuki bean mixtures prepared in different ways; these data will aid manufacturers.
Highlights
Adzuki beans (Vigna angularis) are cultivated and consumed principally in East Asia [1], where the adzuki beans are traditionally used to make confectionery pastes [2]
Amylose content correlated negatively with viscosity but highly with the heat and shear resistances evident during processing [22]. e breakdown viscosity of mixtures containing both Arari and Geomguseul beans (5โ20% w/w) were 73.2โ76.8 and 71.4โ79.0 RVU, respectively, and did not vary by the adzuki bean proportion. e final viscosity was measured after completion of both heating and cooling; starch particles recombine to increase viscosity [22]
As the adzuki bean proportion increased, the final viscosities of mixtures containing both Arari and Geomguseul beans fell to 138.6โ195.8 and 134.5โ195.5 RVU, respectively. e setback viscosity reflects starch aging; the higher the value, the more rapid the aging [22]. e setback viscosity is obtained by subtracting the peak from the final viscosity; the higher this value, the faster the aging; lower values indicate slower aging and a longer duration of the desired taste. e inverse relationship between the proportion of adzuki beans and setback viscosity was found. us, the higher the adzuki bean proportion, the slower the aging
Summary
Adzuki beans (Vigna angularis) are cultivated and consumed principally in East Asia [1], where the adzuki beans are traditionally used to make confectionery pastes [2]. Compared with other commercial starches, adzuki bean starch a ords certain advantages, including noninduction of chronic disease because of the relatively low insulin response, a high paste shear resistance, and good granule stability [3]. E adzuki beans can be used to prepare various foods, including adzuki bean pastes, desserts, pastries, and drinks, and can improve taste, avor, and viscosity. Many studies have reported that adzuki bean extracts exert a variety of physiological functions, including antioxidant, anti-in ammatory, antiatherosclerosis, anticancer, and procardiovascular activities [5, 6]. Oxidative stress is characterized by excessive production of reactive oxygen species (ROS) combined with an inadequate or defective antioxidant defense system [12]
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