Abstract
The effect of high hydrostatic pressure (HHP) treatment on dried soybean, adzuki bean, and kintoki kidney bean, which are low-moisture-content cellular biological materials, was investigated from the viewpoint of water absorption. The samples were vacuum-packed with distilled water and pressurized at 200 MPa and 25 °C for 10 min. After the HHP treatment, time courses of the moisture contents of the samples were measured, and the dimensionless moisture contents were estimated. Water absorption in the case of soybean could be fitted well by a simple water diffusion model. High pressures were found to have negligible effects on water absorption into the cotyledon of soybean and kintoki kidney bean. A non-linear least square method based on the Weibull equation was applied for the adzuki beans, and the effective water diffusion coefficient was found to increase significantly from 8.6 × 10−13 to 6.7 × 10−10 m2/s after HHP treatment. Approximately 30% of the testa of the adzuki bean was damaged upon HHP treatment, which was comparable to the surface area of the testa in the partially peeled adzuki bean sample. Thus, HHP was confirmed to promote mass transfer to the cotyledon of legumes with a tight testa.
Highlights
Rice—an important source of carbohydrates—is the most widely consumed staple food in Japan, but recently, there has been a marked increase in the consumption of functional foods.Examples of such functional foods include polyphenol-enriched adzuki bean, peptide-/GABA-enriched soybean, and white kidney bean
Changes in the moisture contents of the control and the high-pressure-treated soybeans are shown in Figure 2A, where identical water absorption curves can be seen for the control and the pressure-treated (200 MPa) soybeans
The sorption mechanism was identical in the untreated control and in the high hydrostatic pressure (HHP)-treated soybeans because water could permeate through the testa of the bean and reach the cotyledon; the soybean surface remained undamaged even after
Summary
Rice—an important source of carbohydrates—is the most widely consumed staple food in Japan, but recently, there has been a marked increase in the consumption of functional foods Examples of such functional foods include polyphenol-enriched adzuki bean, peptide-/GABA-enriched soybean, and white kidney bean (rich in minerals, vitamins, and fiber). These beans are traditionally cooked in various forms in Japan; for example, adzuki beans are combined with white rice to prepare red rice; fermented soybeans are used to prepare Natto; and Cereal coarse Miso (fermented bean paste) is a coarse mixture of soybean, adzuki beans, barely, brown rice, and oats. In this study, considering the potential of HHP in inducing beneficial structural changes in food products, we decided to investigate the effect of high-pressure treatment on dried beans with low. Increased water uptake in treated beans can help in converting them into valuable food products
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