The application of subcritical water treatments to valorize certain plant-based agricultural waste is reviewed with a focus on the extraction of phenolic compounds and the production of oligosaccharides. Phenolic compounds can be efficiently extracted by raising the temperature to an optimal value; however, many phenolic compounds are decomposed at high temperatures. Nevertheless, some degradation products of phenolic compounds also show high antioxidant activity. The conversion of polysaccharides from plant-based agricultural waste into smaller polysaccharides or oligosaccharides may be an alternative method for the preparation of ingredients with health benefits.
A cultivation behavior in high density cultivation of mung bean sprouts was investigated from the engineering viewpoint. The effect oxygen concentration on the growth rate was evaluated, because heterotrophic growth and secondary metabolism reactions were related to oxygen. The cart with controllable circuit for gas phase was used for high density cultivation. In a growing test of mung bean in high density and individual cultivations under various oxygen concentrations, courses of fresh weight, and whiteness index of seedling of mung bean sprouts were measured, and specific growth rate based on fresh weight were investigated. In high density cultivation, specific growth rate was faster than in individual cultivation, and differences in growth rate according to growth stage were observed with oxygen concentration. On low oxygen concentration whiteness index of the seedling raised. Therefore, it is assumed that oxygen concentration was so low that secondary metabolism reaction of brown substances in root of seedling was limited. These results suggest that growth and secondary metabolism reactions in high density cultivation could be regulated by controlling oxygen concentration in gas phase. In this study, we proposed that the concept of Controlled Atmosphere (CA) might be applied in plant cultivation as well as CA storage.
An open reactor with gas bubbling with various oxygen partial pressure was applied to investigate the role of oxygen in the oxidation of ascorbic acid (AA). The reaction kinetics was described well by the zero-th order mechanism and the rate constant was exactly proportional to the oxygen partial pressure but no effect of initial AA concentration was observed. The reaction rate increased with an increase in pH and decreased by the addition of EDTA as a chelating agent to trace metals suggesting the involvement of metals in the AA oxidation process. The temperature dependence of the kinetics was measured from 0 to 70℃ and the activation energy was obtained to be 62.1 kJ/mol. On the contrary, the AA oxidation was described by the 1-st order kinetics in a closed reactor system because of the limiting oxygen supply. From these results, the aerobic AA oxidation scheme was estimated with the reaction between molecular oxygen and AA as a limiting step.
To produce a characteristic craft beer, a flavor-producing wild yeast was isolated using an enriched culture method from tree sap collected from the Ise-shima area. A comparative analysis of the sequences of ITS1-5.8S rDNA-ITS2 region indicated that the isolated strain was related to Saccharomyces cerevisiae and was named KADOYA1. To evaluate the characteristic and utility of KADOYA1, a commercial scale (1,000 L) of beer production test was performed using ale beer yeast strains 1056 and 3068 as a control. The fermentation rate of KADOYA1 was slightly lower than that of strains 1056 and 3068, but ethanol production was sufficient. The odor properties of beer brewed with each yeast strain were estimated by gas chromatography-mass spectrometry, and a fragrance evaluation was performed using an electronic noses (FF-2A). The results showed that the beer brewed with KADOYA1 has a characteristic odor that is different from that of the beers brewed with the other two strains. KADOYA1 was deemed to be a commercially useful yeast for craft beer production because it has sufficient fermentation and good flavor-producing abilities. KADOYA1 is expected to be used to produce craft beer with a unique flavor.
Thermal aggregation of whey proteins has been the topic of extensive research work. Blocking of disulfide bonds is quite important for the understanding of aggregation mechanism and, specifically, the role of disulfide interchange reaction. In this work, chemical blocking of disulfide bonds by Dithiothreitol (DTT) was compared with physical blocking (at pH 3), when molecules at both conditions were subjected to thermal aggregation at 80℃ for 1 hr. Results indicate differences in molecular properties at the two aggregation conditions. Aggregates that were formed via thermal treatment in the presence of chemical blocking reagents (DTT) produced larger aggregates of spherical, collapsed macromolecules. However, aggregate formed when disulfide bonds were physically blocked - at pH 3- produced smaller aggregates of spherical, wormlike macromolecules.
Acyl ascorbates are ascorbic acid derivatives, which are possibly used as antioxidants in oil systems. The effect of stearoyl ascorbate at different amounts in model cookies containing iron, in terms of lipid autoxidation, was studied. A kinetic model describing the formation and degradation of lipid hydroperoxides (expressed as peroxide value) was developed to compare the antioxidant abilities. Results showed that addition of 25 mg of stearoyl ascorbate to 250 μL of soybean oil resulted in the longest induction time among the tested systems. Additionally, stearoyl ascorbate showed much higher antioxidant ability compared to palmitoyl and behenoyl ascorbates.
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