The 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay has proven to be valuable in the quality assessment of natural antioxidants. The effect of different solvent systems on the DPPH radical scavenging assay was examined using 16 polyphenols. The DPPH values of catechol and pyrogallol compounds determined with a Tris-HCl buffer/EtOH system were higher than those determined with a MeCN system. These results suggest that the DPPH values determined in the Tris-HCl buffer/EtOH system result from the reactivation of the catechol and pyrogallol moieties of the antioxidants. We also found that the DPPH values determined in the Tris-HCl buffer/EtOH system exhibit a higher correlation with Ferric Reducing Antioxidant Power (FRAP) values than those determined in the MeCN system. As the DPPH assay for the Tris-HCl buffer/EtOH system reflects the ferric-reducing capacity of the antioxidants as polyphenols, this system appears to be an appropriate buffer system for the DPPH assay. The effect of the volume ratio of the Tris-HCl buffer and EtOH in the system on the DPPH values was examined. The DPPH values for the catechol and pyrogallol derivatives increased with the volume ratio, suggesting that the buffer ratio is a key factor to determine the values in this assay. We thus conclude that the buffer system selection in the DPPH radical scavenging assay is a critical factor for the quality assessment of natural antioxidants used as food additives.

　Fermented wheat starch (FWS) is produced from starch as a byproduct of gluten manufacture. FWS is used in the traditional Japanese sweet, kuzu-mochi, which originates from the Edo period. The elastic but non-sticky texture of kuzu-mochi is attributable to the properties of FWS. To elucidate the characteristic properties of FWS, the comparison morphology, and physicochemical and pasting properties of starch with/without fermentation treatment were examined. Fermentation of wheat starch (WS) led to a decrease in the abundance of small starch granules, as small starch granules formed large aggregates. The degrees of damaged starch and amylose content in FWS were lower than those in unfermented WS. The λ_max of the iodine absorption spectrum of FWS was blue-shifted relative to that of WS. The maximum and final viscosities of FWS, and its consistency in the rapid visco analyzer viscogram were lower than those of WS. These results revealed that fermentation endows starch with low viscosity and the ability to retard retrogradation.

　This study investigated fruit texture and taste in Shinano Gold apples from Nagano Prefecture that had been stored for five months. Measurements included fruit firmness, sensory softness, and mechanical indentation. Softness measurements non-destructively evaluated the texture of fruit flesh from outside its skin. Mechanical indentation tests depended on the reaction force from inside the fruit following Newton's third law. Indentation tests also provided information about internal fruit quality. Measurements of flesh firmness and sensory softness decreased with storage time and significantly correlated with each other (r＝0.916, p＜0.05). Results suggested that mechanical indentation tests are useful for assessing the taste of apples.

　In this study, four wheat cultivars — Hanamanten (extra strong flour), Yumekaori (hard flour), Satonosora, and Norin. 61 (medium flour) — were assessed by western blotting, enzyme activity assays, and SDS-PAGE for determining the effect of protein disulfide isomerase (PDI) expression and activity on disulfide bond formation during wheat grain ripening. In all cultivars, enzyme assays indicated that PDI activity begins to increase rapidly in the middle of grain ripening. Twenty-five days after anthesis, the highest PDI activity was recorded for Yumekaori (3.3 U/grain), whereas Satonosora and Norin.61 cultivars displayed lower PDI activities of 1.4 and 1.2 U/grain, respectively. PDI expression also increased in the middle of wheat grain ripening for all cultivars. In addition, both the high-molecular-weight glutenin (HMW-GS) and the low-molecular-weight glutenin (LMW-GS) shifted to a higher molecular weight when PDI was activated, particularly in the hard flour. The Yumekaori cultivar showed the highest PDI activity and a decrease in SDS-soluble proteins 30 days after anthesis, which suggests that the SDS-soluble proteins could be transferred to the insoluble fraction.