Potato starch waste residue (PSR) is an unused agricultural resource that is rich in dietary fiber. We focused on a water-soluble polysaccharide contained in the fiber of PSR. We investigated the conditions for efficient extraction of a potato water-soluble polysaccharide (PP), the physical properties of the obtained PP, and its application as a stabilizer for acidic milk beverages. PP was obtained from PSR with a high extraction yield of 53% by heating at 110°C for 1.5 hours at pH4.5. The obtained PP had an average molecular mass of 1.9 million (g/mole), and consisted of galacturonic acid, arabinose, rhamnose, galactose, and glucose. The aqueous solution showed intermediate viscosity characteristics between high-methoxyl-type citrus pectin and soybean polysaccharide. It rapidly thickened at a pH lower than pH4, and showed properties similar to citrus pectin as it thickened and formed a gel when sucrose was added to the PP solution to make the concentration more than 30%. The molecular image obtained by a scanning probe microscope showed a multi-branched structure similar to that of soybean polysaccharide. Furthermore, the PP appeared to function as a dispersion stabilizer as it suppressed the aggregation and precipitation of milk proteins under the weakly acidic condition of pH4.2 to pH5.0.

‘Ruby Roman’ grape (Vitis Labruscana Bailey) juice was concentrated from 14.6 to 23.0 Brix by progressive freeze-concentration (PFC) with a closed circulation flow system. The distribution of organic acids and flavors was measured, and no substantial changes were observed in the component profiles before and after PFC concentration. The PFC-concentrated ‘Ruby Roman’ grape juice was fermented to produce Ruby Roman wine, in which the obtained ethanol concentration was as high as 14.5vol%. Thus, a sufficient alcohol level can be obtained without chaptalisation by using PFC concentration. Following fermentation, acetic and succinic acids increased in the organic acid distribution. In the flavor distribution, some components in the original juice disappeared, while fermentation products such as ethanol, isoamyl acetate, isoamyl alcohol, ethyl octanoate, phenethyl alcohol, octanoic acid, and decanoic acid newly appeared. Overall, the Ruby Roman wine retained sufficient amounts of flavors from the original juice. The present results suggest the possibility of producing a new-type of Ruby Roman wine, not presently available on the market.

To elucidate the effect of processing methods on the iron content of hijiki produced from the west coast of the Izu Peninsula, we analyzed the iron content and tested its correlation with the boiling time in an iron pot or the boiling and holding times in the iron pot. The iron content of the dry material of hijiki averaged 112.0±50.2 mg/100 g dry matter, and the iron content of the products processed in the iron pot was higher than that of the dry material, averaging 112.0±50.2 mg/100 g. There was no correlation between the iron content of the products and the boiling time, whereas a positive correlation was found between the boiling and holding times in the iron pot. Based on our findings, hijiki products from the west coast of the Izu Peninsula that were processed in an iron pot had a higher iron content than other sources of hijiki, and it was due not only to the length of the boiling time in the iron pot, but also the length of the holding time.

The purpose of this study was to analyze the properties of wheat flour and rice flour that are used in the production of wheat flour and rice flour blended bread with the addition of acid-soluble wheat protein (ASP), and to examine the optimal additional amounts of sugars and enzymes that can improve the quality of the wheat flour and rice flour blended bread. In the sponge and dough method of bread-making, rice flour was used to replace 40% of the wheat flour, and 10% wheat protein (gluten and ASP) was added to the wheat flour and rice flour. Results of flour analysis confirmed that the rice flour (rice flour for bread and high amylose rice flour) had less damaged starch content than the wheat flour. Also, rice flour particles were smaller than wheat flour particles, and each displayed different viscosity characteristics. In wheat flour and rice flour blended bread, the addition of rice flour, with its low damaged starch content, decreased the amount of maltose produced during the fermentation of the sponge dough when compared to bread made with wheat flour only. Accordingly, the measured amount of gas generated during sponge dough fermentation also decreased. Therefore, when rice flour was used to replace 40% of the wheat flour, 2% maltose was added to the sponge dough to increase the gas amount and improve fermentability. When wheat flour and rice flour blended bread was made in which 40% of the wheat flour was replaced with rice flour, in comparison to the use of rice flour for bread, the use of high amylose rice flour resulted in a higher specific volume, and caving did not occur. When using two α-amylases with different optimum temperatures (50ppm each), it was possible to improve the specific volume of the bread and suppress the degradation of crumb firmness over time. Furthermore, the addition of 150ppm of lipase was effective at preventing the bread from caving, indicating that the addition of appropriate amounts of these enzymes improved the quality of wheat flour and rice flour blended bread.

Wheat flour is added to and mixed with water to hydrate and associate gliadin and glutenin to form gluten. In addition to various minor interactions such as hydrogen bonding and hydrophobic interaction for proper gluten formation, it is acknowledged that disulfide bonds (SS bonds) between cysteine residues are important. Further, in terms of breeding, genes encoding proteins having excellent SS bond-forming ability, represented by Glu-D1d, are critical. There has been much research on endogenous redox substances and enzymes in the mechanism of SS bond formation in the manufacturing process; however, consensus regarding the relationship has not been obtained. Protein disulfide isomerase (PDI, EC 5.3.4.1) is present in the endoplasmic reticulum, and is a molecular chaperone that forms intramolecular (interstitial) SS bonds during protein expression. When PDI forms SS bonds in gluten, it is reduced (PDIred) and loses its oxidizing ability. It is known that oxidative regeneration to oxidized PDI (PDIoxi) by endoplasmic reticulum oxide reductase 1 (ERO1) occurs in vivo, and ascorbic acid (AA) as a dough-improving agent is involved in this regeneration in wheat flour dough. AA is converted to dehydroascorbic acid (DHA) by ascorbate oxidase in the dough. When examining the effect of DHA on PDIred, conversion to PDIoxi progresses efficiently, and since it catalyzes SS bond formation in substrate protein, it is inferred that the dough-improving effect by AA is brought about in cooperation with PDI.