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The distribution coefficients, K app , of non-electrolytes of different molecular masses on a tapioca starch gel were measured at a temperature range of 25 _ 60℃. The swelling pressure of the gel was estimated from the coefficients at each temperature, and was observed to increase from 1 to 3 MPa with a temperature increase from 25 to 50℃.The swelling pressure, however, decreased at 60℃. The decrease was ascribed to the gelatinization of tapioca starch, which was observed using differential scanning calorimetry. The temperature dependency of the swelling pressure suggested a significant effect of gelatinization on the distribution equilibrium of a solute on the starch gel.The experimentally observed K app values of electrolytes (0.5 to 0.8) were lower than the values calculated using the swelling pressure and specific molecular volumes of the electrolytes. This suggested the involvement of another factor, such as an electrostatic interaction, in the distribution of electrolytes on the gel.

Optimum conditions for chromatographic separation, at 30℃, of galactose, tagatose, and talose were determined by investigation of the effects of the counter-ion form of cation-exchange resin and the ethanol content of eluent on the distribution coefficients of the monosaccharides onto the resin. Resin in the K + form with a divinylbenzene content of 8% was found to be most suitable for the separation. The distribution coefficients of all the solutes on the resin were increased as the ethanol content of eluent increased.Keywords: cation-exchange resin, distribution coefficient, tagatose IntroductionRare sugars are saccharides that occur in only small amounts in nature, and some of them have attracted attention due to their physiological functionality. Xylitol is one such rare sugar, which has an anticaries effect (Söderling et al., 1989) and is contained in gum as a sweetener. d-Psicose, which is an epimer of d-fructose at the C-3 position, is very low in calories and has a beneficial effect on insulin resistance (Matsuo et al., 2002; Hossain et al., 2012).d-Allose, which is an epimer of d-glucose at the C-3 position, has demonstrated preventative effects in ischemia reperfusion injury and hyperpiesia. However, rare sugars are generally very expensive. The high cost restricts investigation of their physiological and textural functionalities. Because of this, the development of effective mass production processes for rare sugars is desired to promote these investigations and achieve industrialization of the production process.Enzymatic methods for producing rare sugars (Takeshita et al., 2000; Granström et al., 2004; Morimoto et al., 2006) have been reported, in addition to a method using anion exchange (Takamine et al., 2009). We reported that isomerization of the common sugar d-galactose to d-tagatose and d-talose, which are rare sugars, was promoted in subcritical aqueous ethanol (Gao et al., 2015). An enzymatic method has also been developed for the production of d-tagatose (Kim et al., 2003). Isomerization in a subcritical fluid would be expected to be more effective than in conventional methods because of a higher reaction rate at higher temperature.d-Tagatose, which is a C-4 epimer of fructose, shows promise as replacement for sucrose and as a therapeutic agent against type 2 diabetes and obesity (Levin et al., 1995; Lu et al., 2008).Because isomerization of d-galactose produces a mixture of unreacted substrate and the products d-tagatose and d-talose, a separation process is required to obtain the desired product, d-tagatose. Ligand-exchange chromatography using cationexchange resin has been commonly used in saccharide separation due to the difference in complex formation or affinity between the counter-ion of the resin and the saccharides (Goulding, 1975; Caruel et al., 1991; Stefansson and Westerlund, 1996). Because water is used as an eluent, the chromatographic separation of saccharides is suitable for industrial purposes. The type of counterion and the divinylbenzene (DVB) content of the resin...

Defatted rice bran was treated at 230℃ for 5 min with distilled water or 40% (v/v) acetone to produce the corresponding extracts. Acetone-soluble substances were fractionated from the extracts. The antioxidative activities against 1,1-diphenyl-2-picrylhydrazyl, hydroxyl and peroxyl radicals, and the hypochlorite and peroxynitrite ions of the extracts and acetone-soluble substances were examined, and the activities were comprehensively characterized using the 5-axe cobweb chart. The 40% acetone extract exhibited higher activity than the water extract. Fractionation of acetone-soluble substances from extracts increased activity. The acetone-soluble substances from the extract with 40% acetone exhibited the highest activity among the extracts and acetone-soluble substances.

INTRODUCTIONSeasoning or flavoring of foods is an important cooking operation. The distribution equilibrium of a seasoning between the cooking ingredient and liquid preparation determines the final concentration or content of the seasoning within the cooking ingredient, and the seasoning rate is controlled by the diffusion of the seasoning compound into the ingredient.Food consists of a variety of polymers such as starches, proteins, and alginates, which are the main constituent polymers in rice, meat, and brown seaweed, respectively. 1) These polymers are not similar in their chemical or electrical properties. Starches are comprised of glucose and are electrically neutral, while proteins are comprised of amino acids and are amphoteric and alginates are comprised of uronic acids 2) and are anionic. Food polymers can form gel-like matrices during the cooking process after water addition or rehydration and then exhibit different properties. Starch, protein, and alginate gels are regarded as size exclusion resins, amphoteric-ion exchangers, and cation exchangers, respectively. On the other hand, although most substances used for seasoning food are low molecular-weight compounds, their chemical properties vary. Sucrose, sodium chloride, and acetic acid are typical seasonings used to enhance sweet, salty, and sour tastes, respectively. Sucrose is a non-electrolyte, sodium chloride is a strong electrolyte, and acetic acid is a weak electrolyte. Moreover, most bitter compounds are hydrophobic. 3) As a result of these varied chemical properties, various kinds of interactions, such as size exclusion, electrostatic, and hydrophobic interactions, occur between the food matrix and seasonings during the cooking process. In order to establish reasonable cooking processes, an understanding of these interactions is required. Among the possible interactions, distribution of non-electrolytes into an electrically neutral matrix such as starch gel seems to be the most straightforward, and this type of interaction is examined in this study.The swelling pressure of food matrix or gel plays an important role in the distribution of non-electrolytes into the matrix or gel. 4) Pressure during cooking would be also an important factor affecting the distribution of seasonings during preparation of flavored rice. Rice grains differently rehydrated and swelled 5,6) However, the swelling pressure of rehydrated rice grains has not been estimated. In this context, we estimated swelling pressures of two cultivars of non-glutinous rice and two cultivars of sticky rice based on our previous study where the swelling pressure of starch gel was estimated from the distribution coefficients of non-electrolytes having different molar volumes. 4) MATERIALS AND METHODS Materials.Non-glutinous rice cultivars (called Uruchi ), Koshihikari and Yumepirika, were harvested in Shiga and Hokkaido, respectively in 2013; sticky rice cultivars (called Mochi ), Habutaemochi and Kitayukimochi, were also harvested in Shiga and Hokkaido, respectively, in 2013. All rice ...