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Effect of the polysaccharide from leaves of Corchorus olitorius L. (PLC) on the freeze-thaw (FT) stability of corn starch gel was studied. PLC was incorporated into the starch gel at 0.7% and total solid was adjusted to 6.0%. The syneresis was measured by the centrifugal-filtration method and, as a result, addition of PLC reduced effectively the syneresis of the starch gel even after 5 FT cycles, which was less than one third that of the normal starch gel. The rheological changes of the starch/PLC gel during the FT treatments were evaluated while the gel remained on the rheometer plate. The starch/PLC gel had less significant changes in the rheological parameters during the FT cycles than starch/guar gum or xanthan gum gel systems. SEM images showed that PLC stabilized the gel matrix surrounding pores, which would contribute to both a lower syneresis production and a higher stability in the rheological behavior at FT.

Citrus pectin was modified with glycine, glycine methyl ester, or glycylglycine by the use of intramolecular associations in polar organic solvents. The modified pectins except glycine methyl ester significantly improved its dissolution in water, compared with unmodified pectin. The pectin modified with glycylglycine was the most soluble into water and was not influenced by pH range from 4.6 to 7.6 and ionic strength range from 1 mM to 50 mM phosphate buffer (pH 5.1), while the dissolution of the unmodified pectin decreased as pH and ionic strength increased. The required time at 45 °C at 95% hydration rate in the glycylglycine-modified pectin (2%, w/v) was toward 58% that in the unmodified pectin. In glycylglycine-modified pectin, the hydration rate was dependent on the bound amounts of the modifying agent to pectin. The potentiometric titration curves revealed that the glycylglycine-modified pectin would bear more negative charge than the unmodified pectin. From analysis of the water adsorption isotherms, the Brunauer–Emmett–Teller C constant as an index of hydrophilicity in the glycylglycine-modified pectin was 1.23-fold and 1.87-fold, respectively, higher than those in the unmodified and glycine methyl ester-modified pectins. These results suggested that the dissolution of pectin into water was preferably related to the net charge and the surface hydrophilicity in pectin molecules.

Viscous hydrocolloid from leaves of Corchorus olitorius L. was fractionated with ammonium sulfate solution (50%, w/v) followed by the stepwise extraction with distilled water. The yield of the hydrocolloid was 4.5% (w/w) based on dry material. Ash, protein, moisture and total sugars were 3.4, 5.3, 12.3 and 83.8% based on dry-material, respectively. The hydrocolloid consisted of mainly uronic acid and the weight ratio was approximately 90% of total sugars. When the molecular weight distribution was checked by size-exclusion chromatography, the hydrocolloid showed a wide uronic acid peak with a molecular weight of 940 kDa. The viscoelastic properties of the hydrocolloid were examined by low-amplitude oscillatory measurements and the hydrocolloid exhibited gel-like character at the concentration higher than 0.5% (w/w). Viscosity of the hydrocolloid surpassed other food hydrocolloids such as guar gum and locust bean gum at the same condition (0.25∼1.0% [w/w], 25 °C). When the hydrocolloid was heated over 60 °C (∼100 °C), an irreversible increase in viscosity was observed, suggesting the conformational change of the polysaccharide molecule.

Pectins were extracted from the peel of Citrus unshiu Marcovitch × C. nobilis Loureiro (Kara mandarin) in the presence of citric acid at different pH and temperature. Treatment with citric acid, particularly, at neutral pH gave a significant increase in viscosity. The citric acid treatment at high temperature led to decreased viscosity although the viscosity remained higher than that of untreated pectin. Pectin methylesterase activity was inhibited at high citric acid concentrations. The increase in viscosity of treated pectin was proportional to the amounts of citric acid bound to pectin. The pectin with citric acid treatment had a low degree of methylation (8.4%) and a high distribution (50 to 2000 kDa) of molecular mass than untreated pectin. Analysis of chemical composition showed that the pectin with citric acid treatment contained lower protein and galacturonic acid, and higher neutral sugars, particularly, galactose than the untreated pectin. The citric acid treatment at neutral pH prior to extraction is an attractive procedure for low methoxy pectin without lowering its molecular weight.

Hydrocolloid from leaves of Corchorus olitorius was fractionated with ammonium sulfate (50%, w/v) and extracted with distilled water. The yield of the hydrocolloid was 6.0% (w/w) based on dry material. The contents of total carbohydrate, anhydrouronic acid, ash, protein, and moisture of the hydrocolloids were 62.2%, 35.3%, 13.3%, 5.5%, and 16.1% (w/w), respectively. Degree of esterification of 19.4% was calculated assuming that the methoxyl groups were attached to only anhydrouronic acid. When the molecular weight distribution was checked by size-exclusion chromatography on Sepharose CL-4B, the hydrocolloid gave a single peak with a molecular weight of 1860 kDa. The rheological behavior of mixed gels made from κ -carrageenan and the hydrocolloid at a total hydrocolloids concentration of 1% (w/w) was investigated by gel strength measurement. Then it was found that the hydrocolloid exhibited synergy with κ -carrageenan in relation to gel strength.

The dye-sensitized solar cells (DSCs) were assembled by using natural carotenoids, crocetin (8,8′-diapocarotenedioic acid) and crocin (crocetin-di-gentiobioside), as sensitizers and their photoelectrochemical properties were investigated taking a presence or absence of carboxylic group in the dye molecule into consideration. In these carotenoids, crocetin that has carboxylic groups in the molecule can attach effectively to the surface of TiO2 film so that it performed the best photosensitized effect resulting in the short-circuit photocurrent with 2.84 mA under irradiation of 1.0 cm2. On the other hand, crocin that has no carboxylic group in the molecule showed lower photoelectrochemical performance because of its lower affinity to the surface of TiO2 film. These results indicate that it is possible to apply carotenoid as sensitizers for DSCs at the presence of effective function groups.

Antioxidants were extracted from Japanese pepper ( Zanthoxylum piperitum DC.) fruit and characterized. The antioxidant activity of the methanol extract from Japanese pepper fruit was found to be equal to that of α-tocopherol and stable under heat treatment. The main compounds that gave a significant antioxidant activity from the methanol extract were identified to be hyperoside (quercetin-3- O -galactoside) and quercitrin (quercetin-3- O -rhamnoside) as determined by HPLC, mass spectrometry, UV/Vis spectroscopy, and TLC. Radical-scavenging activities of hyperoside and quercitrin from Japanese pepper fruit were evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. As a result, hyperoside and quercitrin scavenged DPPH radical strongly with IC 50 values of 16 and 18 μM, respectively. These observations show the presence of strong antioxidants, namely hyperoside and quercitrin in Japanese pepper fruit.

We examined water conditions on a latex surface by using differential scanning calorimetry (DSC). The DSC results indicated that three kinds of water, (free water, freezable bound water, non-freezing water) exist on the latex surface. From the DSC results for several polystyrene latices, it was known that behaviors of freezable bound water, and non-freezing water were affected by initiator, surfactant, and also by co-polymerization of hydrophilic monomer. Further, according to the DSC results of carboxylated latex, it was known that water conditions were related to latex properties, (pH, solid content, latex viscosity). Furthermore, we found that latex viscosity was determined by the amount of free water. These results indicated that water conditions on a latex surface were influenced by condition and localization of hydrophilic substances.

A gene encoding β-glucosidase was cloned from a thermophilic anaerobe strain NA10 into Escherichia coli . The 4.6 kb of Hin dIII fragment was shown to direct the synthesis of β-glucosidase. A homologous DNA sequence was found to be present in strain NA10 by Southern blot analysis. The β-glucosidase was purified from the recombinant E. coli . The molecular weight of the enzyme was estimated to be 50.1 kDal using SDS-polyacrylamide gel electrophoresis. The enzyme was heat stable; the optimum pH and temperature were 5.5 and 85°C, respectively. The enzyme could hydrolyse low molecular weight β-1,3 and β-1,4 glucans. The β-glucosidase was produced in the cytosol of the recombinant E. coli (7–20% of total protein), without fusion to any E. coli promoter sequences.