Ability of scavenging reactive oxygen species (ROS) in yeast Candida tropicalis pK 233 was investigated. Ethanol causes pseudohyphal development in C. tropicalis pK 233 in the absence of myo-inositol. Antioxidative ability of samples was investigated through of scavenging ability for DPPH and O-2. Oxidation-reduction potential (ORP) of the culture without ethanol decreased with cell growth until 24h and then gradually increased, while that with 4% ethanol decreased with cell growth until 48h and remained at the decreased level. The cell culture grown with 4% ethanol showed strong scavenging ability for DPPH radical and O-2, compared to that of without ethanol ; this scavenging ability of ROS by the culture with 4% ethanol increased with cultivating time until 120h. The cell culture grown with both ethanol and inositol was also able to scavenge ROS in a similar manner to that grown with 4% ethanol alone ; yeast cells could be grown under these conditions. Thus, ethanol appears to enhance antioxidative ability in C. tropicalis pK 233 regardless of the presence of inositol and cell morphology.

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Ultrasonic pulse Doppler profiling, rheology, and sensory evaluation were used to determine the effects of gel amount and mastication on the velocity of agar and gelatin gels passing through the pharynx as well as the physical characteristics following mastication. Gel samples (3, 6, 9, and 12g) were masticated 5, 10, 30, or 50 times, respectively. The hardness of agar and gelatin gels decreased as gel amount decreased and mastication increased. Sensory evaluation showed that both agar and gelatin gels became easier to swallow as gel amount decreased and mastication increased. Higher maximum velocities were observed for 9- and 12-g agar gel samples masticated 5 times and for 3- and 6-g gelatin gel samples masticated 50 times. The increase in maximum velocity seen for the agar gel may be due to formation of a large bolus that passes through the pharynx after mastication, compared to that of gelatin gel, which forms a sol.

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Carbon dioxide emission as well as food consumption was compared based on the National Nutrition Survey data for 2002 and 1970. The food self-sufficiency rate was 40% and 60% in 2002 and 1970, respectively. In 1970, the dominant meal pattern was based on a intake of rice, miso soup, and pickles irrespective of the Japanese, Chinese, or Western food items. In 2002, the consumption of rice was greatly reduced while the consumption of meat, fish, vegetables, and fruits was increased both in quantity and variety. An ideal protein-fat-carbohydrate balance was achieved in 1970, while protein and fat intake was increased and carbohydrate intake was reduced in 2002. Carbon dioxide emission calculated from the 1970 diet was 907g/day/person, which increased by about three times to 2743g/day/person in the 2002 diet. This increase achieved the goal of a reduction in carbon dioxide of 1kg/day/person recommended by the Ministry of the Environment.

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The characteristics of sulfide precursor/components in the bulb of Allium ampeloprasum L. (jumbo leek) were compared with those in other Allium species : A. cepa L. (onion), A. sativum L., and A. ampeloprasum L. (broadleaf wild leek). Sulfide components from jumbo leek were analyzed by gas chromatography/mass spectrometry (GC-MS) using spectral analysis. The contents of sulfides from jumbo leek were dimethyl disulfide (M-SS-M ; 1.7mg/kg wet wt), methyl propenyl disulfide (M-SS-Pe ; 15.7mg/kg), propyl propenyl disulfide (P-SS-Pe ; 7.5mg/kg), dimethyl trisulfide (M-SSS-M ; 21.5mg/kg), methyl propyl trisulfide (M-SSS-P ; 10.0mg/kg), and methyl propenyl trisulfide (M-SSS-Pe ; 14.0mg/kg). The composition of alk(en)yl cysteine sulfoxide (alk(en)yl CSO) from jumbo leek was S-methyl cysteine sulfoxide (MCSO ; 4.1±0.5mg/kg wet wt), S-propyl cysteine sulfoxide (PCSO ; 0.1±0.3mg/kg) and S-propenyl cysteine sulfoxide (PeCSO ; 2.4±0.4mg/kg). The total content was the same as those of A. cepa L. and A. ampeloprasum L. Moreover, N-(γ-glutamyl)-S-(E-1-propenyl) cysteine (Glu-PEC, 87mg/kg wet wt) which is a alk(en)yl cysteine precursor from jumbo leek, was detected. Therefore, the lower odor producing mechanism in jumbo leek was determined to be the same as that in leek. That is, the substrate precursor Glu-PEC is converted to S-E-1-propenyl cysteine (PEC) by γ-glutamyl transpeptidase. Then, PEC is oxidized to PeCSO, a substrate for allienase. PeCSO, another naturally present alk(en)yl CSO, is converted to S-alk(en)yl acid by allinase(C-S lyase), followed by sulfide production via formation of the dialkyl thiosulfinates.

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Collapse of potato tuber during cooking is caused by cell separation. This phenomenon is thought to be affected by intrinsic polygalacturonase (PG), which is involved in the decomposition of pectin. To determine the effect of PG on potato collapse, the pectin amount, hardness, and PG activity of potato after boiling were analyzed. A strong correlation was found between PG activity and both pectin amount and hardness. In addition, the degree of potato collapse after boiling increased with increases in potato density.

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Eating quality and physicochemical properties of commercially milled rice were examined to develop a model for predicting eating quality of commercially milled rice from physicochemical properties. Prediction accuracy of appearance, hardness and cohesiveness of commercially milled rice from physicochemical properties was low. Translucency, 1000-kernel weight, bulk weight and L₆ (amount of compression) were selected as potential variables of a multiple linear regression model for predicting overall flavor. The validation statistics (coefficient of determination : r²) of the model was 0.41, indicating that the accuracy of the model was limited due to the small range of physicochemical properties and eating quality of rice produced and distributed in Japan. When rice samples were divided into two qualitative rice groups, samples with high eating quality and samples with low eating quality, the probability for correct classification was 73% using the model developed in this study. Thus, this model for predicting eating quality of commercially milled rice has potential for use in classifying rice samples by taste.

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The performance of near infrared method was examined for nondestructive determination of major components of potato (Solanum tuberosum) and pasting viscosity properties. Good calibration models with reasonable accuracy for moisture, carbohydrate, protein and amylase contents and Rapid Visco Analyzer (RVA) parameters were determined using partial least square (PLS) regression. The standard error of prediction (SEP) was 0.87% for moisture, 0.95% for carbohydrate, 0.6% for amylose, 0.15% for protein, as well as 30RVU (the default Rapid Viscosity Unit) for peak viscosity, 34RVU for final viscosity, 24RVU for breakdown, and 22RVU for setback. The calibration model for ash content was not significant ; further research is needed to improve calibration for ash content. Thus, near infrared spectroscopy is a useful method to nondestructively measure the major components and pasting viscosity of intact potato.

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[in Japanese]

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