Basic food engineering studies have been carried out on extraction of food materials using subcritical water and chromatographic separation of sugars. An equation for describing the apparent distribution coefficient of a sugar to a cation-exchange resin was proposed. The equation allowed us to estimate the equilibrium constant for ligand exchange between various kinds of sugars and counter-ions, and the swelling pressure of the resin. Two mathematical models were proposed for calculating the concentration profiles of solutes in a simulated moving-bed chromatograph, by which two solutes can be continuously separated. A criterion for achieving good separation was also determined. Materials having functionalities such as emulsifying or antioxidative ability could be extracted from unused bioresources by their subcritical water treatment. Many reactions would occur during the treatment. Therefore, catalytic properties of subcritical water were kinetically investigated for decomposition or degradation of various compounds.

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The distribution of phospholipids (PLs) during the gelatinization process of wheat flour suspension was investigated using a rapid visco analyzer. The amount of thermally extracted phospholipids (PLs) in boiling water with water-saturated n-butanol was higher than that extracted at room temperature and in the state of wheat flour suspension. Especially, the amount of thermally extracted lysolecithin (LPC) was 4 to 5 times higher than that extracted at room temperature. Conversely, using gelatinized liquid of wheat, the amount of LPC extracted at room temperature (RT-LPC) was higher than that of thermally extracted LPC (HOT-LPC), and the amount of thermally extracted LPC was almost constant. However, after the peak of viscosity, the amount of HOT-LPC was again higher than that of RT-LPC when the viscosity decreases. The distribution of other LysoPLs was similar to that of LPC. In the gelatinization state, the palmitic acid composition of HOT-LPC was 56.5% and that of RT-LPC was 37.2%. The linoleic acid composition of HOT-LPC was 28% and that of RT-LPC was 51.9%. On the other hand, although n-acyl phosphatidylethanolamine (AcylPE) and n-acyllysophosphatidylethanolamine (AcylLPE) were extracted only at RT in the flour and during the gelatinization process, after the peak viscosity, these phospholipids were extracted at both RT and HOT when the viscosity decreases. These results indicate that the distribution of LPC, AcylPE and AcylLPE change during the gelatinization process of wheat flour suspension.

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Viscoelasticity and air-bubble parameters were measured to estimate the texture of bread from Sudachi (air-bubble structure) and the relationship was quantified. A sampling size in cross-sectional surfaces of the slices of bread was optimized to quantify relationships between viscoelasticity and air-bubble parameters of bread. As a result, a cubic sample (20×20×20mm) cut from the slices of bread was determined to be used to measure the viscoelasticity, and its central square area (10.2×10.2mm) was determined to be tested to measure the air-bubble image. Four viscoelastic moduli (instant elasticity, retardation elasticity, retardation viscosity, and permanent viscosity) of the bread samples were calculated by applying four-element Voigt model to the data acquired by creep test. Additionally, four bubble parameters (average air-bubble size, average air-bubble perimeter, the number of air-bubbles in a unit area, and the ratio of bubble area to the whole area of the bread samples) were also calculated by applying a bubble detection method using image processing on the data taken by an image scanner. Finally, significant correlations (r>0.59, p<0.05) were found between instant elasticity, retardation elasticity, permanent viscosity and the ratio of bubble area (the ratio of bubble area to the whole area). This indicates that crumb hardness increases as the ratio of air-bubble area increases.

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We have investigated the particle size, degree of circularity, extensibility, flowability and foaming properties of matcha in terms of the milling method. Matcha samples were ground by a stone-mill, a ball-mill and a jet-mill, and the matcha ground by a ball-mill was classified by 10μm diameter into fine and coarse matcha with an airflow-type classifier. The median diameter of the matcha ground by a stone-mill and a ball-mill and a fine matcha was 15-20μm, and that of a matcha ground by a jet-mill and a fine matcha was under 5μm. The degree of circularity of a matcha ground by a jet-mill was higher than that by other milling machines. A fine matcha and the matcha ground by a jet-mill showed a higher extensibility compared to others. Matcha ground by a jet-mill showed good flowability compared to a fine one. A fine matcha showed a good foaming property compared to a coarse one. Therefore, we expect the improvement of utility since matcha ground by a jet-mill showed a predominant flowability, extensibility and foaming property because of its small diameter and high degree of circularity.

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Earl's-type melon fruits were stored in air and under CA (5% O₂, 15% CO₂ and 5% O₂+15% CO₂) at 28°C in the dark. The amount of respiration of Earl's-type melon fruits stored under CA was retarded in comparison with that in air. Under the condition of 5% O₂ and 5% O₂+15% CO₂, ethylene production was significantly suppressed, softening, water-soaked appearance and stalk wilting in Earl's-type melon fruits were inhibited. However, under the condition of 15% CO₂ ethylene production slightly decreased and after-ripening continued as well as in air during storage. Therefore, low O₂ or the condition of the combination of low-concentrated O₂ and highly-concentrated CO₂ were considered to be effective to keep the quality of Earl's-type melon fruits, but the condition of highly-concentrated CO₂ was not considered to be beneficial.

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The objective of this study was to clarify the components affecting the quality of cherry tomatoes grown on commercial organic farms and conventional ones in summer and autumn. Sixteen pairs of conventional cherry tomato samples and organic ones were taken from 16 farms and the content of ascorbic acid, lycopene, β-carotene, sugars, citric acid, free amino acids and the production of ethylene were analyzed. The organic cherry tomatoes contained significantly high amount of ascorbic acid and lycopene, but produced significantly low rate of ethylene compared to the conventional ones.

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[in Japanese]

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