1999 Fiscal Year Final Research Report Summary
Mechanism of pressure-induced hardening and optimization for the hardness control of vegetables
| Project/Area Number |
10680140
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
食生活
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| Research Institution | Ochanomizu University |
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Principal Investigator |
KASAI Midori Ochanomizu University, Faculty of Human Life and Environmental Science, Associate Professor, 生活科学部, 助教授 (10262354)
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| Co-Investigator(Kenkyū-buntansha) |
香西 みどり お茶の水女子大学, 生活科学部, 助教授 (10262354)
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| Project Period (FY) |
1998 – 1999
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| Keywords | pressure treatment / hardening / cell wall / pectins / metal ions / water content / Japanese radish |
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| Research Abstract |
It has been reported that vegetables, fruits and beans are hardened by low temperature blanching, drying, addition of salt and storage, and that their softening during cooking at 99.5℃ after these pretreatments are suppressed. We have found that such root vegetables as Japanese radish are hardened by the application of a high pressure of several-hundred Mpa, and that this hardening process continues even after the pressure has been released. The cell membranes were destroyed by the pressure treatment, and a decrease in the degree of esterification of pectins followed. The mechanism for this pressure-induced hardening could not be explained only in terms of the decreased degree of pectin esterification. It was suggested that some other factors contributed to the hardening. The hardness was increased by the pressure treatment and by standing for up to 11 hours after the pressure had been released. A decrease in pH, derease in water-soluble protein, and increase in alkali-insoluble protei
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n of the pressurized samples were observed. The quantities of pectin and cellulose were not changed by pressurization or by standing after the pressure had been released. Hemicellulose I and slightly decreased, whereas hemicellulose II was increased. Since hemicellulose II has stronger hydrogen bonds than hemicellulose I, it has been suggested that the increase in hemicellulose II would lead to reinforcement of the strength of the cell wall. The concentration of calcium ions increased in pectin and decreased in hemicellulose I and II, while the concentration of potassium ions decreased in hemicellulose II. Magnesium ions existed mainly in pectin, and their concentration was not changed by pressurization or by standing after the pressure had been released.
The mechanism for hardening under a pressure of several-hundred Mpa is proposed to lead to a loss of integrity of the cell membrane. This allows the diffusion of intracellular potassium ions into the cell walls, and is followed by the enzymic demethylation of pectins and the subsequent formation of bridge bonds between the calcium ions and free carboxyl groups. Protein denaturation by pressurization causes an increase in insoluble protein. A mass transfer process followed by collapse of the cell membranes due to the pressure treatment are considered to cause hardening during standing by changing the interaction among tissue components such as pectin, hemicelluloses and proteins. Less
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