2007 Fiscal Year Final Research Report Summary
Milk Lactoperoxidase to Control Undesirable Microorganism in Food
| Project/Area Number |
17580111
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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 |
Food science
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| Research Institution | Kagawa University |
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Principal Investigator |
HAYAKAWA Shigeru Kagawa University, Faculty of Agriculture, Professor (50126893)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Food / Safety / Carrot juice / Lactoperoxidase / Salmonella / Antimicrobial activity |
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| Research Abstract |
Lactoperoxidase (LPO) found in milk catalyzes the oxidation of thiocyanate at the expense of hydrogen peroxide to generate short-lived species such as hypothiocyanate radical, showing antimicrobial activity against food deteriorative bacteria. The aims of the present works were to develop the systems for the useful application and improve the LPO system for the effective inhibition of bacteria growth.
The combination of LPO system and glucose oxidase system was built up and the optimum condition to inhibit Salmonella enteritidis was found as follows. LPO 4.5 U/ml, glucose 0.2%, glucose oxidase 0.05 U/ml and KSCN 10 ppm.
Antimicrobial activity of LPO system can be disturbed by protein with free thiol group and high concentration of sugar. The mechanism of the inhibition of antimicrobial activity was elucidated by model system using papain and cysteine. The thiol groups in papain and cysteine were effectively oxidized by LPO system at a concentration of 4.5 U/ml. The moderate amount of food components such as 2-3% salt, protein and cream, and 20% of sucrose effectively inhibited the oxidation of thiol group in papain and cysteine. The enhancement of the concentration (5-10 times) of LPO made precede the oxidation reaction.
Polyphosphate (0.01-0.5%) enhanced the antibacterial effects of the system in tomato juice and chicken skin extract, respectively. LPO system worked well in carrot juice and some components in carrot showed the hurdle effect for the antimicrobial activity.
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