2001 Fiscal Year Final Research Report Summary
Characterizatiion of zinc-chelating compounds in coffee brew
| Project/Area Number |
12480025
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 |
HOMMMA Seiichi Ochanomizu University, Department of Food Science and Nutrition, Professor, 生活科学部, 教授 (50017240)
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| Co-Investigator(Kenkyū-buntansha) |
YORISAWA Aya Ochanomizu University, Department of Food Science and Nutrition, Assistant, 助手
MURATA Masatsune Ochanomizu University, Department of Food Science and Nutrition, Assistant Professor, 人間文化研究科, 助教授 (60210051)
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| Project Period (FY) |
2000 – 2001
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| Keywords | chelating compunds / instant coffee / coffee / alkaline fusion / polyphenols / zinc(II)-chelating / green coffee beans / milk |
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| Research Abstract |
The Zn(II)-chelating compounds were separated from instant coffee by coagulation with ZnCl_2, dissolved in 1 % ammonia, and purified by passage through the columns of the ion-exchangers of Amberlite IRA-410 and IR-120. The Zn(II)-chelating compounds (Ap) were further purified by chromatography on a cellulose column which was developted with a mixture of 1 % ammonia and n-propanol giving six fractions (Ap I 〜VI). Ap-V and Ap-VI were found to be brown powders with zinc, and to be water-soluble. The yield of Ap-V from the instant coffee was 0.2-0.4%. Chemical structure of the active compounds has been investigated by characterizing products formed through such degradative reactions on the Ap-V sample as alkaline fusion (350℃) and alkaline decomposition (250℃) in glycerol. Alkaline fusion of Ap-V yielded about 10 % of ether-soluble compounds, the major ones being low molecular polyphenols such as pyrogallol (2.36 %), pyrocatechol (2.32 %), protocatechuic acid (3.48 %) and p>hydroxybenzoic acid (0.76 %). GC-MS analysis revealed benzoic acid and carbonyl compounds, etc. The chemical structures of another alkaline fusion of Ap-VI gave a different pattern from that of Ap-V for HPLC analysis with UV detection and a similar pattern to Ap-V for GC-MS analysis.
Green coffee beans were found to contain proteins to make complex with Zn(II), and Zn(II)-chelating compounds in coffee brew were different from the proteins. Ap-V and VI compounds of coffee brew were found to be formed by roasting green coffee beans.
Brewed coffee is mostly tasted with or milk cream with fat and protein, and it has been expected that milk products might have some effects to retard metal-chelating activity of coffee. Ap fraction was similarly prepared from instant coffee added with milk as instant coffee, and the prepared ApV showed lower Zn content than that of instant coffee. Milk ingredients may control a metal-chelating activity of brewed coffee by forming coffee-milk complex.
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