Effect of roasting on properties of the zinc-chelating substance in coffee brews.
ApV is a brownish polymer with zinc-chelating activity in brewed coffee. We investigated in this study the effects of roasting on the zinc-chelating, reducing, and antioxidative activities of ApV from light-, medium-, and dark-roasted coffee. We also discuss the effect on the zinc-chelating activity of adding milk to the brewed coffee. The chelating activities of ApVs were evaluated by the tetramethyl murexide method. As the intensity of roasting increased, the yield of ApV increased, and the brown color and molecular weight of ApV respectively became darker and higher. Increasing the degree of roasting also decreased the zinc-chelating activity of ApV. The reducing activities of ApVs estimated by the indophenol method were stronger than those of ascorbic acid. Both the antioxidative activity estimated by the ABTS assay and the reducing activity of ApV increased with roasting. When milk was added to instant coffee and its ApV was prepared, the zinc-chelating activity of ApV was not changed.
Wen
Xu
X
Department of Nutrition and Food Science, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan.
Enokizo
Akiko
A
Hattori
Harumi
H
Kobayashi
Satiko
S
Murata
Masatsune
M
Homma
Seiichi
S
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D000975:Antioxidants / Q000032:analysis; D052160:Benzothiazoles; D002614:Chelating Agents / Q000032:analysis* / Q000737:chemistry*; D003069:Coffee / Q000737:chemistry; D005419:Flavonoids / Q000032:analysis; D005511:Food Handling / Q000379:methods; D016166:Free Radical Scavengers / Q000032:analysis; D006358:Hot Temperature; D008892:Milk / Q000737:chemistry; D010084:Oxidation-Reduction; D010636:Phenols / Q000032:analysis; D059808:Polyphenols; D013451:Sulfonic Acids; D015032:Zinc / Q000737:chemistry*
D000596:Amino Acids; D000975:Antioxidants; D052160:Benzothiazoles; D002614:Chelating Agents; D003069:Coffee; D005419:Flavonoids; D016166:Free Radical Scavengers; D010636:Phenols; D059808:Polyphenols; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D015032:Zinc