Yuzo Mizukami

Changes in the Concentrations of Acrylamide, Selected Odorants, and Catechins Caused by Roasting of Green Tea

This research aims to optimize roasted green tea (Houjicha) processing by using roasting treatments to achieve acrylamide mitigation without compromising the quality. 2-Ethyl-3,5-dimethylpyrazine and 2-ethyl-3,6-dimethylpyrazine were identified as potent odorants by aroma extract dilution analysis. In preliminary sensory experiments, the desirable Houjicha flavor was produced in products roasted at 160 degrees C for 30 min and at 180 degrees C for 15 min. Under these conditions, potent odorants were formed at levels adequate for contributing to the Houjicha flavor. Acrylamide amounts in tea infusions were 2.0 and 4.0 microg/L by roasting at 160 degrees C for 30 min and at 180 degrees C for 15 min, respectively. Compared to roasting at 180 degrees C, the degradation of tea catechins was suppressed by roasting at 160 degrees C. Hence, roasting at 160 degrees C for is recommended for Houjicha processing for acrylamide mitigation, formation of potent odorants, and suppression of degradation of tea catechins.

Evaluation of the Astringency of Black Tea by a Taste Sensor System: Scope and Limitation

Grading the astringency of black tea by a taste sensor system was studied. The black tea samples manufactured in India and Sri Lanka were classified into ten steps on the basis of two standard solutions (0.65 mM and 0.26 mM EGCg aqueous solutions). An organoleptic test demonstrated that the sensor output was correlative to the human gustatory sense.

Acrylamide in roasted barley grains: presence, correlation with colour and decrease during storage

We investigated the presence of acrylamide in roasted barley grains, and assessed the correlation between acrylamide concentration and colour, and also examined acrylamide decrease during storage. Acrylamide concentrations in 45 commercially available roasted barley grains were analysed. The mean and standard deviation were 0.24 and 0.08 mg kg−1, respectively. The CIE colour parameter a* value had little correlation with acrylamide concentration in roasted barley grains; however, the L* and b* values showed correlations with acrylamide concentration in the grains, yielding a correlation coefficient of 0.42 and 0.40, respectively. Darker-coloured roasted barley grains with lower L* values may contain lower amounts of acrylamide. Although acrylamide concentration decreased by 40% in the grains, and decreased by 36% in the milled grains (teabag form) after 309 days of storage at room temperature a significant difference in the rate of acrylamide decrease was not observed between the grain and teabag forms. The data obtained in this study are of importance to the risk assessment and management of acrylamide exposure in Japan.

Acrylamide elution from roasted barley grains into mugicha and its formation during roasting

ABSTRACT This paper investigated acrylamide elution from roasted barley grain into mugicha and its formation during roasting of the grain. Mugicha is an infusion of roasted barley grains. Highly water-soluble acrylamide was easily extracted to mugicha from milled roasted barley grains in teabags. On the other hand, the acrylamide concentration in mugicha prepared from loose grain increased with longer simmering and steeping times. During roasting in a drum roaster, the acrylamide concentration of the grain increased as the surface temperature rose, reaching a maximum at 180–240°C. Above this temperature, the acrylamide concentration decreased with continued roasting, exhibiting an inverted ‘U’-shaped curve. For most of the samples, the acrylamide concentration showed good correlation with the value of the colour space parameter L*. The dark-coloured roasted barley grains with lower L* values contained lower amounts of acrylamide as a result of deep roasting. The level of asparagine in barley grains was found to be a significant factor related to acrylamide formation in roasted barley products. The data are an important contribution to the mitigation of acrylamide intake from mugicha.