Temperature, Humidity Degrade Green Tea Benefits

WEST LAFAYETTE, Ind.Increased temperature and humidity, to a smaller degree, speed catechin degradation in green tea powder, according to a new study published in the Journal of Agricultural and Food Chemistry.

"People drink green tea for health benefits, so they want the catechins to be present," said lead author Lisa Mauer, a Purdue University professor of food science. "The instant powder beverages are becoming more popular for consumers, and it's important to know how storage can influence nutrition of your products."

Previous research showed the powders were stable below the glass transition temperature, the temperature at which an amorphous solid changes from a rigid, glassy state to a rubbery, viscous state. In that rubbery state, compounds may start reacting with each other faster due to increased molecular mobility, leading to significant chemical degradation.

For the study, catechin concentrations were tracked using high-performance liquid chromatography. The method involved dissolving the green tea powder into a solution, which then passed through a column. Compounds moved at different rates and could be measured. More than 1,800 powder samples were stored at varying temperature and humidity combinations for up to 16 weeks and then measured for catechin loss. Those at the highest temperatures and humidities lost the most catechins.

Models then were built to predict the rates at which catechins would be lost at different storage conditions. Mauer said the food industry could use the models to predict the amount of catechins and the likely health benefits in green tea powder at the time it is used.

"Knowing what's happening to the ingredients is extremely important for understanding the quality of a food or beverage product," she said.