The health-giving compounds in green tea powders aren't as stable as once thought and how you store them can determine whether they are beneficial or not, say Purdue University researchers.
U.S. imports of green tea have increased more than 600 percent over the last decade, largely due to the perceived health benefits of the catechins it contains. Catechins are antioxidants thought to fight heart disease, cancer, diabetes and other health problems.
"People drink green tea for health benefits, so they want the catechins to be present," said Purdue's Lisa Mauer. "The instant powder beverages are becoming more popular for consumers, and it's important to know how storage can influence nutrition of your products."
Mauer's research revealed that increased temperature - and humidity, to a smaller degree - speed catechin degradation. "Tea powders are not infinitely stable below their glass transition temperature [the temperature at which an amorphous solid changes from a rigid, glassy state to a rubbery, viscous state]. They degrade more slowly below that temperature, but they can still degrade," Mauer said.
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.
"Knowing what's happening to the ingredients is extremely important for understanding the quality of a food or beverage product," Mauer said. She now intends to look at what the catechins become once they degrade and how those new compounds affect nutritional qualities.
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Source: Purdue University