Develop functional beverages based on white tea, soy or dairy milk.

The market for ready-to-drink tea, spurred on by products like green tea, has grown nearly 10-fold during the last decade. In 2004, sales for this market segment reached more than $2 billion. Consumers have taken a liking to these types of products, especially those that deliver a cooling and refreshing sensation. The development of a soy- or dairy milk-based white tea, for instance, offers a healthy alternative to consumers.

Tea that incorporates soy or dairy milk is becoming nutritionally popular. Unfortunately, the interaction of proteins and polyphenols produces astringency and bitter taste. Scientists at the University of Illinois attempted to develop a white tea beverage with soy or dairy milk and minimize the interaction between polyphenols and proteins.

The scientists examined the chemical stability of the beverage during its storage period and the effect of protein-polyphenol interactions on its antioxidant capacity. Total polyphenol content, antioxidant and antiradical activities were determined as well.

The binding affinity constants between polyphenols in white tea (epigallo catechin gallate, catechin and gallic acid) and the proteins in soy and milk (glycinin and beta-casein) were established spectrofluorometrically. The researchers stored instant powder tea-milk under accelerated conditions at 55 C. They evaluated the stability of liquid and powder versions of this product every 15 days for 60 days based on pH, color, soluble and insoluble solids, polyphenol content and antioxidant activity.

Using a 3-to-1 milk-to-tea ratio produced the desired color and sensory characteristics in both teas. The total polyphenol content of soymilk tea (1.6 [+ or -] 0.2 mg eq. gallic acid per ml) and of dairy milk-tea (1.8 [+ or -] 0.1 mg per ml) was stable during storage. The antioxidant capacity of these beverages was only slightly lower than that of tea: 70 [+ or -] 5 compared with 80 [+ or -] 5 mM Trolox per g.

The soy protein had fewer interactions with catechin and gallic acid than did milk protein. Overall, product quality did not change when both soy- or dairy milk-based teas in liquid and powder forms were under storage conditions.

Further information. Elvira Gonzalez de Mejia, Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, 228 ERML, 1201 W. Gregory Dr., Urbana, IL 61801; phone: [phone]; fax: [phone]; email: [e-mail].