Sergio Soto-Simental

Physicochemical Characterization of Regional Breads Produced in the Northern Mountains of Puebla State, Mexico

Water exists in foods in free and bound forms; only unbound water is available for microbial growth and biochemical reactions (Prior 1979; Troller 1980). Measurement of unbound water is termed water activity (A w ) and is defined as the ratio of partial vapor pressure of water in the air to the vapor pressure of water vapor in saturated air at the same temperature (Scott 1957). This measurement is numerically equal to the relative humidity at equilibrium expressed as a fraction. Techniques for measurement of A w have been reviewed by Prior (1979) and Troller and Christian (1978). In addition, two collaborative studies have compared the various methods (Labuza et al. 1976; Stoloff 1978). Bread is one of the oldest food products consumed by humans. There is clear evidence of its use by different civilizations since prehistoric times. Bread has been a popular product because of its nutritious properties, and this product uses common ingredients as salt, sugar, and yeast (Serna 1996). Bread is a basic food made with cereals, usually in the form of flour, and liquid means, usually water. One of the greatest differences in bread production is the addition of leavening. Bread can be identified by very different names according to its form, weight, color, texture, etc., and the way in which it is presented in different countries as well as in different localities. In Mexico, baking product consumption is high, where approximately 750 varieties of sweet bread exist (CANAIMPA 2007).