Methods to improve and measure texture of sorghum cookies

Abstract

The effect of wheat flour substitution with sorghum flour (SF) on the quality of cookies was evaluated. The three point bending test and sensory panels were used to evaluate changes in cookie texture and acceptability. The formulations used were a Mexican style, standard AACC recipe, and a chocolate chip type. The Mexican style cookie was optimum to evaluate changes in SF on cookie quality. Mexican style cookies made with 100% SF were very gritty, dry and fragile. The chocolate chip cookies had improved palatability, although they remained fragile. Intensive milling methods increased the amount of damaged starch, reduced particle size and moisture in the flour in hopes of improving cookie quality. Milling detoxicated sorghum with a Udy cyclone mill was the best alternative. Flours with higher damaged starch (1x and 2x Udy milled, 11 and 16% DS) produced better cookies than flour with low damaged starch (Sr. milled, 7% DS). Substitution with native corn or sorghum starch did not improve cookie texture. Substituting 5% of SF with pregelatinized waxy corn starch (PCS) or with 10% vital wheat gluten improved the Mexican style cookie quality, making them less gritty and more resistant to breakage during handling, having bending force values close to wheat flour control. Enzymes (α-amylase, xylanase, pentosanase, and protease) and two reducing agents (L-cysteine and sodium metabisulfite) at different concentrations did not have detectable effects on Mexican style cookies made with 100% SF. Environmental SEM analysis was helpful in detecting the continuous starch/lipid phase in the chocolate chip formulation that coated the sharp edges of SF particles in the cookie. The Mexican style cookie crumb improved when 5% PCS was added; more air tunnels developed within the crumb with thicker walls and a starchy continuous matrix that functioned like gluten did in the wheat flour cookie. Sensory evaluation confirmed the improvement in cookie texture for sorghum flours with higher damaged starch levels and when 5% PCS-95% SF ratios were used. Sorghum flour can be used in various cookie formulations to levels as high as 95% in combination with 5% PCS and up to 50% in combination with 50% wheat flour.