Bacterial amylase lessens effects of damaged starch on tortilla quality.

Tortillas continue to gain in popularity. Since the dry milling of wheat damages starch, and wheat flour is the predominant ingredient in tortillas, we need to know what effects damaged starch can have on tortilla processing and product quality.

Amylases are often added to wheat flour to moderate the effect of damaged starch and to optimize flour quality. The objective of Texas A&M scientists was to study the effects of starch damage on dough and tortilla properties. They wanted to see if amylase could moderate the effects of damaged starch. It turns out that a bacterial amylase can overcome some of the negative effects of higher levels of damaged starch. Still, additional research is needed to understand precisely how starch damage influences the quality of tortillas.

In experiments, commercial wheat flour was mechanically damaged using a conical- shaped stone rotating grinder to generate different levels of damaged starch. Tortillas were prepared using pilot-scale, commercial processing equipment. The researchers added a bacterial amylase at 0, 0.05, 0.1 and 1 activity unit per kg of flour in order to hydrolyze the damaged starch. Subjective and objective properties of dough and tortillas were evaluated.

The scientists generated flours with increased starch damage, from 5.4% to 12.6%. The flour containing 9.7% or 12.6% damaged starch had significantly higher dough water absorption, toughness and press ratings. Objective dough compression values supported subjective ratings. Tortillas prepared from these flours had smaller diameters and lower opacities, but better shelf stabilities.

All levels of bacterial amylase had improved ratings for dough smoothness and dough toughness of flours that contained 9.7% or 12.6% damaged starch. Tortillas prepared using damaged starch and bacterial amylase had properties similar to those of the control. Wheat flour used in tortillas should have low levels of starch damage, since moderate to high levels of starch damage lowers all other tortilla qualities, despite improving tortilla shelf life. The research is continuing.

Further information. Ralph Waniska, Department of Soil and Crop Sciences, Texas A&M University, 370 Olsen Blvd., Heep Center, 2474 TAMUS, College Station, TX 77843; phone: [phone]; fax: [phone]; email: [e-mail].