Extend storage stability of tortillas with alpha amylase and soy proteins.

Commercially produced wheat flour tortillas are made with anti-molding additives. For this reason, they are generally shelf-stable in terms of their microbial quality. However, a loss in textural quality rapidly occurs during storage, which limits the storage stability of tortillas.

This loss in quality, often referred to as staling, is believed to be caused by starch retrogradation or a loss of the flexibility of the protein matrix. Texas scientists wanted to find ways of preserving the textural quality of wheat flour tortillas during storage. They found that using an amylase and soy proteins, it's possible to produce tortillas with extended storage stability.

How alpha amylase can reduce the extent of tortilla staling caused by starch retrogradation was studied. The researchers also worked to see if adding soy proteins would help improve the stability of the protein matrix in tortillas. Alpha amylase and soy proteins were added to a standard tortilla formulation. The tortillas were evaluated for their sensory properties, opacity, diameter and specific volume. Texture measurements were performed using the two-dimensional extensibility test with a commercial texture analyzer and the subjective rollability test.

Tortillas with alpha amylase had a larger diameter than the control tortilla. Most of the soy proteins created softer tortillas, although some protein isolates reduced the tortilla diameter. The investigators noted a marked improvement in the retention of textural quality during storage in those tortillas with alpha amylase alone, and in combination with soy proteins.

The control tortillas lost flexibility after 14 days of storage, while those with alpha amylase--with or without soy proteins--remained flexible through 28 days.

Further information. Ralph Waniska, Department of Soil and Crop Sciences, Texas A&M University, 370 Olsen Blvd., 429C Heep Center, 2474 TAMU, College Station, TX 77843; phone: [phone]; email: [e-mail].