Evaluation of corn tortillas fortified with whole and partially defatted flax meal
Santiago San Martin, Diana Iris
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Corn tortilla is a staple food consumed regularly by Mexicans. This staple food is deficient in nutrient content, specially in protein. Flax is a seed rich in protein and has a good amino acid profile which mixed with corn flour may increase the protein and amino acid content in tortillas. Although the use of the oilseed can be expensive, there is potential for the flax meal (by-product) obtained after oil extraction from the seeds, this meal will be less costly than the flax seed. The overall objectives were to develop tortillas higher in protein content and to evaluate the possible changes that the addition of flax meal could produce on the physical, chemical and sensorial properties of corn tortillas. Partially defatted and whole flax meal were added at levels of 10, 15 and 20% to a nixtamalized corn flour. Textural properties and moisture content of tortillas were measured at 30 minutes, 24 hours and 48 hours after preparation. Water absorption capacity and water activity were determined for each treatment dough and tortillas respectively. Textural properties (strength, extensibility and toughness) and moisture content showed a significant difference (p<0.05) for tortillas fortified and unfortified; the level of flax addition in the nixtamalized corn flour changed the weight loss as compared to those prepared using only nixtamalized corn flour. Chemical analysis (protein and fat content) of corn tortillas was determined for each tortilla treatment. Addition of partially defatted and whole flax meal increased protein content in tortillas, as well as possibly improved the amino acid profile specially for lysine and tryptophan. The physical and chemical evaluation of fortified tortillas at levels of 10 and 20% showed acceptable textural and nutritional properties to be tested for sensory evaluation. The variables age and frequency of consumption showed to have a significant effect on acceptability of the samples (p<0.05). Color measurements were obtained for tortillas freshly prepared from golden and brown flax meal for each treatment. Brown flax meal gave a negative effect on tortillas color when added to tortilla formulation (p<0.05), reducing the acceptability of the product. Golden flax meal decreased this effect.