Characterization of tortillas and tortilla chips from sorghum varieties high in phenolic compounds

Abstract

The effects of varying pH and sorghum type on tortilla and tortilla chip properties were evaluated. Masas from white, brown and black sorghums were adjusted to pH levels of 7 (neutral), 9 (control) and 11 (alkaline) and processed into tortillas and tortilla chips. Citric acid and lime solutions were used to adjust the pH. Textural changes of tortillas stored for 2 and 24 hr were evaluated objectively using the extensibility test and subjectively using bending, pliability and rollability tests. Texture of chips was also evaluated using the rupture test. Pasting properties, color, and level of phenolic compounds of tortillas and tortilla chips were determined. Sensory evaluation was conducted with selected tortilla chips. White tortillas required more force to extend and were more extensible than brown and black tortillas at every pH. Alkaline pH tortillas for each sorghum type retained fresh characteristics longer during storage compared to tortillas at neutral and control pH. Methanol extracted flours prepared from black tortillas and tortilla chips developed lower pasting viscosities than brown and white tortilla residues. The shorter peak time of alkaline pH tortilla and chip residues might be related to repulsion between negatively charged starch molecules. A darker pericarp color and higher pH produced darker tortillas and tortilla chips. The colors of tortillas and chips at pH 7, 9 and 11 were reddish brown, brown and dark brown for brown sorghum; dark brown, reddish black and black for black sorghum; pinkish tan, yellowish tan and dark yellow for white sorghum. Phenols were mostly retained during tortilla and tortilla chip processing. Brown and black sorghums have a potential use in the production of dark color tortillas and chips since consumers are relating dark color to healthy food.