Factors affecting the color of corn tortillas and tortilla chips

Abstract

The effects of phenols, amino acids, reducing sugars, pH and bleaching agents on color of tortillas and tortilla chips were investigated. Baked tortillas were equilibrated for 0, 5, 15, 30, 60 min and 24 hr prior to frying to examine the effect of equilibration on chip color. White dry masa flour (1.2% sucrose, 2.3% free amino groups and 1.2% phenols) for tortilla chips was blended with different concentrations and combinations of glucose, lysine and ferulic acid. Calcium oxide and citric acid were used to increase or decrease pH. Hydrogen, benzoyl and calcium peroxide were added as bleaching agents to improve tortilla chip color. Masa was sheeted, baked, cut, equilibrated and fried to produce tortillas and chips using pilot plant equipment. The color (L, a, b), pH, and moisture content of tortillas and chips were determined. Fat content of chips was determined with NIR. Tortillas and chips became darker above pH 7.5 and 6.4, respectively. A decrease in lightness was accompanied by an increase in a dull, yellow color. No darkening was observed in tortillas and chips at pH < 6.4. The minimum level of glucose, lysine and ferulic acid required to participate in the Maillard reaction was much higher in tortillas than chips with significant darkening occurring during frying. The combination of 50 ppm each of glucose, lysine and ferulic acid (GLF) caused darker chips. The combination of glucose and lysine produced darker chips at lower concentrations compared to all paired combinations of glucose, lysine and ferulic acid. Tortillas and chips prepared with hydrogen peroxide were lighter than untreated tortillas and chips. No lightening was observed by the addition of < 2500 ppm of calcium or benzoyl peroxide. Tortillas and chips prepared with GLF, citric acid and hydrogen peroxide had increased lightness when compared to tortillas and chips prepared with GLF alone. Tortillas fried immediately after baking produced oily chips which had excessive pillowing and poor texture. Chips appeared slightly darker when fried immediately compared to chips equilibrated for longer periods. Thus, equilibration time affects the oil absorption, texture and color of the finished chip. Variations in minor components of corn significantly affect color of white tortillas and tortilla chips.