No abstract

An objective extensibility test was evaluated to measure texture of corn tortillas. A tortilla strip is pulled apart by a tensile force during the test. Force at 1 mm deformation, force required to rupture the tortilla strip, modulus of deformation, and extensibility distance were correlated to subjective rollability and flexibility scores. Hard, firm tortillas required more force to deform and to rupture and had greater moduli of deformation than soft, flexible tortillas. Tortilla texture was affected by manufacturer of commercial tortillas and by aging. The coefficient of variation ranged from 6.0 to 16.7% for force at 1 mm deformation and work required to rupture, respectively. The extensibility technique is sensitive, fast, simple, and repeatable.

A simple and effective method to evaluate the ease of pericarp removal on lime (CaO)‐cooked corn (Zea mays L.) has been developed. Corn kernels placed in perforated nylon bags are lime‐cooked for 20 min at 98 to 100 °C and then stained in a solution containing methylene blue and eosine Y. We evaluated 11 corn hybrids grown at seven locations in 1989. The relative ease of pericarp removal was affected by hybrid and by growth environment, with hybrid differences being most important. The method requires a small sample, is rapid, and is ideally suited for ease of pericarp removal in screening large numbers of samples in breeding programs.

Cereal Chem. 75(3):320-324An objective rollability method that imitates subjective rollability scores of corn tortilla texture was developed. Force and work required to pull an axle that caused a tortilla to roll around a dowel were measured. The sensitivity of the technique to detect changes in corn tortilla texture during storage was evaluated, and other factors affecting objective rollability and tortilla texture were studied. The objective rollability technique was fast, simple, and sensitive to changes in the tortillas, and worked effectively on commercial samples. Data was significantly correlated to subjective rollability and flexibility scores. Textural differences among fresh tortillas during the first 24 hr of storage, and among tortillas with different thicknesses and additives, were detected by the objective rollability method. Thicker tortillas required more force and work to roll than thin tortillas. The objective technique is more sensitive to changes in texture than subjective evaluations, which do not detect differences in tortilla variability during the first 24 hr after baking, and it can be used to evaluate the effect of formulation and processing changes on fresh and stored tortillas.

A factorial experiment (4 × 2 × 2) was carried out to study the effect of a fiber degrading enzyme complex on starch yield, SO2 steeping time and starch properties of normal red sorghum (RS), heterowaxy (WHWx) and waxy (WWx) white sorghums compared to regular yellow maize (YM). Starch yields and total starch recovery for the sorghums ranged from 53–64% and 70–85%, respectively. Sorghum starch recovery values were significantly lower (p < 0.05) than maize (66% starch yield and 88% recovery). However, the WWx yielded more starch with lower protein and ash contents (P < 0.05) than the RS and WHWx sorghums. In the RS, the fiber degrading enzymes reduced steep time while owing the same starch recovery. The WWx starch required lower temperature to initiate gelatinization and had higher peak viscosities and lower retrogradation than the other starches. The WHWx starch had intermediate viscoamylograph properties between the regular and waxy starches.