Ralph D. Waniska

Cooking Characteristics and Quality of Noodles from Food Sorghum

ABSTRACT Three white food sorghums, ATx631*RTx436, ATxARG*RTx436, and SC283-14, were decorticated, milled into flour and processed into 100% sorghum noodles. Flour, water, and salt (1%) were preheated using a hotplate or a microwave oven. The mixtures were put through a forming extruder to produce noodles. Extruded noodles were dried by three methods: air-dry method (23°C, 48 hr); one-stage (60°C, 30% rh, 3 hr), or two-stage (60°C, 100% rh for 2 hr followed by 60°C, 30% rh for 2 hr). Noodles were evaluated dry and after cooking. Sorghum flours with smaller particle sizes yielded better noodles. The microwave preheating method yielded better noodles than the hot-plate method. Stronger and firmer noodles, dry or cooked, were prepared using two-stage drying compared with the other drying methods. Fine flour that was preheated using a microwave oven and dried using the two-stage method gave the best noodles with moderate (10%) dry matter loss. Optimized processing conditions yielded sorghum noodles with good ...

Effects of Leavening Acids and Dough Temperature in Wheat Flour Tortillas

ABSTRACT Functionality of four leavening acids (sodium aluminum phosphate [SALP], sodium aluminum sulfate [SAS], monocalcium phosphate [MCP] and sodium acid pyrophosphate [SAPP-28]) was evaluated during processing of wheat flour tortillas. Formulas were optimized to yield opaque, large-diameter tortillas with pH 5.9–6.1. Each leavening acid and sodium bicarbonate was first evaluated at 38°C and then evaluated in combination with fumaric acid at 34 and 38°C. Ionic and pH interactions of leavening salts adversely affected dough properties and resting time. Opacity and pH of tortillas prepared with MCP was lower than for other treatments. Higher dough temperature required more leavening acid and base to compensate for some of the loss of CO2 incurred during dough mixing and resting at 38°C. The addition of fumaric acid decreased the amount of leavening acid, the dough-resting time and tortilla pH, and improved storage stability. Combinations of MCP, SALP (or SAS), and fumaric acid produced dough and tortilla...

Rheological and sensory evaluation of wheat flour tortillas during storage

ABSTRACT Texture of wheat flour tortillas over 15 days at room temperature was evaluated using an expert sensory panel, consumer panels, subjective rollability test, large deformation rheological methods (i.e., bending, extensibility [1-D and 2-D], and puncture tests), and stress relaxation method. Most of the changes in texture occurred during the initial 8 days of storage, while texture of tortillas changed slowly thereafter. Differences in texture between fresh and 1-day-old tortillas were detected by many objective rheological methods but not by either sensory panel. The expert sensory panel observed a rapid decrease in tortilla extensibility and an increase in staleness between 1 and 8 days of storage and smaller changes in sensory scores after 8 days of storage. Most objective rheological parameters changed rapidly between 0 and 5 days, and slowly after 5 days of storage. Significant correlations and factor analysis reveal that changes occurring in flour tortillas during staling are estimated better...

Response of eight sorghum cultivars inoculated with Fusarium thapsinum, Curvularia lunata, and a mixture of the two fungi

Abstract Field studies were conducted in 2000 and 2001 to investigate effects of two common grain mold fungi, Fusarium thapsinum, Curvularia lunata and a mixture of the two pathogens, on grain mold severity and seed germination in eight sorghum cultivars with different levels of vulnerability to grain mold. Significant effects due to cultivar, fungal treatment and their interaction were observed for grain mold severity (GMS) and for germination. Fungal treatments increased GMS and reduced seed germination in all cultivars. Sureno was the most resistant cultivar evaluated. All other cultivars exhibited susceptible reactions. The type of grain mold fungi present in the field influenced the level of GMS, since cultivars responded differently to inoculation with individual or multiple fungal species. Germination was significantly reduced by all fungal treatments. C. lunata had the most negative effect on germination in 2000 while F. thapsinum produced the most reduction in germination in 2001. These pathogens caused significant reductions in the germination rate, even though GMS ratings on inoculated panicles were low.

Use of Extensibility to Measure Corn Tortilla Texture

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.

Effects of Wheat Protein Fractions on Flour Tortilla Quality

ABSTRACT Commercial wheat protein fractions (10) were evaluated during processing for quality of tortillas prepared using pastry, tortilla, and bread flours. Protein fractions that separately modify dough resistance and extensibility were evaluated in tortillas to determine whether the proteins could increase diameter, opacity, and shelf stability. Tortillas were prepared using laboratory-scale, commercial equipment with fixed processing parameters. Dough and tortilla properties were evaluated using analytical methods, a texture analyzer, and subjective methods. Tortillas were stored in plastic bags at 22°C for up to 20 days. Adjustments in water absorption and level of reducing agent were made to normalize differences in functionality of 3% added proteins on dough properties. Tortilla weight, moisture, pH, opacity, and specific volume were not affected by added proteins, except for glutenin and vital wheat gluten treatments, which had decreased opacity in tortillas prepared from pastry flour. Increased i...

Objective Rollability Method for Corn Tortilla Texture Measurement

ABSTRACT An 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 det...

Maize endosperm proteins that contribute to endosperm lysine content

ABSTRACT Nonzein proteins were analyzed using SDS-PAGE to study their relationship to lysine level in mature endosperm of three isogenic lines and 29 inbred lines. The majority of nonzein proteins are glutelins that contain a relatively high lysine content. Trinitrobenzene-sulfonic acid was used to visualize high-lysine proteins on nitrocellulose membrane. Seven intense yellow bands (high-lysine proteins) were found in the glutelin fraction: 35, 43, 48, 52, 84, 92, and 100 kDa. These seven glutelin proteins were also significantly correlated to each other. Lysine content of the triads correlated with three glutelin proteins (35, 43, and 52 kDa), while lysine content of 29 inbred lines correlated with six glutelin proteins (all except 52-kDa protein). Immunoassays based on these higher lysine glutelin proteins provide an effective screening method in the presence of variable zein levels. Retention or improvement of lysine content is possible using this information in a maize improvement program.

Condensed Tannins in Traditional Wet-Cooked and Modern Extrusion-Cooked Sorghum Porridges

ABSTRACT The profile and quantities of condensed tannins (CT) in foods are affected by processing due to their highly reactive nature, which may affect their antioxidant activity and the nutritional value of the foods. The objective was to compare the quantity and profile of condensed tannins in traditional wet-cooked and modern ready-to-eat extrusion-cooked sorghum porridges. CT were analyzed using normal-phase HPLC with fluorescence detection and their content was compared to CT and total phenols determined with standard colorimetric assays. Both the traditionally prepared and instant porridges had significantly reduced CT polymers (DP > 8), with retentions of 38 and 9%, respectively, of the CT present in the whole grain. Oligomer (DP 2–8) and monomer (DP 1) contents in traditional porridges were not significantly different from those of grain. In extruded porridges, the oligomers were reduced and the monomer content was increased. The extractable CT oligomers and monomers in the extrusion-cooked sorghu...

Changes in Starch Properties of Corn Tortillas during Storage

Starch properties of corn tortillas were characterized during storage. Tortillas were chopped into pieces, macerated with ethanol, centrifuged, extracted again with ethanol, centrifuged, dried, and ground into flour to dehydrate and stabilize starch. Water absorption and water solubility at 25°C, starch pasting properties, and amount and molecular weight of starch extracted at 95°C in water were quantified. Increased levels of soluble amylopectin and increased cold paste viscosity distinguished fresh (0, 0.5, and 1 h) from aged (120 h) tortillas. Water solubility at 25°C decreased continuously during storage; whereas, water absorption increased 0.5 h after baking and then decreased during storage. Rapid changes in starch properties were stabilized using the dehydration procedure and clearly distinguished by pasting viscosities and other methods. Measured starch properties were consistent with very rapid associations (retrogradation) of amylose and rapid associations of amylose and amylopectin yielding insoluble structures in corn tortillas. Retention of some starch crystal nuclei after baking facilitated starch associations that yielded rapid structural changes in corn tortillas.