EVALUATION of DIE SWELL and VOLUMETRIC EXPANSION IN CORN MEAL EXTRUDATES1

A method to determine die swell in the presence of volumetric expansion due to moisture vaporization in extruded food products is proposed. the method is applied to twin screw extrusion of corn meal in a study to investigate the effects of extruder die parameter (exit capillary length and entrance cone angle), screw speed, and specific feeding load on die swell and volumetric expansion. the die swell results are compared with known effects for nonexpanded polymers. Die swell tended to decrease with increasing exit length, but had only a weak response to entrance angle. Increasing specific feeding load (SFL) increased die swell, where as increasing screw speed produced increases or decreases in die swell, depending on the SFL. Die swells ranged from approximately 1.2 to 1.7, accounted for approximately 10 to 22% of the total radial expansion, and for approximately 18 to 38% of the extrudate cross sectional area. Volumetric expansion increased with increasing die exit length, but was insensitive to entrance angle with a slight concave upward response. Increasing screw speed produced large increases in volumetric expansion, while increasing SFL produced only slight increases. Observations about die swell compare favorably with previous studies of nonexpanded polymers, suggesting that the proposed analysis method may be useful for food viscoelasticity evaluation studies.     

PALATABILITY OF PANCAKES AND COOKED CORN MEAL FORTIFIED WITH LEGUME FLOURS

Various types of laboratory preparations of navy and pinto beans and commercial soy flours were used as fortifying agents to improve the nutritional quality of some relatively low protein foods-corn meal products and pancake mixes. The detectable level of legume products in these foods by a trained laboratory panel varied from about 10–25%. Sensory evaluation of the fortified and unfortified foods by paired comparison and hedonic scale methods indicated that up to 50% of some legume products could be added without significant loss in palatability.     

THE EFFECTS OF FLAXSEED, SOY AND CORN FLOURS ON THE TEXTURAL AND SENSORY PROPERTIES OF A BAKERY PRODUCT

The objective of this study was to assess the effects of some healthy ingredients on the properties of a ring‐shaped bagel/pretzel‐type bakery product to offer an alternative product satisfying consumer demand. For this purpose, ground flaxseed, defatted soy flour and corn flour were blended at a weight basis with wheat flour at 5, 10 and 15%. The taste score decreased upon increasing the level of substitution of flaxseed, soy and corn flours. Samples containing 15% of flaxseed were rated poorest in taste. No significant difference was observed in crust color except 15% level of flaxseed. The control sample had highest crust color value. The crispness scores of control and other samples containing 5% corn flour were higher than that of other samples. The samples with 5% flaxseed flour had lower crust L values. Flaxseed, soy and corn flour showed significant effects on the hardness, cohesiveness, springiness, gumminess, fracture force and stiffness values (P < 0.05). Samples with 15% corn flour had the highest hardness value. The results of the present study suggest that flaxseed, soy and corn flours could be added to a typical snack formulation up to levels of 10% with a reasonable acceptance offering promising nutritious and healthy alternative to consumers.     

GAS AND HIGH-PERFORMANCE LIQUID CHROMATOGRAPHIC ANALYSES OF AMINO ACIDS IN SOYBEAN MEAL, CORN AND TRITICALE

Analyses of amino acids in six samples each of soybean meal, corn and triticale by high-performance liquid chromatography (HPLC) and gas chromatography (GC) were compared. Samples were hydrolyzed in 6N HC1, then phenylthiocarbamyl (for HPLC) and N-heptafluorobutyryl (for GC) derivatives of free amino acids were prepared and analyzed by the appropriate system. Coefficient of variation within each feedstuff for amino acids analyzed by HPLC ranged from 1.8 (leucine) to 23.5% (methionine) in soybean meal, 2.7 (leucine) to 14.7% (methionine) in corn and 1.7 (leucine) to 14.3% (cystine) in triticale. Corresponding figures from GC analysis were 0.7 to 22.4%, 1.4 to 14.3% and 1.6 to 12.1%, respectively. Linear regression of HPLC on GC values gave good fits with R² ranging from 0.86 for cystine and 0.99 for isoleucine, leucine, lysine, methionine, phenylalanine, threonine, alanine, aspartic acid and glycine. Although some differences between the two systems were evident, feedstuff amino acid values obtained by HPLC and GC analyses compare very well. Results of this study and consideration of such factors as ease of derivatization and length of time for analysis, in our opinion, make HPLC the system of choice.     

EXTRUDED CORN MEAL AND WHEY PROTEIN CONCENTRATE: EFFECT OF PARTICLE SIZE

Blends of whey protein concentrate (WPC) and corn meal, which were separated into four particle fractions (residual on a #30 screen, #40 screen, #60 screen and through a #60 screen), were extruded at two moisture conditions (23 and 28%) to determine the effects of particle size on the extrudate properties. Smaller particle size fractions exhibited increased solubility and significantly higher viscosity both with and without added protein. When WPC was added to the corn meal, a large reduction in paste viscosity was observed regardless of the particle size. The blend with similar particle size distributions of corn meal and WPC had a significantly higher viscosity than the other blends. The expansion ratio, porosity and breaking strength of this blend, when extruded at the lower moisture content, were improved to the extent that they behaved similarly to extrudate made from corn meal alone.     

SOME TEXTURAL, SENSORY AND NUTRITIONAL PROPERTIES OF EXPANDED SNACK FOOD WAFERS MADE FROM CORN, LENTIL AND OTHER INGREDIENTS

Crisp expanded wafers were produced from extruded pellets containing specialty starches and flours derived from peas, lentils, corn and blends of lentils and corn. The density, hardness and consumer acceptability of the wafers varied with the different ingredients. The most acceptable products were produced from corn, lentils and blends of these two ingredients. The weight, density, stiffness and hardness of the wafers increased with the proportion of lentil flour used to make them. Sensory analysis suggested that consumer acceptability was optimal for blends containing between 40 and 80% of lentil flour. Stiffness and fracture force measured by texture profile analysis were correlated with the sensory attributes of hardness and toughness. The glycemic potential measured by in vitro digestion of the wafers was lower for the 100% lentil wafers compared with the 100% corn wafers because of the amount of starch in the grain. For combinations of corn and lentils, the carbohydrate digestion rate, and hence the glycemic potential, was lower than for either 100% corn or 100% lentil wafers. Blending of selected cereal flour ingredients should be a useful method for reducing the glycemic impact of cooked starchy snacks.     

ADDITION OF CORN GLUTEN MEAL AND ZEIN TO GROUND PORK OF VARIOUS FAT PERCENTAGES1

Corn gluten meal and zein at levels of 0, 2.5 and 5% were added to ground pork of three fat percentages. Raw patties were analyzed for fat, moisture, protein contents and color. Selected patties, broiled to 77°C, were evaluated for proximate composition, total cooking loss, color and Instron compression. Five percent zein added to ground pork reduced cooking loss 4.2% when compared with ground pork without zein. Addition of corn gluten meal to pork did not influence yield. Instron compression values increased with the addition of zein and corn gluten meal. Increased fat altered the hue (increased hue angle due to increased b) of the interior of the cooked pork patties. Zein addition also increased the lightness of cooked pork patties. The addition of zein to ground pork patties decreased sensory tenderness and pork flavor intensity and increased off-flavor intensity.     

UPTAKE OF SUCROSE SOLUTION BY EXTRUDED CORN BALLS AND EFFECT ON THE TEXTURAL CHARACTERISTICS

Extruded corn balls were subjected to dip coating with sucrose solutions (0–70%) at different temperatures (20–50C) to determine several coating characteristics such as total uptake, uptake of solid and dimensionless uptake (sucrose solution uptake/water uptake). Textures of the wet sample, as well as the dried sample, were determined under compressive loading, to obtain the maximum force offered and the deformability modulus. A progressive increase in solid uptake occurs with an increase in concentration and/or temperature while the effect of the latter is low. The deformability modulus of the samples drastically increases because of the absorption of sucrose and because of drying. The desirable high dimensionless uptake can be obtained with a high concentration of sucrose at a low temperature. The uptake of solid generally shows a significant relationship (P ≤ 0.05) with other coating and textural parameters for the wet sample, but not with the dry product.     

EFFECT OF ENZYMATIC TREATMENT OF CORN GLUTEN MEAL ON LUTEIN, ZEAXANTHIN AND β-CRYTOXANTHIN EXTRACTION

Response surface methodology was used to optimize some operating parameters on the effects of alcalase treatment extraction of lutein, zeaxanthin and β -cryptoxanthin from corn gluten meal (CGM) on the yield of total xanthophylls. Three independent variables tested were enzyme concentration, substrate concentration and hydrolyzing time. The t -test and P value indicated that the quadratic of the three variables, enzyme concentration and hydrolyzing time were important linear variables affecting the total xanthophyll yield ( P <  0.005), followed by substrate concentration ( P <  0.01). The interaction effect between enzyme concentration and hydrolyzing time was also significant ( P <  0.005). Considering the efficiency, the economy of materials and the feasibility of experiment, the technique parameters were optimized by constrained complex method. The optimum conditions were obtained as follows: the enzyme concentration, the substrate concentration and the hydrolyzing time were 4,367 U/g, 11.3% and 2.4 h, respectively. The highest total xanthophyll yield was predicted of 65.69  µ g/g when CGM was hydrolyzed under the optimum condition. The suitability of the model equation for predicting the optimal response values was tested using the selected optimum conditions; the experimental yield was 65.06  ±  0.78  µ g/g, which was found to be in agreement with the predicted yield.

PRACTICAL APPLICATIONS

Corn gluten meal (CGM), a major by-product of corn wet milling, contains (on a dry basis) 200–400  µ g/g carotenoids. There are ∼840,000 tons of CGM produced in China every year. If a part of CGM produced was manufactured further to produce carotenoids as foods, materials of foods and additives of pharmaceutical products, its value and presence in the marketplace would be increased.     

SWEETNESS PERCEPTION IN RELATION TO SOME TEXTURAL CHARACTERISTICS OF HYDROCOLLOID GELS

The apparent sweetness of five different hydrocolloid gels prepared with equal amounts of sodium Sucaryl varied significantly (P < 0.01) when tested in a multiple paired arrangement by seven trained judges. Results from four replications consistently showed sweetness to be the greatest in carrageenan gels and the least in cornstarch gels. It was intermediate in low methoxyl pectin, agar and gelatin gels. Concentrations of gelling agents were selected to produce gels comparable in hardness. Characterization of mechanical textural properties with the GF-Zenken Texturometer showed that gels of cornstarch and gelatin were more cohesive, springy, chewy and gummy than those of agar, low methoxyl pectin and carrageenan (P < 0.01). These findings suggested that gels which take more effort to disintegrate limit taste perception. Multiple regression analyses showed that the measured mechanical textural parameters accounted for 52.3% of the variability in sweetness scores suggesting that other characteristics may also play a role. Inspection of correlation coefficients of sweetness with single textural parameters showed no one characteristic as a dominating influence over sweetness.     

CORN GERM PROTEIN IN FRANKFURTERS: TEXTURAL,COLOR, AND SENSORY CHARACTERISTICS AND STORAGE STABILITY1

Textural properties, water holding capacity, color, sensory characteristics, and storage stability of frankfurters containing hexane-defatted corn germ protein (CGP) as a meat extender were studied. CGP was incorporated at 2 and 3% levels as a powder or a preswelled slurry. Batter viscosity and shear force values of frankfurters were increased by the preswelled CGP. The redness values of the experimental samples with 2 and 3% CGP added as a powder were less than those of controls. There were no significant effects of CGP incorporation or its preswelling on the initial sensory properties of frankfurters. Meaty flavor and aroma and off-flavor acceptability decreased during 45 days of storage. Off-flavor and off-aroma of frankfurters showed a slight increase with time in storage. Total volatile nitrogen and nonammonia amino nitrogen of experimental and control frankfurters were not significantly different.     

ANTIMICROBIAL AND ANTIOXIDANT ACTIVITIES OF CORN GLUTEN MEAL SUBSTANCES IN AN EMULSIFIED MEAT MODEL SYSTEM

Corn gluten meal (CGM) and pH adjusted (6.6)/particle size-reduced (∼7μm-MC7; ∼38μm-MC38) CGM increased oxidative and microbiological shelf-life of a model emulsified meat system. After 14 days, TBARS were significantly lower for samples containing MC7 and MC38 when compared to controls, and samples containing soy protein isolate (SPI) or native CGM. Based on aerobic plate counts, MC38 and CGM increased product shelf-life by ∼7days compared to SPI- and MC7-containing products and controls. These results suggest that the use of corn gluten meal substances in an emulsified meat product could create a more shelf stable product. These functional characteristics may make the incorporation of corn gluten meal into foods more feasible.     

EFFECTS OF CORN MEAL, VITAL WHEAT GLUTEN, HIGH AMYLOSE STARCH AND EXTRUSION PARAMETERS ON TECHNOLOGICAL PROPERTIES OF WHEAT-BASED EXTRUDED BREADING

A wheat‐based extruded breading was produced using a Brabender single‐screw laboratory scale extruder (model GNF 1014/2) and applied to chicken nuggets. Response surface methodology was applied to study and optimize the effects of formulation and extrusion parameters on pick up, texture, solid loss, oil absorption and adhesiveness of fried coated nuggets. An optimized extruded breading was produced at 160C, 27% moisture content, 15% vital wheat gluten, 8% high amylose starch and 30% corn meal. The product showed pick up of 29.87%, adhesiveness of 100%, texture of 166.1 g, oil absorption of 2.97% and solid losses of 0.0885 absolute. The product presented similar values of pick up and adhesiveness, better texture, lower oil absorption and higher solid loss during deep‐frying, compared with commercial breadings. Acceptance test showed that the product had better overall appearance and fairly similar texture, compared with the commercial ones.