Rolando A. Flores

Physical properties of starch-based foams as affected by extrusion temperature and moisture content

Abstract Although considerable effort has been made to improve the physical and mechanical properties of starch-based foams, they still do not compare favorably with traditional plastic foams. The properties of the foams depend largely on the starch moisture content and extrusion conditions. The purpose of this study was to evaluate the effects of extrusion temperature and moisture content of starch-based foams on selected physical properties. Blends composed of 49% wheat and corn starch (dry solid basis), 33% synthetic polymers, 10.5% total water, 7% blowing agents, and 0.5% nucleating agent were extruded at 100–160°C extruder barrel temperatures and 100 rpm screw speed using a single-screw C. W. Brabender laboratory-scale extruder. Starch-based foams were equilibrated at different relative humidities (10–90%). Moisture adsorption isotherms, bulk densities, and expansion ratios of the starch-based foams were studied. The moisture adsorption isotherms of starch-based foams were rising sigmoidal curves similar to those of grains and grain products. The bulk density of the starch-based foams decreased as the extrusion temperature increased. The highest expansion occurred when the blends containing normal wheat starch were extruded at 140°C. The starch-based foams were four to eight times more dense than polystyrene foam.

Mechanisms of ice crystallization and recrystallization in ice cream: a review.

This review article focuses on the mechanisms of ice crystallization and recrystallization and factors that influence them in ice creams. Ice crystallization is an important factor that determines ice creams final quality. The smaller the ice crystal size is in the final product, the better the quality is. Large ice crystals cause a coarse, grainy, and icy texture in ice cream. The initial ice crystals are formed in the freezer barrel and then grow in size during hardening and storage. Recrystallization during storage is influenced by various factors, including total solids, initial freezing temperature, unfrozen water, stabilizer type, sweetener type, and storage temperature. The roles of these factors, especially stabilizers, are discussed.

Effect of Particle Size and Moisture Content on Viscosity of Fish Feed

ABSTRACT A model was developed for the influence of particle size on the extrusion of a fish feed and the physical characteristics of the extrudates evaluated. The study was conducted using factorial experiments in a fractional replication design for four variables with three levels, and one-third of the replicates (34 factorial in 27 units) were examined in a laboratory extruder. The torque-screw speed measurement was used to develop a viscosity model equation that considered different shear rates, product temperature, initial moisture content, and particle size. When particle size decreased, the apparent viscosity became smaller. The barrel pressure was important in producing extrudate with a uniform volume over the range of processing conditions tested because it had a strong correlation with the volumetric expansion. The material with lower moisture and larger particles caused the specific mechanical energy to increase. The viscosity model developed in this study can be applied to the development of l...

Effect of Different Wheat Classes and Their Flour Milling Streams on Textural Properties of Flour Tortillas

ABSTRACT Wheat flour tortillas were made from flour streams of three wheat cultivars: Jagger hard red winter wheat, 4AT-9900 hard white winter wheat, and Ernie soft red winter wheat. Wheat samples were milled on a Miag experimental mill. Twelve flour streams and one straight-grade flour were obtained. Tortillas were made from each flour stream and the straightgrade flour by the hot-press method. Tortilla stretchability and foldability were evaluated by a texture analyzer and six panelists, respectively. Flour protein and water absorption affected tortilla texture. The foldability evaluated by panelists was positively correlated with flour protein content, farinograph water absorption, and damaged starch (P < 0.05). The 2BK and 3BK streams of hard wheat produced tortillas with strong stretchability and good foldability. Middling streams of hard wheat yielded tortillas with lighter color and less stretchability. Under the conditions tested in this study, soft wheat flours were not good for producing flour t...

Effect of Additional Separation and Grinding on the Chemical and Physical Properties of Selected Corn Dry-Milled Streams

ABSTRACT Three streams of corn dry-milled products (corn grits, corn cones, and corn flour) from three different commercial corn dry-millers were further separated by particle size according to the major portion of each stream. They were separated into corn grits (1.190 and 0.841 mm), corn cones (0.595, 0.420, and 0.297 mm), and corn flour (0.297 and 0.210 mm). Besides separation, corn grits were also ground and then separated into ground corn grits (0.297 and 0.210 mm). The original streams, streams with additional separation, and streams with additional grinding were analyzed for protein content, ash content, crude fat content, and color properties. Duncans significant difference tests (P < 0.01) showed that additional separation and grinding of the commercial corn grits, corn cones, and corn flour affected protein, crude fat content, and color parameter (L, a, and b) distribution of the products. The tristimulus parameters (L, a, and b) were good indicators of the protein content of the corn dry-mille...

Proximate analysis of food service wastes

Association of Official Analytical Chemists (AOAC) methods of analysis were used to determine the protein, fat, ash, carbohydrate, moisture, and energy contents of food wastes from a large university dining center and two military facilities. Food waste from the service area of the university dining center contained (on a dry weight basis): 14.86% protein, 17.46% fat, 3.23% ash, and 64.50% carbohydrate, and 1.97 MJ/100 g of sample. The average nutrient content of food waste from the service area for the two military facilities was: 17.53% protein, 21.69% fat, 3.99% ash, and 56.79% carbohydrate and 2.06 MJ/100 g of sample. The moisture was 65.29% and 70.81% from the university and military facilities, respectively. Findings from this study can be used in evaluating usage of food waste, such as animal feeding, composting, and bioconversion.

Composition of Functional Lipids in Hulled and Hulless Barley in Fractions Obtained by Scarification and in Barley Oil

ABSTRACT Two cultivars of hulled barley (Thoroughbred and Nomini) and two cultivars of hulless barley (Doyce and Merlin) were scarified to abrade the outer layers of hull and pericarp. The resulting scarification fines fractions were evaluated as potential sources of functional lipids (phyto-sterols, tocopherols, and tocotrienols). The levels of total phytosterols and total tocotrienols in the barley scarification fine fractions were probably not high enough to justify their use as functional foods. However, the levels of total phytosterols and total tocotrienols in the oils extracted from both whole kernels and scarified fines were both sufficiently high to make it reasonable to consider their potential use as new functional oils. Indeed, the levels of total tocotrienols in barley oils (2,911–6,126 mg/kg of oil) are several-fold higher than those reported in two other oils that are being marketed as high in tocotrienols: palm oil (530 mg/kg) and rice bran oil (770 mg/kg). The levels of total phytosterols...

Small-Scale Extrusion of Corn Masa By-Products

ABSTRACT Corn masa by-product streams are high in fiber and are amenable for utilization in livestock feed rations. This approach is a potentially viable alternative to landfilling, the traditional disposal method for these processing residues. Suspended solids were separated from a masa processing waste stream, blended with soybean meal at four levels (0, 10, 20, and 30% wb), and extruded in a laboratory-scale extruder at speeds of 50 rpm (5.24 rad/sec) and 100 rpm (10.47 rad/sec) with temperature profiles of 80-90-100°C and 100-110-120°C. Processing conditions, including dough and die temperatures, drive torque, specific mechanical energy consumption, product and feed material throughput rates, dough apparent viscosity, and dough density, were monitored during extrusion. The resulting products were subjected to physical and nutritional characterization to determine the effects of processing conditions for these blends. Extrudate analysis included moisture content, water activity, crude protein, in vitro...

The effects of storage on flour quality and baking performance

Abstract In times of low wheat reserves, newly harvested wheat is processed almost immediately after harvest, which presents a series of problems to the millers and bakers. Newly harvested wheat generally has poor milling and baking quality. However, after wheat is aged, the bran is easier to separate from the endosperm, flour extraction increases, and ash content drops. These improvements have been related to posthar‐vest maturation and physical changes in the wheat kernel. On the other side of the milling process, freshly milled flour does not perform as well as flour that has been kept in storage. To address this issue, extra flour storage capacity is needed, or millers and bakers must add chemicals to their flours. Flour components change during aging. Aged soft wheat flour behaves similarly to chlorinated flour. Flour hydration rate and batter viscosity increase, and cakes have greater volumes without collapse. Aged hard wheat flour has higher water absorption, better mixing tolerance, and greater ga...

Effect of Flour Extraction Rate on White and Red Winter Wheat Flour Compositions and Tortilla Texture

ABSTRACTWheat flours commercially produced at 74, 80, and 100% extraction rates made from hard white winter wheat (WWF) and hard red winter wheat (WRF) were used to produce tortillas at a commercial-scale level. Flour characteristics for moisture, dry gluten, protein, ash, sedimentation volume, falling number, starch damage, and particle-size distribution were obtained. Farinograms and alveograms were also obtained for flour-water dough. A typical northern Mexican formula was used in the laboratory to test the tortilla-making properties of the flours. Then commercial-scale tortilla-baking trials were run on each flour. The baked tortillas were stored at room and refrigeration temperatures for 0, 1, 2, and 3 days. Maximum stress and rollability were measured every day. Tortilla moisture, color, diameter, weight, and thickness were measured for each treatment. Finally, tortilla acceptability was tested by an untrained sensory panel. Analyses of variance (ANOVA) were performed on the data. WWF had higher pro...