Factors Influencing Zein-Whole Sorghum Flour Dough Formation and Bread Quality.

Zein is known to able to form viscoelastic dough with wheat-like properties under certain conditions. Several studies have been conducted to explain the mechanism behind this ability and to improve the functionality and end-use quality of zein-based dough systems. However, most of this research has been conducted using zein in combination with isolated starches or high-starch flours. To investigate the production of additional zein-whole sorghum flour breads, experiments were conducted to determine factors impacting zein-whole sorghum flour dough and bread quality. Optimizing water levels, using defatted zein and/or sorghum flour, and increasing zein content in dough formulas were investigated as initial formulation steps. Of these factors, increasing zein content from 20% to 30% (flour weight basis) had the greatest impact, resulting in stronger zein-based dough and improved bread quality. Additives and zein treatments shown to impact zein functionality were then investigated for their effect of zein-whole sorghum flour breads. Mixing zein and whole sorghum flour with 0.5% hydrogen peroxide, 5% ethanol, or 3% hydroxypropyl methylcellulose resulted in improved dough strength and bread quality. Breads made from whole white sorghum flour had improved quality compared to zein-based breads made with black or high-tannin whole sorghum flour. PRACTICAL APPLICATION: Zein is known to be able to form wheat-like dough when mixed under the right conditions. Most of the research on zein-based dough and food products has used high-starch flours. This project investigated optimizing the production of zein-whole sorghum flour dough and bread as an alternative. Increasing the zein content in the formula and using additives including ethanol and HPMC produced breads from zein-whole sorghum flour that were like those made with zein and pure starch.

Reducing Visual Differences in Whole Grain Bread Prepared with Hard Red and Hard White Wheat: Application for Sensory Studies.

Consumer taste preference can be influenced by visual preference. To eliminate the influence of visual preference in the sensory evaluation of whole grain wheat, a reproducible method to eliminate color differences between Whole Grain breads prepared from hard white wheat (HWW) and hard red wheat (HRW) was evaluated. Response surface methodology (RSM) was used to match the color of HWW to HRW with the addition of commercially available dye solutions: McCormick black (red #40, yellow #5, blue #1), red (red #40, red #3, yellow #6), and yellow (yellow #5). Bread color was assessed by L* , a* , and b* color parameters according to the CIELAB international system of color measurement. Four replicates of the control and dye treated breads were analyzed. Initial color values for HRW were L* = 56.8 ± 0.40; a* = 8.04 ± 0.44; b* = 21.34 ± 0.46. RSM was used to predict dye addition levels to match color between HWW and HRW. With the addition of black (0.457 µL/mL), red (0.574 µL/mL), and yellow (1.165 µL/mL) dye to HWW, breads could be produced with L* , a* , and b* values of no statistical difference to the HRW (P < 0.05). A timed storage trail demonstrated the need to standardize the time between bread production and feeding studies. Visual bias can hinder assessment of wheat varieties in sensory studies. A reproducible method of dying wheat was developed that can be used to reduce this bias in sensory studies. PRACTICAL APPLICATIONS: The ability to control color variability is a critical tool in determining perceived quality in sensory analysis of breads. In this study, a method to reduce or eliminate visual bias between breads made from different varieties of wheat was developed. This method is applicable to any foods where dye could be added to reduce or eliminate color bias in sensory studies.

Characterization of rheological and structural properties of a gum from Balangu seeds.

With the growing interest in all-natural foods, there has been increased study of sustainable natural sources of polysaccharides with suitable functional properties. Lallemantia royleana seed polysaccharide is one such material. Water-soluble polysaccharides were isolated from L. royleana seed to evaluate their chemical structure and rheological properties. The polysaccharide was consisted of neutral (62.9% w/w) and acidic (16.7% w/w) sugars. The backbone of the isolated rhamnoarabinogalactan was composed of (1 → 4)-linked galactopyranose residues. The weight average molecular weight (Mw) of the polysaccharide was 0.777 × 106 g/mol. Rheological behavior of extracted gum was studied at different concentrations (0.1-2.0%; w/v) and temperatures of 5-50 °C. The extracted gum showed typical non-Newtonian and shear thinning behavior at all concentrations and temperatures. However, higher apparent viscosity was observed with increasing gum concentration or decreasing temperature. The quantification of flow activation energy using Arrhenius model showed a decrease from 29,931 to 8339 kJ/mol-1. The mechanical spectra indicated viscoelastic behavior of the gum in all samples. Dynamic moduli increased with increased frequency and G' was always greater than G″, indicating a weak gel system. The results of this study will help to increase potential applications of L. royleana polysaccharide in various food formulations.

Enhanced functionality of pea-rice protein isolate blends through direct steam injection processing.

Direct steam injection (DSI) processing with pH adjustment was investigated to enhance the functionality of pea-rice protein isolate blends (PR). Protein slurries at concentration of 5%(w/w) of commercial pea and rice protein isolates in the ratio of 2:1(w/w) across a range of steam temperatures (66-107°C) and pH values (2-11) were studied. After DSI treatment, the PR were freeze-dried to obtain the final dry protein powder. Based on protein solubility profiles, the optimal DSI processing conditions were 107°C and pH 11. Available lysine was not reduced (P>0.05) in the blend. Solubility (from 3 to 41%, at pH 7), emulsifying activity index (from 5.9 to 52.5m2/g), foam stability (from 68.2 to 82.8%), and oil holding capacity (from 1.8 to 4.9g/g) values increased (P<0.05) compared to the untreated PR. DSI can modify the functionality of PR without affecting the essential amino acid composition.

Effect of Salt and Ethanol Addition on Zein-Starch Dough and Bread Quality.

Development of viscoelastic doughs from non-wheat proteins allows for a wider range of gluten-free products. Little work has been completed to describe mechanisms of zein functionality in food systems. To identify factors responsible for dough development in zein-starch mixtures and their influence on zein bread quality, a mixture of 20% zein-80% maize starch was mixed with water and various reagents. Salts, NaSCN, NaCl, and Na2 SO4 were evaluated at concentrations from 0 to 2M for their influence on the properties of zein-starch dough systems. NaSCN at low concentrations produced softer dough. Ethanol treatments produced softer more workable dough in the absence of salts. Increasing concentrations of NaCl and Na2 SO4 resulted in coalescing of the proteins and no dough formation. The addition of ß-ME had minimal softening effects on zein-starch dough. Specific volumes of zein-starch bread increased with decreasing NaCl addition in bread formulations. Likewise, including 5% ethanol (v/v) in the bread formula increased bread quality.

The Effects of Egg and Diacetyl Tartaric Acid Esters of Monoglycerides Addition on Storage Stability, Texture, and Sensory Properties of Gluten-Free Sorghum Bread.

The impact of whole egg addition (as is) at 20%, 25%, or 30% (flour basis) on sorghum bread quality was evaluated. The use of the antistaling agent diacetyl tartaric acid esters of monoglycerides (DATEM) at 0.5% (flour basis) at each of the egg addition levels was also studied. Evaluated quality factors included color, specific volume, and crumb structure. Texture analysis was performed to evaluate the rate of quality loss based on changes in crumb hardness values over time. A trained sensory panel evaluated bread quality attributes by descriptive analysis. Sorghum breads with egg had larger specific volumes than the control, while DATEM had a negative effect on the volume of sorghum gluten-free bread. Inclusion of egg in the bread formula improved cell structure and produced darker crust (P < 0.05). The addition of egg reduced bread hardness and slowed the rate of quality loss over a 12-d storage period. Descriptive analysis confirmed the findings of texture analysis. Control breads were significantly harder (P < 0.05) than egg-containing bread at days 0 and 4. This research demonstrates that addition of eggs to a gluten-free sorghum bread formulation results in improved storage stability and better overall quality and acceptability of the product.

Role of non-covalent interactions in the production of visco-elastic material from zein.

The role of non-covalent interactions in the formation of visco-elastic material from zein was investigated. Hydrophobic interactions were evaluated through the addition of various salts from the Hofmeister series. Urea, ethanol, and beta mercaptoethanol (ß-ME) were used to evaluate the effects of protein denaturation and disulfide bonds on zein's ability to form a visco-elastic material. The addition of NaI and NaSCN altered the properties of visco-elastic materials made from zein, making them softer and more extensible, as did urea and ethanol. The addition of NaCl and Na2SO4 negatively impacted the ability of zein to from a visco-elastic material and at higher concentrations completely disrupted the formation of visco-elastic material. These results indicate that manipulating non-covalent interactions in zein can alter and in some cases, completely disrupt the formation of a visco-elastic material. Specifically this may be due to disruption of hydrophobic interactions within individual zein proteins or interactions between proteins. The reducing agent ß-ME had little effect on zein's ability to form a visco-elastic material. Therefore, the visco-elastic properties of zein arise as a result of non-covalent interactions.

Composition and molecular weight distribution of carob germ protein fractions.

Biochemical properties of carob germ proteins were analyzed using a combination of selective extraction, reversed-phase high-performance liquid chromatography (RP-HPLC), size exclusion chromatography (SEC) coupled with multiangle laser light scattering (SEC-MALS), and electrophoretic analysis. Using a modified Osborne extraction procedure, carob germ flour proteins were found to contain approximately 32% albumin and globulin and approximately 68% glutelin with no prolamins detected. The albumin and globulin fraction was found to contain low amounts of disulfide-bonded polymers with relatively low M(w) ranging up to 5 x 10(6) Da. The glutelin fraction, however, was found to contain large amounts of high molecular weight disulfide-bonded polymers with M(w) up to 8 x 10(7) Da. When extracted under nonreducing conditions and divided into soluble and insoluble proteins as typically done for wheat gluten, carob germ proteins were found to be almost entirely ( approximately 95%) in the soluble fraction with only ( approximately 5%) in the insoluble fraction. As in wheat, SEC-MALS analysis showed that the insoluble proteins had a greater M(w) than the soluble proteins and ranged up to 8 x 10(7) Da. The lower M(w) distribution of the polymeric proteins of carob germ flour may account for differences in functionality between wheat and carob germ flour.