Foaming Properties of Selected Plant and Animal Proteins

The foaming properties of proteins are important in predicting their fnnctionality in aerated foods. In model aqueous systems, foam expansion (FE) and foam stability (FS) of commercial plant proteins, wheat germ protein flour (WGPF), corn germ protein flour (CGPF), and soy flour (SF), were compared with those of nonfat dried milk (NFDM) and egg white powder (EWP) at 1, 2, 4, 6, and 8% using one- and two-way analyses of variance. The effects of pH 4, 5, 6, 7, and 8 on FE and FS of WGPF were also measured. The highest overall FE and FS were obtained for EWP. Among plant proteins, FE and FS were maximum for CGPF and SF, respectively. FS was lowest for NFDM. Except for SF, FE and FS increased with increasing protein concentration. The FE and FS of WGPF were highest at pH 8, lowest at pH 7, and intermediate at pH 4–6.     

Protein Solubility, Water Retention, and Fat Binding of Corn Germ Protein Flour Compared with Milk Proteins

Protein solubility (PS), water retention (WR), and fat binding (FB) of corn germ protein flour (CGPF), nonfat dry milk (NFDM), whey protein concentrate (WPC), and sodium caseinate (SC) were comparatively studied using response surface methodology. PS and WR of all samples were affected by pH except for WR of CGPF. PS and WR of all samples were not affected by incubation temperature except of WR of CGPF. Incubation temperature influenced FB of CGPF and WPC but not of NFDM and SC. Sample concentration significantly affected FB of all samples. CGPF was an effective protein source in terms of WR and FB. For FB, SC > CGPF = NFDM > WPC and for PS, WPC=NFDM=SC > CGPF.     

Water Retention and Solubility of Soy Proteins and Corn Germ Proteins in a Model System

Response surface methodology was used to study water retention and protein solubility of soy flour (SF), concentrate (SC), and isolate (SI), and corn germ protein flour (CGPF). Water retention increased with pH (6 to 8) and incubation temperature (10–70°C), but not with increasing incubation time (10–30 min). SC had highest water retention per gTam, followed by CGPF, SF, and SI. Water retention in relation to protein content was higher in CGPF than in the three soy products. Protein solubility was significantly affected by pH and temperature of incubation. Protein solubility increased when pH (6 to 8) and incubation temperature increased (30–70°C) in all samples. SI had highest protein solubility, and CGPF had the lowest.     

Functionality of Wheat Germ Protein in Comminuted Meat Products as Compared with Corn Germ and Soy Proteins

Wheat germ protein flour (WGPF), corn germ protein flour (CGPF), and soy flour (SF) were used as additives at a level of 3.5% in comminuted meat products (CMP). Frankfurters with protein additives showed increased water-holding capacity and batter stability and decreased cooking loss. Improved viscosity and adhesiveness were observed with protein additives when the level of added water was constant. Protein additives also influenced textural and sensory properties of frankfurters. WGPF at a level of 3.5% was found similar to effects of SF and CGPF. WGPF is a potential nonmeat protein additive that can be utilized as an extender in CMP such as frankfurters and bologna.     

Emulsifying Capacity and Emulsion Stability of Milk Proteins and Corn Germ Protein Flour

Comparative studies of emulsifying capacity (EC) and emulsion stability (ES) of corn germ protein flour (CGPF), nonfat dry milk (NFDM), whey protein concentrates (WPC), and sodium caseinate (SC) were carried out using response surface methodology. CGPF was an effective stabilizer of fat-protein-water emulsions. Tested proteins showed the following trend in EC and ES: SC > WPC = NFDM > CGPF. EC and ES increased with increased concentration of protein. No effect of incubation temperature on EC and ES of these proteins was detected. All protein samples showed a maximum EC at high pH (near 8.0) and 1.0% concentration under test conditions, except NFDM (about pH 7.0). Minimal pH effect on ES was found.     

Emulsifying Capacity and Emulsion Stability of Soy Proteins Compared with Corn Germ Protein Flour

Both emulsifying capacity (EC) and emulsion stability (ES) increased with increasing concentrations from 0.4% to 0.8% of soy flour (SF), soy concentrate (SC), soy isolate (SI) and corn germ protein flour (CGPF) when studied by response surface methodology. EC and ES increased as pH increased from 6 to 8 in all samples. Increasing incubation temperatures of protein solutions from 20–70°C or from 4–20°C did not affect EC or ES, respectively. SF had the highest EC, followd by SI, SC, and CGPF.     

COMPARATIVE STUDY OF CORN GERM AND SOY PROTEINS UTILIZATION IN COMMINUTED MEAT PRODUCTS1

Soy flour (SF), soy concentrate (SC) and corn germ protein flour (CGPF) at 3.5%, or 2% of soy isolate (SI) were incorporated in the formulations of frankfurters. There was no significant differences in proximate composition of frankfurters containing SF, SC. SI, and CGPF. Frankfurters formulated with high plant protein flour had lower cholesterol, and higher protein content than the all-meat control frankfurters. Control frankfurters had lower water holding capacity and higher cooking losses than those containing plant proteins. No significant differences (P < 0.05) were found in textural and color characteristics. Atypical aroma and flavor profiles increased in frankfurters with SF nd CGPF extension.     

FUNCTIONALITY OF MILK PROTEINS AND CORN GERM PROTEIN FLOUR IN COMMINUTED MEAT PRODUCTS1

Effects of corn germ protein flour (CGPF), nonfat dry milk (NFDM), whey protein concentrate (WPC), and sodium caseinate (SC) on quality characteristics of comminuted meat products were studied. Water holding capacity (WHC) was lowest and cooking loss was highest for the control formulation, whereas formulations extended with CGPF and milk proteins were higher in WHC and lower in cooking losses. Shear force and firmness increased as extenders were added, except WPC. All frankfurters with extenders were firmer than the control, except those extended with WPC. Hue angle was highest for samples with CGPF, while no differences were found in hue angle between control and milk proteins containing samples, except samples with WPC. Frankfurters with CGPF and SC add had a stronger atypical aroma than the control. Meaty aroma score was higher for the control than for the other products, except those with WPC. Meaty flavor score was higher for the control than for all other products. The product with CGPF added had a stronger atypical flavor than the control. Frankfurters containing extenders were not as juicy as the all-meat control.     

COMPARATIVE STUDY OF SHELF-LIFE OF FRANKFURTERS CONTAINING PLANT PROTEIN ADDITIVES1

Soy flour (SF), soy concentrate (SC), soy isolate (SI) and corn germ protein flour (CGPF) were incorporated in frankfurters. The sensory analysis, chemical, and microbiological tests were conducted to investigate the effect of plant proteins on stability during vacuum-packaged storage. No significant difference in meaty aroma was found between all samples after 45 days storage. Atypical flavor and aroma of all samples, including the all-meat control increased (P < 0.05) after 45 days storage. A tendency was found of increase in atypical aroma and flavor with increase in total volatile nitrogen values and total psychrophiles during storage. Salty flavor increased with storage time in experimental samples, but juiciness decreased. Samples containing SF and SC had higher total volatile nitrogen than SI and CGPF containing samples at 2, 30 and 45 days of storage. No significant differences were found in TBA values between tested samples, except higher TBA values for SI containing samples. There was no significant difference among samples in total psychrophilic counts.     

Microstructure of Frankfurters Extended with Wheat Germ Proteins

Transmission electron microscopy was utilized to study the microsctructure of frankfurters extended with wheat germ protein flour (WGPF) at 3.5, 5.0, and 7.0%. Samples with 3.5% WGPF showed a denser matrix than the control. They also had a uniform interfacial protein film (IPF) with a slight increase in average thickness. At WGPF >3.5%, no further effects on IPF were observed. At 7.0% WGPF, an increase in added water, and the resultant dilution of meat and fat components, resulted in fewer fat globules, some with incomplete IPFs. Proteins in the WGPF contributed to IPF formation up to a specific level. Nonprotein components also were important in batter stability by absorbing water.     

Corn Germ Protein Flour as an Extender in Broiled Beef Patties

Beef patties were extended at levels of 10, 20, and 30% of the uncooked weight with hydrated defatted corn germ protein flour (CGPF). Extended patties had lower cooking losses and higher cooked yields than control patties. Adding CGPF did not affect moisture or fat contents in broiled patties, but lowered protein content. The amino acid composition of experimental patties was comparable to that of the control. The water-holding capacity and pH of raw patties increased with increasing levels of added CGPF. Incorporation of CGPF affected sensory characteristics of the product; meaty aroma and flavor of all-meat patties was significantly higher than experimental samples and decreased with an increase in added CGPF. CGPF has potential use as an extender in coarsely ground meats.     

QUALITY CHARACTERISTICS OF MEAT BATTERS AND FRANKFURTERS CONTAINING WHEAT GERM PROTEIN FLOUR1

Frankfurters were extended with wheat germ protein flour (WGPF) at 3.5, 5.0. and 7.0%. Water added during formulation was increased by 2% for every 1% of WGPF added. Batters containing WGPF had higher pH and adhesiveness values. Viscosities of the batters were not affected by addition of WGPF. Batters containing WGPF had lower cooking losses, and lower percent water and fat separated. Positive effects, such as lower cooking losses, higher processing yields and lower percent fat, were not consistent at levels of WGPF beyond 3.5%, probably because of higher levels of added water. Total yields of the samples containing WGPF were higher than those of control samples. No differences were observed in protein and amino acid contents of samples. Lower fat content was found in samples extended with 7.0% WGPF. Frankfurters containing WGPF had lower shear force and firmness values. Differences in color of frankfurters were also observed.     

Quality of Broiled Beef Patties Supplemented with Wheat Germ Protein Flour

Quality characteristics of ground beef patties, supplemented with hydrated wheat germ protein flour (WGPF) at levels 2.0, 3.5, and 5.0% were studied. Water-holding capacity decreased and pH increased with addition of WGPF. Water activity was not affected. Supplemented beef patties had lower cooking losses and changes in diameter and higher yields than control patties. Supplemented beef patties exhibited lower shear force and compression values than all-meat patties. No differences were found in wheat-like aroma and flavor. WGPF has potential for use as an extender in ground meat products.     

Peanut Protein Film as Affected by Drying Temperature and pH of Film Forming Solution

Films were made from peanut protein concentrate solution of pH 6.0, 7.5 or 9.0, and dried at 70, 80 or 90°C. Both total solubility and protein solubility of film decreased with increasing temperature but increased with increasing pH. Film color was darker and more yellow when pH increased. Tensile strength (TS) and elongation (E) increased but water vapor permeability (WVP) and oxygen permeability (OP) decreased as temperature increased. At pH 9 and 90°C, film had the lowest WVP and OP, and the highest TS.     

Thermal and dynamic rheological properties of wheat flour fractions

A commercial high gluten flour (HGF) was fractionated into prime starch (PS), tailing starch (TS), and gluten (G). Fractions were examined alone or in various combinations. Dynamic rheological properties of samples were measured in an oscillatory rheometer (strain 0.02; frequency 0.1 Hz) during heating at 1°C/min. Thermal characteristics of samples were determined by differential scanning calorimetry (DSC) at a heating rate of 10°C/min. The loss (G″) and storage (G′) moduli of PS and mixed G/PS, G/TS, and G/PS/TS increased after 60°C, reaching peak values (e.g. 81, 301, 313, and 3000 Pa in G′, respectively) around 75°C after which the moduli decreased. HGF showed a steady increase in G′ from 32 to 2490 Pa as temperature increased from 65 to 90°C, indicating continuous formation of elastic networks. Cooling increased G′ for G/PS/TS, decreased G′ for HGF, and produced no rheological transitions for all samples. TS and G alone did not exhibit appreciable viscoelastic responses to the heating and cooling temperatures. DSC measurements revealed a major endothermic transition in HGF. This transition, with a peak around 60°C, was due to starch gelatinization. The presence of G or TS resulted in reduced melting enthalpies of starch in the PS fraction. Gluten or TS fractions alone or in combination did not exhibit any endothermic transitions.     

Novel Radiofrequency‐Assisted Thermal Processing Improves the Gelling Properties of Standard Egg White Powder

Effect of radiofrequency (RF)‐assisted thermal processing on quality and functional properties of high‐foaming standard egg white powder (std. EWP, pH approximately 7.0) was investigated and compared with traditional processing (heat treatment in a hot room at 58 °C for at least 14 d). The RF‐assisted thermal treatments were selected to meet the pasteurization requirements and to improve the functional properties of the std. EWP. The treatment conditions were: RF heating to 60, 70, 80, and 90 °C followed by holding in a hot air oven at those temperatures for different periods ranging from 4 h at 90 °C to 72 h at 60 °C. The quality (color and solubility) and functional properties (foaming properties: foaming capacity and foam stability; and gelling properties: water holding capacity and gel‐firmness) of the std. EWP were investigated. RF‐assisted thermal processing did not affect the color and solubility of std. EWP at any of the treatment conditions. In general, the foaming and gelling properties of RF‐assisted thermally processed std. EWP increased with an increase in temperature and treatment duration. The optimal RF‐assisted treatment conditions to produce std. EWP with similar functional properties as the traditionally processed (hot room processed) std. EWP were 90 °C for ≥8 h. These optimal conditions were similar to those for high gel egg white powder (HG‐EWP, pH approximately 9.5). The RF‐assisted thermal pasteurization improved the gelling properties of std. EWP to the levels of HG‐EWP, leading to newer applications of this functionally improved safe product. The RF‐assisted thermal processing allows the processor to produce a HG‐EWP from std. EWP subsequent to processing while simultaneously pasteurizing the product, thus assuring the product safety.     

Natural fermentation of lentils. Functional properties and potential in breadmaking of fermented lentil flour

The effects of fermentation on functional properties of lentil flour and rheological properties of doughs and breads produced from blends of wheat and fermented lentil flour were studied. Lentil protein solubility was higher at neutral pH than acid pH; the lowest and highest protein solubility values were observed at pH 4.0 and pH 7.0, respectively. Water hydration capacity and fat binding capacity of fermented lentil flour (FLF) were always higher than those of non-fermented lentil flour (NFLF), irrespective of fermentation temperature (28–42°C) and flour concentration (79–221 g/l). Emulsifying properties of NFLF were similar to the properties of other legume flours in the range used in experiment. In contrast, the emulsion capacity and stability of FLF were very low and flours fermented at 42°C did not even form emulsion. Rheological properties of doughs made from wheat-fermented lentil blends were similar to those from wheat flour with the addition of other legume flours such as pea and bean. Good quality breads were produced at 2.5 to 10% NFLF and FLF supplementation (except for bread with 10% FLF addition which was middle quality).     

Influence of extrusion variables on the protein in vitro digestibility and protein solubility of extruded soy tarhana

Tarhana, supplemented with 150 g kg⁻¹ full‐fat soy flour, was extruded at different extrusion conditions (barrel temperature: 80–120°C; screw speed: 100–300 rpm; feed rate: 10–20 kg h⁻¹ ) using a twin‐screw extruder. The effect of extrusion conditions on the in vitro digestibility (PD) of the protein and protein solubility (PS) was investigated using response surface methodology. Regression equations for predicting PD and PS were developed. While the barrel temperature had a significant effect on PD (P <0.1), feed rate was the most significant variable on PS of the samples (P<0.05). Since the protein solubility should be high for the instant properties of extruded soy tarhana soup, it is suggested that soy tarhana should be extruded at low feed rates (ie high residence times) while high barrel temperatures should be achieved for the inactivation of antinutritional factors present in the soy flour. © 1999 Society of Chemical Industry     

Functionality of Six Nonmeat Proteins in Meat Emulsion Systems

The emulsion stabilizing and textural effects of six nonmeat proteins, identified by brand name and manufacturers were investigated. Included were: Soy protein isolate (SPI), soy protein concentrate (SPC), soy flour (SF), milk protein hydrolysate (MPH), autolyzed yeast (AY), and spray dried nonfat dry milk (NFDM). SPI and NFDM were most effective, while SF and AY were least effective in emulsion stabilization. Bind value constants (Saffle system) were developed for each nonmeat protein. Mean compression values for all the nonmeat proteins except SPI decreased with increasing levels of the additives. The functional values derived in this study are specific for these nonmeat proteins and may not be applicable to other nonmeat proteins of a similar nature.