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.     

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.     

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.     

Wheat Germ Protein Flour Solubility and Water Retention

The effects of pH and temperature on water retention (WR), protein solubility (PS), and total solubility (TS) of defatted wheat germ protein flour (WGPF) were studied in a model system. PS of WGPF was compared with those of corn germ protein flour (CGPF), soy flour (SF), nonfat dried milk (NFDM), and egg white powder (EWP) at 1–8%. WR increased with increase in pH from 4 to 8. Maximum WR occurred at 70°C, and slight variations were observed between 5 and 30°C. PS and TS increased with increases in pH and temperature. PS of proteins was in the order of NFDM > EWP > SF > CGPF=WGPF. The results showed the potential for usage of WGPF in comminuted meats, beef patties, breads, cakes, and cookies.     

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.     

Response Surface Methodology for Reduction of Pinking in Cooked Turkey Breast Mince by Various Dairy Protein Combinations

Nonfat dry milk (NFDM), sodium caseinate (SC), whey protein concentrate (WPC), and combinations of each were evaluated for abilities to reduce pink color development in cooked, ground, uncured turkey breast. Protein treatments were also evaluated in the presence of pink-color-generating ligands (nicotinamide, 1%, sodium nitrite, 10 ppm, and sodium nitrate, 50 ppm) with and without ethylenedinitrilo-tetraacetic acid disodium salt (200 ppm). NFDM and WPC at levels as low as 1.5% were effective in reducing CIE a* values (P < 0.05) regardless of ligand treatment; SC was not. EDTA reduced pink color within all protein and ligand treatments. Poultry producers can reduce pink color development in further-processed products by selective addition of dairy proteins.     

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.     

The effects of different levels of non-fat dry milk and whey powder on emulsion capacity and stability of beef, turkey and chicken meats

The effects of different concentrations (0.00, 0.25, 0.50%) of either non‐fat dry milk (NFDM) or whey powder (WP) on emulsion capacity (EC) and emulsion stability (ES) of beef, chicken and turkey meats were studied by using a computer model system. The effects of meats types and additives (NFDM and WP) on EC and ES were found to be statistically significant (P < 0.01). Of the meats, chicken had the highest and beef the lowest values of EC and ES. When using different concentrations of WP and NFDM, 0.25% WP and 0.50% NFDM had the highest values of EC. The effect of different concentrations (0.25 and 0.50%) of WP was insignificant on ES; however, the effects of different concentrations (0.0, 0.25 and 0.50%) of NFDM were significant on ES.     

Ability of Various Dairy Proteins to Reduce Pink Color Development in Cooked Ground Turkey Breast

Dairy proteins were evaluated for their ability to reduce pink color in ground turkey samples. Sodium nitrite and nicotinamide were added to induce pink color formation. Nonfat dry milk (NFDM) and 1 of the whey protein concentrates (WPC) reduced CIE a* values in samples containing 10 ppm sodium nitrite. All of the dairy proteins tested reduced CIE a* values in nicotinamide-treated samples. In samples prepared without nicotinamide or nitrite, only WPC reduced CIE a* values, while the other proteins tested had no effect or increased redness. NFDM or specific WPC proteins could be used to reduce the pink color defect and increase yield.     

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.     

Emulsifying Property of Whey Peptide Fractions as a Function of pH and ionic Strength

Solubility and emulsifying properties of whey protein concentrate (WPC), heat-treated WPC (90°C, pH 2.5, 10 min), and their tryptic or chymotryptic peptide fractions obtained by ultrafiltration were measured from pH 3 to 9 at two ionic strengths (uμ=0 and 0.6). There was no correlation between solubility and emulsifying capacity (EC). Heat treatment induced some conformational changes in WPC, resulting in better EC. Some peptide fractions had better EC than proteins at pH 7 and 9. Treatments resulting in more hydrophobic peptides or a higheT content of larger peptides produced fractions with better emulsifying properties. pH and ionic strength affected conformation and emulsifying properties of proteins and peptides.     

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.     

Effect of microbial transglutaminase, sodium caseinate and non-fat dry milk on quality of salt-free, low fat turkey döner kebab

Effects of microbial transglutaminase (MTGase) and its combinations with sodium caseinate (SC) or non-fat dry milk (NFDM) on quality of salt-free, low fat turkey döner kebab were investigated. The purpose of this study was to prevent quality deteriorations (e.g. cooking loss, textural problems) caused by a lack of salt in the product. The results of this study indicated that the use of MTGase can minimize textural quality loss caused by a lack of salt in turkey döner manufacture (p < 0.05). When the enzyme was combined with SC, or NFDM, its effect on texture was enhanced (p < 0.05) and improved cooking yield, moisture and sensory properties compared to the corresponding control manufactured without the enzyme, salt, SC and NFDM. (p < 0.05), however, there was no significant effect on pH and color As a result, the possible quality problems which may occur in salt free, low fat turkey döner can be overcome by the use of combinations of MTGase with SC or NFDM.     

Structural and Functional Properties of Caseinate and Whey Protein Isolate as Affected by Temperature and pH

The structural properties, i.e., active sulfhydryl (SH), flexibility and hydrophobicity, and functional properties, i.e., solubility, emulsion activity (EA), emulsion stability (ES), foam overrun (FO) and foam stability (FS), of commercial sodium caseinate (SC) and whey protein isolate (WPI) solutions were investigated at pH 6, 7 and 8 and at 25, 55 and 65°C. WPI contained a higher concentration of active SH and was more hydrophobic than SC. WPI provided comparable solubility and EA, lower FO, but higher FS than SC. Temperature and pH effects on the two proteins were somewhat inconsistent.     

甘薯叶可溶性蛋白乳化性及其稳定性研究

以甘薯鲜叶为原料,采用碱提酸沉法提取甘薯叶可溶性蛋白(SPSPL),以甘薯叶压榨粉(SPLE)和大豆蛋白粉(SP)为参照,研究了pH、氯化钠浓度和温度等环境因素对甘薯叶可溶性蛋白乳化及其稳定性的影响。pH、氯化钠浓度和温度对甘薯叶可溶性蛋白乳化性影响较大。与SPLE和SP比较,SPSPL在碱性(pH10)范围内乳化性及其稳定性都较大,低盐浓度下(0.1mol/LNaCl)乳化性较大,但乳化稳定性随盐浓度的增加而降低,60℃时乳化性及其稳定性较好。     

Interfacial composition and stability of emulsions made with mixtures of commercial sodium caseinate and whey protein concentrate

The interfacial composition and the stability of oil-in-water emulsion droplets (30% soya oil, pH 7.0) made with mixtures of sodium caseinate and whey protein concentrate (WPC) (1:1 by protein weight) at various total protein concentrations were examined. The average volume-surface diameter (d₃₂) and the total surface protein concentration of emulsion droplets were similar to those of emulsions made with both sodium caseinate alone and WPC alone. Whey proteins were adsorbed in preference to caseins at low protein concentrations (<3%), whereas caseins were adsorbed in preference to whey proteins at high protein concentrations. The creaming stability of the emulsions decreased markedly as the total protein concentration of the system was increased above 2% (sodium caseinate >1%). This was attributed to depletion flocculation caused by the sodium caseinate in these emulsions. Whey proteins did not retard this instability in the emulsions made with mixtures of sodium caseinate and WPC.     

Effect of Whey Pretreatment on Composition and Functional Properties of Whey Protein Concentrate

The effect of pretreatment upon the composition and physicochemical and functional properties of whey, ultrafiltration (UF) retentate and freeze-dried and spray-dried whey protein concentrates (WPC) was investigated. Pretreatment was by cooling cheese whey to 0-5°C, adding calcium chloride, adjusting to pH 7.3, warming to 50°C, and removing the insoluble precipitate that formed by centrifugation or decantation. UF permeation flux rate of pretreated whey was about double that for control whey. Pretreated whey was essentially turbidity free, contained 85% less milkfat, 37% more calcium and 40% less phosphorus than whey. Pretreated whey WPC proteins were slightly more soluble at pH 3, but less functional for emulsification than whey WPC proteins. Neither whey WPC proteins nor pretreated whey WPC proteins was functional for foaming at 6% protein concentration.     

Comparing the heat stability of soya protein and milk whey protein emulsions

The heat stability of emulsions stabilized by WPC or SPI or mixtures of the two are compared by following the change in oil droplet number during heating, and applying kinetic rate equations to calculate the rate constant (k) for destabilization. SPI emulsions were found to be unstable to heat at pH around the pI, whilst being stable at pH further from the pI. This is related to the pH dependent solubility of soy proteins. This determined that a pH close to the pI (pH 4.5) be used for further studies so as to give a heat labile emulsion. Both WPC and SPI emulsions showed a weak dependence of k on protein concentration at pH 4.5, and an increasing k as the temperature increased. Arrhenius plots for emulsions made with WPC were bilinear, whilst those for SPI followed a single straight line. The change in slope of the Arrhenius plots for the WPC emulsions occurred around 70 °C, lower than would be expected from the denaturation temperature of β-lactoglobulin, the protein that dominates the thermal behaviour of WPC. The activation energies for WPC and SPI emulsions calculated from the slopes of the Arrhenius plots are slightly lower for WPC and considerably lower for SPI than the equivalent values in the literature for these proteins in solution. This, and the apparent lower denaturation temperature of β-lactoglobulin in emulsions, we explain by hypothesizing that the WPC and SPI proteins are already partially denatured by surface adsorption when they are heated, and thus require less energy to denature, and unfold at lower temperatures than native non-adsorbed proteins.     

Rheological and structural characterization of gels from whey protein hydrolysates/locust bean gum mixed systems

The gelling ability of whey proteins can be changed by limited hydrolysis and by the addition of other components such as polysaccharides. In this work the effect of the concentration of locust bean gum (LBG) on the heat-set gelation of aqueous whey protein hydrolysates (10% w/w) from pepsin and trypsin was assessed at pH 7.0. Whey protein concentrate (WPC) mild hydrolysis (up to 2.5% in the case of pepsin and 1.0% in the case of trypsin) ameliorates the gelling ability. The WPC synergism with LBG is affected by the protein hydrolysis. For a WPC concentration of 10% (w/w), no maximum value was found in the G′ dependence on LBG content in the case of the hydrolysates, unlike the intact WPC. However, for higher protein concentrations, the behaviour of gels from whey proteins or whey protein hydrolysates towards the presence of LBG becomes very similar. In this case, a small amount of LBG in the presence of salt leads to a big enhancement in the gel strength. Further increases in the LBG concentration led to a decrease in the gel strength.     

海鲜菇蛋白质功能特性及消化性的研究

以海鲜菇粉为原料,采用纤维素酶辅助碱提酸沉法提取出蛋白质,对其功能特性及消化性进行研究。结果表明,随着离子强度的增加,海鲜菇蛋白质的溶解性(Solubility)、持水性(Water holding)、乳化性(Emulsifying)及乳化稳定性(Emulsion stability)、起泡性(Foaming)及泡沫稳定性(Foaming stability)均呈现先升高后降低的趋势;随着蔗糖浓度的提高,溶解性逐渐降低,持水性、乳化性、起泡性及泡沫稳定性呈现先升高后降低的趋势,乳化稳定性呈现先降低后升高的趋势;随着温度的提高,溶解性、持水性、持油性(Oil holding)、乳化性及乳化稳定性、起泡性及泡沫稳定性均呈现先升高后降低的趋势;随着pH的升高,溶解性、起泡性、乳化性及乳化稳定性均呈现先降低后升高的趋势,在等电点附近达到最小值,泡沫稳定性呈现先升高后降低的趋势,在等电点附近达到最大值。海鲜菇蛋白质溶液经过模拟胃消化后,其消化率为35.5%,水解度17.13%,游离氨基酸含量0.42 mg/mL,多肽含量1.16 mg/mL,胃消化液还原力0.55,DPPH·、O2-·和·OH的清除率分别为66.14%、67.36%和69.44%;模拟肠消化后,其消化率为87.65%,水解度20.88%,游离氨基酸含量0.93 mg/mL,多肽含量0.83 mg/mL,肠消化液的还原力0.23,DPPH·、O2-·和·OH的清除率分别为35.02%、27.17%和37.75%。通过试验证明了离子强度、温度、时间和蔗糖浓度对海鲜菇蛋白质的功能特性有一定影响;该蛋白质在胃肠中消化率较高,是一种易消化优质蛋白质。