On the functional properties of globulin and albumin protein fractions and flours of African locust bean (Parkia biglobossa)

Albumin (ALBa) and globulin (ALBg) fractions of African locust bean were isolated and the functional properties were compared with its defatted (ALBdf) and undefatted flours (ALBf). Albumin had minimum % solubility (56.7%) at pH5, while minimum solubility was observed at pH4 for globulin and the flours. In all the samples studied, maximum solubility was observed at pH 10. A pH-dependent gelation study revealed that all of the samples had the highest least gelation concentration at pH10 apart from ALBf which had 16% w/v LGC at pH 2. Initial increase in ionic strength of the medium, to 0.4 and 0.6 M, enhanced the gelation capacity of protein fractions and flours, respectively, while further increase in ionic strength reduced it. Oil absorption capacity was maximal in ALBa while ALBf had the least value of 1.05 ml/g. Initial increase in ionic strength, up to 0.4 M, increased the water absorption capacity (WAC) of albumin fractions while WACs of the globulin fraction and flours were reduced when the ionic strength of the media reached 0.4 M. Foam capacity increased as the concentration of protein solution increased but was reduced by 6% w/v in ALBf. Initial increase in ionic strength enhanced both foam capacity and stability. Maximum EA was observed at pH 10 in all samples apart from ALBf, which reached a peak EA value at pH 2. ES (emulsion stability) was maximal at pH 10 for ALBa and ALBg while the same values were observed for ALBdf and ALBf at pH 2 and 10. Increasing the ionic strength, to 0.4 M, enhanced the EA and ES of ALBa while further increase in ionic strength, to 0.7 M, improved EA of ALBf but reduced the ES. Both EA and ES of ALBf reached peak values in 0.2 M solutions but no fixed pattern was observed in the response of ALBdf to various ionic strengths of the solutions.     

The acylated protein derivatives of Canavalia ensiformis (jack bean): A study of functional characteristics

Protein concentrate was prepared from jack bean (JNP) and it was modified by acylation using acetic (JAP) and succinic anhydrides (JSP). Proximate analyses revealed that moisture and ash content increased following acetylation and succinylation, while both acetylation and succinylation reduced percentage crude fat and protein. Acetylation and succinylation reduced protein solubility in the acidic pH range below the isoelectric point (4.5) of the protein concentrate but improved the solubility of the unmodified protein concentrate at the isoelectric point and pH range alkaline to the isoelectric point. Both acetylation and succinylation increased the water absorption capacity of unmodified protein concentrates at all levels of ionic strength investigated (0.1-1.0 mol/l). Acetylation improved oil absorption capacity whereas the tendency to absorb oil reduced after succinylation. Maximal emulsifying activity of native and modified proteins were obtained at pH 10. Emulsion stability of acylated proteins was higher than those of native proteins in the range of pH 4-10 but lower when the pH was 2. Foam capacity and stability of both native and modified proteins increased with increase in protein concentration. Foam capacity of modified proteins increased progressively with increase in pH from 2 to 10. Also, acylated protein derivatives had improved foam capacity over the native protein except at pH 2. Gelation capacity of both native and modified proteins was maximal at the region of isoelectric point.     

Functional properties of native and chemically modified protein concentrates from bambarra groundnut

Protein concentrate (BNP) was prepared from bambarra groundnut (Voandzeia subterranean) and it was derivatised with succinic (BSP) and acetic anhydride (BAP). Chemical composition revealed significant (P < 0.05) increases in the moisture and ash contents following modifications, while the crude fat was reduced. Protein solubility reduced with increase in pH of the solution until it reached isoelectric points of 3, 3.5 and 4 for BSP, BAP and BNP, respectively, following which steady increases were observed for the proteins as the pH increased. The results indicate an initial increase in emulsifying activity (EA) with increase in protein concentration. Both acetylation and succinylation improved the emulsifying stability of the native protein. Foaming capacity of both native and modified proteins increased with increase in protein concentration. Except at pH 2, where BNP recorded higher foam capacity than the modified proteins, at all other pHs studied, both succinylation and acetylation improved foam capacity. Gelation studies revealed that initial increase in ionic strength enhanced gelation properties, while gelation capacities reduced at higher salt concentrations.     

Characteristics of Isolation and Functionality of Protein from Tomato Pomace Produced with Different Industrial Processing Methods

The seeds separated from tomato pomace may contain valuable protein with unique functional properties. The objectives of this research were to study the impact of industrial hot and cold break tomato processes on protein isolation from defatted tomato seed meal and determine the protein-related functional properties of defatted and non-defatted seed meals. The results showed that the high temperature of hot break process denatured the protein, resulting in the lower protein extraction yield from 9.07 % to 26.29 % for defatted hot break tomato seed (DHTS) compared to from 25.60 % to 32.56 % for defatted cold break tomato seed (DCTS) under various extraction conditions. Hot break process also significantly influenced protein-related functional properties of seed meals. Compared to DCTS, DHTS had higher water absorption capacity (WAC) and oil absorption capacity (OAC) based on the protein weight in the seed meal, but lower emulsifying ability (EA), emulsifying stability (ES), foaming capacity (FC), and foaming stability (FS) based on the whole seed sample weight. When compared to commercial soybean protein isolate (SP), the meals of hot break tomato seed (HTS), DHTS, and DCTS showed higher bulk density and WAC values. The FC and FS of tomato meals were inferior while the ES was superior to SP. High alkaline pH was beneficial to the protein extraction and achieved better EA, ES, FC and FS of all the samples. The results indicated that tomato seed meals have a great potential to be used as functional food ingredients.     

Functional properties of plant proteins Part 6. Some functional properties of succinylated protein isolates from sunflower seed (Helianthus annuus L.)

The reaction of raw globulin preparations from sunflower seed with a 10-30-fold excess of succinic anhydride results in a maximum blockage of 85-92% of the protein amino groups. The water absorption of the protein increases 2-fold after a 26 % succinylation and nearly 6-fold after an exhaustive modification. The oil absorption decreases after a moderate (42 %) succinylation of the protein and reaches the value of unmodified protein after being exhaustively modified. The emulsifying capacity (EC) is highest in the native unmodified protein. Treatment with acidic aqueous butanol for removing phenolic compounds results in a decrease of EC. The latter increases again after an exhaustive succinylation of butanol-treated protein. A high level of modification (≥67%) improves the emulsifying activity and the emulsion stability of the protein. Succinylation increases the foam capacity but does not influence the high foam stability of the protein. A broadening of the solubility minimum and a shift of its position from pH 4.5-5.5 to pH 2.5-4.8 takes place at high levels of chemical modification. Relations are discussed between the dissociation of the protein into the summits at a high level of substitution (≥80%) determined by gel electrophoresis and the functional properties.     

鹰嘴豆分离蛋白质的功能性质

碱溶酸沉法制备鹰嘴豆分离蛋白质,其蛋白质含量为91.53%。研究各种外部条件如温度、pH、离子强度、离子种类对鹰嘴豆分离蛋白质溶解性的影响以及pH、离子强度对乳化能力及乳化稳定性的影响。     

鹰嘴豆分离蛋白的乳化性及结构关系

研究了蛋白质浓度、加油量、pH及离子强度对鹰嘴豆分离蛋白的乳化活力及乳化稳定性的影响。在蛋白质的等电点pH50时,乳化活力最小,乳化稳定性最高;离子强度增加,乳化活力呈现先降后升,而乳化稳定性表现为先升后降的趋势,当离子强度为02时,乳化活力最低而乳化稳定性最高。为了解释这一现象,研究了pH及离子强度对蛋白质的二级结构及表面疏水性的影响。结果表明,蛋白质的二级结构及表面疏水性随溶液的pH及离子强度的变化而变化,在蛋白质的等电点或离子强度较低(如01)时,蛋白质的二级结构主要以α螺旋形式存在,且当离子强度为01时,蛋白质的表面疏水性最低。     

马铃薯淀粉废水蛋白的功能特性

以碱提酸沉法制备的马铃薯淀粉废水蛋白为原料,分别考察了pH值、NaCl浓度和温度对蛋白功能特性（溶解性、持水能力、乳化性及乳化稳定性、起泡性及泡沫稳定性）的影响。结果表明,pH值、NaCl浓度和温度对蛋白的功能特性产生不同程度的影响。在等电点（pH 4.0）时,马铃薯蛋白表现出最低的溶解性、持水性、乳化性、乳化稳定性及起泡性,而泡沫稳定性最好。在较低NaCl浓度（＜0.2 mol/L）时,蛋白溶解性、持水能力、乳化性和乳化稳定性随NaCl浓度的增加而提高,而高浓度的NaCl（＞0.2 mol/L）对上述性质具有抑制作用;蛋白的起泡性和泡沫稳定性在NaCl浓度为0.4 mol/L时具有最大值。在4～80 ℃范围内,蛋白质的各项功能性质随温度的升高均呈现先增加后降低的趋势,且溶解性、持水性、乳化稳定性、起泡性及泡沫稳定性在40 ℃时最佳,乳化性在60 ℃最佳。     

Physicochemical,functional and cooking properties of under explored legumes,Canavalia of the southwest coast of India

Nutritionally potential under explored wild legumes viz., Canavalia cathartica and Canavalia maritima are widely distributed in mangroves and sand dunes, respectively, in Southwest coast of India. Physicochemical, functional and cooking properties of dried seeds of these legumes have been evaluated. Seeds and cotyledons of C. cathartica are larger and possessing higher hydration and swelling capacity than that of C. maritima indicating higher permeability and softness. The crude protein of C. maritima and C. cathartica were found to be higher than common pulses. The pH vs. protein solubility profile was almost similar with minimum solubility at pH 4 (27.8–28.1%). C. maritima showed higher oil absorption capacity (1.53 ml/g) as well as water absorption (0.1 M) capacity. The gelation capacity was minimal at 0.1 M NaCl and pH 4 for both the seed flours. Addition of carbohydrates (starch, lactose, maltose and sucrose) reduced the lowest gelling capacity of C. maritima except for maltose in C. cathartica. Emulsifying activity (EA) and emulsifying stability (ES) diminished with increasing concentration of flours. Minimum EA and ES were attained at pH 4 and maximum at pH 10 in both seed flours. Maximum EA for C. cathartica and C. maritima (62% vs. 72.6%) was attained at 0.4 M NaCl. The ES vs. flour concentration, pH and ionic strength profiles did not differ much between C. maritima and C. cathartica. Peak foam capacity (FC) and stability (FS) were achieved at 6% (w/v) of C. maritima flour, while the same was attained at 8% (w/v) of C. cathartica. The FC and FS of the seed flours improved with increasing pH (pH 2–10). C. maritima flour exhibited the better FC (27.7%), while C. cathartica exhibited better FS (44.42%) at pH 10. Although highest FC was attained at 0.4 M NaCl in both flours, C. maritima was found to be superior (30.5% vs. 28.5%). The flour of C. maritima attained the highest FS at 0.2 M NaCl than C. cathartica (0.4 M NaCl). The minimum cooking time for cotyledons of C. cathartica was more and higher gruel solid loss was reported due to its high L/B ratio. The Pearson correlation coefficients revealed that functional properties of seed flours vary due to their chemical composition.     

离子强度对猪肉肌原纤维蛋白乳化特性和理化特性的影响

以猪肉肌原纤维蛋白为研究对象,测定不同离子强度下肌原纤维蛋白的乳化特性,包括乳化能力（emulsifying capacity,EC）、乳化稳定性（emulsifying stability,ES）,同时测定不同离子强度下肌原纤维蛋白的溶解性、分子间氢键、表面疏水性、活性巯基和总巯基等理化特性,并对理化特性、乳化特性指标进行了相关性分析。结果表明：随着介质离子强度的提高,肌原纤维蛋白的EC和ES增强,溶解度增大,分子间氢键、活性巯基呈上升趋势,表面疏水性则呈下降趋势,而总巯基则无明显变化;溶解度与EC显著正相关（P＜0.05）,与ES呈极显著正相关（P＜0.01）,活性巯基和氢键都与EC呈极显著正相关（P＜0.01）,而表面疏水性与EC呈极显著负相关（P＜0.01）,与ES显著负相关（P＜0.05）。结论：改变肌原纤维蛋白介质的离子强度,导致肌原纤维蛋白的乳化特性、理化特性产生变化,肌原纤维蛋白的理化特性和乳化特性之间有显著或极显著的相关性。     

Effect of succinylation on the functional and physicochemical properties of alpha-globulin,the major protein fraction from Sesamum indicum L

alpha-Globulin the major protein fraction from Sesamum indicum was succinylated to different levels and the effect of the chemical modification was evaluated both on the functional and physicochemical properties. The results suggest that the pH of minimum solubility shifted to the more acidic side (pH approximately 4.5-5.5) for the succinylated alpha-globulin whereas for control alpha-globulin the pH of minimum solubility was 6.5. Succinylation also increased emulsion activity and emulsion stability of the protein. The emulsion stability increased from a control value of 53 +/- 3 s to a value of 122 +/- 5 s. Bulk density, water absorption capacity, oil absorption capacity, foam capacity and foam stability were evaluated in phosphate buffer (pH 7.0) containing 0.5 M sodium chloride and all these properties showed increased values as a result of succinylation. Ultracentrifugation studies showed that the % composition of 7S component increases with concomitant decrease in that of 11S fraction with the increase in percentage of succinylation. Further increase in succinylation resulted in only 2S component which is a dissociated form of 11S and/or 7S protein fractions. The fluorescence emission studies showed a decrease in the fluorescence emission intensity of alpha-globulin as a result of succinylation. The thermal stability of the protein molecule decreased due to progressive succinylation as indicated by decrease in the apparent thermal denaturation temperature from a control value of 84 to 62 degrees C at a succinylation level of 40%. These results suggest that succinylation improves the functional characteristics of alpha-globulin. Such changes in the functional properties have been attributed partly to the dissociation of the protein molecule at higher levels of succinylation and the increase in the net negative charge on the protein.     

Effect of succinylation on the functional and physicochemical properties of α‐globulin,the major protein fraction from Sesamum indicum L.

α‐Globulin the major protein fraction fromSesamum indicum was succinylated to different levels and the effect of the chemical modification was evaluated both on the functional and physicochemical properties. The results suggest that the pH of minimum solubility shifted to the more acidic side (pH ˜ 4.5–5.5) for the succinylated α‐globulin whereas for control α‐globulin the pH of minimum solubility was 6.5. Succinylation also increased emulsion activity and emulsion stability of the protein. The emulsion stability increased from a control value of 53 ± 3 s to a value of 122 ± 5 s. Bulk density, water absorption capacity, oil absorption capacity, foam capacity and foam stability were evaluated in phosphate buffer (pH 7.0) containing 0.5 M sodium chloride and all these properties showed increased values as a result of succinylation. Ultracentrifugation studies showed that the % composition of 7S component increases with concomitant decrease in that of 11S fraction with the increase in percentage of succinylation. Further increase in succinylation resulted in only 2S component which is a dissociated form of 11S and/or 7S protein fractions. The fluorescence emission studies showed a decrease in the fluorescence emission intensity of α‐globulin as a result of succinylation. The thermal stability of the protein molecule decreased due to progressive succinylation as indicated by decrease in the apparent thermal denaturation temperature from a control value of 84 to 62°C at a succinylation level of 40%. These results suggest that succinylation improves the functional characteristics of α‐globulin. Such changes in the functional properties have been attributed partly to the dissociation of the protein molecule at higher levels of succinylation and the increase in the net negative charge on the protein.     

Some functional properties of lupin proteins modified by lactic fermentation and extrusion

The aim of this work was to determine modifying effects of lactic fermentation and extrusion processes on functionality of lupin proteins. Protein content, surface hydrophobicity, water absorption capacity (WAC), water solubility index (WSI) and emulsifying properties (EAI, ESI) of protein preparations obtained from lupin seeds (Lupinus luteus, Lupinus albus, Lupinus angustifolius), with various contents of hull, were analyzed. Changes of protein properties were affected by lupin cultivar, hull content and applied processing method. An increase of soluble protein content after controlled lactic fermentation of lupin seeds, and changes of surface protein hydrophobicity, WAC and WSI values after each treatment and significant worsening of protein emulsifying properties were observed. Correlations were found between parameters examined in this study.     

猕猴桃糖蛋白及其去糖链蛋白功能特性的研究

本文研究了25~60 ℃范围内温度对猕猴桃糖蛋白(CGP)及其去糖链蛋白(GPP)吸油性、溶解性、起泡性和乳化性的影响,以及CGP、GPP的浓度及其溶液pH3~7.5和0~5 g/100 mL范围的NaCl离子强度对CGP和GPP溶解性、起泡性和乳化性的影响。结果表明:25~60 ℃温度范围内CGP吸油性、溶解度高于GPP,随温度升高,CGP、GPP溶解度下降,两者的起泡性先降低后升高,CGP乳化性先降低后升高,GPP乳化性先升高后降低;不同pH条件下,CGP的溶解度始终高于GPP,pH3~6范围内CGP、GPP溶解度均先下降后升高,pH3~7.5范围内CGP、GPP起泡性和乳化性先下降后升高;随离子强度的升高,CGP、GPP溶解度均下降,且CGP的溶解度始终高于GPP,CGP的起泡性和乳化性下降,GPP起泡性先下降后升高而乳化性则相反;CGP、GPP起泡性和乳化性均随其浓度的增高而增高,1.0 mg/mL时起泡性和乳化性最高,0.2 mg/mL时最低。     

Solubility, Hydrophobicity and Net Charge of Succinylated Canola Protein Isolate

Effects of succinylation (54% and 84% modification of free amino groups), pH (3.5–11.0) and NaCl concentration (0.0–0.7M) on solubility, hydrophobicity and zeta potential (net charge) of canola protein isolate were examined. Succinylation markedly enhanced protein solubility at alkaline and slightly acidic pH while effect of NaCl depended on pH. Surface hydrophobicity (S₀) decreased as level of succinylation increased. Effect of NaCl varied with pH but in general, S₀ decreased in a curvilinear manner as pH increased. Zeta potential became more electronegative as both succinylation and pH increased, but decreased with addition of NaCl. Hydrophobicity and zeta potential were closely related in a nonlinear inverse manner demonstrating that ionic environment had opposing influences on number of hydrophobic and charged groups on the surface of protein molecules in solution.     

Xanthan Gum Effects on Solubility and Emulsification Properties of Soy Protein Isolate

The effect of xanthan gum (XG) on solubility and emulsifying properties of soy protein isolate (SPI) was evaluated. The solubility of SPI was increased by addition of XG (p < 0.05). The emulsifying activity of SPI-XG was 4 times higher than that of SPI or XG alone (p < 0.05) and similar to that of bovine serum albumin (BSA) (P > 0.05). The emulsifying stability of SPI-XG dispersions was respectively 3 and 2 times higher than that of SPI and BSA (p < 0.05). The solubility and emulsifying properties of SPI-XG dispersions were stable over a wide range of pH (3.0 to 9.0), ionic strength (0.1 to 1.0M NaCl), and heat (85°C, 1 hr).     

Effect of ionic strength and/or pH on Extractability and physico-functional characterization of broad bean (Vicia faba L.) Protein concentrate

Protein extractability studies showed that the protein of broad bean (Vicia faba L.) was extractable at both acidic and basic pH. The percentage of pH-12 extractable protein that was precipitated at pH 4 (isoelectric point) from protein concentrate, dehulled full-fat seed flour and whole seed flour are 62.0%, 61.2% and 71.6%, respectively. Low ionic strength (μ0.4) increased the solubility of the protein in the bean concentrate at acidic pH, while at alkaline pH, increase in ionic strength (0.1–2.0) had an inverse relationship on the concentrate protein solubility. The capacity to form protein-stabilized foam was least (34%) at pH 4 and highest (97%) at pH 12. These were increased to 62% (pH 4) and 139% (pH 12) in medium with ionic strengths of 0.2 and 0.4, respectively. The foam formed was more stable at pH 4 than at the other pHs. Low ionic strength of 0.1 improved water absorption capacity but reduced it at ionic strength of 0.6.     

Molecular Structure and Functionalities of Protein Isolates Prepared from Defatted Cottonseed Flour Succinylated at Various Levels

Protein isolates were prepared from glandless cottonseed flour succinylated at various levels. Succinylation levels of the resultant proteins followed first order kinetics with respect to succinic anhydride concentration added. Succinylation decreased the amount of free sulfhydryl, as well as ξ-amino groups of proteins, but did not change intermolecular disulfide bonds. Protein isolate prepared from highly succinylated flour consisted of one homogeneous protein agglomerate, while isolate from unmodified flour contained several heterogeneous proteins. Water solubility of the isolates increased logarithmically with respect to degree of succinylation, with the sharpest increase at 95% succinylation or higher. Heat coagulability had an inverse-linear relationship with amounts of negative charges on protein molecules. Emulsion capacity and oil absorption capacity were not significantly changed at less than 60% succinylation. However, these increased markedly at greater than 60% succinylation. Emulsion capacity had a positive, but not linear correlation with water solubility of proteins.     

Emulsifying Properties of Food Proteins: Bovine Serum Albumin

Emulsifying activity (EA) of bovine serum albumin (BSA), at concentrations of 0.07 to 0.45 mM, was maximum at oil:water ratios (o:w) <2:8, in the pH range 4 to 8. At pH 8, the EA was greater than that at pH values below, i.e., < pH 7, but the energy required to form emulsions was higher., EA and emulsion stability (ES) were directly related and improved in NaCl; ES was maximum at pH 4. Surface load was directly related to the o:w and the increase in viscosity with protein load apparently reflected protein unfolding that was marked at an energy input of 680 10⁶ J m^-3. Data indicate that some native structure and flexibility of the BSA molecule are required for optimum emulsifying properties.     

Effects of succinylation and deamidation on functional properties of oat protein isolate

The effects of two different modification methods (deamidation and succinylation) on the functional properties (solubility, water- and oil-binding capacity, foaming capacity and stability, emulsion activity and stability) of oat protein isolates were evaluated. Protein isolates extracted from defatted oat flour at alkaline pH were acylated by 0.20 g/g of succinic anhydride. The protein isolate was also modified using a mild acidic treatment (HCl, 0.5 N). Succinylation and deamidation improved solubility and emulsifying activity of the native protein isolate. Foaming capacity of oat protein isolate increased after deamidation, whereas succinylation decreased it. The deamidated and succinylated proteins had lower foam and emulsion stabilities than had their native counterpart. Water- and oil-binding capacity, in both modified oat proteins, was higher than those of the native oat protein isolate.