Solubility and functional properties of sesame seed proteins as influenced by pH and/or salt concentration

The protein content, solubility and functional properties of a total protein isolate prepared from sesame seeds (Kenana 1 cultivar) as a function of pH and/or NaCl concentration were investigated. The protein content of the seed was found to be 47.70%. The minimum protein solubility was at pH 5 and the maximum was at pH 3. The emulsifying capacity, activity and emulsion stability as well as foaming capacity and foam stability were greatly affected by pH levels and salt concentrations. Lower values were observed at acidic pH and high salt concentration. The protein isolate was highly viscous and dispersable at pH 9 with water holding capacity of 2.10 ml H₂O/g protein, oil holding capacity of 1.50 ml oil/g protein and bulk density of 0.71 gm/ml.     

苦杏仁蛋白的功能特性

采用稀盐溶液浸提及等电点盐析相结合的方法提取制备苦杏仁蛋白,研究pH值、NaCl浓度、蛋白质量浓度和温度等因素对苦杏仁蛋白功能特性(溶解性、持水性、吸油性、乳化性及乳化稳定性、起泡性及起泡稳定性)的影响。结果表明：在等电点pI附近时,苦杏仁蛋白的溶解性、持水性、乳化性及乳化稳定性、起泡性最差;在较低NaCl浓度范围内(0～0.8mol/L)提高NaCl浓度可促进蛋白溶解性、乳化性及乳化稳定性、起泡性及起泡稳定性的提高,而较高的NaCl浓度对蛋白功能特性提高具有抑制作用;当蛋白质量浓度达到一定水平时(3～4g/100mL),蛋白功能特性(乳化性及乳化稳定性、起泡性及起泡稳定性)提高趋于平缓;在适宜的温度范围内,提高温度可有效提高苦杏仁蛋白各项功能特性,但当温度继续上升,各项功能特性持续降低。     

Solubility, Emulsifying, and Foaming Properties of Rice Bran Protein Concentrates

Rice bran protein concentrates were prepared from full-fat and defatted raw rice bran. Selected functional properties, viz. nitrogen solubility, emulsification properties, and foaming properties were measured over the pH range 2.0 to 10.5 and in three dispersion media including water, 0.1M NaCl (low salt) and 1.0M NaCl (high salt). Below and above the isoelectric pH (4.5) the nitrogen solubility increased. Higher pH enhanced the nitrogen solubility and, thereby, considerably improved the functional properties. In higher salt concentration, nitrogen solubility was reduced which also altered the properties of emulsification and foaming. Multiple regression analysis showed that pH was the primary determinant of nitrogen solubility, emulsification and foaming properties. Multiple regression models including pH, salt concentration and nitrogen solubility as independent variables were found to be more accurate in predicting other functional properties.     

蒸汽爆破制备小麦麸皮可溶性膳食纤维

以小麦麸皮为试验原料,研究了蒸汽爆破(SE)制备可溶性膳食纤维(SDF)工艺参数(蒸汽爆破压力和保压时间),并探讨了改性前后SDF的功能特性。结果表明:最佳工艺参数为压力为0.6 MPa,保压时间为9 min,SDF提取率达到31.56%。对照-SDF和SE-SDF的溶解性分别为85.47%和95.68%,持水力分别为2.35和3.57 g/g,持油力分别为1.25和2.06 g/g,膨胀力分别为3.24和5.69 mL/g,乳化活性分别为45.78和79.67 mL/100 mL,乳化稳定性分别为40.17和61.02m L/100 mL,最小凝胶浓度分别为13.57%和8.65%;总酚含量分别为1.57和3.26 mg GAE/g,ABTS、·OH、O2^-·和DPPH的清除率分别为59.34%和70.21%,30.25%和40.12%,45.18%和50.21%,80.42%和88.36%。研究结果可为小麦麸皮膳食纤维的功能改性及综合利用提供理论依据。     

兔皮胶原蛋白的加工特性

以兔皮胶原蛋白为原料,对其加工特性进行系统研究。结果表明,兔皮胶原蛋白具有较强的吸水性,达到14.89 m L/g;其在酸性环境中有很高的溶解性,在p H值为3时,溶解度最高,在碱性环境中溶解度降至50%左右;离子质量浓度对胶原蛋白的溶解度有明显影响,其在Na Cl质量浓度为0~2 g/100 m L时保持相对稳定,在Na Cl质量浓度由2 g/100 m L增加至4 g/100 m L过程中急剧下降,而Na Cl质量浓度大于4 g/100 m L后,胶原蛋白溶解度变化不再明显;当胶原蛋白的质量浓度小于1 g/100 m L时,兔皮胶原蛋白的乳化性随着胶原蛋白质量浓度的增加逐渐增加,但质量浓度超过1 g/100 m L时,乳化性降低,乳化稳定性随胶原蛋白质量浓度的变化呈现与乳化性相反的趋势;低质量浓度的胶原蛋白溶液在p H 3~6过程中,乳化性和乳化稳定性均呈下降趋势,随后,p H 6~9时乳化性和乳化稳定性缓慢增加后保持稳定;离子质量浓度在0.00~7.02 g/100 m L范围内,随离子质量浓度的增加,乳化性呈现出先升高后降低的趋势,而乳化稳定性则呈现先增加随后保持稳定的趋势,在离子质量浓度为5.85 g/100 m L时,胶原蛋白的乳化性与乳化稳定性较好。     

Functional Properties of Raw and Heat Processed Cowpea (Vigna unguiculata, Walp) Flour

The functional properties, gelation, water and oil absorption, emulsification, foaming and protein solubility of raw and heat processed cowpea flour were determined. The effects of pH and NaCl concentration on some of these functional properties were also investigated. Protein solubility vs pH profile showed minimal solubility at pH 4. Water and oil absorption capacities of raw flour were 2.4 g/g and 2.9 g/g, respectively, while heat processed flour gave 3.6 g/g and 3.2 g/g, respectively. Addition of NaCl up to 0.4% improved the emulsification capacity of raw flour while a decrease was observed in the heat processed flour after 0.2%. Least gelation concentration of raw flour was found to be 16% and heat processed flour, 18%.     

米糠蛋白酶解产物功能特性及乳液稳定性研究

目的 改善米糠蛋白的溶解性,探讨米糠蛋白乳液的稳定性。方法 选用胰蛋白酶对米糠蛋白进行酶法改性,分析其在不同水解度下(1%、3%、7%)酶解产物的功能特性及不同pH、离子强度和温度对米糠蛋白酶解产物乳液的影响。结果 酶解可显著提高米糠蛋白的溶解性,在水解度7%时的溶解性最高;而酶解产物的起泡性、起泡稳定性、乳化性和乳化稳定性呈现先增加后下降的趋势,并在水解度为3%时达到最大值;经酶解后持油性显著增加(P<0.05),而持水性显著降低(P<0.05)。米糠蛋白及酶解产物乳液在不同pH下平均粒径和电位总体上呈现相似变化趋势,在等电点附近极不稳定,在pH 7～8时乳液趋于稳定;低水解度(1%、3%)的酶解产物乳液对高温和盐离子的抵抗能力高于米糠蛋白。结论 水解度为3%的酶解产物,其功能特性显著提升,制备的乳液在高离子强度和加热条件下较为稳定,该结果为米糠蛋白酶解产物制备食品乳液提供理论依据。     

Isolation and characterization of protein isolated from defatted cashew nut shell: Influence of pH and NaCl on solubility and functional properties

This work reports the isolation of protein from defatted cashew nut shell (CNS), with the crude protein product containing 91.07% protein. Under its natural conditions, the solubility of this protein isolate is comparable (74.02%) to that of mustard green meal protein. The solubility of the protein isolate decreases with decreasing pH, with the minimum solubility observed at its isoelectric point (pH 3). The water holding capacity, oil holding capacity, foaming capacity, foam stability, emulsifying capacity and emulsion stability were found to be 2.56 cm³ H₂O/g protein, 4.28 cm³ oil/g protein, 76.88%, 70.98%, 62.0% and 79.0%, respectively. The profiles of these functional properties were determined with varying pH values and NaCl concentrations, and improved properties were observed in the alkaline pH range and in the presence of NaCl. Electrophoretic analysis showed that the high molecular weight protein globulin was the major protein in the protein isolate.     

桑叶蛋白的功能特性研究

采用超声波辅助提取结合盐酸沉析法提取桑叶蛋白,研究pH值、离子强度、蔗糖质量浓度和温度对桑叶蛋白功能特性的影响。结果表明：远离其等电点时,桑叶蛋白具有良好的持水性、溶解度、乳化性及乳化稳定性、起泡性;桑叶蛋白的持水性、溶解度和起泡性与NaCl浓度(0～1.0mol/L)呈正相关,而过高的离子强度(NaCl浓度高于0.6～0.8mol/L)会使桑叶蛋白的乳化性和乳化稳定性下降;蔗糖的加入会增加桑叶蛋白的持水性,但会降低其溶解度和起泡性,对桑叶蛋白的乳化性和乳化稳定性影响不大;桑叶蛋白的吸油性和起泡性与温度(4～80℃)呈正相关,持水性、溶解度、乳化性及乳化稳定性于60℃时最好。     

米糠蛋白酶法改性前后的功能特性变化研究

以蛋白质为配料的产品中,蛋白质功能性质往往比营养价值更重要,直接影响到米糠蛋白的应用前景。实验研究了经碱性蛋白酶改性后的米糠蛋白功能特性,并与其改性前进行了比较。测定了改性前后米糠蛋白的溶解性、乳化性及乳化稳定性、起泡性及泡沫稳定性,并确定浓度、温度等因素对上述指标的影响。实验结果表明,改性后米糠蛋白的溶解性、起泡性及乳化性与改性前相比均有较大改善,分别提高了140.46%、117.38%、100.50%。米糠蛋白溶解性在pH4.0～6.0较低,在碱性条件下较高,随温度升高而增大;米糠蛋白乳化性、起泡性在碱性条件下较高,随温度的升高其起泡能力和乳化能力均增强。      

安卡红曲霉液态发酵豆渣、麦麸、梨渣制备可溶性膳食纤维

以豆渣、麦麸、梨渣为原料,接种安卡红曲霉进行液态发酵,研究可溶性膳食纤维(SDF)的制备工艺及特性。结果表明,可溶性膳食纤维的最优发酵条件为豆渣发酵时间7d、料液比1∶15 (g/mL)、接种量13%;麦麸发酵时间6d、料液比1∶15 (g/mL)、接种量14%;梨渣发酵时间6d、料液比1∶20 (g/mL)、接种量14%。发酵后SDF的溶解度、持水力及持油力均得到提高,功能特性得到改善。     

Functionality of native and denatured cashew nut kernel protein isolates at isoelectric pH as a function of salt concentration

The reduced solubility of proteins near the isoelectric pH limits their use in food formulations whose pH lies in the range 5.0–6.0 because of poor functionality. In the present study, the effect of salt on the functionality of native and denatured cashew nut kernel protein isolates at the isoelectric pH was investigated. Both isolates showed improvement in their functional properties, but the improvement was greater for the denatured protein isolate. The solubilities of denatured and native protein isolates at the isoelectric pH increased from 26.4 g l^?1 and 64 g l^?1, respectively, without salt to maxima of 363 and 308 g l^?1, respectively, at 0.75 M salt concentration. The water binding capacity of the isolates increased with increase in NaCl concentration from 1.70 ml g^?1 to 1.77, 1.82, 1.92 and 2.2 ml g^?1 for denatured protein isolate and from 1.45 ml g^?1 to 1.65, 1.69, 1.82 and 1.97 ml g^?1 for native protein isolate at 0.25, 0.50, 0.75 and 1.0 M salt concentrations, respectively. When the properties of the isolates in 0.75 M NaCl solutions were compared with those in salt‐free water there were 15% and 116% increases in emulsifying capacity, 40‐fold and 45‐fold increases in emulsifying activity and 4.6‐fold and 40‐fold increases in emulsion stability for native and denatured protein isolates, respectively, whilst the corresponding foaming capacities increased from 4 to 5.5 and 0 to 8.9 ml g^?1 protein. Statistically, no difference in the foaming capacity of either of the isolates was observed above 0.5 M NaCl. The foam stability also exhibited similar behaviour. Copyright © 2004 Society of Chemical Industry     

胡麻籽分离蛋白的溶解性与起泡性研究

为促进胡麻籽分离蛋白在食品工业中的应用,研究了pH值、盐浓度、蛋白质浓度等因素对其水溶性、起泡性和泡沫稳定性的影响。pH值对胡麻籽分离蛋白溶解度的影响呈典型的V形曲线。NaCl浓度为0.4mol/L前后胡麻籽分离蛋白表现出明显的盐溶与盐析效应。在0.1%～0.8%范围内,提高蛋白质浓度能增强起泡性与泡沫稳定性。在等电点附近,胡麻籽分离蛋白的起泡性最差但却具有最强的泡沫稳定性。NaCl对胡麻籽分离蛋白的起泡性的影响与其对溶解性的影响有相同的趋势。蔗糖能提高胡麻籽分离蛋白的泡沫稳定性,但当浓度高于5%时,对起泡性有负面影响。     

水溶性蚕蛹蛋白功能特性探究

以鲜蚕蛹为原料,采用等电点沉淀法提取水溶性蛋白,并对其功能性质进行研究。结果表明,蚕蛹水溶性蛋白是一种优质蛋白,必需氨基酸含量占总氨基酸含量的39%。蛋白溶解度在70℃条件下降低程度较小,在pH 4.0～9.0,溶解度因α-螺旋与β-折叠增加呈上升趋势,pH值> 9.0后,β-转角和无规则卷曲含量增加,但蛋白展开程度较小且蛋白之间斥力的增加,溶解度仍随pH的增加而继续增大,在NaCl浓度为0.2～1.0 mol/L时,溶解度随着NaCl浓度增加呈上升趋势,> 1.0 mol/L后因盐析作用溶解度下降。蛋白乳化性能在油相体积分数35%、蛋白质量浓度1.0 g/L、pH 10.0下较好,蛋白起泡性在蛋白质量浓度3.0 g/L下最高,蛋白泡沫稳定性在蛋白质量浓度1.0 g/L下最高,蛋白持油性最大为3.9 g/g。该实验结果为蚕蛹水溶性蛋白的综合利用提供理论依据。     

Chemical Modification and Functional Properties of Acylated Beef Heart Myofibrillar Proteins

Beef heart myofibrils were acylated with 0.1, 0.3, 0.6, 0.8, 1.0, 1.5, 2.0, 3.0, and 5.0 mmoles anhydride/g protein, at pH 8.0–8.5 and 2–3°C, with acetic anhydride (AA), succinic anhydride (SA), cis,cis,cis,cis-tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride (FA), and 1,2,4-benzenetricarboxylic anhydride (BA). The anhydride reacted with e-amino groups of lysine, sulfhydryl groups, and hydroxyl groups of tyrosine, serine, and threonine. Chemically modified beef heart myofibriliar proteins were superior to native heart myofibriliar proteins in solubility, emulsifying capacity, emulsion activity, and emulsion stability in a low salt solution of 0.1M NaCl, 0.05M potassium phosphate at pH 7.4 and 6.0. Protein modified with 0.5 mmole anhydride/g protein in 0.2M NaCl had a solubility greater than unmodified proteins in 0.6M NaCl at pH 7.4. Chemical modification also altered the pH-solubility profile. The chemically modified beef heart myofibrillar proteins exhibited an emulsifying capacity at pH 6.0 and 7.4 that was greater than that of the native proteins at pH 7.4. The recommended extent of acylation for modifying beef heart myofibrils on a gram protein basis is 0.6 mmole AA, 1.5 moles SA, 0.6 mmole FA, and 0.6 mmole BA.     

Functional properties of proteins isolated from phorbol ester-free physic nut (Jatropha curcas L.) seed cake

Phorbol ester-free physic nut (Jatropha curcas L.) seed cake is a nutritious protein source. Functional properties of the protein isolates obtained from various protein precipitation methods were investigated. Proteins isolated from the seed cake by ammonium sulfate gave the highest yield. The solubility of all proteins increased with increasing pH with their maximum and minimum solubility at pH of 12.0 and 4.0, respectively. The protein prepared by ethanol provided the maximum water holding capacity (3.34 mL water/g protein). The oil binding capacities of all proteins were 1.96–2.03 mL oil/g protein. The protein precipitated by ethanol showed higher emulsion activity and stability than that precipitated by acetone and ammonium sulfate. The protein obtained from ammonium sulfate gave the highest foam capacity, while the protein from acetone had the highest foam stability. Different functional properties of the proteins were achieved by various protein precipitation methods. The protein isolate obtained from each method could serve as a food ingredient applied to food products requiring a specific functional property.     

超声波对花生蛋白功能特性的影响

用超声波处理花生蛋白粉溶液,测定不同条件下花生蛋白的功能特性。结果表明,超声波处理20min,起泡性从30%增大到60%,泡沫稳定性从17%增大到50%;超声波处理15min,乳化性从38.9%增加到49.3%;超声波处理6min,吸油性从0.91mL/g增大到1.51mL/g;超声波处理8min使1g/100mL花生蛋白溶液中花生蛋白溶解性从0.10g增大到0.35g,2g/100mL花生蛋白溶液中花生蛋白溶解性从0.23g增大到0.48g;pH大于4时,超声波使花生蛋白乳化性增强;NaCl浓度为0.2~0.4mol/L时,超声波使花生蛋白乳化性增强。      

Physicochemical and functional properties of full‐fat and defatted Moringa oleifera kernel flour

Full‐fat and defatted Moringa oleifera kernel flours were analysed for their functional properties. The effect of pH and NaCl concentrations on the functional properties of the flours was investigated following standard procedures. The protein content of full‐fat and defatted flour was 36.18 and 62.76 g/100 g, respectively. The concentrations of other proximate constituents of the defatted flour were higher than those of the full‐fat flour. Nitrogen solubility was lowest at pH of 4.0 and 9.0, respectively, with maximum solubility occurring at pH of 6.0. Defatting increased the water absorption and fat absorption capacities of Moringa oleifera kernel flour. The foaming capacity and foam stability of the defatted flour were 86.0% and 82.0 mL, whereas that of full‐fat flour were 20.6% and 18.5 mL respectively. The defatted flour showed better emulsification (97.2 mL g^?1) than full‐fat flour (66.0 mL g^?1). The least gelation concentration of the defatted and full‐fat flours was 14% and 16% (w/v) respectively. Moringa oleifera kernel flour can be a valuable source of vegetable protein in fortified food products formulation.     

Chemical and functional characterization of Gum karaya (Sterculia urens L.) seed meal

Chemical and functional characterization of the meal of Gum karaya (Sterculia urens) whole and dehulled–defatted seed were investigated. Dehulled–defatted seed meal (DDSM) contained 40.7% of protein as compared to 20.4% in the whole seed meal (WSM). Essential minerals of Ca 39.5, Fe 4.4, K 9.6 and P 995 mg/100 g were found in DDSM. A solid to solvent ratio 1:40 and extraction time of 60 min was optimum. The highest protein solubility (93.97%) was observed at pH 12 and the lowest (26.41%) protein solubility at pH 6. The solubility of protein was enhanced in the presence of 0.1 M and 0.5 M NaCl between pH rang of 2–12. The protein precipitation from an alkaline extract of pH 10 was maximum (81%) at pH 6. Polyacrylamide gel electrophoresis shows that 14 bands of SDS soluble protein subunits were observed in WSM and DDSM. A higher buffer capacity of the meal was observed in the acid medium than in alkaline medium. The DDSM had an initial moisture content (IMC) of 5.16%, which equilibrated at 32% RH and moisture content increased sharply at higher humidity (70%) which, indicated that the non-hygroscopic in nature. Water holding capacity and oil holding capacity were 111 and 81, 67 and 114 g/100 g of WSM and DDSM respectively. DDSM showed very good foam capacity (32%) and stability (75%) even after 90 min at room temperature. The emulsification capacity of DDSM was found to be 20 mL/g sample.     

麦麸及麦麸膳食纤维常规粉碎和超微粉碎物化特性比较

为明确普通粉碎和超微粉碎对麦麸和麦麸膳食纤维物化特性影响,对处理后的麦麸和麦麸膳食纤维持水性、持油性、吸水膨胀性、黏度、阳离子交换能力及对油脂、胆固醇、胆酸钠和葡萄糖吸附能力进行了测定。结果表明:麦麸膳食纤维比麦麸具有更高的WHC和OHC,而超微粉碎处理可进一步提升麦麸膳食纤维WHC和OHC,分别为4.99 g/g和6.30 g/g;在胆酸钠浓度为3 mg/mL时,超微粉碎麦麸及麦麸膳食纤维胆酸钠吸附量最高,分别为40.58 mg/g和46.08 mg/g;在葡萄糖浓度为50～100 mmol/L范围内,超微粉碎后麦麸及麦麸膳食纤维葡萄糖吸附量亦明显上升。pH7时,普通粉碎处理后麦麸胆固醇吸附能力低于麦麸膳食纤维,而超微粉碎处理后麦麸胆固醇吸附能力高于麦麸膳食纤维。普通粉碎的麦麸对不饱和脂肪酸和饱和脂肪酸吸附量最高,分别达到1.56 g/g和1.13g/g。研究表明麦麸及麦麸膳食纤维表通过处理后现出不同物化特性,这将为麦麸食品化利用及对食品体系物化特性影响提供理论依据。