琥珀酰化提高大豆分离蛋白乳化性的研究

为了提高大豆分离蛋白(SPI)的乳化性,采用琥珀酸酐对大豆分离蛋白进行酰化改性。系统研究了SPI质量分数、琥珀酸酐用量和反应温度对大豆分离蛋白乳化性的影响,建立以上3因素与乳化活性和乳化稳定性关系的数学模型,并利用响应面法优化出大豆分离蛋白琥珀酰化的适宜条件:SPI质量分数6.5%、反应温度49℃、琥珀酸酐添加量11.5%。该条件下制备的琥珀酰化蛋白的乳化活性和乳化稳定性与未改性的大豆分离蛋白相比较,分别提高了2.98倍和4.86倍。     

超声-琥珀酰化复合改性提高大豆分离蛋白乳化性的研究

为提高大豆分离蛋白的乳化性,采用超声和琥珀酰化两种方法对大豆分离蛋白进行复合改性。通过单因素实验研究底物浓度、超声功率、超声时间、琥珀酸酐添加量和酰化反应温度对大豆分离蛋白乳化性的影响。在单因素实验的基础上,运用响应面法优化出超声-琥珀酰化改性大豆分离蛋白的适宜条件:超声功率569.36W、超声时间9.79min、酰化温度49.72℃。该条件下制得的改性大豆分离蛋白的乳化活性和乳化稳定性与未改性的大豆分离蛋白相比较,分别提高了3.05倍和4.65倍。     

酰化对大豆分离蛋白乳化性能的影响

目的:研究化学改性对大豆分离蛋白(SPI)乳化性能的影响;方法:采用乙酸酐和琥珀酸酐对SPI进行化学改性;结果:随酰化试剂用量的增大,酰化程度不断提高,在相同酰化试剂用量的条件下,乙酰化程度高于琥珀酰化.SPI的乳化活性指数(EAI)和乳化稳定性(ES)都随酰化程度的增大而增大.在中性和弱碱性(pH 5.0～9.0)范围内,酰化明显提高了SPI的EAI和ES.琥珀酰化的改性效果优于乙酰化;不过离子强度削弱了SPI的EAI和Es;结论:酰化可有效提高SPI的乳化性能,其中琥珀酰化的改性效果优于乙酰化.     

琥珀酰化改性对米糠蛋白功能性质的影响

为了改变米糠蛋白的功能性质,扩大米糠蛋白在食品工业的应用范围,利用琥珀酸酐对米糠蛋白进行酰化改性处理。通过单因素反应,确定了琥珀酸酐酰化改性米糠蛋白的最适反应条件为:米糠蛋白浓度为10%,反应温度为35℃,琥珀酸酐/蛋白质用量为15%。在最适反应条件下,分别反应40 min、80 min,制得酰化度分别为46.8%、69.2%的琥珀酰化米糠蛋白。评价了上述两种琥珀酰化米糠蛋白制品的溶解性、乳化性、起泡性等功能性质,结果表明,琥珀酰化改性对米糠蛋白的溶解性、乳化稳定性以及起泡性均有一定改善,而酰化米糠蛋白的乳化活性、泡沫稳定性随着酰化程度的提高有所下降。     

琥珀酰化度大小对改性小麦面筋蛋白性质影响的研究

本文采用琥珀酸酐对小麦面筋蛋白进行酰化改性，讨论了琥珀酰化度大小对面筋蛋白的溶解性、乳化性、乳化稳定性、起泡性和起泡稳定性影响，并对最佳改性条件下改性小麦面筋蛋白进行了在面条加工中的应用研究。结果表明：琥珀酰化度为66．1％时改性效果最好，改性面筋蛋白的溶解度、乳化及乳化稳定性、起泡及起泡稳定性分别为5．09mg／ml，56．8％，56．4％，44．8％，25％；利用最佳改性条件下的琥珀酰化面筋蛋白生产面条，面条的综合性能均比未改性的面筋蛋白品质高。     

琥珀酰化改性对米渣分离蛋白乳化性的影响

研究对米渣分离蛋白进行琥珀酰化改性以提高其功能特性,拓展其在食品中的应用范围。在单因素试验的基础上,通过响应面法优化琥珀酰化米渣分离蛋白的改性条件,得到乳化性较好的产物。结果表明:琥珀酸酐添加量、反应温度、pH对酰化反应均有显著影响。琥珀酰化改性的最佳条件为反应温度36.24℃,反应pH 8.57及琥珀酸酐添加量5.39%,在此条件下,琥珀酰化米渣分离蛋白的乳化性为5 551 m2/g,为未酰化米渣分离蛋白乳化性的2.64倍。采用响应面法优化琥珀酰化米渣分离蛋白乳化性的工艺条件可靠,具有实用价值。     

酰化改性对大豆分离蛋白凝胶pH响应性的影响

为探讨琥珀酰化改性对大豆分离蛋白(SPI)pH响应性的影响,在特定pH条件下大豆分离蛋白与琥珀酸酐发生酰化反应。通过单因素得出最优条件:酸酐蛋白比0.15、pH 9.0、反应时间30 min,此时酰化程度最高。优化的响应面试验结果表明:酸酐蛋白比16.97%、时间28.11 min、pH 9.32。以葡萄酸内酯(GDL)作交联剂,将改性的大豆分离蛋白制成凝胶;以溶胀性和pH响应性为指标,测定酸酐添加量和GDL添加量对其凝胶性的影响。结论:当GDL添加量3.0%,酸酐添加量12.5%时,大豆分离蛋白凝胶的溶胀性、pH响应性最佳。     

中性蛋白酶酶解酰化大豆分离蛋白功能特性的研究

利用中性蛋白酶对琥珀酰化大豆分离蛋白进行酶解改性,考察pH值、酶解温度和加酶量对其功能特性的影响,通过单因素和中心组合试验确定最优酶解改性条件:pH值为6.82、酶解温度为48℃、加酶量为6627U/mL。酶解改性后琥珀酰化大豆分离蛋白的功能特性均有较大提高,与改性前的大豆分离蛋白相比溶解度、乳化性、乳化稳定性、起泡性和起泡稳定性分别提高了32.28、3.89、4.41、2.5、1.22倍。     

琥珀酰化改性高溶解度大豆分离蛋白的工艺优化

采用琥珀酸酐对大豆分离蛋白进行酰化改性,测定改性前后大豆分离蛋白溶解特性的变化,并建立蛋白质溶解度与改性条件关系的数学模型,利用四元二次正交旋转组合设计试验法优化出琥珀酰化大豆分离蛋白的适宜条件:大豆分离蛋白质量分数7.0%,反应温度54℃,琥珀酸酐添加量11%,反应时间2 h.该条件下制备的酰化蛋白的溶解特性与未改性的大豆分离蛋白相比提高了15.73倍.     

酰化对大豆分离蛋白发泡性能的影响

采用乙酸酐和琥珀酸酐对大豆分离蛋白(SPI)进行化学改性.研究了酰基化程度、pH和离子强度对SPI发泡性能的影响.结果表明,随酰化试剂用量的增大,酰基化程度不断提高,在相同酰化试剂用量的条件下,乙酰化程度高于琥珀酰化.SPI的发泡性经酰化改性后得到明显改善,且随酰基化程度的增大而逐步提高,琥珀酰化的作用更突出;但酰化不利于SPI的泡沫稳定性,其随酰基化程度的增大而不断下降,琥珀酰化的下降更显著.     

Maleic anhydride derivatives of a protein isolate: preparation and functional evaluation

African locust bean protein isolate (NPI) was acylated with maleic anhydride at various concentrations. Addition of maleic anhydride at the levels of 0.1, 0.5 and 1.0 g/g of protein produced 36.4% (MP1), 43.7% (MP2) and 73.6% (MP3) of maleylated protein isolate, respectively. Water absorption capacity increased after maleylation but oil absorption capacity reduced progressively with increase in level of modification. Results also revealed that gelation capacities reduced after protein modifications. Emulsifying activity (EA) and emulsion stability (ES) increased following protein modification. In addition, corresponding increases in emulsifying properties were observed with increase in degree of modification of the proteins. Maleylation improved the foaming capacity of the native protein. Foaming capacity increased with increases in protein concentration for both native and maleylated protein derivatives while progressive decline in foam stability occurred with increases in level of protein modification.     

Functional properties of chemically modified proteins of sardine meal defatted with 1-propanol

After extracting oil from sardines using 1-propanol, the proteins of the residual defatted meal were chemically modified using either succinylation, acetylation, maleylation or phosphorylation, and their functional properties were investigated. The solubility and viscosity of defatted meal protein was improved by succinylation and maleylation. The modified proteins had higher emulsifying activity. Succinylated and maleylated proteins had superior emulsifying capacity and emulsion stability. The nutritional qualities of the modified proteins, based on their amino acid compositions, were somewhat decreased. Modification of the electrostatic and hydration characteristics of protein molecules to a more highly charged state by succinylation and maleylation could be effective in improving the functional properties of defatted meal proteins.     

高固形物浓度对大豆分离蛋白酸性蛋白酶酶解产物功能特性的影响

本文系统研究了提高固形物浓度对酸性蛋白酶酶法改性大豆分离蛋白分子量分布、氮溶解指数、分散稳定性、持水力、乳化性、起泡性和泡沫稳定性的影响。结果表明:大豆分离蛋白经过酸性蛋白酶控制酶解制备的改性大豆分离蛋白,其产物氮溶解指数、起泡性均有明显提高,分散稳定性略有提高;但持水力、乳化性、泡沫稳定性有所降低。在相同水解度下,随着酶解体系中固形物浓度的提高,改性大豆分离蛋白的分散稳定性、持水力、乳化活性均呈上升趋势,酶解产物中分子量小于10 kDa的肽段以及氮溶解指数呈下降趋势。当水解度小于8%时,低浓度酶解产物起泡性高于高浓度酶解产物,而水解度超过8%时,高浓度酶解产物起泡性大体高于低浓度酶解产物。     

Functional Properties of Acylated Pea Protein Isolates

Pea protein isolates were acylated with succinic and acetic anhydride at 1.0, 3.0, and 5.0 mmol anhydride/g protein. The chemically modified isolates showed increased emulsifying capacity, emulsion stability, foam capacity and stability, and water adsorption compared to untreated pea protein isolate. In general, the greater the extent of acylation, the greater the improvement in emulsification properties compared to the untreated protein isolate; however, improvement at greater than 3.0 mmol anhydride/g protein was slight. Acetylation at 3 mmol/g increased foam capacity to the greatest extent. Water adsorption was enhanced to the greatest extent in protein isolates acetylated at 5 mmol/g. Acylation lowered the isoelectric point of protein isolates compared to untreated isolate. In vitro enzyme hydrolysis of the protein isolates, as determined by a multienzyme system of trypsin, chymotrypsin and peptidase, was not impaired by acylation.     

大豆乳清蛋白功能特性的研究

对经过膜分离技术提取的大豆乳清蛋白的功能特性进行研究。主要研究了pH对大豆乳清蛋白的溶解特性、起泡性能及乳化性能的影响,并对大豆乳清蛋白的组成成分进行了电泳分析。结果表明,大豆乳清蛋白具有较好的溶解性及起泡性,但泡沫稳定性及乳化性不如大豆分离蛋白。大豆乳清蛋白主要包含6种成分。     

Modification of the low-molecular weight basic albumin fraction from rapeseed (Brassica napus L.) by acetylation. Part 2. Selected functional properties

The influence of acylation on surface functional properties, solubility and heat-induced aggregation of the low-molecular weight basic protein fraction (napin) from rapeseed was studied. While the native protein was soluble over the whole pH-range, the exhaustively acetylated one became precipitable in the weakly acidic range. Acetylation of 70–80% of the protein amino groups caused a stabilizing against heat-induced aggregation. The native protein had a high foam capacity and stability which were only slightly changed after acylation. Decreasing volume specific work in the order native>acetylated>succinylated protein pointed, however, to an improved foamability of acylated napin. Succinylation increased the interfacial tension on the oil/water interface, while acetylation gave both an increasing and a decreasing effect depending on the degree of modification. The emulsifiying capacity decreased after acylation in the order native>acetylated>succinylated.     

Functional Properties of Guar Proteins

Water and fat absorption, emulsification capacity (E.C.), foaming capacity (F.C.), and foam stability (F.S.) of guar meal and protein isolate have been determined and compared with those of soybean meal and isolate. Guar meal had lower water absorption capacity, similar fat absorption capacity and greater F.S. and E.C. than soybean meal. Guar protein isolate (GPI) had lower water absorption capacity but higher fat absorption capacity than soy protein isolate (SPI). The foaming capacity and emulsification capacity were similar at all pH's except around pH 4. However the foam stability of GPI was greater than that of SPI.     

Improvement of the Functionality of Soy Protein by Introduction of New Thiol Groups through a Papain-catalyzed Acylation

A novel papain-catalyzed acylation between N-acetyl-L-homocysteine thiolactone (AHTL) and terminal or side-chain amino groups of soy protein resulted in covalent introduction of new sulfhydryl groups and the improvement of protein functionalities. Acylation was carried out with 10% soy protein, 1% AHTL and 0.1% papain (w/v) in the presence of L-cysteine and EDTA as activators for papain, and incubated at pH 10.0 and 20°C for 8 hr. It was proposed that acylation was a two-step process, involving fast transthioesterification to form an acyl thioenzyme, and a subsequent aminolysis step between the acyl thioenzyme and the amino groups of protein yielding peptide or isopeptide linkages. Solubility, emulsifiability, foamability and some Theological properties of the modified soy protein increased with increase in degree of acylation. Only foam stability decreased.     

FUNCTIONING POTENTIAL OF SOY, COTTONSEED, AND PEANUT PROTEIN ISOLATES PRODUCED BY INDUSTRIAL MEMBRANE SYSTEMS

Protein isolates from toasted and untoasted soy flour, glandless cottonseed flour and peanut flour were produced by ultrafiltration. Their functional characteristics were evaluated relative to those of a commercial soy isolate. Whippability, foam capacity and stability, heat gelation, emulsitication capacity, oil absorption, and hydration were measured. Nitrogen solubilities and color readings were also obtained. In many instances membrane-produced isolates were equal to or superior in performance to that of the commercial isolate. Membrane isolated soy products yielded foam viscosities in excess of 300,000 cps as compared to 33,000 cps for the commercial isolate. The presence of whey proteins in membrane produced isolates markedly enhanced their functionality.     

高固形物浓度对风味蛋白酶催化制备改性大豆分离蛋白功能特性的影响

高固形物浓度酶解反应具有终产物浓度高、废水少、冷却和浓缩能耗低、设备尺寸小等优点,是蛋白控制酶解的研究热点之一。本文系统研究了提高固形物浓度对风味蛋白酶酶法改性大豆分离蛋白分子量分布、溶解性、分散稳定性、持水力、乳化性、起泡性和泡沫稳定性的影响。研究结果表明:大豆分离蛋白经过风味蛋白酶控制酶解制备的m SPI,其产物溶解性、分散稳定性、起泡性均提高,持水力、乳化性、泡沫稳定性降低。在相同水解度下,随着固形物浓度的提高,m SPI的分散稳定性、持水力、乳化性均呈上升趋势。当水解度8%时,低浓度酶解产物起泡性高于高浓酶解产物,而水解度超过8%时,高浓酶解产物起泡性大体高于低浓酶解产物。风味蛋白酶制备的m SPI的溶解性与酶解固形物浓度无明显关系。