改性大豆蛋白在植脂奶油中的应用

研究了改性大豆蛋白的乳化性、乳化稳定性、起泡性,以及其替代进口酪朊酸钠应用于植脂奶油对其搅打时间、起泡率、保形性、变粗程度、入口即化感、光泽度、细腻度、油腻感的影响,研究表明,改性大豆蛋白的乳化性、乳化稳定性、起池陛介于进口酪朊蛋白和国产酪朊蛋白问,优于国产大豆分离蛋白;改性大豆蛋白替代进口酪朊酸钠50％应用于植脂奶油产品品质良好。     

谷朊粉的乙酰化和磷酸化复合改性研究

本文采用乙酸酐和三聚磷酸钠对谷朊粉进行了复合改性，实验表明：复合改性后的谷朊粉的功能性质比未改性前或单独采用乙酸酐和三聚磷酸钠改性都有显著的改善；以三聚磷酸钠和乙酸酐的总用量为谷朊粉的15％，三聚磷酸钠和乙酸酐的添加比例为3：2时，所制得的复合改性谷朊粉的溶解度为88．3％，乳化度为98．8％，起泡性为250mL，起泡稳定性为180mL，具有良好的功能性质。     

酶法与非酶法磷酸化改性食品蛋白质的研究进展

磷酸化是一种重要的蛋白质修饰改性手段,可以有效改善食物蛋白质的功能性质,如乳化性、溶解性、凝胶性、热稳定性等。蛋白质磷酸化改性方法主要可分为酶法与非酶法两种,其中酶法磷酸化常使用蛋白激酶作为磷酸基团的供体,对蛋白质进行修饰。主要的蛋白激酶包括环磷酸腺苷依赖蛋白激酶(CAMPdPK)和酪蛋白激酶Ⅱ(CK-Ⅱ)。非酶法磷酸化常见的改性试剂主要包括三氯氧磷、焦磷酸钠、三聚磷酸钠和葡萄糖-6-磷酸等。本文对近年来蛋白质磷酸化的有关报道进行了总结归纳,并通过介绍磷酸化蛋白的磷酸键性质、磷酸化肽段及位点的鉴定,阐述了不同磷酸化试剂的反应机制及其对蛋白质构效关系的影响,为通过定向的磷酸化修饰而改善蛋白质特定的功能性质提供了理论依据与参考。     

大豆蛋白-瓜尔豆胶水解物Maillard反应共聚物的乳化特性研究

研究了不同水解时间的瓜尔豆胶对蛋白质-多糖Maillard反应共聚物的乳化特性的影响及不同水相条件下共聚物与酪朊酸钠乳化特性的差异。研究表明,瓜尔豆胶的酸水解时间对大豆分离蛋白-多糖共聚物的乳化活性和乳化稳定性都有明显的影响。水解40min的瓜尔豆胶与大豆分离蛋白反应10 d的共聚物具有优良的乳化性能;在0.3mol/L NaCl和pH 4.0的酸性条件下,共聚物的乳化活性和乳化稳定性都明显高于商品乳化剂酪朊酸钠;在90℃热处理60 min后其乳化活性和乳化稳定性仍接近未经热处理时的酪朊酸钠的乳化活性和稳定性。该共聚物作为安全高效的天然高分子食品乳化剂具有广阔的应用前景。     

大豆分离蛋白-麦芽糊精Maillard反应共聚物的乳化特性研究

研究了不同相对湿度(RH)下反应的大豆分离蛋白-麦芽糊精的Maillard共聚物的乳化特性。研究发现,蛋白质与多糖质量比R为3∶1的共聚物在79%RH下反应7d具有良好乳化活性,其在pH7.0和pH4.0时的乳化活性和乳化稳定性都接近商品乳化剂酪朊酸钠,在0.2mol/LNaCl时的乳化活性也明显优于酪朊酸钠,但乳化活性却低于大豆分离蛋白。90℃短时间热处理不影响共聚物的乳化活性,其乳化稳定性也优于酪朊酸钠,长时间的热处理降低了乳化稳定性。     

三聚磷酸钠改性小麦面筋蛋白研究

采用三聚磷酸钠（ＳＴＰ）对小麦面筋蛋白进行磷酸化改性，确定最佳工艺条件为三聚磷酸钠浓 度与样品浓度之 为３：１３，反应时间０．５小时，反应温度２０℃及ｐＨ值９．５，并研究磷酸化对小 麦面筋蛋白功能特性的影响和对磷酸化小麦面筋蛋白进行应用试验。结果表明，用三聚磷酸 钠对小麦面筋蛋白进行磷酸化改性，小麦面筋蛋白功能性质显著改善，改性后可使乳化性、溶 解性、起泡性及其稳定性都有极大的提高，面粉烘焙品质及在灌肠中的应用均得到很大改善。     

酶改性植物蛋白质——大豆蛋白质

本文主要综述了近十年来、国内外酶改性植物蛋白的进展,以及几种酶改性植物蛋白质的方法。包括胃朊酶、碱性蛋白酶、木瓜酶、菠萝朊酶、酵母等等,一般可改善植物蛋白质的吸水性、乳化稳定性、起泡性和热塑性等。特别是对于变性蛋白质,还可用酶催化降解,提高其功能特性。酶改性植物蛋白质,可广泛地应用于肉食品、饮料、面包制品、点心制品,奶制品、人造奶油及甜食中的发泡剂等食品生产中,提高了产品的营养价值和产品的质量。     

利用转谷氨酰胺酶提高谷朊粉乳化性研究

转谷氨酰胺酶是一种催化蛋白质分子交联酶类,利用其对谷朊粉乳化性进行改良,研究酶浓度、底物浓度、pH值、反应时间、反应温度对谷朊粉乳化活性和乳化稳定性影响;在此基础上通过正交实验,探索转谷氨酰胺酶酶解谷朊粉提高乳化性最佳反应条件。分析发现五个因素对谷朊粉乳化性影响由强到弱顺序为:pH值、谷朊粉浓度、温度、时间和酶浓度。最佳酶解条件为:谷朊粉浓度为6.0%,酶浓度1.0%,反应时间为1.0h,pH值为5.0,反应温度为45℃;此时谷朊粉乳化活性为84.9%,乳化稳定性为85.7%,比酶解前谷朊粉乳化性有明显提高。     

磷酸化改性提高松仁分离蛋白乳化性研究

松仁分离蛋白是从红松松籽仁中提取出的一种蛋白质产品。本实验对松仁蛋白进行磷酸化化学改性,利用三聚磷酸钠(STP)对松仁蛋白进行磷酸化处理,改性后松仁蛋白的乳化能力显著增加,并确定了最佳的改性条件为STP浓度6.0%,提取时间为0.5h,提取温度为40℃。     

小麦面筋蛋白质的乙酰化改性

采用乙酸酐对小麦面筋蛋白质进行酰化改性 .结果表明 :小麦面筋蛋白质乙酰化的最佳反应条件为面筋蛋白质质量分数 5 % ,反应温度 35℃ ,乙酰酐用量为小麦面筋蛋白质用量的 15 % ;乙酰化改性后的面筋蛋白质 ,溶解度、乳化能力和起泡能力均得到了提高 ,乙酰化小麦面筋蛋白质对弱筋粉粉质特性的改善效果强于普通谷朊粉 .     

Structure and Property Changes of Transglutaminase-Induced Modification of Sodium Caseinate in the Presence of Oligochitosan of 5 kDa

Sodium caseinate was modified by transglutaminase-catalyzed reaction in the presence of oligochitosan of 5 kDa at two different levels, aiming to generate two glycated and crosslinked caseinate products (GC-caseinate I and II) and to clarify their respective structure and property changes. Electrophoretic analysis with aid of protein and saccharide staining confirmed that both GC-caseinate I and II were glycated and crosslinked protein products, while high-performance liquid chromatrography analysis demonstrated that both GC-caseinate I and II contained glucosamine (12.8 and 30.8 g/kg protein, respectively). In comparison with sodium caseinate, GC-caseinate I and II also contained less reactable –NH₂ groups (0.50 and 0.52 versus 0.62 mol/kg protein), more –OH groups in their molecules, but they had more ordered secondary structure than sodium caseinate. In addition, GC-caseinate I and II showed higher water-binding capacity, larger hydrodynamic radius (173.9 and 168.2 versus 145.3 nm), and larger negative zeta-potential (–32.9 and –30.9 versus –27.6 mV) in aqueous dispersions, but they exhibited lower thermal stability (namely, greater mass loss) at temperature higher than 286ºC. Oligochitosan-glycated sodium caseinate at lower and higher extents was observed to be unfavorable and favorable to the in vitro digestibility of GC-caseinate I and II, respectively. It is concluded that application of transglutaminase and the oligochitosan can modify structure and property of sodium caseinate to generate new protein ingredients with good hydration and colloidal stability.     

Soluble protein fractions from pH and heat treated sodium caseinate: physicochemical and functional properties

The physicochemical (solubility and hydrophobicity), and functional (emulsifying activity index and emulsifying capacity) properties of soluble sodium caseinate fractions were studied as a function of pH (3–8) and temperature (50–100°C). Solubility was determined by measuring protein with the Bradford and 280 nm absorbency methods. Hydrophobicity was determined fluorometrically with 1-anilino-8-naphtalenesulfonate (ANS), and cis-parinaric acid (CPA). Sodium caseinate solubility was minimal at pH 3.75–4 but the ANS and CPA-hydrophobicities and the functional properties of the soluble proteins increased in this pH range. Circular dichroic and 280 nm absorptivity measurements detected conformational changes. SDS-PAGE and reversed phase HPLC revealed substantial losses of αs₁ and β caseins following pH and heat treatment (pH 3.75 and 92.5°C) and the concomitant appearance of modified compounds. Under these same conditions, the o-phtaldialdehyde values increased suggesting partial hydrolysis of sodium caseinate. The soluble protein fractions from sodium caseinate heat treated near the pI of the caseins were shown to have enhanced emulsifying activity and capacity.     

Temperature-dependent complexation between sodium caseinate and gum arabic

Complex formation between sodium caseinate and gum arabic as a function of temperature was investigated using dynamic light scattering, fluorescence and NMR. At neutral pH, the turbidity and the particle size increased when sodium caseinate and gum arabic mixtures were heated in situ at temperatures above a critical temperature. The increases in turbidity and particle size were reversible. This effect was considered to be due to hydrophobic interactions, leading to the formation of a complex between sodium caseinate and gum arabic. ¹H NMR spectroscopy showed that ANS, which bound to caseinate at low temperatures in caseinate solution or a caseinate-gum arabic mixture, was released at high temperatures upon formation of a caseinate or caseinate-gum arabic complex. This supported changes observed in the fluorescence of 8-anilino-1-naphthalene sulfonate upon binding to caseinate, which decreased at high temperatures for caseinate alone or when sodium caseinate was mixed with gum arabic. Light-scattering (turbidity) and dynamic light-scattering studies show that the temperature-dependent complexation between sodium caseinate and gum arabic was sensitive to the mass ratio of protein to gum arabic (greater complexation at a 1:5 ratio than a 1:1 ratio) and the pH (maximum complexation at pH 6.5).     

Rheological and thermal properties of milk gels formed with κ-carrageenan. I. Sodium caseinate

Mixed gels, formed by κ-carrageenan, and sodium caseinate were studied by differential scanning calorimetry (DSC) and rheometry. DSC showed that during gelation (i.e. cooling) the thermal behaviour of κ-carrageenan was almost uninfluenced by the presence of sodium caseinate. Thus the interaction of κ-carrageenan with sodium caseinate has little (or no) effect on the carrageenan's coil-to-helix transition. In contrast, during melting, added sodium caseinate strongly modified the thermal behaviour. The DSC peak became progressively broader with addition of sodium caseinate, indicating that the junction zones are highly heterogeneous in the mixed gel. Rheometry showed that sodium caseinate strongly influences the storage modulus (G′). In experiments in which the concentration of sodium caseinate was fixed and that of κ-carrageenan varied, plots of G′ vs. concentration of κ-carrageenan were biphasic, with an abrupt change in slope at a concentration that increased linearly with the concentration of sodium caseinate. When the concentration of κ-carrageenan was constant and that of sodium caseinate varied, G′ as a function of concentration of sodium caseinate passed through a minimum. This behaviour could be modelled quantitatively, by assuming that: (a) the sodium caseinate adsorbs κ-carrageenan, but with a limited adsorptive capacity; (b) sodium caseinate aggregates (sub-micelles) with adsorbed κ-carrageenan can associate via interaction between free ends of adsorbed κ-carrageenan chains and form a gel network; and (c) the contributions to G′ from the sodium caseinate–κ-carrageenan network and the network formed by κ-carrageenan alone are additive. At low κ-carrageenan to sodium caseinate ratios, the sodium caseinate and κ-carrageenan combine to form a mixed gel. As the ratio of κ-carrageenan to sodium caseinate increases, the sodium caseinate becomes saturated and no further association with κ-carrageenan can occur—the increase in G′, as further κ-carrageenan is added, comes from a gel network formed by κ-carrageenan alone.     

Effect of phosphatase/transglutaminase treatment on molar mass distribution and techno-functional properties of sodium caseinate

Sodium caseinate was enzymatically dephosphorylated by alkaline or acid phosphatase prior to incubation with microbial transglutaminase. It was demonstrated that a higher degree of protein cross-linking by transglutaminase was achieved in dephosphorylated sodium caseinate than in non-dephosphorylated sodium caseinate. During transglutaminase treatment, about 70% protein polymers >200.000 g/mol were produced from untreated sodium caseinate, but about 90% protein polymers >200.000 g/mol from dephosphorylated sodium caseinate. Phosphatase/transglutaminase-treated sodium caseinate exhibited techno-functional properties similar to transglutaminase-treated sodium caseinate, but performed improved interfacial stabilisation behaviour as well as higher viscosity.     

Surface protein coverage and its implications on spray-drying of model sugar-rich foods: Solubility,powder production and characterisation

We have investigated the amount of protein required to produce amorphous sugar powders through spray-drying. Pea protein isolate was used as a model plant protein and sodium caseinate was used as a model dairy protein. Powder recovery in a laboratory spray dryer was used as a measure of the ease of spray drying for a given formulation. More than 80% of amorphous sucrose and fructose was produced with the addition of sodium caseinate, while the pea protein isolate was able to produce only recoveries of less than 50% of amorphous sucrose. Sensitivity of low molecular weight surfactants has been demonstrated using both ionic (sodium stearoyl lactylate) and non-ionic (polysorbate-80) surfactants. Spray-dried powders were subjected to physico-chemical characterisation and dissolution experiments. The maximum solubility of all powders was obtained after 5 min of dissolution. The solubility of the sodium caseinate increased by 6–7% in the presence of fructose and low molecular weight surfactants. The solubility of the amorphous powders of sucrose–pea protein isolate was found to be lower than amorphous powders of sucrose–sodium caseinate and fructose–sodium caseinate. The addition of sucrose in water increased the solubility of the pea protein isolate from 16.84% to more than 83%. The non-ionic surfactant (Tween-80) has reduced the solubility of sucrose–pea protein isolate–Tween-80 powders significantly (p < 0.05) compared to those of sucrose–pea protein isolate–sodium stearoyl lactylate powders. The solubility of sucrose–sodium caseinate powders was comparable to that of pure sodium caseinate, indicating that addition of sucrose into 0.13% sodium caseinate does not have any significant effect on the solubility of this protein at this concentration.     

Effects of branched-chain amino acids and sodium caseinate on milk protein concentration and yield from dairy cows

Our study investigated the separate and combined effects of branched-chain amino acids (AA) and sodium caseinate on milk protein concentration and yield. Four Holstein cows (112 d in milk) were abomasally infused with water, branched-chain AA (150 g/d), sodium caseinate (600 g/d), or branched-chain AA plus sodium caseinate (44 and 600 g/d, respectively) according to a 4 x 4 Latin square design with 8-d treatment periods. Cows were fed a dry diet based on alfalfa hay and concentrates for ad libitum intake. The ration was formulated to exceed requirements for metabolizable energy and protein using the Cornell Net Carbohydrate and Protein System. Neither daily dry matter intake (24.2 +/- 0.4 kg/d; X +/- SEM) nor milk yield (32.9 +/-; 0.4 kg/d) was affected by any of the infusion treatments. Infusion of branched-chain AA had no effect on any milk production parameters, despite a 50% increase in their concentrations. Modest increases in milk protein concentration (0.1%) and milk protein yield (62 g/d) resulted from the infusion of sodium caseinate or branched-chain AA plus sodium caseinate. True protein and whey protein concentrations in milk were also marginally increased by infusion of sodium caseinate and branched-chain AA plus sodium caseinate, and infusion of branched-chain AA, sodium caseinate, or both elevated milk nonprotein N content. Plasma urea N concentrations were elevated by the sodium caseinate and branched-chain AA plus sodium caseinate treatments. No treatment effects on other plasma metabolites or hormones were observed. Our results show no benefit of supplementation with branched-chain AA and only modest effects of sodium caseinate on milk protein concentration and yield in well-fed cows.     

Characterisation of binding of iron to sodium caseinate and whey protein isolate

The fortification of dairy products with iron is an important approach to delivering iron in required quantities to the consumer. The binding of iron (ferrous sulfate) to two commercial milk protein products, sodium caseinate and whey protein isolate (WPI), dissolved in 50 mM HEPES buffer, was examined as a function of pH and iron concentration. Sodium caseinate had more sites (n = 14) than WPI (n = 8) for binding iron, and the affinity of caseinate to bind iron was also higher than that of WPI. These differences were attributed to the presence of clusters of phosphoserine residues in casein molecules, which are known to bind divalent cations strongly. The amount of iron bound to sodium caseinate was found to be independent of pH in the range 5.5–7.0, whereas acidification (pH range 7.0–3.0) caused a marked decrease in the amount of iron bound to WPI.     

Creaming Stability of Oil-in-Water Emulsions Formed with Sodium and Calcium Caseinates

Creaming stability of emulsions formed with calcium caseinate, determined after storage of emulsions at 20 °C for 24 h, increased gradually with an increase in protein concentration from 0.5% to 2.0%; further increases in caseinate concentration had much less effect. In contrast, the creaming stability of sodium caseinate emulsions showed a decreased with an increase in protein concentration from 0.5% to 3.0%. Confocal laser micrographs of emulsions formed with >2% sodium caseinate showed extensive flocculation of oil droplets with the appearance of a network structure. However, emulsions formed with calcium caseinate or emulsions formed with low concentrations of sodium caseinate (0.5% and 1.0%) were homogenous with no sign of flocculation.