酪蛋白种类和二次均质工艺对再制稀奶油搅打特性的影响

本研究旨在分析3 种常见的酪蛋白产品,胶束酪蛋白浓缩物（micellar casein concentrate,MCC）、酪蛋白酸钙（calcium caseinate,CaC）及酪蛋白酸钠（sodium caseinate,NaC）对再制稀奶油搅打特性的影响,以及再制稀奶油进行二次均质后其搅打特性的变化。结果表明：MCC、CaC及NaC再制稀奶油的搅打特性受酪蛋白质量分数的影响,且其对二次均质工艺的敏感性不同。MCC和CaC的质量分数较高（1.5%和2.5%）时,制备的稀奶油具有良好的搅打特性,最大起泡率在170%～200%范围内,泄漏率在0～1.5%范围内;进行二次均质后最大起泡率和泄漏率的变化较小。而NaC在较低的质量分数（0.5%）条件下制备的稀奶油才可具有较好的搅打特性,最大起泡率为（198.2±4.0）%;当NaC质量分数增至1.5%时,最大起泡率下降至（119.0±15.4）%。二次均质后NaC再制稀奶油的最大起泡率下降,泄漏率增加。研究认为,以MCC和CaC为原料制备的稀奶油无论是否进行二次均质,均有良好的搅打特性。     

酪蛋白和工艺对再制稀奶油稳定性的影响

本研究主要通过测定再制稀奶油的粒径、界面蛋白含量、黏度、微流变性质分析胶束酪蛋白浓缩粉(micelle casein concentrate,MCC)、酪蛋白酸钙(calcium caseinate,CaC)粉及工艺(灭菌、二次均质)对再制稀奶油稳定性的影响。结果表明:蛋白添加量为1.0%(质量分数,后同)和2.0%时,MCC再制稀奶油的失稳系数分别为0.396±0.011、0.032±0.001,说明稳定性随蛋白添加量的增加而提高,而CaC再制稀奶油稳定性的变化规律与之相反。灭菌后,MCC再制稀奶油脂肪球粒径D3,2、界面蛋白含量及黏度显著增加(P0.05),均方根位移(mean square displacement,MSD)明显降低,CaC再制稀奶油与MCC再制稀奶油的变化明显不同,除界面蛋白含量由3.9～5.5 mg/m~2增至5.2～7.0 mg/m~2外,粒径D3,2、黏度及MSD(2.0%CaC再制稀奶油除外)无明显变化。二次均质后,MCC再制稀奶油脂肪球粒径D3,2、界面蛋白含量及黏度显著下降(P0.05),MSD明显增加,而CaC再制稀奶油样品中除1.0%CaC再制稀奶油粒径D3,2由(2.80±0.10)μm下降至(2.06±0.11)μm外,其他理化性质变化不明显。虽然MCC乳化能力较CaC低,但其在添加量2.0%时制备的稀奶油稳定性最好。工艺会导致再制稀奶油(尤其是MCC再制稀奶油)理化性质间平衡的改变,再制稀奶油的稳定性也随之改变。     

一种水包油包胶型乳液的制备及其在乳化肠中的应用

以结冷胶和无水氯化钙为内水相凝固剂,酪蛋白酸钠为外水相乳化剂,制备一种水包油包胶（S/O/W）型 乳液。以多重乳液粒径和分布为指标,研究酪蛋白酸钠添加量对S/O/W型多重乳液加工适应性的影响。结果表明： 正交试验得到S/O型单重乳液最佳制备条件为：内水相中结冷胶添加量0.2%、无水氯化钙添加量0.5%;内水相乳化 剂聚甘油蓖麻醇酯添加量2.5%;油相为精炼猪油,油水体积比3∶2;剪切速率17 500 r/min,剪切时间1.5 min。将制 得的S/O型单重乳液与不同添加量酪蛋白酸钠混合制得S/O/W型多重乳液。当酪蛋白酸钠添加量0.1%时,S/O/W型 多重乳液粒径符合加工要求,且贮藏、热处理、剪切稳定性较好。以多重乳液替代猪脂肪制备的低脂乳化肠与高脂 （精炼猪油含量20%）乳化肠外观不存在明显差异;微观结构观察结果表明,多重乳液在乳化肠中包裹良好、分布 均匀。     

超微粉碎冷榨火麻粕对法兰克福香肠品质特性的影响

研究不同添加量（0%、0.5%、1.0%、1.5%、2.0%、2.5%）的超微粉碎冷榨火麻粕（micronized cold pressed hemp meal,MCPHM）对法兰克福香肠品质特性的影响。结果表明：随着MCPHM添加量的增加,法兰克福香肠的蒸煮损失、乳化稳定性、硬度、弹性及咀嚼性呈现先增加后降低的趋势（P<0.05）;法兰克福香肠的水分活度随着MCPHM添加量的增加而显著降低,而pH值则显著增加（P<0.05）。因此,MCPHM能够有效改善法兰克福香肠的品质,并且在添加量为1.0%时具有最佳改善效果。     

酪蛋白磷酸肽(CPP)理化特性的研究

研究了CPP的溶解性、起泡性及乳化性。CPP在pH2.0～10.0范围内,溶解性除在pH4.0约为90％外,其它均高于90％,且随pH增加而增大。与酪蛋白相比,CPP具有更好的起泡性和泡沫稳定性。CPP对热及Ca~(2 )具有较好的稳定性。CPP乳化力较酪蛋白下降约20％,乳化性下降2.89％,乳化稳定性下降1.45倍。     

酪蛋白水解物对低脂发酵酸奶发酵速度及品质的影响

研究了不同添加量的酪蛋白水解物对低脂发酵酸奶的发酵速度、储存稳定性和质构特性的影响。结果表明,酪蛋白水解物具有明显促进低脂发酵酸奶发酵、缩短发酵时间的作用;可提高低脂发酵酸奶的储存稳定性,主要表现在提高表观黏度和降低储存过程中乳清析出;添加酪蛋白水解物可明显改善低脂发酵酸奶的质构特性。综合考虑,低脂发酵酸奶中添加酪蛋白水解物最适量范围为1.0%～1.5%。     

奶渣酪蛋白酸钙的制备及在植脂末中的应用

以奶渣酪蛋白为原料,制备的酪蛋白酸钙中钙含量为指标,采用单因素试验,确定奶渣酪蛋白酸钙的生产工艺,对奶渣酪蛋白酸钙的理化性质进行测定,以奶渣酪蛋白酸钙作为乳化剂制备植脂末,并与奶渣酪蛋白酸钠及市售酪蛋白酸钙制备的植脂末进行对比,通过测定其粒径和ζ-电位探究植脂末的稳定性。结果表明：溶液pH值为7,料液浓度为1.00%,Ca(OH)2添加量为1.6%时,奶渣酪蛋白酸钙中蛋白质含量为93.76%,钙含量为1.35%;奶渣酪蛋白酸钙具有优异的乳化能力,乳化液稳定性可达到70%以上,起泡能力高于奶渣酪蛋白酸钠;由奶渣酪蛋白酸钙制备的植脂末平均粒径最小,电位绝对值最大,稳定性最好,并且随储藏时间的延长,粒径和ζ-电位变化最小,储藏稳定性最好。     

酪蛋白磷酸肽-钙络合物对酸乳贮藏特性的影响

为探究酪蛋白磷酸肽-钙（CPP-Ca）络合物对酸乳贮藏特性的影响,研究CPP-Ca络合物不同添加量对酸乳21 d贮藏期内乳酸菌总数、pH值、滴定酸度、乳清析出率及黏度的影响。与对照组比较,当CPP-Ca络合物添加量为0.15 g/100 mL时,酸乳中乳酸菌存活率从32.92%提高至47.15%（P＜0.05）;滴定酸度增长率从9.96%降低至7.06%（P＜0.05）;乳清析出率降低了0.4%（P＜0.05）,黏度比提高了5 729 mPa·s （P＜0.05）。结果表明,CPP-Ca络合物的添加能增加酸乳贮藏期内的乳酸菌总数,延缓酸度积累,降低乳清析出率,增加黏度,改善酸乳贮藏期内的产品品质。     

盐及酪蛋白酸钠对藜麦面团及面条品质的影响

本文以藜麦面为研究对象,通过添加KCl、NaCl、酪蛋白酸钠以改善藜麦面团的性质,研究了不同处理条件对藜面团质的硬度、咀嚼性、黏度等质构特性以及储能模量、损耗模量、复合粘度等流变学特性的影响。结果表明:当添加的水量为50%藜麦面团成型的光滑程度、弹性较好;当藜麦面中加入1.5%酪蛋白酸钠+1% KCl所制备的藜麦面团粘性适中、硬度和弹性较好;NaCl、KCl、酪蛋白酸钠的加入,均可改善面团的G'、G'、黏度,1.5%酪蛋白酸钠+1% KCl加入,可增大藜麦面团的G'、G'、黏度;NaCl和酪蛋白酸钠都可以明显的改善藜麦面条吸水率,NaCl可降低藜麦面条的干物质损失率,KCl的作用与之相反,而酪蛋白酸钠与1% KCl联合使用,在增加其吸水率的同时减少了干物质损耗率,当同时添加2.0%酪蛋白酸钠和1% KCl条件下达到最适,而且恢复能力达到最佳;酪蛋白酸钠与1% KCl可增加藜麦面条表面片层的致密程度。因此,1.5%酪蛋白酸钠+1% KCl的添加量对藜麦面团的弹性、硬度、咀嚼性均达到最佳,同时添加2.0%酪蛋白酸钠和1% KCl能显著（P<0.05）改善藜麦面条的蒸煮损失及干物质损失率,降低面汤浊度,还可以增加藜麦面条的硬度,从而增加其咀嚼性。     

添加酪蛋白水解肽改善酸乳的加工特性

向牛乳中添加不同含量菠萝蛋白酶酪蛋白水解肽（0.1%、0.3%、0.5%）,测定酸乳发酵及冷藏过程中理化、微生物和风味指标变化。结果表明,添加酪蛋白水解肽（casein hydrolytic peptides,CHP）加快了酸乳发酵后期pH值下降,缩短发酵时间;CHP添加量为0.1%时发酵时间较对照组缩短了34 min。微流变测定表明,添加CHP降低了发酵后期酸乳的弹性指数（elasticity index,EI）和流动性指数（fluidity index,FI）,但宏观黏度指数（macroscopic viscosity index,MVI）有所升高。扫描电镜图像显示,各组酸乳样品均呈多孔网状结构,适量添加CHP（0.1%）可以改善酸乳的胶体结构,使酸乳网络结构更致密均匀。酸乳冷藏期间,添加CHP可以提高发酵剂菌株的活菌数,一定程度地促进酸类、醛类和酮类等风味化合物的形成,添加0.3%的CHP降低了酸乳EI;随着CHP添加量的增加（0.3%、0.5%）,酸乳的硬度及胶着性逐渐下降,但对持水力、内聚性及黏性无明显影响。本研究为CHP在酸乳加工中的应用及产品品质和功能性提升提供技术参考。     

Stability of Cream Liqueurs Containing Low-Molecular-Weight Surfactants

The effect of adding low-molecular-weight surfactants, commercial glycerol monostearate (GMS) or sodium stearyl lactylate (SSL), on the stability of simulated cream liqueurs (dairy based oil-in-water emulsions containing alcohol) was investigated. The presence of 0.4–0.5 wt % GMS or SSL led to a substantial reduction in creaming at ambient temperature as well as a longer shelf-life at 45°C. A protein analysis of the aqueous phase after emulsion centrifugation showed that added GMS or SSL displaced a significant proportion of caseinate from the surface of the emulsion droplets. Improved stability with respect to creaming appeared to be associated with a change in bulk rheological properties of the emulsion, probably arising from complex formation between low-molecular-weight emulsifier and caseinate, both in bulk aqueous solution and at the surface of the fat droplets.     

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.     

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.     

Oil-in-Water Emulsions Stabilized by Sodium Caseinate or Whey Protein Isolate as influenced by Glycerol Monostearate

Competitive adsorption between glycerol monostearate (GMS) and whey protein isolate (WPI) or sodium caseinate was studied in oil-in-water emulsions (20 wt % soya oil, deionized water, pH 7). Addition of GMS resulted in partial displacement of WPI or sodium caseinate from the emulsion interface. SDS-PAGE showed that GMS altered the adsorbed layer composition in sodium caseinate stabilized emulsions containing < 1.0 wt % protein. Predominance of β-casein at the interface in the absence of surfactant was reduced in the presence of GMS. The distribution of α-lactalbumin and β-lactoglobulin between the aqueous bulk phase and the fat surface in emulsions stabilized with WPI was independent of the concentration of added protein or surfactant.     

STABILITY OF OIL-IN-WATER EMULSIONS. 2. Effects of Oil Phase Volume, Stability Test, Viscosity, Type of Oil and Protein Additive

SUMMARY –Stability of oil-in-water emulsions stabilized in sodium caseinate, gelatin and soy sodium proteinate was found to be increased by either an increase in the aqueous phase protein concentration (0.5–2.5%) or oil phase volume (20–50%). Both factors were significantly interrelated. Emulsions stabilized by soy sodium proteinate were generally higher in stability as compared to those stabilized by gelatin or sodium caseinate. With emulsions containing gelatin, greater stability occurred when the stability testing temperature was increased from 37–70°C and when the time interval was decreased from 24 hr to 90 min. Maximum relative viscosities of emulsions stabilized by gelatin and sodium caseinate were 2.0 and 2.5, respectively. Emulsions stabilized by soy sodium proteinate were quite viscous, with relative viscosity from 1.5–30 depending on both protein concentration and oil phase volume. Interchanging the emulsified oil among corn, soybean, safflower and peanut oils did not alter emulsion stability when examined at three concentrations of soy sodium proteinate. Changing the oil to olive oil significantly increased emulsion stability at each soy sodium proteinate level with oil phase volumes of 30, 40 and 50%.     

酒精对酪蛋白酸钠溶液及O/W乳状液的影响

介绍了酒精对酪蛋白酸钠溶液及酪蛋白稳定的O/W乳状液性质的影响 .试验表明酒精在一定程度上可以降低酪蛋白酸钠的溶解度 .界面张力的测定则表明酒精的存在在很大程度上可以降低油—水界面和油—酪蛋白溶液界面的界面张力 .含酒精的乳状液体系的粘度会由于酒精的存在而提高 ,在酒精体积分数达 3 0 %时 ,乳状液体系的粘度会突然大幅度升高 .通过O/W乳状液的分层稳定性测定可发现 ,低浓度的酒精可以提高酪蛋白稳定的乳状液的分层稳定性 ,但酒精质体积分数超过 3 2 %时 ,乳状液的分层稳定性会受到破坏 .含酒精的O/W乳状液体系中油相含量的提高在一定范围内可以提高乳状液的稳定性 ,但高分散相浓度的含酒精的乳状液体系中由于连续相中酒精浓度的提高使乳状液体系稳定性下降 .     

Influence of xanthan gum on the formation and stability of sodium caseinate oil-in-water emulsions

Studies have been made of the changes in droplet sizes, surface coverage and creaming stability of emulsions formed with 30% (w/w) soya oil, and aqueous solution containing 1 or 3% (w/w) sodium caseinate and varying concentrations of xanthan gum. Addition of xanthan prior to homogenization had no significant effect on average emulsion droplet size and surface protein concentration in all emulsions studied. However, addition of low levels of xanthan (≤0.2 wt%) caused flocculation of droplets that resulted in a large decrease in creaming stability and visual phase separation. At higher xanthan concentrations, the creaming stability improved, apparently due to the formation of network of flocculated droplets. It was found that emulsions formed with 3% sodium caseinate in the absence of xanthan showed extensive flocculation that resulted in very low creaming stability. The presence of xanthan in these emulsions increased the creaming stability, although the emulsion droplets were still flocculated. It appears that creaming stability of emulsions made with mixtures of sodium caseinate and xanthan was more closely related to the structure and rheology of the emulsion itself rather than to the rheology of the aqueous phase.     

Oil-in-water emulsions stabilized by sodium caseinate: Influence of pH,high-pressure homogenization and locust bean gum addition

The effect of pH, addition of a thickening agent (locust bean gum) or high-pressure homogenization on the stability of oil-in-water emulsions added by sodium caseinate (Na-CN) was evaluated. For this purpose, emulsions were characterized by visual analysis, microstructure and rheological measurements. Most of the systems were not stable, showing phase separation a few minutes after emulsion preparation. However, creaming behavior was largely affected by the pH, homogenization pressure or locust bean gum (LBG) concentration. The most stable systems were obtained for emulsions homogenized at high pressure, containing an increased amount of LBG or with pH values close to the isoelectric point (pI) of sodium caseinate, which was attributed to the size reduction of the droplets, the higher viscosity of continuous phase and the emulsion gelation (elastic network formation), respectively. All the studied mechanisms were efficient to decrease the molecular mobility, which slowed down the phase separation of the emulsions. In addition, the use of sodium caseinate was also essential to stabilize the emulsions, since it promoted the electrostatic repulsive interactions between droplets.