法国研究添加单价盐对浓缩酪蛋白酸钠悬浮液流变学和酪蛋白酸钙溶解度的影响

法国研究了在蛋白质质量浓度40～235g／L、温度10～60℃范围内添加NaCl或KCl对浓缩酪蛋白酸钠悬浮液流变学特性的影响（拟发表于2014年7月International Dairy Journal）。     

黄参多糖水溶液流变性研究

以黄参粗糖为原料,研究黄参粗糖水溶液的流变性能,探讨温度和浓度对黄参粗糖水溶液触变、蠕变、频率和流动的影响。结果表明,黄参粗糖水溶液的黏度随着剪切速率的增加而降低,黄参粗糖水溶液表现出剪切变稀的"假塑性",呈现出"非牛顿流体"的流动特性;黄参粗糖水溶液的触变性可通过其溶液浓度的大小加以调控,而适当提高溶液浓度则可使体系的触变性能得到增强,浓度为6%时滞后圈的面积达到最大值;黄参粗糖水溶液体系的储藏模量和损耗模量均随黄参粗糖水溶液浓度增大而增大,即溶液浓度越高,体系的弹性和粘性越强,表明溶液浓度影响体系的粘弹性能。     

不同乳蛋白组分对牛乳酶凝乳特性的影响

研究不同乳蛋白组分对牛乳酶凝乳特性的影响,在脱脂牛乳中添加乳清蛋白浓缩物(whey protein concentrate,WPC)、κ-酪蛋白(κ-casein,κ-CN)、β-乳球蛋白(β-lactoglobulin,β-Lg_A和β-Lg_B)。结果表明:这些乳蛋白组分可以缩短牛乳的酶凝乳时间,而且增加凝乳后的样品黏度,凝乳样品微观结构更加紧密;而添加α-乳白蛋白(α-lactalbumin,α-La)、α-酪蛋白(α-casein,α-CN)、β-酪蛋白(β-casein,β-CN)和总酪蛋白(casein,CN)对凝乳的形成具有抑制作用,凝乳样品微观结构较疏松。采用动态光散射法测定酶凝乳过程中酪蛋白胶束分子粒径的分布情况,结果表明,酪蛋白溶液中添加WPC、κ-CN、β-Lg_A和β-Lg_B后,分子半径分布发生变化,蛋白分子趋于聚集。选择酶凝乳差异明显的原料乳样品进行双向电泳与质谱鉴定,结果表明,与牛乳的酶凝乳特性相关的差异蛋白大多是影响乳腺细胞代谢的微量生物活性蛋白质。     

粘合剂对重组牦牛肉感官品质的影响

为明确粘合剂对重组牦牛肉牦牛肉感官品质的影响,以碎牦牛肉为原料,研究了谷氨酰胺转氨酶、酪蛋白酸钠和卡拉胶添加量对重组牦牛肉感官品质的影响。结果表明,随谷氨酰胺转氨酶添加量的增加,重组牦牛肉的感官品质呈现先增加后稳定的趋势,酪蛋白酸钠和卡拉胶的添加量对重组牦牛肉影响与谷氨酰胺转氨酶的变化规律基本一致;正交试验结果表明,当谷氨酰胺转氨酶添加量为0.35%、酪蛋白酸钠添加量为0.70%、卡拉胶添加量为0.70%时,重组牦牛肉的感官品质好,感官评分为12.67±0.63,验证试验表明优化的粘合剂添加量有效可靠。     

酪蛋白——亚麻籽胶凝胶体系的流变特性受两者浓度及温度的影响

我国及澳大利亚研究人员应用流变仪研究酪蛋白——亚麻籽胶凝胶体系（亚麻籽胶浓度为0．1％～0．5％，酪蛋白浓度为15％～23％）的流变特性。     

酪蛋白在不同pH值下特性的研究

将高速离心分离的酪蛋白配制成不同pH值的溶液,然后研究了酪蛋白的Zeta电势、电导率、黏度、平均粒径和稳定性的变化规律.实验结果表明,酪蛋白溶液的Zeta电势值(绝对值)、电导率值和黏度值都是随着pH的增加而逐渐增加.平均粒径值是先减小后增加,在pH 6.2时有最小值,为26.03mm.溶液的pH在5.8-6.6之间时,体系较稳定.初步认为,当pH小于7时,降低pH会导致胶体磷酸钙的溶解,使得体系的平均粒径变小.继续降低pH会导致静电斥力的减小,酪蛋白会发生凝集,平均粒径增大,体系也会变得不稳定.     

乳清蛋白和乳化剂作用机理的研究

研究了不同添加量的乳化剂对乳清蛋白溶液特性的影响。研究结果表明,无论是亲水性的蔗糖酯还是亲油性的单甘酯,当加入到乳清蛋白溶液时,都能够有效阻止蛋白质分子的聚合。乳清蛋白Zeta电势值(绝对值)和体系的电导率值都是随着乳化剂添加量的增加先增大后降低。表面张力值都是在添加量为0.01%时达到极大值,而后随着添加量的增加显著降低。体系的黏度值随着添加量的增加一直增大。此外,同单甘酯相比,蔗糖酯能够更有效地降低体系的表面张力值、电导率值及乳清蛋白粒子的Zeta电势大小。     

油水界面上酪蛋白酸钠与羧甲基纤维素的相互作用会影响体系的稳定性

我国研究人员最近的一项研究表明,当体系pH值=7时,随着羧甲基纤维素（CMC）浓度的增加,由酪蛋白酸钠（CN）制备的水包油乳化液表面蛋白的覆盖率增加,且β-酪蛋白最易与CMC发生吸附作用;     

碘化酪蛋白添加剂在养殖业上的应用

碘化酪蛋白是利用天然优质蛋白经加碘处理,使碘固定于蛋白质分子上,该蛋白质仍然可被动物消化吸收.1944年Turner等首次报道,碘化酪蛋白能促进动物体内甲状腺素的分泌.饲料中添加碘化酪蛋白类似于添加了T3和T4(Srivastava等1967).研究发现,该蛋白被动物消化吸收之后,有显著地促进畜禽鱼虾健康生长并提高饲料利用率的作用.在美国碘化酪蛋白一直被作为奶牛和母猪的催乳添加剂,它具有调节动物甲状腺活动等功能.本文针对碘化酪蛋白在养殖业中的应用及其作用机理作一简述.     

不同水平蛋白质底物对猪结肠微生物体外发酵特性和菌体合成能力的影响

本试验旨在体外条件下,探究不同水平蛋白质底物对猪结肠微生物发酵特性的影响,了解猪结肠微生物对蛋白质的利用规律。以成年猪结肠内容物为微生物接种物,在结肠微生物发酵液中分别添加0(C组)、0.10(L组)、0.25 g/L(H组)酪蛋白水解物,厌氧发酵不同时间点(3、6、9、12、18、24 h),分别测定累积产气量、p H及微生物蛋白、氨态氮、挥发性脂肪酸浓度。结果显示:1)发酵3、6 h时,L组和H组p H显著低于C组(P0.05)。2)L组和H组累积产气量均高于C组。3)L组和H组各时间点微生物蛋白浓度均显著高于C组(P0.05),6 h时H组又显著高于L组(P0.05)。3)L组和H组各时间点氨态氮浓度均显著高于C组(P0.05)。4)短链脂肪酸和支链脂肪酸浓度随着发酵时间延长而增加,同时随着蛋白质水平增加而增加。由此可见,蛋白质底物的添加促进了肠道微生物菌体合成,但是过多的蛋白质底物水平并不能进一步提高微生物蛋白浓度;随着蛋白质水平增加,肠道微生物发酵特性进一步提高。     

pH值对海藻酸丙二醇酯溶液流变特性的影响

作为一种增稠剂,海藻酸丙二醇酯广泛应用于乳制品或乳饮料中。采用AR-G2流变仪,通过稳态流动、应变扫描、频率扫描、动态黏弹性温度扫描及动态黏度温度扫描等实验研究pH值对海藻酸丙二醇酯溶液流变特性的影响。结果表明:pH值的增加使海藻酸丙二醇酯溶液的黏度降低,同时使其黏弹性与复合黏度降低,损耗正切增加。另外,pH值低于7时,海藻酸丙二醇酯溶液的剪切稀化程度减弱,pH值高于7时,溶液的剪切稀化程度增强。同时,pH值影响海藻酸丙二醇酯溶液的黏度及黏弹性的温度效应。     

丝胶/海藻酸钠复合凝胶粒的制备及其结构性能表征

为了改良丝胶型药物载体的结构性能,将丝胶粉末与海藻酸钠溶液均匀混合后,采用氯化钙胶凝法制备了粒径为1.88 mm±0.15 mm的丝胶/海藻酸钠复合凝胶粒。红外光谱检测表明该复合凝胶粒中的丝胶与海藻酸钠之间以物理方式混和;差示扫描量热分析发现丝胶与海藻酸钠复合后,其结构稳定性有所提高;机械性检测表明丝胶/海藻酸钠复合凝胶粒具有更好的力学性能;溶胀性检测表明丝胶/海藻酸钠复合凝胶粒具有pH敏感溶胀性。研究结果表明丝胶/海藻酸钠复合凝胶粒使丝胶作为药物固定化载体的结构与性能得到改善,更有利于开发利用。     

Improvement of the emulsifying properties of porcine sarcoplasmic proteins with a low-molecular weight surfactant by the two-step emulsification method

The emulsifying properties of porcine sarcoplasmic protein (SP) with or without low-molecular weight surfactants were examined. The emulsifying activity (EA) of SP was weaker than that of sodium caseinate (CA), blood plasma (BP) and whey protein isolates at a protein concentration of 0.5–3%. Sodium chloride decreased the EA of SP. The EA of SP was about one quarter that of CA in the presence of 3% sodium chloride. As homogenization time increased, the EAs of SP and BP decreased. The EA of SP was not influenced by sucrose stearate ester (SE) with a hydrophilic-lipophilic balance (HLB) value of 16 (SE-16) but was decreased by those with HLB values of 5 and 1. Low-molecular weight surfactants such as SE-16, Tween 80 and sodium cholate improved the EA of SP with the two-step emulsification method: corn oil was previously emulsified with the surfactant before addition of SP and homogenization. In the case of the addition of SE-16 as primary emulsifier, the EA was about twice as high as that of SP alone. The same effect was shown in the emulsions formed by CA and soy protein isolate. These results indicate that the emulsifying properties of meat protein would be improved by the addition of a low-molecular weight surfactant in a two-step emulsification.     

Prerigor injection using glycolytic inhibitors in low-quality beef muscles

The objective of this experiment was to determine the effect of prerigor injection of several glycolytic inhibitors on pH, color, tenderness, and related traits of low-value beef cuts. The semimembranosus, triceps brachii, and supraspinatus muscles from each of 10 steer carcasses were removed 1 h postmortem. Control samples remained in the carcass at 2 degrees C for 24 h. Prerigor muscles were injected and tumbled with 10% (by weight) of one of four solutions: sodium citrate (NaC; 200 mM), sodium fluoride (NaF; 200 mM), sodium acetate (NaA; 200 mM), and calcium chloride (CaCl2; 300 mM). All muscles treated with NaC and NaF showed the highest pH and glycogen content (P < 0.05), indicating that glycolysis was inhibited. Injection of NaC in semimembranosus and supraspinatus produced the tenderest meat (P < 0.05), showing a greater increase in tenderization at 3 d than at 7 d postmortem. Treatment did not affect color or oxidation-reduction potential, but all treated muscles tended to be more oxidative (higher oxidation-reduction potential). Sodium citrate was identified as a potential compound to enhance tenderness of prerigor muscle without altering color. Further studies are required to investigate its effect on palatability traits and to provide a basis for commercial application of the process.     

Effects of electrolyte solutions for oral administration on clotting of milk.

The effect of electrolyte solutions commercially formulated for oral administration on clotting of milk was investigated in vitro. Rennet or abomasal fluid was used as the clotting agent. Electrolyte solutions that contained large amounts of bicarbonate or citrate (greater than 40 mEq/L) had marked adverse effects on milk clotting, probably because bicarbonate increased pH and because citrate chelated calcium. Addition of solutions that did not contain alkalinizing agents resulted in normal or enhanced clotting, and enhancement was associated with the presence of acid phosphate salts. Electrolyte solutions that included acetate as the alkalinizing agent did not interfere with milk clotting as long as pH of the final solution was acidic and minimal amounts of citric acid salts were present (less than 10 mEq/L). Acetate-containing electrolyte solutions can be used for oral administration in calves in which alkalinization of blood without interference with milk clotting is desired.     

添加剂对紫花苜蓿青贮饲料发酵品质的影响

为提高紫花苜蓿青贮饲料的发酵品质,抑制不饱和脂肪酸的损失,以无添加剂为对照,研究了添加剂：苯甲酸钠、酪蛋白酸钠、十六烷酸、糖蜜和丙酸,对紫花苜蓿青贮饲料发酵品质和脂肪酸的影响。青贮65 d后开窖,检测发酵品质指标和各种脂肪酸的含量。结果表明：对照组的pH低于4.50,乳酸含量达到54.25 g·kg^-1 DM,丁酸含量低于5.00 g·kg^-1 DM,弗氏评分为64.33,具有良好的发酵品质。与青贮前相比,青贮后苜蓿青贮饲料中的亚油酸（C18：2n6）和亚麻酸（C18：3n3）的含量显著增加（P<0.05）。青贮后,与对照组相比,十六烷酸和酪蛋白酸钠添加组分别不显著（P>0.05）和显著地（P<0.05）降低了乳酸含量;酪蛋白酸钠添加组增加了丁酸含量（P<0.05）;二者的弗氏评分低于50.00,降低了发酵品质。与此相反,苯甲酸钠、丙酸和糖蜜添加组不同程度地增加了乳酸含量,降低了pH,减少了氨态氮和酸性洗涤纤维的含量,弗氏评分分别为70.33、74.33和67.67,进一步提高了青贮发酵品质。与对照相比,苯甲酸钠和丙酸添加组不同程度地增加了C18：2n6或C18：3n3的含量,而糖蜜添加组降低了C18：2n6和C18：3n3的含量（P<0.05）。综上所述,丙酸和苯甲酸钠适宜于作为青贮添加剂生产优质紫花苜蓿青贮饲料。     

Rheological behaviors of Graphitic oxide/Sodium alginate dispersions

One kind of the carbonaceous materials with high performance was chosen to prepare dispersions of GO/SA. The influence of GO contents on rheological properties of SA solution was studied with rotational rheometer under different test conditions. Steady rheological results showed that the solutions exhibited shear-thinning behaviors. The viscosities decreased with the increasing of shear rates. Dynamic rheological results showed that both SA solutions and SA/GO suspensions exhibited liquid-like behaviors. Moreover indicate that incorporation of small amounts GO can significantly increase the G' and G' of SA spinning solution, reflecting good dispersion of GO nanolayers in SA solution, which was proved by ColeCole curves.     

Effect of different non-chloride sodium sources on the performance of heat-stressed broiler chickens

1. One hundred and eighty 1-d-old broiler chicks were used to evaluate the effect upon broiler performance during severely hot summer months of three different sodium salts: sodium bicarbonate (NaHCO3), sodium carbonate (Na2CO3) and sodium sulphate (Na2SO4), in starter and finisher diets having an identical electrolyte balance (DEB) of 250 mEq/kg. 2. The non-chloride sodium salts were added to contribute the same amount of sodium and were substituted at the expense of builder's sand in the basal diets containing common salt (NaCl) as Na and Cl source. 3. Each diet was fed to three experimental units having 15 chicks each until 42 d of age. Severe heat-stress conditions, maintained in the rearing room, were indicated by high average weekly room temperature (minimum 29.3 degrees C; maximum 38.0 degrees C). 4. Diets containing sodium salts gave better body weight gain, feed intake and feed to gain ratio than the control diet. Sodium salts also enhanced water intake as well as water to feed intake ratio. This effect was more pronounced in broilers fed NaHCO3 supplement (with NaCl in the basal diets). 5. The increased water intake resulted in lower body temperature in heat-stressed birds fed NaHCO3 supplemented diet than in birds fed other sodium salts. A lower mortality rate was noted with NaHCO3 (15.15%), Na2CO3 (13.64%) and Na2SO4 (15.15%) supplements than with the control (33.33%) treatment. 6. Better carcase and parts yield were observed in sodium supplemented broilers. Sodium salts reduced the alkalotic pH and enhanced the blood sodium content, which ultimately improved the blood electrolyte balance and overall performance of heat-stressed broilers. 7. Supplementing broiler diets with sodium salts improved the live performance of heat-stressed broilers and better productive performance was noted with NaHCO3 than other sodium supplements.     

Effects of Sodium Caseinate and Varying Protein Sources on In Vitro Fermentation of Forages by Mixed Equine Cecal Microorganisms

To assess the impact of protein on fermentation by equine cecal microorganisms, cecal fluid from 4 cecally cannulated horses was used to inoculate fermentation bottles containing buffer, forage, and supplemental protein. In experiment 1, sodium caseinate (SC) provided 0, 0.5%, 1%, 2%, or 4% additional crude protein (CP) to bottles containing alfalfa or native warm-season prairie grass hay. Bottles were equipped with continuous gas pressure monitors and placed into a shaking incubator for 48 hours at 39°C. Cultures with alfalfa had greater (P < .0001) in vitro dry matter disappearance (IVDMD), neutral detergent fiber disappearance (NDFD), acid detergent fiber disappearance (ADFD), cumulative gas production, and total volatile fatty acid (VFA). Sodium caseinate increased gas production (P ≤ .05) and decreased pH (P < .003) in cultures with grass hay. Sodium caseinate at 1%, 2%, or 4% additional CP increased IVDMD, NDFD, and ADFD (P < .01), while 4% additional CP also increased total VFA (P < .01). For experiment 2, SC, fishmeal, soybean meal (SBM), whey, porcine blood plasma, and L-lysine hydrochloride were added to supply 2% additional CP to cultures with grass hay. All protein sources decreased pH and increased IVDMD, NDFD, and ADFD (P ≤ .01), with the largest effects elicited by SC, L-lysine, and whey (P ≤ .05). Total VFA (P ≤ .04) and gas (P ≤ .05) production increased with L-lysine, whey, SC, SBM, and fishmeal. While protein supplementation had minimal effects on cultures containing alfalfa, it altered fermentation of grass hay, more notably with more soluble protein sources.     

Evaluation of manufacturing variability, diffusion of filling solutions, and long-term maintenance of occlusion in silicone hydraulic occluders

OBJECTIVE: To evaluate manufacturing variability, diffusion of filling solutions, and maintenance of occlusion over time in 3 sizes of silicone hydraulic occluders (HOs). SAMPLE POPULATION: 2-, 5-, and 20-mm HOs (HO2, HO5, and HO20, respectively). PROCEDURES: Manufacturing variability was analyzed by comparing variation in internal luminal areas and filling volumes within each size group. Occluders were filled to 100% occlusion with air (n = 4), saline (0.9% NaCl) solution (4), or sodium hyaluronate (4) and submerged in simulated body fluid. Changes in luminal area and weight were recorded for 133 days to evaluate maintenance of occlusion. RESULTS: Considerable variability in uninflated luminal area and fill volumes was observed among the 3 sizes of HOs. Loss of occlusion developed in the first 12 hours in all air-filled HOs. Fluid-filled occluders were reliable in maintenance of occlusion after 133 days (99.99% for HO20, 99.59% for HO5, and 90.40% for HO2), although diffusion of saline solution and hyaluronate from all HOs was confirmed by detection of significant decreases in weight over time. There was no significant difference in weight loss between HOs filled with saline solution and HOs filled with sodium hyaluronate. CONCLUSIONS AND CLINICAL RELEVANCE: Saline solution or sodium hyaluronate may be used as a filling solution in the HOs tested. Maintenance of occlusion was best in the larger sizes. Saline solution or sodium hyaluronate should be used in future clinical investigations of HOs. Retrograde filling to remove air should be used when filling HOs with fluid.