米蛋白肽铁的螯合条件优化

以米渣为蛋白肽原料,以FeSO4为铁源制备蛋白肽螯合铁。通过实验确定用复合胰蛋白酶进行限制性酶解,用酶量为1%,理想的酶解工艺条件:酶解温度50℃,固液比1∶5,pH为8,酶解时间4h;通过单因素实验和正交实验,采用氮气保护措施,确定了最佳螯合工艺条件:蛋白肽与亚铁盐的配体摩尔比为2∶1,pH为5.0,反应温度50℃,反应时间40min。可得到棕灰色粉末状蛋白肽螯合铁,螯合率为94.4%。     

Effects of calcium and pH on spun fibres produced from plasma-alginate mixtures

When a solution of blood plasma and sodium alginate (protein: polysaccharide ratio 3:1) was extruded into coagulating baths of calcium chloride there was a rapid increase in shear strength of the fibre bundles with a rise in salt concentration up to 3% calcium chloride. Above this concentration no further increase in shear strength was observed. The ratio of plasma protein to alginate was between 0·84 and 1·1 in all tows produced from unbuffered calcium chloride baths.

Extruding the dope into 5% calcium chloride baths of pH values between 2 and 8 indicated that fibre strength was independent of pH in the range 4 to 8. Below pH 4 the tows rapidly decreased in shear strength to a minimum at pH 3·5. Decreasing the pH further led to an increase in fibre strength as acid denaturated protein coprecipitated with the polysaccharide. The ratio of plasma to alginate in the tows was around 1·0 for pH values above 3·5, rapidly increasing to 2·8 at pH 2·0.     

萱藻褐藻胶的提取及流变学特性的研究

以萱藻为原料,采用碱提法提取褐藻胶,探讨萱藻褐藻胶的最佳漂白工艺条件以及褐藻胶溶液的流变学特性。实验结果表明:用次氯酸钠做漂白剂,每600mL滤液加3mL有效氯浓度为4%的次氯酸钠溶液,即3:600,pH10.5左右,漂白时间40min,漂白温度35℃,能够得到较满意的漂白效果;萱藻褐藻胶溶液粘度随剪切速率的增加而降低,是假塑性流体,具有触变性;褐藻胶溶液具有粘弹性,在低频率区域体系以粘性为主,高频率区域体系以弹性为主;此外,温度、溶液质量分数、盐、蔗糖也会影响褐藻胶溶液的粘度。     

Associative phase separation involving canola protein isolate with both sulphated and carboxylated polysaccharides

Associative phase separation within admixtures of canola protein isolate (CPI) and anionic polysaccharides (alginate and ι-carrageenan) was investigated as a function of pH (1.50–7.00) and biopolymer weight mixing ratio (1:1–50:1, w/w) by turbidimetric analysis. Solubility of formed complexes was also studied vs. protein alone as a function of pH. In both CPI–polysaccharide systems, critical pH, associated with the onset of soluble and insoluble complexes, shifted to higher pHs as the mixing ratios increased to a 20:1 CPI–polysaccharide ratio, and then became constant. Complexes formed primarily through electrostatic attractive forces with secondary stabilisation by hydrogen bonding. Solubility of the CPI–alginate system was significantly enhanced relative to CPI alone or CPI–ι-carrageenan.     

Ability of Chelators to Alter the Physical Location and Prooxidant Activity of Iron in Oil-in-Water Emulsions

ABSTRACT: Our research determined whether chelators could influence physical location and prooxidative activity of lipid-phase iron in oil-in-water emulsions. Corn oil saturated with ferric ions was used to produce polyoxyethylene 10 lauryl ether-stabilized oil-in-water emulsions. Continuous-phase iron concentrations increased with increasing chelator concentrations (10 to 100 μM) and storage time (1 to 7 d). At pH 3.0, the concentration of continuous-phase iron was higher in the presence of EDTA and sodium tripolyphosphate (STPP) than citrate. STPP and EDTA were more effective than citrate at inhibiting lipid oxidation at pH 3.0. These results indicate that chelators can increase the transfer of iron in lipid to the aqueous phase, thus altering its prooxidant activity in oil-in-water emulsions.     

内源乳化凝胶法制备微米级海藻酸微胶囊的研究

内源乳化凝胶法中的一些物理化学参数(海藻酸钠浓度,乳化剂用量,水与油体积比等)影响海藻酸微胶囊的大小及粒径分布,文中对这些物理化学参数进行了研究。实验表明:微胶囊的平均粒径随着内部水油相体积比的增高和乳化剂Span80用量的增大而减小,随着海藻酸钠浓度的增大而增大。制备平均粒径为40～60μm海藻酸微胶囊的最佳工艺条件是:海藻酸钠浓度为15g/L,乳化剂Span 80用量为0.7%,水与油的体积比为1:8,CaCO_3与NaALG质量比为1:5。内源乳化凝胶法对大规模生产较小粒径的微胶囊有广阔的前景。     

海藻酸钠固定化亚油酸异构酶及其酶学性质初步研究

以海藻酸钠为载体固定化亚油酸异构酶。研究了海藻酸钠浓度、酶用量、CaC12浓度、固定化时间对固定化过程的影响。结果表明,最佳固定化工艺是：以4%的海藻酸钠为载体、应用海藻酸钠溶液用量与酶液量的体积比3：1、3%的CaC12固定化5h。固定化酶的最适pH值为7.0,与游离酶相比,提高了0.5个pH单位;固定化酶和游离酶最适温度分别为35℃和30℃;固定化酶比游离酶具有更好的温度和pH值适应性。     

超顺磁性海藻酸钠的制备及其结构研究

采用氧化法制备巨藻型及海带型超顺磁性海藻酸钠,通过X-衍射、扫描电镜、古埃磁天平分析;结果表明,氧化法生成的磁性离子体达到纳米级（44．656～66．99nm）,在海藻酸钠中分布比较均匀,巨藻型海藻酸钠制备的磁性海藻酸钠磁化率比海带型海藻酸钠的高1～2倍。     

Iron Binding by Ovotransferrin from Ferric Nitrilotriacetate at pH 5 and pH 5.5

Binding of iron to ovotransferrin (OTf) in egg white at low pH was studied. At pH 5 iron as ferric nitrilotriacetate (FeNTA) bound to only 25% of the OTf iron-binding sites. Although this binding caused a 1°C increase in OTf denaturation temperature, enthalpy of denaturation apparently decreased. At pH 5.5, the apo-OTf denaturation temperature was about 4°C higher than at pH 5. FeNTA bound to 40% of the OTf iron-binding sites; again a small increase in denaturation temperature and an apparent decrease in enthalpy was observed. Work with purified OTf suggests that the denaturation enthalpy decrease observed in egg white may be due to overlapping of the OTf and albumin endotherms.     

两种海藻酸钠基凝胶的溶胀和质构性能

壳聚糖、果胶和海藻酸钠是天然多糖,具有良好的生物相容性和生物可降解性等优点。以CaCl_2为交联剂制备壳聚糖-海藻酸钠水凝胶和果胶-海藻酸钠水凝胶,研究Ca Cl2浓度、多糖质量比(壳聚糖与海藻酸钠、果胶与海藻酸钠)和交联温度对水凝胶在模拟人体胃肠道环境(pH 1.2胃、pH 6.8小肠、pH 7.4结肠缓冲溶液)中溶胀性能的影响。当壳聚糖或果胶和海藻酸钠质量比为1.25∶1、CaCl_2浓度为0.09 mol/L、温度为60℃时,制备的水凝胶在pH 1.2溶液中溶胀率最小,在pH 6.8和pH 7.4溶液中溶胀率较大;结果表明所制备水凝胶具有pH值敏感性。此外,在优化条件下水凝胶具有较好的质构性能。     

Iron, Zinc, Copper and Magnesium Binding by Cooked Pinto Bean (Phaseohs vulgaris) Neutral and Acid Detergent Fiber

Iron, copper and zinc but not magnesium were bound by neutral (NDF) and acid (ADF) detergent fiber obtained from cooked pinto beans. Iron binding increased with higher pH, higher iron concentration, higher fiber concentration and smaller fiber particle size. Maximum binding of iron was at pH 6.5 and minimal binding at pH 4.0 for both NDF and ADF. A 50% decrease in particle size increased iron binding by 8%. Binding of copper and zinc increased with higher copper and zinc concentrations. Both NDF and ADF had a greater affinity for copper than for either iron or zinc. Scatchard plots indicated the presence of two types of binding sites for zinc, one type for iron, and one type for copper.     

Preparation of Chitosan‐Alginate Nanoparticles for Trans‐cinnamaldehyde Entrapment

Trans‐cinnamaldehyde incorporated chitosan‐alginate nanoparticles were synthesized using the ionic gelation and polyelectrolyte complexation technique. Alginate, chitosan, calcium chloride, and trans‐cinnamaldehyde at predetermined concentrations were complexed electrostatically to optimize particle size and loading efficiency. A final methodology using optimized processing parameters (for example, stirring time, homogenization time, equilibration time, and droplet size) was developed. The best working alginate to chitosan mass ratio was determined to be 1.5:1 at a pH dispersion of 4.7. Particle size (166.26 nm) and encapsulation efficiency (73.24%) were further optimized at this mass ratio using an alginate:calcium chloride mass ratio of 4.8:1, alginate:trans‐cinnamaldehyde mass ratio of 37.5:1, a 18 gauge syringe needle, stirring times of 90 min, 15 min of homogenization at 21000 rpm, and equilibration time of 24 h. Optimized nanoparticles showed increased stability (6 wk) and translucency in solution. The final radical scavenging effect of loaded particles in apple juice was 62% and trans‐cinnamaldehyde was just as available to react in free form as it was in inclusion complexes. The final nanoparticle system with modified and optimized processing parameters reduced the size by 43.6% and increased entrapment efficiency by 17.2%. Nanoparticles resembled a spherical shell and core type arrangement (that is, spherical, distinct, and regular) and were in the size range of 10 to 100 nm.     

Characterization of copper adsorption onto an alginate encapsulated magnetic sorbent by a combined FT-IR, XPS, and mathematical modeling study

Copper adsorption onto calcium alginate encapsulated magnetic sorbent is studied in this paper. The objective of this study was to qualitatively and quantitatively elucidate the copper binding onto the sorbent. The adsorption increases from around 0 to almost 100% as the initial pH is increased from 2 to 5. A maximum adsorption capacity of 0.99 mmol g(-1) is achieved. The FT-IR and XPS studies show that the C-O in carboxyl group of alginate directly attaches to the copper ion that leads to most of the adsorption. A mathematical model is developed, and it includes ion exchange between the calcium and the copper, coordination reaction between the functional group and the copper, as well as surface complex formation between the iron oxide and the copper. The model is capable of describing and predicting effects of various key operational parameters on the adsorption process, such as initial pH, metal concentration, and dosage of sorbent.     

不同条件对胖大海胶表观黏度的影响

以胖大海胶研究对象,研究pH、钙离子浓度、不同阳离子、蔗糖及其他胶体对胖大海胶黏度的影响。结果表明:pH偏高或偏低、阳离子存在均使胶体溶液表观黏度下降;随着蔗糖浓度增加,溶液表观黏度逐渐增大;胖大海胶与瓜尔豆胶复合后胶体溶液黏度大于原胶体的黏度,而与黄原胶、海藻酸钠、琼脂复合则小于原胶体黏度。     

响应面法优化微波辅助米渣蛋白糖基化改性工艺

为了改善米渣蛋白的溶解性,提高蛋白质的利用率,本文以米渣蛋白和海藻酸钠为原料,利用微波对米渣蛋白进行接枝改性处理,比较分析海藻酸钠:米渣分离蛋白质量比、微波温度、微波时间、微波功率、pH对接枝度和褐变度的影响,并采用Central Composite中心组合实验设计,以接枝度为响应值,建立米渣分离蛋白与海藻酸钠接枝反应的二次回归模型,通过响应面分析和方差分析得出影响RDP与海藻酸钠接枝度的最优参数为:海藻酸钠:米渣分离蛋白质量比为1.88:1、pH10.18、微波功率186 W、微波温度77.7℃,在此条件下接枝度为36.87%,与实验设计中心点的最大值37.03%误差在5%范围内。本文所建立的米渣蛋白改性方法不仅用时短、效率高,而且改性效果好,具有较大的推广应用前景。     

Effect of calf feeding regimes and diet EDTA on physico-chemical characteristics of veal stored under modified atmospheres

Physico-chemical characteristics of veal from 30 calves allotted to five different rations with respect to iron bioavailability were evaluated at packaging and after 2 and 4 weeks of storage under both 100% CO(2) and 100% N(2). The five diets were 'Milk', 'Grain', 'Mix' (combination of Milk and Grain) and 'Mix + EDTA' and 'Grain + EDTA' where 15 mg EDTA were added per mg Fe in the feed concentrate. Diet EDTA was generally more influential on veal quality than storage treatments. The chelator caused an unexpected pH drop in veal stored four weeks irrespective of storage conditions (p ≤ 0.05). However, the colour, texture and flavour of meat from animals fed EDTA in the Grain- and Mix-ration was equivalent to that of Milk-fed veal (p ≤ 0.05). The EDTA treatments also improved the appearance of veal under anoxic atmospheres. Upon storage however, the chelator increased veal drip losses (p ≤ 0.05) and also cooking losses from Grain-fed calves (p ≤ 0.05). Packaging under CO(2) decreased pH (p ≤ 0.05) and increased drip losses (p ≤ 0.05) but did not alter other physico-chemical parameters. Dietary treatments had no effect on shear forces (p > 0.05) which decreased after two weeks in storage (p ≤ 0.05) independent of gas atmospheres. Overall, the quality characteristics of pale veal were obtained following addition of EDTA in Grain- and Mix-fed animals and were maintained in storage. This approach looks promising for the veal industry but warrants further research.     

玫瑰茄花色苷的降解动力学及抗氧化性

以玫瑰茄花色苷为原料,研究了不同pH、温度和稳定剂条件下花色苷的降解动力学,并研究了热处理过程中玫瑰茄花色苷抗氧化能力的变化。结果表明:玫瑰茄花色苷的降解符合一级反应动力学模型,pH<3条件下花色苷的热稳定性比pH≥3条件下强;同一pH下,花色苷的降解速率k随着温度升高而增大,降解半衰期t_1/2则随之减小。在pH2.0、80 ℃和pH5.0、100 ℃时,花色苷分别有最低的降解速率常数(0.2539 h-1)和最高的降解速率常数(0.6547 h-1),以及最大半衰期值(2.73 h)和最小的半衰期值(1.06 h)。在80、90和100 ℃条件下,花色苷的降解速率常数均随着CMC和海藻酸钠添加量的增加而减小。同时,在80、90和100 ℃条件下加热2.5 h后,玫瑰茄花色苷的体外抗氧化能力均显著降低(p<0.05)。添加CMC和海藻酸钠能显著地提高花色苷的氧化稳定性,且添加海藻酸钠比添加CMC的效果更好。     

海藻酸钠固定化环糊精糖基转移酶的研究

通过单因素分析与正交试验设计确定了海藻酸钠包埋固定环糊精葡萄糖基转移酶(CGTase)的最佳条件。即,海藻酸钠7%(终浓度约为2.3%),CaCl_2浓度3%。海藻酸钠体积与酶液体积比1∶2,固定化时间2.5 h。探讨了固定化CGTase的酶学性质,固定化酶的最适pH及最适温度与游离酶相比没有明显变化,pH稳定性及热稳定性的范围均比游离酶要宽。连续使用7批次操作仍保持75%的酶活力,显示出良好的稳定性。     

低氧胁迫下发芽玉米淀粉特性及高γ-氨基丁酸玉米饮料开发

以糯玉米（京甜紫花糯）为试材,研究低氧胁迫下其籽粒发芽期间淀粉特性变化,筛选了高γ-氨基丁酸（γ-aminobutyric acid,GABA）含量的玉米保健饮料的稳定剂及产品配方。结果表明,玉米经低氧胁迫发芽72 h,GABA含量增加12.2 倍,达0.65 mg/g,淀粉含量显著下降,淀粉糊透光率降低27.8%,淀粉持水性、持油性和乳化性均增强,淀粉乳化稳定性降低7.4%;玉米匀浆最佳料液比1∶8,最优复合稳定剂为羧甲基纤维素钠0.03%、藻酸丙二醇酯0.09%、海藻酸钠0.04%和黄原胶0.06%,其饮料静置沉淀率最低,仅为3.7%;白砂糖添加量为4.8 g/100 mL和体系pH值为4.6 时,模糊综合评价表明该高GABA玉米饮料达到“容易接受”级别,符合消费者饮用要求。     

Complex coacervation of pea protein isolate and alginate polysaccharides

Complex coacervation between pea protein isolate (PPI) and alginate (AL) was investigated as a function of pH (1.50–7.00) and mixing ratio (1:1–20:1 PPI:AL) by turbidimetric analysis and electrophoretic mobility during an acid titration. Conformational changes to the secondary structures during coacervation were also studied by Raman spectroscopy. Critical structure-forming events associated with the formation of soluble (pH 5.00) and insoluble (pH 2.98) complexes were found for a 1:1 PPI–AL mixture, with optimal biopolymer interactions occurring at pH 2.10 (pH_opt). As mixing ratios increased between 4:1 and 8:1, critical pHs shifted towards higher pH. Maximum coacervate formation at pH_opt occurred at a mixing ratio of 4:1. Electrophoretic mobility measurements showed a shift in net neutrality from pH 4.00 in homogenous PPI solutions, to pH 1.55 for the 1:1 mixture. As biopolymer ratios increased towards 8:1 PPI:AL, net neutrality shifted to higher pHs (～3.80). Raman spectroscopy revealed minimal complexation-induced conformational changes. Findings could aid in the design of pH-sensitive biopolymer carriers for use in functional food and bio-material applications.