利用脉冲NMR研究食品体系中的水分性质

核磁共振技术 (NuclearMagneticResonance,简称NMR)其检测快速、灵敏、方便等优点在许多化学分析领域都得到了广泛的应用。简述核磁共振的基本工作原理之上 ,综合国内外的研究结果 ,结合实例 ,介绍了利用NMR分析研究食品体系中与食品品质密切相关的水分子流动性、持水力、水结合、水化等性质 ,并展望了NMR在食品中的研究应用前景     

Pulse NMR Study of Glass Transition in Maltodextrin

A pulse nuclear magnetic resonance (NMR) technique was used to study the glass transition in maltodextrins. The spin-lattice relaxation time (T₁ and spin-spin relaxation time (T₂) of different molecular weight maltodextrins at different moisture contents and temperatures were measured using the pulse NMR tech nique. T₁, and T₂ were plotted against temperatures. From the resultant curves, the state transitions were observed and the corresponding state transition temperatures were determined. The state transition temperatures were very close to the glass transition temperatures (T_gs) determined with differential scanning calorimetry, suggesting a strong relationship between glass transition and proton relaxation behavior. Results indicate pulse NMR-based instrumentation could be very effective for the study of glass transition in food polymers.     

Monitoring Freeze-Drying by Low Resolution Pulse NMR: Determination of Sublimation Endpoint

An NMR method was developed for detection of the sublimation period endpoint during the freeze-drying of potato pieces. Longitudinal (T₁ and transverse (T₂) relaxation times were estimated using rapid NMR methods. Samples were immediately examined to determine presence of a frozen core. The plot of T₁ vs T₂ showed an abrupt increase at a point corresponding to the complete elimination of the frozen core. Similar Tj vs T₂ curves were observed when monitoring freeze-drying of a single potato piece inside the NMR probe-head. The detection of an anomalous freeze-drying is possible by monitoring the T₁ the T₂ or the free induction decay signal.     

超滤法纯化酪蛋白凝乳酶水解物中的酪蛋白糖巨肽

研究超滤法分离纯化了(CGMP)的条件,得到超滤的最佳条件是在室温下,压差为0.02 MPa,浓缩比为8.通过此方法得到比较纯的CGMP,蛋白回收率为1.77%,糖基化程度(唾液酸/蛋白质)为70.1μg/mg,并且此方法适用于工业化生产.     

碱性蛋白酶水解劣质干酪素制备酪蛋白磷酸肽的研究

本实验采用一种微生物酶碱性蛋白酶2709水解劣质干酪素制备酪蛋白磷酸肽(CPPs),采用正交实验优化其水解条件,得出了其最佳水解条件为底物浓度15%,酶浓度800u/g,pH9.0,温度55,时间2.5h.。其N/P为4.371,产率为12.88%。     

牛奶纤维——21世纪的生态纤维材料

近年来发达国家大量废弃的服装已造成环境污染 ,研制新型“绿色”生态纺织品已成为人们的迫切需要。为了解决纺织品生态环保问题 ,一些国家投入了大量的科研经费和人力进行绿色纺织品的研究开发。如目前国内外市场上已经和正在出现的众多的绿色纺织品 ,他们采用的是生产过程无污染的纤维 ,像Ｔｅｎｃｅｌ纤维、牛奶纤维、甲壳素纤维、罗布麻纤维、木浆纤维、竹纤维、豆饼纤维、玉米纤维、天然彩色棉纤维以及有机天然纤维 (指一种作物不论什么化学品都不应当接触它 ,不仅如此 ,而且有待种植这种作物的田地在种植前至少应有 3年未施用化学品而…     

酪蛋白改性

综述了酪蛋白的化学及酶法改性的方法,通过改性可以提高酪蛋白的功能性质和营养价值,从而扩大其在食品中的用途。     

Effects of Iron Source on Iron Availability from Casein and Casein Phosphopeptides

ABSTRACT: :
Iron availability from FeSO₄ in samples containing sodium caseinate (SC), casein phosphopeptides (CPP) or whey protein concentrate (WPC), and from ferric citrate (Fe-CA) in samples containing SC or CPP was measured using an in vitro digestion/Caco-2 cell culture model. In FeSO₄ spiked samples, relative availability was CPP > SC, CPP = WPC, and CPP = FeSO₄ alone. In samples containing Fe-CA, a soluble iron chelate, relative availability was CPP = SC and CPP < Fe-CA alone. These results suggest that CPP enhances iron availability from foods with low availability but does not improve and may inhibit availability from soluble iron species.     

辣木凝乳酶水解酪蛋白位点及其酪蛋白磷酸肽、酪蛋白糖巨肽

基于十二烷基硫酸钠-聚丙烯酰胺凝胶电泳,液相色谱-串联质谱法研究辣木凝乳酶对酪蛋白的酶切位点和水解特性,并分析该凝乳酶水解产生的酪蛋白糖巨肽和酪蛋白磷酸肽.结果表明,辣木凝乳酶酶切κ-酪蛋白的Arg 93-His 94位点导致凝乳,区别于其他已报道的凝乳酶,具有明显特异性.酶作用下κ-酪蛋白的米氏常数Km=0.49 m...     

Density Determinations of Some Polysaccharide Dispersions

Digital oscillator densimeter technique was used for measuring the density of the dispersions of glycogen, starch, dextrin, amylopectin and amylose in different concentrations at 40°C in the presence of distilled water as a reference.     

牛乳酪蛋白的人乳化改性研究

由于牛乳酪蛋白不易为婴儿消化吸收，通过对牛乳酪蛋白人乳化改性的研究，即运用犊牛皱胃酶的作用，减少牛乳α＿ｓ＿１－酪蛋白的量，使β－酪蛋白与α＿ｓ＿１－酪蛋白的比例由原来的０．７提高到３．ｏ以上，从而接近了人乳的消化吸收性。经人乳化改性后的牛乳可适用于新生婴儿配方乳的制造。     

基于表面活性剂的松香胶分散体的制备技术

从松香的改性、表面活性剂的使用以及乳化与分散工艺的控制三个方面介绍了基于表面活性剂的松香胶分散体的制备技术.     

Vane Yield Stress of Starch Dispersions

ABSTRACT: Yield stresses of 5% (wt/wt) cross-linked waxy maize, tapioca, and Amioca starch dispersions (SDs) were measured with the vane method at different rotational speeds ( N ). The static (σ_0S) and dynamic (σ_0d) yield stress values of each SD were measured before and after breaking down its structure under continuous shear, respectively. The difference (σ_0S - σ_0d) was associated with the stress required to break the internal bonds (σ_b). Values of total yield stress (σ₀=σ_0S) and σ_b, and shear rate were related by power law relationships. The contribution of viscous and network stresses were estimated from an energy balance model. Textural characteristics of the SDs were analyzed in a texture map.     

Rheological Behavior of High-Concentration Sodium Caseinate Dispersions

ABSTRACT: Apparent viscosity and frequency sweep (G′, G″) data for sodium caseinate dispersions with concentrations of approximately 18% to 40% w/w were obtained at 20 °C; colloidal glass behavior was exhibited by dispersions with concentration ≥23% w/w. The high concentrations were obtained by mixing frozen powdered buffer with sodium caseinate in boiling liquid nitrogen, and allowing the mixtures to thaw and hydrate at 4 °C. The low-temperature G′−G″ crossover seen in temperature scans between 60 and 5 °C was thought to indicate gelation. Temperature scans from 5 to 90 °C revealed gradual decrease in G′ followed by plateau values. In contrast, G″ decreased gradually and did not reach plateau values. Increase in hydrophobicity of the sodium caseinate or a decrease in the effective volume fraction of its aggregates may have contributed to these phenomena. The gelation and end of softening temperatures of the dispersions increased with the concentration of sodium caseinate. From an Eldridge–Ferry plot, the enthalpy of softening was estimated to be 29.6 kJ mol⁻¹. Practical Application: The results of this study should be useful for creating new products with high concentrations of sodium caseinate.     

酪蛋白磷酸肽的营养作用及其应用

酪蛋白磷酸肽（CPPs）是从牛奶的酪蛋白中提取的一种生物活性肽,现已证明具有促进钙、铁等矿物元素吸收、防止蛀牙等生理功能。本文介绍了CPPs的生理功能和作用机理,并对其在食品和药物方面的应用作了简单介绍。     

酪蛋白磷酸肽的体外功能试验

对不同级别的酪蛋白磷酸肽（Casein Phosphopeptide,以下简称CPP）促进钙吸收的体外功能性质进行了研究,测定了CPP的结合钙量、CPP阻止磷酸钙沉淀形成的效果及持钙能力.结果表明CPP对钙的结合量随温度的升高而减少,随pH值的升高而增加;CPP对阻止磷酸钙沉淀的作用随温度升高和溶液钙磷比增加而下降;随氮磷摩尔比降低,CPP阻止磷酸钙沉淀形成的最低有效浓度下降;对于不同的钙磷比,CPP的氮磷摩尔比越小,保持在溶液中的钙量越多,但每摩尔磷保持钙的摩尔数随氮磷摩尔比的降低而降低.     

牛乳酪蛋白性质的研究

研究和比较了牛乳中α＿ｓ－酪蛋白和β－酪蛋白的酸凝性质和酶水解性质，指出牛乳中α＿ｓ－酪蛋白的大量存在是造成不易消化的根本原因。     

Casein hydrolysis and peptide mapping

A series of short articles on topics of interest to the dairy industry. The subjects covered will include chemistry, consumer affairs, marketing, microbiology, nutrition and processing, and contributions of 1000–1500 words (including tables and figures) are invited from any member of the Society.