玻璃化转变与食品的加工、储存和品质

论述了食品的玻璃化转变与其加工、储存工艺及产品品质间的关系。重点介绍了玻璃化转变对食品的冷冻及干燥工艺的影响,淀粉玻璃化转变对食品的品质的影响,冰淇淋的冷冻保藏和玻璃化法超低温保存等。     

核磁共振技术对食品玻璃化及玻璃化转变温度的研究

本文综述了核磁共振技术(NMR)测定玻璃化转变温度的原理和一些实际应用的例子,以及NMR状态图的概念及其在食品玻璃化转变和转变前后食品理化性质变化的研究中的应用.     

速冻食品的玻璃化加工及保藏

介绍了速冻食品的玻璃化转变及玻璃化转变温度的测定方法,另外对玻璃化理论今后在速冻食品加工与保藏中的应用方向和研究重点也进行了探讨。     

亥磁共振技术对食品玻璃化及玻璃化转变温度的研究

本文综述了核磁共振技术（NMR）测定玻璃化转变温度的原理和一些实际应用的例子,以及NMR状态图的概念及其在食品玻璃化转变和转变前后食品理化性质变化的研究中的应用。     

玻璃化转变对食品稳定性的影响

本文首先简要介绍玻璃化转变对黏度、扩散和反应速率的影响,而后从物理稳定性、化学稳定性和生物学稳定性三个方面详细论述了玻璃化转变对食品稳定性的影响。在玻璃化转变温度附近温度降低使黏度增大,但小分子物质的扩散系数不再进一步减小。食品可能因发生玻璃化转变而丧失稳定性,但玻璃化转变并不能成为衡量食品稳定性的唯一标准,发生玻璃化转变也不意味着食品稳定性立即丧失。根据玻璃化转变可以较好地预测食品的物理稳定性,而难以有效预测食品的化学和生物学稳定性。     

论食品的玻璃化保藏

食品聚合物科学认为：在玻璃态下，造成食品品质变化的一切受扩散控制的反应，其速率均十分缓慢，甚至不会发生。食品发生玻璃化转变时的温度（称为玻璃化转变温度），可利用差式扫描量热法来测定。玻璃化保藏可以最大限度地保存食品原有的色、香、味、形以及营养成分。目前玻璃化在食品中的应用研究包括：淀粉的玻璃化相变研究，玻璃化在冰淇淋、冷冻水果及传统糯米制品中的应用研究等。如何进一步改进检测技术，深入研究食品体系的玻璃化转变动力学、热力学以及食品在贮藏期间品质的变化，以便确定货架稳定的动力学模型，有效地提高食品的品质及稳定性将是今后研究的重点。     

食品玻璃化转变及其在食品加工储藏中的应用

介绍了食品玻璃化转变的相关内容,综合国内外研究结果,介绍了其对食品加工储藏的影响。     

冷冻食品体系中的玻璃化转变

本文在玻璃态和玻璃化转变有关理论的基础上，对影响冷冻食品体系玻璃化转变及其低温稳定性的有关因素进行了介绍和讨论。     

玻璃化转变在食品贮藏中的应用研究进展

玻璃化转变是指无定形聚合物因受热从玻璃态到橡胶态(高弹态)或因冷却从橡胶态到玻璃态的转变.玻璃化转变是影响食品性质、加工特性和货架期的重要因素之一.文章介绍了玻璃化转变相关的基本理论,阐述了玻璃化转变在微生物和酿造发酵食品、果蔬、淀粉类食品、水产品、乳制品、冷冻禽畜肉类及糖果类食品贮藏方面的研究现状,并对玻璃化转变在食品贮藏的应用进行了展望.     

淀粉的玻璃化转变

综述了淀粉的玻璃化转变过程及转变温度的测定方法、影响因素，以及玻璃化转变过程在淀粉类食品加工及贮藏方面的研究进展，并提出了目前淀粉的玻璃化转变研究领域存在的问题，展望了今后的研究方向，以期为后续研究玻璃化转变温度时选择适宜的测定方法提供参考。     

超细纤维合成革玻璃化温度影响因素的探讨

采用差示扫描量热法(DSC)对超细纤维合成革的各个组分进行测试,探讨了尼龙-6、聚氨酯PU含量和表面活性剂及其它助剂对超细纤维合成革玻璃化温度(Tg)的影响。试验结果表明:尼龙-6对合成革的Tg影响最大,聚氨酯也有一定影响,其它成分影响不明显,研究结果为改善超细纤维合成革的Tg和使用性能,提供一定的理论依据。     

浅述玻璃化转变温度与食品成分的关系

食品体系的玻璃化转变温度会对食品的加工和贮藏过程及食品的品质产生重要影响。重视食品体系的玻璃化转变温度并分析其影响因素,可帮助人们更好的了解食品加工和贮藏特性,提高产品品质。该文就水分含量、碳水化合物、蛋白质、平均分子量及食品添加剂等因素与一定的食品体系的玻璃化转变温度的关系进行了综述。     

分子量对淀粉玻璃化转变温度的影响

采用相对黏度法及TDA与DSC法测定了淀粉同系物的黏均分子量和玻璃化转变温度,得到分子量对淀粉同系物的玻璃化转变的影响关系:即随着分子量的增加玻璃化转变温度也增加,当分子量增加到一定程度以后玻璃化转变温度增加趋于平缓,并得到实验关联式。根据这种关系我们可在一定的范围内根据实际生产、加工及贮存的需要,用改变淀粉体系的分子量分布的方法来改变其玻璃化转变温度。     

Coupling of dielectric and mechanical relaxations with glass transition and stickiness of milk solids

Dielectric and mechanical α-relaxations of milk solids with varying milk protein contents were determined by dielectric (DEA) and dynamic-mechanical (DMA) analysis, respectively. The frequency dependence of α-relaxations occurring around and above the glass transition was modeled by the Vogel-Fulcher-Tamman (VTF) relationship. The α-relaxations were governed by the amorphous lactose and shifted to higher temperatures when protein contents of milk solids were increased at all water activities, a_w. Increasing protein contents lowered the overall molecular motions of milk solid components which were shown by small changes in dielectric and mechanical properties above the glass transition. The α-relaxations were strongly frequency-dependent. At temperatures around and above the glass transition, the primary α processes were recorded and the corresponding relaxation times were determined. The temperature dependence of the relaxation times was affected by glass transition, solid composition and water. The relaxation times decreased with increasing temperature and water content as a result of thermal and water plasticization. Higher protein contents increased the relaxation times measured for milk solids. This was associated with small changes in α-relaxation characteristics and reduced powder stickiness. Data on the compositional effects on the relaxation times of milk solids were related to flow characteristics and powder stickiness around and above the glass transition.     

Comparison of dielectric properties and non-enzymatic browning kinetics around glass transition

Dielectric properties of maltodextrin- and poly(vinylpyrrolidone)-based food models designed for studying non-enzymatic browning rates in the vicinity of glass transition were determined at 9 frequencies from 0.1 to 1000 Hz at temperature range from −100 to 150 °C. Dielectric spectra of both materials showed a β-relaxation, an α-relaxation and significant increase in dielectricity at temperatures above the α-relaxation. The α- and β-relaxations exhibited water- and frequency-dependence. They also moved towards lower temperatures as non-enzymatic browning reactants were added. The relaxation above α-relaxation only showed a water-dependence. Dielectric analysis proved to be a sensitive method for detecting molecular mobility below the glass transition observed by differential scanning calorimetry. Dielectric properties of the food models did not, however, completely explain the previously observed differences in non-enzymatic browning rates of the different food models.     

玻璃化转变对食品加工和品质的影响

在有关玻璃态和玻璃化转变理论的基础上 ,综述了玻璃化转变对干燥、冷冻、焙烤、糖果及挤压等食品的加工与品质的影响     

Moisture sorption characteristics and glass transition temperature of apple puree powder

The aim of this study was to characterise the influence of different foam‐mat‐drying methods on the moisture sorption characteristics and glass transition temperatures of apple puree powder. Apple puree was foamed with the addition of 2.5% egg albumin and 0.5% methylcellulose. Convective air‐drying and microwave‐drying techniques were used. Also foamed puree with and without maltodextrin (6% or 15% w/w) was freeze‐dried. Moisture equilibrium data of powders were determined by using a static desiccator method in a water activity range of 0.0–0.903. Modulated differential scanning calorimetry (MDSC) was used to obtain the glass transition temperature. No effect of drying method on sorption properties and glass transition temperatures of apple puree powders was observed. The addition of maltodextrin to the apple puree caused an increase in T_g by 10–30 °C depending on the amount of incorporated additive. Addition of maltodextrin significantly reduced the hygroscopicity of apple puree powders.     

Implication of water activity and glass transition on the mechanical and optical properties of freeze-dried apple and banana slices

The interactions between water content, matrix structures and chemical and physical events in complex foods are usually regarded in terms of water activity and glass transition. In this work, the water content and water activity values that define important changes in the textural and optical properties of freeze-dried banana and apple slices have been related to the critical water content and water activity that cause the glass transition in both products. From the obtained results, it may be concluded that both approaches, glass transition and water activity, may be considered to prevent changes in the mechanical properties, while only the concept of water activity is needed to control the browning reactions that take place in the fruits.     

Kinetics of non-enzymatic browning in amorphous solid systems: distinguishing the effects of water activity and the glass transition

Debates have emerged recently on whether water activity or the state of the system as dictated by the glass transition temperature (T_g) impacts the rates of chemical reactions in reduced-moisture solid systems. The objective of this study was to evaluate the kinetics of brown pigment formation in polyvinylpyrrolidone model systems of different molecular weights so that the effects of water activity and the glass transition could be distinguished. Browning rates at different T_gs, but constant water activity, were significantly different except when all were in the glassy state. As the system changed from a glassy state to a rubbery state, the rate of browning increased 7-fold. The rate of browning also increased as water activity increased from 0.33 to 0.54, but then appeared to plateau with further increases in water activity. Thus, the rate of brown pigment formation is influenced significantly by the glass transition temperature of the system and less by the water activity. In addition, the concentration of reactants in the aqueous microenvironment had a significant impact on the rate of brown pigment formation.     

用热膨胀法测量非晶态粉体的玻璃化转变温度

根据热膨胀原理,建立了测量非晶态粉体的玻璃化转变温度的装置,给出了测量步骤和数据处理方法,考核了用该方法测量非晶态粉体的玻璃化转变温度的重复性和可靠性。结果表明,所建立的测量装置具有操作简单、造价低廉、测量重复性好等特点,可用于非晶态粉体的玻璃化转变温度Tg的测量。