淀粉磷酸单酯对面团流变特性的影响研究

[目的]探讨不同取代度及添加量的淀粉磷酸单酯对面团粉质及拉伸特性的影响。[方法]通过控制反应时间,制备得到两种不同取代度的淀粉磷酸单酯(0.019和0.011),然后分别按面粉重量的0.4%、0.7%、1.0%添加到面粉中,研究其粉质特性和拉伸特性。[结果]面团中按1.0%添加取代度为0.019的淀粉磷酸单酯时,其面团形成时间降低为2.4 min,面团稳定时间增加到4.9 min,软化度降低到86,面团延伸度从24.27 mm提高到25.78 mm;最大拉伸力从0.024 g增加到0.049 g。[结论]淀粉磷酸单酯具有较好的增稠性、乳化性和使用安全性等特点。在弱筋粉中添加淀粉磷酸单酯,可以减少面团形成时间,提高面团稳定时间,降低了软化度,改善面团的粉质特性,淀粉磷酸单酯的取代度越高,其改善效果越好。     

地衣芽孢杆菌D3.11凝乳酶对切达干酪质地特性的影响

为揭示地衣芽孢杆菌D3.11凝乳酶对切达干酪成熟过程中质地的影响,利用地衣芽孢杆菌D3.11凝乳酶制作切达干酪(CDF组)和切达干酪类似物(CD3组),采用商品凝乳酶作为对照(CCF组),分析干酪成熟过程中质构、流变特性、微观结构的变化规律.结果表明:3组干酪的硬度随着干酪的成熟而增加,而弹性和咀嚼性则呈现下降趋势,C...     

凝固型酸奶在储存过程中的特性研究

研究了凝固型酸奶在4℃储存期间粘度、总酸度和活菌数的变化规律。以发酵好的酸奶为基点保存12 d,总共7个点对酸奶的各个指标进行检测。检测表明,酸奶的粘度在储存期间是逐渐降低的,活菌数随总酸度逐渐上升而降低,而总酸度是逐渐升高的。酸奶的粘度和酸度存在一定的相关性。     

Fast X-ray tomography analysis of bubble growth and foam setting during breadmaking

The use of fast X-ray computed microtomography (CMT) shows that the development of gas cell structures during fermentation first depends on a critical time, t₁, determined by overall expansion and before which bubbles grow freely according to a simple exponential law. Afterwards, coalescence rapidly prevails and then leads to a heterogeneous structure, for t≥t₂, characterized by a continuous void phase likely to be stabilized by liquid film walls. This result confirms the involvement of minor components in addition to gluten protein for obtaining a desirable bread texture and suggests that their interfacial properties need to be investigated. The use of fast in situ CMT with careful 3D image analysis also provides data for the validation of numerical models of bubble growth. These small scale experiments could be extended to follow the rheological properties of expanding doughs and the temperature-state changes of wheat flour biopolymers which govern bread baking.     

Effect of shear rate on microstructure and rheological properties of sheared wheat doughs

Structure formation in dough systems is the result of an interplay between processing conditions and subsequent interactions in the protein phase. These interactions can be both of a covalent (disulfide bonds) and physical nature and occur at all length scales.     

Rheological properties and structural changes in steamed and boiled abalone meat

ABSTRACT: Changes in tissue structures, rheological properties, and water content of abalone meat were studied in relation to boiling and steaming time. The adductor muscle of abalone Haliotis discus, which was removed directly from the shell, was boiled or steamed for 1 h, 2 h, and 3 h. When observed under a light microscope and by scanning electron microscopy, structural changes in the myofibrils were greatest in the boiled abalone meat compared with the steamed meat. When heating time was increased from 1 h to 3 h, the instantaneous modulus E ₀ of boiled abalone meat decreased gradually with increased heating time, whereas the E ₀ of steamed abalone meat was reduced when heated for 2 h. When heated for 1 h, the relaxation time of steamed abalone meat was much longer than that of boiled meat. There were no significant changes in the relaxation time of abalone meat among the different boiling times, but the relaxation time of steamed abalone meat was reduced gradually with increasing heating times. The study's results confirmed that the difference in rheological properties between the boiled and steamed meats was due mainly to the denaturation level of myofibrils when heated for 1 h, as well as due to the changes in water and solid content and the manner in which the inner water was exchanged after heating time was increased from 1 h to 3 h.     

Nonlinear,time-dependent shear flow behaviour,and shear-induced effects in wheat flour dough rheology

Retardation test, step-shear rate experiments, low-amplitude and large-amplitude dynamic measurements have been combined to study the nonlinear and time-dependent viscosity of dough and shear-induced effects of flow on dough structure. Despite large quantitative differences in linear viscoelastic constants, doughs from different flours or with different water contents display the same type of flow behaviour. Shear-induced structural changes cause flow to shift from a high viscosity steady-state regime to a low viscosity one. The process, irreversible, is responsible for the time-dependent character of dough viscosity and seems to be controlled by the mechanical energy absorbed. Nevertheless, the two steady-state viscosities follow the same shear-thinning flow curve, fitted by a Cross equation with an exponent close to 1; the Newtonian plateau is approached at very low shear rate values. Viscosity data obtained on different doughs yield a unique flow master curve in reduced coordinates. Shear-induced structural changes cause also the linear viscoelastic plateau modulus of dough to decrease; this progressive weakening of the network structure is irreversible and seems governed by the accumulated strain. These characteristics of dough rheology are discussed with reference to the behaviour of concentrated suspensions.     

赤桉材干燥终了调湿处理中的流变行为

在实验室的小型调温调湿箱中对25 mm厚赤桉干燥材进行终了调湿处理,并以切片法分析调湿过程中的弹性应变和机械吸附应变特性.结果表明:经24 h的处理,表层的吸湿效果显著,含水率上升达5%,而板材的平均含水率上升2.5%～3.0%;表层压缩弹性应变在经历处理开始3 h内的短暂上升后迅速下降,而整个处理过程中心层的拉伸弹性应变变化不大;处理9 h后,次表层的压缩弹性应力比表层的大,产生反向的应力梯度;处理中,木材表层吸湿软化发生了补充收缩,缩小了内外各层长度差异,应力减小;表层软化有效地减小乃至消除机械吸附应变,但由于干燥历史的影响,机械吸附应变的变化滞后于含水率的变化,在处理的第3～9 h间下降幅度最大.     

影响面条品质的小麦品质性状及其QTLs定位的研究进展

本文总结了国内外近几年关于面条品质的研究资料,对影响面条品质的小麦品质性状,包括蛋白质的含量、麦谷蛋白亚基组成、直链淀粉的含量、淀粉特性、Waxy蛋白、面筋的含量、沉淀值、面团的主要特性等进行了概述,对这些小麦品质性状在染色体上QTLs定位的研究情况进行了综述,以期为面条专用小麦的选育和我国面条加工业的发展提供科学的参考。     

Biohydrogel induced soil–water interactions: how to untangle the gel effect? A review

Biohydrogels such as microbial exudates and root‐derived mucilage are soil‐born cross‐linked polymers, able to form porous three‐dimensional networks during water uptake. The gel effect is the variation of soil properties, such as soil hydrology and soil structural stability, resulting from biohydrogel swelling in soil. Conventionally, soil–water–hydrogel interactions are investigated by measuring soil bulk properties such as water retention curves and porosity, without further analyzing the effect of biohydrogel phases in soil on a quantitative basis. Therefore, the evaluation of advanced and novel methods for the characterization of biohydrogel phases in soil and soil–water–hydrogel interactions is necessary. This review evaluates currently available methods for their potential to analyze processes associated to the gel effect. A promising approach to investigate the spatio‐temporal distribution of biohydrogel phases in porous media is based on Nuclear Magnetic Resonance (NMR) such as ¹H‐NMR relaxometry, as well as on imaging techniques such as Environmental Scanning Electron Microscopy (ESEM). Especially NMR techniques enable the identification of different water populations based on their differences in the relaxation, and thus the mobility of water molecules in biohydrogels and non‐gel water in soil pores. Rheology measures the flow behavior of biohydrogels, providing information on the structural behavior of the hydrogel network and its gelling mechanism. Soil rheology further quantifies the effect of the biohydrogel phases on the interactions between soil particles, and thus the impact on soil microstructural stability. However, rheology does not elucidate the spatio‐temporal distribution and structural state of biohydrogel phases in soil. All in all, a systematic combination of rheology, NMR and suitable imaging methods seems promising and necessary in order to elucidate the still widely unknown gel effect in soil.