MECHANICAL PROPERTIES AND VISCOELASTIC CHARACTERISTICS OF TWO VARIETIES OF YAM TUBERS (DIOSCOREA ALATA)

The main mechanical properties and viscoelastic characteristics of two different cultivars of yam have been measured in this work. Using an Instron machine, some different tests has been applied: puncture, uniaxial compression and bending in order to calculate the parameters: maximum stress of penetration, stress and strain at fracture, deformability modulus and the constants a and b from the Peleg model. It is concluded that the Pico de Botella cultivar has a fracture stress higher (0.57 MPa) than the Diamante 22 cultivar (0.31 MPa). Also, the degree of deformation at fracture is higher (32 versus 21%). In relation with the constants from the Peleg viscoelasticity model, there are no differences between cultivars, both having the same value of the asintotic stress ( a =  0.43) and very similar for the relaxation stress rates (Pico de Botella, b =  0.03 and Diamante 22, b =  0.02).

PRACTICAL APPLICATIONS

Information on mechanical properties of yam that has not been reported in the literature.     

碱法分离大米蛋白和淀粉工艺的优化及其产品功能性质研究

本文以籼米为原料，研究了碱法提取分离大米蛋白和淀粉的工艺，并对大米分离蛋白和大米淀粉的功能性质进行了研究。确定了碱法分离大米蛋白和淀粉的最佳工艺条件：氢氧化钠溶液浓度为0．075mol／L；提取时间6h：料液比1：7g／mL；温度40℃。该优化条件下可以得到纯度高于80％大米分离蛋白，蛋白提取率为86．23％，淀粉回收率为92．12％。所得大米分离蛋白溶解性、起泡性好，乳化性能欠佳。     

DYNAMIC VISCOELASTIC PROPERTIES OF PASTA AS A FUNCTION OF TEMPERATURE AND WATER CONTENT*

Pasta samples were tested in the linear viscoelasticity range using a dynamic mechanical thermal analyzer over the temperature range of 25 to 95C and the water content range of 12 to 20% (weight of water/weight of solids). To obtain wholesome pasta samples at different moisture levels, the intermittent sorption technique was used. The behavior of G′ and tanδversus temperature curves exhibited a transition, which was determined to be the glass transition by making comparisons to the literature values of glass transition for starch and semolina extrudates. At 12.5% water content, glass transition initiated at 48.7C. With increase in water content values, the initiating glass transition temperature decreased. At 19.7% water content, glass transition was observed in the temperature range of 36.9 to 57.3C. Although pasta contains about 13% protein fraction, it did not seem to affect the major part of glass transition range because the pasta proteins become mobile at temperatures greater than 80C and water content greater than 17%.     

A NUMERICAL APPROACH TO COMPUTE TEXTURAL ATTRIBUTES OF COOKED RICE BY EXTRUSION TESTING

The cooked rice extrusion testing system consisted of a piston disc and a sample container with a pot base insert of one outlet. S _init (N/m) and S _max (N/m) are the slopes of the force–deformation curve in the packing and compression stages, respectively, and in the original method they are graphically drawn. Here, however, they were numerically computed as the differential of force to distance. The S _init and S _max from the numerical and drawing methods were compared in terms of data reproducibility and accuracy as described by coefficient of variation (CV) and correlation coefficient (CC), respectively. The numerically computed S _init and S _max showed lower CV: the new method, 0.03–0.06 and 0.03–0.06; the original method, 0.18–0.39 and 0.03–0.14, respectively. S _init by the new method showed higher CC with the adhesiveness of the samples: the new method, − 0.99; the original method, − 0.4. Therefore, the new method proved to be better in data accuracy and reproducibility.

PRACTICAL APPLICATIONS

The extrusion test is a practical instrumental method for measuring the textural properties of cooked rice. Nevertheless, its force–deformation curves are difficult to analyze quantitatively. This study attempted to improve the existing method for curve data analysis by applying a numerical method to compute the instrumental parameters. Based on the findings, this new method provided better data reproducibility and accuracy, and in terms of the instrumental parameters, can facilitate the implementation of cooked rice quality control in the field.     

米质判定器在粮食感官检验方面的应用

通过对粮食辅助检验中观察所用光源、检验平台及平台背景色等因素进行分析、研究和实验,结合相关感官检验方面的有关参数,找出了适合粮食感官检验所需的光源强度、透视方式、适合不同检验项目的平台背景色,研发出适合进行粮食辅助检验用的米质判定器。米质判定器的推广和应用将为提高我国粮食感官检验水平提供有力的技术支持,可以更好的贯彻优质优价、按质论价政策,促进我国粮食标准与国际粮食检验标准接轨。着重介绍了米质判定器的结构、特点和技术指标及其应用。     

酶法改善方便米饭复水性的研究

研究了蛋白酶和纤维素酶对方便米饭复水性的影响,利用胃蛋白酶可使方便米饭复水率由原来的２．６２提高到３．４４。成品不仅具有良好的复水性,且口感,风味均有改善,有与新鲜米饭相似的口味。     

纽代尔/涤纶混纺针织物力学性能研究

为了研究不同混纺比的纽代尔/涤纶混纺针织物的力学性能,对4种纽代尔/涤纶混纺针织物的基本力学性能进行了测试分析.所测试的指标有拉伸、顶破、悬垂性、耐磨性、起毛起球性以及弯曲性能等.通过对试验结果的分析比较,可以得出,随着纽代尔纤维比例的增加,纽代尔/涤纶混纺针织物的断裂强度力、顶破强力逐渐下降;悬垂性能、抗起毛起球性能...     

大豆蛋白改性粘胶纤维力学性能研究

对大豆蛋白改性粘胶纤维作了力学性能的研究与分析.通过对大豆蛋白改性粘胶纤维与普通粘胶纤维作对比, 分别在干态、湿态下测定其强伸性能进而分析其性能.不同加持方式的拉伸试验得出加持方式对纤维性能影响也很大.对大豆蛋白改性粘胶纤维在不同应变下的松弛性能作了一定探讨并采用origin对其拟合分析.