Mechanical strength and rheological behaviour of barley kernels

Basic mechanical and rheological properties (stress relaxation behaviour) of single barley kernels under uni-axial compression were studied. The mechanical properties studied were the modulus of elasticity, yield and ultimate compressive strength, and the modulus of toughness as influenced by the moisture content. The stress relaxation experiments also included the effect of deformation rates and strain levels.
Results indicated that with an increase in moisture content, the strength of the barley kernels decreased while the energy required to cause rupture in the kernel increased initially and then decreased. The stress relaxation behaviour of barley kernels was described by a threeterm Maxwell model with a Maximum Relative Difference (MRD) ≤5%, when compared with one- and two-term Maxwell models. The elastic component (E¹) and relaxation time constant (τ¹) of the first term of the three-term Maxwell model decreased linearly with increase in moisture content. Of the different variables studied, moisture content had a significant influence on both of these parameters.     

Application of computer vision for determining viscoelastic characteristics of date fruits

Date fruits are subjected to different environmental conditions from harvest to consumption. Since the rheological behavior of fruits are important for any processing operation, the viscoelastic characteristics of date fruits were studied at six moisture content, and four temperature levels of product, using a computer vision method. The whole date fruits were subjected to uniaxial compression for relaxing the stress during 300 s. As a new approach, a probe that equipped with a camera was used to measure the samples true contact area simultaneously. Three famous viscoelastic models were used to fit on experimental data. It was found that Generalized Maxwell and Nussinovitch models describe viscoelastic characteristics of date fruits appropriately, as compared to Peleg model. Furthermore, it was observed that moisture content of the product has dominant effect on viscoelastic characteristics of the fruits than temperature.     

Metabolic response to two hydrocooling temperatures in sweet cherries cv Lapins and cv Sunburst

Physiological and metabolic characterisation and analysis of response to two hydrocooling temperatures in cv Sunburst (early season) and cv Lapins (mid‐season) cherries during post‐harvest life has been studied. Samples were hydrocooled with water at 1 °C to reach 6 °C inside the fruit (HC‐6C) and 2 °C (HC‐2C) inside the fruit. After harvesting, Sunburst samples presented higher respiration rates and lower malic acid and sorbitol contents than Lapins. Glucose and fructose contents were similar in the two varieties. Sunburst control exhibited a higher respiration rate than Lapins and a higher rate of conversion from sorbitol to fructose. The change of glucose and malic acid consumption over 4 days at 20 °C was similar for the two varieties. Hydrocooling reduced respiration and the consumption of respiratory substrates. The residual effect of hydrocooling was especially significant in cherries of both varieties that had been pre‐cooled to 2 °C. Hydrocooling delayed loss of skin and pulp firmness, and reduced loss of titratable acid and soluble solid contents over 4 days at 20 °C in both varieties. Hydrocooling to 2 °C checked loss of quality with respect to controls for both varieties after 4 days at 20 °C. Lapins showed better conservation properties than Sunburst under all the experimental storage conditions. Hydrocooling reduced total losses in both varieties, especially in cherries pre‐cooled to 2 °C. Hydrocooling also had several residual effects: reduction of the respiration rate and consumption of respiratory substrates, and slowing of loss of quality, particularly for Lapins. Copyright © 2006 Society of Chemical Industry     

Use of an edible coating containing galbanum gum and cumin essential oil for quality preservation in sweet cherries

Nowadays, the use of natural compounds is considered as an effective strategy for maintaining the quality and heath promoting capacity of fresh products. Changes in quality parameters, main phenolics and antioxidants of sweet cherries in response to coating with a novel bioactive edible coating were studied. Fruit were treated with different concentrations of galbanum gum (GG), cumin essential oil (CEO) and CaCl₂ (CA) and stored at 2 ± 1°C with 90–95% RH for 30 days plus 1 day at ambient condition, and were subjected to quality analysis. All phenolic constituents and antioxidants of fruit juice were substantially decreased during storage in control fruit and a bioactive coating containing 1 or 2% GG + 100 or 200 µL L⁻¹ CEO + 1% CA maintained main fruit phytochemicals including phenolics, phenolic acids, flavonols, anti-stress and antioxidant enzymes activities. The coating significantly (P ≤ 0.01) enhanced fruit total antioxidant activity, flavonoids and ferulic acid contents. The results showed that it is possible to enhance the sweet cherry fruit health-promoting phytochemicals and shelf life by the use of a natural edible coating containing GG and CEO.     

The non-linear viscoelastic behaviour of human hair at moderate extensions

We report the results of experiments carried out on the stress relaxation of slightly stretched human hair. The results show that human hair is viscoelastic, and that when quickly extended to a moderate degree (0.5-6.5%) and held, the force generated will fall to half its original value in about 15 h. However, the relaxation process is also dependent on extension, so that iso-chronous (constant time) data is non-Hookean. We show that the iso-chronous stress/strain behaviour departs from linearity at about 1% extension and the modulus progressively decreases thereafter according to a power-law relationship with strain.     

热黏合土工布应力松弛力学性能预测模型研究

采用四种力学模型对三种不同类型热黏合土工布的应力松弛力学性能进行拟合研究。结果表明,使用力学模型对热黏合土工布的应力松弛进行预测是可行的,广义麦克斯韦变化模型二对三种试样均具有最佳的拟合效果,拟合能力优于欧林模型,显示了良好的品种适应性和预测能力。     

Study of woven fabric shear behaviour

The paper presents the shear frame test with a new method of gripping the fabric sample to describe the shear behaviour of fabrics used in the garment industry under high shear strain conditions (maximum shear angles of 20°). This shear frame test was also used to compare between hysteresis curves given by the Kawabata evaluation system (KES) test, the bias extension test and the shear frame test for 10 woven fabrics. The linear viscoelastic theory was used to analyse the shear relaxation behaviour of the woven fabrics. In addition, in this study, the kernel function of the generalised Maxwell model has been used to describe the viscoelastic properties of the fabrics.     

An improved viscoelastic model for tufted carpet yarn

To overcome the problem that the existing mathematical model cannot characterize the viscoelastic properties of tufted carpet yarn completely and accurately, an improved viscoelastic model is built using the semi-empirical method. Using the test data of creep and stress relaxation, the parameters of the improved model are determined. Through the evaluation of fitting effect, the optimal mechanical model to characterize the viscoelastic properties of tufted carpet yarn is obtained. The results show that compared with the standard linear model, the improved model is more suitable to characterize viscoelastic mechanical properties of tufted carpet yarns, such as the creep and stress relaxation properties, which provides a solid theoretical foundation for analysis of vibration characteristics and dynamic tension control of tufted carpet yarn.     

A viscoelastic model for the compaction of fibrous materials

Fibrous materials experience compression in many important industrial and technical applications. They are known to undergo a viscoelastic response in such circumstances, exhibiting phenomena such as dependence on compaction velocity, stress relaxation and stress–strain hysteresis. In this paper, a model has been developed for the stress in compacting fibrous materials. The model is based on the multiplicative decomposition of the stress into a function of the strain and a second function of the strain‐rate. The model is applicable to that class of materials whose stress–strain responses at different compaction velocities can be collapsed onto a single master curve when the stress is normalised appropriately. The model parameters can be determined using a least‐squares fitting to a select number of test data. The model has been tested for two materials of different architectures over a range of compaction speeds and maximum volume fractions; the match to experimental data is excellent.     

甜樱桃呼吸特性及发酵阈值研究

探明不同温度下密封盒内甜樱桃的呼吸特性和发酵阈值。以‘艳阳’樱桃为试材,采用密闭系统法,研究了不同温度（0、5和20℃）条件下,樱桃包装环境内的气体浓度变化和樱桃的呼吸速率,拟合呼吸速率方程,研究樱桃的发酵阈值。结果表明,密封盒内樱桃的米氏模型参数拟合度较高,各方程决定系数（R²）值均在0.96以上。在0、5和20℃环境下,樱桃果实的最大呼吸速率分别为4.50、7.14和24.39 m L CO₂/（kg·h）,最长贮藏时间分别为156、108和24 h,0℃和5℃环境下的发酵阈值比20℃环境低。综上所述,各温度下密封盒内樱桃的米氏模型参数拟合度较高,低温可以有效地抑制果实的呼吸强度,延长贮藏期。      

保鲜剂对甜樱桃果实贮藏性的影响研究

以红灯等甜樱桃为试材,探讨自制的甜樱桃专用保鲜剂对甜樱桃贮藏保鲜的效果。试验结果表明,该保鲜剂处理在保持甜樱桃果实营养方面有良好的效果,能够有效地抑制果实的褐变,减少果实腐烂。     

甜樱桃常温液藏保鲜的研究

通过常温液藏方法对目前栽培较多的2种甜樱桃品种即红灯樱桃(早熟品种)和那翁樱桃(晚熟品种)进行保鲜试验,结果为:贮存40d后,樱桃果实色泽鲜艳,pH值变化较小,Vc含量的降低显著低于文献报道,两品种间果品质量差异不显著;早熟的红灯樱桃平均果实完好率为61.3%,晚熟的那翁樱桃平均果实完好率达到91.7%,二者间差异显著;常温贮藏液的最佳组合为:可溶性固形物含量30%、pH值3.5、山梨酸钾0.1%、Vc0.1%。     

甜樱桃果实采后病原菌的分离鉴定及其生物学特性研究

为研究危害采后甜樱桃果实的病原菌,以‘拉宾斯’甜樱桃果实为试材,对低温贮藏过程中的病原菌进行分离鉴定,并对其生物学特性进行初步研究。根据病原菌形态学特征和18S r DNA序列分析结果将2个病原菌鉴定为子囊菌亚门锤舌菌纲柔膜菌目核盘菌科核盘菌(Sclerotinia sclerotiorum)和子囊菌亚门粪壳菌纲肉座菌亚纲肉座菌目生赤壳科螺旋聚孢霉属(Clonostachys sp.)。核盘菌菌丝在以牛肉膏为氮源的SDA培养基、20℃、p H=5.0及黑暗条件下生长最好,产孢量最佳条件为以乳糖为碳源,牛肉膏为氮源的SDA培养基,30℃、p H=7.0,黑暗环境;螺旋聚孢霉菌丝在以硝酸钾为氮源的SDA培养基、30℃、p H=6.0及光照条件下生长最好,产孢量最佳条件为20℃、p H=6.0,光照培养。      

乳酸链球菌素和柠檬酸对甜樱桃中沙门氏菌的抑制

为了研究沙门氏菌污染采后甜樱桃果实的生长繁殖状况及其控制情况,分别采用乳酸链球菌素(Nisin)、柠檬酸及二者复配溶液处理人工接种沙门氏菌的甜樱桃,观察和分析Nisin和柠檬酸的抑菌效果。结果表明,Nisin与柠檬酸处理均具有抑菌效果,并且随着溶液中Nisin从10μg/m L上升至100μg/m L、柠檬酸从1 g/L上升至5 g/L时,抑菌效果显著增强,(p<0.05)。研究还发现,Nisin溶液100μg/m L、柠檬酸溶液5 g/L、Nisin 10μg/m L与3 g/L柠檬酸复配溶液和Nisin 50μg/m L与柠檬酸1 g/L复配溶液这4种处理具有相似的抑菌除菌效果,处理5 min菌落浓度可以降低至104cfu/m L;Nisin 50μg/m L与3 g/L柠檬酸复配溶液处理样品15 min时,沙门氏菌的菌落降至检测限以下,无法检出;当贮存时间一直延长至第10 d时,Nisin和柠檬酸处理仍然保持一定的抑菌效果,充分除菌抑菌。      

气调贮藏对甜樱桃果实采后生理生化变化的影响

主要研究了甜樱桃品种\     

甜樱桃采后表皮蜡质形态及相关性质变化规律

[目的]揭示不同品种甜樱桃耐贮性差异的原因,为其采后涂膜保鲜提供理论支持和技术指导。[方法]选取4个具有代表性的甜樱桃品种（红灯、雷尼、红玛瑙、友谊）作为研究对象,对采收时不同品种甜樱桃果皮蜡质的形态、果皮对不同溶液的接触角以及红玛瑙樱桃在贮藏期间表皮蜡质形态、接触角、临界表面张力的变化进行了探究。[结果]4个品种甜樱桃在采收时表皮的蜡质分布和形态均存在差异,表皮对于同一种溶液的接触角存在显著差异;红玛瑙樱桃表皮蜡质在贮藏期间呈减少趋势;由于甜樱桃表皮的疏水性,在配制涂膜液时,向其中添加0.1%的吐温-20作为表面活性剂可显著提高涂膜液在其表面的润湿性;红玛瑙樱桃贮藏期间表皮对去离子水的接触角呈下降趋势,并且其临界表面张力随贮藏时间的延长不断升高。[结论]不同品种甜樱桃耐贮性的差异可能与其表皮特性相关联,在涂膜保鲜液中添加0.1%的吐温-20可使涂膜液更均匀地涂覆在甜樱桃表面。