机械损伤对富士苹果酶促褐变的影响

研究了富士苹果机械损伤后在5℃和18℃贮藏条件下对生理变化及酶活性的影响.结果表明,机械损伤后的果实相对电导率急剧增大、L*值迅速下降、多酚含量逐渐降低、丙二醛(MDA)含量逐渐上升,果肉快速发生褐变.机械损伤提高了多酚氧化酶(PPO)、过氧化物酶(POD)和过氧化氢酶(CAT)的活性,抑制了超氧化物歧化酶(SOD)的活性.随着贮藏时间的延长,除了PPO外,其它指标都呈现了上升、下降的反复过程,说明组织自身的保护酶系统对伤胁迫具有生理防御作用,而且在低温贮藏时酶活性较强而能有效地延缓果实的衰老.     

Influence of Ultrasound on Freezing Rate of Immersion-frozen Apples

The use of power ultrasound within the food industry is an innovative subject. Application of sound to monitor a process or product is common, e.g. in quality assurance. However, the use of ultrasound to directly improve processes and products is less popular in food manufacturing. In the present work, ultrasound-assisted immersion freezing was investigated on apple samples. Because the apple parenchyma is mechanically anisotropic, the influence of applying ultrasound on radial or tangential orientated samples was also examined. Apple cylinders were immersed in an ultrasonic bath system, which operates at 40 kHz frequency. Experiments were carried out at a power level of 131.3 W (0.23 W/cm²), and ultrasound was applied intermittently for different times from temperatures below and close to the initial freezing point. Results showed that ultrasound application at 0°C or −1°C for 120 s in total, with 30 s intervals, significantly improved the freezing rate represented by the characteristic freezing time up to 8% (P < 0.05), compared to immersion freezing without ultrasound. Results of the effect of ultrasound waves applied on radial or tangential cut samples sonicated for 120 s from −1°C and/or 0°C indicated that at the power level considered there were no significant differences among the ultrasonic radial or tangential irradiated samples of these treatments, though the freezing rates were enhanced and different (P < 0.05) from the control treatment. Some evidence of the influence of ultrasound to induce primary nucleation was also observed.     

轮轨接触面损伤时冲击力作用下热弹塑性分析

轮轨接触面发生剥离断裂等损伤时轮轨冲击力是无损伤时的数倍,不同损伤,不同速度,不同环境温度,轮轨冲击区域温度不同。由于轮轨损伤而产生的极大的轮轨冲击力导致损伤部位应力应变极大,损伤部位温度升高,损伤附近更容易发生较大的弹/塑性变形,使损伤发生扩展。     

二氧化氯对榨汁苹果表面腐生酵母菌杀菌规律的研究

应用中心组合实验设计方法(Central Composite Design)研究了二氧化氯对榨汁苹果原料表面的腐生酵母的杀菌规律。通过回归分析，用数学模型的方式表示了二氧化氯对苹果表面腐生酵母菌的杀菌规律，指出了几个主要影响因素：作用浓度、杀菌时间、杀菌液值和灭菌温度与杀菌效果的之间的关系。通过对得出的数学模型的验证，证明该方程可以用于描述二氧化氯对腐生酵母的杀菌规律，并可对杀菌效果进行较准确的预测。     

Temperature Effects on Food Contact Surface Properties

Measurable contact surface properties related to surface energy have been suggested to provide direction for prediction and control of fluid food behavior at interfaces. With respect to fouling of heat exchangers, such properties may be useful for development of mathematical models which incorporate surface-related terms. Surface energy parameters for a variety of contact surfaces were recorded at temperatures from 7 to 80°C. A linear dependence was observed between surface energy properties and temperature. This suggests a need to account for temperature influences on surface energy in further development of models which describe surface interactions undergone by food components at temperatures outside of the ambient range.     

Surface Gloss Evaluation of Apples Based on Computer Vision and Support Vector Machine Method

This paper investigates computer vision applications for surface gloss evaluation to determine a quick surface gloss evaluation method for apples. “Red Fuji” apples were wax-coated with different concentrations of shellac solutions to obtain the apple samples with different levels of surface gloss. The surface gloss values and the color scales of the apple samples were detected using a pinhole gloss meter and a color meter. The apple sample images were captured and processed, and the color parameters of the high light areas were extracted. Support vector machine (SVM) regression and classification models were built to predict the surface gloss values and the surface gloss levels of apples, respectively. The results showed that to predict the surface gloss of apple samples, the correlation coefficients of the SVM regression model were 0.94 and 0.90 for the training and the testing groups, respectively. The classification accuracy rates of the SVM classification model for the training and the testing groups were 100 and 96.7%, respectively. Finally, apple surface gloss level classification software was developed, which showed good operating results for both classification accuracy rates and calculation speed. This paper provided a new surface gloss evaluation method based on computer vision for apples.     

砂光机砂光辊剩余不平衡量对振动影响的分析

通过分析砂光机砂光辊剩余不平衡量对振动的影响,给出了砂光辊剩余不平衡量与振动的关系式。为设计、生产制造砂光辊提出合理经济的剩余不平衡量提供理论依据。     

加脂对成革机械性能影响

加脂是制革过程中的一个重要工序,对成革的物理机械性能有重要影响。本文讨论了加脂对成革抗张强度和撕裂强度的影响,概述了不同成革要求应用不同的加脂剂和加脂方法。     

Impact of Mechanical Shear on the Survival of Listeria monocytogenes on Surfaces

Abstract: The impact of mechanical surface shear on microbial viability is rarely a subject for exploration in food processing. The objective of this research was to investigate the impact of mechanical shear on the survival of Listeria monocytogenes on surfaces. Mechanical shear created by slicing a model food was explored to investigate the viability of L. monocytogenes. Cell injury/death was readily demonstrated in fluorescence images by confocal microscopy in which the live and dead cells were fluorescently stained green and red, respectively, with a viability dye kit. Images showed that a large percentage of dead cells appeared after slicing, and they were readily transferred from the slicer blade onto the surfaces of sliced agar, indicating that surface shear may cause the lethal effect on L. monocytogenes. Surface transfer results also showed that viable cell counts on agar slices (in a slicing series) followed a consistently decreasing pattern. The cell counts initially at 5 to 6.5 log CFU/slice (slices 1 to 6), decreased to 3 to 4 log CFU/slice (slices 8 to 30), then to 2 to 3 log CFU/slice (slices 31 to 40), and counts would be expected to further decrease if slicing continued. The overall cell recovery (survival) ratio was about 2% to 3% compared to the initial 8.4 log CFU/blade on a 10 cm² edge area. The impact of shear on microbial viability during slicing may contribute 99% of viable cell count reduction. This study provides clear evidence that surface shear can kill foodborne pathogens and reduce cross-contamination. The lethal effects of surface shear may further enhance food safety.     

盘磨机比接触面积负荷磨浆强度理论的研究

从磨齿边缘长度出发,依据盘磨机的磨浆机理,将磨齿接触面积引入磨浆强度的研究中。结合影响磨浆质量的磨齿主要参数如齿宽、槽宽、磨齿倾角、磨盘内径及磨盘外径等,在磨浆强度理论研究基础上,推导了比接触面积负荷（specific contact surface load,SCSL）的磨浆强度理论,并通过7个不同齿宽、槽宽、磨齿边缘长度及转速的磨盘对漂白针叶木浆进行低浓打浆实验,验证了SCSL的正确性。研究结论不仅在一定程度上改进了现有磨浆强度理论,而且也可为盘磨机磨盘选型和齿形设计提供指导。     

基于接触角法表征纺织品表面润湿性应用研究

纺织品在日常使用中会接触到各类液体,表面润湿性是其表面性质的重要特征之一,是与其实际使用要求密切相关的一项性能。本文重点详述了纺织品表面润湿性的现象和原理,接触角试验方法,接触角在纺织品表面润湿性中的应用及研究状况。     

Mechanical Models of Compression and Impact on Fresh Fruits

Well‐designed and well‐operated postharvest mechanical handling processes are vital if fresh fruits are to enter markets with minimal damage. The susceptibility of fruit to quality loss during handling is largely determined by mechanical contact and damage. This article reviews current understanding concerning the effect of impact and other mechanical contacts on fruits. It also discusses the major mechanical models that represent the interaction between fruits or a fruit and a surface. In total, 25 mechanical models associated with compression and impact behaviors of fresh fruits, mainly characterizing such behavior between 2 deformable spherical bodies and between a deformable spherical body and a rigid plate are reviewed. Finally, possible future research directions are discussed. The main challenge in fruit handling is to recognize and prevent microscopic damage to fruits, especially internal tissue/cell damage and microcracks resulting from multiple/repetitive impacts and compressions.     

On Surface Characterization of Materials Targeted for Food Contact

A measurable parameter related to solid surface energy has recently been suggested to provide an index of contact material interactability with components of fluid food. Employing contact angle methods, two series of aqueous solutions were used to evaluate this parameter for a variety of food contact surfaces. Results were independent of which series of diagnostic liquid was used. This supports the identity of the parameter as a true surface property, unique for a given material, and related to the polar character of its surface. Direction is provided toward a means for contact surface characterization which may aid the development and use of models describing food particle behavior at interfaces.     

Influence of Lees Contact on Evolution of Amines in Chardonnay Wine

ABSTRACT:  Some white wines of Chardonnay variety are aged on their lees in oak barrels over several months. Over this period, autolysis takes place and different compounds are freed in the wine, among them, nitrogen compounds. The aim of this work was to study the evolution of amines in Chardonnay wine during 180 d of maturation on lees, with and without weekly stirring. The process was carried out in new French oak barrels with 225 L capacity. From the results obtained it was found that weekly stirring mainly had an influence on histamine and tyramine concentration. The concentration of these amines at the end of the aging period was higher in the wine with weekly stirring. This treatment showed no effect on the amine concentration at the beginning of the wine aging on lees. The aging time also had an influence on the concentration of amines in the Chardonnay wine.     

小麦机械通风各向异性阻力的数值模拟研究

机械通风是实现安全储粮、保证粮食品质的主要措施。以小麦为研究对象,采用计算流体动力学(computational fluid dynamics,CFD)的方法对大型平房仓小麦的横向通风、压入和吸出式竖向通风阻力进行了数值模拟,通过对不同通风方式下粮堆的阻力的分析发现,粮层阻力与风量成正比,风量越大,粮层阻力越大;通风方式不同,单位粮层阻力也不相同,小麦下行通风的单位粮层阻力最大,上行通风次之,横向通风最小。通过对小麦粮种各向异性阻力的分析,为以后不同粮种机械通风系统的分析奠定基础。     

鲜切苹果品质保持研究

文研究了不同褐变抑制剂对鲜切苹果PPO活性、褐变度、感官品质的影响。试验结果表明:单一的1.5%L-半胱氨酸、1.0%D-异VC钠、1.0%谷胱甘肽处理均能较好地抑制鲜切苹果褐变。采用0.10%D-异VC钠+0.12%谷胱甘肽+0.13%L-半胱氨酸,浸泡2min的复合处理,可使鲜切苹果的PPO活性、褐变度、感官品质在14d内保持较优水平。     

食品成分对淀粉凝胶力学性能的影响

淀粉凝胶的力学性能因糖、无机盐、酸碱、单甘酯等的加入用来改善食品风味和口感的物质而发生变化。这种变化是由于添加物质与淀粉大分子发生作用或是添加物质对淀粉大分子之间的相互作用的产生影响造成的。该研究结果对于生产既具有一定风味又不失良好力学性能的淀粉凝胶类产品提供了必要的依据。     

Mechanical Behavior Under Tension of Schoenoplectus californicus Fiber

In the Andeans, it is common to find homemade containers, chairs, structures made with Schoenoplectus californicus sub. californicus, commonly known as totora. Popularly is known that the homemade products possess resistance and durability due to the incorporation of this fiber, although nowadays the mechanic properties of this material are unknown. This research begins with the study of the variety of the totora which is present in the Province of Imbabura, Ecuador. Considering the geometrical variation of the stem, it is divided in three parts. Based on standard ASTM D4761-02a totora is characterized under tension. Finally, the mechanic characteristics under tension of Schoenoplectus californicus are presented from the stress-strain curve and its comparative analysis among the groups of transversal sections. It is determined that its behavior corresponds to a fragile material with an average of maximum stress up to 88.501 6.92 MPa, and an average of a maximum strain of 0.05132 0.00610 mm/mm.