Rehydration and sorption properties of osmotically pretreated freeze-dried strawberries

The aim of this work was to investigate the influence of osmotic dehydration and type of osmotic solution on selected physical properties of freeze-dried strawberries. Frozen Senga Sengana strawberries were dehydrated in osmotic solution with water activity of about 0.9 (sucrose and glucose solutions and starch syrup). Osmotically dehydrated fruits were frozen and freeze-dried at heating shelf temperature of 30 °C for 24 h.     

Use of pectinmethylesterase and calcium in osmotic dehydration and osmodehydrofreezing of strawberries

Strawberry samples of two varieties (Camarosa and Elsanta) were dehydrated using different osmotic solutions (60% glucose, fructose, sucrose and raftilose) and subsequently frozen by rapid and high-pressure shift freezing (HPSF). The effect of pectinmethylesterase (PME) and calcium (Ca⁺⁺) added to the osmotic solutions on several compositional parameters and the textural/structural quality of dehydrated and osmodehydrofrozen-then-thawed samples was studied. Due to the presence of PME and Ca⁺⁺ in the osmotic solutions, weight reduction upon dehydration was slightly decreased, which was correlated to a small positive effect on the net uptake of sugars and depression of the initial freezing point. Except for the Camarosa samples treated with sucrose, PME and Ca⁺⁺ in osmotic sugar solutions positively affected the relative hardness of dehydrated fruits, which was ascribed to the effect of PME and Ca⁺⁺ on the cell wall strength of the tissue. No cell wall damage and tissue particle alterations were observed upon dehydration. The effect of osmotic dehydration (OD) using different sugar solutions without PME and Ca⁺⁺ on the texture and structure of frozen-then-thawed samples was limited and sometimes negative. The added PME and Ca⁺⁺ however positively influenced the volume and shape of the thawed samples, which could be related to slightly higher relative hardness values and, for the Elsanta strawberry fruits, also to the reduced (up to 81%) drip loss upon thawing. Upon freezing the dehydrated fruits, no cell wall disruption was observed. Tissue distortion caused by freezing and indicated by a decrease in particle size, convexity and roundness, was compensated by the use of PME and Ca⁺⁺ during OD.     

不同小分子糖渗透草莓的传质动力学及对真空冷冻干燥草莓品质的影响

为系统地了解不同小分子糖特别是低聚糖和糖醇对草莓的渗透行为以及不同小分子糖对真空冷冻干燥草莓品质的影响,本研究利用两种数学模型对10 种常见小分子糖（白利度为40 °Brix）的渗透动力学进行拟合,并进一步对渗糖处理后真空冷冻干燥草莓的理化特性进行表征。结果表明,Weibull模型更适用于描述渗糖处理后草莓的可溶性固形物增量（solid gain,SG）,而Peleg模型可以更好地描述草莓的水分去除量（water loss,WL）。经不同糖渗透处理结束后,草莓的SG差异较大,山梨糖醇可以使草莓的SG达到6.84 g/100 g,是低聚异麦芽糖的6.16 倍。此外,渗糖处理的草莓硬度得到普遍提高（94.58%～223.23%）;葡萄糖、果糖、山梨糖醇渗透处理组的脆度分别降低了16.70%、20.74%、41.45%,低聚果糖渗透处理后的草莓质构特性与蔗糖最为接近。综合考虑渗透效率、感官营养品质和生产成本,低聚果糖是蔗糖在果蔬渗透处理方面的一种潜在替代品。     

Antioxidant Activities and Polyphenolic Properties of Raw and Osmotically Dehydrated Dried Mushroom (Agaricus bisporous) Snack Food

Total polyphenolics and free radical scavenging properties of extracts obtained from osmotically dehydrated, and spiced mushroom snack food with raw unprocessed mushrooms were studied. Sensorially acceptable mushroom snack was prepared in the laboratory by osmotically dehydrating Agaricus bisporous in 5% salt solution followed by addition of an adequate combination of spices and vacuum drying. The extracts of raw and dry snack-mushrooms were then evaluated for their scavenging activities against the 2,2-diphenyl-1-picryhydrazyl (DPPH) free radical and 2,2-azobis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS). The scavenging activity of free extracts of raw and dry snack mushrooms on DPPH radical were 76% and 72%, respectively. The ABTS radical scavenging activity of the free extracts of raw sample expressed as ascorbic acid equivalent antioxidant activity (AEAC) was 2.76 mg ascorbic acid equivalents/100 g and 2.67 mg ascorbic acid equivalents/100 g snack mushroom. Both free and bound polyphenolic contents in mushroom snacks were slightly higher than raw mushrooms whereas total flavonoids levels decreased marginally. No change in antioxidants status of the dry snack product was observed when dry snack stored at ambient temperature for up to 15 days. The results of this study suggested that mushroom snacks prepared using a combination of the above methods was able to retain a significant amount of antioxidants, phenols and flavonoids and mushroom snacks may prove to be an alternative nutritious snack.     

Methodological Aspects of Determining Apple Mechanical Properties During Impact

The influence of cylindrical sizes of samples and velocity of impact on its course and strength parameters for the “Braeburn” variety apples was studied. Three sample lengths of 17, 19, and 21 mm, three diameters of 10, 15, and 20 mm and four impact velocities of 0.25, 0.5, 0.75, and 1 ms^–1 were applied. Failure stress and strain, impact energy, absorbed energy as well as tissue stiffness and toughness were determined as dependent variables. The influence of the sample diameter on maximum force response, impact energy, absorbed energy, and tissue stiffness was studied. The other independent variables: Sample length and impact velocity did not show significant influence on the strength parameters of the apple tissue. The shock wave speed in the apple tissue was independent of both sample sizes and impact velocity. Its mean value amounted to 292 ms^–1. Under the experimental conditions the mean value of the absorbed energy contribution to the impact energy amounted to 9.9%. The experiment confirmed importance of a critical stress criterion as regards cylindrical samples of apples under impact conditions.     

Influence of osmotic pre-treatment and microwave application on properties of air dried strawberry related to structural changes

Strawberry halves, with and without osmotic pre-treatment, were dried at 40 °C air temperature, with and without microwave application (0.2 W/g). Changes in volume, pectic fractions, mechanical behaviour and glass transition temperature due to dehydration treatments were evaluated. Microwave application resulted in an increased water soluble pectic fraction as a consequence of both protopectin and oxalate soluble pectic fraction reductions. This solubilisation leads us to obtain dried samples with a more rigid, firmer structure which, indeed, showed greater glass transition temperature values. Nevertheless, these samples are softer when rehydrated, thus indicating a greater structural damage. The sugar presence induced by an osmotic dehydration pre-treatment seems to reinforce the solid cellular matrix, which is evident from the mechanical behaviour of rehydrated samples. So, the greatest structural damage caused by microwaves may be reduced by an osmotic dehydration pre-treatment.     

复合纱强伸性能的探讨

通过两组分相互合并复合纱的拉伸性能的研究，找出了决定复合纱断裂强力和断裂伸长率的主要因素，并建立了复合纱大变形和小变形下的力学模型。     

The Effect of Seed Size and Microstructure on Their Mechanical Properties and Frictional Behavior

The seeds of grass pea were selected based on their size, hardness, and microstructure in order to examine their mechanical properties and friction coefficients versus mass. The size, shape, mass, and static friction coefficients of seeds were determined using adequate methods. Seed hardness was measured using compression methods, and it was described by typical and corrected fracture parameters. The microstructure of cotyledons and seed surfaces was viewed using scanning electron microscopy, and surface microimages were processed by digital image analysis. The length of the examined seeds ranged from 5.86 mm to 14.25 mm, their width ranged from 5.47 mm to 12.93 mm, thickness from 4.59 mm to 6.21 mm, mass from 0.110 g to 0.570 g, projected area from 28.55 mm² to 148.73 mm², and roundness from 1.060 to 1.126. The static friction coefficients for seeds of the examined accessions and varieties determined on steel, wood, rubber, and PVC surfaces were 23.4–33.3°, 24.4–37.2°, 29.6–50.4°, and 22.4–35.4°, respectively. For grass pea seeds of irregular size and shape, corrected fracture energy values (with regard to seed mass and volume) were proposed as a more robust parameter of seed hardness. The values of the static friction coefficient depend on both seed mass and the microstructural properties of seed surface digitalized with the involvement of image analysis techniques.     

Mechanical Properties of Pear as a Function of Location and Orientation

Abstract

This study provides data on the fundamental mechanical properties of pear tissue and its relationship with specimen orientation and location. The compression tests were performed on Dangshan pear using the Instron Universal Testing Machine. The values of failure stress, failure strain, failure energy, and Young's modulus on the specimen orientation and location in pear were obtained. The four mechanical properties are significantly affected by specimen orientation, latitude, and depth, but not affected by the longitude of the specimen.     

Drying kinetics of nopal (Opuntia ficus-indica) using three different methods and their effect on their mechanical properties

Nopal (Opuntia ficus-indica) is an endemic plant of the arid and semiarid lands of America. Preservation problems are associated with nopal utilization and processing, so a practical alternative is dehydration. This work deals with the drying of nopal correlated with the textural properties of the dried product. Convective drying studies were performed and the most representative experimental results at two air flow rates (3 and 5 m/s) and two air temperatures (45 and 65 °C) are displayed here. Experiments of osmotic drying with glucose at 40 and 60 °Brix, and drying temperatures of 25 and 45 °C were tested. A combination of both drying processes was also performed. Results have shown forced convection drying with a mostly decreasing trend at the constant rate period. In the osmotic drying, moisture loss was associated to glucose concentration. Texture profile analysis of dehydrated nopal suggested that samples undergoing convective drying have more cohesiveness than samples treated solely by osmotic drying. On the other hand, samples treated by osmotic drying became more elastic. Between the two drying methods studied, the convective drying has shown the best results at the experimental conditions assayed.     

绉纹整理对真丝织物机械性能的影响

对绉纹整理整理前后的真丝电力纺机械性能进行了较全面的测试。结果表明：整理后织物的变形能力、弹性、湿态折皱弹必玫耐疲劳性能明显提高，丝线强力降低；织物强力随着经纬密度增幅大小的不同，而呈现出增高或降低两种相反的变化趋势。整理后耐磨性增强，但较容易出现局部集中磨损现象。     

浅谈铌元素对钢丝力学性能的影响

８０Ｎｂ盘条拉拔对比试验结果表明，微量元素铌对钢丝的力学性能有明显影响，在增加强度的同时，韧性也提高。     

竹原纤维结构和力学性能研究

文章主要研究了竹原纤维的基本形态特征;同时对竹原纤维的力学性能特点作了详细分析.     

Effect of Plasticizers on Mechanical and Barrier Properties of Rice Starch Film

The effect of plasticizers, glycerol, sorbitol and poly(ethylene glycol) 400 (PEG 400), on mechanical and barrier properties of rice starch film has been investigated. Sorbitol‐ and glycerol‐plasticized starch films appeared homogeneous, clear, smooth, and contained less insoluble particles compared to unplasticized rice starch films. PEG 400 did not form plasticized films of suitable characteristics. The softness and stickiness of films improved with increasing concentrations of glycerol and sorbitol. In general, films plasticized with glycerol and sorbitol displayed a better solubility in water than unplasticized films, i.e. 35% (w/w) glycerol and 45% w/w (sorbitol) (optimum solubility). The tensile strength of films decreased especially in the high concentration regime of plasticizers, between 20–45% (w/w) of plasticizer/rice starch film. Through the entire concentration regime, the tensile strength of glycerol‐plasticized films was significantly lower than that of sorbitol‐plasticized films, but their elongation was larger. The water vapor transmission rate (WVTR) through plasticized films and the oxygen transmission rate (OTR) increased with glycerol and sorbitol concentrations, however, glycerol was revealed to be significantly more effective in reducing the tensile strength as well as increasing the WVTR and the OTR compared to sorbitol. With the higher tensile strength and the smaller OTR and WVTR, the 30% sorbitol‐plasticized film reveals an improved coating performance in terms of a reduction of coating failures.     

储存条件对聚丙烯纺粘法非织造布力学性能的影响

通过拉伸试验探讨了储存条件(环境、时间)对聚丙烯纺粘法非织造布产品力学性能的影响，并且分析了形成这些影响的原因。     

Moisture Dependent Geometric and Mechanical Properties of Wild Pistachio (Pistacia vera L.) Nut and Kernel

In this research, wild pistachio (Pistacia vera L.) nuts and kernels were analyzed for selected geometric properties and mechanical behavior under compression loading. The average length, width and thickness arithmetic and geometric mean diameter of wild pistachio nuts at 5.83% w.b. were 13.98, 8.76, 7.25, 9.93, and 9.75 mm, while the corresponding values of kernels at 6.03% w.b. moisture content were 11.07, 5.92, 4.83, 7.21, and 6.88 mm, respectively. As the moisture content of pistachio nut increased from 5.83 to 30.73% w.b., the bulk density, apparent density and terminal velocity were found to increase from 521 to 543 kgm^?3, 809 to 829 kgm^?3, and 5.51 to 6.29 ms^?1, respectively, whereas porosity decreased from 35.14% to 34.63%. The results revealed that wild pistachio nut required higher rupture force and energy to crack wild pistachio nuts for compression along the L-axis as compared to other two axes.     

针织复合材料人工气管的开发及力学性能研究

介绍了一种新型的针织结构复合材料人工气管支架的原料、编织与涂层方法；对其拉伸和压缩等机械性能进行了初步研究，并和成年大气管的力学性能进行了对比，证实了力学上的可行性。     

Mechanical Properties of Melon Measured by Compression,Shear, and Cutting Modes

Mechanical properties of three common varieties of melon were measured. These are toughness, rupture force, shear strength, maximum shearing force, and cutting force. The role of peel (%) on each property was also calculated as the relative contribution of peel to unpeeled produce. The shear strength of peel was statistically found similar (p > 0.05) for all varieties. The same result was also revealed for unpeeled produce. Using rupture force was not recommended for peeling watermelon, because of close values of this property for its peel and unpeeled case. The required energy for peeling all three varieties of melon was determined to be 500 N mm. Peeling melons using cutter tools could not be recommended.     

Physicochemical,Water Vapor Barrier and Mechanical Properties of Corn Starch and Chitosan Composite Films

Biodegradable flexible films were developed from corn starch (CS) and chitosan (CH); their microstructure, mechanical and barrier properties were evaluated. Chitosan and starch blend filmogenic suspensions showed a pseudoplastic behavior, similar to that of chitosan solutions. Smooth surfaces, homogeneous and compact film structures were observed from microstructure studies using scanning electron microscopy (SEM). The addition of glycerol reduced film opacity and increased film solubility of both CS and composite CS‐CH films. Water vapor permeability values of composite CS‐CH films plasticized with glycerol ranged between 3.76 and 4.54× 10⁻¹¹ g s⁻¹ m⁻¹ Pa⁻¹, lower than those of the single component films. CS‐CH films were resistant and their flexibility increased with glycerol addition. Tensile strength values of CS‐CH films were comparable to those of low‐density and high‐density polyethylenes but lower than that obtained for cellophane, however, composite biodegradable films showed lower elongation at break values than the synthetic commercial ones. In conclusion, CS‐CH films can be described as biofilms with a homogeneous matrix, stable structure and interesting water barrier and mechanical properties, with great possibilities of utilization, and with the advantage of biodegradability.