Mechanical behavior of pistachio nut and its kernel under compression loading

Some mechanical properties of five varieties of Iranian pistachio nut and its kernel (namely; Akbari, Badami, Kalle-Ghuchi, Momtaz and O’hadi) were determined. These properties include rupture force, deformation and rupture energy. Samples at various moisture contents were compressed along the X-, Y- and Z-axes. The X-axis was considered the loading axis through the length dimension, while the Y-axis was the transverse axis containing the minor dimension (width) at right angles to the X-axis, and Z-axis was assumed the transverse axis containing the minimum dimension (thickness). The results showed that rupture force, deformation and rupture energy values decrease with increasing moisture content. The maximum rupture force, deformation and rupture energy values at all moisture levels as well as for all varieties were obtained for pistachio nut loaded along the X-axis. Compression along the Y-axis required less compressive force among the other two compression axes to extract the kernels.     

Instrumental measurement of pomegranate texture during four maturity stages

Texture of pomegranate fruit and arils are the main quality attributes in the food process industries. In this study, the texture properties of pomegranate fruit and arils (cv. “Ashraf”) at four different stage of maturity (88, 109, 124, and 143 days after full bloom) were evaluated using the puncture test (rupture force and rupture energy) and compression test (bioyield force, rupture energy, and young modulus). The tests showed that all studied textural parameters were sensitive textural parameters for distinguishing the maturity stages. Rupture force and rupture energy of pomegranate fruit were determined at top, middle, and bottom positions of the fruit. The results showed that compression load values of aril increased with advances in maturity stage of fruit, while puncture load values of fruit decreased. The textural properties of pomegranate fruit and arils exhibited a strong dependence (p < .05) on the degree of maturity at harvesting time. Also results showed that rupture force of three different studied positions of fruit was severely different. The highest and lowest values were observed at top and middle position, respectively.     

The Effects of Moisture Content, Compression Speeds, and Axes on Mechanical Properties of Walnut Cultivars

In this study, the mechanical properties of walnut (Juglans regia L.) cultivars were investigated as a function of moisture content. The experiments were carried out at three moisture contents, compression speeds (0.5, 1, and 1.5 mm/s), and compression axes (X-, Y-, and Z-axes). The highest rupture force and rupture power in all moisture contents were obtained for walnut cultivars loaded along the Y-axis. Rupture force, rupture energy, and rupture power of walnuts decreased in magnitude with an increase of moisture content, while rupture force, specific deformation, rupture energy, and rupture power increased with an increase of compression speeds. The highest rupture force was obtained with load along the Y-axis as 410.4 N and 394.3 N and also the highest rupture force was recorded at 1.5 mm/s compression speed as 260.7 N and 377.1 N for Yalova-1 and Yalova-3 cultivars, respectively. A linear force decrease was observed from 320.5 N to 196.4 N and from 492.7 N to 247.1 N with increasing moisture content from 11.46% to 23.16% and from 11.25% to 19.47% for Yalova-1 and Yalova-3, respectively. The highest rupture force, specific deformation, rupture energy, and rupture power were obtained at 1.5 mm/s compression speed, while the lowest rupture force was obtained at 0.5 mm/s compression speed for walnut cultivars. The lower rupture force and rupture power were obtained with load along Z-axis for Yalova-1 and Yalova-3 walnut cultivars. The results revealed that the higher compression speed and Z-axis could be recommended for cracking of shelled walnuts.     

花生脱壳力学特性的实验研究

利用微机控制的电子拉压实验机对川西地区花生进行施压的力学实验。并以花生破损力为目标参数,以施压方向、施压速率、含水率为因素进行三因素三水平有重复观测值的正交试验。结果表明：花生壳厚沿不同部位均匀分布;花生在被压缩时,均会经过弹性变形、塑性变形和突然破裂3 个阶段;花生施压方向、施压速率、花生含水率对花生破损力都有极显著影响,并得到不同方向在弹性范围内的花生壳压缩与变形的回归方程,提出花生脱壳的最佳参数组合为花生施压力方向为顶面(x 向)、施压速率为30mm/min、含水率15.8%。     

Mechanical Behavior of Lentil Seeds in Relation to their Physicochemical and Microstructural Characteristics

The mechanical characteristics (rupture force, maximal deformation, and rupture energy) of red and green lentils under compression loading were determined as a function of moisture content ranging from 9.5 to 21.1% (w.b.). Scanning electron microscopy, laser diffraction particle size analysis, and instrumental texture evaluation were successfully applied to relate the microstructure and texture of different lentil seed varieties. Results demonstrated that all of the mechanical parameters of the green lentils, which have smaller starch granules, were significantly (p < 0.05) higher than those of the red lentils. At a loading rate of 4 mm min^?1, the force required for initiating seed rupture decreased with an increase in moisture content, for vertical and horizontal orientations (p < 0.05). The scanning electron microscopy observations also revealed that seeds were more flexible in a horizontal orientation.     

PENDULUM TEST FOR EVALUATION OF THE RUPTURE STRENGTH OF SEED PODS

A small impact pendulum was developed to measure the shatter resistance of seed pods. While clamped by their stems, the pods are hit by the rigid pendulum; the rupture energy is derived from the measured angles of swing. The consistency of the pendulum was confirmed by tests on a sample of fine spring wire. The pendulum was then used in a series of trials on 13 rapeseed varieties and rupture energy results were compared with earlier bending moment and bending energy results obtained from tests using a quasi-static cantilever arrangement. Rupture energy values were much less variable than bending energy. However, the ranking of varieties by all three strength measures was generally similar.     

Effects of moisture content and compression axis on mechanical properties of Shea kernel

Some mechanical properties of Shea kernel were investigated in this study. The kernels were divided into two categories sizes namely: small size kernel (SSK) and large size kernel (LSK) and the properties investigated were: rupture force, deformation at rupture and energy consumed at rupture. The tests were carried out at a deformation rate of 50 mm/min and four moisture content levels of 25.9%, 11.60%, 6.88%, 4.98% (db) for SSK and 11.19%, 6.21%, 5.78% and 2.77% (db) for LSK. The variations in these properties were observed considering the effects of moisture content and compression axes on them as the kernels were air-dried. Sample kernels were compressed along the orthogonal axes corresponding to major axes (length), intermediate axes (width) and minor axes (thickness) of Shea kernel. Some physical characteristics of Shea kernel such as dimensions, geometric mean diameter and mass were also evaluated. Results showed that generally, rupture force, deformation and energy at rupture decreased as moisture content decreased. The regression models that best fitted the relationships were polynomial functions of the second order. The highest and lowest forces for Shea kernel to rupture were those through the minor axis (thickness) and major axis (length) respectively. These properties are often required for the design of transportation, storage and grading/sorting machines and other post harvest machines for Shea kernel.     

Instrumental Texture Analysis Parameters as Winegrapes Varietal Markers and Ripeness Predictors

The texture parameters of three red grape varieties (Mencía, Brancellao, and Merenzao) cultivated in Galician vineyards (North-West Spain) were determined. Different ripening stages (A: 176 ± 8 g/l reducing sugars; B: 193 ± 8 g/l reducing sugars; C: 210 ± 8 g/l reducing sugars; D: 227 ± 8 g/l reducing sugars) were also considered. Principal component analysis was performed for a better understanding of the differences found among grapes according to variety and ripening stage based on the skin and berry texture parameters. The parameters differentiating varieties were the skin break force and energy measured on the lateral side, whereas ripening stages can be classified on the basis of berry cohesiveness. The hardest berry skin was associated with the Merenzao variety with skin break force values comprised between 0.752–0.811 N and skin break energy between 0.715–0.790 mJ for A and B ripening stages, respectively. Instead, Brancellao variety presented the softest skin with skin break force values ranging from 0.521 to 0.562 N and skin break energy from 0.407 to 0.475 mJ for A and B ripening stages, respectively. Ripeness grade increased with the berry cohesiveness for all the varieties studied.     

AREA- AND PERIMETER-DEPENDENT PROPERTIES AND FAILURE OF MATURE-GREEN AND RED-RIPE TOMATO PERICARP TISSUE

The influence of tomato fruit ripeness on area- and perimeter-dependent properties and dominant failure mechanisms of pericarp tissue were investigated. Tissue discs from mature-green and red-ripe fruit were punctured with a flat-ended cylindrical probe and compressed with a flat plate at a constant rate of deformation. Approximately linear force-deformation curves were obtained to tissue failure by both puncture and flat plate compression, interrupted by a region of pseudoplastic deformation at a relatively low initial bioyield force. Based on estimated area- and perimeter-dependent coefficients and firmness (force/deformation) values, initial bioyielding of tissue appeared to be associated with an abrupt increase in cell-to-cell compaction. Puncture of mature-green tissue led to premature failure induced by shearing or rupture of tissue at the probe perimeter. The contribution to puncture of perimeter-dependent or shear-associated forces and a putative "zone of influence" increased markedly with ripening, while the contribution of area-dependent or compression associated forces generally decreased. A concomitant decrease in failure force and firmness with ripening reflected a general loss of both tissue compression and shear strengths. These results suggested that the dominant mode of tissue failure changed with ripening, from cell relaxation and rupture to cell debonding. The data obtained in this study emphasize the need to exercise caution in the interpretation of force-deformation parameters derived from puncture tests alone.     

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.     

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.     

Evaluation of tomato textural mechanical properties

The texture of fresh tomatoes (Lycopersicum esculentum Mill., ‘Momotaro’) at three different stage of ripeness (mature green, pink, and red) was intensively evaluated. The double-cycle load plate compression test showed that initial firmness, average firmness, energy absorption, deformation ratio, and relaxation ratio were sensitive textural parameters for identifying the maturity stages. From a puncture test, initial firmness, average firmness, apparent modulus of elasticity, rupture force, toughness, and deformation at the rupture point were sensitive to the maturity stages. The mature unripe tomato deformed linearly as a function of force; hence, the firmness was constant. However, the fully ripe tomato firmness increased as a function of applied force. The fruit strain increased during ripening, and it was independent of fruit size. The unripe tomato was more elastic than the ripe one. The peel at the mature green stage contributed approximately 70% of the firmness of the fruit and approximately 90% at the pink stage and red stage. The rupture force by the puncture test (traditionally, peak force) was correlated well with other textural parameters, which indicated that it could be used as a firmness representative parameter, as has been used by many researchers. The degree of elasticity was a better indicator for elasticity than the relaxation ratio.     

DETERMINING THE MECHANICAL PROPERTIES OF CHERRY TOMATO VARIETIES FOR HANDLING

Tomatoes, like other vegetables, are susceptible to different kinds of damage during and after harvest. Such damage is a major cause of quality loss in fruit. In order to reduce these losses, it is necessary to know the mechanical properties of the fruit. These mechanical properties of tomato were determined in terms of average rupture force, deformation energy, specific deformation and modulus of elasticity. Variance analysis was carried out on three tomato varieties, and the difference between the mean values was investigated by the least significant difference test. Mean values were represented with the standard error.
The results provide useful data to be used by engineers in the design of sorting, grading and packing machines, equipment for loading and unloading, storage structures, drying equipment, (all postharvest operations), harvesting machines and conveyors.

PRACTICAL APPLICATIONS

Our aim for this research is to get useful data for engineers in the design of sorting, grading and packing machines, equipment for loading and unloading, storage structures, drying equipment, harvesting machines and conveyors.     

Mechanical Properties of Pumpkin

Mechanical properties of three common varieties of pumpkin were evaluated and statistically compared. Toughness, rupture force, shear strength, and cutting force were determined for Jarrahdale, Jap, and Butternut varieties. The investigation was carried out in three cases of flesh, skin and unpeeled product, ignoring the toughness and rupture force of flesh. Relative contribution of skin to unpeeled case of each property was estimated. Varieties were found statistically alike in rupture force, toughness, and maximum shear strength force of unpeeled cases. Also the skin of three varieties showed similar strength in shear (p>0.05). Jap and Butternut varieties for some other properties showed close values. Maximum shear strength force of flesh, shear strength of unpeeled case, and relative contribution of skin to shear strength of unpeeled case were close (p>0.05) for these varieties. Jarrahdale had no difference in shear strength of flesh with two other varieties. It was also similar (p>0.05) to Jap in relative contribution of skin to shear strength, rupture force, and toughness of unpeeled case.     

EVALUATION OF THE TEXTURAL PROPERTIES OF JAPANESE PEAR

The texture of Japanese pear (Pyrus serotina Rehder var. culta 'Housui') during fruit enlargement and ripening was evaluated. From the plate compression test, only the deformation ratio, modulus of elasticity, and relaxation were the interpretable textural indices for the Japanese pear. From the puncture test, interpretable textural indices were the rupture force, deformation at the rupture point, toughness, average firmness, initial firmness, apparent modulus of elasticity, bioyield force, penetrating force and penetrating energy in the flesh. The skin of the Japanese pear contributed 70–80% of the firmness of the fruit. As the fruits enlarged, the strain decreased, the elasticity increased, the fruit skin was more prone to mechanical damage, the fruit flesh became softer, and firmness and rigidity of the whole fruit was reduced.     

湖南地区10个品种薄壳山核桃的坚果品质评价

为研究薄壳山核桃品种间坚果品质差异,筛选出在湖南地区表现优良的薄壳山核桃,以10个品种薄壳山核桃和2个品种普通核桃为材料,分别对各品种坚果表型性状[坚果横径、纵径、侧径、果形指数、果实形状、壳面、果壳颜色、果顶、果底(基)、缝合线、横隔膜]、经济性状(坚果质量、坚果含水率、果壳厚度、出仁率、取仁难易、核仁充实度、核仁饱满度、核仁颜色、核仁风味、核仁含油率)以及其油脂脂肪酸组成及含量进行测定,对薄壳山核桃品质指标进行了相关性分析和主成分分析,综合评价不同品种薄壳山核桃坚果品质。结果表明：在10个品种薄壳山核桃中,‘实生1号’‘德西拉布’‘实生3号’和‘福克特’果形指数较高,分别为2.24、2.15、2.15、1.99;单果质量较大的是‘金奥瓦’‘福克特’和‘德西拉布’,分别为9.24、8.30、8.06 g;出仁率较高的是‘实生4号’和‘金奥瓦’,分别为57.86%、57.08%;含油率较高的为‘福克特’‘佩洛奎’和‘德西拉布’,分别达到72.24%、70.66%、68.24%;薄壳山核桃绝大多数品质指标相互间都有相关性;主成分分析表明,‘德西拉布’的综合得分最高,其次是‘福克特’。综上...     

Effect of water activity on the mechanical properties of selected legumes and nuts

Two legumes (kidney beans and chickpeas) and two nut kernels (almonds and hazelnuts) were compressed intact with a Universal testing machine at various a_w levels in the range of 0·11–0·85 at an ambient temperature of 22°C. Mechanical characterisation of the four was done through four parameters; the slope of the initial part of force–displacement curve, considered a measure of stiffness, the failure force, considered a measure of strength, the deformation at failure, considered a measure of brittleness or deformability and the area under the force–displacement curve corresponding to 20% compression, considered a measure of toughness. Among these parameters only the latter could be determined and used effectively in all four seeds and along the whole water activity range. The jaggedness of the force–displacement curve was also determined in terms of its apparent fractal dimension calculated with two different algorithms for verification. There was a noticeable difference between the mechanical behaviour of the two groups. The nut kernels, apparently because of their high oil content, had a much smoother force–displacement curve, and the effect of absorbed moisture on their texture was generally more moderate than on that of the legumes. But in all the four types of seeds tested, each mechanical property had its own specific moisture dependency, an observation consistent with previous reports on cereal-based products. ©1997 SCI     

储藏期与储藏压力对稻谷籽粒压缩特性的影响研究

利用质构仪压缩稻谷籽粒的短轴来测定稻谷籽粒的压缩特性。测定的稻谷储藏在不同的时间与压力下。实验结果表明:当储藏时间为60 d且储藏压力由0 kPa增加到300 kPa,稻谷籽粒的破坏力由81.6 N减小到73.8 N,破坏能由8.10 mJ减小到6.27 mJ,破坏应变由0.139减小到0.117,表观接触弹性模量由171.3 MPa减小到57.7 MPa,最大接触应力由40.8 MPa减小到19.1 MPa。当稻谷储藏压力为77、100、139、200 kPa且储藏时间由0～60 d,稻谷籽粒的破坏力由81.6 N分别减小到79.6、79.1、78.2、77.0 N;破坏能由8.10 mJ分别减小到7.55、7.35、7.08、6.85 mJ;破坏应变由0.139分别减小到0.131、0.128、0.126、0.121;表观接触弹性模量由171.3 MPa分别减小到136.0、121.8、110.6、83.3 MPa;最大接触应力由41.2 MPa分别减小到35.0、32.5、30.3、15.0 MPa。结果表明储藏压力与储藏时间对稻谷籽粒的压缩特性有重要的影响。     

Development of a Finite Element Method Model to Determine Mechanical Behavior of Pumpkin Seed

In food process simulation studies, geometrical characterization of agricultural produce is extremely difficult due to their irregular shapes. Further simplifications and assumptions can be applied to overcome this problem. Also, applying 3D scanners may easily and realistically lead to more accurate results from simulations. The aim of this work was to study this discrepancy in the obtained values of the elastic parameters of organic materials under a compression case using a finite element method and experimental data. The Zaria variety of pumpkin seed was chosen as a typical sample of an organic material. A 3D scanner, high speed camera, and simulations using a finite element method were used to investigate modulus of elasticity, force, energy, and stress distribution of the pumpkin seed under the condition of parallel plate compression. The results of a compression test were used as experimental analysis. The force/deformation curve generated by the finite element method modeling matched the curve from the experimental test remarkably well up to 0.9 mm combined deformation and showed that the finite element method can be used to describe accurately mechanical behavior of pumpkin seed under compression.     

文冠果种子力学性能分析

通过万能材料试验机进行文冠果种子静态压缩破壳试验,并进行了三因素三水平正交试验,以含水率、加载速度、加载方向为因素,以初次破壳力、位移量、破壳应变能为指标,分析文冠果种子力学特性。结果表明:初次破壳力随着含水率的减少基本呈现上升趋势,位移量、破壳应变能随含水率的减少大致呈现下降趋势,在加载速度为5、10、15 mm/min时,x轴上的初次破壳力、位移量和破壳应变能基本均小于其他两个方向的;文冠果种子综合破壳效果的影响因素由大到小依次为含水率、加载方向、加载速度;最佳破壳条件为含水率37.14%、加载方向x轴、加载速度15 mm/min,在此条件下,初次破壳力为104.445 N。