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.     

Effects of packaging materials,storage conditions and variety on oxidative stability of shelled walnuts

The effects of storage temperature, oxygen permeability of packaging material and variety on oxidative stability of vacuum-packaged walnut kernels were studied over a 12 months storage period. The oxidation experiments applied to two popular walnut varieties (Yalova-1 and Yalova-3) grown in Turkey. The peroxide values and hexanal contents of walnut samples significantly increased (p < 0.01) during storage at 30 °C. The highest hexanal content (4464.5–6406.9 μg/kg) were observed in Yalova-3 variety stored at 30 °C for 12 months in Polyamide/Polyethylene film pouches (oxygen permeability: 63.4 ± 0.4 mL/m²/24 h (23 °C)) with 90 μm total thickness. The effect of storage temperature and variety on lipid oxidation was found to be higher than the effect of oxygen permeability of the packaging material. It was concluded that for vacuum-packed walnut kernels in PA/PE film pouches having 63.4 ± 0.4 mL/m²/24 h (23 °C) oxygen permeability, 20 °C is sufficient to protect against oxidation for 12 months.     

Relations among mechanical properties, human bite parameters, and ease of chewing of solid foods with various textures

This study clarified relations among human bite parameters, mechanical properties, and sensory-determined ease of chewing for 11 solid foods having various textures. A multiple-point sheet sensor measured the human bite force, pressure, and impulse between molars during the first chew. Foods were categorized into four classes based on the shapes and magnitudes of human bite force–time curves. The bite parameters and mechanical parameters shared, in most cases, a non-linear relation, for which a power law model was usually representative. Bite parameters were compared with results of compression and puncture tests obtained using a universal testing machine. The highest correlation was found between the logarithm of the maximum bite force and the logarithm of the puncture force (R = 0.916). Sensory evaluation revealed the optimum correlation between the impulse during the first bite and ease of chewing (R = −0.872). Ease of chewing was assessed during the first bite rather than at the maximum force point because the bite impulse showed a higher correlation than the maximum bite force and pressure. The prediction of ease of chewing was acceptable for use with the work in compression tests (R = −0.689).     

A dry-inoculation method for nut kernels

A dry-inoculation method for almonds and walnuts was developed to eliminate the need for the postinoculation drying required for wet-inoculation methods. The survival of Salmonella enterica Enteritidis PT 30 on wet- and dry-inoculated almond and walnut kernels stored under ambient conditions (average: 23 °C; 41 or 47% RH) was then compared over 14 weeks. For wet inoculation, an aqueous Salmonella preparation was added directly to almond or walnut kernels, which were then dried under ambient conditions (3 or 7 days, respectively) to initial nut moisture levels. For the dry inoculation, liquid inoculum was mixed with sterilized sand and dried for 24 h at 40 °C. The dried inoculated sand was mixed with kernels, and the sand was removed by shaking the mixture in a sterile sieve. Mixing procedures to optimize the bacterial transfer from sand to kernel were evaluated; in general, similar levels were achieved on walnuts (4.8–5.2 log CFU/g) and almonds (4.2–5.1 log CFU/g). The decline of Salmonella Enteritidis populations was similar during ambient storage (98 days) for both wet-and dry-inoculation methods for both almonds and walnuts. The dry-inoculation method mimics some of the suspected routes of contamination for tree nuts and may be appropriate for some postharvest challenge studies.     

Physico‐mechanical evaluation of the aptitude of berries of red wine grape varieties to resist the compression in carbonic maceration vinification

By texture analysis tests, the ability of berries to resist rupture under compression load during intracellular fermentation was studied for twenty‐three red wine grape varieties. The softest berries were associated with Ancellotta (1.72 N), Dolcetto (1.79 N), Gamay (2.26 N) and Schiava gentile (2.29 N) cultivars. The hardest berries corresponded to Franconia and Bonarda cultivars (4.02–4.03 N). High resistance to splitting was also detected for Grenache, Raboso, Marzemino, Negramaro, Montepulciano and Croatina cultivars (3.50–3.95 N). The differentiating power of the mechanical variables of the whole berry and skin was assessed by univariate and multivariate analysis. Relationships among the instrumental berry hardness and other physical and mechanical properties were also investigated. The results obtained suggest that the manufacture of carbonic macerated wines should be planned considering the berry hardness, and it represents a new variable that should be considered in selecting the most appropriate wine grape variety to elaborate these wines.     

Screening various Yarrowia lipolytica strains for citric acid production

Citric acid (CA) productivity by Yarrowia lipolytica dependents on strain type, carbon source, carbon to nitrogen (C/N) molar ratio as well as physicochemical conditions (pH, temperature, oxygen transfer rate, etc.). In the current study, 10 different Y. lipolytica strains were first challenged in shake-flask culture for CA production in a glucose-based media under nitrogen-limited conditions. For the most promising one, strain K57, CA productivity was monitored during culture in batch bioreactor for three initial C/N molar ratio (167, 367, and 567 Cmol/Nmol). The highest CA yield (0.77 g/g glucose), titre (72.3 g/L CA), and productivity (0.04 g/g.h) were found for C/N ratio of 367. However, the highest growth rate was obtained for an initial C/N ratio of 167. From these results, Y. lipolytica strain K57 could be considered to produce CA at higher titre on glucose-based medium in batch bioreactor than others Y. lipolytica strain reported in the literature.     

Effect of γ-irradiation on the physicochemical and sensory properties of walnuts (<Emphasis Type="Italic">Juglans regia</Emphasis> L.)

The present study evaluated physicochemical and sensory quality parameters of walnuts as a function of irradiation dose in order to determine dose levels causing minimal undesirable changes to walnuts. Physicochemical parameters including peroxide value (PV), hexanal content, fatty acid composition, volatile compounds and sensory parameters including color, texture, odor and taste were determined for unirradiated and irradiated walnuts at radiation doses of 1.0, 1.5, 3.0, 5.0 and 7.0 kGy. PV increased from 1.1 to 3.0 meq O₂/kg walnut oil while the hexanal content increased from 3.80 to 34.3 mg/kg walnut after irradiation at a dose of 7.0 kGy. Of the fatty acids determined, stearic and palmitic acids concentration increased while oleic acid decreased with irradiation dose. Polyunsaturated fatty acids were unaffected by irradiation. Volatile compounds such as aldehydes, ketones, alcohols and hydrocarbons increased after irradiation indicating enhanced lipid oxidation. Color parameter L*, a* and b* remained unaffected by irradiation. Sensory analysis showed that taste was the most sensitive of all sensory attributes for the evaluation of walnut quality. Based on taste and odor scores, walnuts remained organoleptically acceptable at doses ≤3.0 kGy.     

青核桃脱皮机理及装置设计与试验

目的:提高核桃初加工过程的机械化水平，解决青核桃脱皮过程中脱净率低、破碎率高等问题。方法:设计一种集刮削挤压、滚刷和清洗于一体的青核桃脱皮装置；对青核桃脱皮过程进行力学与运动学分析，结合理论力学理论建立青核桃空间受力模型，并对关键系统装置进行结构设计。在单因素试验基础上，以转速、对辊末端间距和中心距的取值范围为影响因素，利用Design-Expert 13进行三因素三水平试验，优化青核桃脱皮装置工作参数。结果:青核桃脱皮装置的最佳工作参数为转速64.54 r/min、对辊末端间距41.7 mm、中心距9.44 mm,此条件下的核桃脱净率为91.92%,破碎率为4.49%。结论:该脱皮装置能满足青核桃脱皮生产要求。     

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。     

Mechanical behaviour of hazelnuts used for table consumption under compression loading

Nuts of four hazelnut varieties and five new selections used for table consumption were compressed at the moisture content of 6% wet basis to measure shell resistance to breakage. Rupture force, rupture energy and nut specific deformation were measured under three compression loading positions. Physical parameters of nuts were also evaluated to relate them to the data obtained by compression test measurements. Rupture force and nut specific deformation are the most discriminant parameters that can be used to describe the behaviour under compression, while rupture energy values show fewer differences among the considered varieties. The values of force required to break nut shell ranged from 322.2 to 769.3 N. The lowest values of force were generally obtained along the y‐axis, the transverse axis containing the major dimension at right angles to the longitudinal axis. Nut specific deformation ranged from 3.35 to 11.76%. Correlations between physical and texture parameters showed that values of force, energy and deformation were dependent on different parameters that varied in the three considered axis. The most used varieties, Ennis and Barcelona, showed high mean values of force rupture to break shell and low deformability, while Tonda Giffoni and Tonda Bianca were easy to break. Among the new selections, L35 and B6, with mean values of force rupture less than 428 N and values of nut specific deformation higher than 8%, were suitable for table consumption. Copyright © 2006 Society of Chemical Industry     

Physical and stress-strain properties of wheat (Triticum aestivum) kernel

BACKGROUND: Two hard wheat varieties and one soft variety grown under the same agroecological conditions were analyzed for their physical and uniaxial stress–strain compression properties. RESULTS: The physical properties of wheat kernel were determined at a moisture content of 0.13 kg kg^?1 (wet basis), whereas the stress–strain compression test was conducted at a kernel moisture content from 0.082 to 0.433 kg kg^?1. Mean kernel lengths were 5.46 (5.37 and 5.38) mm, widths were 2.56 (2.47 and 2.62) mm and thicknesses were 2.12 (2.18 and 2.43) mm for Simonida, Dragana and NS 40S cultivars, respectively. Bulk densities were 791.34 (Simonida), 788.51 (Dragana) and 731.77 kg m^?3 (NS 40S). The force at the yield point was 241.46 N for Dragana (moisture content 0.133 kg kg^?1), 244.30 N for Simonida (0.136 kg kg^?1) and 164.90 N for NS 40S (0.433 kg kg^?1). CONCLUSION: The width and thickness of the analyzed kernels were small compared with the length, and bulk densities were also moderate. The yield point force values of the two hard varieties were 2.2 times higher than the values of the soft variety, at a moisture content of 0.136 kg kg^?1 for Simonida, 0.133 kg kg^?1 for Dragana and 0.141 kg kg^?1 for NS 40S. Copyright © 2011 Society of Chemical Industry     

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.     

Effects of feed moisture and extruder screw speed and temperature on physical characteristics and antioxidant activity of extruded proso millet (Panicum miliaceum) flour

The objective of this work was to determine the impact of extrusion variables [moisture (17–25%), screw speed (170–250 r.p.m.) and temperature (90–150 °C)] on the physical properties and antioxidant activity of proso millet extrudates. Extrusion variables were adjusted using an inscribed central composite rotatable design. Response variables were bulk density (BD), radial expansion ratio, water absorption index, water solubility index, hardness, colour (L*, a*, b*) and antioxidant activity. Moisture and screw speed were the most influential variables affecting millet extrusion: their linear, quadratic and interaction terms accounted for more than 50% of the variability in all responses except for b*. Expansion was greatest at severe conditions of low moisture and high screw speed. These conditions were also consistent with the highest antioxidant activity. This study demonstrated that high expansion and antioxidant activity can be obtained by extruding proso millet under low moisture and high screw speed conditions.     

采摘期对新疆3个品种核桃品质的影响

为了研究不同采摘期对核桃品质的影响,以温185、新2、扎343为试验材料,分别于2014年9月1日、9月10日、9月20日、9月30日、10月10日进行采样,并对样品的主要品质指标进行测定。结果表明:随着采摘期的延长,温185、新2、扎343核桃的还原糖含量、脂肪含量、蛋白质含量不断增加,在10月10日均达到最高值;9月30日采摘的核桃其VE含量与灰分含量相对较高,水分损失相对较少;整体而言,单一核桃品种的营养含量有变化,3个品种核桃的营养含量在不同的采摘期也有显著性差异。综合3个良种核桃内在品质的检测,认为9月30日为最佳的采摘期。     

Volatile compounds in light, medium, and dark black walnut and their influence on the sensory aromatic profile

Light, medium, and dark colored kernels from 3 different cultivars (Emma K, Kwik Krop, and Sparks 127) and one wild species of black walnut were studied for their aroma volatiles. Solid-phase microextraction-gas chromatography-mass spectrometry was used to determine the aromatic compounds present in the headspace of these samples. Partial least square regression was used to correlate the instrumental aromatic data with the sensory responses, obtained in a previous study, for the same samples. Thirty-four aromatic compounds were found in the black walnut cultivars, highlighting among them the presence of 14 esters. Although more than 50% of the total concentration of volatile compounds, esters were not important compounds in determining the differences in the sensory aromatic profiles of the 3 colors of the nuts. As a general trend, the concentration of total volatile compounds was always significantly higher in light black walnuts than in the medium colored samples; medium colored samples had higher volatile content than the dark black walnuts. The presence of hexanal was related to rancid and acrid aromas and was determined to differentiate the dark black walnuts from the medium and light colored samples. PRACTICAL APPLICATION: The data presented in this article will help understand the aromatic differences between light, medium, and dark colored kernels of domestic and wild black walnut. The aromatic profile of these nuts, not studied until this moment, can be used as a model to develop flavorings and new products by the food industries.     

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.     

Textural and physicochemical predictors of sensory texture and sweetness of boiled plantain

Boiled pulp is a major form of consumption for plantain. We assessed instrumental (puncture test and texture profile analysis) and sensory texture attributes of 13 plantain cultivars, two cooking hybrids and one dessert banana at different stages of ripeness after cooking in boiling water. Firmness, chewiness, stickiness, mealiness, sweetness and moistness described sensory variability, which was greater between stages of ripeness than between types of cultivars. Firmness and chewiness were well-predicted by instrumental force and hardness (r² > 0.72), and by soluble solid and dry matter content (r² > 0.85). Complementary sensitivity analysis revealed that a pulp puncture force or a hardness of at least 2.1 N or of 0.3 N/mm² was needed before a difference in firmness or chewiness could be perceived; a Brix of 3.7 was required to ensure a detectable difference in sweetness. Rheological and biochemical predictors can be useful for breeders for high-throughput phenotyping.