Physical and mechanical properties of tomato fruits as related to robot’s harvesting

In order to better design, fabricate and control tomato harvesting robot, selected physical properties such as height, diameter, sphericity, surface area, volume, total mass, mass of pericarp and gelatinous matter, bulk density, density of pericarp and gelatinous matter, porosity, projected area, shape factor, and radius of curvature of two cultivar tomato fruits with different locule numbers were mainly investigated by image analysis and water displacement method. Mechanical properties such as friction and rolling resistance coefficients, and rupture energy, rupture force, compressibility, and loading slope of tomato fruits at two loading positions were determined by pull and loading test. Results showed the locule number had a significant effect (P < 0.05) on certain physical and mechanical parameters, such as height, diameter, surface area, rupture force, compressibility, and friction coefficient. The loading position also showed a significant effect (P < 0.05) on certain mechanical parameters, such as compressibility. The obtained properties are closely related to robot’s harvesting.     

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.     

1-MCP及其结构相似物处理对番茄采后贮藏效果的影响

为了研究环丙烯类乙烯抑制剂的作用效果,以绿熟期番茄为试材,用1-甲基环丙烯(1-MCP)、1-戊基环丙烯(1-PentCP)、1-辛基环丙烯(1-OCP)处理后,常温(18℃±2℃)贮藏,每隔3 d测定1次理化指标,研究三者对番茄果实后熟衰老和贮藏效果的影响。结果表明:1-MCP及其结构相似物处理番茄不同程度地降低了呼吸强度和乙烯释放量的峰值,抑制了番茄果实硬度的下降,延缓了可溶性固形物含量的上升,同时也有效抑制了后熟期番茄果实过氧化氢酶(CAT)活性、过氧化物酶(POD)活性,延缓了果实的后熟衰老。3种试验的抑制剂中,1-MCP、1-PentCP和1-OCP处理随支链长度的增加,抑制后熟衰老的效果依次降低。     

Multiscale Biomechanics of Tomato Fruits: A Review

Bruising and other mechanical damage to fruit caused by external forces during and postharvesting is manifested at the macroscale but is ultimately the result of failure of cells at the microscale. However, fruits have internal structures and cells from different tissue types react differently to application of an external force. Not much is known about the effects of such forces on single cells within tissues and one reason for this is the lack of multiscale models linking macro- (organ or whole fruit), meso- (tissue), and micro- (cell) mechanics. This review concerns tomato fruits specifically as this is an important crop and is an excellent exemplar of past and proposed research in this field. The first consideration is the multiscale anatomy of tomato fruits that provides the basis for mechanical modeling. The literature on experimental methods for studying multiscale mechanics of fruit is then reviewed, as are recent results from using those methods. Finally, future research directions are discussed, in particular the combination of work over all scales. It is clear that a bottom-up approach incorporating single-cell mechanics in finite element models of whole fruit assumed to have internal structures is a promising way forward for tomato fruits but further method developments may be needed for these and other fruits and vegetables, in particular recovery of representative single cells from tissues for mechanical characterization.     

CREEP BEHAVIOUR OF TOMATO PERICARP TISSUE AS INFLUENCED BY AMBIENT TEMPERATURE RIPENING AND CHILLED STORAGE

The influence of normal ripening and chilling stress on viscoelastic properties of tomato pericarp tissue were investigated by measuring creep behaviour of tissue from fruit stored at 22C (nonchilled) or 5C (chilled) for 28 days, or at 5C for 16 days prior to transfer to 22C for an additional 12 days (prechilled). Creep compliance of tissue from all treatments subjected to a constant shear stress of 150 Pa for 5 min was best represented by a 6-element Burgers model containing two discrete Voigt-Kelvin units characterizing fast and slow rate viscoelastic properties. The magnitude of instantaneous elastic, viscoelastic and steady-state viscous compliances each increased steadily and contributed to the overall softening of nonchilled and prechilled tissues during ripening, but remained unchanged during chilling of tomato fruit. Increased fluidity of ripening tissues occurred at the expense of elasticity, consistent with a decrease in molecular weight-size distribution of structural elements contributing to respective viscoelastic properties. The physico-mechanical changes in prechilled tissue preceded those in nonchilled tissue by several days, and occurred at a faster rate. The 6-element Burgers model defining the creep behaviour of tomato pericarp tissue was interpreted with respect to general plant cell wall structure and biochemical changes known to occur during ripening of tomato fruits. Multiple mechanisms of softening were thereby consolidated into a single physico-mechanical model.     

果蔬复合凝固型酸牛奶的研制

从天然果蔬中精选大豆、胡萝卜、番茄、枸杞,制取果蔬汁,并按一定的工艺要求复配,经乳酸发酵后产生酸甜可口、风味独特、色泽宜人、营养丰富、老少皆宜的果蔬复合酸奶。同时对产品的稳定进行了研究,采用正交试验法筛选出最佳配方：豆奶25％、脱脂奶粉8．25％、胡萝卜汁30％、番茄汁8％、枸杞汁5％、白砂糖8％,以及0．1％的耐酸CMC－Na和0．2％的藻酸丙二醇（PGA）。     

Investigation of UV-A light irradiation on tomato fruit injury during storage

We investigated the effect of UV-A light (wavelength 315 to 400 nm) irradiation during storage on tomato fruit injury. Mature green tomato fruit (cv. House Momotaro) were exposed to UV-A at doses of 0.02, 0.5, and 2 mW x cm(-2) throughout storage at 25 degrees C. The physiological disorders, fruit ripening, superoxide dismutase (SOD) activity, and increases in fruit temperature were evaluated. All UV-A-irradiated and nonirradiated tomatoes developed a full red color at the same time (2 weeks). Irradiated fruit ripened normally, and exposure of tomato fruits to UV-A did not lead to the discoloration of ripe tomato fruit at any dosage. The fruit temperature did not increase in response to various UV-A light doses and exposure times, and none of the UV-irradiated fruits showed physiological disorders (dull skin blemish, pitting). The SOD activity of UV-A-irradiated fruit exposed to the various UV-A doses did not significantly (P = 0.05) differ from that of fruit stored in dark conditions. The SOD results imply that UV-A light might not induce reactive oxygen species in UV-A-irradiated fruit.     

增施CO2与LED补光对番茄果实品质及挥发性物质的影响

以‘金棚1号’番茄为实验材料,研究了在秋冬季日光温室里增施不同浓度CO2和LED补光对番茄果实产 量、品质以及挥发性芳香物质的影响。结果表明：LED补光＋增施CO2 1 200 μL/L的处理条件可显著提高番茄果实 中可溶性固形物、总酸、可溶性蛋白质和番茄红素的含量,显著增加单果质量、果实颜色,并显著降低果实硝酸盐 的含量。利用顶空固相萃取结合气相色谱-质谱联用仪对果实的挥发性芳香物质的含量进行测定,结果表明LED补 光与增施CO2提高了番茄特征挥发性芳香物质的含量,如6-甲基-5-庚烯-2酮、β-紫罗兰酮和己醛等,也丰富了其种 类,使番茄果味香浓,香气丰富。     

Diffusion of carbon dioxide in tomato fruits during cold storage in modified atmosphere

Treatments with 20% CO₂ of tomato fruit produced a beneficial extension of storage life. The diffusion of CO₂ in tomato (Lycopersicon esculentum Mill) cv. Platense was measured chromatographically and the concentration profiles in the internal gaseous atmosphere of the fruit were determined for non-steady state conditions to establish minimum treatment times that can ensure adequate penetration of the gas.
The effective diffusivity of CO₂ in the tissue was determined by fitting concentration data, obtained from experiments with whole fruit without skin, to the non-steady state solution of the diffusion equation, assuming negligible external mass transfer resistance. The diffusivity was modelled using Maxwell-Eucken expressions, taking account of the heterogeneous structure of the tissue.
The resistance of the fruit skin was evaluated using whole fruits with the stem scar covered with paraffin and fitting experimental data to the solution in terms of mass Biot number; the specific resistance of the peel was some 200 times greater than that of the stem scar.     

Grafting tomato plant on tobacco plant and its effect on tomato plant yield and nicotine content

BACKGROUND: Two different tomato scions, cv. Elazig and cv. Sweet (cherry) (Solanum lycopersicum L.) were self‐grafted and grafted onto tobacco root stock (Nicotiana tobacum L.). Then, grafted tomato plants were evaluated in terms of flower and fruit yield. Tobacco‐grafted tomato plant fruits were also evaluated for nicotine content. RESULTS: Tobacco grafting had a positive effect on the tomato plant cultivation performance; the onset of flowering was almost 15 days earlier and the tomato flower and fruit yields increased in both tomato cultivars. Tobacco grafting resulted in 5.0% and 30.1% increase in total fruit weight for cv. Sweet and cv. Elazig, respectively. Because the level of nicotine was within acceptable ranges, tobacco‐grafted tomato fruits were considered to be safe for consumption. Self‐grafted tomato cultivars also had flowering time onsets almost 11 days earlier. However, self‐grafting caused 6.0% and 7.6% less total fruit yield per cv. Sweet and cv. Elazig, respectively. CONCLUSION: In conclusion, our results show that tomato–tobacco grafting is a novel and promising technique for improvement of not only tomato plant performance and yield, but also that it can be employed to various tomato varieties. Copyright © 2009 Society of Chemical Industry     

番茄交链孢病原菌鉴定及产毒分析

目的 通过对番茄病果中链格孢病原菌的分离鉴定及产毒分析,为番茄采收后病害防控提供理论依据。方法 采集福建省5个县市番茄病果,通过切片和组织分离法从番茄病害部位分离纯化病原菌,结合形态学特征和分子生物学对病原菌进行鉴定。根据柯赫氏法则确定病原菌的致病性,并利用超高效液相串联质谱法对分离得到的交链格孢菌产毒能力进行检测分析。结果 在发病番茄病害部位共分离得到的 3株互隔链格孢菌株均具产毒能力,但毒素种类和产毒能力各有不同,其中NH06菌株产毒量最高,可产生细交链格孢酮酸(tenuazonic acid,TeA )、交链孢酚 (alternariol, AOH)、交链孢酚单甲醚(alternariol monomethyl ether, AME)、交链孢烯(altenuene,ALT )、腾毒素 (tentoxin,TEN ) 5种毒素,而NP002和NH07仅检出产生4种毒素。结论 福建省番茄种植产区内存在交链格孢菌的污染,且产毒种类多,因此,在番茄种植产区内病果的处理应引起关注和重视。     

Difference in volatile composition between the pericarp tissue and inner tissue of tomato (Solanum lycopersicum) fruit

Numerous studies have reported the volatile profiles in the whole fruit or pericarp tissue of tomato (Solanum lycopersicum) fruit; however, information is limited on the volatile composition in the inner tissue and its contribution to tomato aroma. For this, the pericarps and inner tissues of “Moneymaker,” “UglyRipe,” and “FL 47” fruits were separated before volatile analysis. Result showed that the volatile profiles were quite similar between the pericarp and inner tissue, suggesting the inner tissues also have a contribution to overall aroma quality. Besides the difference in volatile profile among cultivars, a higher concentration of alcohols was observed in the inner tissues of tomato fruit in comparison with that in the pericarp, which was associated with higher levels of 3‐methylbutanal, 2‐methylbutanal, 3‐methylbutanol, and 2‐methylbutanol in the inner tissue. These results also imply that different sampling methods might impact tomato aroma quality, which needs further verification via sensory penal.

Practical applications

The information on the volatile profile in the inner tissue and its contribution to tomato aroma is still rudimentary. In this study, the pericarp and inner tissue were separated from three tomato cultivars of different genetic background, and the volatile compositions were analyzed with HS‐SPME‐GC‐MS. Result showed that the volatile compositions were quite similar between the pericarp and inner tissue, suggesting that the inner tissues also have a contribution to overall aroma quality. Besides, a higher concentration of alcohols was observed in the inner tissues of tomato fruit in comparison with that in the pericarp, which was associated with higher levels of 3‐methylbutanal, 2‐methylbutanal, 3‐methylbutanol, and 2‐methylbutanol in the inner tissue. This study will provide the researchers and consumers some useful information on volatile composition in the inner tissue, its contribution to tomato aroma, and the impact of different sampling methods on the volatile profile.     

Structural changes,chemical composition and antioxidant activity of cherry tomato fruits (cv. Micro‐Tom) stored under optimal and chilling conditions

BACKGROUND: Cherry tomato fruits cv. Micro‐Tom, a model plant for tomato genetics, were analysed in order to determine the main structural and chemical changes under optimal and chilling storage conditions. The comparison of Micro‐Tom to standard tomato cultivars will give an insight into suitability of this dwarf cultivar as a model for studying the influence of low‐temperature conditions on tomato fruits. RESULTS: During chilling, fruit tissue was progressively destroyed due to the collapse of the deep layers of the pericarp. Chilling lowered the typical tomato kinetics of ripening in sugars (glucose, fructose, sucrose), organic acids (tartaric, malic, citric, ascorbic and succinic) and the antioxidants phenol and lycopene, while carotenoid synthesis seemed to be blocked. Glutathione level was elevated and the activity of ROS scavenging enzymes was altered. Essentially, Micro‐Tom fruits showed a quality evolution that was similar to that described for standard tomato cultivars. CONCLUSION: The cherry tomato cultivar Micro‐Tom could be used as a model for studying the influence of low temperature on biochemical and structural changes taking place during chilling injury conditions. Copyright © 2009 Society of Chemical Industry     

The effects of 1-methylcyclopropene treatment on the shelf life and quality of cherry tomato (Lycopersicon esculentum var. cerasiforme) fruit

The use of 1‐methylcyclopropene (1‐MCP) to extend the shelf life of cherry tomato (Lycopersicon esculentum var. cerasiforme) was investigated. Higher concentrations of 1‐MCP delayed the ethylene induced climacteric peaks in mature green (MG) and breaker (BR) fruits. Thirteen days after treatment, control fruits were 55% as firm as fruit treated with 0.11 μL L^?1 1‐MCP. The initiation of fruit softening, chlorophyll degradation and accumulation of lycopene and carotenoids was delayed in treated fruits. Higher 1‐MCP concentrations inhibited the accumulation of lycopene and carotene such that the colour of the fruit did not reach that of control fruit. Treatment of MG cherry tomatoes with 1‐MCP enhanced shelf life optimally, while treatment of BR fruits was beneficial where full colour and high content of lycopene and carotenoids is important. Differentiation of the different stages of ripening before application of 1‐MCP is needed in order to succeed in accomplishing different postharvest objectives.     

TOMATO PERICARP TISSUE RESONANCE AND ITS USE IN TEXTURE EVALUATION

The use of resonance properties, measured by dynamic oscillation using a constant stress rheometer, as textural parameters for excised pericarp tissue of tomato ( Lycopersicon esculentum Mill cv Trust) fruit during 21 days of ambient temperature ripening was assessed relative to the large-deformation behavior measured by flat-plate compression. The resonance frequency (f_r) of excised tissue discs decreased significantly (P < 0.05) over the first 9–12 days, and then approached a relatively low and constant value with subsequent ripening. A significant (P < 0.05) increase in associated resonance strain amplitude (y_max) became apparent after the first 9–12 days of tomato fruit ripening. Ripening-associated changes in bioyield and failure strengths, toughness, and apparent elastic and failure deformability moduli derived from flat-plate compression tests were similar to those observed for tissue f_r. Results were consistent with a change in the dominant mode of tissue failure from cell relaxation and rupture to debonding after 9–12 days of fruit ripening. A significant (P < 0.05) semilogarithmic relationship was observed between f_r, but not y_max, and compression parameters, allowing for reasonable prediction of large-deformation behavior on the basis of measurement of only f_r. The results demonstrate that resonance frequency may provide a useful parameter in the evaluation of tomato pericarp tissue texture.     

Nitrogen and potassium requirements of tomato plants for the optimization of fruit quality and antioxidative capacity during storage

While nitrogen (N) and potassium (K) fertilizers are commonly used in tomato fields for increasing plant growth and productivity, concepts regarding the interactive effects of these elements on tomato fruit quality during storage are ambiguous. The interactive effects of potassium (0, 250 and 500 mg kg soil^??1) and nitrogen (0, 150 and 300 mg kg soil^??1) fertilizers were tested on tomato fruit size at harvest, and their quality was evaluated after 30 days of storage at 4 °C. Fruit mass, firmness, taste-related parameters, inorganic nutrients, bioactive compounds, and antioxidative capacity of the fruits were investigated after the storage period. Application of 250–500 mg K in combination with 150 mg N per kg soil improved fruit mass at harvest and reduced loss of mass during storage. By increasing the soil’s K supply, the fruits exhibited significant increases in their amount of potassium, TSS and TA contents, antioxidative capacity, concentrations of lycopene, phenolics and ascorbic acid. Nonetheless, increasing the soil’s K concentration reduced Ca concentration and firmness of the fruits. By increasing the N concentration in the soil, a trend of decline was observed in the fruits’ TSS, soluble phenolics, lycopene and ascorbic acid contents. However, higher amounts of N and TA contents were detected in fruits treated with 300 mg N kg soil^??1. N treatments did not affect the antioxidative capacity of the fruits. Accordingly, application of 250 mg K?+?150 mg N kg soil^??1 was suggested as the optimum treatment that could yield tomato fruits with high quality and that would also have improved storage capability.     

施硒对樱桃番茄贮藏品质及3种活性氧代谢酶的影响

为探寻施硒对樱桃番茄采后贮藏品质的影响并确定其适宜的处理浓度,在樱桃番茄发育过程中分次冲施不同浓度硒肥,分析番茄果实采收时及在贮藏过程中果实硬度、色泽、乙烯释放量、糖、酸、V_C含量及活性氧代谢相关酶活性的变化情况。结果表明,采收时2 mg/L硒处理的樱桃番茄果实硬度、可溶性糖含量、V_C含量与对照组相比分别增加了7.98%、5.29%和11.32%,并在贮藏过程中始终维持较高含量;同时2 mg/L硒处理提高了采后果实过氧化物酶活性(40.01~64.24 U/g)和超氧化物歧化酶活性(36.94~186.39 U/g);并在乙烯释放高峰时期(21 d)抑制乙烯释放量至8.01 μL/kg·h,延缓了樱桃番茄果实的采后衰老。而3 mg/L硒处理在贮藏42 d时对果实的活性氧代谢酶表现出负面影响,过氧化氢酶、过氧化物酶、超氧化物歧化酶活性分别低于对照组11.93%、23.09%和31.01%,不利于维持番茄果实的贮藏品质。2 mg/L为适宜的采前硒处理浓度,可以提升樱桃番茄果实品质及贮藏特性。     

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.     

The Effects of Genetic Transformation of Tomato with Antisense Phospholipase D cDNA on the Quality Characteristics of Fruits and Their Processed Products

The physico-chemical characteristics of tomato juice and sauce, prepared from transgenic tomato fruits (Lycopersicon esculentum Mill, var. Celebrity) transformed with an antisense phospholipase D (PLD) cDNA construct, were evaluated. The antisense transformation resulted in a 30-40% reduction of PLD activity in ripe fruits. The transgenic fruits were firmer, possessed better red color, and flavor. The juice and sauce preparations from transgenic fruits showed improved red color, lycopene content, Brookfield viscosity, and increased levels of major flavor volatiles such as hexenal. The dry matter and ash contents, as well as the precipitate weight ratio (PPT) of the transgenic fruit products were significantly higher when compared to the products from control fruits. The vitamin C content of the transgenic fruits was also higher as compared to the control fruits. The results suggest that a reduction in PLD activity may lead to increased membrane stability and preservation of membrane compartmentalization that can have positive quality impacts in transgenic fruits and their products.     

FAILURE MECHANISMS OF TOMATO PERICARP TISSUE SUGGESTED BY LARGE AND SMALL DEFORMATION TESTS

Failure mechanisms of tomato pericarp tissue were investigated by measuring puncture and viscoelastic properties of tissue from fruit stored at 22C (nonchilled) or 5C (chilled) for 28 days, or at 5C for 15 days prior to transfer to 22C for an additional 13 days (prechilled) to facilitate ripening. The puncture properties of tissue remained unchanged during 28 days of chilling. However, tissue shear strength and rigidity increased with chilling, as demonstrated by increases in storage and loss moduli, and decreases in oscillatory strain and the loss tangent. Puncture failure force, failure firmness and storage and loss moduli of nonchilled and prechilled tissues decreased to low, constant levels by 12 and 9 days, respectively. Simultaneously, pseudoplastic and failure strains and oscillatory strain each increased. These data suggest that the loss of tissue compressive strengths and transition in the dominant mode of failure from cell relaxation and rupture to cell debonding occurred at a faster rate during ripening of prechilled (i.e., chill-injured) compared to nonchilled fruit.