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     

Alleviation of chilling injury in postharvest tomato fruit by preconditioning with ultraviolet irradiation

BACKGROUND: Tomato fruit is usually stored at low temperatures for delayed ripening and extended shelf life. However, tomato fruit is susceptible to chilling injury when exposed to low temperatures. In this study, the potential effects of preconditioning with UV‐C or UV‐B irradiation on chilling injury of postharvest tomato fruit were investigated. RESULTS: Mature–green tomato fruit were exposed to 4 kJ m^?2 UV‐C or 20 kJ m^?2 UV‐B irradiation and stored for 20 days at 2 °C and subsequently 10 days at 20 °C. UV irradiation was effective in reducing chilling injury index and delaying ethylene peak. Furthermore, UV irradiation preserved storage quality as manifested by reduced weight loss, better retention of firmness, and higher contents of total soluble solids, soluble protein and soluble sugar during subsequent storage at 20 °C. UV‐C irradiation significantly delayed the development of the red colour after 10 days of storage at 20 °C. On the other hand, UV irradiation decreased total phenolics content and antioxidant capacity, suggesting possibly reduced stress response to low temperature resulted from enhanced physiological adaptation by UV preconditioning. CONCLUSION: Our results suggest that preconditioning with UV‐C or UV‐B irradiation in appropriate doses had a positive effect on alleviating chilling injury in postharvest tomato fruit. Copyright © 2012 Society of Chemical Industry     

LeMAPK4 participated in cold‐induced ethylene production in tomato fruit

BACKGROUND: Mitogen‐activated protein kinase (MAPK, EC 2.7.11.24) cascade from several plant species has been shown to be activated during response to abiotic stress. Ethylene plays an important role in fruit tolerance to environmental stress. However, the mechanisms by which MAPK regulates defence systems in fruit and the relationship between MAPK and ethylene remain to be determined. RESULTS: MAPK inhibitor significantly decreased the chilling tolerance of tomato (Lycopersicon esculentum cv. Lichun) fruit during cold storage. Moreover, decreases in ethylene content, LeACS2 expression and activities of 1‐aminocyclopropane‐1‐carboxylic acid (ACC) synthase (ACS, EC 4.4.1.14) and ACC oxidase (ACO, EC 1.14.17.4) due to MAPK inhibitor occurred within 24 h after cold treatment. Upon treatment with cold and ethephon, the ethylene content, activities of ACS and ACO and expression of LeACS2, LeACO1 and LeMAPK4 increased. CONCLUSION: The results showed the regulation of MAPK in ethylene biosynthesis to protect tomato fruit from cold stress. In addition, the participation of LeMAPK4 in cold‐induced ethylene biosynthesis in tomato fruit was indicated. © 2013 Society of Chemical Industry     

Environmental conditions in relation to stress in cherry tomato fruits in two experimental Mediterranean greenhouses

BACKGROUND: Considering the economic importance of tomato and its nutritional benefits to human health, a study was conducted on how different environmental factors (temperature, solar radiation and vapour pressure deficit (VPD)) influence hydrogen peroxide detoxification and several stress indicators in cherry tomato (Solanum lycopersicum cv. Naomi) fruits grown in two experimental Mediterranean greenhouses of parral (low‐technology) type and multispan (high‐technology) type. RESULTS: Three fruit samplings were made at the beginning, middle and end of the fruit production period. Values of temperature, solar radiation and VPD peaked at the third sampling in both greenhouses, being higher in the parral‐type greenhouse, while there was a reduction in market production at the third sampling. Peroxidation (malondialdehyde content and lipoxygenase activity) increased significantly at the third sampling, indicating the presence of oxidative stress caused by the rise in temperature, solar radiation and VPD. The ascorbate content, the activities of superoxide dismutase, catalase and ascorbate peroxidase and other stress indicators (proline and sucrose degradation) also increased at the third sampling. CONCLUSION: This study showed that conditions of higher environmental stress occurred at the third sampling and in the parral‐type greenhouse, leading to the accumulation of ascorbic acid in cherry tomato fruits and therefore to higher nutritional quality. Copyright © 2009 Society of Chemical Industry     

水杨酸缺失型突变体NahG和野生型番茄果实抗冷性的比较

本实验以番茄水杨酸(salicylic acid,SA)缺失型突变体(NahG)和野生型(wild type,WT)的采后果实为试材,于4?℃下贮藏28 d后观察番茄果实冷害症状,同时测定冷藏期间果实的冷害指数,游离脯氨酸含量,磷脂酶C(phospholipase C,PLC)、磷脂酶D(phospholipase D...     

Enhancement of Chilling Stress Tolerance of Tomato Fruit by Postharvest Brassinolide Treatment

Tomatoes, originally a tropical fruit, cannot easily be stored at low temperatures, due to the risk of chilling injury (CI). To develop an effective technique to reduce CI, the effects of treatment with 0, 3, and 6 μM brassinolide (BR) on chilling injury, electrolyte leakage (EL), contents of malondialdehyde (MDA) and proline, and activities of phospholipase D (PLD) and lipoxygenase (LOX) were investigated in tomato fruit stored at 1 °C for 21 days. Treatment with BR, especially at 6 μM, significantly alleviated chilling injury, reduced EL and MDA content, and increased proline content. Also, fruit treated with BR exhibited significantly lower PLD and LOX activities as compared with the control fruit. These results suggest that PLD and LOX are associated with the induction of CI in tomato fruit. BR might reduce CI by inhibiting PLD and LOX activities and by enhancing membrane integrity.     

MPR1 as a novel selection marker in Saccharomyces cerevisiae

L ‐Azetidine‐2‐carboxylic acid (AZC) is a toxic four‐membered ring analogue of L ‐proline that is transported into cells by proline transporters. AZC and L ‐proline in the cells are competitively incorporated into nascent proteins. When AZC is present in a minimum medium, misfolded proteins are synthesized in the cells, thereby inhibiting cell growth. The MPR1 gene has been isolated from the budding yeast Saccharomyces cerevisiae Σ1278b as a multicopy suppressor of AZC‐induced growth inhibition. MPR1 encodes a novel acetyltransferase that detoxifies AZC via N‐acetylation. Since MPR1 is absent in the laboratory strain of S. cerevisiae S288C, it could be a positive selection marker that confers AZC resistance in the S288C background strains. To examine the usefulness of MPR1, we constructed some plasmid vectors that harboured MPR1 under the control of various promoters and introduced them into the S288C‐derived strains. The expression of MPR1 conferred AZC resistance that was largely dependent on the expression level of MPR1. In an additional experiment, the galactose‐inducible MPR1 and ppr1⁺, the fission yeast Schizosaccharomyces pombe homologue of MPR1, were used for gene disruption by homologous recombination, and here AZC‐resistant colonies were also successfully selected. We concluded that our MPR1–AZC system provides a powerful tool for yeast transformation. Copyright © 2009 John Wiley & Sons, Ltd.     

SEQUENTIAL TREATMENTS OF HOT WATER AND MODIFIED ATMOSPHERE PACKAGING IN CHERRY TOMATOES

ABSTRACT

The effects of hot water treatment (HWT) and modified atmosphere packaging (MAP) on the storage and fruit quality of cherry tomatoes (Lycopersicon esculentum Mill. cvs. “Alona” and “Naomi”) were investigated. For this purpose, light‐red cherry tomato fruits were dipped in hot water (54C for 5 min) and subsequently stored in plastic film materials with various O₂ and CO₂ permeabilities. The cultivars used in the study were stored in a cold room at 5–7C and 90 ± 5% relative humidity (RH). The changing gas composition within the films and quality changes of the fruits were evaluated during the storage period. At the end of the study, HWT combined with MAP produced better results than MAP alone in both cultivars. Therefore, the HWT + MAP treatment proved effective with regard to fruit quality and delaying the maturity of cherry tomatoes during storage. HWT + 50 micropolyethylene (μPE) treatment produced the best result in the two cultivars at the end of the 28‐day storage with respect to the parameters evaluated in the study.

PRACTICAL APPLICATIONS

Tomato is considered a climacteric fruit, in which ripening is accompanied by a peak in respiration and a concomitant sharp increase in ethylene production, which accelerates quality loss through the physicochemical changes related to this process, such as softening and color evolution. Postharvest heating is a noncontaminating physical treatment that delays the ripening process, reduces chilling injury and controls the activity of pathogens. Because of these beneficial effects, heat treatments are currently used commercially for quality control of fresh products. Modified atmosphere packaging is another technique that has been used to prevent or retard postharvest fruit ripening and its associated biochemical and physiological changes by favorably altering the O₂ and CO₂ levels around the products. In recent years, the use of combined techniques in the postharvest handling of fresh products is increasing, and numerous authors have obtained good results using a combined treatment. Diseases have the potential to destroy the market value and utility of large amounts of fresh tomato annually. The present work evaluated a prestorage conditioning treatment to protect against these losses. The results will allow the long storage of cherry tomato, benefiting the growers, exporters, shippers and distributors of this horticultural product.

     

Degradation of N‐(1‐Deoxy‐d‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐xylulos‐1‐yl)proline using thermal treatment

The formation and degradation of N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)proline, derived from the secondary amine Maillard reaction in xylose‐amino acid model solutions, were detailed in this study. The identification and quantitative analysis of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline were carried out using high‐performance anion‐exchange chromatography and high‐performance liquid chromatography. The formation of intermediate and advanced products derived from N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline was also tested using an UV‐Vis spectrophotometer to gain a better comparing of the degradation process of the two important Maillard reaction products using thermal treatment. Results showed that the degradation of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine was more significant than N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline. Moreover, xylose was tested in the degradation products of both N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline, which indicated that the degradation of N‐substituted 1‐amino‐1‐deoxyketoses was a reversible reaction to form reducing sugar.     

Effects of 1‐methylcyclopropene on oxidative damage,phospholipases and chilling injury in loquat fruit

BACKGROUND: Low‐temperature storage is commonly used for loquat (Eriobotrya japonica Lindl.) fruit to inhibit decay and extend postharvest life, but it also increases the severity of chilling injury (CI) in red‐fleshed fruit. 1‐Methylcyclopropene (1‐MCP) has been used to reduce the development of CI in cold‐stored loquat. However, the effects of 1‐MCP on changes in antioxidant system and phospholipase activity and their relation to CI have not been investigated. The objective of this study was to determine whether the 1‐MCP‐induced modification in antioxidant system and phospholipase activity is linked to the reduced CI in cold‐stored loquat fruit. RESULTS: 1‐MCP treatment significantly alleviated CI in ‘Fuyang’ loquat fruit. The treatment markedly inhibited the accumulation of malondialdehyde, superoxide radicals and hydrogen peroxide and the increase in electrolyte leakage. In addition, 1‐MCP‐treated fruit exhibited significantly higher catalase activity and lower lipoxygenase (LOX) and phospholipase C (PLC) activities than control fruit during storage. CONCLUSION: These results suggest that LOX and PLC are associated with the induction of CI in loquat fruit. 1‐MCP might reduce CI by inhibiting LOX and PLC activities and alleviating oxidative damage. Copyright © 2009 Society of Chemical Industry     

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     

Arginine-rich coconut kernel diet influences nitric oxide synthase activity in alloxandiabetic rats

BACKGROUND: Coconut kernel protein (CKP) has been reported to contain significant amounts of L ‐arginine. Its potential effect on glucose homeostasis, possibly through the nitric oxide synthase (NO) pathway, was therefore investigated in alloxan‐induced diabetic rats. Diabetes was induced by a single intraperitoneal dose of alloxan (150 mg kg^?1 body weight). Experimental rats were grouped as follows: Group I, normal control; Group II, diabetic control; Group III, diabetic + CKP; Group IV, diabetic + L ‐arginine; Group V, diabetic + L ‐arginine + L ‐N^G‐Nitroarginine methyl ester (L ‐NAME). Purified CKP isolated from dried coconut kernel and L ‐arginine was administered to rats along with a semi‐synthetic diet for 45 days. L ‐NAME (0.5 mg kg^?1 body weight) was given to Group V animals. After the experimental period, serum glucose, insulin, activities of liver nitric oxide synthase and arginase, liver glycogen levels and histopathology of the pancreas were evaluated. RESULTS: Serum glucose, insulin and antioxidant enzyme activities and liver glycogen levels were found to be restored to basal levels in CKP‐fed rats. Decreased arginase and increased nitric oxide synthase (NOS) activities were found in CKP‐ and arginine‐fed rats. L ‐NAME treatment showed a partial effect on these parameters. Histopathology revealed that CKP and L ‐arginine feeding reduced the diabetes‐related pancreatic damage in treated rats compared to the diabetic control. CONCLUSION: The results observed in this study indicate that the potential antidiabetic activity of CKP may be through an arginine‐NO pathway leading to pancreatic beta cell regeneration. Copyright © 2012 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.     

Maturity‐dependent chilling tolerance regulated by the antioxidative capacity in postharvest cucumber (Cucumis sativus L.) fruits

BACKGROUND: The aim of the present study was to reveal the effect of fruit maturity on the chilling tolerance of cucumber (Cucumis sativus L.) fruit and the oxidative and antioxidative mechanisms involved. Chinese mini‐cucumber (cv. Hangcui‐1) fruits were harvested at four developmental stages: Immature (3–8 days after anthesis (DAA)), Mature (9–16 DAA), Breaker (17–22 DAA) and Yellow (35–40 DAA). All fruits were stored at 2 °C for 9 days and rewarmed at 20 °C for 2 days. RESULTS: The chilling injury index declined with advancing fruit maturity. High superoxide anion radical production rate and hydrogen peroxide content were observed in Immature fruits after cold storage and rewarming. Under chilling stress, superoxide dismutase showed an early response. Fruits at earlier maturity stages exhibited higher catalase, ascorbate peroxidase and monodehydroascorbate reductase activities and glutathione content as well as its redox state, and lower peroxidase, dehydroascorbate reductase and glutathione reductase activities and ascorbate content as well as its redox state. CONCLUSION: Fruits at the earlier developmental stage are more susceptible to chilling injury, which is related to increased oxidative stress. High peroxidase activity and ascorbate content and maintenance of the latter's redox state appear critical to the chilling tolerance of cucumber fruits at later developmental stages. © 2012 Society of Chemical Industry     

EFFECT OF WAX APPLICATION ON THE QUALITY,LYCOPENE CONTENT AND CHILLING INJURY OF TOMATO FRUIT

ABSTRACT

Waxed and nonwaxed mature green tomato fruits were stored at 12C (nonchilled) or 5C (chilled) for 5, 10, 15 and 20 days before being transferred to 22C for 3, 6, 9 and 12 days, were evaluated for weight loss, chemical composition, skin color, chilling injury (CI) index and pigment content. Waxed fruits showed a delay in weight loss, color development and ripening. The sensitivity of tomato fruit to CI was reduced in waxed fruits, which showed a delay in the appearance of symptoms. A delay in chlorophyll degradation and lycopene synthesis was observed as a result of the use of wax and low temperature. Waxing of tomato fruits allowed their storage at temperatures below critical reducing CI sensitivity and maintaining quality giving more time for marketing.

PRACTICAL APPLICATIONS

Nowadays, local tomato producers use wax on fruits as an everyday practice to carry postharvest fungicides and to improve brightness. They store tomato fruits at nonchilling temperature (12C) because lower temperatures would cause chilling injury and irregular ripening. In this way, it is interesting that waxing tomato fruits allow reducing their storage temperature, protecting them from chilling injury and maintaining their quality and correct color change and ripening; thereby producers and sellers have more days to position their fruits with no extra cost.     

Effect of cold‐shock treatment on chilling injury in mango (Mangifera indica L. cv. ‘Wacheng’) fruit

To investigate how cold shock may affect chilling injury in mango fruit (Mangifera indica L. cv. ‘Wacheng’), the fruit were treated for 3, 4 or 5 h at 0 °C, or treated for 8, 10 or 12 h at 4 °C, respectively, then transferred to 20 °C for 20 h prior to being stored at 2 °C, 85–95% RH. The chilling injury index of mango treated at 0 °C for 4 h was 59.7% lower than that of the control fruit directly stored at 2 °C, 85–95% RH. Some attributes were assayed in the fruit treated at 0 °C for 4 h. Ion leakage of the cold‐shock fruit at 0 °C for 4 h was 16% or 10% lower than that of the control on day 9 or day 12 of storage, respectively. Malondialdehyde content of the cold‐shocked fruit was 70% or 50% lower than that of the control on day 6 or day 12 of storage at 2 °C, respectively. Activities of catalase, ascorbate peroxidase, and contents of glutathione and phenolic compounds in the fruit during storage were all markedly enhanced by the cold‐shock treatment, whereas activities of superoxide dismutase, glutathione reductase and content of ascorbic acid in the mango were slightly influenced by the cold‐shock treatment. These results suggest that cold‐shock treatment may hold promise as an alternative approach to reduce chilling injury in mango fruit during cold storage. Copyright © 2006 Society of Chemical Industry     

Isolation and characterisation of a kallikrein-like enzyme from Agkistrodon halys pallas snake venom

BACKGROUND: Viper snake venoms contain a great variety of toxic proteins. These components mediate their toxicity by either stimulating or inhibiting the haemostatic system of human victims or experimental animals, resulting in common clinical complications of blood clotting or uncontrolled haemorrhage. Therefore it is deemed important to isolate the active component(s) from snake venom with kallikrein‐like activity. RESULTS: A kallikrein‐like proteinase of Agkistrodon halys pallas snake venom, designated AHP‐Ka, was purified by anion exchange chromatography and affinity chromatography. Physicochemical studies showed that the purified enzyme was a 34 kDa monomeric glycoprotein, the molecular weight of which decreased to 26 kDa after deglycosylation with peptide N‐glycosidase F (PNGase F). Sequence studies on the NH₂‐terminal region of the protein indicated that AHP‐Ka shared a high degree of sequence homology with other serine proteinases from snake venoms. AHP‐Ka showed high catalytic activity and kallikrein‐like activity on substrates such as arginine esterase BAEE and chromogenic H‐D‐Pro‐Phe‐Arg‐pNA·2HCl (S‐2302) and was inhibited by protease inhibitor phenylmethylsulfonyl fluoride (PMSF). CONCLUSION: The results showed that AHP‐Ka isolated from A. halys pallas snake venom and purified by anion exchange chromatography and affinity chromatography is in fact a kallikrein‐like enzyme. Copyright © 2011 Society of Chemical Industry