Red Ripe Stage Research Articles

Hydrophilic and lipophilic antioxidant activity changes during on-vine ripening of tomatoes (Lycopersicon esculentum Mill.)

Changes in antioxidant activity during the on-vine ripening of tomatoes (Lycopersicon esculentum) were studied at four different ripening stages (green, breaker, pink and red ripe). Hydrophilic and lipophilic antioxidant activities (HAA and LAA, respectively) were determined and their relationships to ascorbic acid, total phenols, lycopene and β-carotene contents were analysed. HAA and ascorbic acid remained practically unchanged, while the levels of aqueous phenols increased during ripening. The levels of ascorbic acid and HAA were strongly correlated (r=0.90, P<0.1). β-Carotene increased until breaker and pink stages, decreasing afterwards. In contrast, lycopene accumulated throughout the ripening period. The LAA followed the same pattern as lycopene and a good correlation was found (r=0.91, P<0.05). There was less difference between the measured and calculated LAA as the lycopene level increased, the discrepancy being lowest at the red-ripe stage, indicating the importance of lycopene as a lipophilic antioxidant in tomatoes.

Variations in germination and longevity of pepper (Capsicum annuum L.) seeds harvested at different stages of maturation

Pepper (Capsicum annuum L.) seeds of the cultivars Tatashe and Rodo, extracted from fruits sequentially harvested at different maturation stages, were tested for germinability (when freshly harvested) and longevity (over a period of about 17 weeks). Seed dry weight increased with fruit maturation and was maximum when the fruits turned red-ripe. Over-ripening of the fruits for 10 days on the mother plant did not result in a significant seed weight increase, signifying that the seeds were already fully filled when the fruits turned red-ripe. The seeds of the two cultivars started germinating as from 28 days after anthesis (DAA) and peaked at 71.5% and 40% for Tatashe and Rodo respectively, at 44 DAA. The viability of the seeds of Tatashe declined as storage progressed and the more mature the seeds were, the longer they survived. In Rodo, seed viability increased till the end of the storage period due to dormancy, which became progressively broken with age; seeds from more mature fruits survived better. In a second experiment, when fruits of Tatashe were harvested at the colour breaking, red-ripe and over-ripe stages, seed viability and longevity were best from over-ripe fruits.

Altered cell wall disassembly during ripening of Cnr tomato fruit: implications for cell adhesion and fruit softening.

The Cnr ( C olourless n on- r ipening) tomato ( Lycopersicon esculentum Mill.) mutant has an aberrant fruit-ripening phenotype in which fruit do not soften and have reduced cell adhesion between pericarp cells. Cell walls from Cnr fruit were analysed in order to assess the possible contribution of pectic polysaccharides to the non-softening and altered cell adhesion phenotype. Cell wall material (CWM) and solubilised fractions of mature green and red ripe fruit were analysed by chemical, enzymatic and immunochemical techniques. No major differences in CWM sugar composition were detected although differences were found in the solubility and composition of the pectic polysaccharides extracted from the CWM at both stages of development. In comparison with the wild type, the ripening-associated solubilisation of homogalacturonan-rich pectic polysaccharides was reduced in Cnr. The proportion of carbohydrate that was chelator-soluble was 50% less in Cnr cell walls at both the mature green and red ripe stages. Chelator-soluble material from ripe-stage Cnr was more susceptible to endo-polygalacturonase degradation than the corresponding material from wild-type fruit. In addition, cell walls from Cnr fruit contained larger amounts of galactosyl- and arabinosyl-containing polysaccharides that were tightly bound in the cell wall and could only be extracted with 4 M KOH, or remained in the insoluble residue. The complexity of the cell wall alterations that occur during fruit ripening and the significance of different extractable polymer pools from cell walls are discussed in relation to the Cnr phenotype.

The biosynthetic pathway for indole-3-acetic acid changes during tomato fruit development

Phytohormone metabolism during fruit ripening is critical to the controlof this developmental process, yet we know little about pathways for theproduction of many of these signaling compounds. Using stable isotope labelingin both an in vitro aseptic tomato fruit culture systemanddetached greenhouse-grown tomato fruit, we have shown by mass spectral analysisthat tomato uses the tryptophan-independent pathway to produce IAA fromanthranilate or indole. We also show that there is a developmental switch fromtryptophan utilization to tryptophan-independent production that occurs betweenmature green and red-ripe stages of fruit development. Moreover, this pathwayswitch does not appear to be associated with ripening per se in that fruit fromneverripe tomato plants also utilize the tryptophanindependent pathway.

Ripening-related changes in raspberry cell wall composition and structure

Cell walls were prepared from the fruit of two cultivars of raspberry at three stages of ripening; green, white and red (ripe). The cultivars, Glen Clova and Glen Prosen, are subjectively classified, at harvest by growers, as soft and firm fruit, respectively. The cell walls were analysed for neutral sugar composition, uronic acid content, degree of methyl esterification, lignin and ferulic acid-derived dehydrodimers. Solid-state 13C NMR and diffuse reflectance infrared (DRIFT) spectra were acquired for the cell wall residues. For both cultivars the progression from green to white produced minimal changes, save for a reduction in pectin. NMR analyses indicated that the solubilized pectin was acetylated. Progression to the red (ripe) stage, in both cultivars, was accompanied by a reduction in the ordered cellulose and a dramatic reduction in pectin content and the degree of methyl-esterification. Significantly, the softer fruit (Glen Clova) exhibited greater reductions in both parameters, implicating increased pectin hydrolysis, as one of the main factors contributing to the difference in firmness between the cultivars. A relative increase in cell wall-associated protein was seen at the red stage. The nature and function of the protein(s) are, as yet unknown.

Endo‐β‐mannanase is present in an inactive form in ripening tomato fruits of the cultivar Walter

Fruits of the tomato cultivar Walter undergo normal development to the red-ripe stage but, unlike those of the cultivar Trust, they do not produce any active endo-beta-mannanase. Reasons for this failure to produce the enzyme were sought. The cv. Walter contains genes for endo-beta-mannanase, as shown by Southern blot analysis, and transcripts for the enzyme are present in ripening fruits, as revealed using Northern hybridization. Moreover, the enzyme protein is detectable by Western blots using an endo-beta-mannanase-specific antibody from tomato. In addition, the inactive enzyme is localized appropriately in the wall regions of the outer layers of the fruit (skin and outer pericarp). Mixing inactive fruit extracts of cv. Walter, in excess, with extracts from cv. Trust fruits, which contain active enzyme, leads to an increase rather than a reduction in enzyme activity, showing that there are no inhibitors of endo-beta-mannanase in cv. Walter fruits. Similar results were obtained with fruits of the tomato cv. Heinz 1439. In contrast to the situation in fruits, the seeds of both cvs Walter and Heinz 1439 produce active enzyme, especially following germination.

Fruit-localized phytochromes regulate lycopene accumulation independently of ethylene production in tomato.

We show that phytochromes modulate differentially various facets of light-induced ripening of tomato fruit (Solanum lycopersicum L.). Northern analysis demonstrated that phytochrome A mRNA in fruit accumulates 11.4-fold during ripening. Spectroradiometric measurement of pericarp tissues revealed that the red to far-red ratio increases 4-fold in pericarp tissues during ripening from the immature-green to the red-ripe stage. Brief red-light treatment of harvested mature-green fruit stimulated lycopene accumulation 2. 3-fold during fruit development. This red-light-induced lycopene accumulation was reversed by subsequent treatment with far-red light, establishing that light-induced accumulation of lycopene in tomato is regulated by fruit-localized phytochromes. Red-light and red-light/far-red-light treatments during ripening did not influence ethylene production, indicating that the biosynthesis of this ripening hormone in these tissues is not regulated by fruit-localized phytochromes. Compression analysis of fruit treated with red light or red/far-red light indicated that phytochromes do not regulate the rate or extent of pericarp softening during ripening. Moreover, treatments with red or red/far-red light did not alter the concentrations of citrate, malate, fructose, glucose, or sucrose in fruit. These results are consistent with two conclusions: (a) fruit-localized phytochromes regulate light-induced lycopene accumulation independently of ethylene biosynthesis; and (b) fruit-localized phytochromes are not global regulators of ripening, but instead regulate one or more specific components of this developmental process.

Effect of time of harvest, stage of fruit ripening, and post-harvest ripening on seed yield and germinability of local garden egg (&lt;i&gt;Solanum gilo Radii&lt;/i&gt;)

Two cultivars of garden egg (Solanum gilo), Legon 1 and Nyaduahene, were used in the study. The first harvest was done 4 weeks after 50 per cent fruit set, followed by a second harvest, 4 weeks later. Seeds from three fruit maturity stages, mature white, yellow ripe and red ripe, were investigated. Seeds were extracted from half of the fruits harvested from each stage immediately after harvest while the other halves were stored at room temperature to ripen to the soft-red stage before seed extraction. Fruit weight in both cultivars decreased with plant age. Fruits harvested at the yellow-ripe stage produced the highest number of seeds per fruit. Fruits harvested at the mature white stage had the lowest seed yield. Seed yield was higher in the second harvest than in the first. Cultivar differences were observed in 1000-seed weight, but seed weight in both cultivars increased with fruit maturity. Post-harvest ripening to the soft-red stage increased the number of seeds extracted in fruits harvested at the mature-white stage as well as the 1000-seed weight in fruits harvested at the mature-white or yellow stages. Post-harvest ripening also improved the total percentage germination of seeds extracted from fruits harvested at the white or yellow stages, but decreased the percentage germination in seeds from fruits harvested at the red-ripe stage. Ghana Jnl agric Sci. Vol.32(2) 1999: 159-167

Evaluation of Tomato Varieties for Resistance to Alternaria Fruit Rot

Alternaria alternata (Fr.:Fr.) Keissl. (syn. A. tenuis Ness.) causes severe rot of tomato fruits and reduction in yield under field conditions in south Texas. Several fungicidal control measures have been tried against the disease and incorporation of genetic resistance has been found to be economically feasible. The objective of this study was to evaluate resistance and susceptibility of fruits of different tomato cultivars to Alternaria rot. Twenty-five tomato varieties were grown in the field in a randomized complete-block design. Subsequently, the plants were inoculated two times at mature-green stage with A. alternata conidia suspension (104 per ml) to promote moderate to severe fruit rot epidemics. Uninoculated fruits served as controls. Fruit rot incidence was measured by recording numbers of rotted fruit/plant per block and disease severity were rated on a scale of 0 to 3 at red-ripe stage. Three tomato varieties `Celebrity', `Golden Boy', and `Colonial' had little or no fruit rot symptoms, with disease severity indices of less than 1.0. These varieties were regarded as resistant. The tomato varieties `Duke', `GH 761', `Quick-Pick', and `Heat-wave' had disease severity ratings greater 1.5 and were regarded as relatively resistant. The remaining tomato varieties with disease severity ratings greater than 1.5 were regarded as susceptible.

Effect of Harvest Maturity and Ethylene Gassing on Tomato Flavor Volatile Concentrations

Tomato fruit (Lycopersicon esculentum Mill.) cvs. Solar Set and Olympic were harvested at three maturity stages: green (stage 1, USDA color classification) gassed with 100 ppm ethylene, green not gassed, turning (stage 4), and red-ripe (stage 6). After ripening at 21 °C, the fruit were homogenized with CaCl2 and analyzed for important flavor volatile compounds. For `Solar Set', acetone, ethanol, 1-penten-3-one, hexanal, and trans-2-heptenal were significantly higher in red-harvested fruit, while 2+3-methylbutanol, and trans-2-hexenal were higher in green-harvested fruit. trans-2-Hexenal was at higher levels in green-harvested fruit not gassed compared to those that were gassed for `Solar Set'. `Olympic' fruit followed similar trends for harvest maturity and gassing, but there were fewer significant differences in volatile levels. Using a multivariate discriminant pattern recognition procedure, red fruit were separated from turning and green-harvested fruit, while green-gassed separated from non-gassed based on the aroma volatile profile within each cultivar.

Heat Treatment of Mature-green Tomatoes: Differential Effects of Ethylene and Partial Ripening

Mature-green `Sunbeam' tomatoes (Lycopersicon esculentum Mill.) were treated in varying order with C2H4, 42 °C water for 1 hour, 38 °C air for 2days, held 2 days at 20 °C (partial ripening), or not treated and then stored at 2 °C (chilled) for 14 days before ripening at 20 °C. Heat-treated fruit stored at 2 °C and transferred to 20 °C ripened normally, while 63% of nonheated fruit decayed before reaching the red-ripe stage. Partially ripened fruit developed more chilling injury, were firmer, were lighter, and were less red in color than fruit not partially ripened. Lycopene content and internal quality characteristics of fruit were similar at the red-ripe stage irrespective of sequence of C2H4 exposure, heat treatment, or a partial ripening period. Of the 15 flavor volatiles analyzed, 10 were reduced by storage at 2 °C, Exposure to C2H4 before the air heat treatment reduced the levels of four volatiles, while C2H4 application either before or after the water heat treatment had no effect on flavor volatiles. Two volatiles were decreased and two were increased by partial vipening, Storage at 2 °C decreased the level of cholesterol and increased levels of campesterol and isofucosterol in the free sterol pool. Exposure to C2H4 before or following heat treatments, the method of heat treatment, and partial ripening had little effect on free sterols, steryl esters, steryl glycosides, or acylated steryl glycosides in the pericarp of red-ripe fruit. A shortor long-term heat treatment of mature-green tomatoes could permit storage at low temperatures with little loss in their ability to ripen normally, whereas partial ripening did not reduce chilling injury.

Evidence for 1-(Malonylamino)cyclopropane-1-carboxylic acid being the major conjugate of aminocyclopropane-1-carboxylic acid in tomato fruit

Tomato (Lycopersicon esculentum Miller) fruit discs fed with [2, 3-14C]1-aminocyclopropane-1-carboxylic acid (ACC) formed 1-malonyl-ACC (MACC) as the major conjugate of ACC in fruit throughout all ripening stages, from immature-green through the red-ripe stage. Another conjugate of ACC, gamma-glutamyl-ACC (GACC), was formed only in mature-green fruit in an amount about 10% of that of MACC; conjugation of ACC into GACC was not detected in fruits at other ripening stages. No GACC formation was observed from etiolated mung bean (Vigna radiata [L.] Wilczek) hypocotyls, etiolated common vetch (Vicia sativum L.) epicotyls, or pea (Pisum sativum L.) root tips, etiolated epicotyls, and green stem tissue, where active conversion of ACC into MACC was observed. GACC was, however, formed in vitro in extracts from fruit of all ripening stages. GACC formation in an extract from red fruit at pH 7.15 was only about 3% of that at pH 8.0, the pH at which most assays were run. Our present in vivo data support the previous contention that MACC is the major conjugate of ACC in plant tissues, whereas GACC is a minor, if any, conjugate of ACC. Thus, our data do not support the proposal that GACC formation could be more important than MACC formation in tomato fruit.

Galactosidases in tomato fruit ontogeny: decreased galactosidase activities in antisense ACC synthase fruit during ripening and reversal with exogenous ethylene

α- and β-galactosidase (α- and β-Gal) activities, firmness and pigment content were analysed in tomato (Lycopersicon esculentum Mill.) pericarp during fruit growth and ripening, comparing normal fruit with transgenic fruit containing an ACC-synthase antisense transgene. Normal and transgenic immature green fruit had similar temporal patterns of total α- and β-Gal activity. Immature 21-day-old fruit displayed 93% and 134% higher α- and β-Gal activity on a per gram fresh weight basis, respectively, than mature-green fruit. During ripening, normal fruit presented increasing levels of α- and β-Gal activity towards the red-ripe stage. β-Gal II was detected in mature-green tomatoes; it rose rapidly and reached maximum values at the red-ripe stage. In contrast, α- and β-Gal activity in antisense fruit decreased after reaching the breaker stage, and a low continuous level of activity was apparent between 54 and 108 days after anthesis. 48- to 108-day-old transgenic fruit showed constant basal levels of β-Gal II. There were no significant differences in enzyme activity between antisense attached and detached fruit. An exogenous ethylene treatment performed in transgenic tomatoes brought about a promotive effect on total α- and β-Gal activity in general and on β-Gal II in particular, thus suggesting a role for ethylene in de novo synthesis or activation of these enzymes. Softening, chlorophyll breakdown and lycopene biosynthesis were impaired in the antisense fruits, but the impairment was only complete for lycopene synthesis and all were reversed by applied ethylene. These results can be associated with the signal transduction pathways proposed to be operational during tomato ripening.

水分ストレスがミニトマト果実の発育と糖および窒素含量に及ぼす影響

Cherry tomato (Lycopersicon esculentum Mill. cv. Piko) plants were drip-irrigated at four soil moisture levels (pF 1.5, pF 2.0, pF 2.5 and pF 2.9) from the 17th day before fruits on the first cluster reached the red ripe stage. Under high water stress (pF 2.9), the total dry weight and water content of the plant decreased, compared to other treatments. However, the proportion of fruit dry weight per plant gradually increased proportionately to the pF, but the proportion of the leaf and root dry weight decreased. The total sugar content of the fruit increased as the pF value rose, but that of sucrose was lower than that of glucose and fructose under all of water conditions. Starch content in the fruit was equal and decreased during its ripening in all treatments. Although the water content of the fruit decreased with higher water stress, the difference in concentration among the four conditions was within 3% so that the sugar concentration was barely affected. Total nitrogen content and the nitrogen content in the water soluble protein under water stress at pF 2.9 were lower than thoes at pF 1.5 which suggests that the low nitrogen content may account for the high sugar content. We conclude that the optimum pF value ranges between pF 2.5 and 2.9, within which is optimum tomato fruit quality without any reduction in yield.

Characterisation of β-galactosidase isozymes of ripening peppers

Activity of β-galactosidase (EC 3.2.1.23) and isozymes of the New Mexican type pepper were assayed in ripening fruit and characterised in order to further understand the possible role this enzyme plays in fruit ripening. Total β-galactosidase activity increased in New Mexican type peppers (NM chile) as they ripened. To a lesser extent, xylosidase and β-glucosidase increased from the mature green stage to the turning stage of ripening and then decreased in the red ripe stage. Cation exchange chromatography indicated two prominent β-galactosidase peaks depending on stage of ripeness. In mature NM green chile, one large anionic, and in NM red chile, one large cationic peak was found. Isoelectric focusing-polyacrylamide gel electrophoresis (IEF-PAGE) separated one isozyme from mature green NM chile (pI 4.6) and an additional β-galactosidase isozyme as NM chile turned from green to red (pI 8.0). The cationic β-galactosidase isozyme from red NM chile extract had an apparent native-molecular weight of 51 kDa. The optimum pH for β-galactosidase activity in both red and green NM chile was between 3 and 4.5. Stable enzyme activity was observed from 25 to 50°C. β-Galactosidase from red NM chile had a K m of 0.87 mM and V max of 12.3 nKat, while the values for green NM chile β-galactosidase were 2.5 mM and 8.3 nKat. The heavy metal ions Ag 2+ and Hg 2+ inhibited β-galactosidase activity by 100% and 90%, respectively.

Molecular cloning of a ripening-specific lipoxygenase and its expression during wild-type and mutant tomato fruit development.

A 94-kD protein that accumulates predominately in tomato (Ly-copersicon esculentum) fruit during ripening was purified, and antibodies specific for the purified protein were used to isolate cDNA clones from a red-ripe fruit cDNA library. A sequence analysis of these cDNAs and cross-reactivity of the 94-kD-specific antibodies to the soybean lipoxygenase (LOX) L-1, L-2, and L-3 proteins and soybean LOX L-1-specific antibodies to the 94-kD protein identified it as a member of the LOX gene family. Maximum levels of the 94-kD LOX mRNA and protein are present in breaker to ripe and red-ripe stages, respectively. Expression of 94-kD LOX in different tissues from mature green and red-ripe tomato fruits was found to be greatest in the radial walls of ripe fruit, but immunocytolocalization using tissue printing suggests that the highest accumulation of its protein occurs in locular jelly. None of 94-kD LOX is expressed in nonripening mutant fruits of any age. Never-ripe mutant fruit accumulate the 94-kD LOX mRNA to levels similar to those obtained in wild-type fruit, but fail to accumulate the 94-kD LOX protein. Collectively, the results show that expression of 94-kD LOX is regulated by the ripening process, and ethylene may play a role in its protein accumulation.

Effect of a high-temperature stress on endo-β-mannanase and α- and β-galactosidase activities during tomato fruit ripening

Abstract Tomato fruit show physiological disorders when exposed to temperatures at or above 30 °C. It has been suggested that the α- and β-galactosidases (α- and β-Gal), as well as the endo-β-mannanase could play roles during fruit ripening. Their pattern of activities was followed in detached tomato fruit, and the degree of inhibition of the activity at high temperatures was evaluated. The potential resumption of the enzyme activity when fruits were transferred to a room-temperature environment was also studied. Mature-green fruits were incubated at: (a) 36 °C for 2 days, (b) 40 °C for 2 days, or (c) 40 °C for 2 days +36 °C for another 2 days. After heat treatments, fruits were transferred to a 21 °C dark environment. Control fruit were stored at 21 °C. In the control fruit, activity was higher for α-Gal than for β-Gal and revealed slightly increasing patterns toward the red-ripe stage. Endo-β-mannanase activity was not detected in mature-green tomatoes but appeared at the breaker stage and rose rapidly, reaching constant values at the red-ripe stage. The firmness and enzymatic activities of fruits initially treated at 36 °C for 2 days were similar to those of the control group. Galactosidase activity decreased in tomatoes incubated at 40 °C for 2 days; and in those whose heat treatment was extended another 2 days at 36 °C the α-and β-Gal reached a minimum of 1 5 and 1 25 , respectively, of the initial activity on the fourth day. The activity of the endo-β-mannanase could be detected only 6 days after the fruit had been transferred to a 21 °C environment and increased slowly up to 24% of that attained by the control group. α-Gal showed a low rate of recovery but β-Gal activity recovered after 16 days at 21 °C. Results could be associated with an active role of these enzymes on the fruit softening process.

Glutamic Acid and 5-Aminolevulinic Acid May Function as Precursors of System II Ethylene in Ripening Tomato Fruit

The ethylene biosynthetic pathway has been established as methionine (MET) to S-adenosylmethionine to 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene, and this pathway has been labeled System I. Another pathway to ethylene may exist during synthesis of massive amounts of ethylene, and this system has been labeled System II. Our objective was to evaluate the efficacy of several compounds as possible precursors of System II ethylene in ripening tomato fruit tissue. Discs of `Rutgers' tomato pericarp tissue at the mature green, pink, and red ripe stages were incubated continuously in 10, 25, or 40 mm solutions of MET, ACC, 5-aminolevulinic acid (ALA), homocysteine, glutamic acid (GLU), alpha-ketoglutarate, or citrate buffer (control). The ethylene production rate at 8-hour intervals during a 32-hour incubation period and free and conjugated ACC content at the end of the incubation period were quantified. Fruit discs at the mature green stage treated with MET and ACC exhibited increased ethylene production and increased free ACC content. These results confirmed the role of MET and ACC as the predominant precursors of ethylene during the early stages of fruit development in tomato (System I). At the pink stage (System II); however, ALA increased ethylene production by 75% and free ACC content by 46% over the control, and MET increased ethylene by 27% and free ACC content by 57% over the control. At the red ripe stage, ALA caused a 35% increase and GLU caused a 31% increase in ethylene production over the control. These results suggest that ALA and GLU may be metabolized to ethylene via an unknown pathway during tomato fruit ripening (System II).

Quality of Tomatoes Stored at Chilling Temperatures following Prestorage Heat Treatments and Partial Ripening

Mature green `Sunbeam' tomato fruit (Lycopersicon esculentum Mill.), were treated in varying order with C2H4, 42°C water for 60 minutes, 38°C air for 48 hours, partial ripening for 48 hours at 20°C, or not treated, and then stored at 2°C for 14 days before ripening at 20°C. Heat treated fruit stored at 2°C and transferred to 20°C ripened normally while 63% of nonheated fruit decayed before reaching red ripe. More chilling injury (CI) developed when C2H4 was applied following heat treatment rather than before. There was more CI in fruit that were 42°C water treated compared with the 38°C air treatment. Less CI developed on fruit that were partially ripened for 2 days at 20°C before a 42°C water treatment rather than following it. At red ripe, nonchilled fruit were firmer than chilled heat treated fruit. Fruit treated in 42°C water were firmer when the heat treatment was applied before the C2H4 treatment rather than following it. Chlorophyll and lycopene content and internal quality characteristics of fruit were similar at the red ripe stage irrespective of C2H4 or heat treatment. Chilling and heat treatments reduced some of the 15 flavor volatiles analyzed. Volatile levels were lower in fruit treated with C2H4 before heat treatment compared with fruit treated with C2H4 following heat treatment. Prestorage heat treatments could allow for storage of mature green tomatoes at low temperatures with little loss in their ability to ripen normally.

Nondestructive Quality Screening of Green Tomatoes Using Ethylene Gas

The effects of prolonged ethylene exposure on external and internal quality parameters of tomato fruits were studied in order to explore the feasibility of its use as a nondestructive technique for screening immature and inferior quality fruit. `Agriset' and `CPT-5' tomatoes were hand harvested at Stage 1 (green) and held at 20°C and 50 ppm ethylene for 1-7 days. Each 24 hours, fruits reaching Stage 2 (breaker) were removed from C2H4 and transferred to 20°C air for subsequent ripening. Tomatoes were considered at edible maturity upon reaching full red-ripe stage and 4 mm deformation and final quality parameters were determined. For both cultivars, fruits which required prolonged C2H4 exposure to reach Stage 2 had lower overall visual appearance. `Agriset' tomatoes which required short exposure times to C2H4 (1 to 3 days) had somewhat higher quality than those requiring prolonged times (4 or 5 days). Days to reach edible maturity were 9.5 and 7.7, respectively. For the short exposure times, peel color was more intense (higher chroma value), while soluble solids content and total sugars were significantly higher (P = 0.05). Quality of `CPT-5' tomatoes was not adversely affected until requiring 6 or 7 days exposure to C2H4. Days to reach edible maturity decreased from an average of 12.5 to 11.0 for 1 to 5 or for 6 to 7 days exposure, respectively. For fruits requiring 7 days exposure, soluble solids content, total sugars and pH were significantly higher than for those reaching Stage 2 in fewer days. There were no significant differences in titratable acidity or ascorbic acid content for either cultivar.