Pink Stage Research Articles

The tomato debate: Postharvest-ripened or vine ripe has more antioxidant?

The vast majority of the tomato crop is harvested at mature green stage and ripened off of the plant for fresh market consumption. The other large amount of crop is harvested when the fruit has reached to fully mature red stage which is called “vine-ripened”. Here we attempt to answer and clarify if there is any difference between the antioxidant capacity of postharvest ripened and vine ripe tomatoes. Greenhouse grown tomatoes (cv. Newton) were harvested at four different ripening stages of unripe and vine ripe. Total phenolic (TP) contents and antioxidant capacity by the FRAP (ferric reducing antioxidant power) and TEAC (trolox equivalent antioxidant capacity) assays were performed on all ripening stages. Results of the present study demonstrated that tomato peel has significantly higher TP content and antioxidant capacity than the pulp tissues in all maturity stages tested. TP and antioxidant capacity of tomato fruits were affected during postharvest ripening process. If only pulp tissue considered, TAC of vine-ripened and postharvest ripened pink tomatoes has similar amount, but significantly higher content than mature green, breaker and turning maturity stages. If peel tissue measured, the mean separations identified three groups. Postharvest ripened mature green stage has the most TAC, followed by vine-ripened and pink stage. Postharvest breaker and turning stages have the least amount of TAC.

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.

Effect of Post Harvest Treatment on Stored Cherry Tomatoes

Cherry tomatoes are grown for its edible fruits, which can be consumed either fresh as a salad or after cooking as snacks. Cherry tomato is a store house of antioxidants such as Lycopene, ascorbic acid and phenolics.The study was conducted to undertake the effect of storage conditions on the post harvest quality of Cherry tomato cv. Marilee red (Lycopersicon esculentum Mill) harvested at pink stages. The experiment consisted of three post harvest treatments comprising fruits dipped in cold water for five minutes (control), fruits dipped in CaCl2 @ 2% and fruits dipped in acetic acid @ 5%. Fruits imposed with post harvest treatments were stored at ambient (temperature 25°C ± 2 and relative humidity approx. 75 ± 5%) and cold storage conditions (10°C ± 2). Physico-chemical changes recorded on 0, 2, 4, 6, 8, 10, 12, 14 days of storage. Lycopene, ascorbic acid and total sugar changes recorded on 0, 4, 9, 14 days of storage. The data on physical characteristics (firmness, taste, juiciness, decay, colour, gloss, uniformity, shrivel) were recorded. CaCl2 was the best treatment followed by control and acetic acid treatment. Significant differences observed among the chemical parameters due to various post harvest treatments and storage conditions. CaCl2 had highest ascorbic acid, lycopene content and had lowest PLW, moisture content. Acetic acid had highest PLW, titratable acidity, moisture content and lowest TSS, lycopene, total sugar content. Control had highest TSS, total sugar content, lowest titratable acidity and ascorbic acid content at ambient and cold temperatures. TSS and acidity contents increased rapidly initially, but started decreasing gradually afterwards in all storage treatment. CaCl2 was found highly effective in controlling storage loss as well as in maintaining the quality of the produce during storage. Although the ascorbic acid registered a decrease during storage, it could still contribute significantly towards the dietary intakes.

Effect of 1-methylcyclopropene (1-MCP) on reducing postharvest decay in tomatoes ( Solanum lycopersicum L.)

1-Methylcyclopropene (1-MCP as SmartFresh™ technology), an ethylene antagonist, was evaluated for affecting postharvest decay caused by Alternaria alternata, Botrytis cinerea, and Fusarium spp. on ‘Quality 23’ and ‘Seminis 35’ tomatoes at green or pink stages. Fruit with natural or artificial infection were subjected to 1-MCP at 0.0 μL L −1, 0.6 μL L −1 for 12 h, and 1.0 μL L −1 for 6 h. After 31–42 d storage, disease incidence and severity of individual diseases in 1-MCP treated fruit was significantly reduced compared with that of the untreated controls, except in one inoculated test for ‘Quality 23’ where severity of Alternaria rot in 1.0 μL L −1 treated fruit were significantly higher than that of the untreated control. Fruit treated with 1-MCP at 1.0 L −1 for 6 h also had significantly higher incidence of Alternaria rot in the inoculated ‘Quality 23’ and in the non-inoculated ‘Seminis 35’ compared with the fruit treated with 1-MCP at 0.6 μL L −1 for 12 h. The results of this study indicate that 1-MCP can reduce postharvest decay within a certain storage period.

Methyl jasmonate deficiency alters cellular metabolome, including the aminome of tomato (Solanum lycopersicum L.) fruit

Exogenous treatment with jasmonates (JA) has been shown to reduce the levels of polyamines in many plants. But the role of endogenous JA on polyamine biosynthesis or other cellular metabolites has thus far remained uninvestigated. We developed transgenic tomato (Solanum lycopersicum L.) having severely reduced methyl JA levels by silencing a fruit ripening-associated lipoxygenase (LOX), SlLoxB, using a truncated LOX gene under the control of the constitutive CaMV35S promoter. The LOX suppressed and MeJA-deficient fruits had lowered polyamine levels. Thus, these transgenic fruits were used as a plant model to evaluate the effects of reduced endogenous MeJA on cellular metabolites in ripening tomato fruits using NMR spectroscopy. During on-shelf ripening, transgenic fruits were significantly reduced in the content of 19 out of 30 metabolites examined, including Ile, Val, Ala, Thr, Asn Tyr, Glu, Gln, His, Phe, Trp, GABA, citrate, succinate, myo-inositol, unidentified compound B, nucleic acid compound Nucl1, choline, and trigonelline as compared to the wild-type azygous counterparts. A significant increase in β-glucose levels in transgenic fruits was observed at the pink stage. The transgenic fruits were equivalent to the wild type in lycopene level and chlorophyll degradation rates. Taken together, these results show that intracellular MeJA significantly regulates overall primary metabolism, especially aminome (amino acids and polyamines) of ripening fruits.

Vision-based judgment of tomato maturity under growth conditions

To determine the picking time of tomato and design the control strategy for the harvesting robot, the judgment of tomato maturity under natural conditions is required. Tomato samples were collected based on the fruit growth conditions which were divided into five different stages in this article: breakers, turning, pink, light-red, and red stages. The visible CCD camera VS-880HC was adopted to shoot visible images, while the near-infrared images at a wavelength of 810 nm were screened by MS- 3100 multi-spectral camera. The variations of samples, about color features, were analyzed. The tests indicated that with the changes in maturity, the hue-mean of tomato decreased and the red-green colordifference image mean increased. The standard deviations of the hue-mean and red-green image mean were the largest values for tomato in the pink stage, but the intensity mean of the near-infrared image for tomato in the pink stage had the lowest value. Hue-mean and red-green color-difference image mean can be used as a criterion for the judgment of tomato maturity, and the tests indicated that the redgreen mean method was more satisfactory than that of the hue-mean in the maturity recognition methods of tomato fruit with an accuracy of over 96%. The intermediate divisions of five different maturity stages, which were divided by red-green color-difference image mean, were 0, 23.5, 42.5 and 70. The judgment errors of the two methods are mainly caused by the recognition of tomatoes at the pink stage. Key words : Tomato, maturity, image, judgment.

Effect of 1-methylcyclopropene on tomato flavour components, shelf life and decay as influenced by harvest maturity and storage temperature

In Florida, tomatoes are harvested green (GR), which includes mature green (MG) and immature green (IG) fruits, and stored at low temperature (13 °C), resulting in poor flavour. Flavour improvement might be achieved if fruits were harvested with some colour (to eliminate IG fruits) and/or stored at higher temperature with the ripening inhibitor 1-methylcyclopropene (1-MCP). 'Florida 47' tomatoes were harvested at GR (MG + IG), breaker (BR), turning (TR) and pink (PK) stages, treated (+) or not (-) with 1-MCP and stored at 13 and/or 18 °C. 1-MCP treatment resulted in a gain of up to 6 days of shelf life depending on harvest maturity and storage temperature. Storage at 18 °C rather than 13 °C resulted in an increase in internal red colour, soluble solids (SS)/titratable acidity (TA) ratio and levels of many volatiles studied. The shelf life of BR (+) MCP fruits stored at 13 °C was similar to that of MG fruits. IG fruits exhibited lowest levels of SS, TA and ten volatiles compared with BR fruits. Harvesting tomatoes with colour (BR), thereby eliminating IG fruits, and treating with 1-MCP resulted in better quality with adequate shelf life.

Effect of Edible Coatings, Storage Time and Maturity Stage on Overall Quality of Tomato Fruits

Problem statement: Tomato (Lycopersicon esculentum Mill.) is one of the most widely consumed fresh vegetables in the world; however, its highly perishable nature limits its postharvest life. Major losses in tomato quality and quantity occur between harvest and consumption. Therefore, the application of new technologies to extend the postharvest life of this commodity is needed. The use of edible coatings appears to be a good alternative. Approach: We evaluated the effect of carnauba and mineral oil coatings on the postharvest quality of tomato fruits (cv. “Grandela”). Stafresh 2505™ (carnauba) and Stafresh 151™ (mineral oil) coatings were applied on fresh tomatoes at two maturity stages (breaker and pink). The quality of tomatoes was evaluated periodically at 0, 5, 10, 15, 21 and 28 days of storage at 10°C, plus 2 days at 20°C. For respiration rate analysis, tomatoes were kept at 20°C for 16 days. Results: At the beginning of the study, CO2 production was reduced by 38 and 46% when applying the mineral oil coating on breaker and pink tomatoes, respectively. In addition, early during the study, the mineral oil coating showed suppression of ethylene biosynthesis at both maturity stages. Both coatings reduced 30% PG activity of tomato tissue. At the end of storage, mineral oil coatings delayed color changes and reduced weight losses for up 70 and 46% at the breaker and pink stages, respectively. Conclusion/Recommendations: Respiration rate, color, weight loss and enzyme activity were positively affected by mineral oil coating at both maturity stages. No effects on firmness, titratable acidity and pH were found by the coating application. We concluded that mineral oil coating could be a good alternative to preserve the quality and extend the postharvest life of tomato fruit.

EFFECTS OF MODIFIED ATMOSPHERE PACKAGING ON POSTHARVEST QUALITY AND STORAGE OF MATURE GREEN AND PINK TOMATOES

The effects of modified atmosphere packaging (MAP) on storage and postharvest quality of F 1 hybrid tomatoes (Lycopersicon esculentum Mill. 'Zorro') were investigated. Tomatoes were harvested at mature green and pink stages and packed with Xtend ® bags. Air stored fruits were considered as control. All samples were stored at 12°C with 90% RH for 35 days. Weight loss, elasticity, skin color, ethylene production, lycopene, polygalactronase (PG) activity and decay parameters were investigated with intervals of 7 days. At the end of the storage, MAP of either mature green or pink fruits reduced the weight loss and decay. Among mature green tomatoes stored in MAP, the amount of decayed fruit was 5.88%, while this level for control fruits was 19.61%. MAP also delayed the increase of ethylene emission rate (detected by GC) and polygalactronase activity and the higher elasticity obtained from MAP compared to control. At the end of the storage, elasticity values were significantly higher in fruits of both maturity stages stored in MAPs (69.50 and 56.13 shore for mature green and pink fruits, respectively) than those of the control groups (55.73 and 46.53 shore for mature green and pink stages, respectively). Furthermore MAP alleviated the increment of PG activities in fruits of both stages. Mature green fruit had lower weight loss, decay, lycopene accumulation, ethylene production values, whereas they had higher hue angle and elasticity values than pink fruits. The general qualities of MAP fruits were better than those of air stored fruits. Overall findings indicate that MAP was able to store mature green for 35 days without significant decreases in quality characteristics.

RESPONSE OF ‘GRANNY SMITH’ APPLE TREES TO FOLIAR TITANIUM SPRAYS UNDER CONDITIONS OF LOW SOIL AVAILABILITY OF IRON, MANGANESE, AND ZINC

The aim of the study was to examine impact of foliar titanium (Ti) sprays on vegetative and reproductive response of apple (Malus domestica Borkh.) trees under conditions of low soil availability of iron (Fe), manganese (Mn), and zinc (Zn). The experiment was conducted during 2005–2006 at a Experimental Station in Isparta region, Turkey, on mature ‘Granny Smith’ apple trees/M.9, planted at a spacing of 3.5 × 1.5 m, on fine-textured soil with neutral reaction, medium status of organic matter, high amounts of available phosphorus (P), potassium (K), and magnesium (Mg), and low availability of Fe, Mn, and Zn. The trees were sprayed with Ti-ascorbate at the green and pink bud stage, petal fall, and 3, 6, and 9 weeks after full bloom, at a rate of 3 g Ti ha−1 per spray. The efficiency of Ti sprays was compared to combined sprays of Fe, Mn, and Zn [chelated with ethylenediaminetetraacetic acid (EDTA)], applied at the same terms as Ti sprays, at rate of 36 g, 36 g and 24 g per spray, respectively. Trees unsprayed with Ti, Fe, Mn, and Zn served as the control. It was shown that summer leaf Ti concentrations of the trees untreated with Ti were high, varying from 34 to 36 mg kg−1 dry matter. Foliar Ti sprays increased leaf status of this nutrient but they had no effect on nutrition of essential macro- and microelements, tree vigor, and fruit yield. Mean apple weight, coloring, firmness, soluble solids concentration, and titratable acidity of fruit were not also influenced by Ti sprays. Foliar sprays of Fe, Mn, and Zn improved leaf status of nitrogen (N), Mg, Fe, Mn, and Zn; leaves of the trees sprayed with those micronutrients were also greener, and contained more Fe2+ than those of the control plants. Combined sprays of Fe, Mn, and Zn improved tree vigor and fruit yield.

Mechanical String Thinner Reduces Crop Load at Variable Stages of Bloom Development of Peach and Nectarine Trees

Thinning of blossoms or fruitlets is a labor-intensive requirement in the production of peach and nectarine (Prunus persica) fruit of optimum size and quality. Prior research conducted by the authors on string blossom thinners for managing peach tree crop load demonstrated that this new technology reduces labor requirement and improves fruit size. The research reported in the current article was conducted over 2 years on ‘Sugar Giant’ peach and ‘Arctic Sweet’ nectarine to evaluate string blossom thinner efficacy at variable stages of bloom development ranging from pink to petal fall. Blossom removal at the pink stage of bloom development was lower than at other stages in 2008; however, a 150-rpm versus 120-rpm spindle rotation speed resulted in blossom removal similar to the 80% full bloom (FB) treatment in 2009. Blossom removal at the petal fall stage was similar to the open bloom stage with the exception of the 2009 ‘Sugar Giant’ trial, in which blossom removal was higher at 80% FB. Flower density and fruit set of the bloom stage compared with hand-thinned control treatments followed a similar trend with the exception that there were fewer differences in 2009 and in lower canopy regions. Follow-up hand thinning time was reduced by all string thinning/year combinations except ‘Arctic Sweet’ at pink in 2008 and 2009 and at petal fall in 2009. The best treatments reduced follow-up hand thinning time compared with green fruit hand thinning alone by 51% and 41% for ‘Sugar Giant’ and by 42% and 22% for ‘Arctic Sweet’ in Years 1 and 2, respectively. In 2008, the percentage of fruit in the “7.0 cm or greater” size category was increased by all bloom stage treatments in both cultivars. The 2009 size distribution of ‘Arctic Sweet’ fruit was unaffected, but the percentage of ‘Sugar Giant’ fruit in higher market value size categories was increased by the 80% FB and higher rpm pink treatments. Savings in hand thinning time and/or increases in fruit size in both years associated with the bloom stage treatments resulted in a net positive impact of $123/ha to 1368/ha compared with hand thinning alone.

Antioxidants and other chemical and physical characteristics of two strawberry cultivars at different ripeness stages

The present work evaluated the quality and antioxidant characteristics of ‘Osogrande’ and ‘Camino Real’ strawberries at different ripeness stages. Strawberries ( Fragaria x ananassa Duch.) were harvested, selected, graded according to ripeness (green, pink or 3/4 ripe and ripe) and evaluated for pH, total soluble solids, total titratable acidity, sugar/acid ratio, vitamin C, total phenolic compounds, total ellagic acid, total and individual anthocyanins and antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP). The highest total soluble solid content was found for pink (7.5° Brix) and ripe (7.9° Brix) ‘Osogrande’ strawberries. At pink stage, this cultivar showed higher amounts of total phenolics (2909.48 mg kg −1 FW) and total ellagic acid (454.16 mg kg −1 FW). Pink ‘Camino Real’ strawberries presented the highest content of vitamin C (528.55 mg kg −1 FW). Antioxidant activity was higher for ‘Osogrande’ cultivar, at green stage, according to DPPH (11.91 μmol BHT g −1 FW) and FRAP (36.75 μmol ferrous sulphate g −1 FW) assays and at ripe stage, only for DPPH assay (12.83 μmol BHT g −1 FW). Anthocyanins increased along ripening, with more elevated concentrations in ripe ‘Camino Real’ strawberries (292.9 mg kg −1 FW). Cyanindin-3-glucoside showed a higher concentration for the same treatment (17.23 mg kg −1 FW), which might contribute to a more redish color. Although ripe berries have a better flavor and are more appreciated, higher antioxidant contents and activities were observed at pink stage in which higher amounts of total phenolics, total ellagic acid and vitamin C were noticed for both cultivars.

Age-related susceptibility of strawberry leaves and berries to infection by Podosphaera aphanis

Powdery mildew, caused by Podosphaera aphanis, is a major disease of strawberry worldwide. The importance of the disease varies with production system (June bearing vs day neutral) which could be explained in part by the concurrent presence of susceptible leaves or berries and abundant airborne inoculum. Age-related susceptibility was studied by inoculating strawberry leaves and berries at different growth stages of the June bearing cultivar Jewel and the day neutral cultivar Seascape. On eight occasions in 2007, five plants of each cultivar were inoculated with dry conidia using a settling tower. There was a significant effect of leaf and berry growth stage on the susceptibility, which decreased exponentially as leaves or berries aged to reach almost zero when the leaves were completely expanded or the berries at the pink stage at the time of inoculation. The proportion of maximum mildew severity as a function of leaf or berry growth stage was predicted using non-parametric regression ( R 2 = 0.96–0.97). The predicted values were validated with data collected in fields or tunnels naturally infected by P. aphanis. There was a linear relation between predicted and observed proportion of maximum mildew severity ( R 2 = 0.95–0.99). The results of this study showed that timing fungicide sprays based on periods of high leaf and berry susceptibility should greatly improve management of strawberry powdery mildew.

EFFECT OF POLYETHYLENE THICKNESS, PHOTOPERIOD AND INITIAL STAGE AT HARVEST ON RIPENING OF TWO TOMATO (LYCOPERSICON ESCULENTUM MILL.) CULTIVARS

The effects of thickness of polyethylene (PE) packaging material, photoperiod and at-harvest stage of ripening on further ripening during storage at 28°C of fruit of the tomato cultivars 'Roma' and 'Beske' were studied. Fruit at the first four stages of ripening - mature-green, breaker, turning and pink - were separately packed in PE of 2.5, 5.0, 10 and 20 μm thickness, sealed and stored either under 12h naturally-alternating light and dark (LD) or complete darkness (D). Daily observation for progressive red colour development showed that photoperiod, packaging material and initial stage of ripening before packing and storage affected ripening. The ripening of mature-green fruit of 'Beske' tomatoes was independent of photoperiod, but decreased with thickness of PE packaging material. Ripening progressed in D more than in LD in breaker fruit. However, the difference was more pronounced in 'Roma' than in 'Beske' tomatoes. The least ripening in 'Roma' fruit was observed in 20 μm thick PE in LD while the greatest colour development was observed in 2.5 μm thick PE also initially at the breaker stage. There was no significant difference between effects of 10 μm and 20 μm thick PE material on 'Beske' fruit except at turning in both photoperiods and green in D. Fruit initially at turning did not show any significant effect of photoperiod in 'Roma' but did by day 6 in the local cultivar. Further ripening of pink fruit was unaffected by thickness of PE in 'Roma' fruit stored in D but had significant effect in LD. The same trend was observed in 'Beske' fruit. Generally, both photoperiod and thickness of packaging material had more significant effect at the early stages (mature-green and breaker) than at the turning and pink stages of ripening. There were significant interactions of all the factors in 'Roma' fruit but not in all the combinations in 'Beske' fruit.

Short communication. Effective pollination period in "RedChief" and "Golden Delicious" apples (Malus domestica Borkh)

Due to the significant variation in the initial fruit set of apples among seasons and producing regions of Chihuahua, Mexico, it is important to determine the cause(s). Apple fruit yield is strongly determined by the initial fruit set, which is the result of a series of physiological events, such as pollination, pollen tube growth, ovule longevity and fertilisation. During one or two seasons, in the two main apple-producing regions in the state of Chihuahua, México, the effective pollination period (EPP) was evaluated in "Golden Delicious", "RedChief Delicious" and "Golden Delicious Tardío", a regional mutant of Golden Delicious. Daily manual pollinations after the full pink stage were made with "Snow Drift" pollen to determine the EPP. The initial fruit set at 30 days after the last day of hand pollination was evaluated. A daily sampling of flowers was used to measure the pollen tube growth (average growth of 11.70 mm at 96 h) in the pistil and ovule viability in the ovary. The EPP lasted 6 days for RedChief Delicious, 4 days for Golden Delicious, and 10 days for Golden Delicious Tardío. The average ovule longevity of 63% seemed to be a limiting factor for Golden Delicious, leading to a reduced initial fruit set.

Chlorine dioxide gas from an aqueous solution: reduction of Salmonella in wounds on tomato fruit and movement to sinks in a treatment chamber.

Chlorine dioxide (ClO2) off-gassed from an aqueous solution and reacted incrementally with potassium iodide solutions (sinks). After 30 min, 45% of the initial dose was detected as chlorite ion in the sink, whereas 35% of the initial dose was still in the source. Aqueous solutions of ClO2 can be used as a source of ClO2 gas in various laboratory experiments involving treatment of fruits or vegetables. Movement from source to sink is continuous, which precludes the development of large headspace concentrations and the need for a tight chamber seal. When the source solution has dissipated, the chamber can be opened safely as there is little free ClO2 remaining in the headspace. In tests with whole, wound-inoculated tomato fruit, at both green and pink stages of ripeness, the control of Salmonella enterica serotype Typhimurium in wounds varied with the weight of gas used. The number of viable cells of Typhimurium recovered was reduced by > 5 log units when > or = 0.5 mg of ClO2 was applied to three pieces of fruit during a 2-h treatment.

The role of ABA in triggering ethylene biosynthesis and ripening of tomato fruit

In order to understand more details about the role of abscisic acid (ABA) in fruit ripening and senescence of tomato, two cDNAs (LeNCED1 and LeNCED2) which encode 9-cis-epoxycarotenoid dioxygenase (NCED) as a key enzyme in ABA biosynthesis, two cDNAs (LeACS2 and LeACS4) which encode 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, and one cDNA (LeACO1) which encodes ACC oxidase involved in ethylene biosynthesis were cloned from tomato fruit using a reverse transcription-PCR (RT-PCR) approach. The relationship between ABA and ethylene during ripening was also investigated. Among six sampling times in tomato fruits, the LeNCED1 gene was highly expressed only at the breaker stage when the ABA content becomes high. After this, the LeACS2, LeACS4, and LeACO1 genes were expressed with some delay. The change in pattern of ACO activity was in accordance with ethylene production reaching its peak at the pink stage. The maximum ABA content preceded ethylene production in both the seeds and the flesh. The peak value of ABA, ACC, and ACC oxidase activity, and ethylene production all started to increase earlier in seeds than in flesh tissues, although they occurred at different ripening stages. Exogenous ABA treatment increased the ABA content in both flesh and seed, inducing the expression of both ACS and ACO genes, and promoting ethylene synthesis and fruit ripening, while treatment with fluridone or nordihydroguaiaretic acid (NDGA) inhibited them, delaying fruit ripening and softening. Based on the results obtained in this study, it was concluded that LeNCED1 initiates ABA biosynthesis at the onset of fruit ripening, and might act as an original inducer, and ABA accumulation might play a key role in the regulation of ripeness and senescence of tomato fruit.

The influence of light and maturity on fruit quality and flavonoid content of red raspberries

The effects of various fruit maturities and different light intensities on berry fruit quality, antioxidant capacity and phytonutrient levels in red raspberries ( Rubus ideaus L.) were determined. At harvest, immature berries contained significantly lower levels of sugars and acids than ripe berries. When berries were harvested at 5% or 20% maturity, they never developed the levels of soluble solids content (SSC) and titratable acid (TA) values observed in ripe berries at harvest. However, fruit harvested at 50% or more advanced maturity had the capacity of attaining comparable levels of SSC, TA and sugars as those harvested at 100% maturity. When 5% and 20% berries were stored under light, higher level of SSC and lower levels of TA values were observed than those kept in the dark. However, light condition showed little effect in 50% and 80% maturity fruit after 4 days at 24/16 °C (day/night). Ripe raspberries (100%) had stronger antioxidant activities and higher total anthocyanin content when compared with the pink stage (50% maturity). Fruit harvested at greener stages (5% and 20%) also consistently showed higher antioxidant activities and total phenolics than those harvested at 50%. Cyanindin-based anthocyanins increased during postharvest period. On the other hand, other polyphenols such as ellagic acid, quercetin 3-glucoside, quercetin derivative, and kaempferol 3-glucuronide were initially present at high levels but decreased drastically during storage. Red raspberries harvested at different developmental stages continued their development during storage even under the dark conditions. The antioxidant activity of red raspberries was directly related to the total amount of phenolics and flavonoids. Results of this study indicate that red raspberries harvested at 50% or more advanced maturity could develop comparable quality and antioxidant levels as those harvested at full maturity.

Studies with Crisp-textured Blueberries

Over the past two decades, selections that produce crisp-textured blueberries have been noted by breeders. Research was conducted to determine how these selections differ from standard cultivars. Four blueberry clones with crisp texture were compared, using firmness, with 94 advanced selections from the University of Florida blueberry breeding program. The clones, tested for berry firmness with an Instron machine, produced a normal distribution. The crisp clones were at the high end of the distribution, but were not qualitatively different from other firm-fruited selections. Firmness was tested during final stages of berry development to determine if crisp clones softened more slowly than standard cultivars. In both 2003 and 2004, firmness decreased greatly from the white to pink stages of development, with slower loss of firmness thereafter. Crisp and commercial clones were similar in the timing of firmness loss. Berries from six crisp clones and four firm commercial cultivars were subjected to shear cell tests to see if the two groups could be distinguished. Shear cell tests from early and late harvests in the same year showed good agreement. Three of the four crisp clones were much higher in shear force than the other clones tested. A consumer sensory panel was conducted to determine if the average person could distinguish between the berries of crisp and standard cultivars. Ninety-five subjects were given two samples each of crisp and non-crisp blueberries, and asked to designate the one sample they thought the most crisp. Seventy-five subjects chose one of the two crisp clones and 20 chose one of the standard clones. This research indicates that crisp texture in blueberry exists and is recognizable and repeatable, but is difficult to objectively define.

Physiological changes in boysenberry fruit during growth and ripening

SummaryBoysenberries (Rubus hybrid) were harvested at five developmental stages (green, “turning”, pink, red and purple) to study changes associated with flavour, colour and firmness, with a particular focus on the different enzymes involved in chlorophyll degradation or cell wall degradation. The level of reducing and non-reducing sugars increased 109- and 52-fold, respectively, between the “turning” and the purple stage. Titratable acidity increased by 84% between the green and the pink stage, but dropped by 41% between the red stage and full ripening. Total phenols displayed their highest values in green and “turning” fruit. Chlorophyll a and b degradation occurred mainly during the early stages of development, and was paralleled by a 2.3-fold increase in chlorophyllase activity and a 5-fold increase in Mg-dechelatase activity between the green and the red stages. Chlorophyll peroxidase activity was high at the green stage, but did not change significantly after the “turning” stage. This is the first report on the activity of chlorophyll-degrading enzymes in Rubus spp. fruits. Anthocyanins increased 11-fold between the “turning” and the pink stages, and an additional eight-fold between the pink and the purple stages. Fruit firmness decreased noticeably during ripening, with a concomitant 10.75-fold increase in polygalacturonase activity, beginning at the “turning” stage. Endo- -1,4-glucanase and -galactosidase activities rose 9.2- and 6.7-fold, respectively, after the pink stage and paralleled the major softening process taking place between the pink and purple stages, when fruit firmness decreased from 3.83 N to 0.29 N. Pectin methylesterase activity was high in pink and red fruit, but decreased by 21% as the fruit turned from red to purple. This is the first report on cell wall enzyme activities whose combined action might be required for the breakdown of natural cell wall substrates during ripening in boysenberry, as happens in other soft fruits.