Changes In Fruit Firmness Research Articles

Changes in fruit firmness, cell wall composition and cell wall degrading enzymes in postharvest blueberries during storage

Blueberries are now the second most economically important soft fruit. However, they are highly perishable and susceptible to rapid spoilage. One of the main factors limiting postharvest life of blueberries is softening. The changes of fruit firmness, cell wall degrading enzymes and cell wall composition of ‘Brilliant’ blueberry (Vaccinium ashei cv. Brilliant) were investigated in this study. The results showed fruit firmness declined concomitantly with the increase of the content of water soluble pectin (WSP) during storage paralleled by a decreasing amount of sodium carbonate soluble pectin (SSP), cellulose and hemicellulose. Blueberries stored at low temperature (5°C) maintained higher fruit firmness than those stored at 10°C, which was due to the lower WSP content and higher contents of SSP, cellulose and hemicellulose. Meanwhile, the lower activities of cell wall degrading enzymes such as polygalacturonase, cellulase, β-galactosidase and α-mannosidase in blueberries at 5°C were associated with greater fruit firmness and lower WSP content as compared to those in fruit stored at 10°C.

Development of Edible Coating for Shelf Life Extension of Guava

Guava is economically important fruit which occupies a prominent position among fruit crops grown in Sri Lanka. Reported post harvest losses of guava were 46%. The study was carried out to find out suitable coating formula for shelf life extension of guava. The fruits were harvested the maturity at colour break change from green to scant yellow. Medium size fruits were selected while discarding disease and damaged fruits. Three different concentrations of cassava starch (1%, 2%, 3%) with 1% sunflower oil and Rice bran (1%, 2%, 3%) with 1% sunflower oil + 1% Bee wax were used for treatments and stored under ambient condition (280C-30 0C, 55%-60% RH), and quality evaluation was done to find out suitable concentration of cassawa starch and rice bran along with other constituents. 2% cassava starch+1% sunflower oil; 2% Rice bran +1% sunflower oil + 1% Bee wax were selected as better performed treatments in retaining the overall quality as it caused minimum changes in fruit Firmness, Titratable acidity, Reducing sugars, Total soluble solids (TSS). Generally, all treatments caused significant (P<0.05) decrease in fruit firmness and pectin content.

Use of a palladium catalyst to improve the capacity of activated carbon to absorb ethylene, and its effect on tomato ripening

The aims of this work were to study the ethylene adsorption capacity of different types and masses of activated carbon, to predict the performance of the ethylene adsorption process, to improve the removal of ethylene by impregnating granular activated carbon (GAC) with palladium, and to analyse the effect of this product on the removal of ethylene released from tomatoes. In an in vitro system, both GAC and powdered activated carbon (PAC) effectively absorbed exogenous ethylene; GAC was the most effective. Maximum adsorption was achieved with carbon masses of 1.25 g L-1 or greater. The best model describing the adsorption of ethylene by GAC was the Langmuir isotherm. To increase ethylene removal, a system involving an adsorbent (GAC) and a catalyst (1% palladium) was developed. This was tested in an in vivo experiment involving the removal of ethylene produced by three tomato cultivars inside sealed jars. Ethylene removal led to a delay in tomato ripening; smaller changes in fruit firmness and colour were observed compared to controls. This system could provide a useful way of eliminating ethylene from storage areas and thus maintaining tomato fruit quality, which can be negatively affected by ethylene

Prediction of postharvest dry matter, soluble solids content, firmness and acidity in apples (cv. Elshof) using NMR and NIR spectroscopy: a comparative study

Dry matter (DM), soluble solids content (SSC), firmness and acidity by proton nuclear magnetic resonance (NMR) T2 relaxometry and near infrared (NIR) spectroscopy were investigated on a total of 390 apples (cv. Elshof). The fruit came from four different pre- or postharvest treatments and covered a large range of DM (11.4–20.0 %) and SSC values (10.5–18.3 °Brix). NIR was superior in predicting DM (R 2 = 0.82) and SSC (R 2 = 0.80), compared to NMR (R 2 = 0.50 and R 2 = 0.58). However, NMR relaxometry was able to detect multiple water populations assigned to different water pools in the apples and variation in the water distribution between different pre- and postharvest treatments. Differences in the mobility of the vacuole water (population T24) were consistent with changes in fruit firmness. In conclusion, even though NIR is superior in predicting DM and SSC, NMR provides useful information about the intrinsic water state and its distribution in the fruit.

A new descriptive method for fruit firmness changes with various softening patterns of kiwifruit

We have proposed a new interpretation of fruit softening. This was accomplished by generating a hypothesis that probabilities of decay of fruit structure obey the Weibull probabilistic model that has been used in the field of reliability engineering. The elasticity of individual kiwifruit after harvest was continually and nondestructively measured until decomposition by using a laser Doppler vibrometer. The obtained decreasing pattern of elasticity of individual fruit was complex, diverse, and inhomogeneous. Nonetheless, it was satisfactorily explained by a tandem combination of 2 Weibull models involving 4 types of parameters: “shape” related to probability; “scale,” to velocity of decay; “location,” to time lag; and “mixing ratio,” to contribution of the 2 models. Averages of location, shape, and mixing ratio parameters obtained by the measurement of 33 fruit were significantly different between the 2 models, but the scale parameter was not. The results suggested that the complex softening patterns of individual kiwifruit could be described using the tandem model of Weibull distribution, and that the softening process of kiwifruit consisted of at least 2 independent decay phases that are characterized by 2 of 5 parameters: location and mixing ratio. Commencement of the first decay phase could be caused by ethylene treatment after harvest, and the second one spontaneously triggered after a certain time lag.

Effects of harvesting time on fruit quality and internal browning of ‘Wonhuwang’ pear during cold storage

Average fruit weight, seed browning, flesh firmness, total soluble solids, internal browning, and skin blackening were used to determine the optimum harvesting time of ‘Wonhuwang’ pear. Pears for storage were picked three times at 5-day intervals before, during, and after estimated optimum harvesting date. Average fruit weight and seed browning degree were calculated at each picking time. Quality changes, internal browning, and skin blackening were employed to estimate the optimum harvest date. It was found that fruit quality parameters both at harvest and after storage depended on the stage of ripeness at which the pears were picked. Pears harvested earliest (H1) had the highest firmness both before and after storage and lost less percentage of their firmness during storage. The latest picked pears (H3) showed higher total soluble solids value and serious internal browning and skin blackening due to their over ripeness. Pears picked on the 15th of August (H2) had higher firmness and total soluble solids, lower extent of internal browning, and no skin blackening. Based on the changes in fruit firmness and physiologic disorder during ripening and storage, the optimal harvesting time for ‘Wonhuwang’ pear in Shijiazhuang area is around the 15th of August.

Softening and cell wall metabolism in late-season peach in response to controlled atmosphere and 1-MCP treatment

SummarySoftening of peach (Prunus persica L. Batsch) fruit is generally rapid at ambient temperature, which limits considerably the commercial life of the produce. Modifications in the cell wall are believed to underlie changes in fruit firmness and texture. In this work, the effects of controlled atmosphere (CA) storage and 1-methylcyclopropene (1-MCP) on cell wall composition and on the activities of some cell wall-modifying enzymes were assessed in ‘Tardibelle’ fruit, a late-season, melting-flesh peach cultivar. CA storage and 1-MCP treatment applied separately were effective in delaying the softening of ‘Tardibelle’ peach during shelf-life at 20ºC following cold storage, apparently through different mechanisms. CA storage partially inhibited the activities of some pectolytic enzymes and increased the content of pectic polysaccharides, possibly related to delayed softening. 1-MCP treatment caused increased pectin methylesterase activity, but other pectolytic enzymes were inhibited, resulting in an enrichment of chelate-soluble pectin in the cell walls. In contrast, a combined treatment (i.e., CA plus 1-MCP) was unsatisfactory for retaining fruit firmness, apparently due to the extensive degradation of pectin.

Molecular characterization and differential expression of β-1,3-glucanase during ripening in banana fruit in response to ethylene, auxin, ABA, wounding, cold and light–dark cycles

beta-1,3-Glucanases (E.C. 3.2.1.39) are widely distributed enzyme among bacteria, fungi, and higher plants. Analyses of accumulation levels of beta-1,3-glucanase protein in various tissues in banana have clearly indicated abundance of beta-1,3-glucanase protein accumulation in ripe pulp tissue. After cloning of beta-1,3-glucanase from banana pulp (cultivar Cavendish), we have carried out an in silico analysis to investigate the sequential, structural, and phylogenetic characteristics of the putative banana beta-1,3-glucanase protein. As like other ripening specific genes, beta-1,3-glucanase is regulated in response to a wide variety of factors. Therefore, we have analyzed the transcript accumulation pattern and protein levels of beta-1,3-glucanase in response to ethylene, auxin, ABA, wounding and, low temperature in preclimacteric banana fruit. Expression profile analyses have indicated that whereas exogenous application of ethylene strongly stimulated beta-1,3-glucanase transcript accumulation, ABA partially induced the expression of the gene. On the other hand, wound treatment did not induce beta-1,3-glucanase expression. Conversely, auxin and cold treatment negatively regulated beta-1,3-glucanase gene expression and thus inhibited glucanase activity. In addition, beta-1,3-glucanase transcript level was markedly decreased by constant exposure to white light. Protein level and enzymatic activity of beta-1,3-glucanase were substantially increased with considerable decrease in fruit firmness by ethylene treatment and reduced exposure to white light conditions as compared with other treatments. Together, the overall study of beta-1,3-glucanase expression pattern, glucanase activity, and changes in fruit firmness during ripening in various conditions suggest the possible physiological function of beta-1,3-glucanase in fruit pulp softening.

CELL WALL-MODIFYING ENZYME ACTIVITIES AFTER CONTROLLED ATMOSPHERE STORAGE OF CALCIUM-TREATED 'FUJI' APPLES

In this work, 'Fuji Kiku-8' apples were treated with 2% (w/v) CaCl 2 and stored at 1°C and 92% RH under either air or two different controlled atmosphere (CA) regimes for 7 months. Different cell wall-modifying enzyme activities were determined 7 d after removal from storage in order to assess relationships, if any, to changes in fruit firmness and cell wall composition induced by CaCl 2 treatment and/or storage atmosphere. Applied calcium was effective in preserving firmness of air-stored fruit but no significant differences in this attribute were found for samples kept under CA regardless of calcium treatment. Results showed high correlation between firmness and covalently-bound pectin content. To a lesser extent, non covalently-bound pectin content was also related to firmness. Solubilisation of pectins, which leads to loss of fruit firmness, may require a previous release of neutral sugar residues from the side-chains of wall-bound pectins by the action of a number of glycosidases such as β-galactosidase (β-Gal) or β-xylosidase (β-Xyl), which in turn was partially inhibited by CA-conditions during cold storage.

MODIFICATIONS IN CELL WALL COMPOSITION AFTER STORAGE OF 1-MCP-TREATED PEACH FRUIT

Rapid softening of peach (Prunus persica L. Batsch) fruit after harvest considerably limits commercial life of produce. The decline in fruit firmness during ripening and storage is largely the result of partial disassembly of the primary cell wall arising from compositional changes. In this work, suitability of controlled atmosphere (CA) storage and 1-methylcyclopropene (1-MCP) treatment to delay these changes and to extend storage potential of a late-harvesting peach cultivar was tested. Cell wall materials were extracted and fractionated 0 and 7 d after storage to assess possible relationships to changes in fruit firmness. The yield of soluble materials increased during the shelf life period at 20°C, consistent with a decline in the contents of cell wall materials and of pectin-containing fractions, possibly in relation to the decrease in flesh firmness. The increase in the yield of soluble fractions after storage was attenuated by 1-MCP treatment, which proved more effective than CA storage in delaying solubilisation of cell wall polymers.

Effect of nitric oxide on the sensitivity of banana fruit slices to ethylene

SummaryThe effects of nitric oxide (NO) treatment on the sensitivity of banana fruit slices to ethylene were investigated. Fruit slices were partial-pressure infiltrated for 3 min in a NO donor solution of 5 mM sodium nitroprusside (SNP), followedby treatment with 100 µl l1 ethylene for 24 h, then packed into polyethylene bags and stored for 5 d at 24°C. Control slices were treated with distilled water instead of SNP, then treated with ethylene. Changes in fruit firmness, chlorophyll content, respiration rate, the activities of three cell wall modifying enzymes [polygalacturonase (PG), endo-ß&-1,4-glucanase (EGase), and ß-galactosidase (ß-Gal)], and total amylase activity were measured. Expression of the expansin (MaExp1) and ethylene receptor (MaERS2) genes were also analysed. The application of NO, prior to ethylene exposure, retarded pulp softening and peel de-greening. Pre-treatment with NO also decreased the respiration rate of banana fruit slices during ripening. Delayed pulp softening by NO was associated with decreased activities of PG, EGase, ß-Gal, and total amylase, as well as reduced expression of the MaExp1 gene. Expression of the MaERS2 gene was also suppressed in NO-treated banana fruit slices. Collectively, these findings suggest that NO pre-treatment decreased the sensitivity of banana fruit slices to ethylene, and thereby delayed ripening.

Characterization of cultivar differences in beta-1,3 glucanase gene expression, glucanase activity and fruit pulp softening rates during fruit ripening in three naturally occurring banana cultivars.

beta-1,3 glucanase (E.C.3.2.1.39) is the key enzyme involved in the hydrolytic cleavage of 1,3 beta-D glucosidic linkages in beta-1,3 glucans. This work describes a comparative analysis of expression patterns of beta-1,3 glucanase gene in relation to changes in fruit pulp softening rates in three banana cultivars, Rasthali (AAB), Kanthali (AB), and Monthan (ABB). Analysis of transcript and protein levels of beta-1,3 glucanase gene during ripening revealed differential timing in expression of the gene which correlated well with the variation in enzymatic activity of glucanase and fruit pulp softening rates in the three cultivars. Exogenously applied ethylene strongly induced beta-1,3 glucanase expression during the early ripening days in Rasthali, while the expression of the gene was marginally stimulated following ethylene treatment in preclimacteric Kanthali fruit. Conversely, in Monthan, beta-1,3 glucanase expression was very low throughout the ripening stages, and ethylene treatment did not induce the expression of the gene in this cultivar. Analysis of glucanase activity using protein extracts from unripe and ripe fruit of Monthan with crude cell wall polysaccharide fractions (used as substrate) indicated that the natural substrate for glucanase remained almost unutilized in this cultivar due to low in vivo glucanase activity. Furthermore, the recombinant beta-1,3 glucanase protein, overexpressed in E. coli, showed requirement for substrates with contiguous beta-1,3 linkages for optimal activity. Overall, our results provide new information on the expression profile of beta-1,3 glucanase gene in connection with the pattern of changes in fruit firmness at the physiological and molecular levels during ripening in three banana cultivars.

Response of climacteric-type guava ( Psidium guajava L.) to postharvest treatment with 1-MCP

Guava ( Psidium guajava L. cv. ‘Allahabad Safeda’) fruit harvested at the mature light-green stage were exposed to 300 and 600 nL L −1 1-methylcyclopropene (1-MCP) for 6, 12 and 24 h at 20 ± 1 °C, and held in either cold storage (10 °C) for 25 days or ambient conditions (25–29 °C) for 9 days. Most of the physiological and biochemical changes during storage and ripening were affected by 1-MCP in a dose dependent manner. Ethylene production and respiratory rates were significantly suppressed during storage as well as ripening under both the storage conditions depending upon 1-MCP concentration and exposure duration. 1-MCP treatment had a pronounced effect on fruit firmness changes during storage under both the conditions. The reduced changes in the soluble solids contents (SSC), titratable acidity (TA) and vitamin C content showed the effectiveness of 1-MCP in retarding fruit ripening. Vitamin C content in 1-MCP-treated fruit was significantly higher than in non-treated fruit, and those treated with 300 nL L −1 1-MCP for 6 h. The development of chilling injury symptoms was ameliorated to a greater extent in 1-MCP-treated fruit during cold storage and ripening. A significant reduction in the decay incidence of 1-MCP-treated fruit was observed under both the storage conditions. 1-MCP at 600 nL L −1 for 12 h, in combination with cold storage (10 °C) seems a promising way to extend the storage life of guava cv. ‘Allahabad Safeda’ while 1-MCP at 300 nL L −1 for 12 and 24 h or 600 nL L −1 for 6 h, may be used to provide 4–5 days extended marketability of fruit under ambient conditions.

Identification of a new expansin gene closely associated with peach fruit softening

Abstract Expansins are proteins that have been shown to contribute to fruit softening in tomato. However, expansins that have been correlated with loss of fruit firmness have not yet been identified in peach (Prunus persica (L.) Batsch). Along with the previously isolated PpExp1, two new expansin cDNAs, termed PpExp2 and PpExp3, were isolated from ripe peach fruit, and their mRNA expression patterns were characterized during fruit development and in other tissues, including the flower bud, leaf, and stem. All three expansins were detected in the fruit and not in the other tissues, but each showed differential patterns of mRNA accumulation during fruit development. The PpExp2 mRNA was constitutively expressed throughout fruit development but was abundant in Stage III, when the fruit expands exponentially and then matures. The PpExp1 and PpExp3 mRNAs were up-regulated at the onset of ripening, but PpExp1 was induced at an earlier stage. In order to identify the expansins whose expression correlates with the loss of peach fruit firmness, the mRNA expression levels of the three expansins were compared in the ripe fruit of the ‘Akatsuki’ and ‘Manami’ cultivars during postharvest storage. During storage, the ripe fruit of ‘Akatsuki’ rapidly softened as the level of ethylene increased significantly, while ‘Manami’ fruit remained firm and exhibited very low levels of ethylene production. The PpExp1 and PpExp2 mRNAs were constitutively detectable during the 8-day storage of both cultivars, whereas PpExp3 mRNA was detectable in ‘Akatsuki’ but hardly detectable in ‘Manami,’ suggesting that PpExp3 expression may be related to the changes in fruit firmness. To address the detailed role of PpExp3 in the loss of fruit firmness, the fruit of ‘Manami’ was treated by ethylene to artificially induce softening. The PpExp3 mRNA accumulation in the ethylene-treated ‘Manami’ was detectable and similar to that observed in ‘Akatsuki.’ These results show that, while several expansins show a general increase in expression levels during the later stages of fruit development, some isoforms show a greater association with softening than others. In this regard, PpExp3 is more likely to play a role in peach fruit softening than PpExp1 or PpExp2.

Pulsed white light in combination with UV-C and heat to reduce storage rot of strawberry

Abstract Three physical methods—pulsed white light, heat, and ultraviolet-C (UV-C, λ=254 nm) irradiation—were used in different combinations for surface decontamination of strawberry fruit. Strawberries were inoculated with conidia of Botrytis cinerea. Over 10 days, fungal development and structural damage (e.g. holes, changes in fruit firmness) were daily recorded. Pulsed light treatments consisted of 30 μs pulses at a frequency of 15 Hz for a total duration of 40 to 250 s. For the combination experiments, the UV-C doses were 0.5 or 1.0 kJ m−2 and the heat treatments were at 40 and 45 °C for 3 or 15 min. Pulsed light treatments alone had no positive or negative effect. Combining a thermal and an UV-C treatment allowed for a decrease of the thermal treatment to 40 °C for the same level of fungal inactivation. No external fruit damage was reported at this temperature of 40 °C. A combination of a thermal treatment with light pulses did not result in a significant difference in fungal growth. Combining two illumination treatments did not cause a significant decrease in fungal development. In both cases, however, the period before the first observation of fungal growth was increased by 1 or 2 days. Induced resistance against fungal infections in treated fruit was not observed after pulsed light treatment. These induced reactions of treated berries were observed after UV-C treatment of strawberries, but not observed when a thermal treatment was used.

The effect of spraying essential oils of Cymbopogon nardus, Cymbopogon flexuosus and Ocimum basilicum on postharvest diseases and storage life of Embul banana

SummaryEmbul banana hands were sprayed with emulsions of the essential oils of Ceylon citronella (Cymbopogon nardus) (0.4% v/v) lemon grass Cymbopogon flexuosus (0.16% v/v), or Indian sweet basil (Ocimum basilicum) (0.16% v/v) and stored cool (13.5 ± 1°C) or at ambient temperature (28 ± 1°C) at 94% relative humidity. A benomyl spray (0.1% w/v) was included as a standard fungicide control treatment. The effects of the essential oils on post-harvest diseases, and on organoleptic and cosmetic quality and various properties of the fruit (percentage weight loss, changes in fruit firmness, total soluble solids and titratable acidity) were determined. Treatment with Ocimum basilicum oil controlled crown rot and anthracnose, enabling bananas to be stored for up to 21 d at 13.5 ± 1°C without any detrimental effect on their organoleptic properties; results were comparable with treatment with benomyl. Rapid-ripening induced by ethral after cool storage resulted in better quality bananas. The oil of C. nardus affected the texture and flavour of the fruit and that of C. flexuosus did not give complete control of crown rot. Spraying Embul bananas with emulsions of the essential oil of Ocimum basilicum prior to cool storage can be recommended therefore as a safe, cost-effective method, with commercial potential, for controlling post-harvest diseases and extending storage life.

Impact of controlled atmosphere storage conditions on storability and consumer acceptability of sweet cherries ‘Regina’

SummarySweet cherries obtained from a rain-protected orchard were subjected to various controlled atmosphere storage conditions for up to seven weeks. Quality parameters responded differentially to various CA-conditions: changes in fruit firmness, sugar content and colour were mostly not significant. However, the storage conditions exerted significant impact on other parameters such as respiration rate, RQ, ATP- and ADP-concentrations. Air-stored fruits respired at significant higher rates than CA or ultra low oxygen-stored fruits. Moreover, the impact of CA-storage conditions persisted even after a conditioning period of 36 h at room temperature. The ATP and ADP concentrations of sweet cherries behaved similarly, where a combination of reduced O2 and very high CO2 concentration (12% or above) resulted in highly reduced ATP-concentration in the fruit tissue. A taste panel considered fruits stored under 6% CO2 + 2% O2 as good, although there was a strong indication that it is better to store sweet cherries for a limited time (up to five weeks) under a low O2 concentration combined with a high CO2 concentration (12%) or under a high O2 concentration combined with a very high CO2 (18%).

Relationship between fruit softening and the change of β-D-galactosidase activity of Japanese persimmon 'Tonewase' treated with different methods for removing astringency

Tonewase'fruit is the most popular Japanese persimmon (Diospyros kaki Thunb.) in Japan. It has fine flesh and good taste after its astringency was removed. But the fruit has very short shelf life, because of rapid softening. There are two ways for removing astringency; 1) treatment with alcohol on tree and 2) treatment with carbon dioxide (CO2). The present study was conducted to investigate the relationship between the changes in fruit firmness and β-D-galactosidase activity which was hydrolyzed hemicellulosic components. (1) The loosing of fruit firmness was not different between treatments of alcohol on tree and CO2 at 20°C for 24 hours (CTSD method) for removing astringency until 4 days after storage at 20°C, however, the former showed slow softening during storage for 8 days but the latter was rapid softening at 6 days (5 days after treatment). The respiration and ethylene production of fruits treated with carbon dioxide and non-treatment were similar pattern and increased at the end of storage period. However, the fruit of alcohol treatment on tree maintained low level which was comparison with non-treatment and carbon dioxide fruit. (2) The activity of β-D-galactosidase which was non-treatment and CTSD treatment for removal astringency increased during storage. The fruit of alcohol treatment on tree maintained low activity during storage. Finally, the activity of non-treatment and CTSD treatment fruit was higher than alcohol treatment on tree one during storage. These results indicated that the fruit softening of 'Tonewase' is attributable to increase of ethylene production and attended to increased, β-D-galactosidase activity. It was suggested that the fruit softening of alcohol treatment on tree, CTSD treatment, and non-treatment fruits were depend on a degree of hydrolyzed hemicellulosic components during storage or postharvest.

Relationship between fruit softening and the change of pectic or hemicellulosic compounds in cell wall of Japanese persimmon 'Hiratanenashi' and 'Fuyu'

'Hiratanenashi' fruit is the most popular Japanese persimmon (Diospyros kaki Thunb.) in Japan.It has fine flesh and good taste after its astringency was removed. But the fruit has very short shelf life, because of rapid softening after removed astringency. 'Tuyu' fruit is also popular persimmon fruit which is the non-astringency cultivar. The present study was conducted to investigate the relationship between the changes in fruit firmness and cell wall composition (pectic and hemicellulosic composition) and 'Eliratanenashi' and 'Tuyu' cultivars. (1) Sugar of phenol-acetic acid-water (PAW) fraction from 'Tuyu' fruits were increased, but the content of 'Hiratanenashi' fruit did not change during storage. Soluble polyuronide contents increased both cultivars during storage. (2) The contents of cyclohexane-trans-1, 2-diamine tetra-acetate (CDTA) soluble polyuronide and sugar contents of 'Fuyu' fruit was decreased markedly during from 10 day to 15 day in storage. 'Hiratanenashi' fruit was not change during storage.The contents of Na2CO3 soluble polyuronide and sugar contents of both cultivars were similar pattern of CDTA soluble fraction. (3) The contents of guanidium-thiocyanate (GTC) -soluble and KOH-soluble sugar from hemicellulosic components did not change in 'Hiratanenashi' and 'Tuyu' fruit during storage. These results indicated that the fruit softening of 'Hiratanenashi' and 'Tuyu' are attributable to increase of water-soluble polyuronide and decrease of water-insoluble polyuronide contents. Pectic component in 'Fuyu' fruit is much quantity comparison with 'Hiratanenashi' fruit, and polyuronide and sugar contents in pectic component of both cultivars have a similar tendency to fruit firmness.

Molecular cloning of a ripening-related expansin cDNA in peach: evidence for no relationship between expansin accumulation and change in fruit firmness during storage

Summary A cDNA (PchExp 1) encoding a ripening-regulated expansin was isolated from ripe peach fruit. PchExp 1 encodes a predicted protein of 252 amino acids including the predicted signal sequence. The phylogenetic tree based on the deduced amino acid sequences indicated that PchExp 1 was most closely related to apricot PaExp2 and strawberry ripening-regulated FaExp2, and distantly to tomato ripening-regulated LeExp 1. The accumulation of PchExp 1 mRNA was fruit-specific and ripening-regulated. Furthermore, it was enhanced abundantly in 6 h by ethylene treatment. However, the patterns of PchExp 1 mRNA abundance in the ripe fruit of Akatsuki, which lost its firmness rapidly after harvest, and Yumyeong, which retained its firmness after harvest, were very similar during storage for eight days, irrespective of their different traits regarding changes in fruit firmness. The accumulation of protein recognized by the antibodies for LeExp 1 is also detected in the ripe fruit of Yumyeong. The present study suggests that PchExp 1 may play an important role in peach fruit ripening, but the accumulation of PchExp 1 may not regulate the changes in fruit firmness during storage of the peach.