Loss Of Flesh Firmness Research Articles

Effects of Daminozide, Paclobutrazol, and Uniconazole Treatments on `McIntosh' Apples at Harvest and Following Storage

Foliar daminozide (DZ) applications to `McIntosh' apple trees (Malus domestics Borkh.) increased fruit color, reduced preharvest drop, resulted in greater firmness at harvest and after air storage, delayed starch hydrolysis, and reduced fruit ethylene production at harvest and after storage. Foliar paclobutrazol (PBZ) reduced preharvest drop and flesh firmness loss if applied within 5 weeks after full bloom (WAFB). Later applications had no effect. PBZ did not influence the progress of starch hydrolysis or ethylene production at harvest but reduced poststorage ethylene production in one season. Stem-cavity browning and brown core were increased by PBZ applied at 5 and 9 WAFB in 1987. In 1988, fruit soluble solids content (SSC) was reduced by a double application of PBZ and by uniconazole (UCZ). UCZ had little effect on `McIntosh' fruit other than the reduction in SSC. PBZ applications were less consistent in their effects than DZ. Chemical names used: butanedioic acid mono(2,2-dimethylhydrazide) (daminozide); ß-[(4-chlorophenyl) methyl]-α- -(l,l-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol); ß-[(4-chlorophenyl)methylene]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (uniconazole).

Modification of polyuronides and hemicelluloses during muskmelon fruit softening

The loss of flesh firmness during muskmelon (Cucumis melo var. reticulatus L. Naud. cv. Galia) fruit ripening was related temporally to modifications of pectic and hemicellulosic polysaccharides, and a net loss of non‐cellulosic neutral sugars. An increase in solubility and a decrease in molecular size of polyuronides occurred during ripening; however, the decrease in molecular size was apparently not the result of polygalacturonase (EC 3.2.1.15) activity. Molecular size of hemicelluloses shifted from larger to smaller polymers during ripening, and this decrease was accompanied by changes in neutral sugar composition. Galactose, glucose, and xylose were the predominant neutral sugars in the hemicellulosic polymers. On a mol% basis there were decreases in galactose and glucose in large hemicellulosic polymers with ripening. Relative xylose content approximately doubled in the large polymers during ripening; xylose was the predominant neutral sugar in the small polymers and remained fairly constant.

Effects of Fruit Detachment on Ethylene Biosynthesis and Loss of Flesh Firmness, Skin Color, and Starch in Ripening ‘Golden Delicious’ Apples

Abstract Prior to 25 Oct., about 4-6 weeks (1983) or 3-5 weeks (1984) after the normal commercial harvest period, 1-aminocyclopropane-l-carboxylic acid (ACC), ethylene-forming enzyme (EFE), and internal ethylene concentration (IEC) in ‘Golden Delicious’ (Malus domestica Borkh.) apples attached to the tree were low. Thereafter, they began to increase rapidly. The increase in both ACC and IEC was earlier in detached preclimacteric fruit than in fruit attached to the tree. The increase of EFE coincided with that of IEC in detached fruit kept at 20°C. Attached fruit subsequently attained a higher level of ACC but a lower level of IEC as compared to the detached fruit. The results suggest that inhibitor(s) supplied from the tree not only delayed the accumulation of ACC in the fruit but also greatly inhibited its subsequent conversion to ethylene. Once the ripening process is initiated, the development of EFE precedes the development of ACC synthesis in both attached and detached fruit. Since attached fruit showed a steady loss of flesh firmness, green skin color, and starch, these changes did not appear to be related directly to the levels of ACC and internal ethylene. Detached fruit stored at 0° accumulated ACC and increased IEC slightly earlier than those stored at 20°. The magnitudes of these increases during subsequent storage at 0° were, however, smaller than those at 20°.

Effect of low oxygen and high carbon dioxide on the levels of ethylene and 1-aminocyclopropane-1-carboxylic acid in ripening apple fruits

The association of the level of ACC and the ethylene concentration in ripening apple fruit (Malus sylvestris Mill, var. Ben Davis) was studied. Preclimacteric apple contained small amounts of ACC and ethylene. With the onset of the climacteric and a concomitant decrease in flesh firmness, the level of ACC and ethylene concentration both increased markedly. During the postclimacteric period, ethylene concentration started to decline, but the level of ACC continued to increase. Ethylene production and loss of flesh firmness of fruits during ripening were greatly suppressed by treatments with low O2 (O2 1–3%, CO2 O%) or high CO2 (CO2 20–30%, O2 15–20%) at the preclimacteric stage. However, after 4 weeks an accumulation of ACC was observed in treated fruits when control fruit was at the postclimacteric stage. Treatment of fruit with either low O2 or high CO2 at the climacteric stage resulted in a decrease of ethylene production. However, the ACC level in fruit treated with low O2 was much higher than both control and high CO2 treated fruit; it appears that low O2 inhibits only the conversion of ACC to ethylene, resulting in an accumulation of ACC. Since CO2 inhibits ethylene production but does not result in an accumulation of ACC, it appears that high CO2 inhibits both the conversion of ACC to ethylene and the formation of ACC.

Retention of Fruit Firmness and Increase in Vegetative Growth and Fruit Set of Apples with Aminoethoxyvinylglycine1

Abstract Aminoethoxyvinylglycine (AVG), an inhibitor of ethylene synthesis, applied to ‘Delicious’ apple trees (Malus domestica Borkh.) 2 weeks before harvest reduces loss of flesh firmness of apples in storage and increases vegetative growth in the following growth season. When applied to ‘Delicious’ or ‘Golden Delicious’ trees after full bloom, the “June drop” was completely eliminated; thus, fruit set was significantly increased.

White shellac varnish

The gas permeabilities of shellac and several experimental coating formulations, including candelilla wax and shellac-carnauba were measured. These coatings, selected to have a wide range of gas permeabilities, were applied to freshly harvested and 5-month commercially stored ‘Delicious’, ‘Fuji’, ‘Braeburn’ and ‘Granny Smith’ apples. The coated apples were monitored during storage of 2 or 4 weeks at 20 °C for changes in internal gases level, and for quality parameters (surface gloss, weight loss, flesh firmness, Brix, titratable acidity and ethanol content). The shellac coating resulted in maximum fruit gloss, lowest internal O2, highest CO2, and least loss of flesh firmness for all of the varieties. The ‘Granny Smith’ with shellac had low internal O2 (<2 kPa) with both freshly harvested and 5 month-stored apples, and the freshly-harvested ‘Braeburn’ had high internal CO2 (25 kPa). This excessive modification of internal gas induced an abrupt rise of the respiratory quotient, prodigious accumulation of ethanol in both ‘Braeburn’ and ‘Granny Smith’, and flesh browning at the blossom end of ‘Braeburn’. In addition the shellac coating gave an unusual accumulation of ethanol in freshly harvested and 5 month-stored ‘Fuji’. Candelilla and carnauba-shellac coatings maintained more optimal internal O2 and CO2 and better quality for ‘Fuji’, ‘Braeburn’ and ‘Granny Smith’ apples, although even these coatings may present too much of a gas barrier for ‘Granny Smith’. Therefore, this research recommends the best coatings as shellac for ‘Delicious’, and carnauba-shellac for ‘Braeburn’ or ‘Fuji’. Best for ‘Granny Smith’ would seem to be a high-permeability wax similar to polyethylene, which has not been approved for apple by FDA. In general, the gas permeabilities of the coatings were useful as an indicator of differences in coating barrier properties, but did not account for differences in pore blockage.