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  • Author or Editor: W. B. McGlasson x
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Abstract

An investigator commencing work on ethylene and fruit ripening is confronted by the enormous diversity among fruit. It is necessary to identify unique characteristics that differentiate fleshy plant structures from other plant parts in order to develop new treatments successfully for extending the commercial life of fruit. Fleshy fruit are typically determinate structures genetically programmed within each species to achieve a distinctive maximum size, shape, color, texture, and taste. Botanical origins of the tissues that comprise fruit are various. The metabolism of fruit is qualitatively similar, despite their morphological and anatomical diversity, in all cases involving glycolysis, the tricarboxylic acid cycle, terminal oxidases and the biogenesis of ethylene, auxin, gibberellin, cytokinin, and abscisic acid. Genetic diversity in the patterns of ethylene production during growth, ripening, and senescence is apparent among fruit.

Open Access

Abstract

Low levels of abscisic acid (ABA) were found at 10 days after anthesis in fruits of a normal cultivar (‘Rutgers’) and of the abnormal ripening mutants (Nr, rin and nor) of tomato (Lycopersicon esculentum Mill). Thereafter the levels increased to peak values which preceded or coincided with coloring in all strains. Peak levels of ABA coincided with the completion of growth in ‘Rutgers’ and rin but followed completion of growth in Nr and nor. Phaseic acid (PA) and gibberellin (GA) activity were highest in all strains about 10 days after anthesis. Subsequently the levels decreased then rose to a second peak except for PA in rin which remained at a relatively high level from 20 days until completion of growth. The second peak in PA in Rutgers, Nr and nor coincided approximately with peak levels of ABA, the second peak in gibberellin activity preceded the peak of ABA in Rutgers, Nr and rin but coincided with it in nor. The results showed that the patterns in the levels of ABA, PA and gibberellin from about 14 days after anthesis are related to ripening or senescence in the four strains and not to growth.

Open Access

Abstract

‘Valencia’ oranges were stored at 10°C in air and in an atm of 5% CO2,3% O2 under flowing and static atmospheric conditions with and without an ethylene absorbent The development of decay, particularly stem-end decay, loss of orange flavor and development of off-flavor appeared to be primarily associated with the presence of ethylene and not with other volatiles in the storage atm.

Open Access

Abstract

Lemons (Citrus limon (L.) Burm. f.) were stored for up to 27 weeks at 10°C in air and in an atmosphere of 3 to 5% O2 and 0.1 to 0.2% CO2, with and without an ethylene absorbent. Mold incidence was high in controlled atmosphere (CA) storage where ethylene accumulated, but removal of ethylene reduced its development. CA storage improved retention of green color in lemons.

Open Access

Abstract

Ripening is a dramatic event in the development of many fleshy fruits. Tomato ripening involves a number of chemical and physical changes which convert the fruit from a relatively inedible state to one of optimal quality (2, 19). These changes appear to be highly synchronized, as evidenced by the fact that respiratory patterns, rate of ethylene production, carotene development, and flavor and textural changes normally associated with the ripening process, occur in close succession during the relatively short period in which the fruit ripens (2, 22). The association of these changes with seed maturation supports the popular view that ripening is of adaptive significance in seed dispersal by rendering fruit attractive to animals responsible for dispersal.

Open Access

Abstract

Composition and sensory acceptability of fresh market tomatoes (Lycopersicon esculentum Mill ‘Flora-Dade’) were investigated to determine the influence of harvest maturity on quality after fruit had ripened to a tableripe stage. Tomatoes were harvested from commercial plots at ‘immature green’, ‘mature green’, ‘breaker’, ‘light pink’, and ‘light red’. The differentiation between tomatoes harvested ‘mature green’ and ‘immature green’ was aided by application of 40 μl/liter of ethylene in a ripening room at 20°C. Tomatoes harvested at ‘breaker’ were more acceptable when ripe than all other maturities at harvest. Tomatoes harvested at ‘immature green’, ‘mature green’, ‘light pink’, and ‘light red’ were of similar sensory acceptability. The tomatoes harvested at ‘light pink’ and ‘light red’ when ripe were similar or lower in total soluble solids and generally lower in locular content compared to other harvest maturities. There was a high correlation between sensory scores for color and measured external and internal color.

Open Access

Abstract

Differences in aroma have been examined in headspace samples of ripe tomato (Lycopersicon esculentum Mill.) fruit of ‘Rutgers’ and of yellowing fruit of the nonripening mutants rin and nor. Volatiles were trapped and separated by gas chromatography, and the intensity of the effluent aromas was rated by sniffing. Intense aroma compounds were identified by mass spectrometry. Sixty-nine intense compounds were found in ‘Rutgers’, of which 46 were present in one or both mutant strains. Fifteen compounds with odor intensities rated medium to very strong were identified that were deficient or absent in fruit of the mutants. The latter compounds included two aldehydes, seven alcohols, two ketones, three sulfur-containing compounds, and a phenol. A few compounds were intense odors in ‘Rutgers’ and in one or both mutants; hex-2-enal, linalool, phenylacetaldehyde, methyl salicylate, 2-phenylethanol, and eugenol. Some compounds were detected that were more intense in rin and nor than in ‘Rutgers’ (e.g., guaiacol). It is proposed that the “normal background aroma” in fresh tomatoes is caused by those intense odors, which are common to both normal and mutant strains, whereas the bland flavor of mutant fruit is caused by the absence of those intense aroma compounds found only in ‘Rutgers’. The intense aroma compounds found only in ‘Rutgers’ may be crucial determinants of acceptability in fresh tomato fruit.

Open Access

Abstract

A range of tomato (Lycopersicon esculentum Mill.) cultivars was examined for changes during ripening in firmness, endopolygalacturonase (PG) activity and the molecular forms of polygalacturonase, Ca concentration, and the extractability of the Ca. Firm cultivars were firmer than the soft cultivars throughout ripening, and generally they contained less PG activity at each stage examined. In all cultivars, PG was predominately or entirely in the high molecular weight form (PG1) early in ripening, with the PG2 forms being increasingly prominent as ripening progressed. Differences in firmness were established while PG1 was the predominant PG. Uronic acid polymers in isolated cell walls were degraded rapidly by endogenous PG when citrate was present to complex Ca. In the presence of sufficient citrate, cell wall uronic acids of a firm and soft cultivar were equally susceptible to hydrolysis, suggesting that differences in the digestion of the walls by PG were dependent upon differences in Ca content or distribution. However, neither total, water, nor saline-extractable Ca showed consistent correlations with fruit firmness, and they also showed no progressive change during ripening.

Open Access