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- Author or Editor: Donald Huber x
- Journal of the American Society for Horticultural Science x
Abstract
In the article “Respiration and Ethylene Production in Harvested Watermelon Fruit: Evidence for Nonclimacteric Respiratory Behavior,” by Mohamed E. Elkashif, Donald J. Huber, and Jeffrey K. Brecht [J. Amer. Soc. Hort. Sci. 114(1):81–85, January, 1989], the respiratory drifts in Fig. 1 were not clearly visible. An improved figure is printed below.
`Solar Set' tomatoes (Lycopersicon esculentum Mill.) were harvested at the mature-green stage of development and treated with 50 μL·L-1 ethylene at 20 °C. Breaker-stage fruit were dropped from 40 cm onto a solid surface to induce internal bruising and held along with undropped fruit at 20 °C. At the ripe stage, pericarp, locule, and placental tissues were analyzed for soluble sugars, vitamin C, pigments, titratable acidity, soluble solids content, pericarp electrolyte leakage, extractable polygalacturonase activity, and locule tissue consistency. Bruising significantly affected chemical composition and physical properties of pericarp and locule tissues, but not placental tissue. For bruised locule tissue, carotenoids, vitamin C, and titratable acidity were 37%, 15%, and 15%, lower, respectively, than unbruised fruit. For bruised pericarp tissue, vitamin C content was 16% lower than for unbruised tissue, whereas bruising increased electrolyte leakage and extractable polygalacturonase activity by 25% and 33%, respectively. Evidence of abnormal ripening following impact bruising was confined to locule and pericarp tissues and may be related to the disruption of cell structure and altered enzyme activity.
`Haden' and `Tommy Atkins' mangoes (Mangifera indica L.) were stored in air, 2, 3, 4 or 5 kPa O2 plus N2, or 25 kPa CO2 plus air for 14 days at 15 °C or 21 days at 12 °C, respectively, then in air for 5 days at 20 °C to determine their tolerance to reduced O2 levels for storage times encountered in typical marine shipments. All low O2 treatments reduced mature green mango respiration (CO2 production), however, elevated ethanol production occurred in 2 and 3 kPa O2 storage, with the levels two to three times higher in `Tommy Atkins' than `Haden'. In contrast, `Haden' fruit at the onset of the climacteric also accumulated ethanol in 4 kPa O2 and produced 10 to 20-fold more ethanol in 2 and 3 kPa O2 than preclimacteric fruit. While there were no visible injury symptoms, off flavor developed in mature green fruit at 2 kPa O2 and in ripening initiated fruit at 2 and 3 kPa O2. Ethanol production was not affected by storage in 25 kPa CO2. Ethylene production was reduced slightly by low O2, however, `Haden' fruit also showed a residual inhibitory effect on ethylene production after 2 or 3 kPa O2 storage, while `Tommy Atkins' fruit stored in 2 kPa O2 produced a burst of ethylene upon transfer to air at 20 °C. Fruit firmness, total sugars, and starch levels did not differ among the treatments, but 2, 3 or 4 kPa O2 and 25 kPa CO2 maintained significantly higher acidity than 5 kPa O2 or air. The epidermal ground color responded differently to low O2 and high CO2 in the two mango cultivars. Only 2 kPa O2 maintained `Haden' color better than air, while all low O2 levels maintained `Tommy Atkins' color equally well and better than air. High CO2 was more effective than low O2 in maintaining `Haden' color, but had about the same effect as low O2 on `Tommy Atkins'. Results indicate that preclimacteric `Haden' and `Tommy Atkins' mango fruit are able to tolerate 3 kPa O2 for 2 or 3 weeks at 12 to 15 °C and that tolerance to low O2 decreases as mangoes ripen. Results also show that low O2 and high CO2 affect mango ripening differentially.
The effect of physiological maturity at harvest on ripe tomato (Lycopersicon esculentum Mill.) volatile profiles was studied using ripening response time (in days) to 100 μL·L-1 exogenous ethylene treatment as a tool to separate immature-green from mature-green fruit. Electronic nose (EN) sensor array and gas chromatography (GC) analyses were used to document volatile profile changes in tomatoes that required a 1-, 3-, or 5-day ethylene treatment to reach the breaker stage. EN output analysis using multivariate discriminant and canonical analyses classified intact tomato and whole tomato homogenate samples that required 3 or 5 days of ethylene treatment as significantly different (P < 0.01) from those that required only 1 day. The GC aroma profiles from whole tomato homogenate showed that 1-day fruit had significantly higher levels (P < 0.05) of 1-penten-3-one, cis-3-hexenal, 6-methyl-5-hepten-2-one, 2-isobutylthiazole, and geranylacetone when compared to 5-day fruit. Analysis of excised tomato tissues showed that pericarp (including columnella) produced an average 219% greater concentration of the 16 aroma volatiles quantified by GC when compared to locular gel (442 and 203 μL·L-1, respectively). EN analysis concurred with GC by showing greater average Mahalanobis distance between pericarp tissue groupings when compared to locular gel groupings (78.25 and 12.33 units, respectively). Pericarp tissue from the 5-day ethylene treatment showed significantly lower levels of 1-penten-3-one, trans-2-heptenal, 6-methyl-5-hepten-2-one, 2-isobutylthiazole, geranylacetone, and β-ionone compared to the 1- and 3-day treatments, Similarly, locular gel from the 3- and 5-day ethylene treatments had significantly lower levels of 1-penten-3-one, 2-isobutylthiazole, and 1-nitro-2-phenylethane compared to 1-day samples. cis-3-Hexenol in locular gel was the only volatile compound that showed significantly higher levels with increasing ethylene treatment. EN analysis showed greater Mahalanobis distances between 1- and 3-day ethylene samples than between 3- and 5-day ethylene samples (32.09 and 12.90, 24.14 and 6.52, 116.31 and 65.04, and 15.74 and 13.28 units, for intact tomato, whole tomato, pericarp, and locular gel homogenate, respectively).