) ( Redgwell and Turner, 1986 ). The first sign of pepino ripening is the appearance of purple strips. Conclusions on the climacteric (an increase or not in respiration during ripening classifies fruit as climacteric or nonclimacteric) of the pepino are not yet
Tomato (Lycopersicon esculentum Mill.) fruit, cvs. Sunny and Solar Set, were analyzed at five ripening stages for ethylene and CO2 production. Homogenates from the same fruit were prepared for determination of color, flavor volatiles, sugars, and organic acids. Changes in the levels of these compounds were compared to the pattern of climacteric ethylene production. Of the flavor volatiles measured, only eugenol decreased during ripening in both cultivars and 1-penten-3-one in `Sunny' tomatoes. Ethanol and trans-2-trans- 4-decadienal levels showed no change or fluctuated as the fruit ripened while all other volatiles measured (cis- 3-hexenol, acetaldehyde, cis- 3-hexenal, trans-2- hexenal, hexenal acetone, 6-methyl-5 -hepten-2-one, geranylacetone, and 2-isobutylthiazole) increased in concentration, peaking in the turning, pink, or red stage of maturity. Synthesis of some volatile compounds occurred simultaneously with that of climacteric ethylene, CO2 and lycopene production. `Solar Set' fruit exhibited higher levels than `Sunny' of all flavor components except ethanol and hexanal in the red stage. There were no differences in organic acid levels between the cultivars; however, `Solar Set' had higher levels of sugars. Changes in acid and sugar levels showed no temporal relationship to climacteric ethylene or CO2 production.
Abstract
Ripening of mature avocado fruit was accelerated by 18- and 24-hr ethylene treatments which were applied beginning 1 hr after harvest. Exposure to ethylene for 12 hr or less, starting 1 hr after harvest, did not accelerate the respiration rate, ethylene evolution, or fruit softening. Ethylene treatment for 6 hr starting at 1, 6, 12, or 18 hr after harvest did not accelerate the onset of the ripening process. It is suggested that ethylene does not just “trigger” the ripening of avocado fruit but rather is involved in a relatively long (18 to 24 hr) process which requires its continuous presence.
Abstract
Star fruit (Averrhoa carambola L. cv. Golden Star) was harvested in progressively advanced stages of ripeness. Ethylene and CO2 production were lower in ripening fruits than in green ones. In fully ripe fruit, higher levels of CO2 and ethylene were attributed to microbial activity or to tissue senescence. Dissolved solids steadily increased with ripening. The ethylene, CO2, and ripening patterns were typical of those for nonclimacteric fruit.
Abstract
The patterns of concentrations of CO2 and C2H4 in the cavity of attached ripening papayas (Carcia papaya L. cv. Solo) were similar to those of CO2 in respiration and C2H4 production in detached ripening fruits. The peak concentrations of these gasses occurred when the surface color of the fruits was about 80%. The flavor of the pulp of the ripe fruit was rated highest at this time.
Abstract
Postchilling ion leakage, respiration, and C2H4 biosynthesis were used to measure the degree of chilling injury to fruit of tomato (Lycopersicon esculentum Mill. ‘Heinz 1350’). Chilling sensitivity, as measured by ion leakage, first declined as the tomatoes began to ripen and then increased during the late stages of ripening. Both C2H4 biosynthesis and respiration rate were stimulated during the chilling response early in ripening. In the nonripening mutant, nor, chilling sensitivity did not show the early decline but showed the increase during senescence. Variation in chilling sensitivity during tomato ripening was biphasic, with a decline at the onset of ripening followed by a senescence-related increase. It is proposed that the latter may be due to an increase in membrane viscosity.
Abstract
The postharvest behavior of watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] fruit harvested at selected stages of development and stored in air or exposed to 50 μl ethylene/liter or 6500 μl propylene/liter was investigated. Characteristics measured included the effects of ethylene or propylene on ripening, respiration, ethylene production, and fruit firmness. Ethylene treatment induced a rapid deterioration of fruit at all maturation stages, as evidenced by the acute placental tissue softening and watersoaking. Melons of all maturation stages held in air showed little textural change throughout storage and produced only trace quantities of ethylene. Respiratory activity of fruit at each maturation stage was enhanced in the presence of ethylene or propylene and returned to normal rates upon removal of the gases. Ethylene production was not initiated by exposure of fruit to propylene, and was detected only in fruit exhibiting symptoms of decay. The results support the conclusion that watermelon fruit exhibit a nonclimacteric pattern of ripening.
Abstract
Internal ethylene levels, fruit firmness, soluble solids content, and starch–iodine reaction in ‘Delicious’ and ‘Golden Delicious’ apples (Malus domestica Borkh.) were measured weekly for 6 to 8 weeks during fruit maturation for 3 years. Internal ethylene level did not consistently correlate with minimum maturity as judged by agricultural inspection or optimum maturity as judged by a taste panel in either cultivar. Internal ethylene levels ranged from 0 to 26 μl·liter−1 in ‘Delicious’ and 0 to 41 μl·liter−1 in ‘Golden Delicious’ on taste panel harvest dates. Decreases in fruit firmness and increases in starch conversion and soluble solids content were observed prior to any increase in internal ethylene in both ‘Delicious’ and ‘Golden Delicious’. Thus, internal ethylene concentration is not a reliable index of maturity for harvest determination for immediate sale on the fresh market. The combination of fruit firmness decrease, soluble solids increase, and conversion of starch seem to be more closely tied to perception of maturity by both the agricultural inspectors and taste panel.
Fruit were harvested from an erect, thornless blackberry (Rubus L. subgenus Rubus Watson, `Navaho' to study ripening changes. Soluble solids content increased between the red (unripe) and dull-black (overripe) stages of ripening while titratable acidity decreased sharply between the mottled and shiny-black ripeness stages. Anthocyanin content increased sharply between the mottled and shiny-black stages. Firmness of drupelet and receptacle tissues decreased between the mottled and shiny-black stages of ripeness. In whole blackberries, total uronic acids decreased, and water soluble uronic acids increased between the green-red and shiny-black ripeness stages. Volatile production paralleled ripening changes, and was highest in dull-black fruit, with alcohols and aldehydes predominating. Respiration of intact fruit maintained in water decreased between the green and red ripeness stages and increased at the mottled (part-black) and black ripeness stages. Ethylene production remained below 10 nmol·kg-1·h-1 until the dull-black (overripe) stage of maturity. Free 1-aminocyclopropane-1-carboxylic acid (ACC) and ACC oxidase did not increase in berries until the shiny-black stage, corresponding with the onset of detectable ethylene production. ACC oxidase activity decreased in the drupelet tissue (0.5 to 0.01 μmol·kg-1·h-1) and increased in the receptacle tissue (2 to 3.8 μmol·kg-1·h-1) as fruit changed from red to dull black. These results indicate that ripening in blackberries may be initiated in the receptacle tissue. Ripening in blackberries is likely independent of ethylene, but ethylene may regulate berry detachment from pedicels, thus controlling timing of fruit harvests.
Abstract
Equatorial 7-mm-thick slices of mature-green tomato fruit (Lycopersicon esculentum, Mill., cv. Castlemart) ripened normally, and changes in the concentrations of lycopene, soluble solids content, and titratable acids and in pH were analogous to, although in some cases significantly different from, changes in whole fruit that were harvested when mature-green and ripened. An untrained taste panel scored ripened slices acceptable to good, and no off-flavors were detected. Slices of mature-green tomato fruit can be ripened to an acceptable level of quality, and could provide an additional outlet for fresh-market tomatoes to the home and institutional markets.