A high CO2 slow cooling CA storage procedure was developed for `McIntosh' apples (Malus domestica Borkh.). The apples were cooled from 18° to 3°C in 15 days in atmospheres containing a constant O2 at 2.5% and decreasing CO2 starting with 12% and ending at 3%. The results of several tests in a flow-through simulated CA storage system revealed that the new procedure was nearly as effective as rapid CA and was much more effective than traditional slow CA in preserving the firmness of `McIntosh' apples for up to 4 months of storage. Maintaining a constant CO2 either at 12% or 3% instead of gradually decreasing it from 12% to 3% during the slow cooling period resulted in more storage disorders or/and softer apples.
Five cultivars of apples (Malus domestica Borkh.) each with 2 different harvest dates were stored in continuous flow controlled atmosphere (CA) at 3% O2 and 3% CO2 at 0°C or 3.3° for 3 to 7 months. Ethylene in the CA was maintained at 3 levels: low (mostly below 1 ppm, maximum 3.8 ppm), 10 ppm and 500 ppm. In comparison with low ethylene, 10 ppm and 500 ppm ethylene in CA did not significantly affect the soluble solids, titratable acids, firmness and sensory evaluated ripeness of ‘Delicious’, ‘Golden Delicious’, ‘Indared’ and ‘Cortland’ apples harvested on either date and of ‘McIntosh’ apples harvested after the onset of climacteric. However, ‘McIntosh’ harvested before the onset of climacteric retained higher acids, firmer texture and were sensory evaluated as less ripe when kept in CA with low ethylene than that with 10 or 500 ppm ethylene. ‘Delicious’ apples stored for 7 months in CA with 10 or 500 ppm ethylene developed severe scald but those in CA with low ethylene did not.
‘McIntosh’ apples (Malus domestica Borkh.) were harvested on 3 different dates and stored in controlled atmosphere (CA) storage with less than 1, 10 or 500 ppm ethylene. After 5 and 8 months of storage the fruits which had been harvested 5 to 6 days before the onset of the climacteric were less ripe and had less breakdown than fruits harvested after the onset of the climacteric. The fruits harvested at the preclimacteric stage had either comparable or slightly better eating quality but less red color than fruits harvested later. High levels of ethylene had slight but statistically significant negative effects on firmness and acidity of early harvested fruits judged by sensory evaluation after 5-month storage plus 7-day holding and by objective evaluation after 8-month storage plus 1- or 7-day holding at 21°C. An attempt was made to find a method to estimate the physiological age of preclimacteric apples. The minimum treatment time required for 10 ppm ethylene to trigger the onset of the climacteric at 21°C is judged to be promising.
High temperature (40°C) for 2 and 4 days lowered the acidity of 4 cultivars of apples (Malus domestica Borkh.). The preheated fruit was firmer than the control during 2 to 4 weeks of holding at 21°. The treatment also accelerated the loss of chlorophyll from the fruit skin. The soluble solid content of the fruit was not affected. Apples after the heat treatment had a normal respiratory climacteric and normal ethylene production rates. Some feasibility of applying high temperature to improve apple quality seems to exist.
Good correlation was found between length of storage life of banana (Musa cavendishii Lambert cv. Dwarf Cavendish) and minimum treatment time required for ethylene ripening response at harvest. All test bananas responded to 24 hours or less of 10 ppm ethylene treatment. Based on 29 sample groups of greenhousegrown ‘Dwarf Cavendish’ bananas, a linear regression equation relating banana storage life in days in air at 21°C (as output Y) and minimum time in hours required for ripening response to 10 ppm ethylene (as input X) was obtained as Y = 4.59 + 1.25X. The 2 variables had a correlation coefficient of 0.92.
Ten to 100 ppm ethylene in air inhibited the development of superficial senescent spots on ripe bananas (Musa cavendishii Lambert cv. Valery). The ethylene did not affect the respiration rate but accelerated softening of the partially ripe or ripe bananas at 21°C. Six days of continuous exposure to 10 ppm ethylene did not affect the eating quality of bananas but 9 days of exposure slightly lowered the quality. Ethylene did not inhibit anthracnose (Gloeosporium masarum Cke. & Mass.) growth on banana fruit or on petri dish culture. Dipping ripe bananas in 100 to 1000 ppm (2 chloroethyl)phosphonic acid (ethephon) did not inhibit the senescent spot development. Brief dipping in silver nitrate solution (50 mg/liter) counteracted the ethylene effect.
‘Dwarf Cavendish’ bananas (Musa cavendishii, Lambert), which were pretreated with ethylene and stored 28 days in 1% O2 or in 1/10 atmospheric pressure at 14°C, remained green and firm until the end of storage, but started to ripen almost immediately after being placed in 21°C air without additional ethylene treatment. The bananas so treated and stored had normal eating quality when ripe. The key to success was a pretreatment with ethylene for a period of time equal to the minimum required to induce the ripening response. Longer periods of ethylene pretreatment caused bananas to ripen in storage. The data suggest ethylene inactivates a natural ripening inhibitor.
The sensitivity of ‘Dwarf Cavendish’ bananas (Musa cavendishii, Lambert) to ethylene was affected by the physiological age of the fruit and by the composition of gases ambient to the fruit. Ethylene at a concentration of 0.1 ppm in air always shortened the length of the preclimacteric period at 21°C. Exogenous ethylene at concentrations of 0.015 − 0.05 ppm, which were lower than those of endogenous ethylene of the fruits, was effective with 2 out of 3 lots of bananas tested. Low O2 and high CO2 concentrations in the storage atmosphere reduced the sensitivity of bananas to ethylene. The minimum effective concentration of ethylene in a gas mixture containing 4% O2 and 7% CO2 was between 0.1 and 0.5 ppm for bananas with highly advanced maturity and was between 0.5 and 1.0 ppm for bananas with less advanced maturity.
Daminozide-treated and non treated ‘Delicious’ and ‘Idared’ apples (Malus domestica Borkh.) were stored for 7 to 7.5 months in simulated low-ethylene (<1 μl·liter−1) or normal-ethylene (500 μl·liter1) controlled-atmosphere (CA) storage. The simulated CA storage was a flow-through CA storage in 19-liter jars at 0°C. The storage atmosphere contained 2.5-3% O2, 3% CO2, 94-94.5% N2, and nearly 100% RH. Nontreated ‘Delicious’ and ‘Idared’ apples did not respond to low-ethylene CA, except that low-ethylene CA reduced the incidence of storage scaled on ‘Delicious’ apples. Daminozide-treated ‘Delicious’ apples did not respond to low-ethylene CA; the apples being firm after both low-ethylene and normal-ethylene CA storage. The response to low-ethylene CA by daminozide-treated ‘Idared’ apples was a reduced rate of softening of the apples after storage. The daminozide treatment significantly suppressed the ethylene production of both cultivars of apples in simulated low-ethylene CA storage. Chemical names used: butanedioic acid mono(2,2-dimethylhydrazide)(daminozide).
‘McIntosh’ apples (Malus domestica Borkh.) from trees field-sprayed with daminozide were kept in unstoppered 19-liter jars in air at 3.3°C for various periods of time before being sealed and exposed to low-ethylene controlled atmosphere (CA). Similar apples were kept in sealed jars with flow-through low-ethylene CA at 20° for various periods of time before being cooled to 3.3°. After the prestorage treatments of delayed establishment of low-ethylene CA storage (delayed CA) or delayed cooling, these apples were stored in the same jars with a flow-through simulated low-ethylene CA (2.5-3% O2, 3% CO2, <1 μl·liter−1 ethylene, 2.2°-3.3°) for 7.5 months. Delayed cooling or delayed CA for one to 4 days had little adverse effect on the keeping quality of the apples. Delayed cooling for 5 days or delayed CA for 5 to 7 days caused slight decreases in fruit firmness and acidity after storage and sometimes caused slight increases in ethylene production of the apples during storage. Delayed cooling for 7 to 11 days or delayed CA for 9 to 11 days often caused significant decreases in firmness and acidity and large increases in ethylene production. The adverse effect of extended periods of delayed cooling was greater than that of delayed CA. Chemical names used: butanedioic acid mono (2,2-dimethylhydrazide) (daminozide).