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Open access

A.G. Calbo and N.F. Sommer

Abstract

A technique to measure intercellular air volume was developed, based on the relationship between pressure reduction and air expansion, with correction for water vapor pressure. This technique yields air efflux curves, and the extracted air can be used to measure the gas composition of internal atmospheres. ‘Grevenstein’ apple (Malus domestica Borkh.), ‘Bartlett’ pear (Pyrus communis L.), ‘Hayward’ kiwifruit (Actinidia chinensis Planchon), ‘Independence’ nectarine [Prunus persica (L.) Batsch], and ‘Russet’ potato (Solanum tuberosum L.) had intercellular volumes of 16.6%, 5.14%, 3.64%, 5.76%, and 1.64%, respectively.

Open access

E. C. Maxie, N. F. Sommer, and F. G. Mitchell

Abstract

Since World War II, the news media have occasionally carried stories claiming unusually long shelf lives for irradiated fruits and vegetables, often at room temperature. The biochemistry and physiology of senescence make these claims biologically absurd. True, an uncritical review of the “scientific” literature prior to 1964 might have led one to believe that irradiation had a commercial potential for a wide variety of commodities. Many studies were of questionable validity, however. Products were sealed in airtight containers, physiological state (maturity) was ignored, quality evaluation was ignored or at best subjective, sample size was inadequate for statistical treatment, dosimetry was not reliably determined, geometry of radiation distribution into the product seemed highly variable, pathological studies were not quantitative, and often not even qualitative, and experiments were stationary, precluding exposure of the commodity to the injury associated with transport and marketing. Our studies, in contrast, covering 15 years and designed to avoid these criticisms, have led us to conclude that irradiation has technical promise for but few commodities‐‐and that economic feasibility reduces possible application even further.

Open access

E. C. Maxie, F. G. Mitchell, and N. F. Sommer

Abstract

The air transport of perishable commodities has increased markedly in recent years. A potential for an even greater volume of business is found in reduced rates and improvements in aircraft and handling facilities.

Open access

E. C. Maxie, F. G. Mitchell, N. F. Sommer, R. G. Snyder, and H. L. Rae

Abstract

At any stage of the ripeness of ‘Bartlett’ pear fruits, subsequent ripening was inhibited if the fruits were warmed to 40°C. Both production of, and sensitivity to, ethylene (C2H4) were almost totally suppressed. Even at 30°C, C2H4 production was greatly reduced in both early- and late-season fruit. Unless treated with C2H4, early-season fruit failed to ripen at 30°C although late-season fruit ripened spontaneously, presumably because of high internal concentrations of the gas. In both cases ripening was characterized by a watery breakdown of the floral end of the fruit.

At 40° and 50°C, respiratory rates declined progressively unless the fruits were treated with C2H4, whereupon a stimulation occurred although ripening was unaffected.

Gas exchange was not limiting at temperatures as high as 50°C, even when the ends of the fruits were sealed with paraffin wax. Maximum modification of the internal atmosphere of any individual fruit resulted in 15.7% O2 and 7.2% CO2. Ripening of fruits held at 20°C in that atmosphere was delayed about 3 days, presumably via mild competitive CO2 inhibition of C2H4 action.

We conclude that failure of ‘Bartlett’ pears to ripen at 40°C results from lack of C2H4 production and loss of sensitivity to the gas. The mechanisms are unknown.

Open access

J. R. Buchanan, N. F. Sommer, R. J. Fortlage, E. C. Maxie, F. G. Mitchell, and D. P.H. Hsieh

Abstract

Concentrations of patulin in blue mold lesions caused by Penicillium expansum Lk. ex Thom in pears and stone fruits were similar to those reported for apples. Of fruits tested, only the plum was a poor substrate for accumulation of the mycotoxin. The total patulin within disease lesions increased as the lesions enlarged. However, the concentration of patulin varied considerably, with the largest lesions usually yielding the lowest concentrations. Little or no patulin permeated healthy tissue surrounding the disease lesions unless fruits were overripe or had senescent breakdown.

Open access

E. C. Maxie, D. S. Farnham, F. G. Mitchell, N. F. Sommer, R. A. Parsons, R. G. Snyder, and H. L. Rae

Abstract

Cut carnation flowers shipped from California by air occasionally arrive at eastern markets in a senescent condition with losses greater in the warm autumn months. CO2 and C2H4 production by the flowers has a pattern similar to that of climacteric-class fruits, with senescence correlated with a rise in release of the gases.

Cut carnation flowers show an enormous increase in respiratory heat with increasing temperature: 89 BTU/ton/hour at 0°C versus 14,718 at 50°C. In C2H4-free air, the flowers tolerate elevated temperatures but their vase life is reduced. Their sensitivity to C2H4 increases dramatically with increasing temperature, with the threshold concentration partially depending on prior stresses on the flowers.

Flowers in containers exposed to direct sunlight developed temperatures as high as 49.5°C. Air temperatures inside containers shipped via jet aircraft were as high as 35°C. The C2H4 concentrations in the containers may reach 10.5 ppm.

The remarkable resistance of cut carnation flowers to mechanical injury, combined with their low metabolic rates at low temperatures, makes refrigerated surface shipments feasible and perhaps economically desirable. Their resistance to injury seems related to their light weight, the damping action of the petals, and the lack of phenolase or readily oxidizable phenolic compounds in the petals.