GENERATION OF CONTROLLED ATMOSPHERES BY UTILIZING FRUIT RESPIRATION

A completely different method of quality preservation has been tried in the People's Republic of China. In caves in the deep sediments of the big rivers which have traditionally been used for the preservation of food, foil tents are set up in which freshly harvested, warm apples, by their respiratory activity, produce very quickly a strong CO₂ increase and a corresponding O₂ reduction in the storage atmosphere. CO₂ concentrations of 15–18 % are then gradully reduced to about 10 % by the clever arrangement of exchange chambers with semi-permeable membranes. The desirable final oxygen concentration is about 5 %; a final temperature of 5 °C is reached only slowly in the course of about 6 –8 weeks.

Without questioning those conditions which have been found optimal for long-term storage in Western industrialized countries, it seemed interesting to us to find out whether they may be achieved at less expense for cooling and atmospheric changes. Preservation of the fruit quality thereby remained the essential criterion.

After two years's experiments at the laboratory scale had shown that commercially important cultivars such as Golden Delicious, Jonagold, Idared and Melrose tolerated correspondingly high CO₂ concentrations without damage, and that quality preservation of the fruit was even clearly better than of fruit stored in cold stores in normal atmosphere (Bohling, H., 1989 a,b) - which was confirmed by the results of measurements of respiration activity and ethylene production (Figeres 1–2) - we started trying the method on a nearly commercial scale.

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