GASSING APPLES

Evening Post, Volume CXXIII, Issue 136, 10 June 1937, Page 20

GASSING APPLES

TO KEEP THEM FIT

BETTER THAN COLD STORAGE

NOVEL EXPERIMENTS

That apples actually breathe, taking in oxygen and giving out carbon dioxide gas after the fashion of human respiration, may surprise those whose knowledge of plant physiology has not extended beyond the fact learnt at school that plants in their breathing do the reverse of what human beings do—that is, they take in carbon dioxide from the air and give off oxygen. And it will probably surprise them still more to know that in an experimental, laboratory attached to the Department of Scientific and Industrial Research in Sydney Street one can actually see luscious and rosycheeked apples having their rate of respiration measured.' This,- however, is but a minor phase of some very interesting and important experimental work which is going on there in connection with the gas storage of apples. Apples, and all other fruits, are living organisms, and as they ripen (whether on or off the tree) they undergo various complicated physiological change's. A; climacteric is reached: the apple is ripe, and all its starch has been converted into sugar. But the big internal changes which have taken place in the fruit do not cease: they continue, disintegration sets in, and the apple begins to rot, as it is called. Now what science is trying to do is to slow down the life processes going on in the ripening apple, in order that it may be stored for consumption at a time when Nature does not arrange for a supply of fresh apples. When ordinary cold storage came to be applied to meat and to other produce, it was naturally thought that here would be a simple way of keeping apples: just freeze them, or at any rate chill them, and keep them in cold storage until needed. This sounded right enough in theory, but in practice it by no means proved a perfect method of storing apples. Their condition after a period of cold storage was not always what that of a good marketable apple should be. The tissues of'the apple were apt to break down, and the fruit became useless Cold, storage of fruit is of course not solely a matter of temperatures: problems such as that of humidity have to be considered. But even when cold storage conditions are as perfect as man at present knows how to make them the problem of keeping apples is not altogether solved satisfactorily. EXPERIMENTAL GAS CHAMBERS. Science now thinks that there is a better way, and that is by keeping the apples stored in gas chambers, in .a special atmosphere of carbon dioxide and oxygen. As was pointed out at the beginning of this article, apples in the process of ripening breathe out carbon dioxide, and several years ago the experiment' was tried of allowing, apples to remain in their own exhaled gas without a fresh supply of oxygen, with a view to retarding ripening. But this proved to be a failure, for the Cruit suffered from internal break down. -'It'is now known that an excess of carbon dioxide while an apple is in cool storage induces what is kndwn as brown heart Lack of oxygen, it hhs also been-discovered, causes deep scaldv Brown heart starts to;aer I'elop round the core of the/apple and cannot be detected-from the outside until the deterioration is far advanced. Indeed an apple so .infected may be very good to look upon.ibut as an article of diet it is useless, Deep scald, on the other hand.' starts on the surface and works inwards. Kesearch workers in England and elsewhere, however, have never admitted defeat: indeed," failures in cool storage' methods have: spurred them on to further investigations.. Having ascertained the normal requirement of an' apple during its ripening process—what percentage of ■ oxygen ;it needs in' the atmosphere for normal respiration and what percentage of carbon dioxide it exhales— obviously the thing to try to do was to give the stored apples their normal requirements, but at a temperature which would slow down the*ripening processes for a sufficiently lengthy period, This temperature need not be so low as that required for ordinary cold storage, which is a distinct advantage, since the lower the temperature the. more susceptible the apple is to internal break down. - A SCIENTIFIC WONDERLAND. Hence one can see in the spaci/! laboratory which has been built for the Department of Scientific and Industrial Research a number of steel Cabinets in which are stored oil numbered trays apples which are being sacrificed on the altar of science. Above the laboratory are large gas containers which feed oxygen and carbon dioxide to the steel cabinets. The cabinets in each of the three chambers have a different gas mixture, the oxygen ranging from 9 to 15 per cent, and the carbon dioxide from 12 to 6 per cent. There is a range of temperature, too, from 35 to 43 degrees Fahrenheit. Each apple is wrapped in special oiled paper to prevent scalding of the surface tissue. Humidßy, too, is under control, and in fact the whole x rM file apparatus in the laboratory is fitted with an amazing number of gadgets, automatic and electrical' controls, etc.

The anples will be examined after six weeks or. a couple of months to see how they have fared: comparisons will be made between those from th!e various chambers, and from the data available will be deduced what is the optimum gas mixture, temperature, etc. The goal is the discovery of a eas mixture . which will allow apples to be stored for a longthy period, for months'on end in fact, so that they can be placed on the market in the best, of condition and without deterio-' ration in flavour long after their normal1 season.

Apples in ordinary conl stores arel now taken out at any time required, the criance being taken whether they are in good or bad condition. But it will be different with gas-stored apples. Once they are placed in the gas chambers there they must remain, for perhaps three months or more, until the ripening process is completed. The length of time reauired will-be care-: fully worked out beforehand, and the; owner will know almost to the day when his fruit is ready for/.the mar-; ket. Even if the goal aimed; at is not reached immediately, the present experiments are going to tell the research workers much about the behaviour of gas-stored apples , which they did not know before—knowledge which will be invaluable in future experiments. ■