BROWN HEART

Evening Post, Volume CVI, Issue 81, 3 October 1923, Page 15

BROWN HEART

FOOD INVESTIGATION BOARD

A FORM OF SUFFOCATION.

(PROM OUR OWN CORRESPONDENT.)

LONDON, 17th August:

" Brown" heart " in apples, pears, and potatoes is the subject of the special report {No. 12) issued by the Department of Scientific and Industrial Eeßearch of the ' Food Investigation Board (of -which latter body, .hy tha •way, the name of the-Hon. Sir Thomas Mackenzie is still included as one of the members).

The report, most realistically illustrated, deals chiefly with the functional disease as it occurs in apples and pears, and is signed by Franklin Kidd, • D.Sc., and Cyril West, D.Sc. To these'two investigators the description- /-'brown heart " owes its origin.. In 1918, in [the course of certain storage trials,, .some of the apples, externally, apparently sound and good, were found internally to have become brown and dead,, and investigations attributed the cause. to sriine defect in the living processes which the apple, as a live thing,' must manifest. The condition was found not to be due .to bacteria or moulds."; *

No one interested in ; the storage of apples should be without a copy" of this official report (issued by H.M. Stationery Office, 4s 6d,. entitled " Brown Heart—A Functional Disease of ' Apples and Pears "). This disease attacks home-grown as well as imported fruit, and has caused hundreds of thousands of pounds loss oh apples shipped here from Australia—a matter so serious that scientists went out to -see the 'apples gathered and packed, and to travel over with them to study the disease. The report gives some highly interesting details of a course of experiments and. a full illustrated statement on the ravages of the disease on last year's cargoes. Among the general conclusions it is stated that brown heart may occur at any stage in, the storage life of the fruit. Low temperatures increase susceptibility. Reasons are given for considering internal breakdown to be distinct from, brown heart.

A SIGN OF SUFFOCATION.

It is explained that diseases of fruit have been distinguished by botanists as " infective " and "physiological "—a. distinction the importance of which to those who have to diagnose and combat these diseases cannot be overrated. The two classes correspond to the two classes of human or animal diseases, the " infective "" and. the. ""functional." Brown heart is a functional disease of the apple. The storage trials, in ths course of which brown heart appeared, were being carried out with the object of finding a simple and a cheap methodby which the small grower could, hold his apple crop. The retarding effect Upon the ripening of the apples of increased carbon, dioxide and decreased oxygen in the air was being tried,-.and from the records of the experiments the conclusion was drawn that brown heart was due to too much carbon dioxide, combined with too little, oxygen. The. apple, as a h>.e<;sthi&g.^^eaihee,,->and. brawn heart is the sign of'a ! form of suffocation. In mathematical language, there are at least three variables- which determine the onset of the state, concentration of carbon dioxide, concentration of oxygen, and temperature. The recognition of the disease, and of its causation, would not have been of special interest beyond that of. many other incidental experimental-results, had it not been for a further chance discovery by the Food Investigation Board of its immediate and great economic importance. ■. ■-. ■-• ■

The earliest recorded case of brown heart m apples from Australia occurred 1? I!*, U\ but »*- only since 1921 that the Food Investigation Board has made examination. Last year the prevalence o brown heart condition in apples imported from Australasia began to attract general attention, and to arouse anxiety among those connected with the trade The assistance of the Food Investigation Board was sought by Mr. F. E. Pearce, of the Overseas Farmers' Co-operative Association. It was pointed out that little advance could be made except by undertaking a thorough' examination of the conditions obtaining in the holds carrying apples, especially with regard to the gases present, and that such an ■examination should properly be conducted over the whole period from the time the apples were stored to the time they left the B hip. On c of the illustrations shows ClJopatras afflicted fmm Tv h/ arti Whidl Were tak*n Horn a hold found to. contain 30 per cent, carbon dioxide and 2.5 per cent oxygen when examined by us onvt he arrival of the ship in this country. This record ls of additional"interest in that it chows the condition of the apples vFLF ™nths 3- fter removal f ™« the hold. The specimens are from a case of apples which, was -kept under observation-at ordinary 'room tem^eraDr. West that brown heart did not increase after the apples had been retim tVr °lw the hold- the itinje the photograph was taken, the apples were strti perfect external edible. Ihe brown heart areas had enown no increase in size, but had dried out, leaving cavities. INTERNAL ATMOSPHERE OF "TEw APPLE-

In setting out to. .conduct experiments upon the effect of carbon dioxide and oxygen upon bulky fruits, such as-those ot the apple or the pear, it is necessary to take into account the existence and composition of the internal atmosphere in the tissues. The internal atmosphere is the free gas in the internullular spaces of. the tissue; it is in communication with the external atmosphere through pores (lenticels) in the skin of the apple. It vis the concentration of carbon dioxide 'and of oxygen in this internal atmosphere which is of critical importance. The skin of the apple is relatively impermeable to gases, an d forms a barrier through which gaseous exchange can proceed only slowly An apple therefpre, is so -constructed- ag to constitute in. itself, as it were, a miniature gas-store. Each living",.cell- of the apple consumes oxygen and, produces carbon dioxide m respiration..- Th c individual living cells of the tissue ». garded as -umts, -maybe compared to the individual apples-in a: gas-store; the atmosphere between the. appleg in the store to the internal atmosphere between the living cells of the tissue ;'and'the skin of the appfe to the walls of the store. Even when the fruit is bathed in P: lre a'r. relatively high concentrations of carbon dioxide and equivalents low concentrations of. oxygen 'exist. in the internal atmosphere in the'tisues.. 1 Re* cent work in the Botanical Laboratory at Cambridge, carried out in association iv! th the researches upon apple metabolism promoted by the Fruit and Vegetables Committee' of the Food Investigation Board,, provides illustrative data

as to the actual composition of the internal atmosphere of apples.

LABORATORY EXPERIMENTS.

It has been.demonstrated cloarly that brown heart, in apples and pears occurs under storage conditions involving the presence of carbon dioxide above a certain danger limit in the storage atmospheres and correspondingly low (or equivalent) oxygen percentages, but that low percentage of oxygen alone or even the complete absence of oxygen do not produce brown heart: It has been shown also that the degree of susceptibility to brown hearfc varies between varieties. A number of interesting questions, however, remained to be answered. For instance, would carbon dioxide produce brown heart'in the absence of oxygen? Bow far does the concentration of oxygen present affect tho .result? How quickly will brown-.heart be produced under various conditions? ■And in .what manner, if at all, does temperature affect the result? Lastly, how far do apples vary in their susceptibility to brown- heart in relation to size, to degree of storage .maturity, to degree of maturity when gathered, to soil and cultivation?

Scientific solutions are given, and with regard to the ; first query an experiment was made with freshly-gathered Worcester Pearmains, which were stored jn airtight glass containers, each, holding thirteen apples, and iri 'the .bottom of the containers a saturated solution of common salt was added in order to prevent the enclosed atmosphere from becoming completely saturated with water vapour. A current of nitrogen from a cylinder was passed through the containers in order to sweep* out the air, and the carbon dioxide produced by the fruit was then allowed to accumulate., but not to exceed 40 per cent. As soon as analysis showed between 30 per cent. and 40 per cent, carbon dioxide present the containers were ventilated with nitrogen.

STAGE OF RIPENESS.

With the idea of ascertaining whether degrees of ripeness is a factor in the production of brown heart, one experiment was repeated six months later with apples of the same variety that had been held in cold storage during the interval, and the results obtained showed that apples late in their storage life were far less susceptible to brown heart than they are soon after gathering.

INTERNAL BREAKDOWN.

From the point of view of those who have to deal with the storage and transport of apples in practice this report upon brown heart, say the scientists, is not properly' concluded without some reference to a form of disease which is to some extent similar in appearance and easily confused'with it in description. This disease is.'generally known under the .name of "internal breakdown" (probably identical with "flesh collapse," a blemish which recently has been reported to be causing serious damage to stored apples in New Zealand). It- is, like brown heart, a .physiological or functional disease: in that its occurrence cannot be traced to the action of any parasitic organism.

"lii our experience'internal breakdown occurs only in the middle or late storage life of the apple and is not associated in any way with high carbon dioxide or low oxygen concentrations in the 'storage atmosphere. The disease appears Be-more prevalent in cold storage, than in ordinary, storage. Internal breakdown as seen in cross section of an apple usually begins as a buff or brown flush m the cortical tissue. This brown (.flush Slowly- spreads.and deepens in colour as the disease advances, but gonerally there is no .marked line of delimitation, between. it . and the; unaffected flesh. At the same time the affected is.sue, and to someextent the whole apple generally takes on "a mealy consistence, and can be easily mashed into a paste with .ones fingers. At this stage, even when the skin appears to be perfectly normal, affected apples can be readily detected hy the touch. During the early stages the skin remains sound, but as the disease spreads . and becomes 1' advanced ; the apple develops over the whole or part of its surface a dull or dark sub-qolour, due in part to the brown under-lying tissue and in part to the injectjon with water of the intercellular spaces of this tissue. A nar row strip of tissue just beneath the skin usually remains unaffected until the disease is very iar advanced. , In some cases, in which this more resistent layer of txssue is very thin, the surface of the apple may appear to have a brown flush or flushes without definite outline In advanced stages of the disease the internal tissues may' to some extent collapse so that the skin sinks down and the apple looks as if it had been subjected to pressure. The different stages of the disease do not follow precisely the same sequence in every variety of apple . . . Internal breakdown is found to be more prevalent in apples stored at low temperature.

Australian apples, I am informed, are more often affected than those from New Zealand.