CARRIAGE OF MEAT

Otago Daily Times, Issue 22068, 26 September 1933, Page 9

CARRIAGE OF MEAT

ATMOSPHERES IN SHIPS' HOLDS

(From Odb Own Correspondent.) LONDON, August 5.

Some useful information has been gained during the year (according to the report of the Food Investigation Board, H.-M. Stationery Office, ss) with regard to the control of atmospheric conditions in ships' holds, partly by experiments on a ship during a coastal voyage and partly by an analysis of data available from the voyages of ships carrying cargoes of fruit. The ships concerned have been of the type designed in the first place for the carriage of chilled meat, and the results have a special interest in view of the discovery that the growth of moulds and bacteria on chilled meat can be considerably retarded by storage in an atmosphere containing from 10 to 15 per cent, of carbon dioxide. EFFECT OF VENTILATION.

Although the atmosphere in a refrigerated hold is uniform in composition at all points so long as it is not ventilated, this is no longer the case when ventilation has been secured, for example, by extraction through a thermometer tube. The local and temporary irregularities in composition so produced mean that samples taken during or immediately after ventilation may give a Cjuite erroneous impression of the average composition of the atmosphere in the space. Observations in the experimental hold have since provided abundant confirmation of this fact.

Moreover, there is normally an equilibrium between the free atmosphere of the hold, the atmosphere inside the fruit boxes, and the gases in solution in the fruit itself. This equilibrium is upset by ventilation, which in the first instance only displaces carbon dioxide from the free atmosphere of the hold. In a wellfilled hold about two-thirds of the carbon dioxide is inside the fruit boxes, and about half of this is inside the fruit itself. To approximate to a new equilibrum is a matter of several hours, and in the meantime the analysis of samples drawn from the free atmosphere of the hold is misleading as an index of the concentration of the gas in the tissues of the fruit, which is. of course, the value of physiological importance. Some work now in progress to determine the amount of carbon dioxide held in apples in equilibrium with various mixtures, and the speed with which this gas can be displaced, will have an important application in this direction. ATMOSPHERIC CONTROL.

In carrying fruit, the main practical problem of atmospheric control at the moment is the avoidance of excessive amounts of carbon dioxide. In extending the principle of gas storage to the carriage of chilled meat overseas in atmospheres containing from 10 to 15 per cent, of carbon dioxide, the main problem would be to retain the gas sufficiently well to make the project economically feasible, and considerable attention is now being given to this problem. An atmosphere containing 10 to 15 per cent, of carbon dioxide could be maintained in insulated spaces designed as at present, if a cheap supply of the gas were available. The possibility of using ex-haust-gas from the ships' furnaces or engines may not be an altogether impracticable one. The amount required becomes relatively less the larger the space under one hatchway devoted to gas-stor-age. A hatchway covering decks with a total capacity of 100,000 cubic feet, leaking at the rate of, say, 20,000 cubic feet a day, would need about 100,000 cubic feet of carbon dioxide for the voyage from Australia to this country. GAS-TIGHT HOLDS.

In the second place, it would undoubtedly be possible to make the hatchways of existing vessels more gas-tight than they are, perhaps by employing metal hatch-covers, perhaps by the use of rub-ber-sheeting or some similar material. Or, thirdly, it seems likely that good results could be obtained, leaving the hatches as they are, by dividing the decks into smaller chambers by means of steel partitions, trunking off the hatchway, and loading these chambers through small, and relatively gas-tight doors, from the hatch-trunk. The latter space would then be used for frozen meat or some cargo not requiring gas-storage conditions.