SCIENCE AND FROZEN MEAT PROBLEMS

Waipa Post, Volume 31, Issue 1765, 1 June 1926, Page 2

SCIENCE AND FROZEN MEAT PROBLEMS

SEARCH FOR REFRIGERATING METHODS HARMLESS TO MEAT TISSUES. The concluding words of a scientific, addreste delivered by Dr T. Moran, a research scientist of the Food Investigation Board, before the British Cold Storage and Ice Corporation were these: — “ Given sufficient time science will in the end obtain a complete knowledge of the structure of muscle and the molecular changes it undergoes as a result of freezing and thawing.” He added: “At least the conditions will be known, which will reduce drip to a maximum.” The following are a selection of, fundamental quotations from the paper: 'Beef is not completely frozen until it has reached a temperature*of —'ss degrees C. Freezing, if it could be made to give a better product than at present, is much superior to chilling as a method for the preservation of meat.

If the life of a chilled carcase is to be prolonged beyond the time now existing in commercial practice, the first condition is that the pre-storage treatment should be carried out as rapidly and as aseptically as possible. It is a debatable point whether chilling, even if it be prolonged to, say, 60 days by economic methods, could, ever be applied to the bulk of the Australian beef trade.

iOn theoretical grounds it is certain that complete reversiblity of the frozen meat will always demand, slow thawing, or, more exactly, slow and even thawing, s o that the water frozen out during the freezing process will he under the most favourable conditions for its re-absorption. The method of thawing, however although very important is only half the problem, and it must be linked with an equally definite method of freezing which leaves the meat in the most favourable condition for the reabsorption which slow thawing aims at.

If the rate of freezing is slow enough an examination of the meat in a frozen state shows the muscle bundles in a shrunken condition surrounded by big areas of ice.

When applied to a hind-quarter of beef rapid freezing in brine does not give satisfactory results the reason being that the latent heat of freezing cannot be removed from the carcase sufficiently rapidly so that although the surface layer is frozen rapidly

the interior is not, and when examined microscopically it shows ice separtion outside the fibres and, on thawing it gives the characteristic sign of frozen meat.

The Australian National Research Council found that to eliminate drip entirely the freezing must be completed within thirty minutes, and be followed by slow thawing.

It is clear that to eliminate drip the idea of rapid freezing is impracticable with a mass as big as a hindquarter.

We can conclude that the simple principle of quick freezing to prevent drip whilst theoretically sound, is not a practical solution to the 010 hlem of beef freezing.

At present we have little certain knowledge of the wav water is held in dead muscle, and practically none of how it is held in living muscle.

Microscopic studies have shown that during moderately ,sl'ow freezing it (the skin covering each muscle fibre) is liable to mechanical rupture by growing ice crystals. AJpart, however, from damage by mechanical means, the muscle membrane may also cease to function as a result of molecular breakdown. It is considerations of this nature that will fix safe temperature limits in the frozen state.

The rate of freezing determines the mode of thawing which will secure the best results. At present, in addition to the more fundamental research on the freezing of tissues, the possibilities of partial freezing are being tried, but the experiments are not sufficiently advanced to merit discussion.

It would appear from the discussion that followed the reading of Dr Moran’s paper that neither in Australia nor New Zealand is 'there unanimity of opinion that improved chilling methods will solve the Australasian beef

'problem. Another telling point, raised by Mr R. S. Forsyth, London manager of the New Zealand Meat Producers’ Board, was that, assuming that New Zealand and Australia between them could put a regular supply of chilled beef on the British market, there is no guarantee of a remunerative price, bearing in mind that recently Argentina chilled beef has been selling as low as 21d per 1b owing to over-supply. On a long view it would seem that the solution of this difficult problem lie s somewhere between making the chilled beef less perishable or frozen beef more acceptable.