N.Z. VEGETABLES

Wanganui Chronicle, Volume 87, Issue 28, 4 February 1943, Page 6

N.Z. VEGETABLES

DEHYDRATION SCHEME EXTENSIVE GOVERNMENT UNDERTAKING. (P.A.) Wellington, Feb. 1. The Hon. D. G. Sullivan. Minister in charge of the Department of Scientific and Industrial Research, to-day reviewed the research and developmental work in vegetable dehydration which has been initiated in New Zealand by his department and now been successfully brought to the stage of full-scale commercial production for the Armed Forces. Fresh vegetables contain from 80 to 95 per cent of water and the aim of dehydration is to remove almost the whole of that water (dried vegetables contain from 2 to 4 per cent of water) without impairing in any way the dietetic value of the food and without affecting to any appreciable extent the appearance and natural flavour of the vegetables when they are ultimately re-constituted in water and cooked for use. Advantages of Dehydration. The main advantages of dehydration lie in the great saving of weight, the saving of bulk and containers, and the ability to provide vegetables in the diet in localities where fresh vegetables cannot be grown. The magnitude of the saving of weight may be appreciated from the fact that the equivalent of approximately 18 tons of fresh cabbage, 10 tons of carrot or onion, and six tons of potatoes is contained in one ton of the dehydrated products. Dehydration of vegetables first came into prominence during the last was but was not satisfactory owing to failure to recognise the basic principles involved. The industry all but died during the next 20 years or so. and it is only comparatively recently that the essential foundations for satisfactory processing have come to be appreciated. This has been due to scientific investigations which have revealed that reconstitution of dried vegetables cannot be satisfactorly accomplished unless particular attention is paid to varieties, pre-treatment, temperature and humidity of drying, all of which make all the difference between a product which is tough, leathery and unpalatable, and one which when cooked can scarcely be distinguished from fresh material. Research is proceeding in Great Britain, the United States of America. Canada, and Australia, as well as in New Zealand, and while commercial production is now being achieved in countries overseas it must be emphasised that further improvements in several directions are still waiting to be effected. The N.Z. Department of Scientific Industrial Research has kept in close touch with overseas work and is posted with the latest developments in both research and commercial production. New Zealand Experiments.

Work in New Zealand was begun in April of last year in response to a request from the Fighting Services to investigate the possibility of producing dehydrated vegetables in the Dominion for their requirements. Preliminary investigations were carried out by officers of the Department of Scientific Industrial Research at its Plant Chemistry Laboratory at Palmerston North. The vegetables studied were potato, cabbage, carrot, parsnip, and onion. Successful methods for the processing of these types were worked out, and samples of the finished products were submitted to and approved by the three services. In brief the process consists of washing, trimming, and slicing, shredding. or cubing the vegetables, followed by a short scalding treatment that is necessary to preserve colour, favour, food value, and keeping fUaliW. and that also facilitates the of water when th<* vegetables are cooked for use. The vegetables are next spread out on wire-mesh trays and are dried in an insulated tunnel through which a strong current of heated, dry air is circulating. Bofh temperature and humidity of this air are carefully controlled to obtain maximum drying rate without overheating the produce. When the drying is completed the vegetables have a moisture content of only 2-4 per cent., and they are then Immediately packed into moisturetight tinplate cans. Dried vegetables readily absorb moisture from the air and hence it becomes absolutely essential to pack them in airtight containers. otherwise spoilage from the attacks of mould and bacteria quickly results. This description is apt to give the impression that the process If a very simple one. but if a good j

product is to be obtained, then the utmost care and attention has to be devoted to every stage of the process. Preparation of dried vegetables for the table is carried out simply by putting them into boiling salted water and simmering till fully cooked—a process which normally takes from 25 to 45 minutes, according to the vegetables. Commercial Production. In view of the success of the initial experiments it was decided to commence full-scale commercial production. For this purpose it was necessary to develop designs and specifications for a dehydration plant that would be suitable for New Zealand conditions. The Chemical Engineering Section of the Dominion Laboratory, one of the branches of the Department of Scientific Industrial Research has been responsible for this work. Fruit dehydration is well established and its principles thoroughly known and proved. The same is not true of vegetables which present problems of a very different and mucn more difficult nature. There are in operation many types of driers for treating plant products. The Chemical Engineering Section has in recent years given close attention to a number of plant drying problems, and the extensive experience gained has enabled the development of a design, embodying the best features of overseas types, together with some entirely new features which should prove effective in yielding a product of the highest quality. The Government, through the Food Controller, has arranged for the first commercial plant to be installed at Messrs. Wattie Canneries Ltd., Hastings, and for the output to be supplied to the Armed Forces.

Erection of the plant is now in progress and operation will commence in the coming season. The plant is the first of its kind to be established in New Zealand, and will be capable of processing several thousand tons of fresh vegetables per annum. Since the plant has been developed expressly for vegetable dehydration it will be one of the most up-to-date units in Australasia. It has been designed for continuous operation 24 hours per day, and special attention has been paid to the hygienic handling of raw material and finished product, and to conservation of the valuable food constituents of the fresh vegetables. Retention of vitamin C (the anti-scurvy vitamin) in such vegetables as potato and cabbage is a feature of the process, and, contrary to what might be expected, it is actually possible by adoption of scientific control to produce dehydrated cabbage which when cooked will have a higher vitamin C content than cooked fresh cabbage. The dietetic value of the products will thus be beyond question, and in flavour and apnearance thev can scarcely, if at all, be distinguished from the fresh product. Further Development Work.

Common to all countries engaged in vegetable dehydration are certain problems of production and packaging that need further study, e.g., the compression of the dried vegetables into a still more compact form, the development of a satisfactory continuous scalding apparatus, and the packing of the product in nitrogen instead of in air. As soon as the dehydrator is in operation, the Department of Scientific Industrial Research is proposing to carry out investigations of those problems so that still further improvements can be put into practical effect as soon as possible. Another essential investigation being carried out by the department is the growing of every obtainable variety of the different vegetables to ascertain which are suitable for dehydration and which are unsuitable. Considerable variation is being found to exist, and the results of this work will enable mistakes in planting to be avoided.