Advances in Starch Study ERIC H A R D Y , 4 7 Woodsorrel Road, Wavertree, Liverpool 1 5, Ensland
TPHB wartime importance of starch makes interesting some of the recent advances made in the study of this carbohydrate in different countries. In India, where the cowpea (Vigna catjang) is an important food crop, studies of its properties have been made (2). Analysis of seeds from the long-podded variety showed 39.2 per cent starch and 11.12 per cent soluble carbohydrate. Methods similar to those used commercially in producing cereal starches were applied to the cowpea in the laboratory, and the yields were 20 per cent white starch (87.3 per cent starch, 10.02 per cent moisture, and 0.14 per cent ash) and 74.4 per cent pulp (36.22 per cent protein, 23.1 per cent crude fiber, 27.55 per cent starch, 8.17 per cent moisture, and 4.4 per cent ash). A 3 per cent cowpea starch paste heated to 90° C had a viscosity somewhat higher than that of wheat starch, but lower than that of Indian corn starch. However, as the cereal starches decreased in viscosity upon continued heating, the cowpea starch had the highest viscosity after 30 minutes. Gelatinization was found to be slower in cowpea starch than in cereal starches. This relatively small viscosity variation over a wide temperature range renders cowpea starch useful in textile sizing and as a thickener in calico printing. In Ajmerica the physical nature of starch has been further studied by Schoch who, in a recent paper (3), dealt with degrada tion and other important points of starch behavior. Degradation into a mushy paste when it is peptized by an alkali or other peptizing agent and the agent then removed, is well known. This degradation is faster and more complete at low than at high temperatures. Surface degradation * arises in the skinning of boiled starch paste by evaporation. Autoclaved starch solu tions degrade on standing, and degradation is faster the higher the starch concentra tion. Alkali-peptized starch does not de grade o n standing, nor by freezing or evaporation. Degradation arises in the precipitation of starch from pastes or solutions, and this precipitated starch will not dissolve to its former degree of dispersion, even after being autoclaved. High acidity favors degradation, but when acidity is high enough (pH less than 3) hydrolysis of the starch lessens the quantity of precipitate by forming soluble products. Starches which h a v e been solubilized by dextrinization, oxidation, or ethvlation do not de grade readily. They do not skin easily, and if a skin does form it can be redissolved. Such aspects of starch behavior indicate that the affinity of starch for water is 1688
opposed b y the stronger association forces acting between starch molecules. Hydra tion, therefore, can be carried past the gel stage to the colloidal solution stage only with extreme difficulty, and such a col loidal solution degrades easily. A dis sociating force stronger than that of water is needed to solubilize starch. Reference should be made here to Radley's new book on "Starch and Its Derivatives" ( / ) , especially because of the increased commercial interest in the manu facture of starch and its derivatives and the connection with potato starch, dextrin, and glucose. More work must be done before the chemical structure of starch is finally and thoroughly understood, since much of the present literature is conflicting, and re search and observations have been made under different conditions. The bacterial fermentation of maize made by Weizmann during the last war introduced a new source of acetone, but this process has been little used in Britain, where potatoes and horse chestnuts form the chief source of starch. Starch now plays so important a part in the paper and textile industries that its importance as a food source may not al ways receive its share of attention. Doubtless the future will see greater im portance attached to starch iodine, the ethers and esters of starch, the manu facture of starch sirup, glucose sirup or
corn sirup, glucose, and commercial dextrose. In America dustless starch grits have been made from raw starch and a small quantity of gelatinized starch, starch has been converted into a sugar mixture con taining between 65 per cent and 70 per cent dextrose equivalent by use of molyb denum catalyst, and it has also been con verted to paste with a relatively high starch solid content and low consistency through use of a strong solid acid salt of an amino acid. Thin boiling properties have been given by a water-soluble acid salt of an amide, and it has been made soluble by heating in the presence of water and persulfate. Literature Cited (1) Radley, J. A. t "Starch and Its Deriva tives", New York, D. Van Nostrand Co., 1940. (2) Sarin, J. L., and Qure3hi, M. H., Ind. Eng. Chem., 33, 640 (1941). '3) Schoch, T. J., Cereal Chem. 18, 121-8, (1941).
L i q u i d Carbon D i o x i d e in Fire Extinguishing CpNGiNEERS saw liquid carbon dioxide on public display for the first time in the Cardox Corp. exhibit a t the 31st Annual Safety Congress and Exposition in Chicago. The liquid carbon dioxide was contained in a miniature, mechanically refrigerated storage tank of about 30-pound capacity, specially built for the exposition. For the usual all-steel construction thick trans-
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parent plastic ends were substituted on the tank. A miniature, composite industrial plant was created for the Safety Exposition to show many times daily a small-scale rep lica of a typical Cardox engineered fireextinguishing system in operation. A low-heat alcohol fire was used t o activate the system, which automatically detected the fire within a matter of seconds and sounded an alarm bell. A short period was allowed for the imaginary workers to leave the plant before the automatic discharge of carbon dioxide began. While the fire was extinguished almost instantly, the discharge continued long enough to eliminate any possibility of reignition.
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Sterilization with Gas Τ Π Η Ε Department of Agriculture has long employed methyl bromide and it has been used by private business concerns for disinfecting clothing, buildings, plants, etc. Not long ago, a model gas sterilizer was set up by the Department of Agriculture and submitted to Camp Lee's Sterilization School for experiments in creating a standard mobile gas sterilization unit. A complete new gas sterilizer was set up, which is now in the process of manu facture, for use with regular Army units in the field. The new portable unit can be set up in 17 minutes, 20 seconds and can take care of from 65 to 75 men's clothes. The entire unit is collapsible, and two units can be set up in a single large wail tent. It is planned that a mobile sterilization company will use six units encompassing one run or cycle per hour. On that basis, one company consisting of s i x units can sterilize clothing for 450 men per hour; and in a 16-hour day the total amount of clothing sterilized will be sufficient for 7,200 men. Taken apart, the equipment is so com pact and light that two entire units can be carried together with motors, tents, and all other essential equipment, in one truck. A trailer carries shower equipment for bathing facilities. Methyl bromide comes as a liquid, and the equipment is set u p so that it will drain through copper tubing, in the form of a coil, immersed in water heated above atmospheric conditions by the exhaust from the portable motor that operates the unit. The liquid turns rapidly to vapor because of the heat in the coils and the low boiling point. The gas is passed into the shaft and blown into the sterilizing chamber by an air circulator run by the air-cooled motor. A complete cycle or run takes 60 minutes.
M o b i l e gas sterilization unit from the rear
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M o b i l e sterilization unit is about to be used in experiment in stee-ilizitig mattresses. Ingenious "pivot bolts" hold sections together with edges tight, scaling the inside.
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