622
JOURNAL OF CIIE,'"eAL EDUC."TlON
for transportation. Distributor: Texas Company. 20 Providence Street, Boston 16, Massachusetts. Crystals Go to War: An excellent film in color showing the various steps through which rough quartz crystals go until they are made into crystals for radio use. The film begins with beautiful photographs of crystals in an exhibit at Harvard. Each step is shown in enough detail to be understood clearly, but not enough to be boring. Excellent for showing the painstaking work necessary in any precision manufacture. Recommended for high-school, college, and lay groups. 16mm., sound. 40 min. Free except for transportation. Distributor: Reeves Sound Laboratories, Inc., 62 West 47th St., New York 19. Magnesium., Metal from the Sea: A clear and detailed description of the extraction of magnesium from the concentrated brines in the sandstone beneath Midland. :Michigan, also from' the sea water at Freeport, Texas. The importance of magnesium alloys is discussed. Introduction and wind-up too long, but otherwise a good film. Recommended for high-school and lay groups. 16mm., sound. 20 min. Free except for transportation. Distributor: Dow Chemical Company, Midland, Michigan.
Working of Magnesium: Presents a very detailed and clear step-by-step procedure for machining, welding, riveting, cold working, forming, and handling of magnesium. The chemical treatment of pickling magnesium for protection is described in full. Recommended for shop instruction and those concerned with industrial work. 16mm., sound. 20 min. Free ex.cept for transportation. Distributor: Dow Chemical Company, Midland, Michigan. Guardians of Plenty: The story of the du Pont experimental work in the preparation of insectides is presented in full color. The photography, especially of close-up shots of insects, is particularly good. Recommended for high-school and lay groups. 16mm., sound. 26 min. Free except for transportation. Distributor: E. 1. du Pont de Nemours & Co., Motion Picture Bureau, Wilmington 98, Delaware. New Members Russell Meinhold, Rogers High School, Newport, Rhode Island Donald H. Miller, Hoyt Hall, Exeter, New Hampshire Sister M. Columba, OSB, St. Anthony High School, Washington. D.C.
For Longer Life
DATTY materials, whell exposed to air for even a few days, generally lose their characteristic flavor and take on an unpleasant "tallowy" odor. Although it bas been known for almost 30 years that the addition of small quantities of certain materials called antioxidants slowed down this deterioration, only recently have antioxidants been found which are harmless to human beings and can be added to food products. A large packer bas within the past few months introduced refined lard which will compete with vegetable shortenings, perhaps with far-reaching consequences. Ordinary lard has an odor preferred by some, but which unfits it for many uses. This is one of the factors causing it to sell at low prices. When refined and deodorized, its keeping power is so low that it is not a commercial article. Now the addition of an antioxidant permits processing required to build shortening characteristics into it and give the otherwise unstable refined product stability and commercial interest. In order to develop satisfactory antioxidants it is necessary to know how they work. The oxygen of the air has a tendency to attach itself to "double bonds" (unusually reactive parts of the molecules), notably to the olein and linotein content of oils and fats. At first the attachment is so slight that the oxygen is re· movable in some instances, but later the molecule may break at the point of attachment to produce two new substances, each containing firmly bound oxygen, and one of which has an unpleasant oxidized or "tallowy" odor. This type of oxidative fat spoilage can be prevented by elimination of oxygen from the neighborhood of the fat by the lise of vacuum or an inert gas, or by the presence of antioxidants. substances interfering with the usual course of oxidation. Some antioxidants grasp the oxygen morc avidly than does the fat, and hcnce keep it from the fat and slow down oxidation. Other antioxidants are thought or known to combine with and neutralize mctals which hasten oxidation. such as copper, iron, and a few others. Antioxidants arc of many chemical types, but 1ll0st of tht:
r
natural ones used in food arc phenolic substances. A common "inhibitol" or antioxidant of plant origin is the phenol. alphatocopherol, commonly known as Vitamin E. This yellow-colored oily material is soluble in fats and oils, and is found in many of those with the best keeping properties. It is present, for ex· ample, in corn, soybean. and cottonseed oils in quantities up to 0.1 to 0.2 per cent and in wheat germ oil in three times this amount. One commercial antioxidant is based on wheat germ oil activated by a trace of organic acid. Another is also a cereal product, oat flour. Two that are products of natural resins are gum guaiac and nor-dihydro-guaiaretic acid (N. D. G. A.). StilI other phenolic types are gallic acid and its esters, especially ethyl and propyl gallate, and one of the first antioxidants discovered, hydroquiuone. Of all these only gum guaiac, tocopherol, and N. D. G. A. have to date been proved by the MeatInspection Division of the War Food Administration for inclusion in meat fats_ Besides the phenolic type, there are certain amines of particular value as rubber antioxidants. Traces of certain sulfur compounds or triphenyl phosphite present in lubricating oils and greases make these products far more resistant to oxidation than highly refined mineral white oils, solvent~ and petroleum jellies. In preserving most vegetable oils, antioxidants generally have to be used in relatively large proport ions (of the order of I per cent), and at best the gain through their use is usually only moderate. Most essential oils also respond bnt moderately to presently available antioxidants. Perhaps the greatest ~POllse is by some perfnme ingredients and by some artificial flavoring materials, such as benzaldehyde (bitter almonds) and cinnamic aldehyde (cinnamon). Usually in a mixture of oils, some will be of antioxidant value and protect the others; it is the pure mattrials that need protection. With animal fats and oils, most of which contain only small amounts of natural protective agents, the response to antioxidants is relatively great, and is industrially significant.-Industria.f Bulletin of A rlltur D. Lillie. Inc.
