Stability of ry Vitamin A Concentrates M. J. BURNS’AND F. W. QUACKENBUSH Purdue University, Lafayette, I n d .
Manufacturers of conimercial feeds and livestock feeders have long been plagued with the problem of vitamin A deterioration between the time of addition of the vitamin and the consumption of the feed. In efforts to solve this problem, a number of suppliers of vitamin A products have recently placed on the market dry vitamin A preparations which are claimed to be stable. The purpose of this investigation was to compare the stability of these products, both as received and when mixed with some of the common ingredients of feeds. All manufacturers willingly supplied samples of their products, but some revealed only general information concerning composition. The results show that all of these dry vitamin A products represent an improvement over vitamin A oils of the past, but that none of the dry products is greatly superior to the others. All lost some of their initial vitamin but retained more than 500/, of it, during 6 months’ storage at room temperature. In most cases mixing with corn and soybean meal improved the stability. These results should provide useful information to feed manufacturers, nutritionists, and feeders.
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HE autoxidation of vitamin A in feeds is of mncern to live-
stock and poultry feeders and to feed manufacturers. Antioxidants and synergists which retard autoxidation have been used with varying degrees of success in stabilizing oils ( 1 , d ) but when the vitamin is mixed with a feed, the problem of preventing autoxidation seems to become more difficult (4,6). During recent years industry has made available a number of commercial brands of dry vitamin A products which are claimed to be stable when mixed with feeds. The purpose of the present study was to determine how effectively vitamin A is stabilized in the different commercial products and t o ascertain if possible what materials are most effective. Seven different products were furnished by manufacturers with the following information regarding composition or method of manufacture. The initial vitamin A content in micrograms per gram is shown in parentheses following the number. No. 1 (1500). This product consists of vitamin, A feeding oil blended with wheat germ oil meal and soybean oil meal. The fat-soluble vitamins are sealed into the carrier by a process involving the use of microcrystalline wax. The latter process and the finished products are the subjects of pending United States and foreign patents. No. 2 (1500). Same as No. 1, except that it contains added vitamin Da. No. 3 (180) A mixture of a number of vitamins in a vegetable carrier Iio. 4 (300). A stabilized fish liver oil in a dry carrier. No. 5 (1500). Vitamins A and D in a cereal carrier which is lipide coated. No. G (1500). A carrier of calcium carbonate and calcium phosphate for a hydrogenated fish liver oil which is stabilized with sorbitol and butylated hydroxyanisole. No. 7 (150). A carotene concentrate which consists of bran, oats, middlings, alfalfa leaf meal, and carrot powder. PREPARATION AND STORAGE OF FEED MIXTURES
Each of the seven commercial products was subjected to a series of four storage experiments as follows: stored R S received 1
without mixing n-ith a carrier; mixed with ground whole yellow corn, with soybean oil meal (expeller), and with glucose (cerelose) each of which was passed through a 20-mesh sieve before use. The h a 1 mixtures contained approximately 10 micrograms per gram of vitamin A alcohol or its equivalent in esters or @-carotene. The concentrates and mixtures were placed in screw-cap bottles and stored in the dark a t room temperature. The vitamin A or carotene content of the concentrates and mixtures was determined a t the time of storage and a t monthly intervals therea,fter for a period of G months. ANALYTICAL PROCEDURES
Carotene Tvas determined by the official Association of Official Agricultural Chemists (A.O.A.C.j method for hays and dried plants ( 3 ) . Vitamin A was determined by extraction with a mixture of acet’oneand hexane, selective adsorption of the extract on a magnesia column, and reaction of the vitamin A ester portion of the eluate with antimony trichloride. The method, with minor alterations, has recently been adopted by the B.0,A.C. and published in detail (6). RESULTS AND DISCUSSION
The results of the stability tests are shown in Table 2 . The most stable products contained a mixture of natural antioxidants, while the least stable (No. 6 ) contained only’ one antioxidant and a synergist. The product which was lipide coated (No. 5 ) evidently was low in antioxidants because it w m one of the best when mixed with soybean oil meal but was the poorest without a carrier.
TABLE I, STABILITY OF COhZXlERCIAL V I T A X I Y A CONCENTRATES STORED I N AIR AT R O O N TE41PERATURE (Percentages of initial vitainin A or carotene remaining at end of during a 6-month period) Time in Months Product NO. Diluent 1 2 3 4 1 None 100 100 83 82 77 80 Corn meal 100 100 Soybean meal 100 100 91 89 Glucose 100 100 93 93 84 83 88 2 None 100 93 90 91 Corn meal 98 89 90 90 Soybean meal 92 78 79 63 Glucose 90 75 75 76 77 3 None 90 87 82 80 Corn meal 87 88 Soybean meal 95 98 27 32 54 47 Glucose 89 81 78 4 \‘one 100 84 96 92 80 Corn meal 90 100 93 91 Soybean meal 47 32 35 Glucose 63 58 60 97 64 5 None 81 86 51 Corn meal 86 84 88 Soybean meal 70 44 48 33 Glucose 50 71 6 None 93 80 48 Corn meal 89 60 85 67 65 Soybean meal 64 38 33 20 Glucose 7 Wone 100 89 72 65 Onrn meal 100 90 83 84 hesn meal 100 93 76 78 100 86 76 61
%
2;
Present address, Alabama Polytechnic Institute, Auburn, Ala.
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each month ~~
3 64 BO 88 65 85 93 88 61
71 8U
86 27 78 76 89 23 65 84 88 38 70 44 57 14 73
6 86 75 81 61 86 84 92 65 74 77 83 35 67 71 85 17 61 72 85 37 67 46
55
16
73
July 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
The effectiveness of corn meal and soybean oil meal as carriers was due evidently to the presence of antioxidants which supplemented those in the concentrates. Soybean oil meal was more effective in preventing autoxidation than corn meal. The greater rapidity in the loss of vitamin A or @-carotenewhen the products were mixed with glucose than when stored alone may be due either t o greater dispersion of the products or to the presence of oxidants in the glucose. The two products that were the most stable alone (Nos. 1 and 2) were also the most stable when mixed with glucose. They retained more than 60% of their initial vitamin A content after 6 months of storage when mixed with glucose as compared with 37% and less for the other products. SUMMARY
Seven different dry commercial vitamin A products containing 150 to 1500 micrograms of vitamin A or carotene per gram retained 60 to 85% of their initial vitaniin during a 6-month storage period in the dark a t room temperature. The highest stability
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was shown by products which employed vegetable meals or the antioxidants which they contain. A portion of each of the products was mixed with corn meal, soybean oil meal, or glucose in such proportions that the mixtures contained approximately 10 micrograms per gram of vitamin A or its equivalent in esters or @-carotene. Soybean oil meal (expeller) improved the stability of the vitamin in most of the products. Ground yellow corn showed a similar effect but t o a lesser degree. Glucose (cerelose) diminished the stability in all cases. LITERATURE CITED
(1) Buxton, L. O., IND.ENG.CHEM.,39,225 (1947). (2) Dassow, J. A,, and Stansby, Maurice E., J . Am. Oil Chemzsls’ SOC.,26, 475 (1949). ( 3 ) J . Assoc. O f i c . A g r . Chemists,31, 111 (1948). (4)Maynard, L. A,, “Animal Nutrition,” revised ed., p. 187, Piew York, McGraw-Hill Publishing Co., 1947. (5) Mitchell, H. L., Schrenk, W. G., and King, H. H., IND. ENG. CHBM.,41, 670 (1949). (6) Schaefer, H. C., J. Assoc. Ofic.Agr. Chemists, 33, 615 (1950). R E C E I V October ~D 4,1960. Paper No. 478 of the Purdue Agricultural Experim e n t Station.
Protein Evaluations of Yeast Grown on Wood Hvdrolvzate J
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ELWIN E. HARRIS, GEORGE J. HAJNY, AND NIARTHA C. JOHNSON Forest Products Laboratory, Madison, Wis.
This project was undertaken to determine the conditions of maximum growth of six strains of fast-growing yeast, using wood hydrolyzate as a source of sugar, and the comparative value of yeasts as a source of protein for animals. All six strains of yeast grew rapidly on the wood hydrolyzate in a continuous propagator, using 90 to 96% of the reducing matter in solution, giving yields of 42 to 58% of yeast with 4S to 51% protein. These six strains of yeast, plus a sample of yeast grown on sulfite waste liquor, were fed in comparison with casein as a source of protein to protein-depleted adult rats. Regain in weight with the eight strains of yeast was less than with casein, but when supplemented with methionine, weight regain with yeast was equal to casein. Wood hydrolyzate may be used as a source of sugar for the production of high yields of yeast that is high in protein. This low-cost yeast, when supplemented with small amounts of methionine, provides a source of protein comparable with animal proteins, thereby bringing about a rapid, low-cost, ef6cient method of converting waste nonedible carbohydrates into an edible complete protein.
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IX strains of yeast previously shown (9)to be readily acclimatized for growth on wood hydrolyzate in batch propagations in shake flasks were grown continuously in a Waldhof-type yeast propagator. Samples of these six yeasts were fed as a source of protein t o rats to determine availability and value as a source of protein. Experimental production of a Torula yeast on wood hydrolyzate (6, 6, 8) has shown that 8 yeast propagator provided with a means for continuous addition of sugar solution and continuous removal of spent solution and yeast, and with a means of controlling foam, has the, best results. A small experimental propa-
gator having these features was constructed (12) and used for preliminary work.
It was determined in this equipment that 5 to 5.5 grams of reducing sugar, as a 5% solution, could be fed continuously per hour per liter of propagator operating capacity. Yeast in a propagator having an operating capacity of 34 liters gave good groFth when fed 3.4 liters per hour of a 5% solution of wood sugar with the necessary nutrients. Later a modification of the first propagator with an operating capacity of 150 liters was built. This employed a squirrel-cage type of ropeller for distributing the air As in the liquid and pumping the %guid t o control foamin much as 20 liters of 5% sugar solution per hour could be fe%fully acclimatized Torula east in this propagator with practically complete utilization of (0th hexose and pentose sugars. Nutrient requirements (6) were found t o be 3.4 pounds of nitrogen as ammonia, ammonium sulfate, or urea, 0.71 pound of phosphorus as sodium phosphate salts, and 0.58 pound of potassium as either potassium chloride or sulfate for each 100 pounds of reducing sugar in the feed. The air requirement was 80 cubic feet for each pound of sugar in the feed, or 2.3 cubic feet per minute when the rate of feed was 16 liters of 5% sugar per hour. Under equilibrium operating conditions the liquid was changed to a free-flowing foam three times the volume of the liquid so the actual li uid in the 150-liter propagator was 50 liters. d e n a feed rate 16 liters an hour was used, the throughput time was 3.12 hours. At a feed rate of 20 liters, the throughput time waa 2.5 hours. Utilization of reducin material was slightly higher when the throughput time was axout 3 hours than it waa with a 2.5-hour period.
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EQUIPMENT
The yeast propagator was a water-jacketed stainless-steel tank with a total capacity of 150 liters. Inside was a draft tube of about one third the diameter of the tank and a rotating air sparger mounted with a top and bottom bearing similar to the small laboratory model previously described ( l a ) . Sugar solution containing the nutrients was fed in by a proportioning pump. The level of the contents of the propagator was controlled by an electronically operated valve in the bottom. Yeast and spent liquor were pumped from the bottom of the propagator to a defoaming tank, from which it was pumped to a continuous yeast
