Effect of Moisture and of Treatments With Acid and Alkali on Rate of Formation of Free Fatty Acids in Stored Cottonseed

Abstract

IntroductionCottoniseed deteriorates upon1 storage, with the result that the contenit of free fattv acids in the seed oil is increased, the color of the oil in the seed is darkened, the seed protein is partially denatured, and viability is decreased. This increase in free fatty acid conitent is reflected in a higher refining loss during the processing of the crude oil and the darkened color of the oil reduces its desirability as ani edible product. AIALOWAN (7,8), FREYER (3), anid ROBERTSON anid CAMPBELL (14) have investi(gated the effects of methods of storage, moisture content, and temperature of the seed on the formationi of free fattv acids during the storaoe of cottonlseed. SIMPSON (16,17) has made a thorough study of the effect of storage coniditions on the viability-of cottonseed, and RUSCA and GERDES (15) have observed the effect of the drying of cotton prior to ginning uponi the subsequeint storage behavior of the seeds. All of these invest.igators have concluded that, with iniereasino moisture content of the seed and higrher temperature of storage, there is a greater tendency-for the formation of free fatty acids in the seeds and a corresponding loss in t.heir viability.It has become evidenit, however, both from studies of the behavior of individual lots of seed and from a statistical study of the cottoinseed in the Delta reoion (9), that moisture content an(d temperature are niot the only factors influencing the quality of stored seed. This meanis that two samples of cottonseed which have the same moisture contenit anid whieh are stored at the same temperature will not necessarily develop free fatty acids at the same rate.The presenit report covers the results of the first of a series of investi- PLANT PHYSIOLOGY meats was thoroughly homogenized in 10 ml. of distilled water by the use of a glass homogenizer (12). The pH was determined as sooni as the homlogenization was completed; otherwise inconsistent and generally lower results were obtained. A glass electrode wi-as used for all pH measurements.The determinations of free fatty acids were made on the oil which had been extracted with Skellysolve F (boiling range, 30°to 600 C.) from the iueats prepared as described above. Three ml. of oil, freed from solvent, were transferred by use of a calibrated pipette ilnto 50 ml. of hot. neutralized ethyl alcohol and were titrated with 0.05 N sodium hydroxide solutioln, usingy thymol blue as the indicator. Whenever an oil with a very high content of free fatty acids was titrated, a stronger alkali solution (0.5 N) was used. In order to provide for proper stirring and heating of the emulsion of alcohol and oil dcuring the titration, the assembly shown in figure 1 was used. The stirring, was accomplished by an air-driven stirrer operating in one arm of the cell, and heat was applied by means of a chromel resistance wvire wound around the bottom bend. A potential of 20 volts applied to three feet of no. 25 chromel wire provided sufficient heating.It is possible to estimate the content of free fatty acids in cotto...

Fat Utilization and Composition in Germinating Cotton Seeds.

“…7. When seedlings were allowed to develop in the dark in temperatures ranging from 210 to 390 C, there was no alteration in the pattern of fat utilization found at 300 C. 8. Under all germination conditions tested, the fat composition was the same function of the total amount of fatty acids remaining in the fat reserve; it was independent of the rate or type of seedling development.…”

“…Evidence, however, for an initially low lipase activity appears in the literature. Karon and Altschul (8) suggested that the autocatalytic reaction which they found typical of free fatty acid formation in moist cotton seeds might be dependent on an increase in lipase aetivitv with time. Olcott and Fontaine (14) could not detect lipase in dormant cotton seeds, but in another study they (15) showed that during germination the activity of this enzyme increased to a maximum.…”

Effect of Inhibitors on the Respiration and Storage of Cottonseed

“…Two of the preselnt authors have reported previously (13) that ammonia and hydrochloric acid vapors inhibit lipolysis of the oil in cottonseed. Subsequent experiments indicated that ammonia treatment also effects the speetruin of extracted cottonseed oil and the heating of seed stored in bulk (1).…”

Respiration of Cottonseed

“…It is not possible, then, on the basis of moisture content alone, to predict respiration intensity. Similarly, it has been previously shown (8) that it is impossible to predict the rate of free fatty acid production in cottonseed on the basis of moisture content alone. 4.…”

“…Whenever it was necessary to change the moisture content artificially either above or below its original value, care was taken to so condition the seeds to the desired moisture content that any resulting biochemical activity would be minimized and permanent injury to the seeds would be prevented. Conditioning was accomplished in this manner by carrying out all moisture changes in a cold room, as previously described (8). Each 3-pound lot of seeds was then stored in air-tight jars at 250 C.…”