P. J. Wan

Temperature effects on the determination of oxidative stability with the metrohm rancimat

Reproducibility of Oil Stability Index (OSI) values determined on the Metrohm Rancimat was measured with a single run and between experimental runs. Within a single experiment, a range of 0.13 h and a standard deviation of 0.066 h were determined. For multiple experiments, standard deviations of 0.24 and 0.26 were obtained for soybean and low-erucic rapeseed oil, respectively. The effect of temperature was determined for safflower, soybean, lowerucic rapeseed, corn, peanut and olive oils. A linear relationship was established between log (OSI) and temperature. The linear equation obtained for soybean oil was utilized to calculate variability of the OSI due to temperature differences in the heating block.

Ethanol extraction of oil, gossypol and aflatoxin from cottonseed

Commercial processing of cottonseed requires hexane to extract and recover edible oil. Gossypol and aflatoxin are not removed from extracted meals. A bench-top extraction process with 95% (vol/vol) aqueous ethanol (EtOH) solvent has been developed that extracts all three of the above materials with a much less volatile solvent. In this process, cottonseed is pretreated and extracted with ambient 95% EtOH to remove gossypol and then extracted with hot 95% EtOH to extract oil and aflatoxin. Membranes and adsorption columns are used to purify the various extract streams, so that they can be recycled directly. A representative extracted meal contained a total gossypol content of 0.47% (a 70% reduction) and 3 ppb aflatoxin (a 95% reduction). Residual oil content was approximately 2%. Although the process is technically feasible, it is presently not economical unless a mill has a continual, serious aflatoxin contamination problem. However, if a plant cannot meet the hexane emission standards under the Clean Air Act of 1990, this process could provide a safer solvent that may expand the use and increase the value of cottonseed meal as a feed for nonruminants.

Water accumulation in the alcohol extraction of cottonseed

The critical moisture content of cottonseed flakes extracted with an aqueous alcohol solvent can be defined as that flake moisture level at which the flakes lose no moisture during extraction. This study shows that the critical moisture content for aqueous ethanol (92%, w/w) is 3%. For aqueous isopropanol (88%, w/w) this value is 6%. If the moisture contents of the flakes are above these levels, then the solvents pick up moisture. For moisture contents below this level, the flakes adsorb moisture and actually dry the alcohol. It is proposed that this latter capability can be used as a basis for a method to control water accumulation in aqueous alcohol solvent extractions.

Ethanol vapor deactivation of gossypol in cottonseed meal

Most cottonseed cultivars contain gossypol, a polyphenolic antinutritional compound. “Free” gossypol is a physiologically active form of gossypol, which is toxic to young- and nonruminant animals. To utilize solvent-extracted cottonseed meal as a general feed, gossypol must be either removed or deactivated to a minimum level specified for each class of animal. Normally, deactivation is carried out prior to oil extraction; however, the desired level of deactivation is not always attained. A new supplemental method of deactivation has been found by using either ethanol or isopropanol vapors on solventextracted meal. In a bench-top set-up, ethanol vapor reduced free gossypol from 0.115 to 0.053%, and a further reduction to 0.026% has been observed with the addition of ferrous sulfate. The supplemental deactivation method can, in most cases, reduce free gossypol to significantly safer levels for feeding, thus increasing utility, and possibly demand, for cottonseed meal as a general animal feed protein source.

Behavior of diglycerides and conjugated fatty acid triglycerides in reverse-phase chromatography

The behavior of conjugated fatty acid triglycerides and diglycerides on reverse-phase chromatography was studied. Trieleostearin is a geometric isomer of trilinolenin. The conjugated double bond arrangement in trieleostearin enhances its hydrophobic interaction with the stationary phase and causes it to be eluted later than trilinolenin. In separation of “critical pairs” of tri- and diglycerides, diglycerides elute later than triglycerides due to the longer fatty acid constituent. Position isomers of 1,2- and 1,3-diglycerides can be separated by reverse-phase high-performance liquid chromatography.

Quick method for estimating free gossypol in cottonseed, meats, collets, and extracted meals

A method for estimating free gossypol (FG) has been developed that decreases sample-determination time from over 2 h to about 25 min per sample. With auto pipetters and bottle-to dispensers, six sample determinations can be completed in approximately 50 min. The method consisted of adding water and acetone separately to a fixed sample weight, mixing, filtering, diluting with 65% acetone, and reading absorbance on a spectrophotometer. Absorbance was plotted against the official American Oil Chemists’ Society’s FG method for samples that contained FG between 0.02 and 0.9%. Quadratic least squares regression for 31 samples had a correlation coefficient ofr2=0.986 and a standard error of estimated FG of 0.032%.

Microwave heating of cottonseed: A pilot plant study

Two cottonseed samples (50 kg) were exposed to microwaves at 45 KW and 2450 MHz for 4 min in an air temperature of 94°C. The final temperature of the seed was 76°C, and the treatment caused a 20% reduction in seed moisture. Examination of the seed immediately after microwave heating (MWH) indicated no differences in the total or soluble protein content of the meal or the content, quality or color of the oil as compared with unheated seed. There was some reduction in the quality of the oil from unheated seed during storage, but only minimal reduction in the quality of the oil from the MWH samples. Protein quality deteriorated in all samples; however, the deterioration was reduced in the microwave-heated seed.