George Abraham

Modeling the solvent extraction of oilseeds

A computer model and an experimental procedure for generating data needed in the model have been developed for the oilseed extraction process. The experiments are relatively simple and are performed with a bench-top extractor. Experimental results and modeling calculations are presented for the extraction of cottonseed using hexane, isopropanol and ethanol. The calculations show that in an alcohol extraction using a chill separation, isopropanol’s greater oil miscibility allows for a lower solvent-to-feed ratio than does ethanol. Using the latter solvent, however, achieves lower residual lipids in the extracted meal because recycled ethanol contains less oil than recycled isopropanol.

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.

Interesterification selectivity in lipase catalyzed reactions of low molecular weight triglycerides

SummaryIn the absence of an organic solvent, a buffer to enzyme weight ratio of 1 gives maximum selectivity to interesterification over hydrolysis in a lipase-catalyzed mixture of triacetin and tributyrin. Addition of hexane enhances interesterification as does a reversed micelle configuration.

Lipase Catalysis and Its Applications

Lipases have been traditionally defined as enzymes “capable of hydrolyzing esters of oleic acid.”1 The definition of a lipase as a hydrolytic enzyme originated primarily from its physiological function of triglyceride hydrolysis.

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.

CHARACTERISTICS OF LIPASE CATALYSIS DURING ESTER SYNTHESIS IN REVERSED MICELLAR SYSTEMS

The ability of lipase from Candida cylindracea to catalyze ester synthesis from a long chain fatty acid (palmitic acid) and alcohols of varying chain length, is examined. The enzyme is located in the minimal-water environment of reversed micelles. Lipase activity is a strong function of the mode of encapsulation. Direct solid lipase addition to reversed micelles leads to encapsulation in an inactive state unless the enzyme is contacted with the acyl substrate. The alcohol inhibits activity, with low molecular weight alcohols tending to denature the enzyme. Implications to reversed micelle based biocatalyst preparation are briefly discussed.

Utilizing ethanol to produce stabilized brown rice products

Oil in brown rice is susceptible to hydrolytic and oxidative deterioration, which can lead to off-odors, off-flavors, and shortened shelf life. This paper discusses lipolytic hydrolysis and oxidation of kernel oil and methods for stabilizing the oil. An overview of processes in which ethanol is used in liquid and vapor states to stabilize brown rice to lipolytic hydrolysis is presented.

The potential commercial aspects of gossypol

Gossypol, a yellow polyphenolic pigment contained in all plant parts of the predominant cotton cultivars, has been the source of practical as well as scientific interest for over a century. Recent changes in both cotton fiber and cottonseed products markets have focused renewed interest on potential alternate uses for fiber and seed and other products of cotton and for the gossypol contained in the seed. A review of the literature dealing with the potential commercial use of gossypol from 1886, when it was first isolated, until the present, is presented.

Process engineering economic evaluation of the ethanol extraction of cottonseed: Preliminary analysis

This preliminary analysis was undertaken to determine if the operations being developed for the aqueous ethanol extraction of cottonseed oil are economical and whether further research of this process should be pursued. Results of the conversion of hypothetical hexane extraction plants to ethanol extraction, in the plant capacity range of 300-600 tons of cottonseed flakes/day and operating 150-350 days annually, show that two unconventional operations, namely, chill-separation of miscella exiting the extractor and reduction of oil in recycled ethanol by reverse osmosis, require less energy and are less expensive than conventional alternatives. However, additional work is needed to determine the overall efficiency of an alcohol process as compared to a conventional hexane process.

Adsorptive gossypol removal

Gossypol is extractable from cottonseed by using aqueous ethanol. The equilibrium between undissolved gossypol in cottonseed and that dissolved in the solvent determines the residual gossypol. To move the equilibrium toward extraction from the seeds, the dissolved gossypol needs to be removed from the gossypol-solvent-oil mixture. Gossypol removal from the mixture by adsorption on alumina, silica and molecular sieve 5Å was tested. Experimental results indicated that gossypol was more selectively adsorbed than triglycerides by these adsorbents. Alumina and silica had higher gossypol adsorption capacities than molecular sieve 5Å.