The recovery of solvents used in the extraction step of edible oil processing is required for economical, environmental, and safety considerations. The miscella {mixture of extracted oil and solvent) exits the extractor at 70 to 75 wt% solvent content. Currently, the solvent is recovered by distillation. This paper reports the results of a study on separation of vegetable oils from commercial extraction solvents using various types of Reverse Osmosis {RO) and Ultrafiltration (UF} membranes.Solvent permeation rates and separation performances of various RO and UF membranes were determined by using ethanol, isopropyl alcohol and hexane as the solvents. One membrane exhibited a flux of 200 GFD (ethanol) with 1% oil remaining in the permeate. However, hexane rapidly deteriorated all but one of the membranes tested. The membrane that was compatible with hexane had a low flux and unacceptably low oil retention.Industrial-scale membranes were also evaluated in pilot plant trials. A hexane separation was attempted with a hollow-fiber membrane unit, and it was noted that the pores of the fibers swelled almost closed. Some of the commercially available membranes selectively removed solvent {ethanol or isopropanol) from the edible oil miscellas with reasonable flow rates.The research reported has shown that membranes manufactured from polyamide were the least affected by hexane. Fluxes achieved during solvent-oil separations were increased by increases in either temperature or pressure and decreased by increases in oil concentration in the feed. The processing temperature affected the percentage of oil in solution in either ethanol or isopropanol as well as the viscosity of the feed. Both of these factors in turn influenced the flux achieved.Approximately 2 trillion Btu/yr could be saved using a hybrid membrane system to recover solvents used in the extraction step of crude oil production. Studies to date report marginal success. The development of hexane-resistant membranes may make this application viable.Edible oil processing. The primary solvent for extracting crude oil from oilseed flakes, expanded coUets or presscake is commercial "hexane," a mixture of aliphatic and cyclic hydrocarbons collected over a narrow range of distillation temperatures. "Miscella" from extractors contains 25-30% oil and is typically separated by distillation to reclaim the hexane for reuse (1). Figure 1 illustrates the details of miscella distillation and a solvent recovery system (2). Miscella is *To whom correspondence should be addressed. pumped from the miscella tank into the evaporator, where a majority of the solvent is removed at this stage, and concentrated miscella (90% or more oil) next flows into the vacuum stripper. Hexane content of the oil is brought to less then 1% by high vacuum at the top of the stripper. The remaining solvent then is stripped by countercurrent live steam during its movement through a series of trays. The solvent and steam are condensed in the oil stripper condenser and the mixture is separated by decanting. ...
SUMMARY— Glandless cottonseed meals were prepared under controlled conditions in a pilot plant by three different processing methods. These meals along with a glandless cottonseed meal produced at a commercial oil mill were used as source meals for protein isolates. Two protein fractions differing in composition and characteristics were isolated from each type meal using a two‐step, two‐solvent isolation procedure developed at the USDA Southern Utilization R & D Div. yields of each isolate precipitated at three different pH levels were determined on the pilot plant meals. Isolate yields from the commercial meal were determined near the respective isoelectric points of the two fractions. Functional properties including whippability, heat gelation, solubility and foaming properties, were measured on all isolates. Variation in measured values due to meal processing method and precipitation pH was statistically assessed in some instances. Meal processing method was found to significantly affect the yield of Isolate I, the minor isolate. pH of precipitation was found to significantly affect the yield of Isolate II, the major isolate. Also, it was shown that the pH‐solubility profiles of both Isolates I and II could be altered by changing the pH at which they were precipitated. The functional properties of isolates from meals processed without heat were superior to those of isolates from heated meals. Data collected indicated the need for a new practice in evaluating the extent of denaturation of cottonseed protein products. The present practice of determining nitrogen solubility at one point was shown to be inadequate.
AND SUMMARYSixteen new o~r experimental varieties of cottonseed, eight glandless and eight glanded, were extensively analyzed in this study. Ginned seed from each were studied and then kernel samples and finally oil and flour samples prepared from the kernels. Mean values determined for each attribute measured are presented for each type seed. These data are useful for (a) showing the magnitude of particular desirable properties presently being achieved in varieties of each type seed, (b) showing something of the variation of these properties among varieties within seed types, and (c) comparing glandless and glanded seed types for compositional differences.
The production of food ingredients from undefatted soybeans by aqueous processing and isolation of protein from soy flour by ultrafiltration membranes has been demonstrated adequately during the past decade. These relatively new techniques offer significant advantages over conventional soy processing methods. Aqueous processing requires no petroleum-based solvent and consequently provides increased safety and flexibility of operation (because start-up and shutdown are safe and easy). It also provides opportunities for removal or deactivation of undesirable constituents of raw materials with appropriate water-soluble chemicals. It is, however, less efficient in oil extraction, and demulsification is required to recover clear oil when emulsions form. Ultrafiltration processes recover protein directly from soy flour extracts and thereby avoid generation of the whey which results from the conventional isoelectric precipitation. These processes have the advantages of increased isolate yield (as whey proteins are recovered in the isolate), and produce products having enhanced functionality and nitrogen solubility. The two processing techniques have subsequently been combined to obtain a single procedure with the advantages of each. Extracts from undefatted soybeans have been membrane processed with and without separating the oil to produce a variety of new soy protein ingredients.
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