Membrane technology for the processing of fruit juices and beverages has been applied mainly for clarification using ultrafiltration and microfiltration, and for concentration using reverse osmosis. The effects of product preparation, membrane selection, and operating parameters are important factors influencing filtration rate and product quality. Technological advances related to the development of new membranes, improvement in process engineering, and better understanding of fruit beverage constituents have expanded the range of membrane separation processes. Developments in novel membrane processes, including electrodialysis and pervaporation, increased the array of applications in combination with other technologies for alternate uses in fruit juices and beverages.
Commercial sources of edible oils and fats include oil‐seeds, fruit pulps, animals and fish. Oilseeds processing typically consists of the following steps: i) seed preparation; ii) solvent extraction of flakes and/or extruded collets; iii) desolventization of the meal;iv) recovery of solvent by distillation; and v) degumming, refining, bleaching, and deodorizing of the crude oil. The process consumes large amounts of energy—in the forms of electricity, natural gas and fuel oils—to heat and cool the oil between individual processing steps and to generate high vacuum. Steam requirements for producing edible oil from crude oil range from 2000 to 4000 Btu/lb depending on the type of oil processed. The processing of cottonseed, corn, peanut and soybean oils alone consumes approximately 64.7 trillion Btu/yr of energy in the United States (based on 15.1×109 Ib crude oil processed). Electricity requirements for a typical refinery are between 120,000 kWh and 160,000kWh/yr (based on 1400 to 1800 kWh/22,000 Ib crude oil processed/hr). Current membrane separation research, as applied to miscella distillation; vapor recovery; condensate return; wastewater treatment; degumming, refining, and bleaching; hydrogenation catalyst recovery; oilseed proteins; and nitrogen production, is reviewed in this paper. The greatest potential for energy savings of 15 to 21 trillion Btu/yr exists in replacing or supplementing conventional degumming, refining, and bleaching processes. Decreased oil losses and decreased bleaching earth requirements are other potential advantages of membrane processing. Approximately 2 trillion Btu/yr could be saved using a hybrid membrane system to recover solvents in extraction of crude oils. Although marginal success has been reported to date, the development of hexane‐resistant membranes may make this application viable.
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. ...
Isopropyl alcohol (IPA) is one of the most favorable alternatives to hexane for oil extraction. Compared to hexane and other solvents such as ethanol, IPA is less flammable and less toxic and is free of restrictive governmental regulations. Thus, the effects of collets versus flake with hexane and IPA as extraction solvents at various alcohol concentrations (88, 93, 95 and 97% IPA levels) were examined. Cottonseed meats were flaked and cooked before they were processed using a Hivex expander. The solvent extractions were carried out using a seven‐stage countercurrent laboratory extraction unit. Extractability of collets with 95% IPA was better than that of flakes. The residual oil content and solvent hold‐up of the collets were 1.6 and 33.0% compared 4.5; and 53.2% for the flakes, respectively. The aqueous IPA extraction proceeded more slowly and showed a lower oil carrying capacity than that of hexane. The residual oil content of the cottonseed collets extracted with hexane was 1.2% while the solvents containing 97, 93, and 88% IPA resulted in 1.5, 1.9, and 2.4%, respectively. Reduction in water content improved the extraction efficiency of IPA.
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