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    Oil and Oilseed Processing II

    A guide to oil extraction.

    Oil and Oilseed Processing II

    Published Jul. 2016|Id: FAPC-159

    By Nurhan Dunford Print-friendly PDF Share Fact Sheet

    JUMP TO:Oil Extraction Techniques Solvent Extraction  Meal and Oil Desolventizing Mechanical Oil Extraction Aqueous Extraction Supercritical Fluid Technology

    Oil Extraction Techniques

    Oilseed processing and oil extraction processes are designed to obtain high quality oil with minimal undesirable components, achieve high extraction yields and produce high value meal. There are several techniques for extracting oil from oilseeds. Two common oilseed extraction processes are solvent extraction and mechanical extraction using a screw press. Today in the United States, mechanical oil expression is not widely used due to low oil recovery. However, the use of screw press is preferred by small processors because of its low capital cost. Solvent extraction with hexane is the standard practice in today’s modern oilseed-processing facilities. Solvent-extraction plant capacities range from 100 to 9000 metric tons per day. Supercritical fluid, water and enzyme-aided water extraction processes are of interest for specialty and gourmet oils production.

    Solvent Extraction 

    Solvent extraction refers to preferential dissolution of oil by contacting oilseeds with a liquid solvent. This is the most efficient technique to recover oil from oilseeds. The efficiency depends on the oilseed preparation prior to extraction, temperature, mode of operation (batch vs. continuous and co-current vs. counter current operations) and equipment design. It is expected that residual oil in the meal to be less than 1 percent after commercial solvent extraction.

    The choice of solvent type is based on solubility of oil in the selected solvent, cost and safety. Light paraffinic petroleum fractions, pentane (boiling point 88-97°F), hexane (boiling point 146-156°F), heptanes (boiling point 194-210°F) and octane (boiling point 215-264°C) can be used for oil extraction. Currently hexane is widely used for commodity vegetable oil extraction. The major disadvantage of these solvents is their flammability. Strict precautions have to be taken to avoid fires and minimize explosion risk in the extraction plants. The 1990 Clean Air Act listed hexane as a hazardous air pollutant. The oilseed processing industry is under pressure to switch to solvents that are considered benign such as alcohol or water. Low oil solubility and higher energy requirement for solvent recovery and meal drying are major disadvantages for using alcohols and water for oil extraction. Furthermore, alcohols lower functionality of soybean proteins.

    Oil solubility in solvent increases with extraction temperature. High temperature also has a positive effect on viscosity and diffusivity of oil. Viscosity decreases while diffusivity increases as the extraction temperature increases, resulting in shorter extraction times. Energy required for solvent recovery decreases when higher operating temperature is used for extraction. However, high temperatures may cause deterioration and denaturation of some oil and meal components. Hence, temperature selection is based on type of oil and required specifications of the final product. There are three major steps in traditional solvent extraction (Figure 1): oil extraction, meal and oil desolventizing, and meal toasting.

    Figure 1: Simplified flow diagram of a hexane extraction process

    In the 1800s, small batch type oil extraction systems were common in Europe. The same vessel was used for both extraction and meal desolventizing. Today, extraction of specialty and high value oils and recovery of oil from spent bleaching clay are carried out in batch extractors. A rotating drum and a vertical cylindrical kettle equipped with a vapor tight cover and a low speed agitator are two popular batch type extractor designs.

    Use of large-scale continuous processes began in the early 1920s. Today, immersion and percolation type continuous extractors are used for commercial solvent extraction of oilseeds. In immersion-type extractors, flaked oilseeds are completely submerged in solvent. For such a system to be efficient, particle size should be as small as possible to achieve maximum contact between seed and solvent. The main disadvantage of this design is that solid and miscella (oil + solvent mixture) separation is difficult. Thus, immersion-type extractors are suitable for small-scale production facilities.

    In percolation-type extractors, flaked seeds are formed into a fixed bed over which solvent is sprayed. Solvent drains through the bed and washes oil out. The particle size of the seeds needs to be large enough to allow a good solvent flow rate through the seed bed. Fine particles in the bed block the solvent flow causing flooding of the bed and, consequently, lowering extraction efficiency. Early designs based on percolation were basket-type extractors in which flaked seeds were placed in baskets with perforated bottoms. These systems look like an enclosed bucket elevator. The baskets are supported by endless chains in a sealed housing and continuously raised and lowered at a slow rate (1 revolution per hour). Each basket is filled with flaked seeds by an automatic feed hopper at the top. As the basket starts descending, solvent is sprayed over the baskets. The spent flakes in baskets ascend to the top of the housing on the opposite side of the feed hopper. At the top, baskets are automatically inverted and spent seeds are discharged into a hopper from which they are transferred to a meal desolventizer on a conveyor belt. Basket-type extractors are bulky and hard to maintain. The newer extractor designs are horizontal and rotary type. The design principle for horizontal extractors is similar to the basket-type extractors, but the baskets rotate in a single horizontal plane rather than vertically. A popular rotary-type design, Rotocel® Extractor, holds the flaked seeds in cells, which rotate in a horizontal plane around a vertical axis. The extractor has four countercurrent extraction stages. The latest rotary extractor design, Reflex®, has a fixed slotted floor and bevel gear drive. A Reflex® extractor, which has a capacity of 9000 metric tons of soybeans per day, is currently in operation in Argentina. Information on various solvent extractor designs can be found on the following web site:

    स्रोत : extension.okstate.edu

    Oil Extraction

    Oil Extraction

    Oil extraction is defined as the process of separating triglyceride (TAG) lipids from the harvested and concentrated algal biomass and it could be done through a variety of mechanical or chemical manipulation techniques.

    From: Life-Cycle Assessment of Biorefineries, 2017

    Related terms:

    BiofuelBiodiesel ProductionMicroalgaeBiodieselTransesterificationBiomassSolvent ExtractionFeedstocksHexaneExtraction Process

    View all Topics

    Advances in bio-oil extraction from nonedible oil seeds and algal biomass

    G. Baskar, ... I. Abarnaebenezer Selvakumari, in Advances in Eco-Fuels for a Sustainable Environment, 2019

    7.4 Extraction techniques

    There are three main techniques that are available for the extraction of oil from a seed or kernel: mechanical, chemical, or enzymatic. Apart from these widely used methods, there are some other methods that are available that have been designed specifically for some sample types: accelerated solvent extraction (ASE), SFE, or microwave-assisted extraction (MAE) [30].

    7.4.1 Mechanical extraction

    Oil extraction by mechanical expellers or presses is the most conventional method. In this method, either a manual ram press or an engine-driven screw press is used for the extraction of oil. It has been observed that the ram press can extract around 60%–65% of oil while an engine-driven screw press can extract around 68%–80% of the available oil from seeds [30].

    The design of the mechanical press is very important as it plays a crucial role in the yield of oil. The yield can be increased by the pretreatment of the seeds by a cooking process to around 89% in single pass and 91% in a dual pass [32] (Achten, 2008). Oil extracted from a mechanical press needs further treatment by filtering and degumming [30].

    7.4.2 Chemical or solvent extraction

    Solvent extraction is the process of removal of a solute component from the solid by using a liquid solvent; it is called leaching or solid-liquid extraction. According to this method, n-hexane yields the higher amount of oil compared to other solvents [28]. There are various factors such as particle size, solvent type, and temperature that were found to affect the extraction of oil [30]. The small particle size is preferred as it allows for a large interfacial area between the solid and liquid. The solubility of the material increases with an increase in temperature. Agitation of the solvent increases the eddy diffusion and therefore increases the transfer of materals from the surface to the particles [4, 33]. It is observed that low viscosity solvents are preferred to circulate freely during extraction. The chemical oil extraction technique was found to be very effective because of high oil yield and consistent performance. In addition, this method has a negative environmental impact because of the wastewater generation, higher specific energy consumption, and higher emission of volatile organic compounds as well as fewer human health impacts [30]. There are three methods of extraction of this type:

    i.

    Hot water extraction.

    ii. Soxhlet extraction. iii.

    Ultrasonication technique.

    7.4.3 Accelerated solvent extraction

    ASE is also called pressurized solvent extraction (PSE), this is one of the modern extraction processes. According to this method, the oil from seeds is extracted by using organic or aqueous solvents at elevated temperatures and pressures. It was observed that elevated pressure prevents boiling at temperatures above the normal boiling point of solvent but high temperature accelerates the extraction rate of oil. This method has reduced time as well as solvent consumption when compared to the other solvent extraction techniques [40]. ASE has been used for the extraction of different materials, including wheat germ [34] and flaxseed hulls.

    7.4.4 Enzymatic extraction

    The aqueous enzymatic oil extraction (AEOE) method is an endowed technique for the extraction of oil from plant materials [35]. The main advantages of this processis are its environmentally friendly nature and the fact that it does not produce any harmful or volatile organic compounds [36]. Suitable enzymes are used to extract the oil from pretreated seeds. A combination of enzymatic extraction with ultrasonication has shown better results in oil extraction from seeds. Yet the problems associated with solvent extraction can be potentially reduced by using the aqueous enzymatic oil extraction technique. This process of extraction of oil is observed to be more time consuming, which is its main disadvantage [37].

    7.4.5 Supercritical fluid extraction

    The extraction of oil from seeds using various solvent extraction technique has been found to be more time consuming and problem in solvent disposal. Therefore, the problem of solvent use as well as time consumption, often in large quantities and toxicity, SFE technique has been developed. The method has been in practice since the 1980s to avoid the use of organic solvents as well as to increase the speed of extraction [38]. SFE using CO2 has been found to have advantages over solvent extraction [39, 40]. However, the main constraint of the SFE is its high cost at the production scale. This is not only due to the usage of high pressure equipment but also because of the raw material used, which should be freeze-dried to reduce its moisture.

    7.4.6 Microwave-assisted extraction

    स्रोत : www.sciencedirect.com

    Processes

    Most seed oils are edible while some are used generally as raw material for soap production, chocolate, margarine, and recently in biodiesel formulations as potential candidates capable of replacing fossil fuels which are costly and destructive to the environment. Oilseeds are a green and major reservoir which when properly exploited can be used sustainably for the production of chemicals at both the laboratory and industrial scales. Oil extraction is one of the most critical steps in seed oil processing because it determines the quality and quantity of oil extracted. Optimization of the extraction conditions for each extraction method enhances yield and quality meanwhile a carefully chosen optimization process equally has the potential of saving time and heat requirements with an associated consequence on cost reduction of the entire process. In this review, the techniques used to optimize oil extraction from plant materials which can be consulted by stakeholders in the field are brought to focus and the merits and demerits of these methods highlighted. Additionally, different types of optimization techniques used for various processes including modeling and the software employed in the optimization processes are discussed. Finally, the quality of the oil as affected by the methods of extraction and the optimization process used are also presented.

    Open AccessFeature PaperReview

    Optimization Methods for the Extraction of Vegetable Oils: A Review

    by Divine Bup Nde * andAnuanwen Claris Foncha

    Department of Nutrition, Food and Bio-Resource Technology, College of Technology, University of Bamenda, P.O. Box 39 Bamenda, Cameroon

    *

    Author to whom correspondence should be addressed.

    Processes 2020, 8(2), 209; https://doi.org/10.3390/pr8020209

    Received: 25 December 2019 / Revised: 27 January 2020 / Accepted: 30 January 2020 / Published: 8 February 2020

    (This article belongs to the Special Issue Feature Review Papers)

    Download Versions Notes

    Abstract

    Most seed oils are edible while some are used generally as raw material for soap production, chocolate, margarine, and recently in biodiesel formulations as potential candidates capable of replacing fossil fuels which are costly and destructive to the environment. Oilseeds are a green and major reservoir which when properly exploited can be used sustainably for the production of chemicals at both the laboratory and industrial scales. Oil extraction is one of the most critical steps in seed oil processing because it determines the quality and quantity of oil extracted. Optimization of the extraction conditions for each extraction method enhances yield and quality meanwhile a carefully chosen optimization process equally has the potential of saving time and heat requirements with an associated consequence on cost reduction of the entire process. In this review, the techniques used to optimize oil extraction from plant materials which can be consulted by stakeholders in the field are brought to focus and the merits and demerits of these methods highlighted. Additionally, different types of optimization techniques used for various processes including modeling and the software employed in the optimization processes are discussed. Finally, the quality of the oil as affected by the methods of extraction and the optimization process used are also presented.

    Keywords:

    oilseeds; oil extraction; experimental designs and optimization; polynomial modelling; optimization software

    1. Introduction

    Many plants contain extractible oils that have for centuries been used either as food or in cosmetic formulations [1]. Recently some of these plant bearing oils have caught the attention of researchers as a source of renewable energy especially in bio-diesel fuel production [2,3]. Oil content of oleaginous seeds, nut, kernel, or fruit pulps varies between 3% and 70% of the total weight and has similar chemical structures to animal fats [4]. The benefits that accrue from oilseed processing and sales to individual or grouped farmers, companies, and even to national economies cannot be overemphasized because two of its major products oils and meal or cake are both of great commercial value. For example, in developing countries such as Malaysia, Cameroon, and Ivory Coast there are considerable sections of the population that source their livelihoods principally from palm oil processing and sale. Statistics show that global production of vegetable oil has steadily increased from about 90.5 million metric tons in 2000/2001 to 207.5 million metric tons in 2019/2020 and these trends are expected to continue in the future [5]. Major plant oil sources of commercial importance out of the 40 documented ones that contain edible oils include soybean, sunflower, groundnuts, rapeseed, coconut, and oil palm [6]. Other oilseeds of less commercial importance which are however highly cherished because of the important roles they play in one or more of the following processes; soap production, chocolate, margarine, and biodiesel production etc. include castor, safflower, shea, neem, and tung oils etc. Amongst the many unit operations involved in the processing of oils from oilseeds, extraction remains one of the most critical steps because it determines the quality and quantity of the oil extracted. Initial oil content is a major factor that determines the choice of grain processing and extraction methods for the various oil seeds [7].

    Although extraction methods especially for the more conventional oilseeds are known, there has been a continuous quest by researchers to improve extraction yields. One proper way of improving extraction yields is to optimize the extraction conditions for each type of extraction method and oilseed because optimum yield will vary with these factors. Apart from enhancing yields and quality, a carefully chosen optimization process equally has the potential of saving time and heat requirements with an associated consequence on reducing the cost of the entire oil extraction process. A number of optimization methods for the extraction of useful components from plant material have been documented in the literature [1,3,6]. While many researchers have embraced the investigation of nonconventional oils obviously for the multipurpose uses of the oil, there has not been a corresponding effort in documenting published results on oilseeds in the form of reviews that could be available to stake holders for consultation at all times. The few reviews on this subject have lightly discussed the methods of extraction without laying emphasis on types of oilseeds, optimization methods of the extraction processes, modelling, as well as the influence of the extraction and optimization methods on the quality of the extracted oil [8,9,10]. Consequently, to the best of our knowledge, there is no comprehensive review on the various techniques used for optimizing oil extraction from plant material. This work therefore presents a review on techniques used to optimize oil extraction from plant material which can be consulted by stakeholders in the field. The work summarizes the general methods of oil extraction from oilseeds, followed by the different types of optimizations techniques used for the various extraction processes including modelling and the software used in the optimization process. The last section of the work is centered on the oil quality as affected by the extraction methods and the optimization process used.

    स्रोत : www.mdpi.com

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