Optimization of industrial‐scale deodorization of high‐oleic sunflower oil via response surface methodology

Optimization of industrial‐scale deodorization of high‐oleic sunflower oil (HOSO) via response surface methodology is presented in this study. The results of an experimental program conducted on an industrial‐scale deodorizer were analyzed statistically. Predictive models were derived for each of the oil quality indicators (QI) in dependence on the studied variable deodorization process parameters. The deodorization behavior of some minor components was analyzed on a pilot‐scale deodorizer. For comparison, a similar experimental program was also performed on the laboratory‐scale. The results of this study demonstrate that optimization of the deodorization process requires a suitable compromise between often mutually opposing demands dictated by different oil QI. The production of HOSO with top‐quality organoleptic and nutritional values (high tocopherol and phytosterol contents and low free and trans fatty acid contents) and high oxidative stability demands deodorization temperatures in the range between 220 and 235 °C and a total sparge steam above 2.0% (wt/wt in oil). The response surface methodology provides the tools needed to identify the optimum deodorization process conditions. However, the laboratory‐scale experiments, while showing similar response characteristics of QI in dependence on the process parameters and thus helpful as a guide, are of limited value in the optimization of an industrial‐scale operation.     

Thermooxidative stability of vegetable oils refined by steam vacuum distillation and by molecular distillation

Semi‐refined rapeseed and sunflower oils after degumming and bleaching were refined by deodorization and deacidification in two ways, i.e., by steam vacuum distillation in the deodorization column Lurgi and by molecular distillation in the wiped‐film evaporator. The oxidative stability of the oils before and after the physical refining has been evaluated using non‐isothermal differential scanning calorimetry. Treatment of the experimental data was carried out by applying a new method based on a non‐Arrhenian temperature function. The results reveal that refining by molecular distillation leads to lower oxidative stability of the oils than refining by steam vacuum distillation. Practical applications : (i) A method for the refining of edible oils by the molecular distillation in the wiped film of a short‐path evaporator is presented and applied. (ii) Oxidative stability of the oils refined by molecular distillation and steam vacuum distillation is compared. It has been found that refining by molecular distillation leads to lower oxidative stability of the oils than refining by steam vacuum distillation. (iii) Experimental data were treated by applying a new method based on a non‐Arrhenian temperature function. The method enables trustworthy predictions of oil stabilities for the application temperatures.     

<Emphasis Type="Italic">Camelina sativa</Emphasis> Oil Deodorization: Balance Between Free Fatty Acids and Color Reduction and Isomerized Byproducts Formation

Camelina sativa oil is characterized by its high content (up to 40 wt%) of α-linolenic acid and its unique flavor. It is considered to have beneficial health properties and is suitable for food and cosmetic uses. In the present study, response surface methodology was used to optimize processing parameters for bench-scale deodorization of camelina oil. The mathematical models generated described the effects of process parameters (temperature, steam flow, time) on several deodorization quality indicators: free fatty acids (FFA), trans fatty acids (TFA), color, and polymerized triglycerides (PTG). These newly established models can be used as a tool to identify optimum deodorization process conditions within chosen constraints. Based on the optimization of minimum retained FFA with the constraint of a maximum allowable TFA, deodorization parameters can be defined. At a constant steam flow rate of 42 ml/h, a temperature range of 210–220 °C, and deodorization time of 70–120 min were defined. 220 °C appears to be a critical upper temperature limit; above this temperature, isomerization rates significantly increase.     

Oxidative flavour deterioration of fish oil enriched milk

The oxidative deterioration of milk emulsions supplemented with 1.5 wt‐% fish oil was investigated by sensory evaluation and by determining the peroxide value and volatile oxidation products after cold storage. Two types of milk emulsions were produced, one with a highly unsaturated tuna oil (38 wt‐% of n‐3 fatty acids) and one with cod liver oil (26 wt‐% of n‐3 fatty acids). The effect of added calcium disodium ethylenediaminetetraacetate (EDTA) on oxidation was also investigated. Emulsions based on cod liver oil with a slightly elevated peroxide value (1.5 meq/kg) oxidised significantly faster than the tuna oil emulsions, having a lower initial peroxide value (0.1 meq/kg). In the tuna oil emulsions the fishy off‐flavour could not be detected throughout the storage period. Addition of 5—50 ppm EDTA significantly reduced the development of volatile oxidation products in the cod liver oil emulsions, indicating that metal chelation with EDTA could inhibit the decomposition of lipid hydroperoxides in these emulsions. This study showed that an oxidatively stable milk emulsion containing highly polyunsaturated tuna fish oil could be prepared without significant fishy off‐flavour development upon storage, provided that the initial peroxide value was sufficiently low.     

Deodorization of lipase‐interesterified butterfat and rapeseed oil blends in a pilot deodorizer

A mixture of butterfat and rapeseed oil (7 : 3, wt/wt) was interesterified using immobilized lipase from Thermomyces lanuginosus at 50 °C. The interesterified mixture was then deodorized at five temperatures (60–180 °C) and three samples were withdrawn at 1, 2, and 3 h. The operation was monitored by free fatty acid (FFA) content, peroxide value (PV), volatiles, and the sensory evaluation of the samples with respect to flavor and odor (most importantly the butter flavor and odor and the off‐flavor and odor from butyric acid). ANOVA partial least squares regression analysis showed that deodorization time, and especially deodorization temperature, significantly affected the sensory properties and levels of volatiles, FFA and peroxides in the samples. The best compromise between removing undesirable off‐flavors while maintaining the desirable butter flavor seemed to be obtained by using a deodorization temperature of 120 °C for 2 h. Response surface methodology analysis showed a significant effect of deodorization temperature and, to a lesser extent, deodorization time. The butter flavor and odor had an optimum at a deodorization temperature of approximately 100–120 °C for 1–2 h. These conditions are therefore recommended in order to remove the off‐flavor and odor, while maintaining as much as possible of the attractive butter flavor and odor.     

Stripping medium requirement in continuous countercurrent deodorization

A mathematical formula was derived that allows the stripping steam requirement of the countercurrent deodorization process to be calculated as a function of system pressure, vapor pressure of the pure volatile compound, initial and final volatiles contents, and the number of transfer units (an equipment parameter) of the countercurrent deodorizer. Just as in batch or cross-flow deodorization systems, the steam requirement in countercurrent systems is proportional to the system pressure and inversely proportional to the vapor pressure of the pure volatile compound. Increasing the number of transfer units (for instance, by increasing column height) to more than two makes the countercurrent system require less steam than cross-flow systems with a vaporization efficiency of 0.6. In addition, the short residence time in a countercurrent deodorization column minimizes side reactions and allows the deodorization temperature to be raised without generating unwanted by-products such as trans-isomers and/or oligomers of unsaturated fatty acids. The increased deodorization temperature increases the vapor pressure of the pure volatiles and leads to further savings in stripping medium and motive steam. Countercurrent deodorization systems therefore require less energy than cross-flow deodorization systems and/or produce oil with fewer unwanted by-products.     

The use of electronic and human nose for monitoring rapeseed oil autoxidation

This work was aimed at assessing the effectiveness of the electronic nose to monitor off‐flavor associated with lipid oxidation as a supplementary tool to human sensory panel assessment. Therefore, correlations between electronic nose and sensory analysis were determined. Also GC analyses and chemical analyses of oil samples were run to characterize the analyzed samples with well‐described parameters. Refined rapeseed oil was subjected to an accelerated storage test for 12 days at 60 °C and to an ambient temperature storage test in which it was stored in retail plastic bottles for up to 6 months. PCA of electronic nose data samples stored at an elevated temperature was related to PCA of sensory analysis, and similarities in sample clustering were observed. For samples stored at room temperature, the human panel showed greater sensitivity than the electronic nose. Prediction models based on PLS of electronic nose data were able to predict the sensory quality changes during storage at elevated and room temperature, ranging from 0.721 to 0.989 and from 0.849 to 0.881 (p <0.05), respectively. PV and p‐AV were well predicted on the basis of both electronic nose (0.989, 0.998 for elevated temperature; 0.907, 0.881 for room temperature) and sensory analysis data (0.973, 0.993 for elevated temperature; 0.939, 0.886 for room temperature). Applicability of the electronic nose technology to verify sensory and rancidity changes during storage showed to be promising in quality control of oils.     

Flavour reversion in linseed shortening

Summary 1. The production of an edible shortening by the hydrogenation of linseed oil with dry-reduced nickel catalyst has been studied. 2. A derivative of linolenic acid formed during hydrogenation, is shown to be responsible for flavour reversion in linseed oil shortening. It is believed that this substance decomposes to form the volatile products directly responsible for the reverted flavour and odour. 3. Possibilities of producing linseed oil shortening free of reversion have been investigated as to (a) pretreatment of the oil, (b) changing hydrogenation conditions, (c) changing the hydrogenation product by isomerization, (d) destruction of the offensive product of hydrogenation and removal by deodorization, and (e) the use of antioxidants to inhibit reversion in the hydrogenated product. 4. Improved products have been obtained but flavour reversion has never been entirely eliminated. Macdonald College Journal Series No. 192. Issued as paper No. 118 of the Canadian Committee on Food Preservation.     

Thermal degradation of long‐chain polyunsaturated fatty acids during deodorization of fish oil

Long‐chain polyunsaturated fatty acids (LC‐PUFA) of the n‐3 series, particularly eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid, have specific activities especially in the functionality of the central nervous system. Due to the occurrence of numerous methylene‐interrupted ethylenic double bonds, these fatty acids are very sensitive to air (oxygen) and temperature. Non‐volatile degradation products, which include polymers, cyclic fatty acid monomers (CFAM) and geometrical isomers of EPA and DHA, were evaluated in fish oil samples obtained by deodorization under vacuum of semi‐refined fish oil at 180, 220 and 250 °C. Polymers are the major degradation products generated at high deodorization temperatures, with 19.5% oligomers being formed in oil deodorized at 250 °C. A significant amount of CFAM was produced during deodorization at temperatures above or equal to 220 °C. In fact, 23.9 and 66.3 mg/g of C20 and C22 CFAM were found in samples deodorized at 220 and 250 °C, respectively. Only minor changes were observed in the EPA and DHA trans isomer content and composition after deodorization at 180 °C. At this temperature, the formation of polar compounds and CFAM was also low. However, the oil deodorized at 220 and 250 °C contained 4.2% and 7.6% geometrical isomers, respectively. Even after a deodorization at 250 °C, the majority of geometrical isomers were mono‐ and di‐trans. These results indicate that deodorization of fish oils should be conducted at a maximal temperature of 180 °C. This temperature seems to be lower than the activation energy required for polymerization (intra and inter) and geometrical isomerization.     

Gegenstrom-Fallfilm-Treibdampfdestillation mittels eines von außen aufgezwungenen Temperaturfeldes zur wirksamen Desodorierung von Fettsäuren und Speiseölen

Countercurrent Falling Film Steam Distillation Using Externally Applied Temperature Field for Efficient Deodorization of Fatty Acids and Edible Oils The impact of externally applied temperature field on steam deodorization in countercurrent film flow is discussed. Wavelike movement of a film flowing downwards vertically, in combination with additional film movement caused by lateral heat flow, leads to continuous renewal of the surface. Consequently, volatile impurities present in minute amounts which contribute to flavour and taste, have ample opportunity during flow of the film to reach the surface of the film and get in direct contact with the stripping steam. This transfer is facilitated by additional wave-like movement of the falling film. It is to be expected, that this countercurrent deodorization process enables favorable utilization of stripping steam at minimum pressure drop and maximum saturation with the volatile substances responsible for taste and flavor. This means low energy cost in fully continuous operation at minimum contact times, which result in minimum thermal stress on the material treated.     

Effect of physical refining on selected minor components in vegetable oils

The final quality of vegetable oils is largely determined by the deodorization process. From an organoleptic point of view, oils should be light in color with a bland taste and a good cold and/or oxidative stability. Today, however, more and more attention is paid to the real nutritional quality. Oils should contain low trans fatty acid levels, low polymeric triglycerides, and secondary oxidation products and at the same time being rich in natural antioxidants. In order to comply to these new quality requirements, the deodorization technology has been modified substantially. Mathematical models were established describing the influence of different process parameters (time, temperature, steam, and pressure) on trans fatty acid formation, tocopherol stripping, and production of oxidized and polymeric triacylglycerides during physical refining of soybean oil. Trans fatty acid (TFA) formation was influenced only by time and temperature. No significant influence of pressure or sparging steam could be observed. Models expressing the relative degree of cis/trans-isomerization of linoleic (DI_18:2) and α-linolenic acid (DI_18:3) could be extrapolated to other oils and deodorizer designs. Tocopherol removal was mainly influenced by process temperature and sparging steam. Additionally, tocopherol retention seemed to be dependent on the deodorizer design (steam injection geometry and sparging steam distribution). During physical refining, oxidized and polymerized triacylglycerols were not significantly influenced by any of the investigated process parameters. Industrially, process conditions are adapted to minimize trans fatty acid formation and maximize tocopherol retention. These goals can be achieved in a so-called DUAL TEMP^copy; deodorizer.     

Simulation of continuous deodorizers: Effects on product streams

This work deals with the simulation of deodorization, one important process in the edible oil industry related to the removal of odoriferous compounds. The deodorizer was modeled as a multicomponent stripping-column in cross-flow and countercurrent flow. The impact of processing parameters on the quality of the product streams was analyzed. The deodorization of soybean and canola oils (plant scale) and wheat germ oil (lab-scale) was studied under typical ranges of temperature, stripping steam rate, and pressure. Their entire compositions were considered within the simulations, including acylglycerols, FFA, and other key components such as tocopherols and sterols. The deodorization results were analyzed in terms of retention of tocopherol and sitosterol and of neutral oil loss to the distillate. The deodorizer modeling considered Murphree efficiencies and entrainment for each plate. A case study, i.e., the deodorization of soybean oil, illustrated the applicability of our modeling.     

Oxidative stability of diacylglycerol oil and butter blends containing diacylglycerols

Diacylglycerol (DAG) oils produced from sunflower oil and traditional sunflower oil were stored for 20 wk at 38 °C, and their oxidative stability was measured. Moreover, two butter blends were produced containing 40 wt‐% DAG oil made from sunflower oil or rapeseed oil, respectively, as well as two control butter blends with sunflower oil or rapeseed oil. Their oxidative stability during storage at 5 °C for up to 12 wk was examined by similar means as for the pure oils. The storage study of the oils indicated that the DAG oil was oxidatively less stable as compared to sunflower oil, but that they had similar sensory quality. Storage of the butter blends revealed that blends with the two types of rapeseed oil (triacylglycerol (TAG) or DAG oil) were oxidatively more stable than the blends containing oils from sunflower. There was no unambiguous indication of DAG butter blends having a different stability than their respective control TAG blends. However, they had a significantly less salty and buttery flavour, which was ascribed to a much smaller water droplet size causing a delayed sensory perception in the mouth. The butter blend with DAG oil from rapeseed had a very neutral flavour. On the contrary, the butter blend with DAG oil from sunflower had a more rancid aroma and flavour than its control blend with sunflower oil.     

Laboratory continuous deodorizer for vegetable oils

A laboratory-scale continuous deodorizer, based on a modified Snyder distillation column, was constructed and tested for the deodorization of alkali-refined and bleached vegetable oils. Soybean oil extracted with supercritical carbon dioxide and without further processing also was deodorized to a finished edible oil. Results of taste panel evaluations of the finished oils show that the quality of oils deodorized over a temperature range of 194–260 C is equivalent to commercial salad oils. Oil flow rates are 1 to 2 ml/min, and contact time is about 5 min; a vacuum of 0.5 to 1.0 mm Hg is maintained with countercurrent steam flow of 1 to 5% of the oil weight. Small samples of oil (250–1000 ml) are readily accommodated in this equipment, and the deodorization conditions more nearly simulate commercial practice than do traditional small-scale batch deodorizers. Presented at the AOCS meeting in Philadelphia, PA in May 1985.     

Features of the De Smet Deodorizing Systems

Deodorization as applied to edible oils, is a refining step meant to eliminate odoriferous matters by distillation. There are a multitude of components imparting disagreable taste and flavour to crude oils; most of these have been identified by capillary gas chromatography of the head space. These products are partially removed in refining stages prior to deodorizing. Certain odoriferous substances in infinitesimal proportions are tenacious and most intimately linked to the glyceride. These are the ones that give to each oil its characteristic flavour. The consumer is generally most demanding and will not tolerate any flavour and still less any aftertaste in the refined oil. This is why deodorization of edible oils in a refining line is of the utmost importance and should be carried out under optimum conditions and with an adequate equipment. The discerning use of the live steam which is the stripping media during deodorization-distillation, acceptable heat recovery, minimum level of pollutants in the effluent streams and the flexibility and reliability of operation should be the main features of a modern deodorizer. In this paper the main principles of deodorization are mentioned and the currently available De Smet Deodorizers and vapors scrubbing units emphasizing their major features are described.     

Pure H2 production through hollow fiber hydrogen‐selective MFI zeolite membranes using steam as sweep gas

Hollow fiber MFI zeolite membranes were modified by catalytic cracking deposition of methyldiethoxysilane to enhance their H₂/CO₂ separation performance and further used in high temperature water gas shift membrane reactor. Steam was used as the sweep gas in the MR for the production of pure H₂. Extensive investigations were conducted on MR performance by variations of temperature, feed pressure, sweep steam flow rate, and steam‐to‐CO ratio. CO conversion was obviously enhanced in the MR as compared with conventional packed‐bed reactor (PBR) due to the coupled effects of H₂ removal as well as counter‐diffusion of sweep steam. Significant increment in CO conversion for MR vs. PBR was obtained at relatively low temperature and steam‐to‐CO ratio. A high H₂ permeate purity of 98.2% could be achieved in the MR swept by steam. Moreover, the MR exhibited an excellent long‐term operating stability for 100 h in despite of the membrane quality. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3459–3469, 2015     

Geometrical isomerization of polyunsaturated fatty acids in physically refined rapeseed oil during plant‐scale deodorization

The effect of the operating temperature (between 220 and 270 °C) on the formation of trans isomers of linoleic and linolenic acids in physically refined rapeseed oil during deodorization in a plant‐scale semicontinuous tray‐type deodorizer (capacity 10 t/h) was investigated. The industrial procedures of physical refining consisted of a two‐step bleaching and deodorization process. The degree of isomerization of linoleic acid ranged from 0.33 to 4.77% and that of linolenic acid from 4.43 to 45.22% between 220 and 270 °C, respectively. A relation between the logarithm of the degree of isomerization and the deodorization temperature can be approximated by statistically highly significant linear functions for both linoleic and linolenic acids. Oleic acid was resistant to the heat‐induced geometrical isomerization. The values found for the ratio between the degrees of isomerization of linolenic and linoleic acids, slightly decreasing with increasing temperature, were equal to 13.6 and 12.9 at 230 and 240 °C, respectively. Two trans isomers of linoleic acid, exclusively with one double bond isomerized into trans configuration, and four trans isomers of linolenic acid, mostly with one double bond isomerized into trans configuration, were determined in deodorized rapeseed oils. Linolenic acid was observed to be the main source responsible for the formation of nearly all trans fatty acids in physically refined rapeseed oil. At 235 °C, a deodorization temperature considered as a reasonable technological compromise, the content of trans fatty acids in plant‐scale physically refined rapeseed oil was less than 1% of total fatty acids, which would be acceptable for further application.     

Rheological properties and sensory texture of mayonnaise

Mayonnaises are viscoplastic oil‐in‐water emulsions, in which rheological properties have important influences on functional properties and the sensory quality. A set of 17 samples of both traditional and light mayonnaises were tested at 10 and 25 °C, using a rheoviscometer Rotovisco RT 10. Nonlinear relations were observed between the yield value and the apparent viscosity. The yield value was correlated with several sensory characteristics rated after manipulation with a spoon, but not in oral testing. No relations were obtained between the apparent viscosity and sensory characteristics. The yield value and the texture acceptability were related significantly to the flavour acceptability. Multivariate statistical techniques were found advantageous for improving the prediction of the texture acceptance.     

Physical refining of coconut oil: Effect of crude oil quality and deodorization conditions on neutral oil loss

In the present study, neutral oil loss (distillative and mechanical carry-over) during physical refining of coconut oil was quantified. Neutral oil loss seems to depend on both the crude oil quality and the process conditions during deodorization. The distillation of volatile glyceridic components (monoand diglycerides), originally present in the crude oil, was confirmed as the major cause for the neutral oil loss. The amount of these volatile components in crude coconut oils cannot be derived as such from the initial free fatty acid content. A lower deodorization pressure with less sparge steam resulted in a larger neutral oil loss than a higher pressure with more steam. A “deodorizability” test on a laboratory scale under standardized conditions (temperature=230°C, pressure=3 mbar, time=60 min, sparge steam=1%), to evaluate crude oil quality and to obtain a more accurate prediction of the expected neutral oil loss and free fatty acid content in the fatty acid distillate, is described.     

Effects of physical refining on contents of waxes and fatty alcohols of refined olive oil

Changes in the contents of waxes and fatty alcohols during deodorization/physical refining of bleached olive oil were studied. Experiments were carried out with 1.85% acidity oil, which was physically refined in a discontinuous deodorizer of 250-kg maximum capacity using nitrogen as stripping gas instead of steam. The variables studied were load and temperature of oil in the deodorizer as well as N₂ flow. Analyses of waxes and alcohols were carried out at different operation times. The maximum content of wax was always observed when the oil reached the deodorization temperature. The variation in the wax content depended on temperature and N₂ flow. Wax decomposition started and continued during the operating time, and a progressive decrease, which was pronounced between 3 and 4 h, was observed. Small changes in waxes were observed between 4 and 5 h. Total content of fatty alcohols diminished throughout the operating time, and changes did not depend on the variables studied.