The influence of palm oil quality on the refining conditions

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1 The influence of palm oil quality on the refining conditions Klicia A. Sampaio a, *, Jose V. Ayalla b, Simone M. Silva a, Roberta Ceriani c, Roland Verhé d and Antonio J. A. Meirelles a a EXTRAE, Food Engineering Faculty, University of Campinas, Zip Code, , Campinas, São Paulo, Brazil (klicia@fea.unicamp.br)* b Desmet & Ballestra R&D Center, Zip Code, 935, Zaventem, Belgium (jose.vila.ayala@desmetballestra.com) c School of Chemical Engineering, University of Campinas, Zip Code, , Campinas, São Paulo, Brazil (rceriani@feq.unicamp.br) d Faculty of Bioscience Engineering, Ghent University, Zip Code, 9000, Ghent Belgium (roland.verhe@ugent.be) ABSTRACT Palm oil presents a unique composition resulting in an edible oil that is suitable for use in a variety of food applications. The Brazilian palm oil presents normally acidity values not higher than 3.5%, showing its suitable quality. Refining of palm oil is preferably performed by physical means, due to its high acidity that can lead to excessive losses of neutral oil. Physical refining is a process in which free fatty acids and other volatile compounds are removed from the oil by applying high temperatures and low pressures, with the addition of live steam as a stripping gas. However, depending on the initial oil quality, lower temperatures and less amount of stripping gas could be used to reach the desirable parameters for edible oils. Thus, the aim of this work was to verify the effects of two operating parameters i.e., temperature (00 C to 60 C) and steam flow (0.5% to 3.5%), and one quality parameter, i.e., the initial oil acidity (.% to 6%) in the removal of free fatty acids and loss of neutral oil, following a 3 factorial design. The steam deacidification experiments were carried out in a laboratory-scale batch deodorizer. The glass batch deodorizer was loaded with bleached palm oil and placed in an oven with controlled and monitored temperature. The experimental results revealed the final oil acidity and neutral oil loss (NOL) were a function of the three variables studied. However, it was possible to see that the effect of temperature was predominant in both responses, followed by the steam percentage, the initial oil acidity and the interactions between the independent variables considered in this work. Keywords: physical refining; neutral oil loss; free fatty acids; quality parameters. INTRODUCTION During the last years palm oil industry reached a highlighted position in the worldwide production of oils and fats. The change is connected to the high-oil-yield per hectare obtained for oil palm, which is around 0 times more than the average production (0.35 tonnes oil/ha) obtained for soybean oil. In general, palm oil contains 40% of oleic acid (monounsaturated fatty acid), 0% of linoleic acid (polyunsaturated fatty acid), 45% of palmitic acid and 5% stearic acid (saturated fatty acids). This composition results in an edible oil that is suitable for use in a variety of food applications []. Palm oil is derived from the fleshy part or the mesocarp of the palm oil fruit. The unripe fruits contain very little oil but the mesocarp of ripe fruits has an oil content of 70 75% of its total weight. A powerful hydrolytic enzyme is present on the exterior of the palm fruits, and if it is not deactivated promptly after harvesting, any oil escaping from damaged fruits or during processing splits rapidly into free fatty acids (FFA) and partial acylglycerols. High acylglycerols and FFA content must be avoided, as it will result in higher neutral oil losses (NOL) and possible bleachability problems during refining, respectively. The reported range of free fatty acid content of crude palm oil was.3 6.7% []. The quality of any crude oil is to be considered as it can greatly affect the efficiency of the refining process and the quality of the end-products. The most used parameters to asses crude palm oil quality is: FFA; phosphatide content; peroxide value (PV); metal traces and more recently the deterioration of bleachability index (DOBI) [3]. Although, the FFA is one of the most frequently determined quality indices during the production, storage and market of palm oil products and the oil price is dictated by FFA content [] Edible oils are refined in order to remove unacceptable materials with the least possible loss of oil and without affecting desirable compounds that are present in the oil in small quantities [4]. Refining of palm oil

2 is preferably performed by physical means, since its high acidity can lead to excessive losses of neutral oil in case of the caustic refining process. Physical refining of vegetable oil is a distillation process in which, under low absolute pressure and high temperatures, the accompanying lower boiling compounds are distilled off from fatty acids triglycerides, by using gas, usually steam, as effective stripping agent [5] Response surface methodology (RSM), enables evaluation of the effects of many factors and their interactions on response variables. For multivariable processes such as food systems, a large number of factors can influence the responses of the process. The main advantage of RSM is the reduced number of experimental runs needed to provide sufficient information for statistically acceptable results [6]. Thus, the aim of this work was to verify the effects of two operating parameters i.e., temperature (ranging from 00 C to 60 C) and steam flow (from 0.5% to 3.5%), and one quality parameter, i.e., the initial oil acidity (from.% to 6%) in the removal of free fatty acids and loss of neutral oil, following a 3 factorial design. MATERIALS & METHODS Crude palm oil (CPO) was kindly provided by the industry (Agropalma S/A, Amazon Refining Company, Brazil). The oil was then submitted to regular degumming and bleaching process. Commercial oleic acid (MERCK, USA) was added to adjust the acidity of each model system. All chemicals used were analytical grade. All samples were storaged at freezing temperature (-8 C) prior to analysis. In all the trials, samples of the refined oil and of the distillate were analyzed. The FFA content was determined by titration, and expressed as % oleic acid according to the official method Ca 5a-40 (AOCS, 998). Experimental Design The experimental design employed for the analysis was a central composite design. The experiments were carried out using a 3 full-factorial design with three central points to estimate the reproducibility of the trials. The independent variables were temperature (X ), steam flow (X ) and initial oil acidity - IOA (X 3 ). It was estimated five different oil systems with different initial oil acidity. Surfaces of coded variables and independent variables were then built using the quadratic models for the statistically significant variables. The experimental results were analyzed using the software Statistica (Statsoft, v.5.5) to establish the effects of the process variables on the responses of interest. Physical refining process Physical refining experiments were conducted in a laboratory-scale bath deodorizer (Desmet & Ballestra, Zaventem Belgium). Degummed and bleached palm oil (300g) was blended with oleic acid to obtain an initial FFA content varying from.% to 6.0%. The blend was introduced in a glass bath deodorizer (000 ml fat flask) and placed in hot air oven (Heraeus, Germany) with controlled and monitored temperature. After degassing, under a low absolute pressure (8 mbar) the oil was heated to the desired process temperature and the pressure was adjusted to the desired value. When the oil temperature reached the given value of the factorial design (Table ), the flow rate of the stripping gas was started at the desired value. The steam injection was set by adjusting the water flow rate via a microperistaltic pump. Water was vaporized in a stainless steel heating coil, which was placed inside of the deodorizer, preventing fluctuations in flow rate and droplet entrainment. After the microperistaltic pump, the whole water and live steam were under the same vacuum prevailing inside the deodorizer flask. In each experiment, the stripping time was fixed at 60 min. After deodorization, the oil was cooled under vacuum to temperature lower than 80 ºC. The deacidified oil was weighed to allow for the calculation of NOL by difference. All samples were then storaged in a opaque glass vessel under nitrogen atmosphere at -8 ºC until further analysis. RESULTS & DISCUSSION Table shows de responses, i.e. the final FFA and the neutral oil loss (NOL) for the refined oil, after the deacidification process at different temperatures, steam percentage and initial oil acidity (IOA). The experimental results revealed that the final FFA and the NOL were a function of the three variables studied. However, the effect of the temperature was predominant in both responses, followed by the steam percentage.

3 Comparing trials 9 and 0 (X varying from -α to +α), it is possible to verify the effect of increasing temperature (T) from 00 ºC to 60 ºC on the decrease in the final FFA and on the increase in NOL, due to volatilization of fatty compounds at higher temperatures. A comparison of trials and (X varying from - α to +α) showed that an increase in the steam percentage from 0.50 to 3.5%, promoted a decrease in the final oil acidity and an increase in the neutral oil loss, since it reduced the required partial pressure of the volatiles. The effect of increasing the initial oil acidity from. to 6.0 (X 3 varying from -α to +α) on the removal of FFA and on the NOL can be seen by comparing trials 3 and 4. From them, one can see that the variable initial oil acidity presented a slightly effect in both responses. Table. Central composite design, experiment data for the physical refining of palm oil Trial Real Variables Responses T ( C) Steam (%) IOA (%) Final FFA (%) a NOL (%) b ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± a Values expressed as % of oleic acid; b Calculated by difference For the model fitted, the software generated model coefficients, R -values, F-values, and significant probabilities. From those values, one can justify the significance of each experimental variable. The statistical analysis of the experimental results shown in Table revealed significant effects (p = 0.95) for the temperature, steam percentage and initial oil acidity for the response final FFA. Nevertheless, only the temperature and the steam percentage seemed to be significant for the NOL in the models system. It probably happens because we are working with model systems, which present the initial oil acidity modified by the addition of oleic acid. But the oil composition in terms of triacylglycerols and partial acylglycerols was not modified. The part of neutral oil lost during stem stripping is usually very rich in partial acylglycerols. Equations and represent the final FFA and the loss of neutral oil, respectively, as a function of the statistically significant variables. FinalFFA (%) X X. X X. X X X X X Eq. () 3 NOL(%) X X Eq. () X X X X. Where X, X and X 3 are the coded variables for T ( C), steam percentage and the initial oil acidity, respectively. The ANOVA showed that the models appeared to be adequate, with no significant lack of fit (p > 0.05), and with a satisfactory coefficient of determination (R ). The R values of Eqs. () and () were and , respectively. According to the models for final FFA and NOL, the observed experimental responses were close to the predicted results.

4 Using these models it was possible to draw surfaces that represented the influence of different temperatures, steam percentages and initial oil acidities (IOA) on the final FFA value (Fig. ) and neutral oil loss (Fig. ). Figures shows that by increasing the process temperature and steam percentage, a significant reduction in the final oil acidity can be achieved, providing evidence of the synergetic effect between these variables. Figure shows that, for any initial oil acidity and high temperatures an effect of increasing the neutral oil loss is observed. It is important to remember that the model systems used were composed of a good quality bleached palm oil, with initial acidity of.% (expressed as oleic acid) and consequently low amounts of partial acylglycerols. Figure. Response surface as a function of temperature (ºC) and steam (%) for final FFA. Figure. Response surface as a function of temperature (ºC) and initial oil acidity (%) for neutral oil loss. CONCLUSION It was possible to conclude that for the physical refining of palm oil, the variables temperature and steam percentage presented the predominant effects. However, for the response final FFA the effect of the initial oil acidity was also significant, providing evidences of the need for the previous analysis of the oil before sending it to the commercial refining process. This is especially important on the production of edible oils with high amount of minor components, which are usually destroyed by the high temperatures applied during

5 the refining process. Considering the response neutral oil loss, only the effect of temperature and steam percentage were significant, since the amount of partial acylglycerols into the oil was not modified with the addition of oleic acid, which was used to compose the model systems. REFERENCES [] GEE, P. T Analytical characteristics of crude and refined palm oil fractions. European Journal of Lipid and Science Technology, 09, [] Tan, C.-H., Ghazali, H. M., Kuntom, A., Tan, C.-P. and Ariffin, A. A Extraction and physicochemical properties of low free fatty acid crude palm oil, Journal of Food Engineering, 3(), [3] Gibon, V., De Greyt, W. and Kellens, M. 007, Palm oil refining. European Journal of Lipid Science and Technology, 09(), [4] Rossi, M., Gianazza, M., Alamprese, C. and Stang, F. 00. The Effects of Bleaching and Physical Refining on Color and Minor Components of Palm Oil. Journal of the American Oil Chemistry Society, 78(), [5] Sampaio, K. A., Ceriani, R., Silva, S. M., Taham, T., Meirelles, A. J. A. 00. Steam Deacidification of Palm Oil, Food and Bioproducts Processing, doi:0.06/j.fbp [6] BOX, G.E.P. and HUNTER, J.S Statistic for Experimenters An Introduction to Design, Data Analysis, and Model Building. John Wiley & Sons, New York, USA.