Physical and chemical properties of soybean oil bleached with bleaching earth containing increased amounts of aluminum and magnesium oxides

Document Type : Full Research Paper

Authors

• Bahareh Khaligh ¹
• Maryam Gharachorloo ¹
• Peymaneh Ghasemi Afshar ²

¹ Department of Food Science & Technology, Science and Research Branch, Islamic Azad University, Tehran, Iran.

² Department of Food Science & Technology, Hidaj Branch, Islamic Azad University, Zanjan, Iran.

https://doi.org/10.22067/ifstrj.v16i5.82266

Abstract

Introduction: The impurities of the oil and its pigments are basically removed from the oil by physical adsorption using an adsorbent during the bleaching process. The bleaching process involves the removal of pigments, impurities, metals and oxidation products. Removal of these substances is essential in oil refining because it improves the stability, appearance and sensory quality of the oil. Activated bleaching earth is the most commonly used adsorbent for purifying and improving the color of fats and oils. The bleaching process of edible oils is important for producing light colored oils with acceptable quality. The aim of this study was to evaluate the physical and chemical properties of soybean oil bleached with bleaching earth containing increased amounts of aluminum and magnesium oxides.
 
Material and Methods: Bleaching earth was purchased from Kanisaz Jam Company. Degummed and neutralized soybean oil was obtained from Behshahr Vegetable Oil Company. Different amounts of aluminum oxide and magnesium oxide were added to commercial bleaching earth. Activation of the adsorbents was performed with hydrochloric acid and oil bleached at 110°C for 30 min under vacuum by adding 2% of adsorbent containing different percentages of silica, aluminum and magnesium oxides. A series of physical and chemical tests such as peroxide value, acid value, chlorophyll content, carotenoid content, yellow and red colors and amounts of copper and iron were then carried out on the neutralized and bleached oils according to the standard methods. All the experiments and/or measurements were carried out in triplicate. Data were statistically analyzed using the Statistical Analysis System software package on replicated test data. Analysis of variance was performed by application of an ANOVA procedure. Significant differences between the means were determined using the Duncan multiple range test.
 
Result and Discussion: The results of this study showed that the examined adsorbents reduced the peroxide value to 98.9-96.3%. Application of the adsorbents containing 95% commercial bleaching earth - 5% aluminum oxide and 95% commercial bleaching earth - 5% acidic aluminum oxide reduced the acid value by 33.33% and 26.66%, respectively. The amount of chlorophyll in the control sample was 7.58 mg Pheophytin A/kg oil, which reduced 65.66% by using adsorbent containing 90% commercial bleaching earth and 10% magnesium oxide and reached to 1.90 mg Pheophytin A/kg. The amount of carotenoids in the control sample was 7.88 mg/kg. Using the adsorbent containing 90% commercial bleaching earth and 10% magnesium oxide decreased carotenoids up to 93.40%. Adsorbents containing 95% commercial bleaching earth and 5% aluminum oxide, 95% commercial bleaching earth and 5% magnesium oxide, 95% commercial bleaching earth and 5% acidic magnesium oxide and commercial bleaching earth had the same effect on red color reduction. Yellow color in the oil samples treated with commercial bleaching earth, adsorbent consisting of 90% commercial bleaching earth - 10% aluminum oxide, and adsorbent containing 95% commercial bleaching earth - 5% magnesium oxide was reduced and reached to 38, 50 and 50 Lovibond, respectively as compared to the control sample with yellow color of 70.00 Lovibond. Copper and iron decreased 100% by using adsorbents containing 50% commercial bleaching earth and 50% aluminum oxide or 50% commercial bleaching earth and 50% magnesium oxide.
According to our findings, the addition of aluminum and magnesium oxides to commercial bleaching earth was effective in reduction of peroxide value, acid value, chlorophyll, carotenoid, red and yellow color, copper and iron. Also, the results showed that the best adsorbent contain about 50% aluminum and magnesium oxides. Aluminum and magnesium oxides can improve the performance of bleaching earths.

Keywords

• Aluminum Oxide
• Bleaching
• Magnesium Oxide
• Soybean oil
• Bleaching earth

References

Abbasi R, Gharachorloo M, Ghavami M, Asadi Gh-H. (2014). Appilication of ultrasonic waves in bleaching of soybean oil and determination of time and temperature for ultrasonic bath. Iranian Journal of Nutrition Science & Food Technologhy, 9(2): 75-84.

Ajemba, R.O.,Onukwuli, O.D.(2012). Journal of Basic and Applied Scientific Research, 9: 9438-9445.

Anonymous. (2001). Edible oils and fats-Determination of carotene-test method. National Standards Organization of Iran, National Iranian Standard, No. 6686.

AOCS ( 2007). Official methods and recommended practice of the American oil chemist’s society.

AOCS ( 2004). Official methods and recommended practice of the American oil chemist’s society.

De B.K., Patel, J.D., Patel, J.B., Patel, V.K., Patel, V.R.(2009). Bleaching of mustard oil with some alternative bleaching agents and acid activated clays. Journal of of Oleo Science, 58:57-63.

Didi, M.A., Makhoukhi, B., Azzouz, A. and Villemin, D., (2009). Colza oil bleaching through optimized acid activation of bentonite. A comparative study. Applied Clay Science, 42(3-4): 336-344.

Farhoosh, R. Einafshar, S. And Sharayei, P. (2009). The Effect Of Commercial Refining Steps On The Rancidity Measures Of Soybean And Canola Oils. Food Chemistry, 115: 933-938.

Foletto, E. L., Colazzo G. C., Volzone C., Porto L. M.(2011). Sunflower oil bleaching by adsorption onto acid-activated bentonite. Brazilian Journal of Chemical Engineering, 28(1): 169 – 174.

Ghasemi Afshar, P., Honarvar, M., Gharachorloo, M., Eshratabadi, P., and Bazyar, B. (2014). Bleaching of vegteble oils using press mud obtained from sugar industry. Pelagia Research Library, 4(1): 677-684.

Ghasemi Afshar P. (2014). Investigating the use of cake filter made from the sugar production line in the bleaching of edible oils. Ph.D. Thesis. Faculty of Science and Engineering, Food Industry, Islamic Azad University, Science and Research Branch of Tehran.

Ghavami M, Gharachorloo M, , Ghiassi Tarzi B. (2008). Laboratory Techniques Oils & Fats. Islamic Azad University-Science and Research Branch, First edition.

Ghavami M, Gharachorloo M, Mahasti P. (2003). The Effect of purification process on quality characteristics of soybean oil. Journal of Agricultural Sciences, 9(3), 55-68.

Ghobadi M, Yuzbashi A. A, Kashani Motlagh M. M. (2008). Study on the structural changes occurred during the acid activation of Gharenaz bentonite as bleaching earth. Iranian Journal of Crystallography and Mineralogy, 16(1): 13-20.

Gibon, V., De Greyt, W., & Kellens, M. (2007). Palm oil refining. European journal of lipid science and technology, 109(4): 315-335.

Gupta, M.(2017). Practical guide to vegetable oil processing. Elsevier, second edition.

Hoseini S. M. S, Sarafi A, and Tahmooresi, M. (2012). Laboratory study of balloon impact on the structure and strength of bentonite dyeing for the production of bleaching soil. Journal of Chemistry and Chemical Engineering of Iran, 32(1): 35-45.

Hussin, F., Aroua, M. K., & Daud, W. M. A. W. (2011). Textural characteristics, surface chemistry and activation of bleaching earth: A review. Chemical Engineering Journal, 170(1): 90-106.

Kaynak, G., Ersoz, M., & Kara, H. (2004). Investigation of the properties of oil at the bleaching unit of an oil refinery. Journal of Colloid and Interface Science, 280(1):131-138.

Lin, R., and Lin, Ch. (2005). Kinetics of adsorption of free fatty acids from water-degummed and alkali-refined soy oil using regenerated clay. Journal of Separation Purification Technology, 44: 258-265.

Makhoukhi, M. A. Didi, D. Villemin and Azzouz. (2009). Acid activation of bentonite for use as a vegetable oil bleaching agent . Grasasy Aceites, 60(4): 343-349.

Naji M. H, Ghavami M, Lari A. (2010). The Effect of Different Bleaching Earths on the Quality Edible Oils. Food Technology & Nutrition, 7(4): 5-19.

O'brien, R. D. (2008). Fats and oils: formulating and processing for applications. CRC press.

Okolo, J. C., & Adejumo, B. A. (2014). Effect of Bleaching on Some Quality Attributes of Crude Palm Oil. IOSR Journal of Engineering (IOSRJEN), 4: 25-28.

Prokopov, T., & Mechenov, G. (2013). Utilization of spent bleaching earth from vegetable oil processing. Ukrainian Food Journal, 2(4).

Silva, S. M., Sampaio, K. A., Ceriani, R., Verhe, R., Stevens, C., De Greyt, W., & Meirelles, A. J. (2014). Effect of type of bleaching earth on the final color of refined palm oil. LWT-Food Science and Technology, 59(2): 1258-1264.

Saneei M, Goli S. A. H, Keramat J and Shirvani M. (2014). Acid activation of sepiolite clay to bleach edible oils. Journal of Food Resarch, 25(4): 689-698.

Shokrchizad H, Goli S. U. H. and Daghighi H. (2012). Recovery and analysis of residual oil in soap dyes used in soybean oil purification. Journal of Food Science and Technology of Iran, 9(1): 104-101.

Anonymous, (2001). Edible oils and fats-Determination of carotene-test method. National Standards Organization of Iran, National Iranian Standard, No. 6686

Anonymous. (2001). Edible oils and fats-Determination of carotene-test method. National Standards Organization of Iran, National Iranian Standard, No. 6686.