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Quality of Oil Used to Prepare French FRIes in Dhaka City

M. A. Kabir*
Institute of Food Science & Technology (IFST), BCSIR, Dhaka, Bangladesh

S. Khan
Institute of Food Science & Technology (IFST), BCSIR, Dhaka, Bangladesh

S. A. Lisa
Institute of Food Science & Technology (IFST), BCSIR, Dhaka, Bangladesh

F. Islam
Institute of Food Science & Technology (IFST), BCSIR, Dhaka, Bangladesh

Abstract/ Executive Summary:

To evaluate the quality of oil used to prepare French fries, fifteen samples of three different categories were collected from Dhaka city. Using solvent extraction method, oils were extracted from the samples. Fatty acid composition, color, peroxide value (PV) and free fatty acids (FFA) of the extracted oils were analyzed. It was found that soybean oil and palm oil were used for frying purpose. Majority of the samples (60%) had peroxide value more than 10 meqO2/kg with highest value of 17.57(±1.39) meqO2/kg. Average color score was found 53.17(±12.73), yellow score was 17.16(±3.79) and red score was 7.2(±3.27). FFA content of the extracted oils were 0.33(±0.29) with the highest value 1.828(±0.029). Fatty acid composition revealed that palmitic acid and oleic acid were the dominant fatty acid with the highest concentration of 43.71±3.39% and 49.54 ±3.6314% respectively. Trans fatty acid was found in 80% of the extracted oils, most frequent trans fat was trans linoleic acid (C18:2) where as trans oleic acid (C18:1) was found in highest concentration 3.7020 ±0.3448. PV and trans fatty acids revealed that the quality of oil used in low cost shops were lower than middle and high cost shops.

Keywords: French fries; Oil quality; Fatty acid composition; Fatty acids; Trans fatty acid; Peroxide value; Free fatty acid

Location: Institute of Food Science & Technology (IFST), BCSIR, Dhaka, Bangladesh

Start Date:

End Date:

Program Area: Quality and Nutrition

Commodity: Oil

Objectives:

This experiment designed to observe the quality of oil in fried products as well as to find the difference of oil quality in fried French fries from shops of different price.

Methodology:

Materials French fries samples were collected from local shops. Based on the price of sample, shops were categorized into three groups, high cost (HC), medium cost (MC) and low cost (LC). After collecting, samples were brought to the laboratory of Oilseed and Lipid Technology Research section, Institute of Food Science and Technology (IFST), Bangladesh Council of Scientific and Industrial Research (BCSIR). Oil extraction In the laboratory the samples were cut into small pieces of about 1 cm², 400 g of samples were placed in a conical flask, 500 mL of petroleum ether (Merck, Mumbai, India) was taken into the flask, shaked well for proper mixing and kept overnight for oil extraction. The solvent with oil was then filtered through filter paper, evaporated in water bath and the extracted oils were kept in sample bottle for analysis. Peroxide value, acid value and color estimation Peroxide value Peroxide value (PV) was estimated according to AOCS Official Method 965.33. Five grams (5±0.05g) of oil samples were weighed into a glass-stoppered Erlenmeyer conical ?ask and 30 ml of glacial acetic acid (Merck, Germany) -chloroform (RCI Labscan, Thailand) mixture in the ratio of 3:2, respectively, were added to the oil samples. Half ml saturated potassium iodide (KI) (Merck, Germany) solution was added to the solution and allowed to stand for 1 min thereafter, 30 ml of distilled water was added and titrated with 0.1 M sodium thiosulfate (Merck, Germany) solution using starch indicator until the blue color was discharged. A blank was prepared to correct the calculation. Free fatty acid Free fatty acid (FFA) was measured with a slight modification of AOAC (2005). One to three gram (1-3g) of oil sample was weighed into a 250 mL conical flask and dissolved with 25 mL distilled ethanol was added. Two drops of phenolphthalein indicator were added to the flask and titrated to faint pink end point with 0.1 N potassium hydroxide (KOH) (Merck, Germany). Free fatty acid Free fatty acid (FFA) was measured with a slight modification of AOAC (2005). One to three gram (1-3g) of oil sample was weighed into a 250 mL conical flask and dissolved with 25 mL distilled ethanol was added. Two drops of phenolphthalein indicator were added to the flask and titrated to faint pink end point with 0.1 N potassium hydroxide (KOH) (Merck, Germany). Fatty acid composition of the extracted oils was determined as their methyl esters with a slight modification of method stated by Akabr et al. (2009). In this method, few drops of extracted fat were dissolved in petroleum ether in a test tube and methylated by using sodium methoxide (Merck, Germany) in presence of flame. The solution was then diluted with distilled water and allowed to settle for few minutes until a clear portion was visible in the upper part of the tube. The upper layer of fatty acid methyl ester (FAME) was collected and used for GC-analysis. Gas chromatography analysis Fatty acid composition and trans fatty acids were analyzed with Shimadzu GC-14B (Japan) series gas chromatograph equipped with flame ionization detector and fused silica capillary column (FAMEWAX, Crossbondpolyethylene glycol, 15m×0.25mm×0.25µm film thickness, Restek; Pennsylvania, USA). Splitless injection technique with nitrogen as carrier gas at a constant low rate of 20 mL/min was used. Injector temperature was 250^oC, initial oven temperature was 150^oC and held for 5 minutes. Temperature was increased at 8^oC/min to 190^oC and then increased to 200^oC at a rate of 2^oC/min and held for 10 minutes. The fatty acids were identified by using respective fatty acid methyl ester standards (FAME mix; Sigma-Aldrich, St. Louis, Missouri, USA) and presented as relative percentage as done by the automated GC software (Class GC-10; Shimadzu; Japan). Statistical analysis The results presented are mean ± standard deviation obtained from the analysis of three samples. The difference between the mean value of the parameters were obtained by One-way analysis of variance (ANOVA) using SPSS 16.0 (SPSS 2007, SPSS for Windows, Chicago, Illinois, USA) statistically significant differences were reported at (P<0.05).

Source of Information: Bangladesh J. Sci. Ind. Res. 53(2), 117-124, 2018

Article Link (Online Journal): DOI: http://dx.doi.org/10.3329/bjsir.v53i2.36672

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Fatty acid composition showed that the frying medium of 60% of the French fries were palm oil and for 40% case, the medium was soybean oil. No significant difference has found among the three different price groups for free fatty acid (FFA) color value, saturated fatty acid (SFA), mono unsaturated fatty acid (MUFA), poly unsaturated fatty acid (PUFA) and trans fat. peroxide value (PV) of oils extracted from high cost shops’ French fries is significantly lower than low cost and medium cost shops’ French fries.

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