Determination of Benzoic Acid in Commercial Fermented Soybean Pastes via Ultraviolet-Visible Spectroscopy (UV-Vis) and Reversed-Phase High Performance Liquid Chromatography (RP-HPLC) Methods

Ben, Zhu Ying (2018) Determination of Benzoic Acid in Commercial Fermented Soybean Pastes via Ultraviolet-Visible Spectroscopy (UV-Vis) and Reversed-Phase High Performance Liquid Chromatography (RP-HPLC) Methods. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Fermented soybean paste is a product which undergone brine fermentation by Aspergillus species and commonly preserved by sodium benzoate owing to its outstanding water solubility property. However, the permitted usage level of sodium benzoate (calculated as benzoic acid) is 1000mg/kg, according to Malaysian Food Act 1983 and Regulations. Studies (WHO, 2000) had shown that test group who were subjected to oral challenge with benzoic acid and sodium benzoate experienced urticarial, asthma and dermatitis. Hence, the use of benzoic acid and sodium benzoate must be strictly controlled. Currently, there are various methods used to determine benzoic acid in different type of food matrices. In this study, the amount of benzoic acid exists in fermented soybean paste was examined by using Ultraviolet-Visible Spectroscopy (UV-Vis) and Reversed-Phase High Performance Liquid Chromatography (RP-HPLC) method. The objectives are: i) to compare these two methods; ii) to measure the concentration of benzoic acid present in commercial fermented soybean paste samples. Linearity, accuracy, precision and sensitivity had been investigated. Benzoic acid was extracted with chloroform and HPLC grade methanol. In this study, benzoic acid in different samples were analysed using UV-Vis at wavelength 272nm and RP-HPLC equipped with Diode Array detector, C18 column was used as stationary phase while ammonium acetate buffer (pH 4.4) and HPLC grade methanol acted as mobile phase. The linear correlation coefficient of benzoic acid calibration graphs were more than 0.9. Besides, the LOD and LOQ for benzoic acid were 0.3737ppm and 1.1324ppm, respectively. A result of more than 90% of recovery in every sample signified high accuracy of extraction method. High reproducibility of results denoted by relative standard deviation, lower than 5%. In conclusion, benzoic acid were detected in all samples with concentration ranging from 315ppm to 734ppm in all five commercial products were within the regulated boundary.