Salviano Santos V., Silva L., Salgado A., Pereira K., 2013, Application of Agaricus bisporus Extract for Benzoate Sodium Detection Based on Tyrosinase Inhibition for Biosensor Development, Chemical Engineering Transactions, 32, 1831-1836.
Sodium benzoate preservative is widely used in foods and beverages. Considering the possible adverse reactions described in the literature (child hyperactivity, asthma, urticaria), there is an importance for stringent control of sodium benzoate levels in order to maintain food quality and guarantee safety for consumers. Accordingly the need for analytical methods which are quick and affordable. Nowadays, the HPLC (High-performance liquid chromatography) is the official method used for the detection and quantification of these preservatives. However, the chromatographic technique has some limitations such as the need for pretreatment of the sample and the need for highly skilled operators to perform analyses. Biosensor development may offer advantages in comparison to conventional detection techniques. The assays described here aim to validate the method of detection and quantification of sodium benzoate and will be applied in future construction of a biosensor designed to detect benzoates in food samples. The principle of the method is based on the measurement of the inhibition of tyrosinase enzymatic activity with the substrate L-tyrosine of the sodium benzoate present in samples of beverages. The concentration of the preservative is quantitatively related to the percent inhibition experienced by the enzyme. The tests were conducted using an oxygen electrode as transducer; measuring its consumption during the enzymatic reaction in the presence of the substrate. The source used was the tyrosinase enzyme extract obtained from macrofungi Agaricus bisporus, having enzymatic activity as determined by colorimetric method of 372 U/mL to 937 U/mL. The proportions of enzyme/substrate obtained were determined as the best ones: neat extract/solution of 1 mM L-tyrosine or extract diluted 1:1 in a buffer solution of sodium phosphate pH 6 of L-tyrosine 1.2 mM. A standard curve showed linearity of enzyme inhibition of 0.006 g to 0.014 g sodium benzoate. Tests with real samples indicated the presence of sodium benzoate below those permitted by Brazilian Law in samples of natural guaraná soft drink.
