Desenvolvimento de procedimentos analíticos para determinação de formaldeído em cogumelos

Abstract

Formaldehyde is employed as a fungicide, pesticide and disinfectant in food production. However, some types of mushroom, such as shiitake and shimeji, may produce formaldehyde during their growth. Shiitake mushrooms can have formaldehyde at 21–370 􀈝g g−1. A tolerable daily intake (TDI) of 0.15 mg kg-1 body weight per day has been set for formaldehyde consumption by the World Health Organization (WHO 1996). Several methods have been reported for formaldehyde determination in different samples such as air, food, water and wood, with different techniques, for example, spectrophotometry, fluorimetry and chromatography. In this work two procedures for determination of formaldehyde in mushrooms samples (shiitake and shimeji) were developed, both determination involves the reaction with acetylacetone in ammonium acetate medium (Nash reagent, pH 5.5) leading to the formation of 3,5-diacetil-1,4-dihidrolutidin (DDL). Firstly, a multicommuted flow analysis system with spectrophotometric detection were design using solenoid valves controlled by a computer. A linear response was observed from 0.2 – 7.0 mg L-1, with a detection limit of 0.02 mg L-1, (99,7% confidence level) relative standard deviation of 1.08% (n = 15), sampling frequency of 17 samples h-1, consuming 10.9 mg of acetylacetone and 30 mg of ammonium acetate per determination. Secondly, an electroanalytical procedure was developed using square wave voltammetry to determine formaldehyde indirectly by exploring the formation of DDL with glassy carbon electrode. A linear response was observed from 0.4 – 40 mg L-1, with a detection limit of 0.05 mg L-1 (99,7% confidence level), relative standard deviation of 0.71% (n = 10) and consuming 1.56 mg of acetylacetone and 117 mg of ammonium acetate per determination. Both procedures were applied on the analysis of shiitake and shimeji samples after formaldehyde steam distillation with 10 % phosphoric acid. No statistical difference was observed applying the Student t- test paired at 95% of confidence interval for the concentration results obtained with both developed procedures. The results showed that both procedures were selectives and sensitives, simple, fast and reduces waste production when compared to chromatographic procedures that determine this aldehyde in food samples.