Sterigmatocystin Occurrence in Paddy and Processed Rice Produced in Italy in the Years 2014–2015 and Distribution in Milled Rice Fractions

Terenzio Bertuzzi,Silvia Rastelli,Annalisa Mulazzi,Amedeo Pietri,Marco Romani

doi:10.3390/toxins9030086

Abstract

The occurrence of sterigmatocystin (STC) in paddy and processed rice samples produced in Italy was surveyed. After extraction and purification, STC was analysed using HPLC-MS/MS. STC was detected in all paddy rice samples (n = 49), in the range 0.29–15.85 μg·kg−1. As regards processed rice, a widespread contamination was found in brown and parboiled rice. All the brown rice samples were contaminated between 0.12 and 1.32 μg·kg−1; for parboiled rice, the incidence was 90.9% and the maximum level was 1.09 μg·kg−1. The contamination in white rice was significantly lower (p < 0.01). The STC distribution in different rice fractions, obtained by the de-hulling and polishing processes, was evaluated. After de-hulling, the STC percentage remaining in brown rice was in the range 21.2%–30.8%. The polishing process, from brown to white rice, caused another remarkable decrease of contamination; the STC remaining in white rice was 2.2%–8.3% of the amount found in paddy rice.

Highlights

Sterigmatocystin (STC) is a mycotoxin produced by fungi of the genus Aspergillus as well as by other species belonging to the genera Bipolaris, Chaetomium and Emiricella; A. versicolor is the most common source in food
For the samples falling between limit of detection (LOD) and limit of quantification (LOQ), we tentatively calculated the value by proportion with the lowest calibration standard
As regards paddy rice samples, STC was detected in all samples in the range of 0.29–15.85 μg·kg−1

Summary

Introduction

Sterigmatocystin (STC) is a mycotoxin produced by fungi of the genus Aspergillus (mainlyA. nidulans and A. versicolor) as well as by other species belonging to the genera Bipolaris, Chaetomium and Emiricella; A. versicolor is the most common source in food. Food commodities infested by these fungi can contain high amounts of STC; on the contrary, infestation by A. flavus and A. parasiticus can cause low amounts of STC, because most is converted into aflatoxins [1,2,3]. STC has an aflatoxin-like structure including a furofuran ring system; in several studies STC was recognised as a potential carcinogen, mutagen and teratogen in animals [4,5,6,7]. Recent studies showed that STC forms DNA adducts after metabolic activation to an epoxide at the furofuran ring [9] and is more genotoxic than AFB1 in three types of human cell lines [10]. European legislation has no fixed limits for STC occurrence in food; only the

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