Rapid prediction of ochratoxin A producing strains of Penicillium on dry cured meat by MOS based electronic nose.
The availability of rapid diagnostic methods for monitoring ochratoxigenic species during the seasoning processes for dry cured meats is crucial and constitutes a key stage in order to prevent the risk of ochratoxin A (OTA) contamination. A rapid, easy to perform and non invasive method using an electronic nose (e nose) based on metal oxide semiconductors (MOS) was developed to discriminate dry cured meat samples in two classes based on the fungal contamination: class P (samples contaminated by OTA producing Penicillium strains) and class NP (samples contaminated by OTA non producing Penicillium strains) Two OTA producing strains of Penicillium nordicum and two OTA non producing strains of Penicillium nalgiovense and Penicillium salamii, were tested. The feasibility of this approach was initially evaluated by e nose analysis of 480 samples of both Yeast extract sucrose (YES) and meat based agar media inoculated with the tested Penicillium strains and incubated up to 14 days. The high recognition percentages (higher than 82% obtained by Discriminant Function Analysis (DFA) either in calibration and cross validation (leave more out approach) for both YES and meat based samples demonstrated the validity of the used approach. The e nose method was subsequently developed and validated for the analysis of dry cured meat samples. A total of 240 e nose analyses were carried out using inoculated sausages, seasoned by a laboratory scale process and sampled at 5, 7, 10 and 14 days. DFA provided calibration models that permitted discrimination of dry cured meat samples after only 5 days of seasoning with mean recognition percentages in calibration and cross validation of 98 and 88% respectively. A further validation of the developed e nose method was performed using 60 dry cured meat samples produced by an industrial scale seasoning process showing a total recognition percentage of 73% The pattern of volatile compounds of dry cured meat samples was identified and characterized by a developed HS SPME/GC MS method. Seven volatile compounds (2 methyl 1 butanol, octane, 1R a pinene, d limonene, undecane, tetradecanal, 9 (Z) octadecenoic acid methyl ester) allowed discrimination between dry cured meat samples of classes P and NP. These results demonstrate that MOS based electronic nose can be a useful tool for a rapid screening in preventing OTA contamination in the cured meat supply chain.
International journal of food microbiology