Effects of increasing concentrations of sodium metabisulphite (Na2S2O5, SBS) on deoxynivalenol (DON) concentration and microbial spoilage of triticale kernels preserved without and with propionic acid at various moisture contents

Unground triticale kernels contaminated with 6.63 mg deoxynivalenol (DON) per kg dry matter were stored for up to 63 days at total moisture contents of 13 and 15% in order to study the time-dependent kinetics of DON concentration in dependence on graded levels of sodium metabisulfite [0, 1, 2, 3, 4 and 5 g Na2S2O5 (SBS) per kg], and in the absence and presence of 10 g propionic acid (PA) per kg. The DON concentration decreased with increasing amounts of supplemented SBS and with increasing duration of the preservation period in a bi-exponential fashion when SBS addition was ?3 g/kg. Lower SBS concentrations yielded inconsistent results. The maximum measured DON reductions after adding 5 g SBS/kg were 3 and 4% of the initial DON concentration after 63 days in the absence and presence of PA at moisture contents of 15%, while the corresponding recovery for the variants preserved at 13% amounted to 21 and 11%, respectively. The 12 variants preserved without PA supplementation were more frequently contaminated by moulds and yeasts (n = 5) than the corresponding variants stored together with PA (n = 1). The overall results and regressive evaluations do suggest that the highest SBS addition of 5 g/kg triticale at a moisture content of 15% preserved for 63 days would be necessary for a maximum DON reduction. Although PA did not exert a direct decontaminating effect, an additional supplementation together with SBS seemed to be advantageous with regard to the prevention of yeast and mould contamination and favouring the decontamination reaction by the acid milieu.