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

Abstract

Unground triticale kernels contaminated with 6.63mg deoxynivalenol (DON) per kg dry matter were stored for up to 63days 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 5g Na2S2O5 (SBS) per kg], and in the absence and presence of 10g 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 ≥3g/kg. Lower SBS concentrations yielded inconsistent results. The maximum measured DON reductions after adding 5g SBS/kg were 3 and 4% of the initial DON concentration after 63days 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 5g/kg triticale at a moisture content of 15% preserved for 63days 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.