Longitudinal study on the sulphur dioxide residues on daylilies treated with sodium metabisulfite and sulphur

In order to ensure the security of daylilies treated by sulphur,the sulphur dioxide residues treated by sodium metabisulfite and sulphur were tested during the process of storage,rehydration and cooking,respectively.The sulphur dioxide residue on daylilies treated by sodium metabisulfite solution was under 100 mg/kg after 90 days′storage,and it decreased to 32.3-50.6 mg/kg after rehydration of 60 min,then to 20.80-40.00 mg/kg after cooking.The sulphur dioxide residue on daylilies treated by the concentration of 0.5 g/kg was under 200 mg/kg,and decreased to 114-187 mg/kg after rehydration of 60 min.The sulphur dioxide residue on daylilies treated by sodium metabisulfite powder was still higher than 200 mg/kg after 150 days′storage and 120 mins′rehydration.The results showed that the sulphur dioxide residues of daylily following treatment with sodium metabisulfite solution(≤10 g/L) and sulphur(≤0.5 g/kg) was within safe boundaries.