Metam Sodium (MS) in Water and Cane Juice at Different Processing Conditions According to the Industrial Case. Part 1. Effects of Matrix, pH, Temperature, Processing Time, and Photolysis

Abstract

The process for extracting sugarcane juice (Saccharum officinarum) represents the point of greatest contamination in sugarcane mills. Sodium dithiocarbamate also known as metam-sodium or MS is added to inhibit the growth of microorganisms especially Leuconostoc mesenteroides which is responsible for forming polysaccharides. Metam-sodium, upon decomposition, produces highly toxic byproducts. According to literature, under acidic conditions, MS is hydrolyzed resulting in methylamine (MA), CH₃NH₂, and carbon disulfide (CS₂), and in dilute alkaline solutions, MS produces an oxidation reaction characterized by the formation of elemental sulfur (S) and methyl isothiocyanate (MITC). In this paper, it was studied how MS decomposes to MITC and/or MA considering the effects of the matrix (methanol and water); of temperature (4 and 25 °C); of processing time (0, 1, 2, 3, 4 days); and of pH (4.0, 4.5, 7.0). A second experimental design considering the effects of the matrix (water and sugarcane juice); of temperature (4, 25, 35, 45 °C); of processing time (30, 300 min); and of pH (4.0, 4.5, 7.0) was derived from the results obtained considering MITC and/or MA formation. According to the statistical analysis of these results (p < 0.05), the order of the influential factors was as follows: time > matrix > pH > temperature. Results also indicated that the water matrix at pH = 4.5 and 45 °C had the lowest degradation rate (k), with a value of 8.82 day⁻¹, while for the sugarcane juice matrix at the same pH and temperature conditions was larger, with a k value of 30.07 day⁻¹. These results show that the matrix is also important for the degradation of dithiocarbamate to MITC and to MA.

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