An Assessment of Pectin Thiolation parameters: Degree of Esterification, Conjugate and Cross-linking Reagent Concentrations

Abstract

This study focuses on the optimisation of pectinthiolation using L-cysteine and assesses the impact of the degree ofesterification (DE), polymer to L-cysteine ratio, and concentrations ofconjugating reagents on the total and free thiol content of both highlyesterified (HE) (>50% esterified) and lowly esterified (LE) (<50%esterified) pectin thiomers. The thiolation process was analysed undervariations of four factors - the type of pectin used (HE and LE), the polymer tocysteine ratio, and concentrations of the conjugating reagents 1-(3-dimethylaminopropyl)-3-ethylcarbodiimidehydrochloride (EDAC) and N-hydroxysuccinamide (NHS) (0 mM, 25 mM, 50 mM &100 mM). Thiol content was determined using Ellman’s reagent, withspectrophotometric methods. Statistical analysis via multivariant analysis of variation(MANOVA) indicates a significant relationship with respect to total thiolcontent considering DE, polymer to cysteine ratio, and EDAC concentration(P<0.05). Concordantly, MANOVA indicated a significant relationship withrespect to free thiol content considering DE, polymer to cysteine ratio, andboth EDAC and NHS concentrations (P<0.05). Increasing EDAC concentrationcorresponded with increased total and free thiol content in both types ofpectin. In contrast, elevating NHS concentration led to reduced total thiolcontent across most ratios. Thus, the study delineates critical parameters inthe thiolation of pectin using L-cysteine.