Abstract
The kinetics of pectin reactions in apple pomace were modelled preparatory to developing a time-temperature operating map for quantity and quality of solubilized pectin and other reactions in apple pomace. This graph can be used for selecting suitable time-temperature conditions for hydrothermal treatments to ensure a safe product with expected quality. Kinetics were measured for the major reactions in apple pomace heated at 90–140 °C for 0–210 min, in particular for the solubilization and depolymerization reactions of pectin. Maximum levels of soluble pectin (~ 605 μmol galacturonic acid/g dry pomace) were observed when heating pomace (diluted 1:2) at 130 and 140 °C for 15 and 7 min, respectively. Acid hydrolysis and β-elimination reactions showed temperature-dependent behaviour, with activation energies of 81 and 65 kJ/mol, respectively. Heating at temperatures ≥ 110 °C resulted in degradation of soluble pectin into ethanol-soluble galacturonic acid. Depolymerization reactions of pectin occurred at non-esterified sites within the pectin polymers, as suggested by the high degree of esterification of the remaining insoluble pectin.
Published Version
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