Intense pulsed light treatment for enhancing the storage stability of sorghum flour: lipase inactivation kinetics, fatty acid changes, and shelf-life prediction

Abstract

This study aimed to investigate the impact of intense pulsed light (PL) treatment as a novel post-harvest intervention to enhance the shelf-life stability of sorghum flour. The lipase inactivation kinetics was studied over a varying range of pulse fluence (5-30 J/cm²), and kinetic modelling was performed. During storage period of 120 days, moisture content, water activity, pH, colour parameters, lipase activity (LA), and free fatty acids (FFAs) were analysed for flour samples from whole and polished grains (treated and untreated) stored at both ambient (27 ± 1 °C, 65% RH) and accelerated (40 ± 1 °C, 90% RH) conditions. A comprehensive fatty acid profiling was done, followed by shelf-life prediction using zero-order kinetics. Results indicated a significant reduction in LA following PL treatment, with an IC50 fluence of 25.31 J/cm², representing the fluence required to inhibit LA by 50%. The fractional conversion model best fitted the lipase inactivation kinetics with an R² of 0.998. After 120 days of ambient storage, the flour from polished and PL-treated grains exhibited superior shelf-life properties, showing 35% lower FFA content and 53% lower LA compared to flour from whole-untreated grains. Additionally, this flour exhibited the lowest zero-order reaction rate constants for both FFA and LA under ambient and accelerated storage conditions. Fatty acid profiling showed positive changes in saturated and monounsaturated fatty acids, with less significant changes in polyunsaturated fatty acids in this sample. These findings suggest that intense PL can be an effective, non-thermal post-harvest intervention to extend the shelf-life of sorghum flour.