Effects of three types of modified atmospheric packaging on the physicochemical properties of selected glutinous rice

The effect of modified atmospheric packaging (MAP) on the physicochemical properties of selected glutinous (Thadokkham-8 and Thadokkham-11) rice was studied and compared with a non-glutinous rice (Doongara). The freshly harvested/milled grains were packed in four different MAP conditions viz. control, vacuum, CO2 and N2 for 12 months at room temperature (23 ± 1 °C). Gas (N2 or CO2) was flushed in aluminum bags at the pressure of 300 kPa for 3 s and subsequently hermetically sealed. Vacuum packaging was done at −100 kPa. Results showed that ageing induced changes in the starch granules were less prominent in vacuum and/or MAP samples using CO2 or N2. Surface analysis showed that control storage significantly reduced the percentage of lipids and increased the percentage of proteins on the surface in all selected varieties. N2 and CO2 storage of TDK8 and DG slowed down the shift of properties of macromolecules and maintained the surface starch/proteins/lipids ratios during 6 months of storage. Moreover, the grains stored in vacuum maintained the lipids with lower proportion of proteins exposed to the surface after cooking. N2 and CO2 induced increase in pasting temperature but significant reduction in final viscosity when compared to control. The findings correlated well with thermal analysis. The in situ Thermal Mechanical Compression Test (TMCT) device cooking and texture analysis revealed that modified storage slightly slowed the ageing induced changes in the cooking quality and stickiness of glutinous rice. Among all storage conditions used vacuum was relatively the best to maintain the quality of the grain.