The effect of applicationof MIRD before freeze drying (MIRD–FD) and after freeze drying (FD–MIRD) on drying time,
color,
rehydration ratio,
apparent density,
microstructure and aroma compounds was measured,explained and compared with the effect of FD on these parameters.The results showed that the combination of FD (for 4 h) followed by MIRD saves 48% timecompared to FD while keeping the product quality at an acceptable level.
The MIRD–FD combination was found to beinferior compared to the FD–MIRD as the former tended to produce products with a collapsed surface layer and poorrehydration capability.
The combination of MIRD with FD had a significant effect on aroma retention and caused anincrease of sulfur compounds such as dimethyl, trisulfide and 1,2,4-trithiolane.