Product shrinkage was evident in all test runs, but the extent was somewhat
dependent on the severity of microwave application, being minimal at the
highest power level (PL 4) and maximum with no microwave heating (PL 0).
The COR and the rehydration ratio (RR) calculated from rehydration tests
are summarized in Table 2. Rehydration properties were improved by drying at
higher power levels as indicated by higher values of COR and RR. Similar
results were reported by Jeppson ( 1964) and Nury and Salunkhe ( 1968) for
drying of apples. The rehydration process, however, was not complete in the 5
min cooking process employed as shown by the low RR values. The available
quantity of dried samples was insufficient to carry out additional rehydration
tests (with longer cooking times). Although test samples were not fully reconsti-
tuted, visual observation of the rehydrated product revealed that samples dried
at PL 0 and 2 retained good colour, while those dried at PL 4 were dull. Thus PL
2 appears to be the best compromise, with good rehydration and appearance
characteristics and moderate drying rates.