  A rich inventory of complex organic molecules (COMs) has been observed in
high abundances in the gas phase toward Class 0 protostars. These molecules are
suggested to be formed in ices and sublimate in the warm inner envelope close
to the protostar. However, only the most abundant COM, methanol (CH3OH), has
been firmly detected in ices before the era of James Webb Space Telescope
(JWST). Now it is possible to detect the interstellar ices of other COMs and
constrain their ice column densities quantitatively. We aim to determine the
column densities of several oxygen-bearing COMs (O-COMs) in both gas and ice
for two low-mass protostellar sources, NGC 1333 IRAS 2A and B1-c, as case
studies in our JWST Observations of Young protoStars (JOYS+) program. By
comparing the column density ratios w.r.t. CH3OH between both phases measured
in the same sources, we can probe into the evolution of COMs from ice to gas in
the early stages of star formation. We are able to fit the fingerprints range
of COM ices between 6.8 and 8.8 um in the JWST/MIRI-MRS spectra of B1-c using
similar components as recently used for IRAS 2A. We claim detection of CH4,
OCN-, HCOO-, HCOOH, CH3CHO, C2H5OH, CH3OCH3, CH3OCHO, and CH3COCH3 in B1-c, and
upper limits are estimated for SO2, CH3COOH, and CH3CN. The comparison of O-COM
ratios w.r.t CH3OH between ice and gas shows two different cases. 1) the column
density ratios of CH3OCHO and CH3OCH3 match well between the two phases, which
may be attributed to a direct inheritance from ice to gas or strong chemical
links with CH3OH. 2) the ice ratios of CH3CHO and C2H5OH w.r.t. CH3OH are
higher than the gas ratios by 1-2 orders of magnitudes. This difference can be
explained by the gas-phase reprocessing following sublimation, or different
spatial distributions of COMs in the envelope.
