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Complex organic molecules (COMs) are often observed toward embedded Class 0and I protostars. However, not all Class 0 and I protostars exhibit COMsemission. In this work, variations in methanol (CH$_3$OH) emission are studiedto test if absence of CH$_3$OH emission can be linked to source properties.Combining both new and archival observations with ALMA and sources from theliterature, a sample of 184 low-mass and high-mass protostars is investigated.The warm (T > 100 K) gaseous CH$_3$OH mass, $M_{\rm CH_3OH}$, is determined foreach source using primarily optically thin isotopologues. On average, Class Iprotostellar systems seem to have less warm $M_{\rm CH_3OH}$ ($<10^{-10}$M$_\odot$) than younger Class 0 sources ($\sim10^{-7}$ M$_\odot$). High-masssources in our sample show higher warm $M_{\rm CH_3OH}$ up to $10^{-7}-10^{-3}$M$_\odot$. To take into account the effect of the source's overall mass on$M_{\rm CH_3OH}$, a normalized CH$_3$OH mass is defined as $M_{\rmCH_3OH}/M_{\rm dust,0}$, where $M_{\rm dust,0}$ is the cold + warm dust masswithin a fixed radius. Excluding upper limits, a simple power-law fit to thenormalized warm CH$_3$OH masses results in $M_{\rm CH_3OH}/M_{\rmdust,0}\propto L_{\rm bol}^{0.70\pm0.05}$. This is in good agreement with asimple hot core toy model which predicts that the normalized $M_{\rm CH_3OH}$increases with $L_{\rm bol}^{0.75}$ due to the snowline moving outward. Sourcesfor which the size of the disk is equivalent or smaller than the estimated 100K radius agree well with the best-fit power-law model, whereas sources withsignificantly larger disks show up to two orders of magnitude lower normalizedwarm CH$_3$OH masses. Based on the latter results, we suggest that sourcestructure such as a disk can result in colder gas and thus fewer COMs in thegas phase. Additionally, optically thick dust can hide the emission of COMs.

Importance of source structure on complex organics emission. I. Observations of CH$_3$OH from low-mass to high-mass protostars