Methanol is an ubiquitous complex organic molecule (COM) in the interstellar medium, thought to be a precursor of larger COMs when it is submitted to different energetic processes, that can trigger chemical reactions in solid and gas phases. Using laboratory experiments, we report the characterization of the evolution of photo-products generated by the UV irradiation of methanol ice at different UV doses and temperatures (20 and 80 K). We used gas chromatography coupled to mass spectrometry (GC-MS) to analyze the volatile organic compounds (VOCs) recovered during the warming of the photo-processed methanol ice. We identified 21 molecules (with up to 5 carbon atoms, including alcohols, aldehydes, ketones, ester and ethers) and followed their abundance as a function of the UV fluence and ice temperatures. With increasing UV fluence, an increase in the production of heavier COMs is observed, while species with 1 or 2 carbon atoms are depleted or do not increase. Species within a same chemical family show the same pattern of evolution, with heavier molecules present in smaller quantities. Ketones and esters are the chemical families that lead to more complex molecules and start forming at the earliest stages of irradiation. Their formation pathways are driven by radical recombinations with CO as the main building blocks. Aldehydes are formed before their alcohol counterparts, implying they do not form through alcohol deshydrogenation, but via radical recombination around HCO. Ethers seem to be the precursors of a large set of COMs, and alcohols present a steady profile throughout irradiation.