Fruit waste is a potential feedstock for biogas prodn. However, the presence of fruit flavors that have antimicrobial activity is a challenge for biogas prodn. Lactones, ketones, and phenolic compds. are among the several groups of fruit flavors that are present in many fruits. This work aimed to investigate the effects of two lactones, i.e., γ-hexalactone and γ-decalactone; two ketones, i.e., furaneol and mesifurane; and two phenolic compds., i.e., quercetin and epicatechin on anaerobic digestion with a focus on methane prodn., biogas compn., and metabolic intermediates. Anaerobic digestion was performed in a batch glass digester incubated at 55 °C for 30 days. The flavor compds. were added at concns. of 0.05, 0.5, and 5 g/L. The results show that the addn. of γ-decalactone, quercetin, and epicathechin in the range of 0.5-5 g/L reduced the methane prodn. by 50 % (MIC50). Methane content was reduced by 90 % with the addn. of 5 g/L of γ-decalactone, quercetin, and epicathechin. Accumulation of acetic acid, together with an increase in carbon dioxide prodn., was obsd. On the contrary, γ-hexalactone, furaneol, and mesifurane increased the methane prodn. by 83-132 % at a concn. of 5 g/L. [on SciFinder(R)]