Hydrothermal pre-treatment (HTP) is considered to be a promising technique which can be used to improve food waste (FW) dewatering performance and biodegradability. It was critical to selecting HTP conditions to optimize protein degradation, transformation and split-phase biogas production during dark fermentation. The results show that as the temperature increased from 80 to 200 degrees C, a noticeable decrease in the proportions of crude protein and amino acids within the solid-phase was found, whilst total volatile fatty acids within the liquid-phase from the FW under HTP increased. The tryptophan and tyrosine proportions were higher than that of the control after HTP, whereas the fulvic acid- and humic acid-like substances simultaneously disappeared. The optimum performance of hydrogen production during the liquid-phase dark fermentation after HTP-III (at 150 degrees C for 60 min with 40% water addition) showed the highest hydrogen production rate and proportion of 15.57 mL/h and 62%, respectively. This contributed to protein hydrolysis and enhancement of the biogas production from FW under HTP. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.