Effects of Different Thermal Processing Methods on the Physicochemical Properties, Volatile Flavor Substances and Sensory Quality of Crayfish Hepatopancreas

This study investigated the effects of three common thermal processing methods (boiling, steaming, and frying) on the color, nutritional composition, fatty acid profile, volatile base nitrogen (TVB-N), and fat oxidation of crayfish hepatopancreas. Electronic tongue, electronic nose, and gas chromatography-ion mobility spectrometry (GC-IMS) techniques combined with sensory evaluation were applied to evaluate the effects of different thermal processing methods on the physicochemical properties, volatile flavor substances, and sensory quality of crayfish hepatopancreas. The results revealed that, in comparison to fresh hepatopancreas, significant changes in physicochemical properties and volatile flavor compounds were observed after undergoing these three distinct thermal processing methods, with notable variations among the groups. The redness (a^*), yellowness (b^*), and brightness (L^*) values of crayfish hepatopancreas in thermal processing groups were increased, and the frying group was the most significant. Total fatty acids and major fatty acid components decreased, most prominently in the frying group. The steaming group demonstrated better preservation of EPA+DHA. TVB-N and thiobarbituric acid reactive substances (TBARS) were increased, especially in the frying group. Electronic tongue analysis revealed that a prominent umami taste with a hint of saltiness was prevalent in all thermally processed hepatopancreas. Electronic nose analysis showed noticeable differences in aroma characteristics before and after thermal processing, with the frying group displaying the most significant changes. A total of 28 volatile substances were identified by GC-IMS. The number and content of substances were mainly aldehydes and esters. The content of volatile substances in the frying group was the highest, followed by the steaming group, and the boiling group was the least. Sensory evaluations indicated that the frying group with higher aroma, color, and taste scores got the highest overall rating score, and the boiling and steaming groups scored slightly lower and were close. Therefore, the boiling group exhibited the lowest degree of oxidative changes due to heat treatment and retained more characteristics of fresh samples, and the frying group experienced the highest level of heat-induced oxidative changes, resulting in the richest flavor profile and a higher degree of popularity. This research provides valuable insights for optimizing crayfish processing in the industry.