Fermentation, one of the oldest and most prevalent methods of food preservation, is often regarded as a preliminary phase of digestion wherein microorganisms transform basic meals into “new foods” with unique organoleptic characteristics (Jeyaram et al., 2025). Fermented foods can be categorically classed as fruit and vegetable items, dairy products, meat products, cereal products, and aquatic products depending on their constituent composition. Fish sauce is a clear, amber-hued liquid condiment characterised by a distinctive salty and umami flavor. It is generally produced from low-cost seafood (anchovies) that have had an extensive fermentation process (Russo, Langellotti, Genovese, Martello, & Sacchi, 2020). As the predominant fermented aquatic product in South-east Asia, it is gaining popularity among customers in other nations due to its delectable flavor and smooth texture (Kim et al., 2016). Traditionally, fish sauce is produced by marinating raw ingredients in a high salt concentration and sealing them for a duration of 6 to 24 months or longer (Lapsongphon, Cadwallader, Rodtong, & Yongsawatdigul, 2013) (Lapsongphon, Yongsawatdigul, & Cadwallader, 2015). This process utilises the enzymatic system inherent to the fish and the saline microorganisms present in the environment to gradually decompose nutrients such as proteins and lipids in the raw materials, resulting in the distinctive salty and fresh flavor characteristic of fish sauce (Du, Zhang, Gu, Song, & Gao, 2019). Nevertheless, fish sauce produced via traditional methods is susceptible to microbial contamination during fermentation, necessitating the addition of a high salt concentration to inhibit or eradicate spoilage bacteria, with salt levels potentially reaching approximately 30 %. Such elevated salt content contradicts contemporary dietary principles, and an extended fermentation period significantly diminishes the efficiency of fish sauce production.

To generate a substantial quantity of high-quality fish sauce, individuals have identified the quick-brewing procedure, which primarily encompasses heat preservation fermentation, enzyme fermentation, and inoculation fermentation methods. The idea of holding fermentation posits that elevated fermentation temperatures can expedite the rate of protein hydrolysis, hence facilitating the Maillard reaction; Tian et al. (Tian, Gao, Xu, Xia, & Jiang, 2021) discovered that elevated fermentation temperatures enhanced the accumulation of flavor compounds in fermented bream (Parabramis pekinensis); however, prolonged fermentation is unsuitable for extended durations, as it results in rancid odours and incurs high costs. The principle of additive enzyme fermentation is to enhance the rate of protein breakdown through the introduction of exogenous enzymes or enzyme-rich visceral tissues. Aquerreta et al. (Aquerreta, Astiasarán, & Bello, 2002) markedly decreased the fermentation duration of garum through the incorporation of neutral protease; yet, the fish sauce generated via enzyme-assisted fermentation exhibited an inferior flavor profile and a subtle bitterness. The inoculation fermentation method primarily involves introducing microorganisms into the fermentation slurry, utilizing their protease, lipase, and amylase producing capabilities to thoroughly deconstruct the proteins, fats, and carbohydrates present in the raw fish, thereby significantly reducing the fermentation duration. The predominant inoculation microorganism is Aspergillus oryzae. Zhao et al. (Zhao, Jiang, Xu, & Xia, 2017) discovered that the sweet and caramel notes in fish sauce generated through inoculated fermentation were markedly enhanced, whereas the ammonia and acidic flavors were considerably diminished; however, a drawback is that if the inoculated microorganisms are not pre-acclimated to elevated salt concentrations, they may experience substantial mortality due to “salt shock,” thereby significantly extending the fermentation duration.

Climate change, biodiversity loss, land degradation, and freshwater resource depletion will result in substantial alterations to the global food system (Diaz & Rosenberg, 2008); amid global population growth and climate change, food scarcity is intensifying, and conventional agriculture is encountering constraints in land and water resources. Marine food, as an underutilised resource, presents a novel avenue to mitigate the food crisis. Fish and fishery products are significant components of global cuisine (Love et al., 2023) (Golden, 2025) (Naylor et al., 2021). The fish processing business has been advancing swiftly due to ongoing enhancements in processing technology and equipment; yet, 50 %–60 % of by-products are produced during the processing phase. Most by-products, including fish heads, bones, and skins, can be converted into fishmeal, fish oil, or low-value animal feeds; nevertheless, fish offal is typically discarded due to inadequate processing, resulting in significant waste of protein and fat resources and contributing to environmental contamination. Metabolomics technology analyzes changes in metabolite content and their biological characteristics to enable high-throughput, high-precision, and quantitative study on metabolites (Liu & Locasale, 2017). The study of numerous fermented foods, including pickle (Tomita, Nakamura, & Okada, 2018), green tea (Z. Han et al., 2022), baijiu (Song et al., 2020), soy sauce (Kamal et al., 2022), etc., has made extensive use of metabolomics technology in recent years.

This study concentrated on the utilisation of fish offal waste, employing domesticated Aspergillus strains resistant to high salinity and nitrogen as fermentation agents. The combined application of extra-enzymatic and inoculation fermentation methods not only significantly reduces fermentation time and mitigates resource wastage but also enhances the flavor of fish sauce. By integrating free amino acids, gas chromatography-ion mobility spectrometry (GC-IMS), electronic nose, electronic tongue, and metabolomics to investigate the unique flavor compounds and essential metabolic pathways during fermentation, we can achieve a synergy between marine food and food security centred on sustainable development, while preserving marine ecological resilience for the scientific management of marine resources, thereby offering mutually beneficial solutions for humanity's sustainable advancement.