OFF-FLAVOR MITIGATION IN ATLANTIC SALMON GROWN IN RAS VIA THE USE OF A NOVEL SINGLE CELL PROTEIN BASED FEED

While a major world consumer of seafood by volume, the United States' domestic seafood production is limited. As a result, 90% of the seafood consumed in the US is imported, and the seafood trade deficit has grown to $14 billion in 2016 - second only to oil. Aquaculture will play a major role in meeting the ever-growing demand for seafood, and specifically in the United States, many of these production facilities will be land-based or recirculating aquaculture systems (RAS). The first of several large commercial RAS facilities are coming online and are poised to play a key role in reducing the seafood trade deficit. Advantages of RAS include reduced water usage & waste discharge, controlled environment, no escape risk. The flexibility to locate RAS near major markets reduces carbon footprints associated with shipping and provides more stability along the supply chain given the Covid-19 pandemic era. However, RAS facilities face challenges including 1) off-flavor mitigation, and 2) sourcing high quality fish feed. Off-flavors are mostly associated with the compounds geosmin (GSM) and 2-methylisoborneol (MIB), imparting a muddy and/or musty taste to the fillet. The human senses of taste and smell can detect these compounds at very low concentrations, thus modest bioaccumulation is sufficient to taint the final product. While they are non-toxic and do not decrease fish performance, these off-flavors are highly undesirable by the consumer. Off-flavors delay or deny a sale leading to significant economic impact at scale. For these reasons, off-flavors are consistently ranked among top issues facing the RAS industry. According to our internal customer discovery efforts and consistent with peer-reviewed literature, off-flavors are either #1 or #2 biggest issue for RAS production systems. The current consensus indicates that GSM and MIB are water-borne compounds which are primarily absorbed by the fish through the gills. Because of their lipophilic nature, the rates of uptake of GSM or MIB by the fish are much faster than the rates of depuration from the tissues, leading to a bioaccumulation in the body of the animal and the development of an off-flavor perceivable by people. Considering this paradigm, there are two main strategies to mitigate off-flavors in aquaculture fish: 1) Target microorganisms present in the culture environment to control or remove the GSM/MIB producers, 2) Purge animals in a clean system devoid of GSM or MIB. To date, examples of the former have shown only limited effects, and none are used commercially. Additionally, purging fish for off-flavor mitigation is a grossly inefficient process and a significant burden to a farm's viability. Working with a local New England RAS farm, KnipBio and partners anecdotally discovered that one of the KBM flours led to a "cleaner" tasting fish after a growth trial terminated. Although this observation was repeated several times, there is a need to further validate it under a more robust experimental design. Briefly, the technical approach of the proposed proof of concept will directly compare groups of fish fed either a control or a test feed containing 5% KBM. Due to the relevance and scale, Atlantic salmon is preferred in this study. The fish will be housed in an indoor RAS at the industry leading CRO Freshwater Institute, where groups of fish will be randomly assigned either the control or the test feed. The feeding trial will last 8 weeks during which water GSM and MIB concentrations will be routinely monitored. At the 4- and 8- week time points, the fish will be sampled and fillet GSM and MIB will be measured. A sensory panel will be assembled to evaluate taste. Samples from the biofilter and fish tank will be taken to evaluate the system microbiome. Because each tank has its own dedicated, independent water filtration system, we will have replication at the system level. The specific objectives of the proposed Phase I work are as follows: Feed Generation - Produce 55 kg of KBM flour to be used to manufacture 1,100kg of feed (550kg of each formula) necessary to feed 600, 4kg Atlantic salmon for the duration of the study. Feeding Trial - Conduct the feeding trial for 8 weeks with regular sampling of the fish and water. Fish should perform well, with no mortality. Sample analysis - Upon termination of the feeding trial, all samples will be sent to external laboratories for analyses. Sensory panel - An external panel of trained panelists will evaluate the taste of the fish in a double-blind design. Data analysis and reporting - All data will be analyzed with statistical tools appropriate to the nature of the data and experimental design. The results will be interpreted, and a final report produced accordingly.