Kyle Peveto, Watts, Evelyn
Seafood is an important part of the United States and Louisiana economy. According to National Oceanic and Atmospheric Administration (NOAA) 2020 commercial landings, Louisiana ranks second in metric tons of seafood landed and fourth in dollar value in the country. The increasing demand for seafood and its characteristic high perishability make handling, processing and packaging practices key to ensure a high quality to meet consumers’ expectations. Seafood is key in the global economy as it is recognized for its health benefits of high-quality protein, vitamins, minerals and essential amino acids. A total of 1 billion people depend on seafood as a source of protein. However, because of its large unsaturated lipid composition, seafood is known to be highly perishable with a relatively short shelf life. Deterioration of seafood begins immediately upon harvesting and quality depends directly on handling, storage and processing conditions.
While Louisiana seafood is famous countrywide, rapid quality deterioration limits market opportunities for the local industry. The Seafood Quality Laboratory at the LSU AgCenter supports the local industry conducting research activities to help the industry enhance seafood quality, expand shelf life and enhance co-product recovery. The seafood laboratory research work focuses on evaluating different chilling methods, antimicrobials applications, packaging and co-product recovery.
Different technologies have been used to chill seafood. In Louisiana, the most common process utilized is flake ice. In contrast, slurry ice is an innovative chilling system prepared from marine water that can reach subzero temperatures, which provides a good application to store aquatic food products compared to flake ice or refrigerated seawater. It reduces physical damage, limits microbial growth and increases shelf life. Research conducted at the seafood lab found that the use of a nano-size slurry ice allows for faster cooling rates compared to flake ice currently used by the seafood industry. This nano-size slurry ice allows the storage of whole fish for a longer period compared to flake ice. In addition, the application of organic acid enhanced the nano-size ice slurry in the chilling step delayed bacterial growth. Furthermore, a study evaluating crawfish shelf life using lactic acid during the chilling step after cooking expanded crawfish tail meat microbial stability from 10 to 12 days. Charts and graphs further explaining research results can be viewed at https://www.lsuagcenter.com/portals/communications/publications/agmag.
In addition to using processing interventions to improve seafood shelf life, packaging also plays an important role in protecting the product to preserve quality and safety. Thus, the primary functions of packaging can be defined as containment, protection, convenience and communication. Development of packaging technologies and materials is extensive. A large variety of packaging materials and technologies exist now that allow for a better quality and a convenient product. Modified atmosphere packaging (MAP) is a technology widely used in meat and poultry products; however, in recent years, market trends are demanding this technology application in seafood products. The seafood lab completed a study evaluating the shelf life and quality of black drum comparing three different packaging technologies and comparing two MAP gas combinations and their effect on shelf life. Microbial growth was reduced in fish stored in MAP at refrigeration temperature for up to 20 days. No difference was observed between different MAP gas combinations.
The seafood lab is currently evaluating the effect of gelatin extracted from fish skin in the shelf life of different seafood products. Gelatin is being enhanced with different antimicrobials and applied as an edible film. Research is still ongoing, but some promising results have been observed in the extension of shelf life.
Findings from research completed at the LSU AgCenter Seafood Quality Laboratory allow the local industry to implement technologies available in the market to enhance the shelf life of their product, meeting consumers’ expectations and being able to market to a regional and national level.
Evelyn Watts is a seafood extension specialist for the LSU AgCenter and Louisiana Sea Grant.
(This article appears in the spring 2022 issue of Louisiana Agriculture magazine.)
Figure 1: Cooling curves of black drum fish stored in a 2:1 ice-to-fish ration. Handling technique abbreviations: PDSI — Pre-drained with nano-sized slurry ice; CDSI — Continuous drain with nano-sized slurry ice; RSI — Retention of meltwater with nano-sized slurry ice; RFI — Retention of meltwater with flake ice.
Figure 2: Psychrophilic count (Log CFU/g) during 18-day shelf life of black drum comparing flake (F) and nano-sized slurry ice (N). The orange line indicates the recommended limit (Log CFU/g=logarithmic colony forming units per gram).
Figure 5: Aerobic plate counts (APC) during the black drum 20-day shelf-life study comparing different packaging methods: air packed (AP), vacuum packed (VP), modified packaging (MAP), 50% nitrogen and 50% carbon dioxide (NC), and MAP 30% nitrogen, 40% carbon dioxide, and 30% oxygen (NCO). The orange line indicates the recommended limit (Log CFU/g=logarithmic colony forming units per gram).
Former students Katheryn Parraga-Estrada, left, and Hunter Songy coat shrimp in an edible gelatin to test whether the gelatin will help extend the shelf life of the shrimp. Provided photo
The Seafood Quality Laboratory is testing whether an edible gelatin made from fish skins can extend the shelf life of the shrimp. Provided photo