Posted on July 7, 2016
Humans have evolved as highly visual creatures, using color as one of the most important signifiers of safety. From a red stop light to a brightly colored snake, color acts as an instant and instinctual visual alarm bell warning us of potential dangers. This use of color as an indicator of safety is perhaps most clearly evidenced by the act of pulling out a piece of fish from the refrigerator and asking, “Does this look okay to you?”
Unlike many color/perception relationships, the one between fish color and food safety is relatively linear; although even experts may not be able to distinguish between white and red wines in blind taste tastes, you can be pretty sure that if a fish looks bad, it is bad. The color change itself is an indicator of a specific sequence of biological events and the process begins almost immediately following death. As Nollet and Foldra point out in the Handbook of Seafood and Seafood Product Analysis
The appearance of a newly landed fish is unforgettable, in that the interplay of subtle shades of beautiful colors make it a joy to behold and irresistible as an item of food. Just a few hours after death, though, it begins to look less obviously attractive, and its now ‘ordinary’ colors are much more familiar to the majority of the public.1
Just as familiar is the look of spoiled fish product: dull, lifeless, decaying, and carrying the potential for food poisoning.
But the determination of fish freshness isn’t just up to individual consumers; the seafood industry as a whole must take great care to assess the quality and safety of products throughout the supply chain, particularly at a time when traceability is a growing concern.
Instrumental Determination of Fish Freshness
Because the color of fish acts as a relatively predictable indicator of freshness, instrumental color analysis offers a simple, economical, and rapid method of reliable quality assurance. By replacing subjective human vision, which is prone to a host of biological and environmental vulnerabilities, instrumental color analysis provides a clear and stable basis of assessment that ensure fish is evaluated the same way every time, regardless of operator skill or location. The sophisticated color measurement capabilities of modern spectrophotometers make them ideally suited to objectively assess fish freshness at key points in the supply chain, from raw product to minced, dried, cooked, or otherwise processed fish. Not only does this allow you to evaluate the quality of fish and fish products for the safety of the public, but it also allows you an objective way to identify potential mishandling either within your own facility or by your suppliers and take swift action to correct the issue.
Choosing the Right Spectrophotometer
Fish, however, present several unique physical qualities that make the choice of spectrophotometer particularly critical to obtaining accurate, repeatable measurements. First, the color of fresh fish is rarely homogenous, but rather intricately variable. As such, a single measurement may not provide a complete picture of fish freshness. Selecting an instrument that can take multiple measurements in rapid succession and average the results is vital to ensuring that the color values truly represent the sample as a whole. Fish and fish products may also be textured and require labor-intensive sample preparation using outdated spectrophotometric instruments. Choosing a spectrophotometer with integrated height measurement eliminates the need for this sample preparation because it automatically accounts for height variation, eliminating the risk of operator error and saving valuable time.
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