Sensory Analysis: Using Visible Spectrophotometry for Quality Detection in Fish

There is perhaps nothing better than the taste of fresh-caught fish, and if you’re lucky enough to have a fisherman in your family, you probably understand what I mean. However, the fishing season only lasts so long, and soon it’s necessary to turn to local fish markets or the frozen food aisle to keep this healthy and delicious protein option in our diets. Supermarket fish comes from a variety of sources, and the methods that are used to process and package it depends on quality measurements through sensory analysis.

frozen fish sensory analysis
Both fresh and frozen fish must undergo rigid testing before it reaches the supermarket or frozen foods aisle.
Image Source: Flickr user Frank Kovalchek

Sensory analysis involves the human perception of food through sight, smell, taste, and touch. However, human perception has its limits and is highly subjective, making quality evaluation and consistency difficult to achieve. Visual perception is the most powerful factor in food selection and greatly affects consumer decisions, yet color perception varies from person to person, and humans experience many challenges with color memory. This is why color measurement instrumentation plays a vital role in sensory analysis for quality control. Visible spectrophotometers use human eye technology to emulate the way we see color, but also can quantify colors objectively and consistently. Assessment of fish quality is dependent of visual spectrophotometry to obtain accurate information to determine freshness, spoilage, and/or food safety through the use of sensory analysis.

Color measurement and quality control of fresh and frozen fish

Monitoring fresh fish is a very complex and scientific process, and can be conducted in several different ways. Various test methods are used to evaluate for spoilage in fish by detecting total bacterial numbers, total volatile bases, TMA, total volatile reducing substances, indoor sensory analysis, refractive index of the eye fluid, electrical parameters of the fish flesh, volatile acids, volatile ammonia, and total volatile nitrogen. Chemical testing for the determination of trimethylamine-nitrogen (TMA-N) in fish samples is commonly used and effective, but can alter the integrity of the sample. Spectrophotometers use sensory analysis to create a colorimetric assay for determining TMA-N without affecting the sample composition. The Association of Official Analytical Chemists (AOAC) proposes that a combination of head-space single drop microextraction and microvolume UV-vis spectrophotometry provides the highest level of accuracy for detecting spoilage in fresh fish products.

salmon sensory analysis
Fresh fish is analyzed for quality by detecting any traces of bacteria through analytical processing and spectrophotometric evaluation.
Image source: Flickr user pui wong {as*q}

Sensory analysis in frozen fish is also beneficial for meeting standards and regulations governing the manufacturing and processing of commercial fish products. The United States Standards for Grades of Frozen Minced Fish Blocks relies on spectrophotometric evaluation of fish to provide deteriorative color analysis for product safety. Color measurement uses sensory analysis to detect any changes in frozen minced fish blocks. These changes are defined in the NOAA (National Oceanic and Atmospheric Association) guidelines, stating:

Deteriorative color refers to discoloration from the normal characteristics of the material used. Deterioration can be due to yellowing of fatty material, the browning of blood pigments, or other changes.

  • Slight deteriorative discoloration–refers to a color defect that is slightly noticeable but does not seriously affect the appearance, desirability, or eating quality of the product.
  • Moderate deteriorative discoloration—refers a color defect that is conspicuously noticeable, but does not seriously affect the appearance, desirability, or eating quality of the product.
grilled salmon sensory analysis
The use of visual and spectral analysis helps to ensure delicious and safe seafood dishes.
Image Source: Flickr user snowpea&bokchoi

Spectrophotometers for sensory analysis

Advancements in spectrophotometric technology have led to the development of a variety of instrumentation options available for sensory analysis in the commercial fishing industry. HunterLab specializes in portable and benchtop spectrophotometers that are rugged and durable, and can be used nearly anywhere. Our state of the art technology provides the most accurate color measurements for quality assurance. We work together with our clients to understand both their challenges and needs and provide a solution that works. Contact HunterLab today to learn more about spectrophotometers and quality control in the fish processing industry.

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