New Zealanders love fish and all sorts of seafood products. From fresh fish filets to smoked mussels to frozen fish cutlets, they all enjoy pride of place on our dining tables, at our BBQs and in our smokers. Depending on whether manufacturing dried seafood and seafood by-products, packing fresh or frozen fish or supplying value added processing to seafood, process control is the key to quality assurance. 



Can I grade incoming products for quality?

Rapid testing is needed to isolate products by quality for optimal use and to develop consistent products by modifying seafood blends for fat, moisture, ash, protein, collagen, and more.

The Mätt Solutions range of near-infrared (NIR) analysers, both at-line (DA7250) and in-line (DA7350, DA7440) measure in-production samples to help control the manufacturing process. Fast and accurate results mean adjustments can be made in real time to better meet targeted critical control points. In less than 10 seconds an NIR instrument can deliver results for parameters such as fat, collagen or moisture to enable an insight into each batch and make the best adjustments to ensure consistency for the consumer.  

Why is Water Activity important to quality in processed, ready to eat fish and seafood products?

Water activity is a measure of the “free” water available in a product to drive chemical reactions (like microbial growth) – by controlling water activity or the correct “dry” level, microbial growth, mould and spoilage from rancidity can be controlled.  Having a specified water activity target can also create an objective measure of the right texture to ensure consistency and uniformity of product. In any dry product, and especially seafood, product water activity is best correlated to inhibition of each pathogen’s growth. Drying to a low water activity is essential to ensure no growth of pathogens and mould but over drying can also have negative effects by encouraging lipid oxidation. With varying fat and moisture levels in raw ingredients, it can be difficult to establish a drying time appropriate for different batches. This is why an objective measure of the finished product, coupled to fast results, can give far better consistency and increase profits. Mätt Solutions are New Zealand’s water activity specialists both in offering the water activity instruments for your quality control like the Aqualab 4TE, Aqualab 3 (AQ3) and Pawkit, and also offering water activity testing services at our lab in Christchurch.

Will Modified Atmosphere Packaging extend my Shelflife?

The packaging of fresh seafood, when done right, increases its shelf-life. Packaging seafood into a modified atmosphere package (MAP) inhibits bacterial growth. However, leaks can cause shelf-life to be ¼ of what it is in a good MAP package (i.e., no air getting in or out). The challenge is in identifying when a leak is present and ensuring that the quality control process is strong enough to stop leaking packages from reaching customers. Mätt Solutions specialise in modified atmosphere packaging QA/QC and provide a variety of MAP package testing tools, enabling a seafood processor to get the best seafood shelf-life. These tools include the traditional water bath which can tell where a leak is and help in trouble shooting, through to non-destructive leak testing with either a Dansensor LeakPointer (for use when flushing in CO2) or Bestech (for use when flushing with 100% nitrogen). For 100% quality assurance by testing every package that comes off the line, there is also the Dansensor LeakMatic – giving an assurance that customers are kept safe and providing brand protection with a guarantee that the expected shelf-life is achieved. Gas Mixers and Online MAP Gas Analyzers are utilised to control and monitor the gas (Oxygen O2, Carbon dioxide CO2 and Nitrogen N2) needed for fish and seafood. Headspace Gas Analysers and Leak Detectors provide the quality control needed to guard against costly product recalls.

Is there a fast way to perform shelf-life testing/verification on fish/seafood products?

Mätt Solutions offer shelf-life testing services that look at the product's "complete picture", considering all its aspects to determine when and what ends the shelf-life of fish or processed seafood. Packaging provides protection from extremes in light, temperature, humidity and oxygen all of which will reduce shelf-life if not controlled. To perform an accurate shelf-life test, it is imperative to expose the product to different conditions to know when and why it fails. Mätt Solutions have a wide selection of chambers and simulation set-ups to test these extremes, abuse scenarios or simulations and help determine the shelf-life and durability of chilled products by offering shelf-life studies as applicable. At the end of the trial, a comprehensive report is provided that states the actual shelf-life of the product, outlines reasons for failure and in most cases recommends ways to improve. This report tends to be a requirement by most supermarket chains and is well received by auditors and MPI (Ministry of Primary Industries) 

What is the water activity of dried fish?

When drying fish, a water activity of 0.85 or below prevents the growth of pathogens such as Staphylococcus aureus or Clostridium botulinum. A water activity of below 0.85 also halts toxin production and is recommended for any shelf-stable dried product. 

Which is “better” for Quality Control (QC) of dried fish – water activity or moisture content?

For products that have very low moisture content, such as a dried fish, water activity gives a more relevant repeatable result than moisture content. When moisture content is very low, a small change can have a disproportionate impact, because of this a method that stresses repeatability vs accuracy is preferred.

How much salt is in salted fish brine?

Salt inhibits the growth of microorganisms by drawing water out of microbial cells through osmosis. Concentrations of salt up to 20% are required to render most species of unwanted bacteria inactive or dormant. The salting process should be verified BOTH by measuring the salt content via a salt meter AND by measuring the water activity of the finished product. 

What is the water activity of smoked fish/mussels?

According to MPI guidelines for the safety of hot-smoked seafood for food safety the water activity of hot smoked seafood should be below 0.85 for protection against pathogen growth.

Should fresh fish packaging be gas flushed?

The use of a modified atmosphere packaging (MAP) for fresh fish and seafood products has the potential to more than triple the effective shelf-life. When gas flushing cooked, cured or processed fish and seafood products, Dansensor, specialise in gas flushing instrumentation, recommend a gas mix of 30% CO2/70% N2 for retail supply or 70% CO2 / 30% N2 for bulk wholesale supply.  

What is the best gas mixture when using MAP for fresh fish?

Products that are high in fat can often absorb CO2 and change the gas ratio in a MAP scenario. The recommended gas mixture for fresh fish depends upon the fat content. A high fat fish should use 40% CO2/60% N2 which drops to 30% CO2/70% N2 for low fat fish. The reduction of oxygen also slows down lipid oxidation and the development of rancidity. While not immediately a safety concern, rancidity can lead to an unpleasant customer experience and cause complaints. 

What is the shelf-life of gas flushed, chilled fresh fish?

The shelf life of fresh fish and seafood products is highly variable depending upon type of fish, handling and the MAP mix used. In general, the use of the temperature control and correct gas mix for each breed of fish can more than triple the shelf-life of a product that is not gas flushed.