Dry Foods

When done properly, drying food has several benefits including longer shelf life, more consistent product, easier transport and a concentration of flavours and nutrients. 

Why is water activity important in dry foods?

Read this article to learn more

What is a good Water Activity Meter?

To understand how well a production process is working and if the best food safety standard is being met and profits are being maximised by drying to the “best” level, a target must first be established. This target will take into account where caking and clumping starts to happen within the product and how quickly it moves from a free-flowing powder to a lumpy, congealed mess. 

The analysis to identify the precise water activity and moisture at which caking and clumping begins to occur is performed with a Vapour Sorption Analyser (VSA). The VSA is capable of generating a definitive curve relating water activity to moisture content otherwise known as an isotherm. An isotherm clearly defines phase transitions (points at which change occurs) that show what water activity level is going to be an appropriate target for balancing product quality and profit maximisation. An isotherm generation service is available at Matt Solutions as part of their shelf-life testing services. 

Does the humidity in a packing room matter?

For dried foods, producing a quality product is reliant upon controlling the production process and environment. Once the production process is completed, the product needs to be kept in a dry enough environment so as not to allow it to absorb water from the surrounding environment. This normally involves having temperature and humidity controllers and environmental monitoring systems to ensure the product is protected. 

For the monitoring of air quality and humidity in the packing room, Mätt Solutions suggest the Monnit range of battery powered data loggers. A Monnit logger, which boasts a 12-year battery life, is not chained to a wired solution. It can be moved with the product, to different drying rooms and re-sited with ease. It reports to a web-based tracking solution – enabling access from phone, computer or laptop. Custom alerts can also be set for each logger, delivering instant notification if critical control parameters are breached – leaving time to solve the problem before product must be disposed of. 

How can I extend the shelf-life of my dried product?

Water activity and moisture combined with modified atmosphere packaging are major primary driving factors in the shelf life of dried products. The ideal water activity needs to be maintained at a level that ensures a high-quality product. Poor packing material, packing process and handling can undo all the hard work. Modified Atmosphere Packaging/Gas flushing is utilised to minimise oxidation, rancidity and mould growth in dry foods/ingredients. Mätt Solutions offer specialist solutions in modified atmosphere packaging (MAP) QA/QC, barrier film testing and have pioneered a variety of MAP package testing tools to ensure packaged dried products last. Ametek Mocon Gas Mixers, such as the Map Mix Provectus and Online MAP Gas Analyzers, such as the MAP Check 3 are essential for control and monitoring of the gas composition needed for dried food products. Headspace Gas Analyzers, such as the CheckMate 3 and CheckPoint 3 along with Leak Detectors (the offline LeakPointer 3 and inline LeakMatic 2) provide the quality control needed to confidently ship products to market. If a waterbath leak detection system is preferred, there is also the extremely robust Haug PackVac. Another alternative in leak detection is Bestech – which offers non-destructive leak testing by using pressure decay to find even the smallest holes.

Is there a fast way to perform shelf-life testing/verification on dry foods?

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 dry food products’ shelf-life. Microbial growth, pathogens, oxidation and sensory aspects like colour, odour and texture are all considered. 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 and help determine the shelf-life and durability of dry food products by offering both accelerated and real time shelf-life studies as applicable. At the end of the trial, a comprehensive report is provided, stating the actual shelf-life of the product, outlining reasons for failure and in most cases recommending 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 water activity or moisture content does a product need to be to prevent caking/ clumping/lumps in a dry powder?

Every product behaves differently and starts to form lumps at a different water activity. The best way to find out where your dry/powdered product starts to form clumps or lumps is with an isotherm analysis.  

What water activity will prevent lumps in a dry powder?

Because every product behaves differently and starts to form lumps at a different water activity this is impossible to provide a single answer to.  The best way to find out where your dry/powdered product starts to form clumps or lumps is with an isotherm analysis.  

What is an isotherm?

An isotherm charts the relationship between water activity and moisture content. It can be used to predict where a dried, powdered product will start to cake/clump/form lumps. This is then used to establish a quality control point/critical control point for a dried food/powders

How much moisture is in a dry food?

This is different for every food. A product such as sugar will be only 1%-3% moisture, while some dried foods leave more moisture in the product which influences texture. Often, more moisture means more profit in a product that is sold by weight hence the need to optimise. Moisture content can be determined with a moisture meter, a water activity meter or, if a one-off test is required Matt Solutions provides a moisture content testing service. 

Does a dry food need to be gas flushed?

Gas Flushing/Modified Atmosphere Packaging is the removal of a gas to replace with a more desirable one. Often this is the removal of Oxygen and replacement with Nitrogen and Carbon Dioxide.

Products that are subject to lipid oxidation or rancidity will benefit from gas flushing or packing in a modified atmosphere. Gas flushing will also assist in control of the humidity in the headspace of the package and stop a very dry product from absorbing moisture in the air and starting to form lumps. 

What is OTR and WVTR?

OTR, or oxygen transmission rate and WVTR (water vapour transmission rate) refer to how much oxygen or moisture will travel through or “get through” a packaging material over time. Another term for this is permeability. This is important for a dried product – if the packaging is of poor quality and allows water vapour though, the powder can “absorb” this water and form clumps, develop mould or change in texture. Over time, powders can turn from a free-flowing powder into a solid mass/brick.