Powders & Concentrates
There are myriad ways of drying different products, each is for a different purpose and will have different critical control points. However, whether it be a spray drying, drum, freeze drying, oven drying or air drying, monitoring measuring and recording the water activity is going to be one of the critical factors in ensuring quality and safety – and with water being the cheapest ingredient in any of these products, also maximising profits.
In general, dried powder products will have an aW in the very low range – anywhere from 0.1 aW to 0.5 aW. This is highly product dependent and Critical Control Point (CCP) targets should be set with the assistance of a Vapour Sorption Isotherm.
Most of the dried or powdered products that Mätt Solutions sees in our shelf-life testing facility will have a moisture content below 5%.
When using a moisture balance the test time and the repeatability are both affected by the sample volume. Some moisture balances will conduct a test with as little as 1gram of sample, this however offers poor repeatability. For “best” accuracy sample volumes more than 4 grams are generally recommended, however this severely increases the test time so is very much a trade-off that the production manager needs to make a decision on.
The removal of Oxygen is required as this will slow down chemical reactions related to spoilage. Because of this, a MAP mix of either 30% CO2 and 70% N2 or 100% N2 is recommended.
Note: As many dried or powdered products are also highly hygroscopic, even if the removal of oxygen is not required, many producers will want to ensure that their product is not negatively impacted by being packed in humid air.
Moisture content testing is highly variable depending upon the method used. Analysis with a moisture balance generally takes from 5 minutes up to an hour. While the recommended (oven drying) ASTM methods often range from 3 to 24 hours.
When using the Meter Aqualab 3, with fast water activity readings enabled, water activity analysis takes just 60 seconds. This can also be correlated to moisture content. The time taken to conduct a water activity test is not affected by the sample volume.
In most instances, Mätt Solutions recommends the use of water activity as a CCP as it is both more accurate and more repeatable than moisture content. Water activity is also more significant for qualitative considerations such as product stability, shelf life (e.g., microbiological & enzymatic stability, aroma retention), handling characteristics, physical properties and chemical stability.
A major quality control stumbling block with powders has always been caking and clumping. To measure, predict and subsequently avoid this, water activity (aW) is a key factor. Working with Meter Food (formerly Decagon Aqualab), Mätt Solutions offers a comprehensive suite of water activity meters that are suitable for all any sort of powder or concentrated flavouring. This includes the PaWKit, an at line meter suitable for inspectors or spot inspections, the exciting new AQ3 – offering water activity analysis in only 1 minute, the highly accurate Aqualab 4TE, or if your sample has volatiles, the Aqualab TDL 2 (Tunable Diode Laser) that can deliver accurate aW readings, even when the product has volatile ingredients or oil.
To understand how well a production process is working and if 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 Mätt Solutions part of their shelf-life testing services.
For powders, 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 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 suggests the Monnit range of battery powered data loggers. A Monnit logger, which boasts a 10-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.
Leak Detection is key for shelf life. Products that are exported, particularly to hotter / humid regions are extremely susceptible to failure from a poor or weak seals – this will allow moist/humid air into the package and cause physical changes to powders. With this in mind, a quality leak detection system can be your insurance policy. At its simplest level – leak detection starts with the tried-and-true waterbath – immersion in water followed by drawing a vacuum to create a pressure differential between the inside and outside of the package. We then look for leaks as bubbles – the Haug PackVac and Dansensor LeakPointer H2O excels in this arena, with chambers as large as 85cmx65cmx60cm they offer a robust and easy to use solution. If you prefer non-destructive leak testing with truly objective results there is also Bestech, which works based on pressure decay and the Dansensor LeakPointers which detect the presence of CO2 if this is what you are using in your gas flushing process.
Bulk density is the weight of a volume unit of powder and is usually expressed in g/cm3. For the powder manufacturer, whether air drying, spray drying or freeze drying, a measure of the bulk density is useful on two key fronts – it will provide information regarding how much a powder can be expected to “settle” in the package during shipping, how much weight a package can hold in terms of volume/ fill height, which also has as direct impact on customer perceptions. The Engelsmann StavII jolting bulk density meter “taps” a cylinder to measure how much a powder settles in terms of volume.
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 for a powdered food product. 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 powered products by offering both accelerated and real time 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).