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Water activity contributes to the efficient, safe production of food, pharmaceuticals and cosmetics

17 October 2011

Water activity is a remarkably versatile quality metric in the food, pharmaceutical and cosmetic industries, and is applicable at several different points within the production process.

Water activity measurements can help to prevent quality-related problems such as mould growth and adverse changes in taste and texture, plus it can avoid wastage of ingredients and energy.

To maximise the benefits available from water activity measurements, the research and development department should first use water activity and moisture sorption isotherms to formulate the product in order to optimise the taste, texture, packaging, safety and shelf life.

Whereas water activity is a measure of the energy status of the water in a component (eg an individual ingredient) or system (eg a complete food product), a moisture sorption isotherm is a graph of the relationship between water activity and moisture content (as a percentage) at a specific temperature; sometimes a set of isotherms will be generated at different temperatures to characterise more fully the component or system. The specifications created by the R&D scientists can then be used as the basis for the acceptable limits elsewhere in the production environment.

For example, incoming ingredients can have their water activity measured as part of the acceptance procedure. Isotherms will provide information to indicate whether a given water activity will cause spoilage during storage, thereby helping to eliminate waste and ensure that storage conditions are optimised.

Once the ingredients enter production, managers can monitor the water activity and adjust process parameters such as temperatures to ensure that products are not over- or undercooked. Further measurements of water activity by quality assurance and quality control personnel can verify that every batch complies with all of the product specifications. For instance, the R&D scientists are likely to have specified HACCP (Hazard Analysis and Critical Control Point) water activity specifications. Further water activity measurements can be used prior to shipping to ensure that batches are within specification before being delivered to customers - who may also have specified upper and lower limits for water activity.

Water activity can be used by managers to gain an insight into the performance of the production plant. As an accurate scientific metric, water activity can provide highly reliable data for evaluating a plant's performance, thereby helping to raise efficiency and reduce variation and waste.

Fortunately the instruments manufactured by Decagon Devices for measuring water activity and for generating isotherms are extremely simple and quick to use. The phrase used by the company is "If you can microwave a burrito, you can run a highly accurate water activity test." High-resolution moisture sorption isotherms are similarly straightforward to generate, and the Decagon instruments can complete this process in just two days - which is considerably quicker than the traditional methods used.

Labcell is the sole UK distributor for the water activity instruments manufactured by Decagon Devices. Data sheets can be downloaded directly from Labcell's website at www.labcell.com or contact the company to request a copy of the new 'Managing by Water Activity' booklet or with specific enquiries by telephone on 01420 568150 or email mail@labcell.com. 


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