Water Activity Measurement
Every living organism owes its existence to water. Water activity indicates the energy of water, which determines if it is biologically available to these microorganisms. As it relates to manufacturing, water activity also affects a product’s texture, taste, color, nutritional value, and its shelf life. Every species of microorganism, such as bacteria, yeast, or mold, has a minimum water activity value at which they will grow. If the water activity of their environment should drop, their growth is no longer possible.
The water activity measurement of the energy of water in any product affects both the product quality and its shelf-life. This factor is particularly critical in highly regulated industries such as pharmaceuticals, food, and cosmetics. If the energy of the water in a product is too high, for example, there is a risk of its contamination by microbial growth. In addition, if the storage humidity for a product is too high, it can increase the water activity and lead to clumping, changes in consistency or taste, diminution of nutrients which affect the product’s value, as well as markedly reducing its storage and shelf-life.
Well-documented and scientifically established guidelines that are also supported by FDA regulations outline these thresholds of microbial limits using a water activity (aw) range or scale. This water activity (aw) range provides the lowest rating for inhibition of microorganisms. In addition, identifying the ideal water activity for any product can minimize the risk of other degradative chemical and physical reactions that, for example, affect shelf life in foods.
Pure water has significant, measurable energy and is classified as having a water activity of 1.00. As water in a product interacts with other polar materials in the product, the water's energy, and hence the water activity (aw) decreases. The degree to which the energy of the water is reduced depends on the type and nature of the other ingredients. The lower end of the water activity scale is zero, but this value is only theoretical and cannot be achieved.
Understanding and documenting how water activity is affected by different material substances provides valuable information. Using this information provides a way for researchers/manufacturers to take proactive measures to lower water activity as they seek to improve the microbial, chemical and structure stability of foods, pharmaceuticals, and other materials.
Water activity testing makes it possible to monitor, control, and optimize product manufacturing and preservation processes, thereby ensuring physical, chemical, and microbiological stability of moisture-sensitive products. Therefore, water activity measurement is a key tool for numerous industries to remain regulation compliant.
In addition, manufacturers of foods and pharmaceutical products must, for example, show to the FDA that the water activity of a product has declined to such an extent that bacteria can no longer grow. This metric can be determined by water activity meters which measure the water vapor pressure generated by the water molecules in foods and other products not bound to water-binding sites and are a key parameter in the quality control of all shelf-stable materials.
You already know that water activity measurement is important to maintaining the high product quality and product shelf life you strive for. Whether you are measuring water activity in foods or in other applications, the quality, accuracy, and excellence of your water activity testing equipment is of the utmost importance to you. That’s why we’d like to introduce you to a brand that can guarantee the highest quality and innovation - the Novasina Swiss line of water activity meters.
The Novasina brand developed a unique electrolytic measuring sensor that enables highly accurate measurement of water activity (aw-value). Novasina’s precise water activity equipment is used around the world in many industries from food and pharmaceuticals, to oil and chemicals. The water activity testing instrumentation can be used in for water activity measurement in processing and quality control, on the production line, or for laboratory analysis and product development.
We offer three incomparable Novasina Models to provide the volume, speed, and accuracy required by the various industries that perform water activity testing: The Lab Swift, economical water activity meter, The Lab Touch, a mid-range choice in water activity equipment, and The LabMaster Neo, widely acknowledged as the new global standard in water activity measurement.
In addition, Neutec highly recommends that you to use a filter with the sensor to protect it and to prolong its life span - to choose the filter that works best for your sample- click here
Our in-house team of specialists and highly trained engineers will take care of servicing, maintaining, and calibrating your water activity equipment for you. Let us know if you need any assistance!
FREQUENTLY ASKED QUESTIONS
Water activity is greatly affected by temperature, thus its standardized at 25°C and that is the temperature used by regulatory agencies.
Temperature control assures higher accuracy results, provides a constant equilibrated environment for repeatable testing and complies with regulatory testing that is carried out at 25°C.
The calibration standard salts that come with the unit are used in two ways. They are used for calibration, so there is always an accurate curve to compare your samples to. They are also meant to provide you with a means for verification daily. This way you can identify any drift in your readings and correct it or call us for support,
Yes, you can certainly use the standards multiple times. These salts are NOT disposable. They have a shelf life of 2–4 years depending on factors such as storage conditions (storage container must be well closed), frequency of use, exposure to light and the value of the standard.
Calibration frequency is based on your internal SOP but a good rule of thumb is to carry out a calibration at least once per month and to carry out a verification at the start of each day.
Yes, the Novasina units in conjunction with special protective filters can be used to measure samples that contain volatiles. We strongly recommend the use of filters if there is any doubt to protect and prolong the life of the sensor.
No, Novasina units are very simple to use and do not require much maintenance. We suggest keeping the units clean and wiping them down at the end of each day with a cloth and keeping the measuring chamber clean and free of debris. Also, we recommend having a PM (Preventative Maintenance) completed once a year to keep the unit running in top condition.
Yes, Neutec provides 3 different services for the water activity units. A PM (Preventative Maintenance) service, a VC (Verification Calibration) service and a CC (Certified Calibration) service. All three of the services come with completion documents and the Certified Calibration is also 21 CFR Part 11 compliant from a government certified laboratory.
A PM (preventative maintenance) is a proactive measure taken to ensure that your unit does not suffer any damage due to preventable issues caused by wear and tear and that it continues to run like new for years to come. A PM is completed by performing a full “tune up” of the unit, which includes full diagnostics, calibration, replacement of pre-filters, internal sterilization, cleaning and certification.
It will mainly depend on the sample itself, as different materials release water at different rates. Our units report the AW value once the equilibrium point has been reached. Yet you can stop the unit at any time and take a reading. Waiting to reach stability is the most accurate method. Speeding this process may result in inaccurate results generated and recorded.
These specially designed filters shall be mounted in front of the sensor and used to provide protection against chemical contamination and degradation of the resistive electrolytic sensor element.
As the inner part of the sensor consists of a liquid, volatiles which dissolve and dissociate are extremely dangerous and harm the sensor in a very short time.
Be aware that sensor failure due to chemical contamination by NOT using an appropriate chemical filter is not covered by warranty and replacement goes 100% on the user's account.
For that reason, it is inevitable to check sample composition for volatiles PRIOR to order the instrument. We will ask you those questions and will hand you this document for signing.
We fully understand if sample compositions and/or recipes cannot be shared with us but somehow we must gather the information, respectively ensure, that we can offer the best possible solution for a reliable, accurate and repeatable water activity measurement of your samples.
Many questions about changing interval were and are brought to our attention. Unfortunately, there is no precise guideline but a rule of thumb:
If you do less or equal than 10 measurements a week, change filter every 6-12 months
If you do more than 10 measurements a week, change filter every 3-6 months
If instrument is in use, day and night, change filter every 2 months
Please read the operating instruction manual of the water activity meter as well to learn about the procedure how to find out the optimal chemical filter changing interval. It is important that the filter is changed from time to time as it is of saturation type. Once saturated, volatiles will pass through and harm the sensor.
Be aware that sometimes filter combinations must be used to get highest protection efficiency. As soon as ethanol is involved, our alcohol-resilient sensor (CM-3 or awSens-ELS) must be used. If ethanol is present in conjunction with other volatiles, select the alcohol-resilient sensor plus the respective filter(s) from the selection list.
Note that chemical filters will extend the measurement time as the water vapor has to pass through the filter but it will not affect the measurement value.
If you have doubts about the procedure or feel unsure how to work that out, please do not hesitate to contact us.
Download the Filter Selection Guide PDF from any water activity meter product page