Water Activity

What You Need to Know about Water Activity?

Water activity is the amount of ‘free’ or ‘available’ water in a product. The degree of availability of water is measured  by water activity (aw).

Water Activity corresponds to free available water
Moisture corresponds to free + bound (total) water

Thus water activity and moisture is not the same.

Temperature affects the aw value even when the moisture content remain the same.

aw value ranges between 0 (absolute dryness) and 1 (condensed humidity). 

The relative humidity is measured after reaching the equilibrium humidity over a sample (partial water vapor pressure) The relative humidity is measured in % RH and relates to the aw–value as follows: aw = ERH/100

The Influence of Water Activity in Products

Water activity plays a key role in the growth of harmful organisms, such as bacteria and molds, which can produce toxins or other dangerous substances. It also influences chemical and biochemical reactions, such as the Maillard reaction, which may alter various properties of a product. Most reaction rates increase with increasing aw and most reaction rates correlate better with aw than moisture.

• Microbiological stability

1. 1. Shelf-life
   2. Food safety

• Chemical stability

1. 1. Content of proteins and vitamins
   2. Reactivity of ingredients (enzymes)

• Physical stability

1. 1. Colour, taste, and nutritional value
   2. Solubility and texture

Why Our Water Activity Meter?

• Novasina uses the electrolytic sensor which is resistant to volatile samples and has fast mode availability. It also doesn’t need to be cleaned or verified frequently unlike other sensor types.
• Unlike other brands, Novasina’s aw Meter verification/calibration standards are reusable for 4-5 years, not one-time consumables.
• Over 60 years of expertise and dedication to being the world leaders in the science of water activity

How to Select the Water Activity Meter

Instrument Models

Lab Start

This is our entry model. A cost-effective aw meter designed for low to medium aw range measurements, is suitable when high accuracy and reproducibility are not critical.

• Measuring range: 0.33 – 0.75aw | 0 – 30°C 
• Accuracy: ± 0,03aw | ± 0,15°C
• No temperature control
• No 21CFR

Lab Swift

The LabSwift, equipped with a rechargeable battery, provides portable functionality. It is designed for daily use and suitable for low to medium aw range samples.

• Measuring range: 0.11 – 0.90aw | 5 – 45°C 
• Accuracy: ± 0,01aw | ± 0,15°C
• No temperature control
• No 21CFR
• Rechargeable battery option

Lab Touch

A versatile and fast water activity meter featuring a large touch screen. It is user-friendly and ideal for AT-line measurements in production or precise aw-value determination in the QC lab.

• Measuring range: 0.06 – 0.97aw | 5 – 45°C 
• Accuracy: ± 0,005aw | ± 0,1°C
• Ambient temperature control: +2°C above
• No 21CFR
• Sensor to measure samples with alcohol option

LabMaster Neo

This is the high-end model ideal for routine daily water activity measurements in QA laboratories of food and pharmaceutical companies. This instrument also aids in identifying the causes of product spoilage, texture changes, or rancidity using the optional sorption isotherm set.

• Measuring range: 0.03 – 1.000aw | 0 – 60°C 
• Accuracy: ± 0,003aw | ± 0,1°C
• Temperature control: 0 – 60°C
• 21CFR
• Sensor to measure samples with alcohol option
• Sorption isotherm set option
• Printer option
• Barcode scanner option

Filter Selection

Just as mentioned before, a range of filters is available to protect the sensor from aggressive vapors, alcohols, glycols, and more. For detailed guidance on selecting the most appropriate filter for your application, please contact us through the website form, phone, or one of our email addresses.

Optional Accessories

SAL-T / SAL-F Calibration & Verification Standards

SAL-T (picture on the left) and SAL-F (picture on the right) are used for Novasina aw meter verification and calibration. The advantage of using SAL-T is that it is reusable for 3-5 years whereas other brand standards are one-time usage.

SAL-F is suitable if you have fast-moving production or laboratory and need quicker calibration. Although it is for one-time use only, the calibration time is reduced to less than 10 minutes!

Sorption-Isotherm Set

The Novasina sorption isotherm set, designed exclusively for use with the LabMaster-aw neo, enables straightforward recording of a sorption isotherm at up to 11 points within the 0.04-1.00 aw range. These curves provide an initial general assessment of the correlation between water activity and product moisture.

A sorption isotherm test can be highly valuable for analyzing processes such as texture changes, crystallization/recrystallization, phase transitions, packaging optimization, storage conditions, and their impact on product stability.

Regeneration-Kit

Charcoal regeneration kit for restoring the sensor after exposure to strong aromas found in spices, herbs, essential oils, and sweets such as filled candies and chewing gum to preserve and extend the sensor life.

Printer BIXOLON SRP-275 III A

A printer customized for compatibility with the LabMaster-aw neo, designed to print test results and supplied with 5 paper rolls. Only LabMaster Neo can use a printer.

Wireless Barcode Scanner

Wireless barcode scanner kit for scanning batch IDs before starting measurements, ensuring full data integrity. The set includes a wireless barcode scanner and a Bluetooth communication board.

ePW Dispenser

A dispenser with sample cups for aw measurement probes, compatible with LabStart-aw, LabSwift-aw, LabTouch-aw, and LabMaster-aw neo. The set includes 5 dispensers, each containing 20 disposable sample trays.

Summary

In choosing our aw meter, it is best to know your application. You can look at the table below as the first guidance towards choosing the model but please contact our team for further information.

Higher accuracy, temperature control availability, and 21CFR also can be a consideration.

Then you need to choose the correct filter to make the sensor more long-lasting.

Lastly, there are optional accessories to choose from. Calibration standards, sorption-isotherm set, printer, etc.