What is the water activity?

Water activity - the key to food safety and shelf life

What is water activity and why is it crucial for food?

Water activity (aw) is a key factor in food science. It indicates how much free water is available in a product for microbial, chemical or physical processes. The aw value is between 0 and 1, with pure water having a value of 1.0. Foods with an aw value below 0.6 are considered to be virtually resistant to microbial growth.

Why is water activity so important for food?

🔹 Control microbial growth
A low aw value prevents the growth of bacteria, yeasts and molds. Bacteria generally require an aw value of at least 0.91, while yeasts and molds can thrive at lower values.

🔹 Extend shelf life
By reducing water activity, food can be preserved for longer. This is particularly important for long-term storage and packaged products such as dried fruit, snacks or spices.

🔹 Improve food safety
A low aw value inhibits the growth of dangerous germs such as salmonella, E. coli and listeria and thus protects against food-borne illnesses.

🔹 Use optimal preservation techniques
Methods such as drying, freeze-drying or salting aim to reduce water activity in order to keep products fresh for longer.

🔹 Maintain texture and quality
Water activity influences the consistency of food. Snacks, cookies or baked goods need a certain aw value to remain crispy, while too much water activity can make them soft or sticky.

🔹 Prevent undesirable chemical reactions
High water activity can accelerate chemical processes such as lipid oxidation or enzymatic browning, which leads to a loss of quality.

🔹 O ptimize packaging
The right packaging protects food from moisture migration, which can cause undesirable changes in texture or mould growth.

Simple measurement with the humimeter RH2 water activity meter

With the humimeter RH2, you can quickly and precisely determine the water activity of your food. Thanks to two different sensors, you can optimally adapt the measurement to the properties of the material - for reliable results and maximum product quality.

Link Humimeter RH2 AW value

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Performance features

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Extensions and accessories

Art.no.	Image	Extension, accessories
13700		KIT Aw-value measuring chamber and humidity-temperature sensor - screw-in glass aw-value measuring chamber and humidity/temperature sensor with 2 meter connection cable - incl. accessories: 2 pcs. 186 ml screw-top jar, 2 pcs. Screw-top jar 245 ml, 4 pcs. Twist-off lid, calibration ampoule set Art. No. 10005, factory calibration certificate Art. 10403, case Art. 13624 (suitable e.g. for dried fruit / sausages, cheese and other foods)
14500		KIT aw-value measuring cell 25 ml made of aluminum aw-value measuring cell 25 ml made of aluminum, with attachable humidity-temperature sensor with 2 meter connection cable - incl. accessories: 10 pcs. Plastic inserts PP 25ml for the measuring cell, calibration ampoule set Art. No. 10005, factory calibration certificate Art. 10403, case Art. 13624 (suitable for small quantities of powder / hemp / teas, herbs, saffron etc.)
10600		Factory calibration certificate Material humidity Factory calibration certificate - Calibration delivery record for material moisture meters
11235		Certified oak ampoules Certified oak ampoules - set of 5 pieces 80% RH.
10352		Certified oak ampoules Certified oak ampoules - set of 5 pieces 50% RH.
10005		Certified oak ampoules Certified oak ampoules - set of 5 pieces: 2 pieces 35 % RH, 1 piece 50 % RH, 2 pieces 80 % RH.
14433		Thermal printer Thermal printer with battery - Mobile serial printer for Humimeter devices with USB interface
13741		Screw jars Screw vials replacement set with sealing cap for aw-value measuring chamber Art. no. 13700: 14 pieces with filling volume max. 186 ml
12485		Data interface module Humimeter USB data interface module AKKUVERSION with LogMemorizer measurement data acquisition and evaluation software on USB stick including USB cable for PC
14126		Plastic cans Plastic cans (PET) with sealing lid for aw-value measuring chamber Art. no. 13700: 14 pieces with max. filling quantity 200 ml
13740		Screw jars Screw vials replacement set with sealing cap for aw-value measuring chamber Art. no. 13700: 14 pieces with max. filling volume 245 ml
12278		humimeter USB data interface module humimeter USB data interface module with LogMemorizer measurement data acquisition and evaluation software including USB cable for PC (Attention: retrofitting option only possible in the factory)