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Water Activity (aw) Chart: Typical Food Values and Microbial Growth Limits

Water activity tells you how much of the water in a product is free for microbes to use. It is one of the first numbers a food scientist checks when deciding if a product can sit on a shelf without refrigeration.

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Group	Food or organism	Typical aw or minimum aw for growth	What it means
Food	Fresh meat, fish, milk, fresh vegetables	0.98 to 0.99	Supports all common spoilage and pathogen growth; needs refrigeration
Food	Fresh fruit	0.97 to 0.99	Acid and pH usually limit pathogens, molds and yeasts still grow
Food	Bread and soft baked goods	0.94 to 0.97	Mold is the main shelf life limit
Food	Soft and semi-soft cheese	0.95 to 0.98	Moisture, pH and salt together control safety
Food	Hard aged cheese	0.90 to 0.95	Lower aw plus low pH slows many organisms
Food	Cured ham and dry sausage	0.85 to 0.93	Salt and drying are the controls; staphylococci and molds remain concerns at the upper end
Food	Jam, jelly, marmalade	0.75 to 0.85	Sugar binds water; molds and osmophilic yeasts are the main spoilers
Food	Fruitcake and sweetened baked goods	0.73 to 0.83	Shelf stable when aw and preservatives are controlled
Food	Honey	0.50 to 0.65	Too dry for most growth; fermentation risk if moisture rises
Food	Dried pasta and rice	0.30 to 0.50	Shelf stable while kept dry
Food	Crackers, biscuits, breakfast cereal	0.10 to 0.30	Texture loss from moisture pickup is the limit, not growth
Food	Dried milk powder	0.20 or below	Salmonella can survive dry but not grow; keep dry
Organism	Most spoilage bacteria	0.90 to 0.91	Typical lowest aw for growth of common bacteria
Organism	Clostridium botulinum, proteolytic types	0.94	Growth stops below this aw in otherwise suitable conditions
Organism	Clostridium botulinum, non-proteolytic types	0.97	Higher minimum than proteolytic strains
Organism	Salmonella	0.94	Growth limit, but survival in low aw foods can last months
Organism	Escherichia coli	0.95	General minimum for growth
Organism	Listeria monocytogenes	0.92	Grows at refrigeration temperature; one of the lower bacterial limits
Organism	Staphylococcus aureus	0.86 (aerobic growth)	Lowest aw at which a common pathogen still grows
Organism	Most yeasts	0.88	Fermentation and gas spoilage risk above this
Organism	Most molds	0.80	Xerophilic molds grow down to about 0.65
Organism	Osmophilic yeasts	0.60	Practical floor for microbial growth in foods
Regulatory	Food Code non-TCS threshold (food with aw of 0.85 or less)	0.85	A product at aw 0.85 or less and meeting other conditions may not need time and temperature control

Values are typical published ranges and vary with product, temperature, pH and measurement method. Shelf stability depends on aw together with pH, preservatives, heat treatment and packaging. Validate with a calibrated water activity meter and a challenge or stability study.

Link lab results to lots

Optional review of how aw and micro results can be attached to lot records so release decisions use real data.

Optional. The tool and every export work without this. No spam.

How to use the table

Find the food group nearest your product to sanity-check a measured aw, then read the organism rows to see what can still grow at that value. If your product measures 0.88 for example, the table shows that most bacteria are inhibited but many yeasts and almost all molds can still grow. Export the rows you need to build a formulation or shelf life justification.

Measure aw at 25 C with a calibrated chilled mirror or capacitance meter
Test the worst-case lot, not only the average
Re-test after a formulation change in sugar, salt, humectants or moisture

Water activity is not moisture content

Moisture content is how much water the product holds. Water activity is how available it is. Honey can hold about 17 percent water and still sit near 0.55 aw because sugar binds that water. That is why two products with the same moisture can behave very differently on a shelf.

Combining aw with other hurdles

Few products rely on aw alone. Hurdle technology combines aw, pH, heat treatment, preservatives, temperature and packaging. A product with aw 0.90 and pH 4.2 may be safe where aw 0.90 alone would not be. Document each hurdle and its validated limit, and treat aw as a critical control only when it is monitored at a frequency that can catch a drift.

Common mistakes

Measuring a surface sample of a product that equilibrates unevenly, ignoring temperature in the reading, assuming a dry product is always safe even though Salmonella survives in low aw foods, and using a single published number instead of the meter reading from your own plant.

Frequently Asked Questions

What water activity is considered shelf stable?

There is no single number, but many bacteria stop growing below about 0.91 and most molds below about 0.80. Shelf stability also depends on pH, preservatives and heat treatment, so use aw as one hurdle among several.

Can Salmonella survive in low aw foods?

Yes. Salmonella cannot grow below about 0.94 aw but can survive for long periods in dry foods such as powders and nut butters, so kill steps and environmental control still matter.

What does aw 0.85 mean for TCS foods?

The FDA Food Code treats a food with aw of 0.85 or less and a suitable heat or processing history as not requiring time and temperature control. Check the Food Code table for the exact conditions that apply.

How is water activity measured?

With a meter that equilibrates a sealed sample and reads the relative humidity of the headspace, then divides by 100. Calibrate with certified salt standards and control sample temperature.

If aw readings are logged in a lab system, Netray can help connect them to lot records in your ERP. The reference works on its own with no contact.

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