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INTRINSICS - INDICATORS OF RISK

It is essential to establish a product's intrinsic values as part of a risk assessment for HACCP as well as shelf life and preservative level determinations. A key intrinsic is:

WATER ACTIVITY (aw)

Water in food, which is not bound to food molecules, can support the growth of bacteria, yeasts and moulds. The term water activity (aw) refers to this unbound water. The following information is adapted from Beuchat (1981)

Microorganisms generally inhibited by aw at this point	aw	Examples of foods within this range of water activity
	1.000	Pure water
Pseudomonas, Escherichia, Proteus, Shigella, Klebsiella, Bacillus, Clostridium perfringens, Listeria, some yeasts	0.950	Fresh meat, fish, fresh and canned fruit Bread
Salmonella, Vibrio parahaemolyticus, C. botulinum, Serratia, Lactobacillus, Pediococcus, some moulds, Rhodotorula, Pichia	0.910	Some cheese (Cheddar, Swiss, Muenster, Provolone) Cured meat (ham), some fruit juice concentrates
Many yeasts (Candida, Torulopsis, Hansenula), Micrococcus	0.870	Fermented sausage (salami), sponge cakes, dry cheeses, margarine
Most moulds (mycotoxigenic penicillia), Staphylococcus aureus, most Saccharomyces (baillii) spp., Debaryomyces	0.800	Most fruit juice concentrates, sweetened condensed milk, chocolate syrup, maple and fruit syrups, flour, rice, pulses containing 15-17% moisture; fruit cake; fondants, high-sugar cakes, fruit pudding
Most halophilic bacteria, mycotoxigenic aspergilli	0.750	Jam, marmalade, marzipan, glacé fruits, some marshmallows
Xerophilic moulds (Aspergillus chevalieri, A. candidus, Wallemia sebi), Saccharomyces bisporus	0.650	Rolled oats containing ~10% moisture, grained nougats, fudge marshmallows, jelly, molasses, raw cane sugar, some dried fruits, nuts
Osmophilic yeasts (Saccharomyces rouxii), few moulds (Aspergillus echinulatus, Monascus bisporus)	0.600	Dried fruits containing 15-20% moisture; some toffees and caramels, honey
No microbial proliferation	0.500	Noodles, spaghetti, etc. containing ~12% moisture; spices containing ~10% moisture
	0.400	Whole egg powder containing ~5% moisture
	0.300	Biscuits, crackers, bread crusts, etc. containing 3-5% moisture
	0.030	Whole milk powder containing 2-3% moisture, instant coffee, dried vegetables containing ~5% moisture; corn flakes containing ~5% moisture, dehydrated soups, some biscuits, crackers
	0.000

Technical Definition of Water Activity: The water activity (aw) represents the ratio of the water vapour pressure of the food to the water vapour of pure water, under the same conditions and it is expressed as a fraction.

We can measure your product aw, pH and O2 levels as part of a product risk assessment.