What is the biological AW value? What does aw mean in biology?

The aw value refers to water activity.

Value: The minimum water activity value required by various microorganisms is different. Bacteria, molds, and yeasts.

Among the three major types of microorganisms, the minimum AW required by general bacteria is higher, in; The minimum AW required for mold and the minimum AW required for yeast is. However, some dry molds, such as Aspergillus griseus, have a minimum aw of only (water content.

16%), and some food water activity values are about 16% in water content) Aspergillus and Penicillium can grow, so it is safer to have a mildew resistance value of dried food below (water content of 12% or less than 14%). Fresh foods such as milk, meat, fish, eggs, fruits, vegetables, etc. have high moisture, and their water activity value is generally high, which is suitable for the growth of a variety of microorganisms. At present, the moisture of mildew-proof dried food is generally 3 25%, such as 15 25% for dried fruits, less than 4% for dried vegetables, and 5 10% for dried meat products, spray dried.

Milk powder is less than 5% spray-dried egg powder.

The part of water that can be used by microorganisms is also called wateractivity (wateractivity abbreviated as AW), and the closer AW is to 1, the most likely for microorganisms to grow and reproduce.

1. Effect on microorganisms. The AW value reflects how well water binds to food and how effectively it is used by microorganisms. The growth and development of various microorganisms has its optimal AW value, and when the AW value decreases, their growth rate also decreases, and finally, the AW can drop to the level where the microorganism stops growing.

AW can alter the sensitivity of microorganisms to heat, light, and chemical agents. In general, microorganisms are most sensitive at high AW and least sensitive at moderate AW. Microorganisms require different AW values at different stages of growth.

Bacteria form spores higher than they reproduce and grow. 2. Effect on enzymes Enzyme activity increases with the increase of AW, and usually reaches the maximum in the range of AW. At AW<, enzyme activity decreases or decreases, but to inhibit enzyme activity, AW should be below.

3. Influence on other reactions 1. Fat oxidation: AW can not inhibit the oxidation reaction, even if the water activity is very low, the food containing unsaturated fatty acid is very easy to oxidize rancidity in the air, and even the water activity is lower than that of the monolayer water. 2. Non-enzymatic browning

AW also does not completely inhibit the reaction. Due to the difference in food composition, even if the same food and processing technology are different, the most water activity that causes browning is also different. 3. Effect of AW on starch aging:

When the aw is high, the starch is easy to age, and if the aw is low, the starch aging is not easy to carry out. 4. The increase of AW will accelerate the oxidation of protein: when the moisture content reaches 4%, the deformation of protein can still be carried out slowly, and if the moisture content is less than 2%, it is not easy to denature.

"AW" is an abbreviation for "airwatts", which means, air watts or air watts.

AW suction is called pneumatic power to produce suction.

The formula is airwatts (aw) = vacuum suction inches of water * air flow cfm.

"Extended Materials":

AW suction is called pneumatic power to produce suction, and kpa suction power is usually used to indicate the suction power of the vacuum cleaner.

In vacuum cleaners, if you want to test the continuous working ability of the vacuum cleaner, you need to use the AW value, KPA can not be expressed, like the Dyson vacuum cleaner is different from other vacuum cleaners is only marked with the AW value.

The vacuum cleaner also measures the following: power (watts), suction power (watts), flow rate (liters and minutes l min);

KPA is the size of the negative pressure generated by the machine, and the vacuum cleaner is the vacuum cleaner

The AW value of a vacuum cleaner is called airwatts, which means air watts or air watts. The performance of the vacuum cleaner is better reflected than the power of the product itself. The machine is set up at the factory and tested for pneumatic power, which can reflect the dust suction capacity in the real use process.

"AW" is an abbreviation for "airwatts", which means, air watts or air watts.

The formula is airwatts (aw) = vacuum suction inches of water * air flow cfm

Vacuum suction inches of water and vacuum kpa are both vacuum, but the unit of measurement is different, just like buying a bull's head, one is measured in 'pounds' and the other is measured in 'kg', vacuum suction inches of water and vacuum kpa can be converted.

So airwatts(aw) = vacuum suction inches of water*air flow cfm

Vacuum Suction KPA* Air Flow CFM

However, in this formula, the vacuum suction and air flow are the actual measurements, both of which are taken at the same time during each measurement, so there is no way to deduce how much kPa is needed from a unit AW

AW is the annual value, and the mutually exclusive scheme uses this evaluation criterion: if it is a comparison of income indicators, which scheme has the largest annual value, choose which; If it is a cost indicator, which annual value is the best solution.

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Water activity (AW) refers to the ability of microorganisms to use water.

Most bacteria, including those that are clearly associated with public health, generally do not grow at or below water activity.

Therefore, it follows from the above that the AW value required for the growth of most bacteria should be greater than that.