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Recipe aw
Program
This page is from the
Recipe Water Activity Program on-line help.
Contents
- Program Description
- Ross Equation
- Isotherm
- Norrish
- Raoult's Law
- Grover
- Sugar Equivalent
- Using the Program
- Make Changes
- Print Recipe
- Ingredients Database
- Recipe Database
This program estimates the aw
for a mix of ingredients, at a specified final moisture or the
initial moisture.
The program uses the Ross Equation to
calculate an estimation of the water activity of a food
formulation. This equation assumes that each ingredient is
dissolved in all the water present in the mix, including added
water and moisture in the ingredients.
The aw
of each of the ingredients must be calculated individually to use
the Ross equation.
Individual aw's may
be calculated by any of the following methods:
The GAB parameters for the isotherm
may be calculated using the Isotherm Program.
Refer to the
Isotherm Program Page
for further information.
The Norrish equation is used for
solutions, and is valid when the molecular weight and the Norrish
k value are known.
Refer to the
Norrish Program Page
for further information.
Raoult's Law applies to solutions of
small molecular weight compounds for which the calculated aw
>0.95
aw
= A nH2O
/(nH2O+
nsolute)
where:
-
A = activity coefficient
-
nH2O
= moles of water in solution (assumed to be 1 for solutions with
aw >0.95)
-
nsolute=
moles of solute
The Grover equation is a polynomial
fit that has been established for confectionery ingredients.
-
aw
=1.04 - 0.1Es
+ 0.0045(Es)²
-
Es
= ∑ (Ei
/ mi)
-
mi
= g H2
O / g
solids of component i
The sugar equivalent method works on
the basis that a material has the same effect on water activity
as an equivalent quantity of sucrose.
For example, baking
powder has an SE (sugar equivalence) of 3. This means that 1g of
baking powder would have the same effect as 3g of sucrose.
All functions of this program are
accessed from the "Program menu". This menu contains
the following options:
This allow you to add or delete
ingredients from the recipe, and change the quantity and moisture
content of ingredients used.
A dialog box shows ingredients
selected for the recipe.
Functions:
The aw
will be calculated.
The effect on aw of
increasing each ingredient by 1% will also be calculated.
The recipe is printed, together with
isotherms and calculated data
This option is to view or maintain the
ingredients database.
Functions:
This option allows you to maintain the
recipe database. Functions:
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