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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

Program Description

This program estimates the aw for a mix of ingredients, at a specified final moisture or the initial moisture.

 

Ross Equation

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 a
w's may be calculated by any of the following methods:

Isotherm

The GAB parameters for the isotherm may be calculated using the Isotherm Program.

Refer to the Isotherm Program Page for further information.

Norrish

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

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

Grover

The Grover equation is a polynomial fit that has been established for confectionery ingredients.

aw =1.04 - 0.1Es + 0.0045(Es)
Es = (Ei / mi)
mi = g H2 O / g solids of component i

Sugar Equivalent

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.
 

Using the Program

All functions of this program are accessed from the "Program menu". This menu contains the following options:

Make Changes

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 a
w of increasing each ingredient by 1% will also be calculated.

Print Recipe

The recipe is printed, together with isotherms and calculated data

Ingredients Database

This option is to view or maintain the ingredients database.
Functions:

Recipe Database

This option allows you to maintain the recipe database. Functions:

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Last modified: 10-Aug-2008