Notes on the Chart in Excel File AwNEqnWB

Charting the Results

The following paragraphs describe the cells of Sheet2 used to produce the chart of the mixture modeled in the demonstration worksheet. The chart is plotted using Excel's XY (Scatter) chart type.

InitAw (cells H4:H18) are copies of Sheet1 cells D4:D18 and contain the initial water activity (Aw) value of each ingredient. These are the x-coordinates of the triangle markers on the graph.

InitMoist (cells I4:I18) are copies of cells C4:C18 and contain the initial moisture value of each ingredient. These are the y-coordinates of the triangle markers on the graph.

EqAw (cells J4:J18) are copies of Sheet1 cell $D$2, the equilibrium water activity (AwStar). These are the x-coordinates of the square markers on the graph. A $ precedes an absolute row or column reference (which does not change when copied and pasted).

EqMoist (cells K4:K18) are copies of Sheet1 cells H4:H23 and contain the final (equilibrium) moisture value of each ingredient. These are the y-coordinates of the solid square markers on the graph.

AwStarX (cells L4:L5) are copies of Sheet1 cell $D$2, the equilibrium water activity (AwStar). These are the x-coordinates of the vertical light blue line on the graph. A $ precedes an absolute row or column reference (which does not change when copied and pasted).

Aw* (cells M4:M5) are the y-coordinates of the vertical light blue line on the graph. The y-coordinate in cell M4 is the minimum y-axis value shown on the graph (0) and the y-coordinate in cell M5 is the maximum y-axis value shown on the graph (50).

Aw (cells N4:N103) are the x-coordinate values of the moisture sorption isotherm curves plotted for each ingredient. Cell N4 is set to the minimum value shown on the x-axis of the graph (0). An increment of 0.01 is added to each succeeding value so that 100 points will be used to plot the curves. Cell N103 is set to 0.99 and is 0.01 less than the maximum value (1) shown on the x-axis of the graph. This prevents a division-by-zero error that occurs if certain model equations are calculated using a value of 1 for Aw.

Black (cells O4:O103) are the y-coordinates of the moisture sorption isotherm curve for the first possible ingredient. They are found by calculating the equation for that ingredient using the Aw values found in cells N4 to N103. The black color of the curve and markers on the graph matches the black background color in Sheet1 cells D4 through H4 where the user made entries for that ingredient. The column name in cell O3 specifies the label for the black curve used in the graph's legend and is a copy of the ingredient name that the user entered in Sheet1 cell E4. The above remarks on column O also apply to the remaining Sheet2 columns (P through AC) for the other 14 possible ingredients.

Excel water activity worksheet download page