A grid with a defined pixel spacing is added to the image in the form of an overlay. It is important to realize that a photographic image and a hand drawn grid overlay are equally effective for stereological measurement. Computer generated overlays can be used in imaging packages such as Adobe Photoshop as well as in conjunction with image analysis software. The points are marked, either with a pen or mouse, where the grid intersects the image feature to be quantified. The number of counts are used together with the number of grid points, the dimensions of the grid and the image area to derive stereological values.
Dots mark the intersection between the vertical grid lines and the bubble interface.
All foam images were collected at the same magnification and the dimensions of the image were calibrated using a copper grid of defined dimension. Intersection points between the vertical lines of the grid and the bubbles were marked using the mouse as shown in Figure 1. The measurement of volume fraction of air bubbles in the foam will quantify the change in foam structure over time and allow for the evaluation of the effect of different treatments on foam stability. The purpose of stereological measurement was to evaluate the effect of the choice of heat treatment and the addition of stabilizer on structural stability of whipped creams. Freshly whipped cream was compared with the foam which had been stored for 24 hours.