Determination of a representative area element (RAE) based on nonparametric statistics in bread

The concept of representative area element (RAE) was applied to quantify the air cell present in pre-sliced bread. Ten slices from bread were selected and each divided into nine subareas where 60 air cells were measured. To determine the RAE, one to nine sampling areas were considered and five positions in the image were randomly selected and compared by nonparametric statistic and the fluctuation of mean air cell area method. The RAE was attained when the air cell area size distribution curves for each sampling area did not present significant differences. Hence, the RAE size was 67% of the image using the nonparametric method (equivalent to six subareas of the nine subareas that form the image), whereas the RAE could not be estimated using the fluctuation of mean air cell area method. Therefore, nonparametric statistics are a useful tool to determine the RAE in structures with size distributions that do not fit a normal distribution.