The rotatable central composite design was applied to identify
the influence of two variables, the applied voltage (V) and the total
solids content of the blueberry pulp (g/100 g), on the percentage of
anthocyanin degradation (response variable). The coded and
uncoded independent variables used in the experimental design
are listed in Table 1. Voltage ranges (X1) were selected based on the
limitations of the ohmic heating system, and the range of the solids
content (X2)was chosen based on the characteristics of the fruit and
the stability of the diluted suspension. To determine the influence
of the selected parameters on the response variable, experiments
were planned according to the central composite design (CCD)
using a 22 full factorial and star design with three central points, as
shown in Table 2. For the ohmic heating experiments, the error
between independent experiments was determined using the
central points of the rotatable central composite design.
Multiple linear regression analysis was performed using