Digital external micrometer

The samples were conditioned at 25 °C for 24 h, and the thickness of the edible films (EFs) was measured (exactness of ± 0.001 mm) using a digital external micrometer (Mitutoyo Co., Kawasaki, Japan) at 10 different points of the film. Averaged thickness values were obtained and used in all calculations.

Thickness of film was measured by digital external micrometer (Mitutoyo Co., Kawasaki, Japan) and the overall thickness was expressed as an average generated randomly from each film at 15 different points.
The transmittance (%) of the films was measured by a Shimadzu UV-2500 spectrophotometer (Tokyo, Japan). Film was cut into 1 × 4 cm rectangular pieces. Then the cut films were fixed to one side of a spectrophotometer cell. An empty cell was used as control. Three duplications were performed for each film to guarantee the accuracy. The transparency of sample was measured at 600 nm. Relative transparency, which was an approximation, was calculated according to Formula (1): $\mathrm{Transmittance}(\%)=(\frac{T_{600}}{\mathrm{d}})\times 100$
where T₆₀₀ is transparency of the film at 600 nm; d is the averaged thickness (mm).
A Minolta colorimeter (Cr 410, Konica Minolta, Tokyo, Japan) was used to measure the color parameters of the films with a standard white plate applied for calibration. The results were expressed according to the CieLab color system, where L* was 0 for black and 100 for white, a* represented red (+) to green (−), and b* values indicated yellow (+) to blue (−). The mean values were then calculated.

In this experiment, three CS (p-CM, p-ADM, a-ADM) were cut to a size of 15 × 20 mm, with three samples (n = 3) of each matrix prepared. Dimensions (length, width and height) were measured at the highest point of the samples using a digital external micrometer (Mitutoyo, Urdorf, Switzerland) at the first visual contact. A pencil line was drawn on each matrix 2 mm from the bottom edge. The prepared samples were vertically mounted on a sample holder attached to a XS204 DeltaRange® scale (Mettler, Greifensee, Switzerland) (Fig. 1). A vessel containing PBS was placed on the balance plate and the bottom 2 mm of each matrix was immersed in PBS. The time and mass change from the immersion of the matrix in the solution until the solution reached the top of the matrix were assessed. Once the matrix appeared fully swollen, the balance plate was lowered, so that the matrix was no longer in contact with the solution. After this, weight change was recorded for an additional 2 min to measure any evaporation. The liquid absorption capacity per volume was calculated by subtracting the mass of the dry matrix from the mass of the swollen matrix and then dividing by the volume of the matrix.Fig. 1

Scheme of the experimental setup