deletions | additions       diff --git a/sectionColorimetric_.tex b/sectionColorimetric_.tex  index 4d3de54..8ae6e35 100644  --- a/sectionColorimetric_.tex  +++ b/sectionColorimetric_.tex 
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where \textit{w} is the weight gain; $\theta$ is the time during which \textit{w} occurred (hr); \textit{t} is the sample thickness (mm); \textit{A} is the test area (m$^2$); and $\Delta$\textit{p} is the vapour pressure difference (kPa).  For Swelliing Swelling  Index (SI) assay, the samples are cut into slices and then kept in a desiccator with silica-gel until constant weight. After this procedure the samples are weighed and then subjected to immersion in beakers containing distilled water for different time intervals at room temperature. At each time interval, samples are removed, dried and weighed. The Swelling Index (SI\%) is calculated according to Equation \ref{eqn:swell}: \begin{equation}  SI\% = \frac{Final Weight - Initial Weight}{Final Weight} \cdot 100   \label{eqn:swell}  \end{equation}  \par  \subsubsection{Mechanical Properties}  Good mechanical properties is expected for application of thin polymeric films in food packaging. Tensile strength, elongation at break and Young’s modulus are measured to determine the mechanical properties of these films. It is expected that a good biopolymer film for food packaging applications has mechanical properties comparable to those of commercially available polymers. These mechanical properties are measured using the method described in ASTM D1708-10, which is suitable for determining the mechanical properties of plastics or the traction of films with thicknesses ranging from 0.0025 mm to 2.5 mm, which is sufficient for the application in food packaging.\par\par  \subsubsection{Dynamic Parameters of Colour}  A colourimetric sensing film must have its colour parameter evaluated. The colour parameter indicatas how the film colour changes and if these changes can be detected with naked eyes. Thus, this is an imporant parameter to be evaluated. Briefly, thee colour parameters of the film is determined with a UV-Vis colour measurement spectrophotometer. Tests are performed in triplicate and the total colour values of L* (lightness), a* (red - green) and b* (yellow - blue) are registered. The colour differences are obtained according to Equation \ref{eqn:colour}:  \begin{equation}  \Delta{E} = ((\Delta{L}*)^2 + (\Delta{a}*)^2 + (\Delta{b}*)^2)^\frac{1}{2}  \label{eqn:colour}  \end{equation}  Where $\Delta{L}* = L* - L_0*$, $\Delta{a}* = a* - a_0*$ and $\Delta{b}* = b* - b_0*$. $L_0*$, $a_0*$ and $b_0*$ are the initial colour values of sensing films.