Relationships between wheat flour baking properties and tensile characteristics of derived thermoplastic films

Abstract

This work was aimed at defining models to explain tensile properties of thermoplastic films derived from common wheat flours as a function of source flours characteristics. A total of 26 flours, two blends from an industrial mill and 24 single-cultivar flours collected over three different years of grain production (from 2013 to 2015) and cultivar grain hardness (from soft to hard) were used in a wide range of protein content (from 9.0 to 16.2%) and values of Chopin's alveograph parameters (as indexes of gluten characteristics), i.e., P (from 27 to 160mm), L (from 32 to 236mm), P/L (from 0.13 to 4.44), and W (from 63 to 398). The same plasticization recipe and filming procedure was adopted for all manufactures. The maximum tensile strength (σmax) and the elongation at break (εmax), as well as the elastic modulus (E), stiffness (k) and energy at break (wb) of films from flours having moderate to high values of P (>60mm), P/L (≥0.43) and W (>170) were positively correlated to P and negatively correlated to P/L and W, with all the variables significant (p-value <0.05) and R2=0.72 for σmax, 0.62 for εmax, 0.81 for E, 0.83 for k and 0.72 for wb. The εmax of films obtained from flours having moderate to low values of P (≤45mm), P/L (≤0.42) and W (≤160) was negatively correlated to P, L and P/L, and positively correlated with W, with all the variables significant (p-value <0.05) and R2=0.86. On the contrary, no relationship was found for the σmax, as well as for E, k and wb of these films. Results encourage further research aimed at improving the robustness and reliability of models so that tensile properties of a thermoplastic film can be predicted for any given source flour.