Development of psyllium seed husk-based colorimetric indicator by different homogenization methods

Intelligent packaging with a pH indicative property has gained so much importance for real time monitoring of food quality. Natural pigments could be considered as very promising candidates as compared to toxicity debatable synthetic ones. They are also highly valuable for active packaging design due to their antioxidant and eco-friendly properties and low-cost values. This study brought sumac extract (SC) to the forward as a film material and a new active edible film formulation was developed by psyllium husk powder (PSY) incorporating with SC through different homogenization methods (stirring, high-speed homogenization and ultrasonication). Sumac addition into film formulation increased antioxidant activities regardless of process conditions. On the other hand, they showed differences in physicochemical properties. The lowest values in moisture content, swelling degree and water permeability were obtained in the film prepared by ultrasonic treatment, but it gave the highest opaque, most heterogeneous and dense structure. Overall, high-speed homogenization treatment displayed optimum results. FTIR spectra confirmed the changes in -OH bending vibration in the presence of sumac with the loss of peak at around 1213 cm(-1). For pH sensitivity, PSY-SC films displayed color differences from purple to brown at pH 2.0-12.0. Thus, sumac fortified edible PSY-based film could be proposed as a colorimetric indicator for pH-sensitive and active food packaging material.