Thermo-resistant films based on core-shell nanofibers loaded with phase change materials for butter packaging; fabrication, characterization, application

Abstract

Shelf life of butter, as an important dairy product in the human diet, can be limited due to light, temperature, and humidity during storage, which makes this product susceptible to oxidation, lipolysis, and microbial spoilage. Therefore, to address challenges related to the shelf life of butter by enhancing the thermo-resistance of its packaging and increasing its stability at ambient temperature, in this research, thermoplastic polyurethane (TPU) nanofibers containing bio-waxes of soy, coconut, carnauba, bees, and spermaceti as phase change materials were designed through coaxial/melt electrospinning technique. Our results revealed that when waxes were loaded inside the nanofibers, $\Delta H_m$ value became lower than pure waxes. Core-shell nanofiber consisting of 15 % (w/w) TPU (as the shell) and 30 % (w/v) carnauba wax (as the core) with an average diameter of 241.1 ± 7 nm was chosen as the best sample due to good thermal properties (i.e., T_m = 54.7 °C, $\Delta H_m$= 88.6 $\frac{J}{g}$, and ΔC_p = 8.16 $\frac{J}{gK}$) and the highest nanoencapsulation ratio. The designed nanofibers can be used as a thin and effective insulating layer, enhancing the thermo-resistance of traditional packaging. They successfully protect butter against environmental changes (i.e., temperature fluctuations), leading to a significant extension of its shelf life.