Ciencias Exactas y Ciencias de la Salud

Biopolymer films can prevent food spoilage and maintain the safety of packaged foods, while representing an alternative to reduce the consumption of synthetic plastics. However, their natural origin results in unstable properties over time. Therefore, it is necessary to extend the study of biopolymer films and determine their viability as packaging materials during storage in defined conditions. In this context, the present work investigated the effects of storage for eight weeks at 5, 25, 35 ° C and 75 % of relative humidity (RH) on the mechanical properties, water vapor permeability (WVP), color, morphology, and chemical structure of pectin-based films with SiO2 and corn starch. In general, the evaluated temperature and time of storage had a significant effect (p-value < 5%) on the studied properties of pectin-based films after storage (at t8). At t8, the tensile strength (TS) decreased 38.71, 33.8, and 23.3 % at 5, 25, and 35 ° C, respectively. The elongation at break (EAB) increased 21.9 and 15.8 %, while the elastic modulus (EM) decreased 54.31 and 24.61 % at 5 and 25 ° C, respectively. Furthermore, the WVP of the studied films increased 38.3 and 18.0 % at 5 and 25 ° C, respectively. The effect of temperature on the WVP at t0 and at t8 followed an Arrhenius relationship. The activation energy of water vapor permeation of pectin-based films at t0 was -4.07 kJ mol-1, which decreased to -9.2 kJ mol-1 at t8. The color of the studied films turned brown at all evaluated temperatures at t8. The browning of the films was more pronounced with increasing temperature of storage. The coordinate L* decreased 1.4, 7.1, and 14.6 % at 5, 25, and 35 ° C, respectively. Whereas an inverse behavior was observed in the coordinate a* as it increased 43.7, 95.2, and 152.7 % at 5, 25, and 35 ° C, respectively. The coordinate b* decreased 31.4 % at 5 ° C, however, an increase of 26.1 and 52.7 % was observed at 25 and 35 ° C, respectively. The total color difference (ΔE) increased 540, 403, and 358 % at 5, 25, and 35 ° C, however higher magnitudes were detected with increasing temperature of storage. In contrast, the hue angle (h°) was observed to decrease 2.7, 10.2, and 15.2 % at 5, 25, and 35 ° C, respectively. The yellowness index (YI) displayed a reduction of 30.5 % at 5 ° C, and an inverse behavior at 25 and 35 °C as it increased 35.8 and 79.2 %, respectively. The color change kinetics of pectin-based films were studied as a function of storage time. The effect of different temperature of storage was evaluated on the color kinetics. The changes in color parameters were fitted to zero and first-order models. The zero-order model was selected as it showed the best fit (R2 > 0.88) to the experimental data. Also, the effect of temperature on the color kinetics followed an Arrhenius relationship. The color change activation energy of all color parameters during storage ranged from 10.27 to 54.42 kJ mol-1. Data suggests that the resultant modifications in the properties of the studied films were related to chemical and physical alterations within the pectin-matrix. These alterations occurred by the accumulation of water molecules in pectin-based films during storage. Furthermore, the resultant color changes were related to non-enzymatic browning (NEB) reactions and to the degradation of carotenoids during storage at all conditions. For the first time, the modifications in the properties of pectin-based films during storage were quantified. Although the properties of the studied films were altered, they maintained their macroscopic integrity during storage. Which suggests that the performance of pectin-based films as packaging materials would remain functional during extended storage. Therefore, the quantification of the observed alterations in the properties of pectin-based films could provide relevant data towards the shelf-life estimation of target food products.

Ciencias Exactas y Ciencias de la Salud

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