Effect of Mesoporous Silica Nanoparticles on The Physicochemical Properties of Pectin Packaging Material for Strawberry Wrapping

Abstract

Citrus peel pectin was used to prepare films (cast with or without glycerol) containing mesoporous silica nanoparticles. Nanoparticles reduced significantly the particle size, and had no effect on the Zeta potential of pectin solutions. Mechanical characterization demonstrates that pectin+nanoparticles containing films slightly increased tensile strength and significantly decreased the Young's modulus in comparison to films made only of pectin. However, elongation at the break increased in the pectin+nanoparticles films cast in the presence of glycerol, while both Young's modulus and tensile strength were reduced. Moreover, nanoparticles were able to reduce the barrier properties of pectin films prepared with or without glycerol, whereas positively affected the thermal stability of pectin films and the seal strength. The 0.6% pectin films reinforced or not with 3% nanoparticles in the presence of 30% glycerol were used to wrap strawberries in order to extend the fruit's shelf-life, over a period of eighty days, by improving their physicochemical properties.

Keywords: biodegradable films; food packaging; mesoporous silica nanoparticles; pectin; wrapped strawberries.

Figure 1

Effect of different pHs on the Zeta potential and Z-average size of 0.1% PEC-based and 3% MSN water solution (Panel A), and of 0.1% PEC-based FFS (prepared in the presence of 30% GLY (w/w with PEC) or 3% MSNs (w/w with PEC) or in the presence of both 3% MSNs and 30% GLY (Panel B).

Figure 2

Effect of pectin (PEC) concentration on thickness and mechanical properties of films prepared at pH 7.5 in the presence or absence of mesoporous silica nanoparticles (MSNs) or glycerol (GLY) or in the presence of both. The values, significantly different from those obtained by analyzing the Viscofan NDX edible film (white bars) (Data from Porta et al. [54]), are indicated by “a”, while the values indicated by “b” were significantly different from those obtained by using only PEC (p < 0.05). Further experimental details are given in the text.

Figure 3

Effect of different concentrations of MSNs and GLY on thickness and mechanical properties of 0.6% PEC films (Panel A) and 1% PEC films (Panel B), both prepared at pH 7.5. The values significantly different from those obtained by analyzing Viscofan NDX (white bars) (Data from Porta et al. [54]), are indicated by “a”, while the values indicated by “b” were significantly different from those obtained by analyzing films made of either only PEC or the one obtained with GLY (p < 0.05). Further experimental details are given in the text.

Figure 4

Seal strength of 0.6% PEC film prepared with or without 3% MSNs (w/w PEC), 30% GLY (w/w PEC) or in the presence of both (Panel A) and 1% PEC film prepared with or without 1% MSN (w/w PEC), 50% GLY (w/w PEC) or in the presence of both (Panel B). All the films were prepared at pH 7.5. The values significantly different from those obtained by PEC only (0.6% or 1%) are indicated by “a”, while the values indicated by “b” were significantly different from those obtained by only adding GLY (p < 0.05).

Figure 5

Thermogravimetric analysis (TGA) and differential thermal gravimetry (DTG) of 0.6% PEC film prepared at pH 7.5 with or without 30% (w/w PEC) GLY, 3% MSNs (w/w PEC) or with both (Panel A) and 1% PEC film prepared with or without 50% (w/w PEC) GLY, 1% MSNs (w/w PEC) or with both (Panel B).

Figure 6

Differential Scanning Calorimetry (DSC) thermograms of 0.6% PEC film prepared with or without 30% GLY (w/w PEC), 3% MSNs (w/w PEC) or in the presence of both (Panel A) and of 1% PEC film prepared with or without 50% GLY (w/w PEC), 1% MSNs (w/w PEC) or in the presence of both (Panel B). All the films were prepared at pH 7.5.

Figure 7

Effect of wrapping with pectin films on weight loss % (A), pH (B), and titratable acidity (C) of strawberries stored for several days (0–8 days). * indicates statistically significant differences at p < 0.05 compared to the unwrapping group (UW) used as a control, and to samples wrapped with Mater-Bi^®.

Figure 8

Effect of wrapping with pectin films on ascorbic acid content (A), and antioxidant activity (B) of strawberries stored for several days (0–8 days). * indicates statistically significant differences at p < 0.05 compared to the unwrapping group (UW) used as a control and to samples wrapped with Mater-Bi^®.

Figure 9

Images of unwrapped and wrapped groups of strawberries during storage time (days).