Short‐ and long‐term loss of carvacrol from polymer/clay nanocomposite film – a chemometric approach

Abstract

A combination of partial least squares (PLS) regression and design of experiments was used to analyse and define the shortand long-term loss mechanisms of carvacrol from polymer/clay nanocomposite films used as an antimicrobial food packaging material. Three formulation x variables were evaluated: type of nanoclay, concentration of nanoclay and concentration of compatibilizer agent. Five experimental y responses were measured: loss of carvacrol from the films stored at room conditions on the third and fifth days (short-term loss); on the forty-fifth and sixtieth days (long-term loss); and the polymer/clay level of intercalation. All variables and responses were simultaneously calibrated by an ANOVA-validated (P < 0.05) comprehensive PLS interaction model with a satisfactory R 2 = 0.956 and Q 2 = 0.505. A differentiation and discrimination of the mechanisms that control the loss of carvacrol over different periods of time was observed. Short-term loss seems to be controlled mainly by direct molecular interactions in the interlayer space between carvacrol and the nanoclay organomodifier. Long-term loss seems to be mainly controlled by diffusion within the nanocomposite matrix once carvacrol has left the nanoclay interlayer space, and it is closely related to the levels of intercalation reached in the nanocomposite.

Antimicrobial films containing hybrid systems aiming at packaging applications

“…Nanoclay, especially montmorillonite (used in this work), has a lamella structure; therefore, the EOs can be inserted between the nanoclay lamellae. [23][24][25][26] Besides, to extend and control the time of bacterial action, these oil carrier systems can be used to protect the oil, resulting in an improvement of thermal stability and mechanical properties during processing by extrusion. 23,24,27 According to the literature, nanocomposites (PE/clay/EOs) containing low-density polyethylene (LDPE), nanoclay and EOs show high antimicrobial activity against Escherichia coli, Listeria innocua, Staphylococcus aureus and Bacillus cereus.…”

“…In this case, the antimicrobial activity occurred with efficiency for Gram-positive foodborne disease bacteria (S. aureus and Listeria monocytogenes) applying the EO at 0.4-1.2 wt%. 17,[23][24][25]27,28 Generally, literature work has evaluated the antimicrobial properties of well-known EOs at high concentrations in a polymer-clay matrix. Taking account that the concentrations are higher than the minimal inhibitory concentration of EOs, there is still a lack of knowledge about whether lower concentrations of EOs can be incorporated in clay mineral and a known polymer matrix, keeping the antimicrobial effect against Gram-negative foodborne disease bacteria.…”

“…Among the carrier agents, nanoclay can be mentioned. Nanoclay, especially montmorillonite (used in this work), has a lamella structure; therefore, the EOs can be inserted between the nanoclay lamellae 23–26 . Besides, to extend and control the time of bacterial action, these oil carrier systems can be used to protect the oil, resulting in an improvement of thermal stability and mechanical properties during processing by extrusion 23,24,27 …”

“…Similar results were observed by Hosseini et al ., where carvacrol was incorporated in chitosan and fish gelatin by casting methods. In this case, the antimicrobial activity occurred with efficiency for Gram‐positive foodborne disease bacteria ( S. aureus and Listeria monocytogenes ) applying the EO at 0.4–1.2 wt% 17,23–25,27,28 . Generally, literature work has evaluated the antimicrobial properties of well‐known EOs at high concentrations in a polymer–clay matrix.…”

Mechanical and Morphological Properties of Poly(3-Hydroxybutyrate)-Thermoplastic Starch/Clay/Eugenol Bionanocomposites

“…13 The clays not only improve the mechanical, thermal and barrier properties of the polymers but also make it possible to encapsulate active ingredients, which give new features to the polymers such as antioxidant, antibacterial or antifungal activity. [14][15][16][17][18] Essential oils are active ingredients that manage to deliver antioxidant, antibacterial and antifungal activity at the same time. Among the most used essential oils are carvacrol, thymol, and eugenol, which have been used in bionanocomposites of clay, where it has been proven that it maintains its excellent antifungal properties against Botrytis cinerea.…”