Geraniol and cinnamaldehyde as natural antibacterial additives for poly(lactic acid) and their plasticizing effects

Abstract

<jats:title>Abstract</jats:title> <jats:p>The main goal of this study is to prepare antibacterial poly(lactic acid) (PLA) containing cinnamaldehyde and geraniol and to evaluate the antibacterial activity and assess the changes of physical properties of the PLA films. Cinnamaldehyde- and geraniol-incorporated (10%, 20%, 30%, and 50% v/w) PLA films were prepared via solution-casting. While preparing these films, plasticizers were not added to the matrix. Antibacterial activities of these films against <jats:italic>Escherichia coli</jats:italic> and <jats:italic>Staphylococcus aureus</jats:italic> were investigated by the disk diffusion method. Thermal degradation characteristics were analyzed via thermogravimetric analysis (TGA), glass transition, crystallization, and melting temperatures, and enthalpies of the films were determined from differential scanning calorimetry (DSC) scans. Tensile strength and elongation-at-break values of neat PLA and antibacterial-compound-containing films were evaluated and compared after the mechanical tests. Moreover, the changes in the polymer morphology were observed by SEM analysis, and opacity of the films was determined by UV-vis spectroscopy. Our results showed that both compounds provided antibacterial effect to the PLA, with cinnamaldehyde being more effective than geraniol. Moreover, plasticization effects of the compounds were confirmed by DSC analysis.</jats:p>

Immobilization of Caraway Essential Oil in a Polypropylene Matrix for Antimicrobial Modification of a Polymeric Surface

“…Similar results were described by Llana-Ruiz-Cabello [ 23 ] in a study on PP films supplemented with oregano EO and allium extract intended for the packaging of meat products. This highlights that EOs not only provide an antibacterial function but also heighten the flexibility of PP composites which contain reinforcing fillers [ 28 ]. The improved mechanical properties can be also caused by the TC surface modification with EO considering that the modification of TC surface with EO presumably increases TC surface hydrophobicity and thus improves the interaction strength at the PP/TC interface.…”

“…The melting temperature (T m ) and the exothermal response relating to cold crystallization (T c ) were obtained from the second heating cycle. The degree of crystallinity ( X C ) was calculated from the value for specific enthalpy of melting (Δ H f ), as determined from the area under the melting peak in the second scan, applying the theoretical enthalpy of melting for 100% crystalline PP (209 J/g); see Equation (1) below [ 26 , 27 , 28 ]. where Δ H° f is the theoretical enthalpy of melting for 100% crystalline PP, and W is the weight fraction of PP in the composite.…”

“…Nitrogen flow was set to 50 mL/min., and the following heating program was applied: an initial heating cycle from 25 • C to 200 • C (10 • C/min), maintaining the same for 2 min, and subsequent cooling to −50 • C (20 • C/min); this temperature was maintained for 2 min prior to conducting another heating scan to 200 • C. The melting temperature (T m ) and the exothermal response relating to cold crystallization (T c ) were obtained from the second heating cycle. The degree of crystallinity (X C ) was calculated from the value for specific enthalpy of melting (∆H f ), as determined from the area under the melting peak in the second scan, applying the theoretical enthalpy of melting for 100% crystalline PP (209 J/g); see Equation (1) below [26][27][28].…”

Natural Antimicrobials as Additives for Edible Food Packaging Applications: A Review

“…Among the biodegradable polymers, poly(lactic acid) (PLA) has received great attraction as it can be easily degraded by hydrolysis and enzymatic reactions without leaving harmful or toxic residuals.The Food and Drug Administration has also approved this biopolymer as safe, being produced from renewable products such as corn and sugarcane. It bears superior mechanical properties similar to PS and PET with an additional advantage of biodegradability [125].…”

“…Essential oils, frequently employed in edible coatings as antibacterial agents, are categorized and registered as GRAS by the European Commission and the United States, may cause allergic reactions and oral toxicity [127]. Therefore, it is necessary to balance the effectiveness of essential oil or plant extract dose and the risk of their toxicity [121,125]. Overall, since edible films and coatings become part of the food to be consumed, all materials used in these products must be appropriately declared on the label [128].…”