Abstract
The new trend in food packaging films is to use biodegradable or bio-based polymers, such as poly(lactic acid), PLA with additives such as thymol, carvacrol, limonene or cinnamaldehyde coming from natural resources (i.e., thyme, oregano, citrus fruits and cinnamon) in order to extent foodstuff shelf-life and improve consumers’ safety. Single, triple and quadruple blends of these active compounds in PLA were prepared and studied using the solvent-casting technique. The successful incorporation of the active ingredients into the polymer matrix was verified by FTIR spectroscopy. XRD and DSC data revealed that the crystallinity of PLA was not significantly affected. However, the Tg of the polymer decreased, verifying the plasticization effect of all additives. Multicomponent mixtures resulted in more intense plasticization. Cinnamaldehyde was found to play a catalytic role in the thermal degradation of PLA shifting curves to slightly lower temperatures. Release of thymol or carvacrol from the composites takes place at low rates at temperatures below 100 °C. A combined diffusion-model was found to simulate the experimental release profiles very well. Higher antioxidant activity was noticed when carvacrol was added, followed by thymol and then cinnamaldehyde and limonene. From the triple-component composites, higher antioxidant activity measured in the materials with thymol, carvacrol and cinnamaldehyde.
Highlights
The main function of food packaging is to maintain the quality and safety of food products during storage and transport and to extend their shelf life by preventing impacts from unfavorable factors or conditions, such as spoilage microorganisms, chemical contaminants, oxygen, moisture, light, and external force
The amount of thymol, carvacrol, limonene or cinnamaldehyde present in the formulations after processing appear in Table 2 in terms of loading capacity and encapsulation efficiency as defined in Equation (1)
In this research several bio-composites of poly(lactic acid), PLA, with ingredients found in thyme, oregano, citrus fruits and cinnamon, namely thymol, carvacrol, limonene and cinnamaldehyde were prepared and studied
Summary
The main function of food packaging is to maintain the quality and safety of food products during storage and transport and to extend their shelf life by preventing impacts from unfavorable factors or conditions, such as spoilage microorganisms, chemical contaminants, oxygen, moisture, light, and external force. Studies within the area of food active packaging are experiencing great development due to the consumers’ demand and market trends. Food active packaging systems are based on materials in which some additives with antimicrobial and/or antioxidant properties are added into the polymer matrix with the aim of extending foodstuff shelf life and improving consumer’s safety [1,2,3,4]. The demand for the use of natural additives has produced in recent years a clear increase in the number of studies based on natural extracts such as essential oils, which are categorized as ‘Generally Recognized as Safe’ (GRAS) by the US Food and Drug Administration [5], and they could be considered potential alternatives to synthetic additives, such as butylated hydroxytoluene (BHT) [6]. The great interest towards the use of renewable natural resources in the food packaging industry makes natural antioxidants candidates for stabilization of biodegradable polymer formulations
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