Abstract
In this research, the antibacterial and antioxidant properties of oregano essential oil (OEO), rosemary extract (RE), and green tea extract (GTE) were evaluated. These active substances were encapsulated into ultrathin fibers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) derived from fruit waste using solution electrospinning, and the resultant electrospun mats were annealed to produce continuous films. The incorporation of the active substances resulted in PHBV films with a relatively high contact transparency, but it also induced a slightly yellow appearance and increased the films opacity. Whereas OEO significantly reduced the onset of thermal degradation of PHBV, both the RE and GTE-containing PHBV films showed a thermal stability profile that was similar to the neat PHBV film. In any case, all the active PHBV films were stable up to approximately 200 °C. The incorporation of the active substances also resulted in a significant decrease in hydrophobicity. The antimicrobial and antioxidant activity of the films were finally evaluated in both open and closed systems for up to 15 days in order to anticipate the real packaging conditions. The results showed that the electrospun OEO-containing PHBV films presented the highest antimicrobial activity against two strains of food-borne bacteria, as well as the most significant antioxidant performance, ascribed to the films high content in carvacrol and thymol. Therefore, the PHBV films developed in this study presented high antimicrobial and antioxidant properties, and they can be applied as active layers to prolong the shelf life of the foods in biopackaging applications.
Highlights
The packaging industry requires the development of new plastic materials with active properties, based on the demand by consumers for safer and more nutritive food [1]
The neat PHBV solution, without oregano essential oil (OEO) and natural extracts (NEs), showed the highest viscosity value, that is, 212.4 cP. This value was relatively similar to that reported by Melendez-Rodriguez et al [39], who obtained a value of viscosity of 296.8 cP for a PHBV solution in 2,2,2-trifluoroethanol (TFE) at 2 wt%
When OEO, Rosemary extract (RE), and green tea extract (GTE) were added, the viscosity of the PHBV solution slightly decreased. This effect could be ascribed to a reduction of the molecular cohesion forces in the biopolymer due to the presence of the active substances. This result was in agreement with, for instance, previous research works reported by Arfa et al [46] and Jouki et al [47], showing that the addition of either OEO or its active components decreased the apparent viscosity of polymer solutions of mucilage and soy protein (SP)
Summary
The packaging industry requires the development of new plastic materials with active properties, based on the demand by consumers for safer and more nutritive food [1]. Active packaging technology is mostly related to materials and articles that are intended to extend food shelf life, and to improve packaged food conditions by interacting with the food product and/or with its internal packaging environment. Active packaging systems can extend the shelf life of food products and reduce food waste by maintaining the quality of food products for longer, increasing product safety by securing the foods against pathogens, and enhancing the convenience of food processing, distribution, retailing, and consumption [11]. Active-releasing antimicrobial packaging applications are directly related to food microbial safety, as well as to shelf life extension, by preventing the growth of spoilage and/or pathogenic microorganisms [15,16]. The growth of spoilage microorganisms can reduce the food shelf life, but it can endanger public health ( in the case of pathogenic microorganisms)
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