Effect of Chitosan Edible Coatings Incorporated with Free or Microencapsulated Thyme Essential Oil on Quality Characteristics of Fresh-Cut Carrot Slices

Abstract

The present study evaluated the effectiveness of the application of active edible coatings based on chitosan containing free thyme essential oil (TO) and microencapsulated TO in β-cyclodextrin (β-CD) in enhancing the quality and shelf-life of sliced carrots during 13 days of refrigerated storage. All coated samples showed less superficial discoloration and better organoleptic quality than non-coated samples. In fact, non-coated carrot slices showed overall visual quality (OVQ) scores below the limit of acceptance from day 9 of storage, while all the other samples exhibited acceptable values of OVQ during the entire sampling period. Higher values of total phenolics content (TPC) and antioxidant capacity were observed in coated samples with respect to uncoated ones. Moreover, coatings containing TO were more effective in enhancing the phytochemical quality of the samples, and those containing the essential oil microencapsulated in β-CD presented the highest values of TPC and antioxidant activity along storage. An initial reduction in the counts of mesophilic, psychrophilic, and yeast and molds populations was detected in the samples coated with free TO with respect to the other samples, effect that was not maintained during storage. On the contrary, the use of microencapsulated TO in the chitosan coatings allowed to reduce the microbial counts from day 6 till the end of storage. Results demonstrate the potential of applying chitosan coatings enriched with thyme essential oils to improve the quality of minimally processed carrots during storage. In addition, the efficacy of β-CD as a carrier of thyme essential oil bioactives is also highlighted.