Physicochemical and repellent properties of chitosan films loaded with essential oils for producing an active packaging effective against the food pest Sitophilus oryzae

Sitophilus oryzae (L.) (Coleoptera: Dryophtoridae) represents one of the most important pests of stored products. The adults are considered very effective packaging penetrators, causing serious economic losses. Hence, the development of new food packaging technologies is crucial to prevent its infestations. In this study, Citrus × aurantium L., Elettaria cardamomum (L.) Maton, Ocimum basilicum L., and Piper nigrum L. essential oils (EOs) were analyzed by GC-EIMS and then used to produce aromatized chitosan (CHT)-based films. The spontaneous volatile emissions of these films were evaluated by headspace solid phase micro-extraction (HS-SPME) to assess the chemical composition of the vapors released from the CHT matrix after 2, 5, 7, 9, 12, and 14 days. The thickness, moisture content, swelling properties, total soluble matter, water vapor transmission rate, color, and transmission and transparency of light of all the CHT films after 1, 7, 14, 21, 28, and 35 days were also assessed. Furthermore, the repellency of the EO-loaded CHT films was tested daily against S. oryzae adults for 28 days.

Overall, adding the different EOs to the CHT films had a good impact on their physical and chemical properties. In particular, the C. × aurantium EO-loaded CHT film was characterized by the lowest swelling ratio, solubility, and water vapor transmission rate, besides having the lowest impact on the film transparency and opacity among the four EOs involved and a pleasant, lemon-like odor. The same C. × aurantium EO-loaded film was also the most effective as a repellent against S. oryzae, with a long-lasting effect for up to 28 days on the pest and a median repellency time (RT₅₀) of 7.184 days.