Reduction of Dickeya chrysanthemi on fresh-cut iceberg lettuce using antimicrobial sachet containing microencapsulated oregano essential oil

An antimicrobial sachet releasing vapor of oregano essential oil (EO) was developed and its effectiveness as an antimicrobial packaging system for fresh-cut iceberg lettuce was evaluated. Oregano EO was microencapsulated with polyvinyl alcohol (oregano EO/PVA ratio: 3/5 (w/w)) using a spray-drying technique. The sachet containing oregano microcapsules was incubated with iceberg lettuce at 20 °C and 85% RH for five days. During this storage, the reduction efficiency against growth of Dickeya chrysanthemi, molds and yeasts (MY), and total mesophilic aerobic bacteria (MAB) on the surface of iceberg lettuce was investigated. Oregano EO released from the sachet inhibited the growth of D. chrysanthemi, resulting in 3.9 log CFU/5 pieces reduction over five days storage at 20 °C. The volatile oregano EO also showed significant growth inhibitory effects against MY and total MAB that each was significantly reduced by 2.1 log CFU/5 pieces and 1.5 log CFU/5 pieces, respectively. The texture and color characteristics of the iceberg lettuce were not affected by the release of oregano EO vapor. These results may be useful for the development of antimicrobial packaging systems that are intended to increase the microbiological safety and to extend the shelf life of fresh products.