Antimicrobial activity of sugar beet lignocellulose films containing tung oil and cedarwood essential oil

Abstract

Several studies have been reported on the use of cellulose, lignocellulose, chitin and other biolog- ical macromolecules for food packaging. One of the major drawbacks limiting their wide uses is their limited antimicrobial and water vapor barrier properties. In this study, cedarwood (Thuja occidentalis) essential oil (CWO), known to contain terpenes, polyphenols and tung oil, known to contain fatty acids, were used as additives to improve water vapor barrier, antimicrobial, and physical properties of laboratory cast lignocellulose films. Physicochemical and mechanical properties were tested to evaluate theimpact ofthe addition of oils in the filmsformulations.Theadditionof15 %CWOandtung oils improved water vapor permeability by more than 25 % as also evidenced by the increase of contact angle between water andfilm by 134 % from 38.98to 89.36 with 15 % tung oil. FTIR was used to monitor the presenceofhydrophobic groupsat 1463and1741 cm -1 from the oil on the film spectra confirming the improvement of film hydrophobicity from oils interac- tions. However, the addition of 15 % hydrophobic oils promoted a significant decrease in tensile properties of films (p B 0.05) by 40 % for CWO and 32 % for tung oil,respectively,duetoapartialincompatibilitybetween hydrophilic lignocellulose and hydrophobic oils. The use of a tailored coupling agent to reduce the incom- patibility and to improve the load charge transfer between hydrophobic and hydrophilic group might reduce the decrease of the tensile properties with the addition of hydrophobic compounds. No significant difference (p(0.05) was observed on the thermal stability of films using TGA. The antimicrobial effects of lignocellulose films against bacteria namely Listeria innocua, Escherichia coli ,a ndSalmonella enterica was tested by disk inhibition zone method and showed an improvement with the addition of 5 % CWO in thefilm. The Microbe Growth Index of the lignocellulose cellulosicfilmscontaining20 %w/wofCWOdecreases by 80 %. CWO and tung oil are good candidates to control microbial growth and water vapor permeability in flexible films. Future work will focus on the olfactory andtensilepropertiesforapplicationsinfoodpackaging.