Effect of citric acid and plasma activated water on the functional properties of sodium alginate for potential food packaging applications

Abstract In this study, cold plasma activated water (PAW) was used in the preparation of sodium alginate (SA) solution and the effect of reactive oxygen and nitrogen species (RONS), low pH and high oxidation-reduction potential on the functional properties of SA films was evaluated. Citric acid (CA) was added to SA, and the combined effect of PAW and CA on the functional properties of SA films was assessed. With 0.5, 1 and 2 w/v% addition of CA, tensile strength (TS) of the SA films decreased by 32, 58 and 66 %, while the elongation at break (EB) increased by 150, 275 and 475 %. The, TS and EB of SA films increased by 43 and 66 % when PAW was used to prepare SA solutions. Addition of glycerol reduced the TS and tensile modulus, while the EB was increased. The linear viscoelastic region (LVE) of SA decreased with the addition of CA and glycerol. However, addition of PAW increased the LVE region. The 1 and 2 % CA and PAW containing samples showed higher storage modulus as compared to the control samples and no intersection was observed between storage and loss modulus. The CA and/or PAW containing solutions showed shear thinning properties. The water vapour transmission rate (WVTR) of SA decreased by 34 % with the addition of 1 % CA, while only 12 % reduction was observed for 0.5 and 2 % CA containing samples. A further reduction in WVTR to 44 % was observed as PAW was added to 1 % CA containing SA samples.