LAUSR

The present study introduces guar gum (GG), tragacanth gum (TG) and Persian gum (PG) as novel potential coating materials for fruits and vegetables. Coating solutions of these gums were prepared at different concentrations and their surface properties for coating cucumber and tomato were investigated. Results showed that tomato and cucumber epicarps were both low-energy surfaces with surface tensions of 35.86 and 34.33 mN/m, respectively. The polar and dispersive components of tomato surface were determined to be 6.86 and 27.47 mN/m, respectively. For cucumber, these parameters were estimated to be 2.45 and 33.42 mN/m, respectively. The critical surface tension values for tomato and cucumber were calculated to be 20.73 and 26.27 mN/m, respectively. The surface tension values of gum solutions were found to be in the order of GG > TG > PG. The adhesion (Wa) and cohesion (Wc) coefficients of the gum solutions varied in the ranges of 70.99–77.06 and 86.66–141.81 mN/m, respectively. At all gum concentrations, the spreading coefficient (Ws) changed in the order of GG < TG < PG. Ws was increased by increasing the gum concentration due to the reduction of Wc. The influence of GG, TG and PG concentrations on Ws was well described by a polynomial model (R2 > 0.91). The apparent viscosities of the gum solutions altered in the order of TG (46.35–2584.72 mPa s) > GG (30.05–884.2 mPa s) > PG (8.18–49.45 mPa s) over the studied concentration range (0.01–1%).