pH modulates antibacterial activity of hydroxybenzaldehyde derivatives immobilized in chitosan films via reversible Schiff bases and its application to preserve freshly-squeezed juice

•Chitosan films were functionalized with Schiff bases of antimicrobial aldehydes.•Synthesis and stability of Schiff bases depended on aldehyde chemical structure.•Reversibility of Schiff bases and release of aldehydes were promoted at pH 5.•Films functionalized with salicylaldehyde were bactericidal for E. coli at pH 5.•Organic acids of carrot-orange juice pH triggered the release of salicylaldehyde.