Properties of whey protein-based films containing organic acids and nisin to control Listeria monocytogenes.
Whey protein isolate and glycerol were mixed to form a matrix to incorporate antimicrobial agents and produce edible films with antimicrobial activity against Listeria monocytogenes strains isolated from cheeses. Various organic acids were used to decrease pH down to approximately 3. In a preliminary assay without nisin, the effect of each organic acid was evaluated with respect to the rheological properties of the film solutions and the inhibitory and mechanical properties of the films. Lactic, malic, and citric acids (3%, wt/vol), which were used in a subsequent study of their combined inhibitory effect with nisin (50 IU/ml), had significantly higher antilisterial activity (P < 0.05) compared with the control (2 N HCl, 3% [wt/vol], with nisin). The largest mean zone of inhibition was 4.00 +/- 0.92 mm for malic acid with nisin. Under small-amplitude oscillatory stress, the protein-glycerol-acid film solutions exhibited a predominantly viscous behavior or a weak gel behavior, with the storage modulus (G') slightly higher than the loss modulus (G"). The malic acid-based solution was the only one whose viscosity was not influenced by the addition of nisin. The addition of nisin resulted in a nonsignificant (P > 0.05) increase in the percentage of elongation at break. Results from tensile and puncture stress were variable, but in general no significant differences were found after the incorporation of nisin. The overall results support the use of malic acid with nisin to produce effective antimicrobial films to control L. monocytogenes growth.
Escola Superior Agrária, Instituto Politécnico de Castelo Branco, Quinta da Senhora de Mércoles, 6001-909 Castelo Branco, Portugal. cpintado@esa.ipcb.pt
Cristina M B S
CM
Pintado
Maria A S S
MA
Ferreira
Isabel
I
Sousa
D019343:Citric Acid / Q000494:pharmacology; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D005519:Food Preservation / Q000379:methods*; D005520:Food Preservatives / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000494:pharmacology; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000254:growth & development; D008293:Malates / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008894:Milk Proteins; D009561:Nisin / Q000494:pharmacology*; D012212:Rheology; D013718:Tensile Strength; D000067816:Whey Proteins
D004338:Drug Combinations; D005520:Food Preservatives; D008293:Malates; D008894:Milk Proteins; D000067816:Whey Proteins; D009561:Nisin; D019343:Citric Acid; D019344:Lactic Acid; C030298:malic acid