Shelf life extension of Ricotta cheese using coatings of galactomannans from nonconventional sources incorporating nisin against Listeria monocytogenes

Abstract

Shelf life extension of Ricotta cheese was evaluated at 4 °C upon the use of edible coatings made of galactomannans from Gleditsia triacanthos incorporating nisin against Listeria monocytogenes. Three different treatments were tested in cheese: samples without coating; samples with coating without nisin; and samples with coating containing 50 IU·g−1 of nisin. To test the effectiveness of the treatments against L. monocytogenes, the surface of the cheese was inoculated with a suspension of the microorganism. Microbiological and physical−chemical analyses of the cheese samples were performed during 28 days. Results showed that the cheese coated with nisin-added galactomannan film was the treatment presenting the best results in terms of microbial growth delay (p < 0.05). The addition of nisin also affects (p < 0.05) the physical and mechanical properties of the films: O2 permeability decreased from 1.84 to 1.35 × 10−12 cm3·(Pa·s·m)−1; CO2 permeability increased from 1.96 to 6.31 × 10−12 cm3·(Pa·s·m)−1; opacity increased from 3.68 to 4.59%; tensile strength ranged from 0.84 to 1.46 MPa; and elongation at break improved from 50.93 to 68.16%. These results demonstrate that novel galactomannan-based edible coatings, when combined with nisin, may provide consumer-friendly alternatives to reduce L. monocytogenes postcontamination on cheese products during storage.