Anais da IX Conferência Internacional de Proteínas e Coloides Alimentares

Currently there is a demand by consumers for healthier and more natural foods, without chemical additives. This makes the industry look for alternatives to traditional antimicrobials such as the use of antimicrobial biopolymers as biopreservers. Milk proteins, especially lactoferrin (L), presents antimicrobial activity due to the sequestration of iron from biological fluids and the disruption of the membranes of microorganisms. Conversely, the mechanism of antimicrobial action of chitosan (Q), a polysaccharide, is the interaction between the positive amino groups of chitosan with the negative carboxyl groups of the bacterial membrane, leading to changes in the cellular permeability of the microorganism, with consecutive loss of cellular compounds. The production of lactoferrin and chitosan nanoparticles stands out as a tool to intensify the antimicrobial potential of these biopolymers. The objective of this work was the development of natural antimicrobials from the formation of lactoferrin and chitosan nanoparticles through different techniques: electrostatic complexation and ionic crosslinking, aiming at potentiating the antimicrobial characteristic of these biopolymers. Mixed nanoparticles (with two cationic biopolymers) were produced by electrostatic complexation with gellan gum (G) or by ionic crosslinking (with sodium tripolyphosphate - TPP). The nanoparticles were characterized regarding size, charge density, morphology, and antimicrobial activity against S. aureus. The nanoparticles with more intense antimicrobial activity were selected for application in strawberry coating, aiming the increase in the shelf life of the fruits. Among the nanoparticles formed by lactoferrin-chitosan-gellan at 4.5L:4.5Q:1G, the one with the highest zeta potential (+57.90 ± 1.50 mV) and the smallest hydrodynamic diameter (53.53 ± 2.06 nm) resulted in the highest antimicrobial action (minimum inhibitory concentration of 0.0117 mg/ml). Regarding the lactoferrin-chitosan-TPP nanoparticles, the proportions 3.5L:5.5Q:1TPP and 4.5L:4.5Q:1TPP showed the best physicochemical properties of charge and size (+39.30 mV, 81.87 nm and +33.07 mV, 97.67 nm, respectively) and antimicrobial properties (0.0370 mg/ml and 0.0463 mg/ml, respectively). When applied to coating of fresh strawberries, the nanoparticles were effective in preserving their physicochemical properties, especially in the presence of carboxymethylcellulose that improved the adhesion of particles to the fruits. The antimicrobial action of nanoparticles 4.5L:4.5Q:1G, 3.5L:5.5Q:1TPP and 4.5L:4.5Q:1TPP was higher than that of lactoferrin and pure chitosan alone, however the ternary nanoparticles formed by electrostatic complexation (4.5L:4.5Q:1G) were the ones that stood out due to their bacteriostatic effect. Nanoparticles with gellan gum had the lowest MIC compared to all other nanoparticles because they had a higher zeta potential and smaller hydrodynamic size, proving the positive relationship between the increase in surface area/volume and the increase in bioactivity of the nanoparticle. Thus, these results highlight that the antimicrobial properties of these biopolymers can be improved by nanoscale aggregation. The nanoparticles produced have excellent potential for application as natural food preservatives.