Nanoemulsão de goma do cajueiro (Anacardium occidentale) e óleo essencial de manjericão-cravo (Ocimum gratissimum) na inibição de melanose e qualidade de camarão branco do pacifico (Litopenaeus vannamei)

Abstract

Shrimp is a food with high nutritional value, consumed in different parts of the world. However, it degrades rapidly with the emergence of melanosis, which leads to rejection of the product and great losses for meat production. Nanotechnology has shown promise for the development of carriers of natural compounds in foods. Therefore, we sought to develop a nanostructured system using natural compounds to inhibit the emergence of melanosis and preserve the quality of refrigerated shrimp. In this study, essential oil (EO) nanoemulsions from Ocimum gratissimum and cashew gum (Anacardium occidentale) (CG) were produced using low and high energy techniques. The main constituents of EO were determined by chromatography and mass spectrometry. The hydrodynamic diameter, polydispersion index, zeta potential and encapsulation efficiency (EE%) were used to evaluate the stability of the nanoemulsion during storage. Nanoparticle tracking analysis (NTA) and Atomic Force Microscopy (AFM) were used to determine the size distribution of micelles and their morphological analysis, respectively. Computational methods of molecular dynamics determined the interaction between the constituents of the system in the formation of the nanoemulsion. The Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC) were determined for the pathogenic species Staphylococcus aureus, Escherichia coli and Salmonella enterica. AFM showed the interaction between the nanoemulsion and the cell surface of S. enterica. Antioxidant activity was evaluated against ABTS and DPPH radicals. EO and nanoemulsion with CG were used to maintain freshness and quality in Litopenaeus vannamei stored for 16 days at 4 ± 0.5 ºC. The parameters evaluated consisted of the appearance of melanosis, growth of psychrotrophic bacteria, pH, Total Volatile Base Nitrogen (T-BVN) and Thiobarbituric Acid Reactive Substances (TBARS). The EO presented eugenol and eucalyptol as major constituents. The nanoemulsions had an average diameter of 108 - 180 nm and EE% of 88.81 - 94.19%. Nanoemulsions showed better MIC and MBC results compared to EO for S. aureus and E. coli, however, for S. enterica only the bactericidal action was enhanced. The antioxidant action of nanoemulsions also showed better results compared to EO. It was observed that it is possible to use a self-emulsification method, capable of keeping the EO content stable in the system, improving and preserving its antibacterial and antioxidant activity. Shrimp treated with nanoemulsion showed greater inhibition of melanosis than those treated with EO and without treatment (control). The pH showed a gradual increase and no difference (p >0.05) between treatments. The analysis of psychrotrophic bacteria, T-BVN and TBARS, showed better results for EO and nanoemulsion, not differing from each other (p >0.05). This demonstrates that both can act to prevent lipid oxidation, improving physicochemical parameters and providing longer shelf life in relation to untreated shrimp. Therefore, the nanoemulsion is promising due to its better performance against pathogenic bacteria linked to fish consumption, contributing to the safety of this food.