Ana Luiza Machado Terra’s research while affiliated with University of Rio Grande and Rio Grande Community College and other places

The main motivation of the food industry is to guarantee the sensory and microbiological quality of the products. The development of active packaging through nanotechnology is a promising strategy for extending the shelf life of food products. Bacteriocins are peptides that have antibacterial properties. However, the direct application of bacteriocins in foods with a high protein and lipid content can limit or inactivate their action. Thus, nanotechnology emerges as an alternative to overcome this obstacle. This review addresses nanotechnological innovations to improve antimicrobial properties and the application of bacteriocins through active food packaging systems. In this sense, nanotechnological techniques are described as alternatives for the physicochemical stabilization of bacteriocins and to enhance their antimicrobial properties. The incorporation of nanoencapsulated bacteriocins in active packaging systems needs to be explored to expand the potential in the food industries.

The indiscriminate and continuous use of chemical substances to control pathogens negatively impacts the environment and human health. In this sense, silver nanoparticles are promising materials to be used as sensors for pathogen detection or applied as a biocide to inhibit microbial growth in plant crops. The main characteristics of silver nanoparticles for pathogen detection are high surface area, sensitivity, specificity, and precision. Therefore, these properties provide the versatility of the detection of nanobiosensor-based methods such as colorimetric, chemosensor, fluorescent, electrochemical, and optical. The synthesis of nanoparticles from biological sources is a green alternative to traditional chemical means of synthesis. Among the various green sources explored for the production of nanoparticles, microalgae have gained prominence in recent years. Microalgae are photosynthetic microorganisms that synthesize silver nanoparticles in their culture by reducing silver through enzymes, biochemical compounds with reducing or antioxidant properties. Thus, this chapter presents the green and simultaneous production of silver nanoparticles and biomass from microalgae technology. Besides, it explored the antimicrobial properties of microalgal biomass and silver nanoparticles produced by microalgae and their ability to act as a biocide. The chapter also addresses the use of silver nanoparticles for pathogen sensors and the challenges regarding the nanoparticles synthesized by microalgae as an ecological and sustainable processes.

The objective of the study was to develop pH indicator membranes from polymeric nanofibers with phycocyanin and to evaluate the irreversibility of the system. The polymeric solutions were prepared with 13% (w/v) polycaprolactone (PCL) and 6% (w/v) poly (ethylene oxide) (PEO), with varying phycocyanin concentrations of 0.5, 1 and 2% (w/v) phycocyanin with chloroform and distilled water (8:2) as the solvent. The electrospinning technique was used to form polymeric nanofibers. PCL/PEO nanofibers developed with 2% (w/v) of phycocyanin presented a smaller average diameter (875 nm) when compared to the membranes produced with 0.5 and 1% (w/v) of the pigment. Through the thermal analysis, events associated with the elimination of volatiles, free water, and bound water were observed. The phycocyanin encapsulation efficiency in PCL/PEO nanofibers with 0.5, 1, and 2% (w/v) phycocyanin was 97.7, 97.8, and 91.7%, respectively. The nanofibers with the addition of 1 and 2% (w/v) of microalgal pigment showed slightly hydrophobic characteristics (contact angle>90.0°). The nanofibers of 13% PCL and 6% PEO with 2% (w/v) phycocyanin when tested in pH buffers ranging from 3 to 4 and 5–6 showed color variation values ≥ 8.5. Thus, PCL/PEO nanofibers containing 2% (w/v) phycocyanin become a promising alternative as indicators in packaging to monitor the viability of food.

Colorimetric indicators produced from nanofibers have a high contact surface area, allowing better interaction of the indicator with the external environment. In this context, this study aimed to develop time-pH indicator nanofibers with natural pigments for use as an emerging technology in the control of food quality. The polymeric solutions were prepared with 13% (w v⁻¹) polycaprolactone (PCL) and 6% (w v⁻¹) poly (ethylene oxide) (PEO). The natural dyes added to the polymeric solution were curcumin and quercetin (2%, w v⁻¹) with the addition of 0.5 or 1% (w v⁻¹) of phycocyanin. Solutions with curcumin, quercetin, and phycocyanin only (2% w v⁻¹) were also studied. The color change monitoring was performed for 24 h, followed up every 1 h, using buffer solutions (pH 2 to 7). The condition with 2% (w v⁻¹) phycocyanin showed a color variation (ΔE ≥ 5) noticeable to the human eye in the pH range 3 to 6 in 5 h of analysis. Thus, the indicator developed with PCL/PEO nanofibers containing 2% (w v⁻¹) of phycocyanin is a promising alternative in monitoring the quality of perishable foods, as it can visually estimate changes in pH over time.