Miguel A. Cerqueira

Nanoemulsions of β-carotene using a high-energy emulsification–evaporation technique

Nanoemulsions of b-carotene were prepared using a high-energy emulsification-evaporation technique based on a 2 3 level factorial design. Results show that it is possible to obtain dispersions at a nanoscale range. Process parameters such as time and shear rate of homogenization affected significantly particle size distribution in terms of volume-weighted mean diameter and surface-weighted mean diameter. The obtained nanoemulsions presented a volume-surface diameter ranging from 9 to 280 nm immedi- ately after the production of particles, displaying in all cases a monomodal size distribution. Those nano- emulsions showed a good physical stability during 21 days storage. The stability was evaluated by the maintenance of size distribution. However, b-carotene retention inside the micelles and color were affected by storage. Processing conditions also influenced storage stability.

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

Shelf life extension of Ricotta cheese was evaluated at 4 degrees 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 x 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: O(2) permeability decreased from 1.84 to 1.35 x 10(-12) cm(3) x (Pa x s x m)(-1); CO(2) permeability increased from 1.96 to 6.31 x 10(-12) cm(3).(Pa x s x 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.

Functional polysaccharides as edible coatings for cheese.

The objective of the present study was to apply the polysaccharides from different nontraditional sources for cheese coatings. Chitosan, galactomannan from Gleditsia triacanthos, and agar from Glacilaria birdiae were tested, with different formulations and with the addition of plasticizer and corn oil. The surface properties of the cheese and the wetting capacity of the coatings on the cheese were determined. The three best solutions for each polysaccharide were chosen, further films were cast, and permeability to water vapor, oxygen, and carbon dioxide was determined, along with opacity. The solutions of G. triacanthos (formulation: 1.5% of galactomannan, 2.0% of glycerol, and 0.5% of oil) presented the best properties to coat the cheese: -38.76 mN x m(-1) for wettability; 3.24 x 10(-11) (g x (m x s x Pa)(-1)) for water vapor permeability; 0.94 x 10(-15) and 15.35 x 10(-15) (g x m(Pa x s x m(2))(-1)) for oxygen and carbon dioxide permeabilities, respectively; and opacity values of 5.27%. The O(2) consumption and CO(2) production rates of the cheese with and without coating were evaluated, showing a decrease of the respiration rates when the coating was applied. The uncoated cheese had an extensive mold growth at the surface when compared with the coated cheese. The results show that these coatings can be applied as an alternative to synthetic coatings.

Antimicrobial nanostructured starch based films for packaging

Montmorillonite modified with a quaternary ammonium salt C30B/starch nanocomposite (C30B/ST-NC), silver nanoparticles/starch nanocomposite (Ag-NPs/ST-NC) and both silver nanoparticles/C30B/starch nanocomposites (Ag-NPs/C30B/ST-NC) films were produced. The nanoclay (C30B) was dispersed in a starch solution using an ultrasonic probe. Different concentrations of Ag-NPs (0.3, 0.5, 0.8 and 1.0mM) were synthesized directly in starch and in clay/starch solutions via chemical reduction method. Dispersion of C30B silicate layers and Ag-NPs in ST films characterized by X-ray and scanning electron microscopy showed that the presence of Ag-NPs enhanced clay dispersion. Color and opacity measurements, barrier properties (water vapor and oxygen permeabilities), dynamic mechanical analysis and contact angle were evaluated and related with the incorporation of C30B and Ag-NPs. Films presented antimicrobial activity against Staphylococcus aureus, Escherichia coli and Candida albicans without significant differences between Ag-NPs concentrations. The migration of components from the nanostructured starch films, assessed by food contact tests, was minor and under the legal limits. These results indicated that the starch films incorporated with C30B and Ag-NPs have potential to be used as packaging nanostructured material.

Effect of chitosan-based coatings on the shelf life of Salmon (Salmo salar)

This study aimed at determining the effect of chitosan coating on shelf life extension of salmon ( Salmo salar ) fillets. The success of edible coatings depends highly on their effective wetting capacity of the surfaces on which they are applied. In this context in a first stage the surface properties of salmon fillets and the wetting capacity of the coatings on fish were evaluated. In terms of wettability there were no significant differences (p > 0.05) between the solutions presenting higher values (solutions 1-4); therefore, solution 1 with a spreading coefficient (Ws) of -4.73 mN m(-1), was chosen to be subsequently analyzed and applied on fish fillets. For shelf life analyses the fillets were coated and stored at 0 °C for 18 days. The control and coated fish samples were analyzed periodically for total aerobic plate count (TPC), pH, total volatile base nitrogen (TVB-N), trimethylamine (TMA), thiobarbituric acid (TBA), and ATP breakdown products (K value). The results showed that fish samples coated with chitosan presented a significant reduction (p < 0.05) for pH and K value after 6 days and for TVB, TMA, and TBA values after 9 days of storage, when compared to control samples. In terms of microbial growth, a slower increase in TPC was observed for the coated fish, indicating that chitosan-based coatings were effective in extending for an additional 3 days the shelf life of the salmon. These results demonstrate that chitosan-based coatings may be an alternative for extending the shelf life of salmon fillets during storage at 0 °C.

Chitosan/fucoidan multilayer nanocapsules as a vehicle for controlled release of bioactive compounds.

Hollow multilayer nanocapsules were successfully prepared through layer-by-layer assembly of two bioactive polysaccharides, chitosan and fucoidan. The stepwise adsorption of 10 chitosan/fucoidan layers and the consequent formation of a multilayer film on polystyrene nanoparticles (used as templates) were followed through ζ-potential measurement and the removal of the polystyrene core was confirmed by FTIR analysis. The chitosan/fucoidan nanocapsules morphology and size were evaluated by SEM and TEM, which showed that after the core removal, the nanocapsules maintained their spherical shape and a decrease of size occurred. A cationic bioactive compound, poly-L-lysine (PLL), was chosen to evaluate the loading and release behaviour of the nanocapsules. The chitosan/fucoidan nanocapsules showed a good capacity for the encapsulation and loading of PLL, which shows to be influenced by the initial PLL concentration and the method of encapsulation used. The results of fitting the linear superimposition model to the experimental data of PLL release suggest an anomalous behaviour, with one main polymer relaxation. The PLL release was found to be pH-dependent: at pH 2 relaxation is the governing phenomenon and at pH 7 Ficks diffusion is the main mechanism of PLL release. Chitosan/fucoidan nanocapsules is a promising delivery system for water soluble bioactive compounds, such as PLL, showing a great potential of application in food and pharmaceutical industries.

Biorefinery valorization of autohydrolysis wheat straw hemicellulose to be applied in a polymer-blend film

The aims of this study were the extraction of hemicellulose from wheat straw (WS) and its utilization in the reinforcement of a κ-carrageenan/locust bean gum (κ-car/LBG) polymeric blend films (PBFs). WS hemicellulose extraction was performed under autohydrolysis process and hemicellulose extracted (HE) under optimum condition was used in PBFs. PBFs were prepared varying different proportions of HE into the κ-car/LBG film-forming solutions. Barrier properties (water vapor permeability, WVP), mechanical properties (tensile-strength, TS and elongation-at-break, EB), moisture content, opacity and thermal properties of the resulting PBFs were determined and related with the incorporation of HE. The 2-3-2 proportion (in the high ratio) of PBF (κ-car/LBG/HE) causes a slight decrease of WVP and an increase of the TS, thus resulting in an improvement of the physical properties of PBFs. HE showed to be a promising material in order to reinforce κ-car/LBG PBF and can be an alternative in the application of hemicellulose according to biorefinery concept.

Effects of Electric Fields on Protein Unfolding and Aggregation: Influence on Edible Films Formation

Electric fields application is receiving increased attention because of its uniform heating of liquids. The mechanisms of unfolding and aggregation of whey proteins during ohmic heating may influence properties of edible films made thereof. The aim of this work was to evaluate the effects of ohmic heating on physical and structural properties of whey protein edible films and compare them with those obtained by conventional heating. The results showed that ohmic heating determined less aggregation and lower concentration of free sulphydryls in film-forming solutions. Ohmic films were thinner, less permeable to water vapor and presented nearly the same mechanical properties of conventional films. Ohmic heating induced protein conformational changes by increasing the contents of β-sheet structures in the film network. This work emphasized the effects of ohmic heating in unfolding and aggregation mechanisms of whey proteins during heat denaturation, which determined the production of protein edible films with distinctive properties.

Alginate/chitosan nanoparticles for encapsulation and controlled release of vitamin B2

This work aims at evaluating encapsulation and controlled release of vitamin B2 from alginate/chitosan nanoparticles. Ionotropic polyelectrolyte pre-gelation was used as production method being chitosan and alginate used as main materials. Nanoparticles were characterized in terms of average size, polydispersity index (PDI), zeta potential and vitamin entrapment efficiency. The average size for alginate/chitosan nanoparticles was 119.5±49.9nm for samples without vitamin B2 and 104.0±67.2nm with the encapsulation of vitamin B2, presenting a PDI of 0.454±0.066 and 0.319±0.068, respectively. The nanoparticles showed encapsulation efficiency and loading capacity values of 55.9±5.6% and 2.2±0.6%, respectively. Release profiles were evaluated at different conditions showing that the polymeric relaxation was the most influent phenomenon in vitamin B2 release. In order to study their stability nanoparticles were stored at 4°C being particles sizes and PDI evaluated during 5 months showing the results that vitamin B2-loaded nanoparticles are more stable (in terms of size and PDI) than nanoparticles without vitamin B2.

Design of Bio-nanosystems for Oral Delivery of Functional Compounds

Nanotechnology has been referred to as one of the most interesting topics in food technology due to the potentialities of its use by food industry. This calls for studying the behavior of nanosystems as carriers of biological and functional compounds aiming at their utilization for delivery, controlled release and protection of such compounds during food processing and oral ingestion. This review highlights the principles of design and production of bio-nanosystems for oral delivery and their behavior within the human gastrointestinal (GI) tract, while providing an insight into the application of reverse engineering approach to the design of those bio-nanosystems. Nanocapsules, nanohydrogels, lipid-based and multilayer nanosystems are discussed (in terms of their main ingredients, production techniques, predominant forces and properties) and some examples of possible food applications are given. Phenomena occurring in in vitro digestion models are presented, mainly using examples related to the utilization of lipid-based nanosystems and their physicochemical behavior throughout the GI tract. Furthermore, it is shown how a reverse engineering approach, through two main steps, can be used to design bio-nanosystems for food applications, and finally a last section is presented to discuss future trends and consumer perception on food nanotechnology.