In a nutshell: prospects and challenges on coatings for edible kernels.

Edible kernels have been popular food items since ancient times. Although in-shell nuts are naturally protected and relatively shelf stable, convenience demands require their commercialization in shelled form. However, whereas shelled kernels are more convenient, they are more exposed to oxygen, and thus more susceptible to oxidative rancidity and loss of crunchiness, which negatively affect the product acceptability. In this review, we discuss the role of edible coatings in extending stability of edible kernels, which is an opportunity to be better explored by the industry. The discussion also includes the role of antioxidants in the context of active coatings. Finally, future prospects and research challenges are addressed. © 2019 Society of Chemical Industry.

Nanoencapsulation of active compounds in chitosan by ionic gelation: Physicochemical, active properties and application in packaging.

The ionic gelation technique using chitosan to encapsulate active compounds has received lots of attention in the literature due to its ease-of-use and known biodegradability, biocompatibility and antimicrobial properties of the polymer. In this review, main studies from the last five years involving encapsulation of active compounds (natural and commercial/synthetic) are brought together in order to understand the encapsulation mechanisms of components with chitosan as well as the physical, chemical and morphological properties of the resulting particles. The application of these nanostructures in polymeric films was then investigated, since additives for packaging are an attractive premise and have only recently started being studied in the literature. Herein, comparisons are made between free and encapsulated bioactive compounds in different film matrices, as well as the effect of this activation on structure. Finally, this work details the mechanisms involved in the production of chitosan nanoparticles with active compounds and encourages new studies to focus on their application in packaging.

Ultrasound-assisted extraction of bioactives as a strategic step for chemical pretreatments in nanocellulose production from acerola by-products.

Acerola by-products (AB) have been used as raw material for extracting active compounds; however, there were no studies related to the use of the remaining acerola by-product (RAB) from this extraction. This portion still has fibers and can be used for the production of cellulose nanofibrils (CNFs); therefore, the main objective of this study was to evaluate the production of CNFs using AB and RAB and to investigate whether the extraction can be a treatment step before bleaching/acid hydrolysis. AB and RAB were characterized before and after being chemically treated (AB_CT and RAB_CT, respectively). The fibers extracted from the RAB showed the highest cellulose contents (RAB: 36.6 % and RAB_CT: 69.9 %), suggesting that the extraction process had an impact on by-product defibrillation. The same trends were observed for CNFs produced by acid hydrolysis. CNFs based on RAB showed higher yield (CNF_RAB: 25.2 % and CNF_RAB_CT: 24.2 %), higher crystallinity index (CNF_RAB: 68.3 % and CNF_RAB_CT: 71.7 %) and higher thermal stability compared to CNFs extracted from AB and AB_CT. This study proved that it is feasible to use by-products after removing the active compounds for CNF production without other pre-treatments or in association with chemical treatment to obtain more crystalline and thermally stable CNFs.

Measuring bacterial cells size with AFM.

Atomic Force Microscopy (AFM) can be used to obtain high-resolution topographical images of bacteria revealing surface details and cell integrity. During scanning however, the interactions between the AFM probe and the membrane results in distortion of the images. Such distortions or artifacts are the result of geometrical effects related to bacterial cell height, specimen curvature and the AFM probe geometry. The most common artifact in imaging is surface broadening, what can lead to errors in bacterial sizing. Several methods of correction have been proposed to compensate for these artifacts and in this study we describe a simple geometric model for the interaction between the tip (a pyramidal shaped AFM probe) and the bacterium (Escherichia coli JM-109 strain) to minimize the enlarging effect. Approaches to bacteria immobilization and examples of AFM images analysis are also described.

Chitosan suspension as extractor and encapsulating agent of phenolics from acerola by-product.

The polymeric suspension of chitosan (Ch) has been an effective media for the extraction of total phenolic compounds (TPC) from the acerola by-product. It facilitates the subsequent production of nanoparticles loaded with the phenolics (Np-TPC) by ionic gelation. However, neither the effects of Ch concentration on encapsulation efficiency (EE%) of TPC nor which compounds are extracted in its media are known, being it the first objective of this study. The second objective was to analyze the stability of the Np-TPC under accelerated conditions and its release profile at pHs 3.0 and 7.0. The results showed that Ch does not affect the extraction of TPC. However, the EE increased from 35.0 to 48.1 % with the increase of Ch concentration (0.4 to 1.0 %). LC/ESI-QTOF MS analysis showed that phenolic acids and flavonoids are extracted in 0.8 % Ch medium. After encapsulation, microscopy images revealed particle sizes ranging between 110 and 150 nm. Additionally, the presence of phenolics did not change the stability of the particles under accelerated conditions and the actives were fully released into the released medium for 10 h. The Np-TPC suspension appears to be useful for the production of edible antioxidant coatings to preserve fruits/vegetables, with potential application as carrier of other food ingredients.

Extraction of phenolic compounds from acerola by-products using chitosan solution, encapsulation and application in extending the shelf-life of guava.

Aiming the simplification of the production of chitosan nanoparticles as an encapsulating material, the primary approach of this study was to investigate the extraction of active compounds from acerola-pulp by-products directly in chitosan solution by using tip sonication. The results have shown that chitosan solution can be used as a good solvent, mainly for total phenolic compounds (TPC) extraction (1792.7 mg/100 g of dry by-product). The extract was submitted to ionic gelation process using, as counter-ion, the sodium tripolyphosphate to form loaded nanoparticles with TPC. The suspension was applied as protective coatings on the guavas. The nanoengineered coatings provided an effective barrier that delayed the maturation and maintained the green pigmentation for longer periods along with good firmness. To the best of our knowledge, this was the first study that uses chitosan solution as extraction solvent of TPC from food byproducts in order to facilitate the encapsulation process.

Whey Protein Isolate Microgel Properties Tuned by Crosslinking with Organic Acids to Achieve Stabilization of Pickering Emulsions.

Whey protein isolate (WPI) can be used effectively to produce food-grade particles for stabilizing Pickering emulsions. In the present study, crosslinking of WPI microgels using organic acids (tannic and citric acids) is proposed to improve their functionality in emulsions containing roasted coffee oil. It was demonstrated that crosslinking of WPI by organic acids reduces the microgels' size from ≈1850 nm to 185 nm and increases their contact angle compared to conventional WPI microgels, achieving values as high as 60°. This led to the higher physical stability of Pickering emulsions: the higher contact angle and smaller particle size of acid-crosslinked microgels contribute to the formation of a thinner layer of particles on the oil/water (O/W) interface that is located mostly in the water phase, thus forming an effective barrier against droplet coalescence. Particularly, emulsions stabilized by tannic acid-crosslinked WPI microgels presented neither creaming nor sedimentation up to 7 days of storage. The present work demonstrates that the functionality of these crosslinked WPI microgels can be tweaked considerably, which is an asset compared to other food-grade particles that mostly need to be used as such to comply with the clean-label policy. In addition, the applications of these particles for an emulsion are much more diverse as of the starting material.

Amphiphilic diethylaminoethyl chitosan of high molecular weight as an edible film.

Edible films and coatings can enhance the quality of food products, protecting them from biological deterioration, especially against fungal diseases and pathogenic microorganisms. In this study, films from chitosan, diethylaminoethyl-chitosan (DEAE-CH) and its hydrophobicized derivative DEAE-CH-DD were prepared by casting and their physicochemical and antimicrobial properties evaluated. The grafting with DEAE and dodecyl groups resulted in films with an elasticity modulus up to five times higher than commercial chitosan and increased water vapor permeability. Field emission gun - scanning electron microscopy and atomic force microscopy techniques showed films with smooth surfaces and the contact angle measurements revealed a correlation between the grafted group and hydrophilic/hydrophobic nature of the surface of the film. The amphiphilic derivatives exhibited better antimicrobial activity than unmodified chitosan against Penecillium expansum, Alternaria alternata and Alternaria solani. The amphiphilics DEAE-CH and DEAE-CH-DD showed no toxicity and delayed rotting and loss of water in strawberries and bananas, suggesting that this kind of film has great potential for increasing the shelf-life of different fruits.

Chitosan and crosslinked chitosan nanoparticles: Synthesis, characterization and their role as Pickering emulsifiers.

Chitosan has been modified in order to produce nanoparticles with promising characteristics in diverse food applications, e.g. Pickering emulsions. Chitosan deprotonation and ionic crosslinking with tripolyphosphate were assessed in this work. Chitosan nanoparticles produced by these two methods were characterized according to surface charge, particle size distribution, chemical structure, wettability and microstructure imaging. The nanoparticles' performance in the formation of oil-in-water Pickering emulsions was studied by physicochemical and rheological assays. Chitosan nanoparticles produced by amino deprotonation were larger and resulted in emulsions with larger oil droplets, with rheological behavior of the emulsions being greatly affected by increasing concentration of chitosan, which formed a network structure in the continuous phase. On the contrary, the tripolyphosphate-crosslinked chitosan nanoparticles were smaller and produced emulsions with smaller droplets, which remained less viscous even when chitosan concentration was increased and showed evidences of Pickering stabilization when analyzed by microscopy techniques.

Preparation and Characterization of Nanocomposites from Whey Protein Concentrate Activated with Lycopene.

The production and characterization of nanocomposites based on whey protein concentrate (WPC) and montmorilonite (MMT) incorporated with lycopene as a functional substance is presented and discussed as an alternative biomaterial for potential uses in foodstuff applications. A full factorial design with varying levels of MMT (0% and 2% in w/w) and lycopene (0%, 6%, and 12% in w/w) was used. Color, light transmission, film transparency, moisture, density, solubility, water vapor permeability, and antioxidant activity of the resulting materials were evaluated. Results indicated that lycopene and MMT nanoparticles were successfully included in WPC films using the casting/evaporation method. Inclusion of 2% w/w of MMT in the polymeric matrix significantly improved barrier property against water vapor. Lycopene, besides its good red coloring ability, provided to the films antioxidant activity and UV-vis light protection. These findings open a new perspective for the use of materials for bioactive packaging applications.

Development of poly(lactic acid) nanostructured membranes for the controlled delivery of progesterone to livestock animals.

Solution blow spinning (SBS) is a novel technology feasible to produce nanostructured polymeric membranes loaded with active agents. In the present study, nanofibrous mats of poly(lactic acid) (PLA) loaded with progesterone (P4) were produced by SBS at different P4 concentrations. The spun membranes were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). The in vitro releasing of P4 was evaluated using high-performance liquid chromatography (HPLC). Interactions between progesterone and PLA were confirmed by rheological measurements of the PLA/P4 solutions and in the spun mats by microscopy (SEM), thermal (DSC) and spectral (FTIR) analyses. SEM micrographs provided evidences of a smooth and homogeneous structure for nanostructured membranes without progesterone crystals on fiber surface. FTIR spectroscopy indicated miscibility and interaction between the ester of PLA and the ketone groups of the P4 in the nanofibers. X-ray analysis indicated that the size of PLA crystallites increased with progesterone content. Finally, by in vitro release experiments it was possible to observe that the progesterone releasing follows nearly first-order kinetics, probably due to the diffusion of hormone into PLA nanofibers.

Measuring bacterial cells size with AFM

Atomic Force Microscopy (AFM) can be used to obtain high-resolution topographical images of bacteria revealing surface details and cell integrity. During scanning however, the interactions between the AFM probe and the membrane results in distortion of the images. Such distortions or artifacts are the result of geometrical effects related to bacterial cell height, specimen curvature and the AFM probe geometry. The most common artifact in imaging is surface broadening, what can lead to errors in bacterial sizing. Several methods of correction have been proposed to compensate for these artifacts and in this study we describe a simple geometric model for the interaction between the tip (a pyramidal shaped AFM probe) and the bacterium (Escherichia coli JM-109 strain) to minimize the enlarging effect. Approaches to bacteria immobilization and examples of AFM images analysis are also described.

Tratamentos de silanização em grãos de feijão por hexametildissilazana: resultados preliminares / Silanization treatments on beans by hexamethyldisilazane: preliminary results

Grãos comerciais de feijão (Phaseolus vulgaris L.) foram submetidos a tratamentos para formação de filme hidrofóbico por três procedimentos distintos de silanização. A solução precursora foi hexametildissilazana (HDMS) para todos os tratamentos. Os resultados indicam que todas as seqüências tornam a superfície dos grãos resistentes à umidade, reduzindo a absorção em valores de 15 a 57 por cento em comparação às amostras não tratadas. Ensaios de germinação em teste-padrão mostraram que os tratamentos retardam ou evitam a germinação indesejável mesmo em condições de alta umidade.

Development of an algorithm for tip-related artifacts identification in AFM biological film imaging

Um aspecto limitante a plena interpretação de imagens geradas por microscopia de força atômica é a interação entre a superfie varrida e ponta de varredura do sistema gerando artefatos de imagens. Para a identificação desses artefatos, propomos neste texto, um algoritmo simples capaz de assinalar esse tipo de irregularidade de imagem. A medida tem por princípio a identificação de ângulos similares formados entre dois pontos sobre a espécie varrida. O potencial de aplicação do método proposto é aqui ilustrado sobre um filme de polissacarídeo quitosana. As imagens geradas são comparadas entre si, indicando regiões de artefatos típicos gerados pela ponta de varredura. Este algoritmo apresenta-se como uma ferramenta útil a cientistas e usuários, permitindo a separação de aspectos reais e artificiais, que são fundamentais para uma melhor caracterização e medida.

Avaliação de técnica eletroquímica na remoção de resíduos orgânicos em água com emprego de unidade em escala de laboratório / Evaluation of electrochemical technique for removal of organic waste from water by using a laboratory scale unit

Neste trabalho são apresentados os resultados preliminares da avaliação de técnica eletroquímica na remoção de compostos orgânicos em água, em escala laboratorial. Cela eletroquímica simples foi construída para os testes e uma metodologia básica foi empregada. O método consiste em provocar a migração de espécies polares ou ionizadas em direção ao eletrodo de carga oposta. Fenol e o herbicida atrazina foram os contaminantes avaliados. Os ensaios foram realizados em função do tempo de aplicação de carga, acompanhada a evolução do pH entre os eletrodos e as concentrações relativas avaliadas por medidas de absorbância na região do ultra-violeta. Os melhores resultados foram conseguidos para operações acima de 30 minutos, indicando migração proporcional a 62% para o fenol, mas inferior a 30% para a atrazina.

In this work the preliminary results of a lab scale evaluation of electrokinetic technique for the removal of organic contaminants in water are presented. A simple cell was constructed and a basic methodology was followed. The method consists in provoke the migration of ionized or polar specimens solved in aqueous solution in direction of the opposite charged electrode. Phenol (C6H5OH) and herbicide atrazine (6-chlorine-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4 diamine), was chosen as standard contaminants. The testes were performed in function of charge application time, mapping the pH between electrodes and the concentration assessed by absorbance measurements in ultra-violet region. The best results were attained after 30 minutes operation, showing migration proportional to 62% for phenol, but inferior to 30% atrazine.

Corrosão de amálgamas / Amalgams corrosion

No presente trabalho, os autores procuraram determinar a corrosão de algumas marcas e tipos de amálgamas odontológicos, por meio de potenciostato eletrônico, que situa-se entre os aparelhos que maior uso e desenvolvimento vem recebendo. Através desse, era possível obter curvas de polarização e características eletroquímicas dos materiais, com reprodutividade satisfatória. Análises, foram feitas, de restaurações com os diferentes tratamentos superficiais, em pacientes e após isto, comparadas com os resultados obtidos por meio das curvas de polarização já citadas

Corrosão das restaurações de amálgama: comportamento "in vivo", frente à técnica de polarização anódica / Amalgama corrosion in dental restorations: in vitro behaviour using anodyc polarization technique

No presente trabalho, foram feitas, análises de alguns tipos e marcas comerciais de limalhas para restaurações à amálgama, após testes com um potenciostato eletrônico que situa-se hoje, entre os aparelhos que maior uso e desenvolvimento vem recebendo. Através desse aparelho, era possível obter curvas de polarização e características eletroquímicas dos materiais, com reprodutividade satisfatória. Foram analisadas, ainda, restaurações com diferentes tratamentos superficiais, em pacientes de 14 a 40 anos de idade, em um período de 2 anos e comparadas, com os resultados obtidos por meio das curvas de polarização anódicas, acima citadas