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The objective of this study was to encapsulate avocado oil in ultrafine zein fibers by the electrospinning technique. Avocado oil, at concentrations of 15 and 30% (w/w), was incorporated into 20, 25 and 30% (w/v) zein polymer solutions. The polymer solutions were evaluated for viscosity and electrical conductivity. The zein fibers containing the avocado oil were evaluated for the efficiency of encapsulation, morphology and size distribution of diameter, FTIR-ATR and X-ray diffraction, as well as for the release of carotenoids in gastrointestinal conditions in vitro. At the concentration of 30% zein, continuous ultrafine fibers were obtained, without bead formation and with mean diameter distribution ranging from 618 to 971 nm, whose encapsulation efficiency was higher than 77%. The FTIR-ATR analysis showed the encapsulation of the oil, and X-ray diffraction showed the amorphous structure of the fibers. It was verified that the composite fiber of 30% of zein and 30% of oil had a release profile close to the ideal of carotenoid release under simulated gastrointestinal conditions.

The objective of this study was to immobilize α-amylase in ultrafine polyvinyl alcohol (PVA) fibers by electrolysis and to evaluate its stability at different temperatures and pHs using various starch substrates such as corn starch and germinated and ungerminated wheat starches. The α-amylase-loaded ultrafine fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and loadability and enzymatic activity evaluations. Incorporation of the enzyme resulted in a slight change in fiber morphology; the fibers became flatter and thicker with increasing enzyme concentration. The mean diameters ranged from 187 to 282 nm. FT-IR spectra indicated that the enzyme was incorporated into the fibers. PVA showed a high loading capacity for α-amylase at all concentrations tested (1.0, 1.5, and 2.0% w/v), indicating that PVA is an excellent support. The enzymatic activity of α-amylase was tested on the different starch substrates; the activity was higher in the immobilized form than in the free form. Enzymatic immobilization improved the stability of α-amylase over a wide range of temperatures and pHs. Enzymatic activity was highest when germinated wheat starch was used as the substrate at different temperatures and pHs, indicating great potential for its application in hydrolysis with α-amylase.

The ultrafine fibers were produced using a polymeric blend of soy protein isolate (SPI), polyethylene oxide (PEO), and zein at a ratio of 1:1:1 (v/v/v) by electrospinning. The ginger essential oil (GEO) was encapsulated in the ultrafine fibers and the morphology, Fourier-Transform Infrared Spectroscopy (FTIR) analysis, thermal properties and relative crystallinity were evaluated. The antimicrobial activity of ginger essential oil was evaluated against five bacteria (Listeria monocytogenes, Staphylococcus aureus, Escherichia coli 0157:H7, Salmonella typhimurium, and Pseudomonas aeruginosa). Based on the preliminary tests, the concentration of GEO selected to add in the polymer solution was 12% (v/v; GEO/polymer solution). The fiber produced with 12% (v/v) GEO was used for antimicrobial analysis and in situ application (in fresh Minas cheese) against L. monocytogenes by micro-atmosphere. The ultrafine fibers produced, regardless the concentration of the essential oil, presented homogeneous morphology with cylindrical shape without the presence of beads. The application of the active fibers containing 12% GEO showed high potential to be applied in food packaging to reduce microbial contamination.

The aim of this study was to produce ultrafine fibers from zein incorporated with a complex of eucalyptus essential oil (EEO) and β-cyclodextrin (β-CD) with antimicrobial properties by electrospinning technique. The EEO was characterized by chemical composition and antimicrobial tests against three Gram positive and four Gram negative bacteria. The inclusion complex (IC) was prepared with β-CD and EEO by co-precipitation technique and added at different concentrations in zein polymer solution using aqueous ethanol as solvent. The morphology, thermal properties, functional groups, and antimicrobial activity against L. monocytogenes and S. aureus of the ultrafine fibers were evaluated. The composite membranes containing 24% IC exhibited a greater reduction of growth as compared to the fibers without addition of IC. For L. monocytogenes the growth reduction was 28.5% and for S. aureus it was 24.3%. The electrospun IC-β-CD/EEO composite membranes are promising for use in antimicrobial applications, such as food packaging.

The aim of this study was to produce and characterize inclusion complexes (IC) between β-cyclodextrin (β-CD) and orange essential oil (OEO) or eucalyptus essential oil (EEO), and to compare these with their pure compounds and physical mixtures. The samples were evaluated by chemical composition, morphology, thermal stability, and volatile compounds by static headspace-gas chromatography (SH-GC). Comparing the free essential oil and physical mixture with the inclusion complex, of both essential oils (OEO and EEO), it was observed differences occurred in the chemical composition, thermal stability, and morphology. These differences show that there was the formation of the inclusion complex and demonstrate the necessity of the precipitation method used to guarantee the interaction between β-CD and essential oils. The slow loss of the volatile compounds from both essential oils, when complexed with β-CD, showed a higher stability when compared with their physical mixtures and free essential oils. Therefore, the results showed that the chemical composition, molecular size, and structure of the essential oils influence the characteristics of the inclusion complexes. The application of the β-CD in the formation of inclusion complexes with essential oils can expand the potential applications in foods.

Submitted by Gabriela Lopes (gmachadolopesufpel@gmail.com) on 2019-04-12T16:00:38Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese versao final pdf com ficha.pdf: 1971176 bytes, checksum: fcee724e9715ff1732bf42637512c767 (MD5) Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2019-04-17T18:26:42Z (GMT) No. of bitstreams: 2 Tese versao final pdf com ficha.pdf: 1971176 bytes, checksum: fcee724e9715ff1732bf42637512c767 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Made available in DSpace on 2019-04-17T18:26:42Z (GMT). No. of bitstreams: 2 Tese versao final pdf com ficha.pdf: 1971176 bytes, checksum: fcee724e9715ff1732bf42637512c767 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-12-17 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES A α-amilase é uma enzima muito utilizada na indústria alimentícia, porém, existem alguns fatores que podem afetar a sua eficiência e estabilidade, assim a imobilização surge como uma alternativa. O electrospinning está emergindo como uma tecnologia promissora para a imobilização de enzimas onde diversos polímeros podem ser utilizados. O álcool polivinílico (PVA) possui boas características para utilização como suporte na imobilização de enzimas, pois possui boas propriedades para produção de fibras por electrospinning, é biodegradável, biocompatível, entre outros. No entanto, as fibras elaboradas com PVA apresentam baixa estabilidade térmica. Visando aumentar a sua estabilidade térmica, a utilização de um agente de reticulação, como o glutaraldeído em fase de vapor, tem sido sugerida. O objetivo do estudo foi imobilizar α-amilase em fibras de PVA via electrospinning e aplicá-la em substratos de amido de milho, trigo germinado e trigo não germinado. Para tanto, soluções de PVA 8 % (p/v) foram adicionadas de α-amilase nas concentrações de 1, 1,5 e 2 % (p/v) e produzidas fibras ultrafinas via electrospinning. As fibras foram avaliadas quanto a morfologia e distribuição de tamanho, grupos funcionais e cadeia, atividade enzimática, capacidade de carregamento e estabilidade a diferentes temperaturas e pH’s. Em outra etapa foi realizada a reticulação com glutaraldeído em fase de vapor, nos tempos de 1, 2, 3 e 4 horas de exposição, utilizando as fibras com 1,5 % de α-amilase. Após a reticulação as fibras foram avaliadas quanto a morfologia, atividade enzimática e análise termogravimétrica. Os resultados mostraram que a incorporação da enzima ocasionou uma leve mudança na morfologia das fibras, apresentando fibras mais achatadas e espessas com o aumento da concentração da enzima. Os diâmetros médios variaram de 187 a 282 nm. Os espectros de FTIR indicaram que a enzima foi incorporada nas fibras. O PVA exibiu alta capacidade de carregamento para α-amilase em todas as concentrações testadas, mostrando ser um bom suporte para imobilização de enzimas. A imobilização enzimática melhorou a estabilidade da α-amilase em uma ampla faixa de temperatura e pH. O amido de trigo germinado apresentou maior valor de atividade enzimática, nas diferentes temperaturas e pH’s, apresentando um grande potencial para aplicação na hidrólise com α-amilase. Após a reticulação, a morfologia das fibras apresentou uma estrutura mais densa e compacta entre as fibras, resultado da interação química do glutaraldeído com o PVA e a α-amilase. Observou-se também uma diminuição da atividade enzimática após os diferentes tempos de exposição ao vapor de glutaraldeído. A análise de TGA apresentou um aumento da temperatura de decomposição inicial para as fibras, demonstrando uma maior estabilidade térmica das fibras reticuladas. A partir dos resultados obtidos é possível concluir que as membranas de PVA com α-amilase imobilizada 7 apresentaram boas características para utilização na hidrólise do amido de diferentes fontes. α-amylase is an enzyme widely used in the food industry, however, there are some factors that may affect its efficiency and stability and immobilization arises as an alternative. Electrospinning is emerging as a promising technology for the immobilization of enzymes where various polymers can be used. Polyvinyl alcohol (PVA) has good characteristics for use as a support in the immobilization of enzymes, since it has good fiber production capacity by electrospinning, it is biodegradable, biocompatible, among others. However, fibers made with PVA have low thermal stability. In order to increase its thermal stability, the use of a crosslinking agent, such as glutaraldehyde in the vapor phase, has been suggested. The aim of the study was to immobilize α-amylase in PVA fibers by electrospinning and apply it to substrates of corn starch, germinated wheat and ungerminated wheat. To that end, solutions of 8% (w / v) PVA were added α-amylase at concentrations of 1, 1.5 and 2% (w / v) and produced ultrafine fibers via electrospinning. The fibers were evaluated for morphology and size distribution, functional groups and chain, enzymatic activity, loading capacity and stability at different temperatures and pH's. In another step, glutaraldehyde cross-linking was carried out at 1, 2, 3 and 4 hours of exposure using the fibers with 1.5% α-amylase. After the crosslinking the fibers were evaluated for morphology, enzymatic activity and thermogravimetric analysis. The results showed that the incorporation of enzyme caused a slight change in the morphology of the fibers, presenting fibers more flattened and thicker with the increase of the enzyme concentration. The mean diameters ranged from 187 to 282 nm. FTIR spectra indicated that the enzyme was incorporated into the fibers. PVA exhibited high loading capacity for α-amylase at all concentrations tested, showing good support for immobilization of enzymes. Enzymatic immobilization improved α-amylase stability over a wide temperature range and pH. The germinated wheat starch presented higher value of enzymatic activity, at different temperatures and pH's, presenting a great potential for application in α-amylase hydrolysis. After the crosslinking, the fiber morphology presented a denser and more compact structure between the fibers, resulting from the chemical interaction of glutaraldehyde with PVA and α-amylase. A decrease in enzyme activity was also observed after different exposure times to glutaraldehyde vapor. The TGA analysis showed an increase in the initial decomposition temperature for the fibers, demonstrating a higher thermal stability of the crosslinked fibers. From the results obtained it is possible to conclude that the membranes of immobilized α-amylase PVA presented good characteristics for use in the hydrolysis of starch from different sources.

Biodegradable films of native or acetylated starches with different concentrations of cellulose fibers (0%, 10% and 20%) were prepared. The films were characterized by morphological, mechanical, barrier, and thermal properties.; Result: The tensile strength of the acetylated starch film was lower than those of the native starch film, without fibers. The addition of fibers increased the tensile strength and decreased the elongation and the moisture of native and acetylated starches films. The acetylated starch film showed higher water solubility when compared to native starch film. The addition of cellulose fibers reduced the water solubility of the acetylated starch film. The films reinforced with cellulose fiber exhibited a higher initial decomposition temperature and thermal stability.; Conclusion: The mechanical, barrier, solubility, and thermal properties are factors which direct the type of the film application in packaging for food products. The films elaborated with acetylated starches of low degree of substitution were not effective in a reduction of the water vapor permeability. The addition of the cellulose fiber in acetylated and native starches films can contribute to the development of more resistant films to be applied in food systems that need to maintain their integrity. © 2016 Society of Chemical Industry.; © 2016 Society of Chemical Industry.

The aim of this study was to produce and characterize inclusion complexes (IC) between β-cyclodextrin (β-CD) and orange essential oil (OEO) or eucalyptus essential oil (EEO), and to compare these with their pure compounds and physical mixtures. The samples were evaluated by chemical composition, morphology, thermal stability, and volatile compounds by static headspace-gas chromatography (SH-GC). Comparing the free essential oil and physical mixture with the inclusion complex, of both essential oils (OEO and EEO), it was observed differences occurred in the chemical composition, thermal stability, and morphology. These differences show that there was the formation of the inclusion complex and demonstrate the necessity of the precipitation method used to guarantee the interaction between β-CD and essential oils. The slow loss of the volatile compounds from both essential oils, when complexed with β-CD, showed a higher stability when compared with their physical mixtures and free essential oils. Therefore, the results showed that the chemical composition, molecular size, and structure of the essential oils influence the characteristics of the inclusion complexes. The application of the β-CD in the formation of inclusion complexes with essential oils can expand the potential applications in foods.

The objective of this work was to study the effect of enzymatic hydrolysis of black bean protein concentrate using different enzymes. Bean proteins were extracted and hydrolyzed over a period of 120 min using the enzymes pepsin or alcalase. The protein hydrolysates’ molecular weight was assayed by electrophoresis and the antioxidant activity was evaluated by the capturing methods of free radicals ABTS●+ and DPPH. Electrophoretic results showed that the bands above 50 kDa disappeared, when the beans protein was subjected to hydrolysis with pepsin. The bean protein hydrolysate obtained by hydrolysis with alcalase enzyme, showed higher antioxidant activity for inhibition of the radical ABTS●+. However, the hydrolysates obtained by hydrolysis with pepsin had higher antioxidant activity for inhibition of the radical DPPH. The use of pepsin and alcalase enzymes, under the same reaction time, produced black bean protein hydrolysates with different molecular weight profiles and superior antioxidant activity than the native bean protein.

Biodegradable films of native or acetylated starches with different concentrations of cellulose fibers (0%, 10% and 20%) were prepared. The films were characterized by morphological, mechanical, barrier, and thermal properties.The tensile strength of the acetylated starch film was lower than those of the native starch film, without fibers. The addition of fibers increased the tensile strength and decreased the elongation and the moisture of native and acetylated starches films. The acetylated starch film showed higher water solubility when compared to native starch film. The addition of cellulose fibers reduced the water solubility of the acetylated starch film. The films reinforced with cellulose fiber exhibited a higher initial decomposition temperature and thermal stability.The mechanical, barrier, solubility, and thermal properties are factors which direct the type of the film application in packaging for food products. The films elaborated with acetylated starches of low degree of substitution were not effective in a reduction of the water vapor permeability. The addition of the cellulose fiber in acetylated and native starches films can contribute to the development of more resistant films to be applied in food systems that need to maintain their integrity. © 2016 Society of Chemical Industry.

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