In this work an investigation to find new method of extraction of pectin from orange peel with shortening time of extraction is carried out. Pectin was extracted from dried orange peel at higher temperature by employing stainless steel reactors. In this investigation the effect of extraction conditions (temperature: 120, 150, 200°C; extraction time: 5, 15, 30 min) with sulphuric acid, on the yield and purity of citrus pectin was performed. Moreover, optimizing other methods of extraction and analyzing of pectin is tested. In addition, effect of adding special reagent such as Sodium polyphosphate to extract solvent examined. Furthermore, two different acids are used for extraction and the results are compared as described. Pectin is solubilized by HCl and H2SO4 at different concentrations, retention time and temperature. The effect of extraction conditions (pH: 1.5 to 2; temperature: 80 to 90°C; extraction time: 1 to 3 hours) with sulphuric acid, on the yield and purity of citrus pectin was carried out. The solubilized pectin is precipitated from the solution by using organic solvents such as 2-propanol and ethanol and then analysis was done with different methods such as carbozole and meta-hydroxy-diphenyl method. A same test was run for hydrochloric acid and comparison between them was done. / Uppsatsnivå: D

This work studied the effects of step size, angle, spindle speed, and feed rate on the external surface roughening, orange peel effect, observed in single point incremental forming (SPIF). Experimental results were used to estimate models to categorize the extent of orange peel roughening based on visual inspection and on surface roughness measurements. Tests were performed at very high rotational speeds and feed rates and showed various influences on surface roughness, thickness distribution, and grain size. Friction at the tool-sheet interface was also studied with a completely instrumented tool that measured and recorded torsion and forming forces through deformation strains. Coefficients of friction for each part were determined and through statistical analysis, the influence of each of the following forming parameters was established: material thickness, formed shape, tool size, step size, forming speeds (feed rate and rotational speed), and forming angle. Multidimensional response surfaces were generated to show when and under what condition friction was minimized. A new contact zone representation for SPIF was also established. This formulation used common forming parameters and geometric considerations to determine the contacting zone between the sheet and the tool. Area models were proposed for both the tangential and torsional component of friction in SPIF. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2010-02-01 16:47:17.249

The further usage of vegetable and plant waste from juice pressing industry as textile dyes is presented in this thesis. The thesis is focused on β-carotene (C40H56) dyestuff extracted from orange peel and carrot residue. The three organic solvents; ethyl acetate, petroleum ether and hexane/acetone (1:1 v/v) were used for the extraction. The analysis of the extract was done by RP-HPLC with a C18 column. The yield and the purity of the extracted β-carotene were determined. The highest yield was achieved with petroleum ether whereas the other two solvents were nearly as good. The highest and purest amount on β-carotene was found in the extracts of carrots. The dyeing process was continued with β-carotene dyestuff of orange peel and carrot residue extracted from 27 g of residue on 0,8 g cotton in the dyeing ratio 1:50. Unmordant and post mordanted bleached and mercerized cotton fabric was dyed. 10% alum of the weight fraction of cotton was used as mordant. Colour measurements (K/S, C*, L*, a*, b*, h and ΔE) and fastness properties as light- (ISO-Norm B02) and wash fastness (ISO 105 – C) were tested. Fair light fastness grades were achieved by β-carotene dyestuff of orange peel residue dyed on cotton fabric. Poorer were the grades for β-carotene dyestuff of carrot residue for both unmordanted and mordanted samples. The wash fastness couldn’t achieve reasonable results neither for β-carotene dyestuff from carrots nor orange peel residue, dyed on cotton fabric. / Program: Master programme in Textile Engineering

For the citrus processing industry the disposal of fresh peels has become a major concern for manyfactories. Orange peels are the major solid by-product. Dried orange peels have a high content ofpectin, cellulose and hemicellulose, which make it suitable as fermentation substrate when hydrolyzed.The present work aims at utilizing orange peels for the production of ethanol by using the fungusMucor indicus. Hence, producing a valuable product from the orange peel waste. The biomass growthwas also examined, since the biomass of the fungus can be processed into chitosan, which also is avaluable material.The work was first focused on examining the fungus ability to assimilate galacturonic acid and severalother sugars present in orange peel hydrolyzate (fructose, glucose, galactose, arabionose, and xylose).Fructose and glucose are the sugars which are consumed the fastest whereas arabinose, xylose andgalacturonic acid are assimilated much slower.One problem when using orange peels as raw material is its content of peel oils (mainly D-limonene),which has an immense antimicrobial effect on many microorganism even at low concentrations. Inorder to study M. indicus sensitivity to peel oil the fungus was grown in medium containing differentconcentrations of D-limonene.At very low limonene concentrations the fungal growth was delayed only modestly, hence a couple ofhours when starting from spores and almost nothing when starting with biomass. Increasing theconcentration to 0.25% (v/v) and above halted the growth to a large extent. However, the fungus wasable to grow even at a limonene concentration of 1.0%, although, at very reduced rate. Cultivationsstarted from spore-solution were more sensitive than those started with biomass.Orange peels were hydrolyzed by two different methods to fermentable sugars, namely by dilute acidhydrolysis (0.5% (v/v) H2SO4) at 150 °C and by enzymatic hydrolysis by cellulase, pectinase and β-glucosidase. The fungus was able to produce ethanol with a maximum yield of about 0.36 g/g after 24h when grown on acid hydrolyzed orange peels both by aerobic and anaerobic cultivation. Apreliminary aerobic cultivation on enzymatic hydrolyzed orange peels gave a maximum ethanol yieldof 0.33 g/g after 26 h.The major metabolite produced during the cultivations was ethanol. Apart from ethanol, glycerol wasthe only component produced in significant amounts. In cultivations performed aerobically on acidandenzymatic hydrolyzed orange peels the glycerol yields were 0.048 g/g after 24 h.Two different techniques were also examined in order to evaluate if the methods could be use asbiomass determining methods when solid particles are present in the culture medium. The problemwith solid particles is that they will be buried inside the fungal biomass matrix. Hence makingseparation impossible prior to dry weight determination in the ordinary way. However, none of themethods involving chitin extraction or chitosan extraction did show any good results.The results from the present work are rather clear, M. indicus was able to grow and produce bothethanol and biomass even when limonene was present in the culture medium. The maximum ethanolyield was achieved after about 24 h in cultivations performed on both acid hydrolyzed and enzymatichydrolyzed orange peels. However, in order to say if the method can be applicable at industrial scaleand made economically feasible the subject has to be investigated further.

Orange cultivation is a huge industry which increasing for each year. By the year 2010 theorange production of the world is expected to reach 66.4 million tons per year. Most of theoranges are used for orange juice production. Consequently, a large amount of organic wastes,including seeds, segment membranes and peel, counting up to half of the weight of usedoranges, are generated As alternatives to land filling and incineration, source separation andcomposting together with biogas production are being considered as suitable methods fortreating this fraction of wastes, because it holds a high amount of organic materials in form ofvaluable carbohydrate polymers. However, the presence of peel oil, limonene, known to haveantimicrobial effects, has showed to be a strong inhibitor for the biogas producingmicroorganisms. Therefore the orange peel waste (OP) was mixed with the organic fraction ofmunicipal solid waste (MSW) in this study to keep the concentration of this inhibitorycompound at low level.Based on the results from previous batch experiments, this study was performed in order toconfirm and develop the possible use of orange peel waste in biogas production. Since thebatch experiments showed that the methane production was not affected, when a mixture of70% MSW and 30% OP (calculated on the basis of volatile solids (VS) content added) wasused as substrate, a continuous anaerobic digestion experiment was performed using the samemixture of MSW and OP as a substrate in this study. Furthermore, a reactor utilizing onlyMSW was used as a control. Both reactors were operated during 35 days at thermophilicconditions (55ºC), with an organic loading rate of 3gVS/L/day and a hydraulic retention timeof 21 days. The methane production was around 0,5 Nm3/kgVS/day in both reactors duringthe first period of operation. However, the production of methane started to decrease after 20days followed by a sharp decrease during the last 5 days in the orange peel-containing reactor.Furthermore, a steadily increase (from 4,85g/L to 6,51g/L) in the total content of volatile fattyacids (VFA) could be observed here, while the total content of VFA in the control reactorremained at low levels (0,84g/L). A second experimental set up using a decreased amount ofOP (20% OP and 80% MSW) in the substrate mixture and operating at the same conditions sthe previous experiment was also performed and showed similar trends in the results. Thefailure of the process can be explained by inhibition in the system, which led to theaccumulation of VFA’s resulting in a decreased and finally no methane production. Thisinhibition might be caused by the accumulation of the inhibitory compound, limonene,presented in the orange peel waste. Therefore some treatment of the OP is necessary prior todigestion to avoid this inhibition. Batch digestion of treated vs untreated OP showed that themethane production of treated OP could be increased to 0,628 Nm3/kgVS compared to that of0,408 Nm3/kgVS from the untreated sample. Further investigations utilizing this treated OPfraction in continuous biogas process are necessary in the future.

Protein upgrading of orange peel waste was carried out by Solid Substrate Fermentation using an Aspergillus sp. inoculum in a waste peel mixture containing peel waste, potassium dihydrogen orthophosphate (KH2 PO4), ammonium sulphate [(NH4)2SO4] and molasses. Fermentation lasted 72 hours at 30C. after which crude protein level in the substrate increased from 5% to 13%. Factors found to be important in determing the efficiency of the fermentation process included fermentable sugar content of the medium, nitrogen and mineral levels, initial temperature, PH, moisture, agitation of the medium, and size of particles constituting the substrate. Protein quality of the fermented peel was evaluated by PEP assay and a PER value of 0.78 was recorded. It is suggested that a low level of total amino acids is the major contributory factor to this low PEP value. Total amino acid level measured 5.75g per 100g fermented peel waste. / Master of Science (Hons)

A big concern when painting surfaces is the unevenness of the surface texture that is created by the paint. This is a well known problem for the automotive industry, referred to as The Orange Peel Effect, creating a surface texture like that of an orange. This project aims to answer if the currently used Wave Scan could be replaced with the new Optimap to measure the Orange Peel Effect. A standardized measurement of this Orange Peel Effect are the N1 and N3 values, calculated through the BMW-Ford-scale and used by Volvo Trucks. In the first part of this report five models are created and evaluated to make the measurements from the new Optimap comparable with the currently used Wave Scan. In this report it is shown that N1 and N3 could be estimated such that hat(N1) = 2, 551813 + 0, 018900 ∗ Tb + 0, 089610 ∗ Td hat(N3) = 3, 862056 − 0, 014959 ∗ Tb + 0, 019958 ∗ Tc + 0, 067837 ∗ Td where Tb,Tc and Td are measurements from Optimap. By replacing Wave Scan with Optimap Volvo Trucks would be able to measure underlying layers like the matte base coat. Volvo suspects that the underlying layers could affect the top coats surface structure. If this is true it could then be further investigated and in turn optimized. This first part is modelled using measurements from plates which are painted with the truck cabs. These plates are measured with both tools and 110 paired measurements are used for the modelling. The variance is analyzed using another set of 24 plates with 6 replicates each, yielding 144 paired masurements. The two tools measures significantly differently for different wave lengths. Some of Optimaps measurements are also significantly different between the replicates of the same plate. The second part of this project is to evaluate the effect that the base coat has on the end product surface structure. Volvo Trucks is interested in the trends over time in the orange peel. This is done using data acquired from the production line, with truck cabs measured with base coat applied and cabs with top coat applied. Does the base coat follow the same trends? The result is that, due to lack of paired data, not enough evidence is found to either support nor reject the hypothesis that the base coat affects the end products surface texture. A significant difference between the different base coats is found. This is discussed and taken into account in the third part. The third part consists of a recommendation to Volvo Trucks on how to use the Optimap and further investigate the possible predictors of orange peel. This recommendation mainly focuses on reducing the number of variables. This could be done with only one type of top coat painted on the different base coats, using the same type of base surface for every measurement. The surface could then be measured before and after the top coat is applied to aquire paired data. This could be done in a laboratory in small-scale, and depending on the outcome more experiments could be constructed. In future studies one can investigate one of the base coats further. The same experiment could then be done with different alternations of one base coat instead of using several.

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2018-05-18T14:00:30Z No. of bitstreams: 1 PDF - Ketyla Karla Rodrigues do Nascimento.pdf: 25462207 bytes, checksum: 0fb2137c9613d2a8add8e97fc4299059 (MD5) / Made available in DSpace on 2018-05-18T14:00:30Z (GMT). No. of bitstreams: 1 PDF - Ketyla Karla Rodrigues do Nascimento.pdf: 25462207 bytes, checksum: 0fb2137c9613d2a8add8e97fc4299059 (MD5) Previous issue date: 2018-02-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / One of the great problems at the presente time is related to hydric availability and waters quality. The release of wastewater not treated properly, the water bodies exceeds in many places, the standards established by Resolution 357/2005 of the National Environmental Council - CONAMA. In the present study we evaluated the drying pear orange peel (Citrus sinensis L. Osbeck) at temperatures of 60 to 80 ° C, and the potential as a natural adsorbent for removing textile dye Tupy in burgundy color - 16. The research was divided into two phases, the first being drying the material and shaping of the experimental data and the second was the study of adsorption. Among the models used to describe the drying kinetics, the exponential model of two terms obtained best fit to the experimental data, according to the coefficient of determination (R^2)) and the F Test .It was performed chemical modification of the adsorbent with hydrochloric acid – 0,1 mole HCl. The characterization of the adsorbent occurred by determining the point of zero shit – pHpcz, infrared spectroscopy with Fourier transform – FTIR and scanning electron microscopy – SEM. The pHpcz for the dry material was 3,5 and the modified material was 2,5 with HCl. The factorial design 2^5 complete with the mass variable, concentration, pH, contact and chemical modification time was applied in order to optimize the adsorption process and evaluated the quantity responses adsorbed (qt) and a reduction in dye concentration (R%). For the qt response, all variables showed significant effect at the 95% confidence interval, and for response reduction only the variable concentration was not statistically significant. The kinetic assays were conducted at pH 4,0 and concentration of 200 mg.L-1, samples being collected every five minutes to 60 minutes for both adsorbents. The kinetic data were fitted to models of pseudo-first order and pseudo-second order equation Elovich, with the model of the pseudo-second order best fit to testing on the material without chemical modification. For the adsorbent modified with HCl the pseudo-first order model obtained best fit, presenting bigger values R2 and F Test. The values isotherms were constructed concentration ranging from 25 to 200 mg.L-1, pH 4,0. For data obtained with unmodified material, the Sips isotherm obtained the highest R^2 value and Test F and the data obtained with modified material, the Freundlich isotherm described in a more satisfactory manner. The adsorbent originating from orange peel was efficient for the removal of dye in the study. / Um dos grandes problemas da atualidade está relacionado à disponibilidade hídrica e à qualidade das águas. O lançamento de efluentes não tratados adequadamente, nos corpos hídricos, ultrapassa em muitos trechos, os padrões estabelecidos pela resolução 357/2005 do Conselho Nacional de Meio Ambiente – CONAMA. No presente estudo avaliou-se a secagem da casca de laranja pera (Citrus sinensis L. osbeck), nas temperaturas de 60 e 80 °C, e o potencial como adsorvente natural, para remoção do corante têxtil Tupy, na cor bordô – 16. A pesquisa foi dividida em duas fases, a primeira foi a secagem do material e modelagem dos dados experimentais, e a segunda foi o estudo da adsorção. Entre os modelos utilizados para descrever a cinética de secagem, o modelo exponencial de dois termos obteve melhor ajuste aos dados experimentais, de acordo com o coeficiente de determinação (R ) e o Teste F. Realizou-se a ativação ácida do adsorvente com ácido clorídrico - HCl 0,1 molar. A caracterização do adsorvente se deu através da determinação do ponto de caga zero – pHpcz, da espectroscopia de infravermelho com transformada de Fourier – FTIR e da micrografia de varredura eletrônica – MEV. O pHpcz para o material seco foi de 3,5 e para o material modificado com HCl foi 2,5. O planejamento fatorial 2 completo com as variáveis massa, concentração, pH, tempo de contato e ativação ácida foi aplicado com a finalidade de otimizar o processo de adsorção, sendo avaliadas as respostas quantidade adsorvida (qt) e redução na concentração de corante (R%). Para a resposta qt, todas as variáveis apresentaram efeito significativo ao intervalo de confiança de 95%, e para a resposta redução apenas a variável concentração não apresentou significância estatística. Os ensaios cinéticos foram realizados em pH 4,0 e concentração de 200 mg.L-1, sendo coletadas amostras a cada cinco minutos até 60 minutos, para ambos os adsorventes. Os dados cinéticos foram ajustados aos modelos de pseudo-primeira ordem, pseudo-segunda ordem e equação de Elovich, sendo o modelo de pseudo-segunda ordem o que melhor se ajustou aos ensaios com o material sem ativação ácida. Para o adsorvente modificado com HCl, o modelo pseudo-primeira ordem obteve melhor ajuste, apresentando maiores valores de R e Teste F. As isotermas foram construídas variando a concentração de 25 a 200 mg.L-1, com pH 4,0. Para os dados obtidos com material sem ativação química, a isoterma de Sips obteve maior valor de R^2 e Teste F, e para os dados obtidos com material modificado, a isoterma de Freundlich descreveu de maneira mais satisfatória. O adsorvente oriundo da casca da laranja se mostrou eficiente para a remoção do corante em estudo.

A utilização de antioxidantes sintéticos nas indústrias de biocombustíveis visando prolongar a vida útil destes materiais é comum, porém com a finalidade de se utilizar o maior número de matérias-primas renováveis na produção do biodiesel é que surgiu a ideia de se estudar a adição de produtos vegetais aos biodieseis, pois eles são ricos em compostos fenólicos (os principais responsáveis pela ação antioxidante). O trabalho foi executado em duas etapas, na qual a primeira consistiu em estudar, por meio da termogravimetria (TGA) a influência da adição das folhas de alecrim e da erva mate imersos nos biodieseis de canola e de girassol (ambos produzidos no laboratório) durante o período de 90 dias e na ausência de fatores pró-oxidantes. A segunda etapa consistiu na extração dos extratos vegetais das cascas de laranja, das folhas de alecrim e erva mate, por extração Soxhlet com a utilização do solvente orgânico diclorometano. Os extratos obtidos nesta etapa foram adicionados em diferentes proporções (1.000 mg/L e 2.000 mg/L) aos biodieseis de canola e girassol e expostos a duas diferentes condições. A condição I consistiu em expor os biodieseis aditivados ao ar atmosférico, luz e temperatura ambiente durante 60 dias e a condição II consistiu na exposição dos biodieseis ao aquecimento durante o mesmo período em uma estufa a 60°C. O estudo da influência dessas adições foi acompanhado por TGA e análise do índice de acidez. Ao final, constatou-se que as folhas de alecrim e erva mate diretamente adicionadas aos biodieseis e isolados de fatores pró-oxidação não apresentaram alterações significativas, uma vez que os biodieseis aditivados apresentaram valores de temperatura inicial de degradação (Ti) semelhantes. Por este motivo definiu-se outra etapa do trabalho, na qual os biodieseis aditivados foram expostos a fatores pró-oxidação, podendo-se dessa forma avaliar a eficiência das adições. Em paralelo, fez-se estudo semelhante com o produto sintético butil-hidroxitolueno (BHT), observando-se que nenhum dos extratos vegetais estudados superou sua ação antioxidante. Porém todos os extratos vegetais adicionados nos biodieseis apresentaram ação antioxidante no decorrer dos 60 dias, pois o B100 puro apresentou índice de acidez superior e Ti inferior ao das amostras aditivadas. As amostras aditivadas expostas à condição I apresentaram resultados próximos ao do B100 enquanto que na condição II foi possível observar a ação antioxidante dos extratos naturais e do produto sintético. Observou-se que dentre os biodieseis com extratos vegetais estudados, o B100 de canola com 2.000 mg/L do extrato de casca de laranja e o B100 de girassol com 2.000 mg/L do extrato de erva mate apresentaram melhor estabilidade termooxidativa. / The use of synthetic antioxidants at biofuel factories with the objective of extending the useful life of these fuels is common. However, it was bearing in mind the intent of using the greatest number of renewable resources in the production of biodiesel that the idea of studying the addition of plant products in biodiesel came up. This is because they are rich in phenolic compounds, which are responsible for the antioxidant activity. The study consisted of two stages. The first stage was to study, using thermogravimetry (TGA), the influence of rosemary leaves and yerba mate immersed in canola and sunflower biodiesel (both produced in labs) for a period of 90 days without any pro-oxidant factors. The second stage encompassed the extraction of plant extracts from orange peels, rosemary leaves, and yerba mate by Soxhlet extraction with the use of organic dichloromethane solvents. The extracts obtained at this point were added in different proportions (1,000 mg/L and 2,000 mg/L) in canola and sunflower biodiesel and exposed to two different conditions. The first condition was exposing the modified biodiesel to atmospheric air, light and room temperature during 60 days; the second condition consisted of exposing the biodiesel to heat during the same period in a greenhouse at 60 ºC. The influence of these additions and biodiesel exposures were tracked using TGA and acidity index analyses. At the end, it was clear that adding rosemary leaves and yerba mate directly into biodiesels and isolating them from pro-oxidant factors resulted in no significant contributions coming from these products since both the unmodified biodiesels and the modified biodiesels showed similar Ti values (initial degradation temperature). For this reason, it was necessary to start another work phase, where all biodiesels were exposed to pro-oxidant factors, making possible the analysis of the efficiency of the additions. No plant extract exceeded the antioxidant action of the BHT (butylated hydroxytoluene), however they all showed antioxidant activity during the 60-day period since pure B100 showed higher acidity index levels and lower Ti levels compared to the modified samples. The biodiesels exposed to the first condition showed similar results in the pure B100 and the modified B100, unlike what happened with the samples exposed to heat. When the biodiesels were exposed to heat, the activity of the additives became clearer. It was possible to conclude that among the biodiesels with added plant extracts, the canola B100 added with 2,000 mg/L of orange peel extract and sunflower B100 added with 2,000 mg/L of yerba mate extract showed higher thermal-oxidative stability.

A utilização de antioxidantes sintéticos nas indústrias de biocombustíveis visando prolongar a vida útil destes materiais é comum, porém com a finalidade de se utilizar o maior número de matérias-primas renováveis na produção do biodiesel é que surgiu a ideia de se estudar a adição de produtos vegetais aos biodieseis, pois eles são ricos em compostos fenólicos (os principais responsáveis pela ação antioxidante). O trabalho foi executado em duas etapas, na qual a primeira consistiu em estudar, por meio da termogravimetria (TGA) a influência da adição das folhas de alecrim e da erva mate imersos nos biodieseis de canola e de girassol (ambos produzidos no laboratório) durante o período de 90 dias e na ausência de fatores pró-oxidantes. A segunda etapa consistiu na extração dos extratos vegetais das cascas de laranja, das folhas de alecrim e erva mate, por extração Soxhlet com a utilização do solvente orgânico diclorometano. Os extratos obtidos nesta etapa foram adicionados em diferentes proporções (1.000 mg/L e 2.000 mg/L) aos biodieseis de canola e girassol e expostos a duas diferentes condições. A condição I consistiu em expor os biodieseis aditivados ao ar atmosférico, luz e temperatura ambiente durante 60 dias e a condição II consistiu na exposição dos biodieseis ao aquecimento durante o mesmo período em uma estufa a 60°C. O estudo da influência dessas adições foi acompanhado por TGA e análise do índice de acidez. Ao final, constatou-se que as folhas de alecrim e erva mate diretamente adicionadas aos biodieseis e isolados de fatores pró-oxidação não apresentaram alterações significativas, uma vez que os biodieseis aditivados apresentaram valores de temperatura inicial de degradação (Ti) semelhantes. Por este motivo definiu-se outra etapa do trabalho, na qual os biodieseis aditivados foram expostos a fatores pró-oxidação, podendo-se dessa forma avaliar a eficiência das adições. Em paralelo, fez-se estudo semelhante com o produto sintético butil-hidroxitolueno (BHT), observando-se que nenhum dos extratos vegetais estudados superou sua ação antioxidante. Porém todos os extratos vegetais adicionados nos biodieseis apresentaram ação antioxidante no decorrer dos 60 dias, pois o B100 puro apresentou índice de acidez superior e Ti inferior ao das amostras aditivadas. As amostras aditivadas expostas à condição I apresentaram resultados próximos ao do B100 enquanto que na condição II foi possível observar a ação antioxidante dos extratos naturais e do produto sintético. Observou-se que dentre os biodieseis com extratos vegetais estudados, o B100 de canola com 2.000 mg/L do extrato de casca de laranja e o B100 de girassol com 2.000 mg/L do extrato de erva mate apresentaram melhor estabilidade termooxidativa. / The use of synthetic antioxidants at biofuel factories with the objective of extending the useful life of these fuels is common. However, it was bearing in mind the intent of using the greatest number of renewable resources in the production of biodiesel that the idea of studying the addition of plant products in biodiesel came up. This is because they are rich in phenolic compounds, which are responsible for the antioxidant activity. The study consisted of two stages. The first stage was to study, using thermogravimetry (TGA), the influence of rosemary leaves and yerba mate immersed in canola and sunflower biodiesel (both produced in labs) for a period of 90 days without any pro-oxidant factors. The second stage encompassed the extraction of plant extracts from orange peels, rosemary leaves, and yerba mate by Soxhlet extraction with the use of organic dichloromethane solvents. The extracts obtained at this point were added in different proportions (1,000 mg/L and 2,000 mg/L) in canola and sunflower biodiesel and exposed to two different conditions. The first condition was exposing the modified biodiesel to atmospheric air, light and room temperature during 60 days; the second condition consisted of exposing the biodiesel to heat during the same period in a greenhouse at 60 ºC. The influence of these additions and biodiesel exposures were tracked using TGA and acidity index analyses. At the end, it was clear that adding rosemary leaves and yerba mate directly into biodiesels and isolating them from pro-oxidant factors resulted in no significant contributions coming from these products since both the unmodified biodiesels and the modified biodiesels showed similar Ti values (initial degradation temperature). For this reason, it was necessary to start another work phase, where all biodiesels were exposed to pro-oxidant factors, making possible the analysis of the efficiency of the additions. No plant extract exceeded the antioxidant action of the BHT (butylated hydroxytoluene), however they all showed antioxidant activity during the 60-day period since pure B100 showed higher acidity index levels and lower Ti levels compared to the modified samples. The biodiesels exposed to the first condition showed similar results in the pure B100 and the modified B100, unlike what happened with the samples exposed to heat. When the biodiesels were exposed to heat, the activity of the additives became clearer. It was possible to conclude that among the biodiesels with added plant extracts, the canola B100 added with 2,000 mg/L of orange peel extract and sunflower B100 added with 2,000 mg/L of yerba mate extract showed higher thermal-oxidative stability.