Thesis (M. Sc. (Agriculture)) -- University of Limpopo, 2004 / National Research Foundation (NRF)

<p>The objective for this master’s thesis was to test and evaluate two methods for determining the content of tannin in a pinebarkextract. The methods used at Södra for this previously have not been specific enough, only the amount of polyphenolics have been measured. One of these methods is a test based on the Stiasny test and it determines the extracts ability to form a gel with formaldehyde. When this test was carried out it showed that the extract did not contain much tannin. The other method used at Södra measures the amount of polyphenolic substances with a spectrophotometer. The result from this method showed that the content were 50 %.</p><p> </p><p>One of the two new methods that were evaluated determines the amount tannin present in the extract because of tannins ability to form a complex with proteins. According to this method, the amount tannin in the extract were 42,5 %, and 19,4 % of this in the form of tannic acid. These results are credible on basis of previous information about the extract.</p><p> </p><p>The other method uses a RP- HPLC where ellagic and gallic acid were used as standards. The amount ellagic acid in the extract was determined to 0,06 %, but the result from gallic acid was inconclusive. Further analysis is necessary to evaluate the obtained results and the methods reliability.</p><p> </p><p>If the metods is to be used on a regular basis, my recommendation would be to start evaluating the protein-binding method because this would be easier and less time-consuming than modifying the HPLC- method. The HPLC- method could on the other hand provide useful information about the extract, not only the amount tannin could be measured, but also which kind of tannin could be investigated.</p>

The objective for this master’s thesis was to test and evaluate two methods for determining the content of tannin in a pinebarkextract. The methods used at Södra for this previously have not been specific enough, only the amount of polyphenolics have been measured. One of these methods is a test based on the Stiasny test and it determines the extracts ability to form a gel with formaldehyde. When this test was carried out it showed that the extract did not contain much tannin. The other method used at Södra measures the amount of polyphenolic substances with a spectrophotometer. The result from this method showed that the content were 50 %.   One of the two new methods that were evaluated determines the amount tannin present in the extract because of tannins ability to form a complex with proteins. According to this method, the amount tannin in the extract were 42,5 %, and 19,4 % of this in the form of tannic acid. These results are credible on basis of previous information about the extract.   The other method uses a RP- HPLC where ellagic and gallic acid were used as standards. The amount ellagic acid in the extract was determined to 0,06 %, but the result from gallic acid was inconclusive. Further analysis is necessary to evaluate the obtained results and the methods reliability.   If the metods is to be used on a regular basis, my recommendation would be to start evaluating the protein-binding method because this would be easier and less time-consuming than modifying the HPLC- method. The HPLC- method could on the other hand provide useful information about the extract, not only the amount tannin could be measured, but also which kind of tannin could be investigated.

Whole-grain, high-fiber, or decorticated extrudates of excellent properties were made from white (nonwaxy, heterowaxy, waxy) sorghums or brown tannin-sorghums. Intact grains or prepared raw materials (cracked, cracked and sifted, decorticated) were extruded in a high-temperature, short-time (HTST) extruder. Waxy extrudates expanded less and were softer than those from nonwaxy or heterowaxy sorghums. Waxy extrudates had bigger air cells and thicker cell walls. Low moisture used in this type of extrusion and its interaction with the different amylose contents were the causes of the differences. Whole-grain extrudates from white sorghum had similar sensory acceptability to those from white decorticated sorghum. They had bland flavor and appearance and texture characteristic of whole-grain products. Extrudates from tannin sorghums were reddish brown due to their high levels of phytochemicals. The more expanded, softer products from whole-grain tannin sorghum were obtained when the grain was cracked and sifted. Decreased expansion was caused by higher levels of fiber and greater particle sizes (as in the extruded intact grain), and by reduced particle sizes (as in the cracked non-sifted grain). Expansion was correlated to smaller air cells with smooth walls. A simple enzymatic method was developed that isolates the 'gritty' particles from whole-grain/high-fiber extrudates, which closely correlated with expansion. Gritty particles were fiber (bran) plus undegraded starchy material. Whole grain/high fiber extrudates from white and tannin sorghums are an excellent option for food processors because of their excellent taste, appearance and texture.

As sessile organisms, plants are unable to escape from attack by herbivorous insects. To cope with this pressure, plants have evolved several defense strategies, including the production of secondary metabolites, specialized chemicals with ecological functions. Most studies have focused on the role of secondary metabolites in plant defense against chewing insects. Little is known about what compounds are present in phloem sap and how they affect phloem feeding insects. Therefore, I investigated the effects of phenolic compounds on phloem feeders, using Chaitophorus aphids in bioassays with wildtype and transgenic poplar overexpressing the transcription factor MYB 134, which results in elevated levels of tannins and reduced levels of phenolic glycosides. Aphids produced significantly more offspring on MYB 134 plants but showed a significant preference for lower tannin leaf tissue. Analysis of poplar phloem exudates and aphid extracts provides direct evidence that the phenolic glycosides salicin, salicortin and tremulacin are present in poplar phloem and are ingested by aphids. These results are discussed in relation to what is driving the differences in aphid fecundity and choice between plant types. / Graduate / 0309 / 0307 / 0329 / alphareghanwong@gmail.com

Orientador: Marcos Hikari Toyama / Resumo: A explosão respiratória está fortemente associada ao processo inflamatório, uma vez que diversos compostos antioxidantes estão envolvidos na potencialização ou neutralização deste processo. Diversos peróxidos inorgânicos e orgânicos são produzidos durante esse processo, como os hidroperóxidos de lipídio. Hidroperóxidos de lipídio são estáveis, extremamente reativos e podem induzir a apoptose celular. Tais lipídios modificados podem ser produzidos durante o processo inflamatório induzido pelas fosfolipases A2 (PLA2) que constituem o veneno de serpentes, que possui como consequência de sua atividade catalítica a produção de ácido araquidônico pela quebra de fosfolipídios de membrana, e estes então seriam oxidados por espécies reativas de oxigênio (ROS), formando os hidroperóxidos araquidônicos, que agravam o quadro inflamatório. Deste modo, nesse trabalho avaliamos o efeito protetor de compostos polifenólicos e extratos ricos em tais compostos de diferentes espécies vegetais no curso da inflamação e miotoxidade e no efeito inflamatório pró-oxidante induzido pela PLA2 purificada de veneno crotálico e botrópico. Nossos resultados mostraram que diversos compostos polifenólicos são capazes de diminuir os efeitos provocados pela PLA2, interagindo diretamente, inibindo a enzima e possivelmente atuando na captura de ROS. / Abstract: Respiratory burst is strongly associated with inflammatory process, since several antioxidant compounds are involved in potentiation or neutralization of this process. Various inorganic and organic peroxides are produced during this process such as lipid hydroperoxides. Lipid hydroperoxides are stable, highly reactive and can induce cellular apoptosis. Such modified lipids can be produced during the inflammatory process induced by phospholipases A2 (PLA2) which are present in snake venom, and produces, because of its catalytic activity, arachidonic acid by the breakdown of membrane phospholipids, and these would then be oxidized by reactive oxygen species (ROS), forming the arachidonic hydroperoxides, which aggravates inflammation. Thus, in this work we evaluated the protective effect of polyphenolic compounds and extracts rich in such compounds of different plant species throughout the inflammation and myotoxicity and in pro-oxidant effect induced by PLA2 purified from bothrops and crotalus venom. Our results showed that polyphenolic compounds can decrease effects caused by PLA2, by directly interaction, inhibiting the enzyme and possible acting to capture ROS. / Doutor

A proteção contra a corrosão do aço galvanizado com um tratamento via cromatização, apesar de apresentar desempenho superior à outras alternativas, gera efluentes tóxicos ao meio ambiente e em especial aos seres humanos. Dentre as alternativas apresentadas até o presente momento, que incluem diversos tipos de tratamentos para esse substrato, um deles é o revestimento com silanos. Apesar desse revestimento ter um satisfatório desempenho, vem se utilizando incorporações em seu preparo, para se potencializar seu desempenho. A incorporação escolhida nesse trabalho foi a do tanino, um inibidor de corrosão natural, extraído de vegetais. O objetivo desse trabalho é avaliar um revestimento do silano Ortossilicato de tetraetila (TEOS) junto de um tanino para o aço galvanizado destinado a aplicações onde não há pintura. Essa sinergia deve proteger a superfície até que o zinco consiga de forma natural desenvolver sua pátina protetora, formando uma barreira entre substrato e eletrólito. Foram revestidas chapas de aço galvanizado com períodos de imersão que variaram entre 2 e 10 minutos, com soluções na concentração de tanino de 2g/L e 10g/L com diferentes valores de pH, em uma solução previamente preparada de TEOS em concentração de 2%, água 49% e etanol 49%. Realizou-se análise comparativa entre os diferentes parâmetros de tratamento proposto neste trabalho com aço galvanizado somente desengraxado e aço galvanizado cromatizado nas seguintes técnicas: espectroscopia de impedância eletroquímica, polarização potenciodinâmica, microscopia eletrônica de varredura acoplada a espectroscopia de energia dispersiva, e ensaios de corrosão acelerada em câmara úmida e névoa salina. Os resultados apresentados indicam que diferentes concentrações de tanino e tempos de imersão não são significativos para causar diferenças relevantes entre os desempenhos e que os substratos tratados demonstraram um desempenho superior comparado às amostras que não tinham nenhum tipo de tratamento e inferiores às amostras cromatizadas. / The corrosion protection of galvanized steel with a chromatized treatment, despite superior performance to other alternatives, generates effluents toxic to the environment and especially to humans. Among the alternatives presented to date, which include several types of treatments for this substrate, one of them is the coating with silanes. Although this coating has a satisfactory performance, it has been using incorporations in its preparation, to enhance its performance. The incorporation chosen in this work was that of tannin, a natural corrosion inhibitor, extracted from plants. The objective of this work is to evaluate a coating of silane tetraethyl orthosilicate (TEOS) with tannin for galvanized steel, for applications where there is no paint. This synergy should protect the surface until zinc can naturally develop its protective patina, forming a barrier between substrate and electrolyte. Galvanized steel plates were coated with immersion times ranging from 2 to 10 minutes, with solutions at tannin concentration of 2 g/L and 10 g/L with different pH values, in a previously prepared solution of TEOS at a concentration of 2% , 49% of water and 49% of ethanol. A comparative analysis was performed between the different treatment parameters proposed in this work with galvanized steel only degreased and galvanized steel chromatized in the following techniques: electrochemical impedance spectroscopy (EIE), potentiodynamic polarization, scanning electron microscopy coupled to dispersive energy spectroscopy, and corrosion tests accelerated in humid chamber and saline mist. The results indicated that different concentrations of tannin and immersion times are not significant to cause relevant differences between the performances and that the substrates demonstrated superior performance compared to the samples that had no type of treatment, and inferior to the samples chromatized.

A proteção contra a corrosão do aço galvanizado com um tratamento via cromatização, apesar de apresentar desempenho superior à outras alternativas, gera efluentes tóxicos ao meio ambiente e em especial aos seres humanos. Dentre as alternativas apresentadas até o presente momento, que incluem diversos tipos de tratamentos para esse substrato, um deles é o revestimento com silanos. Apesar desse revestimento ter um satisfatório desempenho, vem se utilizando incorporações em seu preparo, para se potencializar seu desempenho. A incorporação escolhida nesse trabalho foi a do tanino, um inibidor de corrosão natural, extraído de vegetais. O objetivo desse trabalho é avaliar um revestimento do silano Ortossilicato de tetraetila (TEOS) junto de um tanino para o aço galvanizado destinado a aplicações onde não há pintura. Essa sinergia deve proteger a superfície até que o zinco consiga de forma natural desenvolver sua pátina protetora, formando uma barreira entre substrato e eletrólito. Foram revestidas chapas de aço galvanizado com períodos de imersão que variaram entre 2 e 10 minutos, com soluções na concentração de tanino de 2g/L e 10g/L com diferentes valores de pH, em uma solução previamente preparada de TEOS em concentração de 2%, água 49% e etanol 49%. Realizou-se análise comparativa entre os diferentes parâmetros de tratamento proposto neste trabalho com aço galvanizado somente desengraxado e aço galvanizado cromatizado nas seguintes técnicas: espectroscopia de impedância eletroquímica, polarização potenciodinâmica, microscopia eletrônica de varredura acoplada a espectroscopia de energia dispersiva, e ensaios de corrosão acelerada em câmara úmida e névoa salina. Os resultados apresentados indicam que diferentes concentrações de tanino e tempos de imersão não são significativos para causar diferenças relevantes entre os desempenhos e que os substratos tratados demonstraram um desempenho superior comparado às amostras que não tinham nenhum tipo de tratamento e inferiores às amostras cromatizadas. / The corrosion protection of galvanized steel with a chromatized treatment, despite superior performance to other alternatives, generates effluents toxic to the environment and especially to humans. Among the alternatives presented to date, which include several types of treatments for this substrate, one of them is the coating with silanes. Although this coating has a satisfactory performance, it has been using incorporations in its preparation, to enhance its performance. The incorporation chosen in this work was that of tannin, a natural corrosion inhibitor, extracted from plants. The objective of this work is to evaluate a coating of silane tetraethyl orthosilicate (TEOS) with tannin for galvanized steel, for applications where there is no paint. This synergy should protect the surface until zinc can naturally develop its protective patina, forming a barrier between substrate and electrolyte. Galvanized steel plates were coated with immersion times ranging from 2 to 10 minutes, with solutions at tannin concentration of 2 g/L and 10 g/L with different pH values, in a previously prepared solution of TEOS at a concentration of 2% , 49% of water and 49% of ethanol. A comparative analysis was performed between the different treatment parameters proposed in this work with galvanized steel only degreased and galvanized steel chromatized in the following techniques: electrochemical impedance spectroscopy (EIE), potentiodynamic polarization, scanning electron microscopy coupled to dispersive energy spectroscopy, and corrosion tests accelerated in humid chamber and saline mist. The results indicated that different concentrations of tannin and immersion times are not significant to cause relevant differences between the performances and that the substrates demonstrated superior performance compared to the samples that had no type of treatment, and inferior to the samples chromatized.

Amongst cereals, sorghum is one of the major sources of phenolic compounds. South African cultivars have not been profiled for their phenolic content and antioxidant activity to highlight their potential benefits. Thus, South African sorghum cultivars representing different sorghum types were evaluated for total phenolic content, condensed tannin content and antioxidant activity and the effect of cultivar on their antioxidant activity. The presence of phenolic antioxidants in the different sorghum cultivars, created an opportunity to develop a sorghum product as a vector of the antioxidants. Cookies were a product of choice due to their shelf stability and high nutrient density. Sorghum cookies were produced from 70%, 90% and 100% extraction rate flours. The effects of flour extraction rates and cultivar on the total phenolic content, condensed tannin content and antioxidant activity of the cookies were determined. Consumer sensory evaluation was used to evaluate sorghum cookie acceptability against a wheat flour cookie. Total phenolic content of the cultivars, determined by the Folin-Ciocalteu method was 0.20 to 1.42 g catechin equivalents (CE)/100 g. The total phenolic content was 3 to 7 times higher in condensed tannin cultivars than in tannin-free cultivars. Using the modified Vanillin-HCl method, condensed tannins were only measurable in the condensed tannin cultivars. They ranged between 5.16 and 8.39 g CE/100 g. Subsequently, the antioxidant activity of the condensed tannin cultivars measured by the ABTS radical scavenging assay was up to 4 times higher than in the tannin-free cultivars. The high phenolic content and antioxidant activity of condensed tannin cultivars was attributed to the contribution of condensed tannins. Therefore, condensed tannin cultivars are a major source of antioxidants compared to tannin-free cultivars. For each sorghum cultivar, cookies of 100% extraction rate flours had 2 to 3 times higher total phenolics compared to those of 70% extraction rate flours, while antioxidant activity was 2 to 10 times higher. Cookies of the condensed tannin sorghum had 2 to 5 times more phenolics compared to those of condensed tannin-free sorghum. Antioxidant activity was 145 to 227 ìMol Trolox equivalents (TE)/g in cookies of condensed tannin sorghum compared to 10 to 102 ìMol TE/g in those of condensed tannin-free sorghum. Processing sorghum flours to cookies seemed to reduce phenolic and antioxidant activity, but considering the flour component in the formula, cookie antioxidant activity was slightly higher than that of flours. The texture of all sorghum cookies was less acceptable compared to that of wheat cookies. The consumers showed a slight overall liking of the condensed tannin-free sorghum and wheat flour cookies. The cookies from condensed tannin flours were neither liked nor disliked. Since generally wheat flour is used for making cookies, the similarities in the overall liking of the condensed tannin-free sorghum cookies and the wheat flour cookies indicate strong potential of sorghum flour for cookie making. Therefore, sorghum cookies have a potential as a functional ready-to-eat snack, with target consumers such as school children in feeding schemes to improve their health and nutrition status. / Dissertation (MSc)--University of Pretoria, 2009. / Food Science / unrestricted

The perception of wine’s quality is directly influenced by its color. Anthocyanin molecules are responsible for imparting color to red wines. They are extracted from grape skins during alcoholic fermentation. This work compares the effects of three parameters: berry integrity, enzyme addition, and fermentation temperature, on phenolic compound extraction (total phenol, tannin and anthocyanin) during the production of Paso Robles’ Cabernet Sauvignon wine. Analyses on phenolic compounds were completed during alcoholic fermentation and barrel aging over the course of eighteen months. Berry integrity compared the degree of berry crushing (whole destemmed berries versus fully crushed berries). Results showed that phenolic compound content after alcoholic fermentation seem to be unaffected by this parameter, while minor increases in total phenol concentration (3%) and tannin concentration (3%) during barrel aging were observed. Adding pectinase-rich macerating enzymes increased the total phenols by 8.7 and 21.0% to the 2010 and 2011 vintage, respectively, and tannin concentrations by 20.8 and 48.8%, respectively, during barrel aging. Alcoholic fermentation temperature of 25.0°C was compared to a fermentation temperature of 32.2°C in the 2011 vintage. When fermented at 32.2°C, concentrations of total phenol and tannin were significantly increased (20.6% and 28.9%, for the 2010 and 2011 vintages, respectively) when compared to 25.0°C. A cooler fermentation temperature led to 57.5% greater anthocyanin concentration throughout barrel aging. The results suggested that fermenting berries at a cooler temperature (25.0°C) increased anthocyanin levels and decreased total phenol and tannin concentration, which are desired outcomes for Paso Robles’ Cabernet Sauvignon wine quality.