Perfil de solutos e micotoxinas nas águas do cultivo e beneficiamento do arroz

O cultivo do arroz no RS é fortemente relacionado com recursos hídricos, pois este se faz sob irrigação e durante o beneficiamento, especialmente no caso da parboilização, são necessários volumes consideráveis de água. Em vista disso, os solutos presentes nestas águas permitem estimar o impacto desta cultura e sua industrialização na qualidade do ambiente hídrico no RS. Foi desenvolvida uma rotina analítica para caracterização físico-química das águas da cadeia produtiva do arroz, onde foram analisados nitrogênio total, nitrogênio amoniacal, nitrogênio orgânico, açucares redutores, açucares redutores totais, sólidos totais, sólidos fixos, sólidos voláteis, ácidos voláteis, alcalinidade, pH, nitrato, nitrito e fósforo. Também um método multimicotoxinas foi desenvolvido avaliando a eficiência de cinco sistemas de extração-partição para aflatoxina B1 (AFA B1), aflatoxina B2 (AFA B2), ocratoxina A (OTA), zearalenona (ZEA) e deoxinivalenol (DON). A partição liquido-liquido com clorofórmio foi a mais eficiente recuperando 89; 96; 89; 97 e 72%, respectivamente de cada micotoxina. A comparação entre volumes de solventes, onde o número de etapas envolvidas e o tempo necessário para efetuar a determinação confirmaram a simplicidade, a economia e a rapidez deste sistema de partição a ser adotado para extrair micotoxinas de água da cadeia produtiva de arroz. O método foi aplicado para determinação de micotoxinas em amostras de águas de irrigação e parboilização de arroz de diferentes procedências verificando-se que as últimas aparecem contaminadas com micotoxinas, AFA B1 9,0 ng mL-1 e DON 110 ng mL-1 . Foi realizado também um estudo de migração de micotoxinas AFA B1, OTA, ZEA e DON e outros solutos sob condições de encharcamento (4 e 6 h) em dois níveis de fortificação, durante a parboilização do grão ficando demonstrado que durante o processo ocorria a lixiviação de solutos e micotoxinas para água de encharcamento do arroz.

Reducing acrylamide precursors in raw materials derived from wheat and potato

A review of agronomic and genetic approaches as strategies for the mitigation of acrylamide risk in wheat and potato is presented. Acrylamide is formed through the Maillard reaction during high-temperature cooking, such as frying, roasting, or baking, and the main precursors are free asparagine and reducing sugars. In wheat flour, acrylamide formation is determined by asparagine levels and asparagine accumulation increases dramatically in response to sulfur deprivation and, to a much lesser extent, with nitrogen feeding. In potatoes, in which sugar concentrations are much lower, the relationships between acrylamide and its precursors are more complex. Much attention has been focused on reducing the levels of sugars in potatoes as a means of reducing acrylamide risk. However, the level of asparagine as a proportion of the total free amino acid pool has been shown to be a key parameter, indicating that when sugar levels are limiting, competition between asparagine and the other amino acids for participation in the Maillard reaction determines acrylamide formation. Genetic approaches to reducing acrylamide risk include the identification of cultivars; and other germplasm in which free asparagine and/or sugar levels are low and the manipulation of genes involved in sugar and amino acid metabolism and signaling. These approaches are made more difficult by genotype/ environment interactions that can result in a genotype being "good" in one environment but "poor" in another. Another important consideration is the effect that any change could have on flavor in the cooked product. Nevertheless, as both wheat and potato are regarded as of relatively high acrylamide risk compared with, for example, maize and rice, it is essential that changes are achieved that mitigate the problem.

Concentrations of free amino acids and sugars in nine potato varieties: effects of storage and relationship with acrylamide formation

Acrylamide forms during cooking and processing predominately from the reaction of free asparagine and reducing sugars in the Maillard reaction. The identification of low free asparagine and reducing sugar varieties of crops is therefore an important target. In this study, nine varieties of potato (French fry varieties Maris Piper (from two suppliers), Pentland Dell, King Edward, Daisy, and Markies; and chipping varieties Lady Claire, Lady Rosetta, Saturna, and Hermes) grown in the United Kingdom in 2009 were analyzed at monthly intervals through storage from November 2009 to July 2010. Acrylamide formation was measured in heated flour and chips fried in oil. Analysis of variance revealed significant interactions between varieties nested within type (French fry and chipping) and storage time for most free amino acids, glucose, fructose, and acrylamide formation. Acrylamide formed in chips correlated significantly with acrylamide formed in flour and with chip color. There were significant correlations between glucose or total reducing sugar concentration and acrylamide formation in both variety types, but with fructose the correlation was much stronger for chipping than for French fry varieties. Conversely, there were significant correlations with acrylamide formation for both total free amino acid and free asparagine concentration in the French fry but not chipping varieties. The study showed the potential of variety selection for preventing unacceptable levels of acrylamide formation in potato products and the variety-dependent effect of long-term storage on acrylamide risk. It also highlighted the complex relationship between precursor concentration and acrylamide risk in potatoes.

The reduction of Cu(II)/neocuproine complexes by some polyphenols: Total polyphenols determination in wine samples

A new method is presented for spectrophotometric determination of total polyphenols content in wine. The procedure is a modified CUPRAC method based on the reduction of Cu(II), in hydroethanolic medium (pH 7.0) in the presence of neocuproine (2,9-dimethyl-1,10-phenanthroline), by polyphenols, yielding a Cu(I) complexes with maximum absorption peak at 450 nm. The absorbance values are linear (r = 0.998, n = 6) with tannic acid concentrations from 0.4 to 3.6 mu mol L(-1). The limit of detection obtained was 0.41 mu mol L(-1) and relative standard deviation 1.2% (1 mu mol L(-1); n = 8). Recoveries between 80% and 110% (mean value of 95%) were calculated for total polyphenols determination in 14 commercials and 2 synthetic wine samples (with and without sulphite). The proposed procedure is about 1.5 more sensitive than the official Folin-Ciocalteu method. The sensitivities of both methods were compared by the analytical responses of several polyphenols tested in each method. (C) 2010 Elsevier Ltd. All rights reserved.

Ciclo de cultivo e técnicas pós-colheita de yacon (Polymnia sonchifolia Poep. Endl.) em função do conteúdo de frutose total nos órgãos subterrâneos

Pós-graduação em Agronomia (Horticultura) - FCA

Trehalose Toxicity in Cuscuta reflexa - Sucrose Content Decreases In Shoot Tips Upon Trehalose Feeding

Trehalose, an alpha,alpha-diglucoside, induced a rapid blackening and death of shoot tips of Cuscuta reflexa (dodder) cultured in vitro. The onset of toxic symptom was delayed if any of the several sugars which support the in vitro growth of Cuscuta was supplied with trehalose. The rate of trehalose uptake or its accumulation in the tissue was not affected by sugar cofeeding. The levels of total and reducing sugars declined appreciably in the trehalose-fed shoot tip explants compared to control tissue cultured in absence of a carbon source. This was not due to an increased rate of respiration of the trehalose-treated tissue. In shoot tips cultured in presence of both trehalose and sucrose, the decline in total and reducing sugars was curtailed. There was a marked fall in the level of sucrose; and invertase activity was higher in trehalose-fed shoot tips. The incorporation of label from [14C]glucose into sucrose in the shoot tip explant was reduced as early as 12 h of trehalose feeding. The results suggest that increased utilization of sucrose as well as an inhibition of its synthesis contribute to the drastic fall in the sucrose content upon trehalose feeding.

Toxicity in Cuscuta reflexa Sucrose Content Decreases In Shoot Tips Upon Trehalose Feeding Trehalose

Trehalose, an {alpha},{alpha}-diglucoside, induced a rapid blackening and death of shoot tips of Cuscuta reflexa (dodder) cultured in vitro. The onset of toxic symptom was delayed if any of the several sugars which support the in vitro growth of Cuscuta was supplied with trehalose. The rate of trehalose uptake or its accumulation in the tissue was not affected by sugar cofeeding. The levels of total and reducing sugars declined appreciably in the trehalose-fed shoot tip explants compared to control tissue cultured in absence of a carbon source. This was not due to an increased rate of respiration of the trehalose-treated tissue. In shoot tips cultured in presence of both trehalose and sucrose, the decline in total and reducing sugars was curtailed. There was a marked fall in the level of sucrose; and invertase activity was higher in trehalose-fed shoot tips. The incorporation of label from [14C]glucose into sucrose in the shoot tip explant was reduced as early as 12 h of trehalose feeding. The results suggest that increased utilization of sucrose as well as an inhibition of its synthesis contribute to the drastic fall in the sucrose content upon trehalose feeding

Cytochemical changes in the developmental process of Nostoc sphaeroides (cyanobacterium)

There are several apparent developmental stages in the life cycle of Nostoc sphaeroides Kutzing, an edible cyanobacterium found mainly in paddy fields in central China. The cytochemical changes in developmental stages such as hormogonia, aseriate stage, filamentous stage and colony in N. sphaeroides were examined using fluorescent staining and colorimetric methods. The staining of acidic and sulfated polysaccharides increased with development when hormogonia were used as the starting point. Acidic polysaccharides (AP) were most abundant at the aseriate stage and then decreased, while the sulfated polysaccharides (SP) were highest at the colony stage. Quantitatively, along the developmental process from hormogonia to colony, total carbohydrates first increased, then became stable, and then reached their highest level at the colony stage, while reducing sugars were highest at the hormogonia stage and then decreased sharply once development began. SP were not detectable in the hot water soluble polysaccharides (HWSP), and hormogonia had the lowest content of AP, while old colonies had the highest. The AP content of the aseriate stage, filamentous stage and young colony stage were very similar. The evolutionary relationships reflected in the developmental stages of N. sphaeroides are discussed.

UV-B-induced Oxidative Damage and Protective Role of Exopolysaccharides in Desert Cyanobacterium Microcoleus vaginatus

UV-B-induced oxidative damage and the protective effect of exopolysaccharides (EPS) in Microcoleus vaginatus, a cyanobacterium isolated from desert crust, were investigated. After being irradiated with UV-B radiation, photosynthetic activity (Fv/Fm), cellular total carbohydrates, EPS and sucrose production of irradiated cells decreased, while reducing sugars, reactive oxygen species (ROS) generation, malondialdehyde (MDA) production and DNA strand breaks increased significantly. However, when pretreated with 100 mg/L exogenous EPS, EPS production in the culture medium of UV-B stressed cells decreased significantly; Fv/Fm, cellular total carbohydrates, reducing sugars and sucrose synthase (SS) activity of irradiated cells increased significantly, while ROS generation, MDA production and DNA strand breaks of irradiated cells decreased significantly. The results suggested that EPS exhibited a significant protective effect on DNA strand breaks and lipid peroxidation by effectively eliminating ROS induced by UV-B radiation in M. vaginatus.

Effects of salt stress on carbohydrate metabolism in desert soil alga Microcoleus vaginatus Gom.

The effects of salt stress on carbohydrate metabolism in Microcoleus vaginatus Gom., a cyanobacterium isolated from desert algal crusts, were investigated in the present study. Extracellular total carbohydrates and exopolysaccharides (EPS) in the culture medium produced by M. vaginatus increased significantly during the growth phase and reached a maximum during the stationary phase. The production of extracellular carbohydrates also significantly increased under higher salt concentrations, which was attributed to an increase in low molecular weight carbohydrates. In the presence of NaCl, the production of cellular total carbohydrates decreased and photosynthetic activity was impaired, whereas cellular reducing sugars, water-soluble sugars and sucrose content and sucrose phosphate synthase activity increased, reaching a maximum in the presence of 200 mmol/L NaCl. These parameters were restored to original levels when the algae were transferred to a non-saline medium. Sodium and K+ concentrations of stressed cells decreased significantly and H+-ATPase activity increased after the addition of exogenous sucrose or EPS. The results suggest that EPS and sucrose are synthesized to maintain the cellular osmotic equilibrium between the intra- and extracellular environment, thus protecting algal cells from osmotic damage, which was attributed to the selective exclusion of cellular Na+ and K+ by H+-ATPase.

Acid-catalyzed hydrolysis of cellulose and cellulosic waste using a microwave reactor system

A microwave reactor system was investigated as a potential technique to maximize sugar yield for the hydrolysis of municipal solid waste for ethanol production. Specifically, dilute acid hydrolysis of a-cellulose and waste cellulosic biomass (grass clippings) with phosphoric acid was undertaken within the microwave reactor system. The experimental data and reaction kinetic analysis indicate that the use of a microwave reactor system can successfully facilitate dilute acid hydrolysis of cellulose and waste cellulosic biomass, producing high yields of total sugars in short reaction times. The maximum yield of reducing sugars was obtained at 7.5% (w/v) phosphoric acid and 160 degrees C, corresponding to 60% of the theoretical total sugars, with a reaction time of 5 min. When using a very low acid concentration (0.4% w/v) for the hydrolysis in the microwave reactor, it was found that 10 g of total sugars/100 g dry mass was produced, which is significant considering the low acid concentration. When hydrolyzing grass clippings using the microwave reactor, the optimum conditions were an acid concentration of 2.5% (w/v), 175 degrees C with a 15 min reaction time, giving 18 g/100 g dry mass of total sugars, with xylose being the sugar with the highest yield. It was observed that pentose sugars were more easily formed but also more easily degraded, these being significantly affected by increases in acid concentration and temperature. Kinetic modeling of the data indicated that the use of microwave heating may account for an increase in reaction rate constant, k(1), found in this study in comparison with conventional systems described in the literature.

Extração e caracterização de extratos de Jatropha gossypiifolia L.: avaliação da sua atividade antimicrobiana e antioxidante

Trabalho Final de Mestrado para obtenção do grau de mestre em Engenharia Química e Biológica

Water-soluble precursors of beef flavour I: effect of diet and breed

The effects of diet and breed on the concentration of water-soluble flavour precursors, namely sugars, free amino acids, ribonucleotides, creatinine, carnosine and creatine, were studied in beef longissimus hanborum muscle. Diet had a significant effect on the concentration of free amino acids, with animals fed on grass silage having higher free amino acid levels than animals fed on a concentrate diet, whereas animals fed concentrates had a higher total reducing sugar content. Differences between a beef breed (Aberdeen Angus x Holstein-Friesian) and a dairy breed (Holstein-Friesian) were generally small. (C) 2007 Elsevier Ltd. All rights reserved.

Effects of genotype and environment on free amino acid levels in wheat grain: implications for acrylamide formation during processing

Acrylamide forms from free asparagine and reducing sugars during cooking, with asparagine concentration being the key parameter determining the formation in foods produced from wheat flour. In this study free amino acid concentrations were measured in the grain of varieties Spark and Rialto and four doubled haploid lines from a Spark x Rialto mapping population. The parental and doubled haploid lines had differing levels of total free amino acids and free asparagine in the grain, with one line consistently being lower than either parent for both of these factors. Sulfur deprivation led to huge increases in the concentrations of free asparagine and glutamine, and canonical variate analysis showed clear separation of the grain samples as a result of treatment (environment, E) and genotype (G) and provided evidence of G x E interactions. Low grain sulfur and high free asparagine concentration were closely associated with increased risk of acrylamide formation. G, E, and G x E effects were also evident in grain from six varieties of wheat grown at field locations around the United Kingdom in 2006 and 2007. The data indicate that progress in reducing the risk of acrylamide formation in processed wheat products could be made immediately through the selection and cultivation of low grain asparagme varieties and that further genetically driven improvements should be achievable. However, genotypes that are selected should also be tested under a range of environmental conditions.

Sugars in crop plants

We review current knowledge of the most abundant sugars, sucrose, maltose, glucose and fructose, in the world's major crop plants. The sucrose-accumulating crops, sugar beet and sugar cane, are included, but the main focus of the review is potato and the major cereal crops. The production of sucrose in photosynthesis and the inter-relationships of sucrose, glucose, fructose and other metabolites in primary carbon metabolism are described, as well as the synthesis of starch, fructan and cell wall polysaccharides and the breakdown of starch to produce maltose. The importance of sugars as hormone-like signalling molecules is discussed, including the role of another sugar, trehalose, and the trehalose biosynthetic pathway. The Maillard reaction, which occurs between reducing sugars and amino acids during thermal processing, is described because of its importance for colour and flavour in cooked foods. This reaction also leads to the formation of potentially harmful compounds, such as acrylamide, and is attracting increasing attention as food producers and regulators seek to reduce the levels of acrylamide in cooked food. Genetic and environmental factors affecting sugar concentrations are described.