Débora de Queiroz Tavares

The structure of waxy corn starch: Effect of granule size

The granules of waxy corn starch were isolated and various samples were separated by size and classified according to their average diameter in: non-separated granules (N), granules with diamcter < 15 μm (S) and granules with diameter ≥ 15 μm (L). The samples were hydrolyzed by bacterial α-amylase and fungal amyloglucosidase. The starch granules remaining after enzymatic hydrolysis were analysed by X-ray diffraction and optical and scanning electron microscopy. Sephadex G-50 gel permeation chromatography of the dissolved residues from the hydrolysis of the N and S samples was performed directly and after successive enzymatic digestion with pullulanase and β-amylase. The results showed that the percentage of hydrolysis increased with a decrease in diameter. No apparent differences in waxy corn starch when observed under light and scanning electronic microscope were observed, regardless of diameter and enzyme action, although both large and small granules showed extensive surface corrosion after enzymatic attack. X-ray analysis suggested a decrease in the quantity of crystalline areas in the smaller granules, which would explain the high percentage of hydrolysis evidenced by these granules. The elution patterns of the α-glucans of both starches (N and S) were similar and reveled the presence of two fractions which were not susceptible to α-amylase and amyloglucosidase attack suggesting that these fractions were involved in the waxy corn starch crystalline regions. Debranching with pullulanase followed by gel-permeation chromatography showed that the amylopectins from the starch granules studied contained three groups of unit chains instead of the two reported in the literature.

Structural and Physicochemical Characteristics of Lintnerized Native and Sour Cassava Starches

Univ Estadual Paulista, Dept Engn & Tecnol Alimentos, BR-15054000 Sao Jose do Rio Preto, SP, Brazil

A high-fructose diet induces insulin resistance but not blood pressure changes in normotensive rats

Rats fed a high-fructose diet represent an animal model for insulin resistance and hypertension. We recently showed that a high-fructose diet containing vegetable oil but a normal sodium/potassium ratio induced mild insulin resistance with decreased insulin receptor substrate-1 tyrosine phosphorylation in the liver and muscle of normal rats. In the present study, we examined the mean blood pressure, serum lipid levels and insulin sensitivity by estimating in vivo insulin activity using the 15-min intravenous insulin tolerance test (ITT, 0.5 ml of 6 microg insulin, iv) followed by calculation of the rate constant for plasma glucose disappearance (Kitt) in male Wistar-Hannover rats (110-130 g) randomly divided into four diet groups: control, 1:3 sodium/potassium ratio (R Na:K) diet (C 1:3 R Na:K); control, 1:1 sodium/potassium ratio diet (CNa 1:1 R Na:K); high-fructose, 1:3 sodium/potassium ratio diet (F 1:3 R Na:K), and high-fructose, 1:1 sodium/potassium ratio diet (FNa 1:1 R Na:K) for 28 days. The change in R Na:K for the control and high-fructose diets had no effect on insulin sensitivity measured by ITT. In contrast, the 1:1 R Na:K increased blood pressure in rats receiving the control and high-fructose diets from 117 +/- 3 and 118 +/- 3 mmHg to 141 +/- 4 and 132 +/- 4 mmHg (P < 0.05), respectively. Triacylglycerol levels were higher in both groups treated with a high-fructose diet when compared to controls (C 1:3 R Na:K: 1.2 +/- 0.1 mmol/l vs F 1:3 R Na:K: 2.3 +/- 0.4 mmol/l and CNa 1:1 R Na:K: 1.2 +/- 0.2 mmol/l vs FNa 1:1 R Na:K: 2.6 +/- 0.4 mmol/l, P < 0.05). These data suggest that fructose alone does not induce hyperinsulinemia or hypertension in rats fed a normal R Na:K diet, whereas an elevation of sodium in the diet may contribute to the elevated blood pressure in this animal model.

A high-fructose diet induces changes in pp185 phosphorylation in muscle and liver of rats

Insulin stimulates the tyrosine kinase activity of its receptor resulting in the tyrosine phosphorylation of pp185, which contains insulin receptor substrates IRS-1 and IRS-2. These early steps in insulin action are essential for the metabolic effects of insulin. Feeding animals a high-fructose diet results in insulin resistance. However, the exact molecular mechanism underlying this effect is unknown. In the present study, we determined the levels and phosphorylation status of the insulin receptor and pp185 (IRS-(1/2)) in liver and muscle of rats submitted to a high-fructose diet evaluated by immunoblotting with specific antibodies. Feeding fructose (28 days) induced a discrete insulin resistance, as demonstrated by the insulin tolerance test. Plasma glucose and serum insulin and cholesterol levels of the two groups of rats, fructose-fed and control, were similar, whereas plasma triacylglycerol concentration was significantly increased in the rats submitted to the fructose diet (P<0.05). There were no changes in insulin receptor concentration in the liver or muscle of either group. However, insulin-stimulated receptor autophosphorylation was reduced to 72 +/- 4% (P<0.05) in the liver of high-fructose rats. The IRS-1 protein levels were similar in both liver and muscle of the two groups of rats. In contrast, there was a significant decrease in insulin-induced pp185 (IRS-(1/2)) phosphorylation, to 83 +/- 5% (P<0.05) in liver and to 77 +/- 4% (P<0.05) in muscle of the high-fructose rats. These data suggest that changes in the early steps of insulin signal transduction may have an important role in the insulin resistance induced by high-fructose feeding.

Behavior of plant tissue in osmotic solutions

The effect of the concentration of sucrose solutions on the cellular structure of potato tissue in equilibrium at 27 °C was studied. Two different methods of investigation were used to determine the volume of the different phases composing the cellular tissue of the potato when in equilibrium with the solutions, one based on data of the concentration itself and the overall volume of 2 mm slices after 48 h at equilibrium, and the other on microscopic images of cells in thin slices of fresh tissue stained with neutral red after an hour in equilibrium to show protoplasts, vacuoles and plasmolysis spaces. The results of these methods were compared with those obtained by a predictive thermodynamic approach considering the semipermeability of cell membranes. Phase volume data obtained from microscopic analysis were more similar to what was predicted by the theoretical model than those obtained by means of composition measurement, where the long equilibrium time apparently led to the loss of semipermeability of the cell membranes, since total volumes calculated without consideration of the cell membranes were similar to those measured. This suggests that the length of time of osmotic dehydration brings about a change in cell structure and the consequent involvement of a different mechanism in mass transfer.

Microencapsulação de óleo essencial de laranja

It was done microencapsulation of natural essencial orange oil through spray-drying. The purpose was to use the best proportion of wall materials among maltodextrin, acacia gum, and modified starch (capsul) in order to retain greater amount of orange oil. The orange oil (10%) and maltodextrin (36%) remained constant. Three spray drying temperatures were employed: 180°C, 200°C and 220°C, therefore, nine final products were obtained. The superficial and inner oil concentrations were measured. The microcapsules were also examined through optical and scanning electron microscopy. The three temperatures employed did not affect the microencapsulation. The microstructure of the capsules were almost similar regardless the proportion employed among the carbohydrates to wall composition. At light microscopy it was observed a great heterogeneity of capsules diameters, and probably not smooth surfaces; at scanning electron microscopy it was clear that the walls displayed porosity over round surfaces. The best retention was given by the formula containing 10% of capsul, 10% of orange oil and 36% of maltodextrin, when total oil retention was 94%, regardless the drying temperature here employed.

OCORRÊNCIA E CARACTERIZAÇÃO DO AMIDO RESISTENTE EM AMIDOS DE MILHO E DE BANANA

In this work the occurrence of resistant starch (RS) in normal corn and banana (naturally resistant) starches was studied and also the effects of conditioning moisture, storage temperature and time on the formation of RS in normal corn starch. The physico-chemical characteristics of the RS from corn and banana were also studied, including the molecular structure. The proximate composition data showed that the percentage of RS is not related to the chemical composition of the granule. Banana starch showed granules with a certain polyformism, and a B x-ray diffraction pattern. The dextrins from this starch showed a linear fraction with DP 34 resistant to sequential action of b-amylase and/or pulullonase. The pasting characteristics indicated that the high RS content observed in this starch, could not be explained by the physical structure which maintains the granule. The normal corn starch showed polyhedral shapes. Exclusion gel chromatography of the residues obtained after b- amylase and/or pulullonase hydrolysis, did not show a fraction with DP 34, although the pasting properties indicated a higher granule cohesivity than that of the banana starch. The hydrothermal treatment almost triplicated the RS content (7.15%) of the corn starch, because of the formation of more cohesive structures inside the granule. The retrograded corn starch, with 7.15% RS, was constituted of porous fragments and a C type diffraction pattern. On the other hand, the non significance of storage time on the formation of RS in conjunction with the absence of a fraction with DP 34, suggested the participation of amylose in this resistant structure.

Survey on ochratoxin A in Brazilian green coffee destined for exports

A presenca de ocratoxina A (OTA) em cafe, detectada nos ultimos anos, tem levado alguns paises a estabelecer limites regulatorios. Embora o cafe nao seja uma fonte importante de OTA no consumo humano, a Uniao Europeia podera estabelecer limites, causando impacto economico em paises produtores desses graos. O presente estudo analisou OTA utilizando CLAE em 37 amostras de cafe verde brasileiro destinado exclusivamente a exportacao e verificou a possivel relacao entre graos defeituosos e concentracao de OTA. Os resultados mostraram que a concentracao de OTA esteve entre < 0,16ng/g (limite de deteccao) e 6,24ng/g (media 3,2ng/g). Das cinco amostras avaliadas quanto a relacao defeitos X OTA, o nivel da toxina esteve entre 0,22 e 0,80ng/g (media 0,46ng/g) entre graos sadios e 0,42 e 17,46ng/g (media 4,52ng/g) entre graos defeituosos. Diferencas morfologicas entre graos sadios e defeituosos observados em Microscopia Otica nao demonstraram susceptibilidade a invasao fungica entre os defeituosos. Entre os 15 graos observados em Microscopia Eletronica de Varredura (MEV), apenas um (preto) revelou presenca de fungos e esporos. Os resultados desta investigacao apontam que o cafe verde brasileiro destinado a exportacao encontra-se dentro dos limites para OTA ja estabelecidos.

Polyphenolic cells and their interrelation with cotyledon cells in seven species of Theobroma (Sterculiaceae)

The amount of cotyledon polyphenolic cells varies extensively within the Theobroma species. The polyphenolic compounds of these cells play a protective role and furthermore have an important function in the development of chocolate flavour. The morphology of the polyphenolic cells of the mesophyll is described and the development of these idioblasts in Theobroma cacao L., T. subincanum Mart., T. obovatum Klotzsch ex Bernoulli, T. grandiflorum (Willd. ex Spreng.) K. Schum., T. microcarpum Mart., T. bicolor Bonpl. and T. speciosum Willd. ex Spreng analysed. The total polyphenolic content in the seeds as determined by spectrophotometry showed a variation of about forty times. The alive, transparent polyphenolic cells are scattered throughout the cotiledonary mesophyll. However the polyphenolic cells of T. cacao and T. grandiflorum are also aligned perpendicularly with respect to the mesophyll borders and, in addition, both species display polyphenolic cells with a natural translucent purple colour. All the species analysed contained polyphenolic cells scattered throughout the parenchymal cells and also in a lengthwise association with vascular bundles. In T. bicolor and T. speciosum, the species with the lowest polyphenolic contents, these cells were mostly located around the vascular bundles. Using Scanning Electron Microscopy, the polyphenolic cells demonstrated a complex cytoarchitecture, and after fixing with glutaraldhyde, the polyphenolic secretion was shown to remain as a single unit or was organized into round droplets. Transmission Electron Microscopy displayed immature plastids from young mesophyll cells containing eletron-dense deposits similar to phenolic substances, suggesting that Theobroma plastids are involved in the synthesis of phenolics.

Ensaio tecnológico e sensorial de soja [Glycine max (L.) Merrill] enlatada em estádios verdes e no estádio da maturação de colheita

It was investigated the consumption possibility of the soybean cultivar IAC PL-1 canned as green grain and its best harvest time for canning. Five harvests were processed from the 48th day after flowering (DAF) until extinction of the green coloration. The canning procedure started by pod bleaching, dehulling and canning. To the five lots obtained, a sixth lot was added to study the effect of storage. To qualify the six lots of canned grains, measures of weight, color, texture were done, as well as characteristics of canning liquid. Studies of the sensorial properties of canned grains to dimensionate both acceptance and aspect was performed. Canning was optimized to 121oC with sterilization time around four minutes. Grains physiological maturity took place between 61st to 64th DAF. The heat process conserved the green color of canned grains and did not induce significant loss of the mass of grains; the firm texture of grains increased with maturation. The tasters showed good acceptance of the products and there was no preference concerning the maturation stages. The work concluded that green grains of soybean IAC PL-1 provide canned products with very good technical and taste characteristics. It was found that grains harvested at the conventional maturation point stored and canned obtained good taste acceptance, following that the cultivar IAC PL-1 is also suitable to consumption canned after storage.