Resistant starch in cassava products

Found in different foods, starch is the most important source of carbohydrates in the diet. Some factors present in starchy foods influence the rate at which the starch is hydrolyzed and absorbed in vivo. Due the importance of cassava products in Brazilian diet, the objective of this study was to analyze total starch, resistant starch, and digestible starch contents in commercial cassava products. Thirty three commercial cassava products from different brands, classifications, and origin were analyzed. The method used for determination of resistant starch consisted of an enzymatic process to calculate the final content of resistant starch considering the concentration of glucose released and analyzed. The results showed significant differences between the products. Among the flours and seasoned flours analyzed, the highest levels of resistant starch were observed in the flour from Bahia state (2.21%) and the seasoned flour from Paraná state (1.93%). Starch, tapioca, and sago showed levels of resistant starch ranging from 0.56 to 1.1%. The cassava products analyzed can be considered good sources of resistant starch; which make them beneficial products to the gastrointestinal tract.

Modificação enzimática da farinha de arroz visando a produção de amido resistente

The aim of this work was to study the enzymatic modification on rice flour using lipase pancreatic and amyloglucosidase to obtain resistant starch. For this, Response Surface Methodology (RSM) was used to determine the best operating conditions for each enzyme. For lypase pancreatic, the highest value for resistant starch (45%) was achieved within 2 h reaction at pH 7 using an enzyme/substrate ratio of 4% (w/w) and Dp= 100/200 tyler. For amyloglucosidase, optima conditions corresponded to an enzyme/substrate ratio of 0,006 mL/g and Dp= 100/200 tyler at 45 ºC, yielding 57% of resistant starch in 2 h reaction. These results show the potential of using both enzymes to modified rice flour, increasing the resistant starch in about 5.7 folds in relation to the flour without treatment (resistant starch=10.6%).

Nutritional potential of green banana flour obtained by drying in spouted bed

This study evaluated the chemical composition of peeled and unpeeled green banana Cavendish (AAA) flour obtained by drying in spouted bed, aiming at adding nutritional value to food products. The bananas were sliced and crushed to obtain a paste and fed to the spouted bed dryer (12 cm height and T = 80 ºC) in order to obtain flour. The flours obtained were subjected to analysis of moisture, protein, ash, carbohydrates, total starch, resistant starch, fiber. The green banana flours, mainly unpeeled, are good sources of fiber and resistant starch with an average of 21.91g/100g and 68.02g/100g respectively. The protein content was found in an average of 4.76g/100g, being classified as a low biological value protein with lysine as the first limiting amino acid. The results showed that unpeeled green banana flour obtained by spouted bed drying can be a valuable tool to add nutritional value to products in order to increase their non-digestible fraction.

Cultivar, harvest year, and storage conditions affecting nutritional quality of common beans (Phaseolus vulgaris L.

Sixteen common bean cultivars were compared concerning the physicochemical characteristics of their raw seeds in the course of two consecutive harvests, as well as the effect of storage conditions on starch and dietary fiber content of cooked beans. Using cluster analysis it was possible to identify groups of cultivars with different nutritional features. Bean cultivars were categorized into four different groups according either to their macronutrient content (crude protein-PROT, total dietary fiber-TDF, insoluble dietary fiber-IDF, soluble dietary fiber-SDF, digestible starch-DS, and resistant starch-RS) or to their micronutrient levels (Fe, Zn, Mn, Cu, Ca, Mg, and P). Guateian 6662 and Rio Tibagi appeared to be the most suitable cultivars to prevent nutritional deficiencies, because they had high PROT, DS, Fe, and Zn content. The high total dietary fiber and RS content of Iraí, Minuano, and TPS Bonito cultivars, and specially the high soluble fiber content of Guateian 6662 and Rio Tibagi cultivars suggests that they could have a beneficial role in controlling blood lipid and glucose levels. Cooked beans had a decrease in DS and an increase in RS content after storage (4 °C or -20 °C), but these changes were more prominent in beans that had low RS content before cooking than in those of high RS content. TDF, IDF, and SDF did not change after storage.

Influence of heat treatment on the sensory and physical characteristics and carbohydrate fractions of french-fried potatoes (Solanum tuberosum L.)

AbstractThe aim of this study was to analyze the impact that heat treatment with salts and freezing processes on the sensory, instrumental, and physico-chemical characteristics of fried potatoes of the Monalisa cultivar. The potatoes were blanched in distilled water (P); sodium chloride solution (B1); calcium chloride solution (B2), and a solution with both of these salts (B3). They were then pre-cooked and frozen for 24 hours and for 30 days. After frying, sensory characteristics were analyzed (color, texture, flavor, oiliness), along with overall preference and instrumental determinations of texture, color, and oil content. Further tests were conducted on the sample with the best results in the sensory analysis (B1), along with sample P as a control, to determine granule microstructure, carbohydrate fractions, glycemic index, and glycemic load. Blanching B3, despite reducing oil absorption and providing less oiliness, obtained lesser overall preference. Freezing for 30 days increased the lightness, except for when sodium chloride was used, which intensified the color yellow. The use of sodium chloride did not interfere with the type of starch granules, nor with the formation of resistant starch; however, longer freezing time reduced the glycemic index and concentrated the dietary fiber content. All samples exhibited low glycemic index and moderate glycemic loads.

The schistosome enzyme that activates oxamniquine has the characteristics of a sulfotransferase

Available evidence suggests that the antischistosomal drug oxamniquine is converted to a reactive ester by a schistosome enzyme that is missing in drug-resistant parasites. This study presents data supporting the idea that the active ester is a sulfate and the activating enzyme is a sulfotransferase. Evidence comes from the fact that the parasite extract loses its activating capability upon dialysis, implying the requirement of some dialyzable cofactor. The addition of the sulfate donor 3'-phosphoadenosine 5'-phosphosulfate (PAPS) restored activity of the dialyzate, a strong indication that a sulfotransferase is probably involved. Classical sulfotransferase substrates like beta-estradiol and quercetin competitively inhibited the activation of oxamniquine. Furthermore, these substrates could be sulfonated in vitro using an extract of sensitive (but not resistant) schistosomes. Gel filtration analysis showed that the activating factor eluted in a fraction corresponding to a molecular mass of about 32 kDa, which is the average size of typical sulfotransferase subunits. Ion exchange and affinity chromatography confirmed the sulfotransferase nature of the enzyme. Putative sulfotransferases present in schistosome databases are being examined for their possible role as oxamniquine activators.

Megazol and its bioisostere 4H-1,2,4-triazole: comparing the trypanocidal, cytotoxic and genotoxic activities and their in vitro and in silico interactions with the Trypanosoma brucei nitroreductase enzyme

Megazol (7) is a 5-nitroimidazole that is highly active against Trypanosoma cruzi and Trypanosoma brucei, as well as drug-resistant forms of trypanosomiasis. Compound 7 is not used clinically due to its mutagenic and genotoxic properties, but has been largely used as a lead compound. Here, we compared the activity of 7 with its 4H-1,2,4-triazole bioisostere (8) in bloodstream forms of T. brucei and T. cruzi and evaluated their activation by T. brucei type I nitroreductase (TbNTR) enzyme. We also analysed the cytotoxic and genotoxic effects of these compounds in whole human blood using Comet and fluorescein diacetate/ethidium bromide assays. Although the only difference between 7 and 8 is the substitution of sulphur (in the thiadiazole in 7) for nitrogen (in the triazole in 8), the results indicated that 8 had poorer antiparasitic activity than 7 and was not genotoxic, whereas 7 presented this effect. The determination of Vmax indicated that although 8 was metabolised more rapidly than 7, it bounds to the TbNTR with better affinity, resulting in equivalent kcat/KM values. Docking assays of 7 and 8 performed within the active site of a homology model of the TbNTR indicating that 8 had greater affinity than 7.

Novel point mutations in the ERG11 gene in clinical isolates of azole resistant Candida species

The azoles are the class of medications most commonly used to fight infections caused by Candida sp. Typically, resistance can be attributed to mutations in ERG11 gene (CYP51) which encodes the cytochrome P450 14α-demethylase, the primary target for the activity of azoles. The objective of this study was to identify mutations in the coding region of theERG11 gene in clinical isolates of Candidaspecies known to be resistant to azoles. We identified three new synonymous mutations in the ERG11 gene in the isolates of Candida glabrata (C108G, C423T and A1581G) and two new nonsynonymous mutations in the isolates of Candida krusei - A497C (Y166S) and G1570A (G524R). The functional consequence of these nonsynonymous mutations was predicted using evolutionary conservation scores. The G524R mutation did not have effect on 14α-demethylase functionality, while the Y166S mutation was found to affect the enzyme. This observation suggests a possible link between the mutation and dose-dependent sensitivity to voriconazole in the clinical isolate of C. krusei. Although the presence of the Y166S in phenotype of reduced azole sensitivity observed in isolate C. kruseidemands investigation, it might contribute to the search of new therapeutic agents against resistant Candida isolates.

Acetolactate synthase activity in Euphorbia heterophylla resistant to ALS- and protox- inhibiting herbicides

The objective of this study was to determine the activity of the enzyme acetolactate synthase in biotypes of wild poinsettia (Euphorbia heterophylla) with multiple resistance to ALS- and Protox- inhibitors in the presence and absence of imazapyr, imazethapyr and nicosulfuron. We conducted in vitro assay of ALS enzyme extracted from plants of Vitorino, Bom Sucesso do Sul and Medianeira biotypes (with multiple resistance) and a susceptible population in the absence and presence of imazapyr, imazethapyr and nicosulfuron. In the absence of herbicides, biotypes with multiple resistance showed higher affinity for the substrate of the enzyme compared with the susceptible population. The herbicides imazapyr, imazethapyr and nicosulfuron had little effect on the enzyme activity of ALS-resistant biotypes and, conversely, high inhibitory effect on ALS of the susceptible population. Resistance factors were very high, greater than 438, 963 and 474 for Vitorino, Bom Sucesso do Sul and Medianeira biotypes, respectively. The resistance to ALS inhibitors is due to the insensitivity of ALS to herbicides of both imidazolinone and sulfonylurea groups, characterizing a cross-resistance.

Specific fluorogenic substrates for neprilysin (neutral endopeptidase, EC 3.4.24.11) which are highly resistant to serine- and metalloproteases

Two intramolecularly quenched fluorogenic peptides containing o-aminobenzoyl (Abz) and ethylenediamine 2,4-dinitrophenyl (EDDnp) groups at amino- and carboxyl-terminal amino acid residues, Abz-DArg-Arg-Leu-EDDnp (Abz-DRRL-EDDnp) and Abz-DArg-Arg-Phe-EDDnp (Abz-DRRF-EDDnp), were selectively hydrolyzed by neutral endopeptidase (NEP, enkephalinase, neprilysin, EC 3.4.24.11) at the Arg-Leu and Arg-Phe bonds, respectively. The kinetic parameters for the NEP-catalyzed hydrolysis of Abz-DRRL-EDDnp and Abz-DRRF-EDDnp were Km = 2.8 µM, kcat = 5.3 min-1, kcat/Km = 2 min-1 µM-1 and Km = 5.0 µM, kcat = 7.0 min-1, kcat/Km = 1.4 min-1 µM-1, respectively. The high specificity of these substrates was demonstrated by their resistance to hydrolysis by metalloproteases [thermolysin (EC 3.4.24.2), angiotensin-converting enzyme (ACE; EC 3.4.24.15)], serineproteases [trypsin (EC 3.4.21.4), a-chymotrypsin (EC 3.4.21.1)] and proteases present in tissue homogenates from kidney, lung, brain and testis. The blocked amino- and carboxyl-terminal amino acids protected these substrates against the action of aminopeptidases, carboxypeptidases and ACE. Furthermore, DR amino acids ensured total protection of Abz-DRRL-EDDnp and Abz-DRRF-EDDnp against the action of thermolysin and trypsin. Leu-EDDnp and Phe-EDDnp were resistant to hydrolysis by a-chymotrypsin. The high specifity of these substrates suggests their use for specific NEP assays in crude enzyme preparations

Analysis of renin-angiotensin-aldosterone system gene polymorphisms in resistant hypertension

Essential hypertension is a disease multifactorially triggered by genetic and environmental factors. The contribution of genetic polymorphisms of the renin-angiotensin-aldosterone system and clinical risk factors to the development of resistant hypertension was evaluated in 90 hypertensive patients and in 115 normotensive controls living in Southwestern Brazil. Genotyping for insertion/deletion of angiotensin-converting enzyme, angiotensinogen M235T, angiotensin II type 1 receptor A1166C, aldosterone synthase C344T, and mineralocorticoid receptor A4582C polymorphisms was performed by PCR, with further restriction analysis when required. The influence of genetic polymorphisms on blood pressure variation was assessed by analysis of the odds ratio, while clinical risk factors were evaluated by logistic regression. Our analysis indicated that individuals who carry alleles 235-T, 1166-A, 344-T, or 4582-C had a significant risk of developing resistant hypertension (P < 0.05). Surprisingly, when we tested individuals who carried the presumed risk genotypes A1166C, C344T, and A4582C we found that these genotypes were not associated with resistant hypertension. However, a gradual increase in the risk to develop resistant hypertension was detected when the 235-MT and TT genotypes were combined with one, two or three of the supposedly more vulnerable genotypes - A1166C (AC/AA), C344T (TC/TT) and A4582C (AC/CC). Analysis of clinical parameters indicated that age, body mass index and gender contribute to blood pressure increase (P < 0.05). These results suggest that unfavorable genetic renin-angiotensin-aldosterone system patterns and clinical risk variables may contribute to increasing the risk for the development of resistant hypertension in a sample of the Brazilian population.

ENZYMATIC DETERMINATION OF STARCH IN DOCE DE LEITE USING DIALYSIS

The importance of starch for the food industry makes it necessary to develop new, fast, economic and accurate methodologies for its quantification. In the present paper starch hydrolysis using commercial enzymes of industrial grade are studied aiming to develop an easy and cheap analysis, available to a greater number of industries and technicians. The proposed method is simple, divided in a first step where soluble sugars are eliminated from the samples by using dialysis, followed by starch hydrolysis of the retained fraction with a thermoresistent bacterial alfa-amylase (Termamyl 120L®) and an amyloglucosidase (AMG 300L®). The hydrolysis conditions were those suggested by the enzyme producer. After the hydrolysis step the material was dialysed again for the extraction of glucose that was quantified by the glucose-oxidase colorimetric reactant. The results allowed the construction of calibration equations for starch determination on the analyzed samples. These samples were produced on a laboratory scale and native and acid-modified corn starches were added in known concentrations. By considering the final dilutions employed for glucose determination on the samples, it was possible to confirm that they were identical to that of the glucose-oxidase reactant calibration.

Effect of enzymatic hydrolysis on some physicochemical properties of root and tuber granular starches

Enzymatic hydrolysis of granular starch is an important tool to provide information about granule structure. Cassava, sweet potato, Peruvian carrot, and potato starches were hydrolyzed by bacterial α-amylase at 37 °C for 48 hours, and the physicochemical properties of the residues from hydrolysis were determined. Cassava starch was the most susceptible to enzyme displaying 20.9% of hydrolysis, whereas potato starch was the most resistant with 5.9%. The granule average size varied from 10.8 to 23.4 μm for Peruvian carrot and potato starches, respectively. With the use of SEM, a smooth granule surface was observed for all native starches. Cassava and sweet potato starches displayed an A-type X-ray diffraction pattern, while Peruvian carrot and potato starches showed a B-type pattern. After hydrolysis, cassava, sweet potato, and Peruvian carrot starches showed some well degraded granules, whereas potato starch presented a slight sign of degradation. The amylose content of the starches decreased with hydrolysis for cassava, sweet potato, and Peruvian carrot starches and was kept unchanged for the potato starch. As expected, intrinsic viscosity and pasting properties decreased for all hydrolyzed starches. There is no difference between thermal properties of native and hydrolyzed starches. These results suggested that hydrolysis occurred in amorphous and crystalline areas of the granules. The B type diffraction pattern in conjunction with the big granule size of the potato starch may have contributed to the greatest resistance of this starch to hydrolysis.

Cassava starch in the Brazilian food industry

Cassava starch is a valued raw material for producing many kinds of modified starches for food applications. Its physicochemical properties, as well as its availability, have made it an interesting and challenging ingredient for the food industry. In the present work, food grade modified cassava starches were purchased from producers and analyzed for selected physicochemical characteristics. Samples of sour cassava starch were included, as well as one sample of native cassava starch. Results showed that almost all modified starches were resistant to syneresis, produced pastes more stable to stirred cooking, and some of them were difficult to cook. The sour cassava starches presented high acidity and resulted in clear and unstable pastes during stirred cooking, susceptible to syneresis.

Sugarcane starch: quantitative determination and characterization

Starch is found in sugarcane as a storage polysaccharide. Starch concentrations vary widely depending on the country, variety, developmental stage, and growth conditions. The purpose of this study was to determine the starch content in different varieties of sugarcane, between May and November 2007, and some characteristics of sugarcane starch such as structure and granules size; gelatinization temperature; starch solution filterability; and susceptibility to glucoamylase, pullulanase, and commercial bacterial and fungal α-amylase enzymes. Susceptibility to debranching amylolytic isoamylase enzyme from Flavobacterium sp. was also tested. Sugarcane starch had spherical shape with a diameter of 1-3 µm. Sugarcane starch formed complexes with iodine, which showed greater absorption in the range of 540 to 620 nm. Sugarcane starch showed higher susceptibility to glucoamylase compared to that of waxy maize, cassava, and potato starch. Sugarcane starch also showed susceptibility to debranching amylolytic pullulanases similar to that of waxy rice starch. It also showed susceptibility to α-amylase from Bacillus subtilis, Bacillus licheniformis, and Aspergillus oryzae similar to that of the other tested starches producing glucose, maltose, maltotriose, maltotetraose, maltopentose and limit α- dextrin.