Ivo Mottin Demiate

Characterization of tropical starches modified with potassium permanganate and lactic acid

In the present work some tropical starches were modified by an oxidative chemical treatment with potassium permanganate and lactic acid. The native and modified samples were evaluated by mid-infrared spectroscopy, differential dyeing, pH, expansion power, solubility and swelling power, clarity of the pastes, susceptibility to syneresis, carboxyl content and reducing power. All modified samples presented dark blue color, higher expansion power (except corn starch), carboxyl content and reducing power. The solubility of the modified starch granules was very high at 90oC. At this temperature, it was not possible to measure their swelling power. The viscographic analysis showed decrease in peak viscosity and higher degree of cooking instability. The principal component analysis of the mid-infrared spectra allowed separation between native and modified samples due to the presence of carboxyl groups. The expansion was inversely related with amylose content of the starches.

Characterization of chestnut (Castanea sativa, mill) starch for industrial utilization

Studies were conducted to characterize the chestnut and its starch. Chemical composition of the chestnuts showed high level of starch. Moisture level in the raw nuts was around 50g/100g in wet basis and starch content, around 80g/100g in dry basis; other nut flour components were protein (5.58 g/100g), lipid (5.39 g/100g), crude fiber (2.34 g/100g) and ash (2.14 g/100g). Starch fraction was chemically characterized in order to identify the granule quality as compared with those of cassava and corn. This fraction showed more lipids and proteins than the other starches. Chestnut starch granules showed peculiar shape, smaller than the control starches and low amount of damaged units. Chemical composition concerning amylose : amylopectin ratio was intermediate to that presented by cassava and corn starch granules. Water absorption at different temperatures as well as solubility were also intermediate but closer to that presented by cassava granules. The same behavior was observed in the interaction with dimethyl-sulfoxide. Native starch granules and those submitted to enzymatic treatment with commercial a-amylase and also with enzymes from germinated wheat were observed by scanning electronic microscopy. Water suspensions of chestnut starch granules were heated to form pastes that were studied comparatively to those obtained with cassava and corn starches. Viscographic pattern of chestnut starch pastes showed a characteristic profile with high initial viscosity but peak absence, high resistance to mechanical stirring under hot conditions and high final viscosity. There was no way to compare it with the paste viscographic profiles obtained with the control starches. Chestnut starch pastes were stable down to pH 4 but unstable at pH 3. The water losses observed in the chestnut starch pastes after freeze-thaw cycles showed more similarity to the pattern observed in corn starch pastes as well as clarity and strength of the gel. In general the results showed that chestnut pastes functional properties are intermediate to those of the cassava and corn starch pastes.

Optimisation of the extraction of phenolic compounds from apples using response surface methodology.

The extraction of phenolic compounds from apples was optimised using response surface methodology (RSM). A Box-Behnken design was conducted to analyse the effects of solvent concentration (methanol or acetone), temperature and time on the extraction of total phenolic content, total flavonoids and antioxidant capacity (FRAP and DPPH). Analysis of the individual phenolics was performed by HPLC in optimal extraction conditions. The optimisation suggested that extraction with 84.5% methanol for 15 min, at 28 °C and extraction with 65% acetone for 20 min, at 10 °C were the best solutions for this combination of variables. RSM was shown to be an adequate approach for modelling the extraction of phenolic compounds from apples. Most of the experiments with acetone solutions extracted more bioactive compounds, and hence they had more antioxidant capacity, however, chlorogenic acid and phloridzin had higher yields (32.4% and 48.4%, respectively) in extraction with methanol.

Características estruturais e físico-químicas de amidos de mandioquinha-salsa (Arracacia xanthorrhiza)

Starch has very important physicochemical properties that depend on its botanical source and structural characteristics. Peruvian carrot starch displays special characteristics, which make it appropriate for industrial application in many processed foods. In this work, starch from two Peruvian carrot varieties, Amarela de Carandai (AC) and Amarela de Senador Amaral (ASA), were isolated and their physicochemical and structural properties were determined. Starch from the ASA variety exhibited granules with a greater average diameter than those from the AC variety and more than double the number of granules with size >20 µm, when compared to the other variety. Starches from both varieties, observed in a Scanning Electron Microscope, showed smooth granule surface with circular and polyhedral shapes for large and small granules, respectively. Molecular size distribution, intrinsic viscosity and degree of cristallinity of starches from both varieties were similar; however, amylose content was higher for the starch from the AC variety. Higher values of viscosity, swelling power and gelatinization temperatures were observed for the starch from the ASA variety, which could be related to the lower amylose content and the higher proportion of large granules exhibited by this starch.

Avaliação da qualidade de amostras comerciais de doce de leite pastoso - composição química

Doce de leite is a regional food produced mainly in Argentina and Brazil, presenting some problems related with quality. The present paper aims to determine the chemical composition of commercial samples (n = 42) in order to search for some irregularities. The compounds present in milk (lactose, protein, lipids and ash) were determined as well as starch. The starch content was enzymatically determined and the results showed high levels of polyssacharide. On 15 samples levels higher than 3.0% of starch were found, with 7.8% as a maximum. Moisture levels higher than that allowed by Brazilian legislation [2] were detected on ten samples, with a maximum of 37.2%. The statistical analysis of the chemical composition showed that there was a positive correlation between milk compounds (lactose, protein, lipids and ash) present in the samples and that these compounds were negatively correlated with starch, showing that in some cases starch is added for reducing costs, which can be characterized as a fraud. The principal component analysis evidenced sample differentiation due to their milk compounds, starch and sucrose contents.

Avaliação da influência de amido e carragena nas características físico-químicas e sensoriais de presunto cozido de peru

The use of carrageenan in ham is facultative, but the addition of starch is not allowed by the Brazilian legislation in this kind of product. In this work, a 22 experimental design was used, with duplicates of the central point, considering starch (0 to 2%) and carrageenan levels (0 to 1%) in the production of turkey ham. In both cases, starch and carrageenan showed negative effects on the purge loss and on the reheating loss, indicating that the presence of the hydrocolloids favored the retention of water in the product. However, there were no significant differences in pH, chemical composition, shear values and in the sensory evaluation. A synergistic effect between the polysaccharides was noted. Samples made with 1% carrageenan presented the formation of a gelatinous exudate, but the samples that had 1% carrageenan and 2% starch, did not exhibit this effect. The inclusion of starch to the turkey ham with added carrageenan reduced this undesirable effect. The utilization of starch in ham improved some physicochemical characteristics, reduced defects and there were no sensory differences when the turkey ham with added starch was compared to the Brazilian standard without starch.

Thermal behavior of corn starch granules modified by acid treatment at 30 and 50°C

Unprocessed native starches are structurally too weak and functionally too restricted for application in todays advanced food technologies. Processing is necessary to engender a range of functionality. Naturals or natives starches can be modified by using several methods physical, chemical, enzymatic or combined, according industrial purposes. In this work, native corn starch was hydrolyzed by hydrochloric acid solution and investigated by using thermoanalytical techniques (thermogravimetry - TG, differential thermal analysis - DTA and differential scanning calorimetry - DSC), as well as optical microscopy and X-ray diffractometry. After acid treatment at 30 and 50°C, a decrease of gelatinization enthalpy (ΔHgel) was verified. Optical microscopy and X-ray diffractometry allowed us to verify the granules contorn and rugosity typical of cereal starches.

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.

Thermal characterization of partially hydrolyzed cassava (Manihot esculenta) starch granules

Cassava starch, partially hydrolyzed by fungal a-amylase, was characterized using thermal analysis, light microscopy and X-ray diffraction. Thermal degradation was initiated at lower degradation temperatures after enzymatic treatment and the DSC (Differential scanning calorimetry) analysis showed almost similar range of gelatinization temperature, but the enthalpies of gelatinization were quite increased for the partially hydrolyzed starch granules. The results suggested that the partial degradation of the starch granules was concentrated in the amorphous regions.

Características físico-químicas de amidos modificados com permanganato de potássio/ácido lático e hipoclorito de sódio/ácido lático

Oxidized starches produce low-viscosity pastes even in high concentrations, are stable to retrogradation and are used in the paper, textile and food industries. This property is attributed to the presence of carboxyl groups, which have negative charges and are bulkier than hydroxyls. In this work, potato, sweet potato, Peruvian carrot, cassava, corn and waxy corn starches were modified with oxidative reagents and characterized with respect to their carboxyl content, reducing power, differential dyeing, expansion power and viscographic properties, in water, acetate buffer (pH 4.0) and phosphate buffer (pH 7.0). The results showed that waxy corn and cassava starches presented high expansions, when modified with KMNO4/lactic acid (25.8 and 24.1 mL.g-1, respectively). The starch pastes of waxy corn showed freeze-thaw stability in all treatments. Differential dyeing and carboxyl content did not vary between the native and modified samples; only potato starch reacted with methylene blue, due to the presence of phosphate groups. With respect to pH and acidity, almost all samples presented values next to neutrality, except corn and waxy corn starch modified with NaOCl/lactic acid. The starches oxidized with KMnO4/lactic acid presented lower viscosity peaks than those oxidized with NaOCl. The viscosity peaks of starches analyzed in phosphate buffer were lower than in water and acetate buffer.