Luís Fernando Polesi

Structural and physicochemical characteristics of starch from sugar cane and sweet sorghum stalks.

The starch present in sugar cane and sorghum juice has been considered a problem to the sugar industry. The objective of this work was to study the structural and physicochemical characteristics of the starch present in sugar cane and sweet sorghum. Sugar cane and sweet sorghum starches presented small granules (maximum 5.9 and 7.9 μm), A-type diffraction pattern, high degree of relative crystallinity (44.4 and 42.0%), and low amylose content (17.5 and 16.4%), respectively. Sugar cane starch presented more uniformity in granule shape and size, more homogeneity in amylose chain length, higher number of long lateral chains of amylopectin, and higher susceptibility to enzymatic digestion. Besides being in higher amount in the juice, sweet sorghum starch presented lower values for thermal properties of gelatinization, as well as higher swelling factor, which can cause more problems during processing. Additional studies are needed to evaluate the variety and maturity influence on these properties.

Composition and characterization of pea and chickpea starches

Non conventional starch sources have been intensively studied in recent years, searching for new properties and uses as food ingredients. The objective of this study was to evaluate the physicochemical, structural and functional characteristics of starches from two legumes: green pea (cultivar Utrillo) and chickpea (cultivar BRS Cícero). The pea starch showed high amylose (61%) and resistant starch (RS) (39.8%) contents, with 14.3% of total dietary fibre (TDF). The pea starch presented simple and composite granules with various shapes and sizes, a wide distribution in the amylose elution profile in gel permeation chromatography, B-type crystallinity pattern, gelatinization peak temperature of 74.8 °C, reduced granule swelling with increasing temperature and did not generate high viscosity in the Rapid Visco Analyzer (RVA). The chickpea starch showed large oval shaped granules and small spherical shaped ones, all with a smooth surface, C-type crystallinity pattern, gelatinization peak temperature of 64.6 °C, good granule swelling and high viscosity in the RVA. With respect to composition, the amylose content was 29.2%, the RS 31.9% and TDF 2.7%. These starches could be used in different food applications. From the nutritional point of view, pea starch is interesting due to its considerable resistant starch and total dietary fibre contents. From the technological point of view, chickpea starch is interesting for use in foods requiring hot viscosity.

Physicochemical and structural characteristics of rice starch modified by irradiation.

This work evaluated the physicochemical and structural properties of rice starch of the cultivars IAC 202 and IRGA 417 modified by irradiation. Starch samples were irradiated by (60)Co in doses 1, 2 and 5kGy, on a rate of 0.4kGy/h. A control not irradiated was used for comparison. The granule morphology and A-type X-ray diffraction pattern were not altered by irradiation. There was an increase in amylose content, carboxyl content and acidity with irradiation. Gamma radiation did not affect the thermal properties of IAC202, but increased gelatinization temperature of IRGA417, in the higher dose (5kGy). The number of long chains of amylopectin was reduced and short chains were increased for IAC202, whereas for IRGA 417, the opposite was observed, probably due to cross-linking of starch chains. Starches had their physicochemical and structural properties modified by irradiation differently.

Caracterização físico-química, funcional e nutricional de duas cultivares brasileiras de arroz

O objetivo deste trabalho foi realizar a caracterizacao fisico-quimica, funcional e nutricional de duas cultivares brasileiras de arroz. O arroz da cultivar IAC 202 apresentou maior temperatura de gelatinizacao, absorcao de agua, volume de expansao, perda de solidos, pegajosidade e amido lentamente digerivel. O arroz da cultivar IRGA 417 apresentou maior teor de proteinas, lipideos, amilose aparente, viscosidade em RVA, dureza, amido rapidamente digerivel e amido resistente. O arroz IRGA 417 apresentou caracteristicas de textura mais apreciada pelos brasileiros, com grao cozido mais firme e menos pegajoso. Alem disso, apresentou vantagem nutricional sobre o IAC 202 pelo maior teor de proteinas e amido resistente.

Influence of gamma radiation on the physical and sensory properties of two Brazilian rice cultivars.

BACKGROUNDnLittle has been reported about the effects of gamma radiation on the physical and sensory characteristics of rice. Samples were irradiated with 60 Co in doses 0, 1, 2 and 5u2009kGy, on a rate of 0.4u2009kGy h-1 .nnnRESULTSnThe evaluation of instrumental color showed that increasing doses promoted the yellowing (higher b* value) of the rice grains. Hardness was decreased and stickiness was increased in cooked rice with increasing doses. Sensory evaluation using quantitative descriptive analysis showed that increasing doses promoted higher occurrence of yellowish appearance, emergence of burnt aroma, and an increase of bitter and burnt taste. The sensory acceptance test by 9-point hedonic scale showed alteration of the samples irradiated with 5u2009kGy in all evaluated attributes (appearance, color, aroma, taste and texture). The lowest dose (1 kGy), however, had good acceptability by the panelists.nnnCONCLUSIONnRice may be subjected to 1 kGy dose of gamma radiation without changes or with small changes in physical properties and with good overall acceptability.