Pablo D. Ribotta

Evaluation of the mechanical damage on wheat starch granules by SEM, ESEM, AFM and texture image analysis.

The effect of mechanical damage on wheat starch granules surface, at a microstructural level, was investigated by scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), atomic force microscopy (AFM), and image textural analysis. The SEM and ESEM images of the native sample showed that the starch granules had smooth, flat surfaces and smooth edges. The samples with higher damaged starch content exhibited granular distortion, irregularity and less uniformity. The fractal dimension of contour parameter increased with mechanical damage, indicating that the surface irregularities quantitatively increased due to the damage. The surfaces of damaged granules showed depressions of different shapes and sizes. The roughness parameters and fractal dimension of the surface increased as a result of the mechanical damage. The surface of damaged granules showed higher entropy and lower homogeneity values when damaged starch increased. The results indicated that the mechanical process caused structural modifications at nano level.

Use of enzymes to minimize the rheological dough problems caused by high levels of damaged starch in starch–gluten systems

BACKGROUNDnDuring wheat milling, starch granules can experience mechanical damage, producing damaged starch. High levels of damaged starch modify the physicochemical properties of wheat flour, negatively affecting the dough behavior as well as the flour quality and cookie and bread making quality. The aim of this work was to evaluate the effect of α-amylase, maltogenic amylase and amyloglucosidase on dough rheology in order to propose alternatives to reduce the issues related to high levels of damaged starch.nnnRESULTSnThe dough with a high level of damaged starch became more viscous and resistant to deformations as well as less elastic and extensible. The soluble fraction of the doughs influenced the rheological behavior of the systems. The α-amylase and amyloglucosidase reduced the negative effects of high damaged starch contents, improving the dough rheological properties modified by damaged starch. The rheological behavior of dough with the higher damaged-starch content was related to a more open gluten network arrangement as a result of the large size of the swollen damaged starch granules.nnnCONCLUSIONnWe can conclude that the dough rheological properties of systems with high damaged starch content changed positively as a result of enzyme action, particularly α-amylase and amyloglucosidase additions, allowing the use of these amylases and mixtures of them as corrective additives. Little information was reported about amyloglucosidase activity alone or combined with α-amylase. The combinations of these two enzymes are promising to minimize the negative effects caused by high levels of damaged starch on product quality. More research needs to be done on bread quality combining these two enzymes.

Optimization of soybean heat-treating using a fluidized bed dryer

This study was designed to optimize drying and inactivation of heat-labile inhibitors conditions of soybean by using a fluidized bed dryer, in order to shorten treatment time and to reduce losses in end-product quality such as soy flour color and soy protein solubility. The independent variables were initial moisture of soybeans, heating time and temperature of air entering the fluidization chamber. The response variables studied were final moisture of soybeans, inactivation of urease, soy flour color and soy protein solubility. Response surface methodology was able to model the response of the different studied variables. For each response group, relevant terms were included into an equation; the behavior of response was predicted within the experimental area and was presented as a response surface. The results suggested that a combination of soybean initial moisture of 0.14xa0g/g (wb), treatment time of 3.4xa0min and hot-air temperature of 136.5xa0°C could be a good processing combination of parameters for heating soybean using hot-air in order to reduce treatment time and quality losses in soybean flour. Thus, fluidized bed drying technology may be used as an alternative industrial method to eliminate the antinutritional factors.

Effect of different fibers on dough properties and biscuit quality

BACKGROUNDnThis study forms part of a broader project aimed at understanding the role of fibers from different sources in high-fat, high-sugar biscuits and at selecting the best fibers for biscuit quality. The main purpose of this work was to understand the rheological and structural properties involved in fiber-enriched biscuit dough. High-amylose corn starch (RSII), chemically modified starch (RSIV), oat fiber (OF) and inulin (IN) were used at two different levels of incorporation (6 and 12 g) in dough formulation. The influence of fiber on the properties of biscuit dough was studied via dynamic rheological tests, confocal microscopy and spreading behavior. Biscuit quality was assessed by width/thickness factor, texture and surface characteristics, total dietary fiber and sensory evaluation.nnnRESULTSnMain results indicated that IN incorporation increased the capacity of dough spreading during baking and thus improved biscuit quality. OF reduced dough spreading during baking and strongly increased its resistance to deformation. RSII and RSIV slightly affected the quality of the biscuits. Sensory evaluation revealed that the panel liked IN-incorporated biscuits as much as control biscuits.nnnCONCLUSIONnThe increase in total dietary fiber modified dough behavior and biscuit properties, and the extent of these effects depended on the type of fiber incorporated.

Wheat germ stabilization by infrared radiation

Wheat germ has an important enzymatic activity, being lipases the enzymes which cause the highest impact in the reduction of shelf life. The objective of this study was to evaluate the effects of infrared radiation on wheat germ stabilization in an attempt to extend the shelf life. The effects of treatment time, gap (sample distance to IR emitters) and infrared radiation intensity on wheat germ were analyzed through response surface methodology. Final moisture content, final temperature, color of germ and germ oil quality parameters: free fatty acid content changes and total tocopherol content were the responses evaluated using a Box-Behnken design. A combination of an infrared radiation intensity of 4800xa0W/m2, a 3xa0min treatment and 0.2xa0m emitter-sample distance were the best processing condition to stabilize the wheat germ without significantly reduction of the tocopherol content. A confirmatory experiment was conducted with these optimal conditions, and the heat-treated and raw germ samples were stored for 90xa0days at room temperature in three layer packages to protect them against light and oxygen. The oil quality parameters indicated that the raw germ had a shelf-life of about 15xa0days, with the heat-treated wheat germ maintaining its quality for at least 90xa0days under these stored conditions.

Effect of defatted almond flour on cooking, chemical and sensorial properties of gluten-free fresh pasta

Summary nThe aim of this work was to analyse the influence of defatted almond flour on soya bean-based gluten-free pasta. Optimal cooking time of pasta varied between 2.0 and 3.5xa0min, while cooking loss ranged 6.1% and 19.7%. The total protein content of samples varied from 30.4% to 41.0% (dry basis, db) in cooked pasta. The total phenols content of cooked samples varied between 1.66 and 2.99xa0mg ellagic acid equivalent/g, while the antioxidant activity (DPPH•) ranged between 19.1% and 41.9%. The sensory test showed no significant differences between the formulated pasta samples among brightness (3.20–3.27), surface appearance (1.14–1.20), hardness (2.14–2.36) and elasticity (1.56–1.71). Pasta developed is an innovative product that improves nutritional and functional properties of gluten-free pasta compared to gluten-free and traditional wheat flour pasta available on market.