Thermomechanical characterization of an amylose-free starch extracted from cassava (Manihot esculenta, Crantz)The International Center for Tropical Agriculture (CIAT) believes that open access contributes to its mission of reducing hunger and poverty, and improving human nutrition in the tropics through research aimed at increasing the eco-efficiency of agriculture.CIAT is committed to creating and sharing knowledge and information openly and globally. We do this through collaborative research as well as through the open sharing of our data, tools, and publications. Citation:Pulido This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. THERMOMECHANICAL CHARACTERIZATION OF AN AMYLOSE-FREE STARCH EXTRACTED FROM CASSAVA (Manihot HighlightsThermal transitions measurements were made by DSC and DMTA.Thermal behaviors of waxy cassava follow the Flory Huggins theory.Waxy cassava starch has phase transitions similar to a waxy corn starch. AbstractThe aim of this study was to determine and compare the melting (T m ), glass transition (T g ) and mechanical relaxation (T  ) temperatures of a new waxy cassava starch. Thermal transitions measurements were obtained by Differential Scanning Calorimetry (DSC) and Dynamical Mechanical Thermal Analysis (DMTA). The experimental data showed a high correlation between water volume fraction and melting temperature (T m ) indicating that the Flory-Huggins theory can be used to describe the thermal behavior of this starch. The T m of waxy cassava starch-water mixes were lower than a waxy corn starch-water reference system, but differences were not statistically significant. The mechanical relaxation temperatures taken at tan δ peaks were found 29-38 °C larger than T g . The T  and T g measured for waxy cassava starch exhibited similar properties to the ones of waxy corn starch, implying that waxy cassava starch can be used in food and materials industry.

A dough made of amylaceou materials shows a viscoelastic behavior, its macrostructural behavior depends on processing conditions, its constituents and the interaction among them. Studies on dough rheology and texture are useful and important for applications that include ingredient specifications, quality control, product design and adaptation of new processing technologies. This work is a review of rheological and textural principles, testing methods and characteristics of wheat and corn doughs.

Las propiedades texturales de masas preparadas a partir de harina de yuca precocida fueron estudiadas con el fin de determinar el efecto de las condiciones de proceso en sus características físicas. El módulo de deformabilidad, la dureza, la cohesividad y la adhesividad de masas reconstituidas de harina de yuca se evaluaron utilizando un analizador de textura. Trozos de parénquima de yuca procesados a diferentes condiciones de cocción y almacenados a baja temperatura (-5 ºC y -20 ºC) por 24 h se emplearon para elaborar las harinas. Cuando la temperatura en el período de almacenamiento del parénquima cocinado disminuyó de -5ºC a -20ºC, el módulo de deformabilidad, la dureza y la cohesividad de la masa aumentaron significativamente. Se concluye que la temperatura en el período de reposo del parénquima cocinado es el factor más importante que afecta las propiedades texturales de la masa de yuca.

Promoting food security in Latin-America and the Caribbean is directly related to agricultural products. The region faces a food crisis which has reduced large population groups' access to food. This work contributes to the study of obtaining precooked composite flour made from biofortified crops using protein, vitamin A and/or minerals. This study evaluated the effect of precooked flour's composition and precooking on its solubility in water, water absorption capacity, consistency and viscosity; such flour was obtained by extrusion and drying on rollers. The composite flours were obtained from cassava roots, sweet potato tubers, corn, rice and bean grains and cassava leaves. Four composite flours were formulated taking four- to six-year-old children's daily nutrient requirements (protein, iron, zinc and beta-carotenes) as a basis. The extruder was operated at 90oC, 300 rpm screw rotation speed, 17.64 g/min feed flow, with 30% moisture mixture. The dryer rollers were operated at 4 rpm roller rotation speed, 90oC surface temperature and 1 mm separation between rollers. It was determined that flour dried on rollers led to more complete cooking and modified starch granule structure than precooking by extrusion, thereby producing flour having greater solubility in water, less water absorption, higher consistency and smaller viscosity, comparable to that of pattern flour.