CAMBIOS DE SOLUBILIDAD DE LAS PROTEÍNAS DE MAÍZ DURANTE EL PROCESO DE ELABORACIÓN DE LA TORTILLA A DIFERENTES TIEMPOS DE COCIMIENTO

El objetivo de esta investigación fue determinar el efecto del tiempo de cocimiento alcalino sobre los cambios en solubilidad que sufren las proteínas del maíz durante la obtención de los diferentes productos del proceso de elaboración de la tortilla. Lotes de 20 kg de maíz fueron sometidos a nixtamalización usando una concentración de cal de 1 % a temperatura de ebullición del agua. Se probaron tres tiempos de nixtamalización (25, 45 y 65 min). Después de 14 h de reposo, el maíz se lavó para obtener el nixtamal, el cual se llevó a una tortillería comercial para ser molido y elaborar los discos de masa que fueron cocidos en un horno de tres bandas. Las muestras obtenidas del proceso fueron maíz, nejayote, nixtamal, masa y tortilla a las cuales se les realizó extracción de proteínas por el método de Paulis (1975) y Paulis y Wall (1979). La cuantificación de las fracciones proteínicas se llevó a cabo por el método de Lowry modificado por Hartree (1972). Se utilizó un diseño factorial con dos factores: El tiempo de cocimiento (25, 45 o 65 min) y el tipo de producto obtenido (nejayote, nixtamal, masa y tortilla). Este diseño fue aplicado a cada fracción proteínica. A los datos obtenidos se les realizó un análisis de varianza con un nivel de significancia del 95 %. La fracción proteínica I (albúminas y globulinas) mostró los valores más altos de solubilidad en nejayote para los tres tiempos de cocimiento, mientras que para la fracción II (prolaminas) la solubilidad en nejayote, nixtamal, masa y tortilla se mantuvo casi constante a los 25 y 45 min de cocimiento, sin embargo, a los 65 min de cocimiento se observó un incremento significativo en nejayote y tortilla. La fracción proteínica III (gluteninas reducidas) mostró incrementos en solubilidad a partir de la obtención del nixtamal para los tres tiempos de cocimiento. La fracción proteínica IV (gluteninas) incrementó su solubilidad en la etapa de obtención del nixtamal, sin embargo, a partir de ese producto se presenta una disminución hasta la obtención de la tortilla

Grading Factors of Wheat Kernels Based on Their Physical Properties

Cereal grains are biological materials and as such have certain unique characteristics greatly affected by both genetics and environment. Wheat is worldwide considered as the main cereal grain in the average human diet. The aim of this chapter is to provide an overview of the most important grading factors and kernel physical parameters that are involved in the estimation of quality specifications. The determination of the physical properties of wheat kernels gives a first approximation of the structural characteristics useful for the design and selection of equipment for handling, harvesting, aeration, drying, storing and more importantly to functionality, processing and end uses. For instance, physical quality test that directly measure those properties are needed. To get a better prediction, physical evaluation of the wheat kernels offers a first and interesting quality control for their selection as raw materials in order to optimize quality of a large diversity of products. Kernel colour, shape, size, sphericity, porosity and bulk and specific densities and damages incurred due to heat, insects, molds or sprouting are relevant tests related to wheat kernel properties and quality

Mechanical Properties in Wheat (Triticum aestivum) Kernels Evaluated by Compression Tests: A Review

To assess the quality of food grains, it is necessary to consider the following two aspects: their general characteristics and their intrinsic quality. Analyzing the quality of wheat kernels is complex due to the particularity of wheat proteins and the diversity of products that can be developed. In contrast, basic factors are used to assess quality aspects, with a focus on kernel hardness. This parameter is usually measured by the force that is required to make the grain rupture. The application of force must be controlled, and hence, the grain will exhibit other mechanical attributes and behavioral characteristics that can be used to evaluate it more objectively. This has led to the development of nondestructive evaluation methods based on the mechanical properties of kernels. This review carried out research on grain wheat, in which the main objective was to evaluate mechanical properties, including the viscoelasticity of the wheat kernels, by using compression tests. The study examined different methods of applying those techniques and the parameters they evaluated. Finally, the results obtained by the different investigation groups that applied the compression tests on wheat kernels were discussed

Physicochemical and Rheological Changes of Starch in Nixtamalization Processes: Extrusion as an Alternative to Produce Corn Flour

Corn tortilla is a food consumed mainly in México and Central America. It provides 50% of total calories ingestion and is a good source of fiber. Tortilla is produced by the nixtamalization process using corn, water and lime. It has been produced by alternative processes as extrusion, reducing cooking liquor, and increasing dietary fiber. The aim of this book chapter is to describe the changes in corn starch by different nixtamalization processes, also are presented the advantages and disadvantages of both processes, encouraging some aspects of producing corn flour by extrusion. The extrusion is a technology that is dependent of process variables and is reflected on quality of end product. Several factors are involved, as feed moisture and temperature, and they have a direct impact on corn starch physicochemical, textural, and rheological properties