Influence of drying and hydrothermal treatments on the denaturation of corn proteins

Poster (2013, February 08)

Corn (Zea mays L.) is the most abundant cereal grain produced in the world. It also provides a significant amount of protein in human and animal diets. During drying corn grains undergo several ... [more ▼]

Corn (Zea mays L.) is the most abundant cereal grain produced in the world. It also provides a significant amount of protein in human and animal diets. During drying corn grains undergo several alterations including protein denaturation. A series of studies have been conducted in order to understand mechanisms behind denaturation of corn proteins during drying and heat moisture treatments. Using a laboratory fluidized-bed dryer, a flint corn variety have been dried between 54° and 130°C and subjected to different analyses from a qualitative point of view with a sequential extraction of corn protein fractions and from a quantitative point of view with the modeling of salt-soluble proteins using Promatest assay. Albumin, globulin and zein solubilities dropped significantly when the drying temperature increased. The electrophoretic patterns of zein and glutelin-G1 were not significantly modified, although the solubility of zein was affected by the drying temperature. The analysis of the different protein group solubilities suggested that denaturation mechanisms other than the creation of new disulfide bonds occurred during the drying of corn at high temperature. The study of the effect of heat treatments on the extractability of salt-soluble proteins shows that temperature; moisture content and time of processing greatly influence their kinetic denaturation. Modeling of salt-soluble proteins reveals that the evolution of extractible salt-soluble proteins content of corn kernels during drying at high temperature is more correctly described with a second order kinetic reaction. Investigations continue in order to understand protein denaturation and influence in functional properties and end-use of corn protein-based products. [less ▲]

Improvement of the cellulose hydrolysis yields and hydrolysate concentration by management of enzymes and substrate input

in Cerevisia : Belgian Journal of Brewing and Biotechnology (2012), 37

In order to improve the hydrolysis of cellulose fiber and to obtain highly concentrated hydrolysate, two methods based on successive addition of enzyme and substrate were assessed. The first method, which ... [more ▼]

In order to improve the hydrolysis of cellulose fiber and to obtain highly concentrated hydrolysate, two methods based on successive addition of enzyme and substrate were assessed. The first method, which required only substrate addition, allowed to increase by 50% the hydrolysate concentration and to decrease by 30% enzyme units needed. The second method highlighted the ability to reach very high concentrated hydrolysate (up to 170 g/l) by simultaneous addition of enzyme and substrate. In parallel, relationships between some limiting factors and the yields of hydrolysis were investigated. In conclusion, viscosity evolution of cellulose suspension during hydrolysis step was investigated with an aim to improve the management of enzyme and substrate addition. [less ▲]

Structure de l’amidon de maïs et principaux phénomènes impliqués dans sa modification thermique

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(2), 315-326

Modelling dehydration and quality degradation of maize during fluidized-bed drying

in Journal of Food Engineering (2010), 100(3), 527-534

At harvest time, maize (Zea mays L.) has a moisture content too high to be stored, and has to be dried. To control the previous termdryingnext term impact on maize characteristics, it is necessary to ... [more ▼]

At harvest time, maize (Zea mays L.) has a moisture content too high to be stored, and has to be dried. To control the previous termdryingnext term impact on maize characteristics, it is necessary to accurately know the spatial distribution of temperature and moisture content in the kernel, and the kinetics of quality loss in relation to these two factors. To this end, a physical model of heat and mass transfer in a maize kernel was designed. The Fick and Fourier equations were solved by the finite element method (FEM). The real 3D geometry of maize was obtained by NMR imaging and then used to build the mesh needed for the FEM computations. The model correctly describes the evolutions of maize moisture and salt-soluble protein content during fluidized-bed previous termdryingnext term with a constant previous termdryingnext term air temperature between 50 °C and 100 °C. [less ▲]

Comparative study of the effect of drying temperatures and heat-moisture treatment on the physicochemical and functional properties of corn starch

in Carbohydrate Polymers (2010), 79(3), 633-641

This manuscript compares the modifications induced by the heat-moisture treatment of native starch (HMT) and by the hot-air drying of corn on wet-milled starch granules. High temperatures applied during ... [more ▼]

This manuscript compares the modifications induced by the heat-moisture treatment of native starch (HMT) and by the hot-air drying of corn on wet-milled starch granules. High temperatures applied during both corn drying and HMT reduced the swelling capacity of granules, increased the starch gelatinization temperatures and decreased their residual enthalpy. Pasting behaviour of pre-treated starch showed a decrease of peak and breakdown viscosity when corn drying and HMT temperatures increased. Microscopic analysis showed that after hydrothermal treatment, starch granules extracted from corn dried at lower temperature swell more significantly than those extracted from corn dried at higher temperature. All these changes suggest the occurring of structural modifications within starch granules during high-temperature pre-treatments. At similar temperatures and initial moisture contents, HMT affected the physicochemical and functional properties of cornstarch more dramatically than hot-air drying. Differences induced by these two treatments were attributed to the availability of water around granules during these two pre-treatment procedures. [less ▲]

Influence of drying temperature on the wet-milling performance and the proteins solubility indexes of corn kernels

in Journal of Food Engineering (2009), 95

The effects of air drying temperature on the wet-milling performance and the proteins solubility indexes were investigated for corn kernels dried between 54°C and 130°C. It was observed that when the ... [more ▼]

The effects of air drying temperature on the wet-milling performance and the proteins solubility indexes were investigated for corn kernels dried between 54°C and 130°C. It was observed that when the drying temperature increases, the starch yield drops significantly. The gluten recovered increased abruptly for drying temperatures up to 80 C. The albumin, globulin and zein solubility indexes decreased continuously when corn drying temperatures increased. According to the temperatures used, the starch yield, the gluten recovered and the salt-soluble proteins solubility indexes were adjusted satisfactorily by using a two asymptotic logistic model. This model has the advantage of supplying information on the dynamic of the variation of described parameters. The solubility index of total salt-soluble proteins was shown to be a suitable indicator of the severity of the drying treatment in regard to the corn wet-milling performance. [less ▲]

Causes et mécanismes de la perte de l’aptitude au fractionnement du maïs séché à haute température

Poster (2007, December 10)

Le séchage par entrainement d’air chaud dénature les principales familles des protéines du maïs, ce qui entraine la diminution de leur solubilité. Les températures élevées de séchage induisent également ... [more ▼]

Le séchage par entrainement d’air chaud dénature les principales familles des protéines du maïs, ce qui entraine la diminution de leur solubilité. Les températures élevées de séchage induisent également une diminution de l’aptitude à l’imprégnation d’eau des grains lors du trempage des maïs avec pour conséquence la diminution du ramollissement des grains, ce qui occasionne des moutures imparfaites et une réduction de la libération des granules d’amidon lors des phases de séparation de l’amidon et des protéines. La fonction logistique à deux asymptotes permet une meilleure prévision des rendements d’extraction de l’amidon et des quantités des glutens récoltées au tamisage en fonction de la température du séchage. [less ▲]

Influence de la température de séchage sur les propriétés physicochimiques des amidons de maïs

in Kechaou (Ed.) Actes du Séminaire d'animation régionale sur les Technologies douces et les procédés de séparation au service de la qualité et de l'innocuité des aliments (2006, November 27)

Les amidons extraits des grains de maïs séchés aux températures de l’air comprises entre 54 et 130°C ont été caractérisés par Analyse Calorimétrique Différentielle (ACD), par granulométrie laser, par ... [more ▼]

Les amidons extraits des grains de maïs séchés aux températures de l’air comprises entre 54 et 130°C ont été caractérisés par Analyse Calorimétrique Différentielle (ACD), par granulométrie laser, par microscopie sous lumière polarisée et par diffraction des rayons-X. Il ressort de cette étude que le séchage aux températures élevées induit une modification des propriétés intrinsèques des amidons sans pour autant induire leur gélatinisation complète [less ▲]

Influence du séchage par entraînement d’air chaud sur l’aptitude au fractionnement par voie humide du maïs

in Sakho, Mama; Crouzet, Jean (Eds.) Transformation, Conservation et Qualité des Aliments : Nouvelle Approche de Lutte contre la Pauvreté (1998)

Le séchage par entrainement d’air chaud dénature les principales familles des protéines du maïs, ce qui entraine la diminution de leur solubilité. Les températures élevées de séchage induisent également ... [more ▼]

Le séchage par entrainement d’air chaud dénature les principales familles des protéines du maïs, ce qui entraine la diminution de leur solubilité. Les températures élevées de séchage induisent également une diminution de l’aptitude à l’imprégnation d’eau des grains lors du trempage des maïs avec pour conséquence la diminution du ramollissement des grains, ce qui occasionne des moutures imparfaites et une réduction de la libération des granules d’amidon lors des phases de séparation de l’amidon et des protéines. Une fonction polynomiale de troisième degré est proposée pour prévoir le rendement d’extraction des amidons en fonction des températures appliquées pendant le séchage du maïs de variété Baltimore. [less ▲]