Propiedades fisicoquímicas y de panificación de dos variedades de trigo (Triticum aestivum) secadas por lecho fluidizado Público Deposited
Se evaluaron las caracteristicas fisicoquimicas y de panificacion de dos variedades de trigos comerciales, Oasis F89 de textura dura y gluten fuerte y Salamanca S75 de textura suave y gluten debil, que fueron secadas por lecho fluidizado a diferentes tiempos y temperaturas. El trabajo se desarrollo en tres etapas 1) Muestras representativas de 1 kg de cada variedad de trigo, se humedecieron 22% y se sometieron a tratamiento termico a 40, 60, 80 y 100•‹C por 60 minutos en todos los casos. Se uso un secador de lecho fluidizado a nivel de laboratorio con aire de 0.008 kg H20/kg de aire seco y una velocidad superficial de 1.52 mls. A los granos despues del secado se les determino, peso hectolitrico, dureza, peso de 1000 granos. A las harinas obtenidas a partir del grano se les determino contenido de proteina total, de gluten y de cenizas. a las masas de trigo pruebas reologicas, medidas con el farinografo y extensografo de Brabender, con el alve6grafo de Chopin y con el mixografo de Swanson, por ultimo se determinaron las caracteristicas del pan. 2) Las variedades de trigo se ajustaron a 17, 25 y 37 %h y se secaron bajo las mismas condiciones del primer experimento. Se determino la cinetica de secado y la energia de activacion segun la ley de Arrenhius. A los granos despues del secado se les determino peso hectolitrico y dureza. A las harinas, contenido de proteina total, a las masas de trigo pruebas reologicas (medidas con alveografo de Chopin y mixografo de Swanson), y al pan sus caracteristicas. 3) Las dos variedades de trigos con 20 y 15 %h se secaron a temperaturas de 40, 60, 70, 80 y 100•‹C hasta alcanzar humedades finales de entre 11 y 9% Se realizaron las cineticas de secado y la determinacion de la energia de activacion. A los granos se les determino, peso hectolitrico y dureza, a las harinas, proteina soluble en NaCI, a las masas de trigo sus caracteristicas, medidas con mixografo de Swanson y al pan su volumen. Finalmente se realizo analisis electroforetico a las harinas de trigo. En general la temperatura de secado mostro mayor efecto significativo sobre la calidad industrial del trigo que la humedad inicial del grano y la variedad del trigo. Los valores del peso hectolitrico y dureza (textura) fueron significativos (p<0.05) entre variedades, contenido de humedad del grano y temperaturas de secado. Los ccntenidos de cenizas y de proteina total de las harinas solo presentaron diferencias significativas (p<0.05) entre variedades, indicando entre variedades, indicando que el tratamiento termico del trigo no afecto el contenido total de nitrogeno proteico ni el de minerales de las harinas. Los porcentajes de gluten y la concentracion de proteina soluble, fueron significativos (p<0.05) entre variedades y temperaturas, disminuyendo en relacion directa con el aumento de temperatura Las caracteristicas reologicas de las masas de trigo presentaron diferencias significativas (p<0.05) entre variedades, temperaturas y contenido de humedad del grano, mostrando cambios en relacion directa con el grado de desnaturalizacibn del gluten y el volumen del pan. La solubilidad en Na CI de las proteinas del trigo disminuyo conforme la temperatura de secado aumento. Ambas variedades de trigos secadas a 40,60 y 70% reportaron valores semejantes a los del trigo control correspondiente. Por el contrario el tratamiento termico drastico a 80 y 100•‹C reporto masas de trigo menos elasticas, de mala calidad panadera con leudado deficiente o nulo. Los resultados mostraron gluten mas resistente al tratamiento termico para el trigo Oasis con 9% de proteina que para el trigo suave de la variedad Salamanca con 8%. El analisis electroforetico realizado a las harinas de trigo sometido a tratamiento termico mostro que los cambios medidos pueden ser atribuidos principalmente a la desnaturalizacibn termica de las proteinas del gluten.
The effect of fluidized bed drying on the physicochemical characteristics of two wheat varieties, used in the breadrnaking industry, was studied. The two varieties were a hard texture, strong gluten Oasis F89 wneat, and a soft texture, weak gluten Salamanca S75 wheat. The study consisted into three experimental parts: 1) lnitial rnoisture content of two wheat varieties was adjusted to 22% ( dry basis);drying was canied out at 40, 60, 80 and 100C during 60 rnin. Each batch was hurnidified and subjected to heat treatrnent in a batch scale fluidized-bed dried. Drying conditions were: air rnoisture content: 0.008 kg H20lkg dry air, velocity at the surfacee:1.52 rnls. Drying kinetics was obtained for the experimental condition. Grains were analyzed for hectoliter weight, hardness, weight of 1000 grains and rnilling yield. The flour obtained frorn the dried grain was analyzed for protein content, dry gluten, sishes and sedirnentation rate; rheological test were determined in the dough using a Brabender farinograph and arnylograph, Chopin alveograph, and Swanson rnixograph. Finally the loaf volurne was determined. Frorn these analysis several quality determinations were concluded to be the rnost suitable for the next part. 2) The two wheat varieties were adjusted to 17, 25 and 37% rnoisture content (dry basis) and dried at the same ternperature and time as described for the first part. Drying kinetics were studied obtaining the activation energy according to the Arrhenius equation. The grain obtained after drying were analyzed for hectolitre weight and hardness; the flour was analyzed fcr protein content and sedirnentation rate, and the dough fort rheological pararneters ( as obtained frorn Chopin alveograph and Swanson rnixograph); loaf volume was also determined. 3) the two varieties, with 15 and 20 % initial rnoisture content, were dried at 40, 60, 80 and 100•‹C and different time periods until reaching 9 to 13% final rnoisture content. In this part, drying kinetics and activation energy were also obtained. The dried grain was analyzed for hectoliter weight and hardness; the flour for total protein content and protein soluble in NaCI; the dough was analyzed with a Swanson rnixograph and for loaf volurne. Protein in the flour was analyzed by electrophoresis. The results showed that ternperature was the most SignifiCant effect on wheat industrial quality. Wheat variety and initial moisture content were significant in a lesser extent. Heclolitre wiqh and hardness were significant (pc0.05) for wheat varieties, moisture content and drying time. Grain hardness was more affected by heat treatment than hectoliter weight, but did not efficiently detect damage in the grain. Ash and total protein content had significant differences (pc0.05) between varieties, showing that thermal treatment did not affect total protein nitrogen nor mineral content. Gluten and soluble protein content were also significant (pc0.05) for wheat variety. time and temperature, decreasing as the temperature increased. Wheat rheological characteristics showed significant differences (pc0.05) for wheat varieties, moisture content and drying time. Grain hardness was more affected by heat treatment than hectoliter weight, but did not efficiently detect damage in the grain. Ash and total protein content had significant differences (pc0.05) between varieties, showing that thermal treatment did not affect total protein nitrogen nor mineral content. Gluten and soluble protein content were also significant (pc0.05) for wheat variety. time and temperature, decreasing as the temperature increased. Wheat rheological characteristics showed significant differences (p<0.05) for variety, temperature moisture content and drying time. Rheological analysis showed that changes in wheat dough viscoelastic properties was directly correlated to the gluten denaturation degree, as estimated by changes in the loaf volume. The protein soluble in NaCl decreasing as the temperature increased. When both wheat varieties were dried at 40 OC, 60•‹C and 70•‹C they showed values similar to those obtained with the respective control. Extreme heat treatment (80 and 100•‹C) rendered low breadmaking quality flours with deficient of none leavening capacity. In addition, more resistant gluten for heat treatment was observed in 9% protein Oasis variety than for 8% protein Salamanca variety, dried at different temperatures. Electrophoresis suggested that changes in severe heat-treated wheat may be dueto gluten thermal denaturation.
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