R.G. Campos-Montiel

The effect of drying temperature on mechanical properties of pig skin gelatin films El efecto de la temperatura de secado sobre las propiedades mecánicas de películas de gelatina de cerdo

Films from three different bloom strength were prepared and dried at three different temperatures (20 °C, 40 °C and 60 °C) to investigate whether the differences in ordering and aggregation during film formation, under controlled drying conditions, reflect changes in their mechanical properties. Results showed that Youngs modulus (E) was not significantly (p ≤ 0.05) influenced by the drying regime because it remained around 3.0 GPa. Film A-270 dried at 20 °C showed higher fracture properties when compared with the same sample dried at 40 °C and 60 °C. Brittleness followed: 60 °C > 40 °C > 20 °C. A-100 was sensitive to 60 °C because there was no formation of a continuous network. Films with higher bloom index showed improved fracture properties, it followed A-270 > A-160 > A-100. Films reflected lower degree of crystallinity (∼0%) as the drying temperature increased; the higher the crystallinity (∼33%), the better the fracture properties. Films formed at 40 °C and 60 °C showed mostly an amorphous structure. Películas con tres diferentes grados de firmeza de gel fueron elaborados y secados a tres diferentes temperaturas (20 °C, 40 °C y 60 °C) para investigar si las diferencias en reorganización y agregación durante la formación de película bajo condiciones de secado controladas refleja cambios en sus propiedades mecánicas. Los resultados mostraron que el módulo de Young (E) de las películas no fue influenciado significativamente (p ≤ 0,05) por el régimen de secado debido a que éste permaneció alrededor de 3,0 GPa. La película A-270 secado a 20 °C mostró mejores propiedades de fractura en comparación a la misma muestra pero secada a 40 °C y 60°. La rigidez en películas siguió la tendencia: 60 °C > 40 °C > 20 °C. A-100 fue sensitiva a 60 °C porque no hubo formación de una red continua. Las películas con alto nivel de firmeza de gel mostró mejores propiedades de fractura, esta tendencia mostró A-270>A-160>A-100. Las películas reflejaron bajo grado de cristalinidad (∼0%) mientras que la temperatura de secado se incrementaba, cuanto más alta la cristalinidad (∼33%) mejores fueron las propiedades de fractura. Películas formadas a 40 °C y 60 °C mostraron una estructura amorfa.

Extraction and characterization of collagen from rabbit skin: partial characterization

Extraction and characterization of collagen were carried out in rabbit skins as a new alternative for collagen type I. Acetic acid and pepsin were for the extraction of soluble and insoluble collagen, respectively. The enzymatic treatment yielded higher amount of collagen (71%). The average pH value was 6.3, no matter what the method of extraction was. Denaturation temperature of collagen was found at 36°C approximately in two different techniques: Rheometer and Differential Scanning Calorimetry (DSC). Despite the amount of collagen in solution was low, its viscosity was high because of the hydrodynamic behaviour of collagen molecules. Sodium dodecyl sulphate polyacrylamide gel electrophoresis results showed three different bands that reflected two alpha-chains and one beta-chain with molecular weights of 102, 118 and 220 kDa, respectively. Determination of hydroxyproline gave evidence that the extracted material was collagen. It was concluded that rabbit skin could be an alternative source for the extraction of collagen.

Characterization of a yeast culture extract compound stimulating the growth of an anaerobic cellulolytic consortium

In this work the compound obtained from yeast culture extract (YCE) that stimulated the activity of an anaerobic cellulolytic consortium (ACC) was characterized. YCE were obtained at different pH (4, 7 and 10) and ultra-filtered 300 and 30 kDa membranes (UYE). The 30 kDa UYE was heated to 60 °C, 90 °C and 120 °C and gel filtered (GYF). Mid infrared spectroscopy, protein and carbohydrate analysis of GYF were conducted. Results showed that YCE, UYE and GYF significantly stimulated (p < 0.05) the biomass production, acetate concentration and carboxymethyl cellulase activity of the ACC, in relation to the control. The GYF had an estimated molecular mass of 4 kDa. Mid-infrared and biochemical analysis of GYF suggested that the active compound is a peptide.