Analysis of drying kinetic of brewer ́s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds / Análisis de la cinética de secado del bagazo residual de malta: efecto de la temperatura sobre las propiedades físicas y el contenido de compuestos bioactivos

Background: Brewer ́s spent grain (BSG) is a biomass by-product generated in large volumes during industrial beer production. BSG has become a growing environmental problem, as most breweries discard it inappropriately, negatively impacting the environment. Alternatives for the exploitation of this by-product have consisted of elaborating food supplements for farm animals, obtaining biofuels, developing adsorbents, and obtaining substances for the food industry. However, the high moisture content in BSG (approximately 70%), poses a significant challenge in exploring various reuse alternatives. Therefore, the implementation of a pre-drying process becomes essential. Objective: This study aimed to analyze the BSG drying kinetics at different temperatures and the effect of the drying temperature on the physical properties and the content of bioactive compounds. Methods: BSG samples were dried at different temperatures (50, 60, 70, 80, 90, and 105°C) and analyzed for their moisture ratio, water activity, total polyphenol content (TPC), and DPPH (1,1-diphenyl-2-picrylhydrazil) radical scavenging activity. Also, four kinetics models were fitted to the drying data. Results:It was determined that the effective diffusivity was between 5.23x10

Antecedentes: El Bagazo residual de malta (BSG por sus siglas en inglés) es un subproducto biomásico generado en grandes volúmenes durante la producción industrial de cerveza. El BSG se ha convertido en un creciente problema para el medio ambiente, debido a que la mayoría de las cervecerías descartan inapropiadamente este residuo generando un impacto negativo al ambiente. Las alternativas para el aprovechamiento de este subproducto han consistido especialmente en la elaboración de suplementos alimenticios para animales de granja, obtención de biocombustibles, desarrollo de adsorbentes y obtención de productos para la industria alimentaria. Sin embargo, el alto contenido de humedad (~70%) del BSG representa un reto para el desarrollo de diferentes alternativas de reutilización, por lo que se hace necesario un proceso de secado previo. Objetivos: En este estudio se analizó la cinética de secado del BSG a diferentes temperaturas y el efecto de la temperatura de secado sobre sus propiedades físicas y contenido de compuestos bioactivos. Métodos: Las muestras de BSG fueron secadas a diferentes temperaturas (50, 60, 70, 80, 90 y 105°C) y analizadas en términos de razón de humedad, actividad acuosa, contenido de polifenoles totales (TPC) y actividad secuestradora del radical DPPH. Además, se ajustaron 4 modelos cinéticos a los datos de secado. Resultados: Se determinó que la difusividad efectiva del BSG varió entre 5.23x10

Mathematical analysis of the effect of process conditions on the porous structure development of activated carbons derived from Pine cones.

This paper presents the results of a study on the influence of the degree of impregnation and activation temperature on the formation of the porous structure of activated carbons (ACs) obtained from Pine cones by the chemical activation process using potassium hydroxide as an activator. The advanced new numerical clustering based adsorption analysis (LBET) method, together with the implemented unique numerical procedure for the fast multivariant identification were applied to nitrogen and carbon dioxide adsorption isotherms determined for porous structure characterization of the ACs. Moreover, the Quenched Solid Density Functional Theory (QSDFT) method was chosen to determine pore size distributions. The results showed a significant influence of the primary structure of Pine cones on the formation of the porous structure of the developed ACs. Among others, it was evidenced by a very high degree of surface heterogeneity of all the obtained ACs, irrespective of the degree of impregnation with potassium hydroxide and the activation temperature. Moreover, the analysis of carbon dioxide adsorption isotherms showed, that the porous structure of the studied ACs samples contains micropores accessible only to carbon dioxide molecules. The results also showed a significant advantage of the LBET method over those conventionally used for porous structure analysis based on Brunauer-Emmett-Teller (BET) and Dubinin-Raduskevich (DR) equations, because it takes into account surface heterogeneities. The novel analyses methods were more fully validated as a reliable characterization tool, by extending their application to the isotherms for ACs developed from the same precursor by phosphoric acid activation, and for samples arising from these ACs, further subjected to additional post-treatments. The effect of the raw material used as precursor was moreover analysed by comparison with previous reported results for other ACs. The complementarity of the results obtained with the LBET and QSDFT methods is also noteworthy, resulting in a more complete and reliable picture of the analyzed porous structures.

Improvement of the Ultrasound-Assisted Extraction of Polyphenols from Welsh Onion (Allium fistulosum) Leaves Using Response Surface Methodology.

Welsh onion (Allium fistulosum) leaves contain several bioactive compounds that can be extracted and used to develop new value-added products (e.g., functional foods and dietary supplements). In the current work, optimal ultrasound-assisted extraction (UAE) conditions to obtain extracts with high polyphenols content and DPPH (1,1-diphenyl-2-picrylhydrazil) scavenging activity were identified using response surface methodology. A complete 3k factorial design was used to evaluate the effect of different variables of the UAE (extraction temperature, time, and ethanol concentration) on the polyphenols content and the DPPH scavenging activity of the extracts. The best conditions for UAE to reach both the highest values of total polyphenols content (51.78 mg GAE/100 g) and DPPH scavenging activity (34.07 mg Trolox equivalents/100 g) were an extraction temperature of 60 °C, time of 10 min, and ethanol concentration of 70% v/v. The antioxidant activity of the extracts obtained at the optimal conditions was also evaluated by 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) and ferric reducing antioxidant power (FRAP) assays obtaining values of 155.51 ± 2.80 µM Trolox/100 g and 1300.21 ± 65.55 µM Trolox/100 g, respectively. Moreover, these extracts were characterized by UHPLC-ESI+-Orbitrap-MS analysis finding that cyanidin (6.0 mg/kg) was the phenolic compound found in the highest amount followed by quercetin-3-glucoside (4.4 mg/kg).

Tailoring activated carbons from Pinus canariensis cones for post-combustion CO2 capture.

Activated carbons (ACs) from Pinus canariensis cones were developed by KOH chemical activation. The effect of the impregnation KOH/carbonized cones ratio (IR = 1, 2, or 3) and temperature (873, 973, 1073 K) on main chemical, textural, and morphological characteristics of the resulting ACs was systematically examined. CO2 adsorption capacity from gaseous streams was evaluated by gravimetric adsorption tests, and the analysis of breakthrough curves was determined in a packed-bed column at 303 K and atmospheric pressure. Comparison of CO2 adsorption capacities of the ACs at 273 K and 303 K at equilibrium showed that those samples developed at 973 K with IR = 3 (BET surface area ~ 1900 m2 g-1) attained the highest values (6.4 mmol g-1 and 1.9 mmol g-1, respectively), even though the ACs obtained at 1073 K with the same IR exhibited the largest surface area (2200 m2 g-1). Thermodynamic parameters evaluated from CO2 adsorption isotherms determined in the range 273-333 K for the former sample pointed to a physisorption, spontaneous, and exothermic process; isosteric heat of adsorption was also estimated for the range of surface coverage of the equilibrium isotherms. The kinetics of CO2 adsorption onto all the ACs was successfully described by the linear driving force model. The breakthrough curves were properly represented by the Thomas' model, the longest breakthrough time and highest adsorption capacity being also attained for the bed packed with the ACs developed at 973 K with IR = 3. Higher CO2 adsorption capacities of the ACs were directly related to the presence of narrow micropores (< 0.9 nm) induced by the stronger activation conditions. However, an excessively severe combination of the IR and activation temperature exerted a negative influence on CO2 adsorption onto the ACs, likely due to micropores widening.