Conditioning and characterization of craft Pilsen brewers´ spent grain (BSG)

PALENCIA, MANUEL A; CONSTENLA, DIANA; PEREZ , ETHEL

Buenos AIres

Congreso; 11th World Congress of Chemical Engineering; 2023

Asociación Argentina de Ingenieros Químicos

Spent grain is the most abundant by-product of the brewing process, corresponding to about 85 % of the total by-products, and it accounts for (in average). For every 10 L of brewed beer, approximately 2 kg of BSG are obtained [1]. Based on the global beer production quantities, about 40 million tons of BSG would be available worldwide by 2025. The major limitation to using spent grains is its high moisture content, with values between 75 and 90%, which makes it an unstable material and susceptible to microbial spoilage. This characteristic is a major restriction on the BSG use for consumption in the food industry. Nowadays, the use of BSG is promoted for animal feed production or for composting in landfills, although in the long term the latter could cause environmental pollution due to its chemical composition [2]. The present work provides information considered of interest from a scientific and an industrial point of view, to determine conditioning by analyzing the drying, sorption isotherm and composition. Two types of brewers´ spent grain (BSG), Pilsen and Weisner, were collected from a craft brewery located in Bahia Blanca (Argentina). Initial moisture was previously analyzed, resulting in an average of 72.5%, approximately and was characterized proximally (moisture, ash, lipids and proteins). The Pilsen BSG sample was divided into two test portions, ones was performed successive water washes until the concentration of soluble solids (°Brix) in the wash water dropped to zero. Drying assays were carried out on washed Pilsen, unwashed Pilsen and unwashed Weisen samples at 40 and 50°C by means a natural convective dryer. To obtain the water sorption isotherm, water activities of the samples conditioned at different moisture content were measured at room temperature using a thermohygrometer Testo 650 (Testo AG, GermanyThe) and moisture content was determined by means of OHAUS (MB 45) infrared analytical balance (105 °C). All assays were carried out by three replicates to estimate the inherent variability of the determination. Three empirical models are used for the mathematic modeling (Newton, Henderson-Pabis & Page). According to the statistical analyses used (R2, SSE, RMSE and 2), the Page model shows the best fit quality on all experimental data. Desorption curves were also made under the same conditions, the monolayer values (GAB) were determined. Monolayer value predicted obtained for washed Pilsen, unwashed Pilsen and unwashed Weisner samples from the GAB equation, were 1.9, 4.1 and 0.48 g water/100 g dry BSG, respectively. The concentrations of the proximal components agree with literature. Statistical method was used in order to compare of non-linear model fitting parameters representing of the drying. In order to find differences among the different spent grain lots and among those preserved by the temperature, and to establish relationships between determinations.