Abstract
Brewers’ spent grain (BSG) is the main solid by-product from the brewery industry, rich in valuable nutrients and bioactive compounds. The aim of this study was to valorize this by-product, recovering phenolic compounds from BSG using ultrasound-assisted extraction (UAE) and chemometric techniques, such as the response surface methodology (RSM). Therefore, UAE process parameters (temperature and time) and solvent composition (ethanol aqueous mixtures) were optimized using a three-level Box–Behnken design, in order to carry out the maximum yield in phenols. Then, the extract obtained under optimal conditions was characterized for the total phenolic content and antioxidant capacity (2,20-azino-bis(3-ethylbenothiazoline-6-sulphonic acid, ABTS, and 2,2-diphenyl-1-picrylhydrazyl, DPPH), and individual phenolic compounds were identified using HPLC-DAD. The results show the highest level of total soluble phenolic content (4.1 ± 0.1 mg GAE/g d.w.) at 80 °C, 50 min and 65:35% ethanol:water, with a high goodness of fit between experimental and predicted values (R2 = 0.987), and a high antioxidant potential (DPPH: 0.42 ± 0.01 mg TE eq/g d.w.; ABTS: 5.82 ± 0.04 mg TE eq/g d.w.). A comparison between the classic extraction techniques and the UAE with the same solvent showed an increase of 156% in the phenol yield. The characterization of phenolic profile revealed that ferulic acid (1.5 ± 0.2 mg/L), vanillic acid (0.78 ± 0.18 mg/L) and p-coumaric acid (0.12 ± 0.03 mg/L) were the prevalent ones. UAE coupled with RSM was a useful tool to inexpensively and quickly recover bioactive phenolic compounds from BSG, which can be used in the food, pharmaceutical or cosmetic industries.
Highlights
Introduction published maps and institutional affilThe European green deal strategies aim to boost the efficient use of resources by moving to a clean, circular economy, stop environmental degradation and climate change, revert biodiversity loss and cut pollution [1]
The characterization of phenolic profile revealed that ferulic acid (1.5 ± 0.2 mg/L), vanillic acid (0.78 ± 0.18 mg/L) and p-coumaric acid (0.12 ± 0.03 mg/L) were the prevalent ones
The new challenge in the agri-food sector concerns reducing waste production or reuse through applying green technologies. In light of these considerations, the aim of this study was optimizing the ultrasound-assisted extraction (UAE) parameters, such as temperature, time and solvent composition, using the response surface methodology (RSM) technique to lead to a maximum yield in phenols
Summary
Introduction published maps and institutional affilThe European green deal strategies aim to boost the efficient use of resources by moving to a clean, circular economy, stop environmental degradation and climate change, revert biodiversity loss and cut pollution [1]. The coronavirus pandemic has only highlighted the need to accelerate the transition processes to make the economy competitive and inclusive, implementing resource efficiency pathways and providing a high standard of living with much lower environmental impacts. To address these global challenges, it is necessary to rethink and reshape the entire global economy, building an economic system based on circular economy models, with measures covering the full life cycle of products, from production and consumption to waste management and the market for secondary raw materials [2]. Industries must develop innovative processes, valorizing residual flows, obtaining new high added-value products and minimizing the disposal of their residuals in the environment [3]. iations.
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