Reintegration of Brewers Spent Grains in the Food Chain: Nutritional, Functional and Sensorial Aspects

Brewer's spent grain: Unveiling innovative applications in the food and packaging industry

Brewer's spent grain, a byproduct of beer brewing, is often discarded as waste, leading to environmental concerns. However, the growing interest in sustainability and the circular bioeconomy has prompted research into its use in food and packaging industries. The objective of this review paper is to explore recent advancements in food applications, focusing on various aspects such as processing innovations, food properties, sensory acceptability, and safety considerations. The paper highlights the role of functional bioactive compounds of BSG in food and evaluates their pharmacological activities. Additionally, it investigates the development of sustainable food-packaging materials derived from BSG, discussing their applications, challenges, and potential for eco-friendly packaging solutions. The inclusion of BSG significantly impacts the food matrix during processing, which can negatively affect the physical, rheological, and textural properties and sensory acceptability. To enhance BSGs desirability as a food ingredient, various approaches have been employed, including drying, fermentation, extrusion, and modifications using enzyme treatments, dough enhancers, and texture modifiers. BSG-derived biodegradable films and coatings demonstrate a promising potential for food-packaging applications, offering desirable properties such as sustainability and effective performance. Key challenges for adopting BSG-based solutions in food and packaging industries include limited consumer awareness, commercialization strategies, and the need for life cycle assessment and life cycle costing for successful integration and widespread adoption.

Regulation of Sugar Metabolism During Fermentation of Brewers' Spent Grain by Leuconostoc pseudomesenteroides DSM20193

Re-utilising brewers' spent grain (BSG) through LAB fermentation can enable its broad use in the food industry, enhancing its nutritional and functional properties and offering a clear example of a sustainable approach in the valorisation of food side streams. Despite extensive research on LAB fermentation, the regulation of metabolism during the growth in complex food-industry-relevant environments remains unclear. This study investigates the metabolic processes in Leuconostoc pseudomesenteroides DSM20193 during 24 h fermentation of BSG with and without 4% sucrose (w/w) supplementation, allowing in situ dextran synthesis. Besides dextran synthesis, the presence of sucrose led to faster acidification, especially due to the increased formation of acetic acid. Furthermore, differences in the utilisation of sucrose, fructose, glucose, and maltose and the formation of diverse oligosaccharides were observed. Transcriptome analysis comparing expression profiles during 0 h and 16 h growth in BSG with sucrose revealed differences in the expression of genes involved in carbohydrate utilisation pathways, including higher activity of sucrose and maltose metabolism and lower activity of metabolism related to alternative carbon sources. Transcription analysis of selected relevant genes in a time-course comparison between BSG with and without sucrose provided more detailed indications of responses of the metabolic network in this complex environment. This analysis provided a deeper understanding of the dynamic regulatory mechanism that drives sugar metabolism and dextran synthesis and how the presence of sucrose can alter the metabolic flux towards different fermentation products.

Application of a multivariate approach to the study of chemometric and sensory profiles of cookies fortified with brewers' spent grain

This work was aimed to investigate the effects of three factors on cookie quality: brewers' spent grain (BSG) composition [65% malted barley and 35% of unmalted durum (DA) or soft (RI), or emmer (EM) wheats]; geographical origin of the cereals used in brewing (Daunia or Salento); and percentages of BSG in cookie formulation (30 or 40%). A control made of 100% Manitoba flour was produced. Statistical analyses were performed to evaluate the effects of those factors (Analysis of Variance), the possibility to distinguish the various types of cookies (Principal Component Analysis), and the relationships among variables (Pearson Correlation Analysis).The single and interactive effects of the three factors were significant for almost all variables. Cookies with 40% EM spent grains showed the highest ash, dietary fibre, and total phenolic contents but cookies with 30% DA or RI spent grains received the highest overall quality scores due to the higher intensity of their fresh baked flavour and their lower hardness and fibrousness. Based on the nutritional and sensory characteristics, cookies fortified with RI and DA were the best to consume. Although few physicochemical differences can be attributed to geographical origin, a slightly higher overall sensory score was assigned to those produced with Salento cereals. Principal Component Analysis showed a clear separation between the control made of 100% Manitoba flour and the group of fortified cookies. Among the latter, the cookies produced with RI and DA spent grains were indistinguishable from each other due to their similar quality characteristics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-024-06064-3.

Assessing the Potential of Brewer's Spent Grain to Enhance Cookie Physicochemical and Nutritional Profiles

Brewers' spent grain (BSG), the major by-product of the brewery industry, has high nutritional value, making it suitable for upcycling into products such as healthy, and sustainable cookies. Nonetheless, the incorporation of BSG in cookies can impact their quality, given the increased fiber and protein content. This work explored the effect of replacing wheat flour with BSG at 50% and 75% in cookie formulations, focusing on physical, chemical, and sensory properties. The dietary fiber, lipid, and protein content of cookies improved considerably with the highest incorporation of BSG, increasing from 6.37% to 15.54%, 9.95% to 13.06%, and 9.59% to 12.29%, respectively. Conversely, moisture and water activity decreased from 11.03% to 3.37% and 0.742 to 0.506, respectively, forecasting a lower risk of microbial contamination and increased shelf-life. The incorporation of BSG in cookies resulted in decreased brightness and increased hardness, from 40 N to 97 N. Moreover, colorimetric shifts among the control cookies and the two BSG-rich formulations could be easily identified by an untrained observer. Sensory evaluation showed that cookies with 50% BSG retained acceptable sensory characteristics, suggesting potential for further development. Overall, BSG enhances the nutritional profile of cookies with no excessive detrimental impact on sensory features.

Microbial alchemy: upcycling of brewery spent grains into high-value products through fermentation

Spent grains are one of the lignocellulosic biomasses available in abundance, discarded by breweries as waste. The brewing process generates around 25-30% of waste in different forms and spent grains alone account for 80-85% of that waste, resulting in a significant global waste volume. Despite containing essential nutrients, i.e., carbohydrates, fibers, proteins, fatty acids, lipids, minerals, and vitamins, efficient and economically viable valorization of these grains is lacking. Microbial fermentation enables the valorization of spent grain biomass into numerous commercially valuable products used in energy, food, healthcare, and biomaterials. However, the process still needs more investigation to overcome challenges, such as transportation, cost-effective pretreatment, and fermentation strategy. to lower the product cost and to achieve market feasibility and customer affordability. This review summarizes the potential of spent grains valorization via microbial fermentation and associated challenges.

Non-Conventional Brewers' Spent Grains, an Alternative Raw Material in Bread-Making

The main objective of this experiment was to investigate the technological potential of upcycling unsparged non-conventional brewers' spent grains (BSGs) in bread-making and assess the comparative quality of bread enriched with non-fermented and lactic acid-fermented BSGs obtained from mashes brewed with starch adjuncts of buckwheat and oats. After the runoff of the first wort, unsparged non-conventional BSGs with approximately 75% moisture, acidic pH, and yield in the soluble extract above 56.6% (w/w d.m.) were used in substituting wheat flour with 5 and 15% (w/w d.m.) in bread-making recipes. The highest loaf volume value (318.68 cm3/100 g) was observed for 5% fermented buckwheat-BSG addition. Except for the samples with 5% fermented BSGs, specific volumes decreased. Crumb moisture was reduced by up to 22% for all samples, with this parameter related to bread weight. Bread porosity, elasticity, acidity, and overall sensory acceptability were better for fermented than non-fermented BSGs. The results proved that non-conventional BSGs with buckwheat and oats addition have the potential to be valorized in new bread assortments, and lactic acid fermentation applied to the BSGs is beneficial, even for overall sensory acceptability and quality of baked end-products. Technological, buckwheat-BSG was more convenient than oats-BSG. Further research continues to optimize and upscale Technology Readiness Levels.

Utilizing Food Waste in 3D-Printed PLA Formulations to Achieve Sustainable and Customizable Controlled Delivery Systems

This is the first study that explores blending polylactic acid (PLA) with various biomasses, including food wastes-brewer's spent grain (BSG), spent coffee grounds (SCG), sesame cake (SC), and thermoplastic starch (TPS) biomass to create composite gastric floating drug delivery systems (GFDDS) through 3D printing. The aim is to investigate the influence of biomass percentage, biomass type, and printing parameters on their corresponding drug release profiles. 3D-printed (3DP) composite filaments were prepared by blending biomasses and PLA before in vitro drug release studies were performed using hydrophilic and hydrophobic model drugs, metoprolol tartrate (MT), and risperidone (RIS). The data revealed that release profiles were influenced by composite compositions and wall thicknesses of 3DP GFDDS capsules. Up to 15% of food waste could be blended with PLA for all food waste types tested. Delivery studies for PLA-food wastes found that MT was fully released by 4 h, exhibiting burst release profiles after a lag time of 0.5 to 1.5 h, and RIS could achieve a sustained release profile of approximately 48 h. PLA-TPS was utilized as a comparison and demonstrated variable release profiles ranging from 8 to 120 h, depending on the TPS content. The results demonstrated the potential for adjusting drug release profiles by incorporating affordable biomasses into GFDDS. This study presents a promising direction for creating delivery systems that are sustainable, customizable, and cost-effective, utilizing sustainable materials that can also be employed for agricultural, nutraceutical, personal care, and wastewater treatment applications.

Fostering Circular Economy: Brewing By-Products as Innovative Ingredients for Cereal Bar Formulation

Brewer's spent grain (BSG) was used as a sustainable and healthy ingredient in two cereal bar formulations, with honey (H) and chocolate (C) used as the binding systems' characterizing ingredients. The two bars, formulated using three levels of BSG (H1: 8.5%; H2: 12.7%; H3: 21.2%; C1: 3.9%; C2: 7.7%; C3: 15.5%) and stored for 20 days, were studied from a physicochemical perspective and compared to non-enriched control bars. The analysis showed that BSG enriched the bars with minerals, B vitamins, proteins, and fibers, meeting the required contents for the "high fiber" nutritional claim. Moisture content and water activity decreased with increasing BSG quantity and storage time. Higher BSG content increased flexibility in H bars after 7 days, while decreasing water content and increasing hardness in C bars at 1 storage day. Higher BSG levels darkened the samples' color with little change during storage. In addition, a consumer sensory test was conducted. The results showed that providing information on BSG had little impact on liking, purchase intent, and sensory perception. In addition, under blind conditions, H bars were considered more natural and healthier than the C bars; however, these differences were not significant in the informed conditions. This study shows the potential use of upcycled ingredients in cereal bars and highlights the central role of the sensory experience on consumer appreciation, considering also information provision.

Evaluation of Proximate Composition, Physicochemical Properties, and Sensory Attributes of Instant Flour from Brewery Spent Grain, by Blending with Maize (Zea mays L.) and Germinated Chickpea (Cicer arietinum L.)

Brewer's spent grain (BSG) is a nutritional-rich by-product of the brewing industry used in different food product development processes. "Corn Soya Blend" (CSB) is prepared from heat-treated maize and soybeans according to the specifications set by the World Food Program (WFP). Three instant formulations-IF20 (70% maize, 10% chickpea, and 20% BSG), IF15 (70% maize, 15% chickpea, and 15% BSG), and IF10 (70% maize, 20% chickpea, and 10% BSG)-were developed in this research. Proximate composition, functional properties, and antinutritional factors were analysed. The sensory quality of porridge samples developed from the instant flour was evaluated using a consumer-oriented panel (food science and technology students) at a five-point hedonic scale. Accordingly, moisture, crude fibre, crude protein, total ash, and crude fat contents increased significantly (p < 0.05) as a result of BSG ratio inclusion. Bulk density decreased significantly (p < 0.05) while the BSG proportion increased but water absorption capacity increased when the proportion of BSG increased. Phytate and tannin contents were also increased while the BSG proportion increased. However, an increase in germinated chickpea proportion significantly (p < 0.05) decreased phytate and tannin contents. While BSG increased, the overall acceptability of porridge samples decreased, with the exception of mouthfeel. According to this study, up to 15% of BSG, 70% maize, and 15% chickpea could be used for instant flour preparation which has a comparable sensory characteristic with the commercial CSB. Hence, it can be used as a substitute for corn-soya mix.

Study on the Effect of Microwaved Brewer's Spent Grains on the Quality and Flavor Characteristics of Bread

To enable a wider utilization of co-products from beer processing and minimize the negative effect of added grain on bread quality, flavor, and other attributes, brewer's spent grains (BSG) are processed through microwave pretreatment, and then the microwave-treated BSG (MW-BSG) is added to bread. So far, there has been no investigation on the effect of microwave-pretreated BSG on bread quality and flavor. In this study, we examined the effects of diverse microwave treatment variables on the physicochemical structure of BSG and explored the consequences of MW-BSG on the quality and flavor of bread. The results showed that soluble dietary fiber and water-soluble protein levels in MW-BSG increased significantly (144.88% and 23.35%) at a 540 W microwave power, 3 min processing time, and 1:5 material-liquid ratio of BSG to water. The proper addition of MW-BSG positively affected the bread texture properties and color, but excessive amounts led to an irregular size and distribution of the bread crumbs. The result of electronic nose and HS-SPME-GC-MS analyses showed that the addition of MW-BSG modified the odor profile of the bread. A sensory evaluation showed mean scores ranging from 6.81 to 4.41 for bread containing 0-10% MW-BSG. Consumers found a maximum level of 6% MW-BSG acceptable. This study endeavors to decrease environmental contamination caused by brewing waste by broadening the methods by which beer co-products can be utilized through an innovative approach.

The Rheology and Textural Properties of Bakery Products Upcycling Brewers' Spent Grain

This study aimed to evaluate the rheological properties of doughs with 50% brewers' spent grain (BSG) derived from a rye-based (RBSG) and barley-based (BBSG) beer added, and the textural profile of the related baked products. Simple model systems using BSG flour mixed with water were studied. Two bakery products, focaccia and cookies, were made as food systems using BSG in a 1:1 ratio with wheat flour (WF). Their rheological properties and texture after baking were characterized. BSG-added dough exhibited viscoelastic properties with a solid gel-like behavior. The addition of BSG increased G' > G″ and decreased the dough flexibility. BSG addition in baked RBSG focaccia increased the hardness, gumminess, and chewiness by 10%, 9%, and 12%, respectively. BBSG cookies had a 20% increase in fracturability. A positive correlation was found between the rheological metrics of the dough and the textural parameters of BBSG-added cookies. PCA analysis revealed that complex viscosity, G', G″, and cohesiveness separated BBSG focaccia from RBSG focaccia and the control. Therefore, the rheological properties of BSG dough will have industrial relevance for 3D-printed customized food products with fiber. Adding RBSG and BBSG to selected foods will increase the up-cycling potential by combining techno-functional properties.

Extraction, Composition, Functionality, and Utilization of Brewer’s Spent Grain Protein in Food Formulations

In recent years, brewer’s spent grain (BSG) has gained attention as a plant-based protein source because it occurs in large quantities as a by-product of beer brewing. BSG can contribute to future food requirements and support the development of a circular economy. In light of the dynamic developments in this area, this review aims to understand the proteins present in BSG, and the effect of extraction techniques and conditions on the composition, physicochemical, and techno-functional properties of the obtained protein extracts. The water-insoluble hordeins and glutelins form the major protein fractions in BSG. Depending on the beer brewing process, the extraction technique, and conditions, the BSG protein isolates predominantly contain B, C, and ϒ hordeins, and exhibit a broad molecular weight distribution ranging between <5 kDa and >250 kDa. While the BSG isolates obtained through chemical extraction methods seem promising to obtain gelled food products, physical and enzymatic modifications of BSG proteins through ultrasound and proteolytic hydrolysis offer an effective way to produce soluble and functional protein isolates with good emulsifying and foaming capabilities. Specifically tailored protein extracts to suit different applications can thus be obtained from BSG, highlighting that it is a highly valuable protein source.

Functional Bread Produced in a Circular Economy Perspective: The Use of Brewers' Spent Grain

Brewers' spent grain (BSG) is the main by-product of the brewing industry, corresponding to ~85% of its solid residues. The attention of food technologists towards BSG is due to its content in nutraceutical compounds and its suitability to be dried, ground, and used for bakery products. This work was aimed to investigate the use of BSG as a functional ingredient in bread-making. BSGs were characterised for formulation (three mixtures of malted barley and unmalted durum (Da), soft (Ri), or emmer (Em) wheats) and origin (two cereal cultivation places). The breads enriched with two different percentages of each BSG flour and gluten were analysed to evaluate the effects of replacements on their overall quality and functional characteristics. Principal Component Analysis homogeneously grouped BSGs by type and origin and breads into three sets: the control bread, with high values of crumb development, a specific volume, a minimum and maximum height, and cohesiveness; Em breads, with high values of IDF, TPC, crispiness, porosity, fibrousness, and wheat smell; and the group of Ri and Da breads, which have high values of overall smell intensity, toasty smell, pore size, crust thickness, overall quality, a darker crumb colour, and intermediate TPC. Based on these results, Em breads had the highest concentrations of nutraceuticals but the lowest overall quality. Ri and Da breads were the best choice (intermediate phenolic and fibre contents and overall quality comparable to that of control bread). Practical applications: the transformation of breweries into biorefineries capable of turning BSG into high-value, low-perishable ingredients; the extensive use of BSGs to increase the production of food commodities; and the study of food formulations marketable with health claims.

Food industry waste - An opportunity for black soldier fly larvae protein production in Tanzania

Black soldier fly larvae composting is an emerging treatment option with potential to improve biowaste valorization in cities of low-income countries. This study surveyed the current generation and management status of food industry biowaste and their availability and suitability as potential feedstock for black soldier fly larvae (BSFL) composting treatment in three Tanzania cities, Dar es Salaam, Mwanza, and Dodoma. Biowaste-generating food industry companies (n = 29) in the three cities were found to produce banana peels, mango seeds, sunflower press cake, brewery waste, and coffee husks in large quantities (~100,000-1,000,000 kg y^-1). Around 50 % of these companies (16/29), primarily vegetable oil companies (10/11), either sold or gave away their waste as animal feed, while most companies (9/11) with unutilized food industry waste landfilled the generated biowaste. Multi-criteria analysis based on substrate availability criteria identified banana peels, mango seeds, and coffee husks with total score points of ≥10/12 as the most suitable feedstock for BSFL composting. However, multi-criteria analysis based on physical-chemical criteria identified brewery waste and sunflower press cake with total score points of ≥11/15 as the most suitable feedstock. Combined availability and physical-chemical properties of individual biowastes showed that all identified types of food industry biowaste can be suitable feedstock for producing BSFL biomass for protein production, but certain waste streams needed to be mixed with other waste streams prior to BSFL-composting to ensure sufficient availability and provide a balanced nutritional profile compared with the single-source biowastes. This study concluded that large volumes of food industry waste are being generated from food industry companies in Tanzania and there is need to establish new biowaste management interventions for resource recovery. Furthermore, for interested stakeholders in the waste management business, multi-stream BSFL-composting can be a suitable solution for managing and closing nutrient loops of the unutilized food industry biowaste in Tanzania and in other similar settings globally.

Hybrid Sausages: Modelling the Effect of Partial Meat Replacement with Broccoli, Upcycled Brewer's Spent Grain and Insect Flours

The social, environmental and health concerns associated with the massive consumption of meat products has resulted in calls for a reduction in meat consumption. A simplex lattice design was used for studying the effect of combining broccoli, upcycled brewer’s spent grain (BSG) and insect flours from Tenebrio molitor (IF) as alternative sources of protein and micronutrients, in hybrid sausages formulation. The techno-functional properties of the ingredients and the nutritional and textural properties of nine hybrid sausages were analysed. The effect of adding these ingredients (constituting 35% of a turkey-based sausage) on protein, fat, fibre, iron and zinc content, and textural properties (Texture Profile Analysis (TPA) and Warner−Bratzler parameters) were modelled employing linear regression (0.72 < R2 < 1). The “desirability” function was used for multi-response optimisation of the samples for the highest protein content, optimum chewiness and a* value (closeness to red). The analysis of sensory data for the three optimised samples showed no significant differences in juiciness and odour between the hybrid meat sausage with 22% broccoli, 3% BSG, and 10% IF and the commercial Bratwurst sausage elaborated exclusively with animal protein. Colour, appearance, chewiness and pastiness were rated higher than for the reference. The instrumental chewiness highly correlated with sensorial chewiness (R2 = 0.98). Thus, a strategy introducing less refined and more sustainable sources of protein and micronutrients was successfully employed to model and statistically optimise a meat product formulation with reduced animal protein content.

In Vitro Digestibility of Minerals and B Group Vitamins from Different Brewers' Spent Grains

Brewers' spent grain (BSG), the main by-product of the brewing industry, is a rich source of minerals and water-soluble vitamins such as thiamine, pyridoxine, niacin, and cobalamin. Bioaccessibility through in vitro digestion is an important step toward the complete absorption of minerals and B group vitamins in the gastrointestinal system. Inductively coupled plasma optical emission spectrometry (ICP-OES) together with inductively coupled plasma quadrupole mass spectrometry (ICP-MS) was used for the quantification of the macro- and micro-minerals. An ultra-high performance liquid chromatography (UHPLC) system coupled with a diode array detector (DAD) was used for B group vitamin identification. Four different industrial BSG samples were used in the present study, with different percentages of malted cereals such as barley, wheat, and degermed corn. Calcium's bioaccessibility was higher in the BSG4 sample composed of 50% malted barley and 50% malted wheat (16.03%), while iron presented the highest bioaccessibility value in the BSG2 sample (30.03%) composed of 65% Pale Ale malt and 35% Vienna malt. On the other hand, vitamin B1 had the highest bioaccessibility value (72.45%) in the BSG3 sample, whilst B6 registered the lowest bioaccessibility value (16.47%) in the BSG2 sample. Therefore, measuring the bioaccessibilty of bioactive BSG compounds before their further use is crucial in assessing their bioavailability.

Cereal Waste Valorization through Conventional and Current Extraction Techniques-An Up-to-Date Overview

Nowadays, in the European Union more than 100 million tons of food are wasted, meanwhile, millions of people are starving. Food waste represents a serious and ever-growing issue which has gained researchers’ attention due to its economic, environmental, social, and ethical implications. The Sustainable Development Goal has as its main objective the reduction of food waste through several approaches such as the re-use of agro-industrial by-products and their exploitation through complete valorization of their bioactive compounds. The extraction of the bioactive compounds through conventional methods has been used for a long time, whilst the increasing demand and evolution for using more sustainable extraction techniques has led to the development of new, ecologically friendly, and high-efficiency technologies. Enzymatic and ultrasound-assisted extractions, microwave-assisted extraction, membrane fractionation, and pressure-based extraction techniques (supercritical fluid extraction, subcritical water extraction, and steam explosion) are the main debated green technologies in the present paper. This review aims to provide a critical and comprehensive overview of the well-known conventional extraction methods and the advanced novel treatments and extraction techniques applied to release the bioactive compounds from cereal waste and by-products.

The Potential of Brewer’s Spent Grain in the Circular Bioeconomy: State of the Art and Future Perspectives

Brewer’s spent grain (BSG) accounts for approximately 85% of the total mass of solid by-products in the brewing industry and represents an important secondary raw material of future biorefineries. Currently, the main application of BSG is limited to the feed and food industry. There is a strong need to develop sustainable pretreatment and fractionation processes to obtain BSG hydrolysates that enable efficient biotransformation into biofuels, biomaterials, or biochemicals. This paper aims to provide a comprehensive insight into the availability of BSG, chemical properties, and current and potential applications juxtaposed with the existing and emerging markets of the pyramid of bio-based products in the context of sustainable and circular bioeconomy. An economic evaluation of BSG for the production of highly valuable products is presented in the context of sustainable and circular bioeconomy targeting the market of Central and Eastern European countries (BIOEAST region).

Analysis of Fatty Acids, Amino Acids and Volatile Profile of Apple By-Products by Gas Chromatography-Mass Spectrometry

Apple industrial by-products are a promising source of bioactive compounds with direct implications on human health. The main goal of the present work was to characterize the Jonathan and Golden Delicious by-products from their fatty acid, amino acid, and volatile aroma compounds’ point of view. GC-MS (gas chromatography-mass spectrometry) and ITEX/GC-MS methods were used for the by-products characterization. Linoleic and oleic were the main fatty acids identified in all samples, while palmitic and stearic acid were the representant of saturated ones. With respect to amino acids, from the essential group, isoleucine was the majority compound identified in JS (Jonathan skin) and GS (Golden skin) samples, lysine was the representant of JP (Jonathan pomace), and valine was mainly identified in GP (Golden pomace). A total number of 47 aroma volatile compounds were quantified in all samples, from which the esters groups ranged from 41.55–53.29%, aldehydes 29.75–43.99%, alcohols from 4.15 to 6.37%, ketones 4.14–5.72%, and the terpenes and terpenoids group reached values between 2.27% and 4.61%. Moreover, the by-products were valorized in biscuits manufacturing, highlighting their importance in enhancing the volatile aroma compounds, color, and sensorial analysis of the final baked goods.

Optimization of Phenolic Compound Extraction from Brewers’ Spent Grain Using Ultrasound Technologies Coupled with Response Surface Methodology

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.