Potential Uses of Spent Coffee Grounds in the Food Industry

Lignin from Plant-Based Agro-Industrial Biowastes: From Extraction to Sustainable Applications

Lignin, the most abundant aromatic polymer in nature, plays a critical role in lignocellulosic biomasses by providing structural support. However, its presence complicates the industrial exploitation of these materials for biofuels, paper production and other high-value compounds. Annually, the industrial extraction of lignin reaches an estimated 225 million tons, yet only a fraction is recovered for reuse, with most incinerated as low-value fuel. The growing interest in lignin potential has sparked research into sustainable recovery methods from lignocellulosic agro-industrial wastes. This review examines the chemical, physical and physicochemical processes for isolating lignin, focusing on innovative, sustainable technologies that align with the principles of a circular economy. Key challenges include lignin structural complexity and heterogeneity, which hinder its efficient extraction and application. Nonetheless, its properties such as high thermal stability, biodegradability and abundant carbon content place lignin as a promising material for diverse industrial applications, including chemical synthesis and energy generation. A structured analysis of advancements in lignin extraction, characterization and valorization offers insights into transforming this undervalued by-product into a vital resource, reducing reliance on non-renewable materials while addressing environmental sustainability.

Spent Coffee Grounds as a Source of Chlorogenic Acid

Spent coffee grounds generated from the brewing of coffee cherries are rich in chlorogenic acids that are associated, to a certain extent, with a delay in the development of various chronic diseases and age-related disorders. These natural antioxidants are applied in the pharmaceutical, cosmetic, and food industries. This brief overview describes recently proposed procedures for the extraction and recovery of chlorogenic acids from spent coffee grounds, which is a low-cost and easily accessible by-product. Solvent selection and temperature control seem to be the main factors due to the thermolabile nature of these compounds. Advanced extraction technologies are generally faster and enhance extraction efficiency. Procedures for the valorization of coffee waste are the goal of a sustainable and circular bioeconomy that seeks to increase their added benefits and reduce environmental pollution.

The Antimicrobial Effects of Coffee and By-Products and Their Potential Applications in Healthcare and Agricultural Sectors: A State-of-Art Review

Coffee is one of the most consumed beverages around the world. Its production is dominated by the species Coffea arabica and Coffea canephora. However, the coffee elaboration process leads to generating a significant amount of waste, which arises in various stages of coffee bean processing and is rich in natural bioactive compounds such as phenolic compounds and alkaloids. Particularly, chlorogenic and caffeic acids have a high antimicrobial potential and have been demonstrated to be effective against bacteria and viruses of healthcare and food relevance, including multi-resistant pathogens. However, the production and accumulation of coffee waste have a negative environmental impact since they can contaminate the surrounding environment due to the presence of organic molecules such as caffeine and tannins. In this context, exploiting natural resources as a source of compounds with the antimicrobial potential of, for example, the bioactive compounds obtained from coffee, has been evaluated in previous works. This review aims to summarize the current knowledge on the antimicrobial properties of coffee and its by-products and their potential application in the healthcare sector and disease control in agricultural crops, with particular emphasis on improving sustainability and efficiency in agriculture through making use of waste, which carries high importance in today's society.

TEMPO-oxidized cellulose fiber from spent coffee ground: Studying their properties as a function of particle size

The applicability of cellulose and its derivatives is greatly depends on their attributes such as aspect ratio, morphology, surface chemistry, crystallinity, as well as their thermal and mechanical properties. However, these attributes can alter according to the utilized raw material, size classifications, extraction techniques, or fibrillation methods. Among these, the effect of raw material particle size on cellulose properties has received limited attention in scientific studies. Therefore, this study aimed to investigate the effect of different particle sizes of spent coffee grounds (SCG) (A: 850-1400 μm, B: 500-850 μm, C: 355-500 μm) on the physicochemical properties of TEMPO-oxidized cellulose (TOC). The freez-dried TOC was characterized in terms of functional groups, morphology, width diameter, crystallinity, carboxyl content, charge density, thermal properties, and re-dispersibility in water. Successful oxidation in all samples was confirmed by the presence of a sodium carboxylate peak in the FTIR spectrum. Higher thermal resistance, carboxyl content, as well as improved physical stability of the re-dispersed suspension were observed in A-TOC sample. Unlike B and C-TOC, A-TOC was favored sample for obtaining fibrillated cellulose with crystallinity of 49.92 %. In contrast, production process significantly damaged the crystalline regions in finer particles and reduced the crystallinity of B and C-TOC to values ranging from 35 to 37 %. In conclusion, finer SCG particles were highly sensitive to reaction conditions and showed high tendency toward dissolution, which make them unsuitable candidates for fiber fabrication. In terms of SCG, only coarse particles (A: 850-1400 μm) were found to be ideal for producing oxidized cellulose fibers.

Coffee Silverskin as a Potential Ingredient for Functional Foods: Recent Advances and a Case Study with Chocolate Cake

Coffee silverskin (CS) is a by-product of the coffee roasting process that is known for its potential as a fiber source with antioxidant properties. Therefore, this study aimed to provide an overview of the latest research on CS as a potential ingredient for functional foods and to evaluate the effect of adding different amounts of CS on the functional and sensory attributes of chocolate cakes. The addition of CS increased the total dietary fiber content, antioxidant capacity and the contents of extractable and non-extractable phenolics in the cakes. The evaluated sensory attributes were color, smell, taste, texture and overall impression, and they were evaluated according to a 9-point hedonic scale. Internal preference maps were obtained based on the results from acceptance and "intention to buy" tests. In general, the cakes with lower coffee silverskin content (2.6% and 3.6%) had a similar level of acceptance and the cake with 4.6% coffee silverskin content was the least accepted. The most important attributes were taste and overall impression, corresponding to "like slightly" and "like moderately" for the cakes that had better acceptance. Nonetheless, even with the lowest amount of added CS (2.6%), the produced cakes could be regarded as antioxidant fiber sources (with fiber content above 3 g/100 g), thus confirming the potential of CS as a functional food additive.

Conilon coffee: A critical review and bibliometric analysis for the agri-food industry

This study includes a bibliometric analysis and literature review on Conilon coffee and its relevant aspects for the food industry, focusing on its chemical constituents, the application of fermentation as a processing method, and the reuse of waste generated during processing. Relevant articles were selected through a bibliometric analysis of titles indexed in the Web of Science (WoS) and Google Scholar databases. Conilon coffee cultivation, especially in the Brazilian states of Espírito Santo, Rondônia and Bahia, has played a growing role in the global economy, with research focused on strategies to increase productivity, reduce costs and improve nutritional and bioactive quality. The use of agricultural waste as substrates for seedlings and genetic manipulation to develop clonal cultivars are showing promise, although some options may increase the heavy metal content in plants. This review enabled the identification of the main chemical constituents of Conilon coffee and an assessment of their contributions to the product's sensory attributes and bioactive properties. It was clear that the choice of fermentation conditions changes the sensory characterization of coffee, potentially benefiting the overall rating of the beverage. This review also suggests that Conilon coffee residues contain volatile compounds of considerable commercial value, so they should be subjected to extraction methods and subsequently preserved. Acid hydrolysis and microencapsulation can be alternatives for extracting and preserving compounds of interest from Conilon coffee. This work contributes to deepening knowledge about the challenges faced by Conilon coffee and the search for alternatives to increase its market value.

Quality Properties of Bakery Products and Pasta Containing Spent Coffee Grounds (SCGs): A Review

Coffee is one of the most consumed and popular beverages worldwide, and it produces a significant quantity of waste. Spent coffee grounds (SCGs) are one of the major waste products that can be used as an ingredient for creating novel foods. Therefore, the effect of incorporating varying percentages of spent coffee grounds (SCGs) on the quality properties of bakery products and pasta is reviewed. Chemically, SCGs alter protein, fat, fiber, ash, and bioactive compound levels in bakery and pasta products, improving nutritional value and promoting health benefits. The impact of SCGs on the physical characteristics of baked goods depends on factors like SCG concentration and processing methods, which influence product texture and structure. Sensory properties are vital for consumer acceptance. SCGs can add unique flavors and colors to baked goods, but more attention is needed to optimize the SCGs' incorporation concentration for a better consumer appeal. In conclusion, integrating SCGs into bakery products and pasta offers nutritional enhancement, sustainability, and sensory improvement opportunities. Optimizing product quality allows manufacturers to leverage SCGs' potential in the food industry.

Sustainable Valorisation of Coffee Waste as a Protein Source, Mycelium-Based Packaging Material and Renewable Energy Pellet

This study investigates the valorization of spent coffee grounds (SCGs) through protein extraction and their application in mycelium-based packaging and renewable energy pellets. Three extraction methods-mechanical stirring, ultrasound-assisted, and CO2-assisted extraction-were applied to SCGs. CO2-assisted extraction yielded the highest protein content at 34.24%, followed by mechanical stirring (31.46%) and ultrasound-assisted extraction (28.51%). The total polyphenol content and antioxidant capacity were also highest in the CO2 extracts, suggesting that this method preserves bioactive compounds most effectively. After protein extraction, SCGs were tested as a component in mycelium-based packaging, with results showing an apparent density of 0.551 g/cm3 and compression resistance of 3.354 MPa, indicating its suitability for structural applications. The energy value of SCGs remained high, with a calorific value of 19,887 J/g DW, slightly decreasing after extraction but still sufficient for renewable energy production. These findings highlight the potential of SCGs as a multi-functional resource, contributing to sustainable solutions across various industries.

Inhibition of α-glucosidase activity by potential peptides derived from fermented spent coffee grounds

The control of α-glucosidase activity has been associated with managing diabetes. We previously identified three peptides with high bioactive indices derived from protein hydrolysates of fermented spent coffee grounds. In this study, the peptides YGF, GMCC, and RMYRY were synthesized and tested in vitro for their α-glucosidase inhibition activity, complemented by in silico analyses. Two of the three peptides significantly inhibited α-glucosidase activity, with the more efficient peptides being YGF and GMCC (0.42 mg/mL), resulting in decreased enzymatic activity of 95.31% and 89.79%, respectively. These peptides exhibited binding free energies with the α-glucosidase complex of -8.5 and - 6.6 kcal/mol, respectively, through hydrogen bonds and van der Waals interactions with amino acids from the active site. Pharmacokinetic analysis indicated that YGF and GMCC profiles were unrelated to toxicity. These results underscore the importance of focusing on food waste bioprocessing products to expand the range of alternatives that could aid in diabetes treatment.

Adsorption parameters optimization of spent coffee ground biochar for methylene blue removal using response surface methodology

This study investigates the potential of spent coffee ground biochar (SCGB) as a sustainable and cost-effective adsorbent for the removal of methylene blue (MB), a hazardous dye commonly used in the textile and printing industries. A response surface methodology (RSM) approach with central composite design (CCD) was employed to systematically investigate the effects of key process parameters, including adsorbent dosage, solution pH, contact time and temperature, on MB removal efficiency. The analysis revealed that adsorbent dosage and temperature as critical factors influencing MB removal, with a linear model providing a strong correlation. Optimal conditions for MB removal were determined to be 0.99 g of SCGB, 30 min of contact time, 30 °C temperature, and a solution pH of 7. Under these conditions, MB removal reached 99.99%, with a desirability of 1.000. The experimental results closely matched the predicted values, differing by only 0.02%, thus validating the accuracy of the model. Kinetic studies indicated a rapid adsorption process, well-described by both pseudo-first and pseudo-second order models. Isotherm analysis confirmed the applicability of the Freundlich model, suggesting favorable adsorption with increasing MB concentration. The high adsorption capacity of SCGB is attributed to its carbonaceous and porous structure, highlighting its potential as an effective adsorbent for dye removal in wastewater treatment applications.

Bioactive Compounds from Organic Waste

The reuse and reincorporation of waste are the principles of circular economies. Compost, biofuels, animal feed, dyes, and bioactive compounds can be obtained from the revaluation of organic waste. Research on this subject is scarce and limited to specific sectors, such as agriculture and agroindustry, leaving aside others that generate large quantities of organic waste, such as floriculture. The remains of these sectors have a low decomposition rate compared to other organic wastes. They are a source of bioactive compounds (e.g., essential oils, pigments, phenols) that can be reincorporated into the production chain of various industries. This review describes the composition of waste from agroindustry, agriculture, and floriculture, analyzing their potential revalorization as a source of bioactive compounds and an alternative supply source.

Exploring the Nutritional Potential of Spent Coffee Grounds as a Substitute for Rice Bran in Feeds for Nile tilapia, Oreochromis niloticus: An Evaluation of Growth Performance and Biological Indices

This study aimed to assess the viability of replacing rice bran with spent coffee grounds (SCG) in the diets of Oreochromis niloticus (average body weight, 48.8 ± 0.42 g). The fish were randomly allocated into four sets of three groups each and placed in net cages (1 m × 2 m × 0.5 m) at a density of 30 fish per cage. They were fed diets with four different replacement levels: 0%, 5%, 10%, and 15% of SCG over a period of 90 days. Growth and serum biochemical indices were monitored three times at 30, 60, and 90 days. During the experiment, there were no significant differences (P  > 0.05) observed in growth indices, including weight gain (WG), daily WG, specific growth rate, feed conversion rate, protein efficiency ratio, and survival rate among the groups at 30, 60, and 90 days. Serum biochemical indices, such as aspartate aminotransferase and alanine aminotransferase, showed a similar trend with significant differences observed only on day 30, while the lowest and highest levels were found in the control and 15% SCG replacement groups, respectively. For total cholesterol, a significantly different result was found only on day 30. However, these differences were not sustained in subsequent assessments. Conversely, serum glucose, total protein, albumin, and globulin remained unaffected by SCG replacement throughout the experiment. The findings indicate that replacing rice bran with up to 15% SCG did not adversely impact the growth performance or key serum biochemical indices of Nile tilapia. To the researchers' knowledge, these findings are the first in the field to substitute SCG for rice bran, opening a new avenue for further research.

Exploiting Agri-Food Waste as Feed for Tenebrio molitor Larvae Rearing: A Review

The agri-food industry generates substantial amounts of waste, including by-products and residues. The increasing demand for sustainable and eco-friendly practices in the agri-food sector has sparked an interest in finding alternative uses for such waste materials. One promising approach is the utilization of waste from the agri-food industry as feed for the rearing of mealworms (Tenebrio molitor). Since agri-food waste is rich in proteins, carbohydrates, lipids, and vitamins, as well as other bioactive compounds, all of which are essential for insect growth and development, incorporating such waste into the diet of mealworms promotes sustainable insect production, reducing the economic and environmental problems associated with waste disposal. This practice can also be beneficial for the rearing of mealworms since their nutritional value can also be enhanced. To this end, various waste materials, such as fruit and vegetable peels, spent grains, and food processing residues, have been investigated as potential feed sources, leading to increased mass production, lower cost, and enhanced nutritional value. This review aims to highlight the potential of agri-food waste as a feed source for mealworms, as well as their potential to enhance their nutritional value. Furthermore, the potential applications of mealworms reared on agri-food waste are highlighted, including their potential as a sustainable protein source for human consumption and as feed ingredients in the livestock and aquaculture sectors.

Biodegradable, UV-blocking, and antioxidant films from lignocellulosic fibers of spent coffee grounds

Plastics are strong, flexible, and inexpensive and hence desirable for packaging. However, as they biodegrade very slowly, their waste remains a global burden and pollution, warranting a search for safer alternatives. Towards this end, residual fibers from biowaste, such as spent coffee grounds (SCGs), stand out for creating biodegradable packaging materials. Herein, lignocellulosic fibers from SCG were extracted, and various amounts (0.6, 0.8, 1.0, and 1.2 g) were solubilized using 68 % ZnCl2 and crosslinked with salt (CaCl2) amounts 0.1, 0.2, 0.3 and 0.4 g and prepared biodegradable films. The films were characterized for their color, thickness, moisture content, tensile strength, elongation at break, water vapor permeability, transmittance of electromagnetic radiation, biodegradability, and antioxidant properties. The results reveal that the films possess the highest tensile strength of 26.8 MPa. The tensile strengths are positively correlated to salt and SCG extract amounts. The percentage of elongation decreased with an increase in the calcium ions but increased with SCG residue increment. The films biodegraded in the soil, and most lost >80 % of their initial weight in 45 and 100 days, respectively, at 30 % and 12 % soil moisture. Biodegradability and water vapor permeability decreased with an increase in salt content. Films also showed antioxidant properties and blocked UV and IR radiation significantly. Overall, this research involving green and recyclable chemicals in preparation of SCG residue fibers is a promising, economical, and sustainable route to produce strong biodegradable films to replace petrochemical plastics and thus is an attractive contribution to the circular bioeconomy.

Coffee oligosaccharides and their role in health and wellness

Coffee oligosaccharides (COS) are novel sources of prebiotics comprising manno-oligosaccharides, galacto-oligosaccharides, arabinoxylan-oligosaccharides, and cello-oligosaccharides. These oligosaccharides function as prebiotics, antioxidant-dietary fiber owing to important physicochemical and physiological properties, adjuvants, pharma, nutraceutical food, gut health, immune system boosting, cancer treatment, and many more. Research suggests COS performs prebiotic action, as it enhances gut health by promoting beneficial bacteria in the colon and releasing functional metabolites such as SCFAs. However, research on COS concerning other metabolic illnesses is still lacking. Among various production strategies, pretreatment and enzymatic hydrolysis are preferred for the production of COS. Functional oligosaccharides can add value to coffee waste and reduce the environmental impact of coffee manufacturing, besides providing more options for healthy and active ingredients. This review updates COS, production, bio-activity, their role as a functional food, food supplements/natural food additives, prebiotics and many applications of health sectors. Research is desirable to extend information on COS and their bio-activity, besides in vivo and clinical trials, to assess their effects in prior human formulations into the food and therapeutic arena.

Utilization of spent coffee grounds as fillers to prepare polypropylene composites for food packaging applications

Biomass-derived wastes as the additive of nondegradable plastics have been paid more attention due to the ever-growing environmental pollution and energy crisis. Herein, the spent coffee grounds (SCG) have been used as fillers in polypropylene (PP) after the heat treatment to realize its recycling utilization. The effect of the heat treatment atmosphere on the properties of the obtained SCG and SCG/PP composites has been investigated systematically. The results show that the residual coffee oil can be removed more thoroughly under an air atmosphere than under a nitrogen atmosphere at a relatively low cost and an eco-friendly process. The lower residual oil rate of SCG is beneficial to improve the comminution and further enhance the affinity with the PP matrix. The obtained SCG/PP composites hold lower water absorption, higher hydrophobicity, and better mechanical properties, implying their potential applications in the field of food packaging. RESEARCH HIGHLIGHTS: Spent coffee grounds have been used as fillers in PP after the heat treatment. The heat treatment in the air is more favorable for the removal of the coffer oil of SCG. The low residual oil rate in SCG can improve its comminution and affinity with PP. The SCG/PP composites hold excellent performances for food packaging applications.

Caffeic Acid in Spent Coffee Grounds as a Dual Inhibitor for MMP-9 and DPP-4 Enzymes

Type 2 diabetes mellitus and diabetic foot ulcers remain serious worldwide health problems. Caffeic acid is one of the natural products that has been experimentally proven to have diverse pharmacological properties. This study aimed to assess the inhibitory activity of caffeic acid and ethanolic extract of spent coffee grounds targeting DPP-4 and MMP-9 enzymes and evaluate the molecular interactions through 50-ns molecular dynamics simulations. This study also introduced our new version of PyPLIF HIPPOS, PyPLIF HIPPOS 0.2.0, which allowed us to identify protein-ligand interaction fingerprints and interaction hotspots resulting from molecular dynamics simulations. Our findings revealed that caffeic acid inhibited the DPP-4 and MMP-9 activity with an IC50 of 158.19 ± 11.30 µM and 88.99 ± 3.35 µM while ethanolic extract of spent coffee grounds exhibited an IC50 of 227.87 ± 23.80 µg/100 µL and 81.24 ± 6.46 µg/100 µL, respectively. Molecular dynamics simulations showed that caffeic acid interacted in the plausible allosteric sites of DPP-4 and in the active site of MMP-9. PyPLIF HIPPOS 0.2.0 identified amino acid residues interacting more than 10% throughout the simulation, which were Lys463 and Trp62 in the plausible allosteric site of DPP-4 and His226 in the active site of MMP-9.

The Potential of Spent Coffee Grounds in Functional Food Development

Coffee is a popular and widely consumed beverage worldwide, with epidemiological studies showing reduced risk of cardiovascular disease, cancers and non-alcoholic fatty liver disease. However, few studies have investigated the health effects of the post-brewing coffee product, spent coffee grounds (SCG), from either hot- or cold-brew coffee. SCG from hot-brew coffee improved metabolic parameters in rats with diet-induced metabolic syndrome and improved gut microbiome in these rats and in humans; further, SCG reduced energy consumption in humans. SCG contains similar bioactive compounds as the beverage including caffeine, chlorogenic acids, trigonelline, polyphenols and melanoidins, with established health benefits and safety for human consumption. Further, SCG utilisation could reduce the estimated 6-8 million tonnes of waste each year worldwide from production of coffee as a beverage. In this article, we explore SCG as a major by-product of coffee production and consumption, together with the potential economic impacts of health and non-health applications of SCG. The known bioactive compounds present in hot- and cold-brew coffee and SCG show potential effects in cardiovascular disease, cancer, liver disease and metabolic disorders. Based on these potential health benefits of SCG, it is expected that foods including SCG may moderate chronic human disease while reducing the environmental impact of waste otherwise dumped in landfill.

Spent Coffee Grounds Valorization in Biorefinery Context to Obtain Valuable Products Using Different Extraction Approaches and Solvents

The valuable products that can be isolated from spent coffee ground (SCG) biomass consist of a high number of bioactive components, which are suitable for further application as raw materials in various production chains. This paper presents the potential value of the SCG obtained from large and local coffee beverage producers, for the production of valuable, biologically active products. Despite its high potential, SCG has not been utilized to its full potential value, but is instead discarded as waste in landfills. During its decomposition, SCG emits a large amount of CO₂ and methane each year. The main novelty of our work is the implementation of sequential extraction with solvents of increased polarity that allows for the maximal removal of the available extractives. In addition, we have compared different extraction techniques, such as conventional and Soxhlet extraction, with more effective accelerated solvent extraction (ASE), which has seen relatively little use in terms of SCG extraction. By comparing these extraction methods and highlighting the key differences between them in terms of extraction yield and obtained extract composition, this work offers key insights for further SCG utilization. By using sequential and one-step accelerated solvent extraction, it is possible to obtain a significant number of extractives from SCG, with a yield above 20% of the starting biomass. The highest yield is for coffee oil, which is obtained with n-hexane ranging between 12% and 14% using accelerated solvent extraction (ASE) according to the scheme: n-hexane→ethyl acetate→60% ethanol. Using single-stage extraction, increasing the ethanol concentration also increases the total phenolic content (TPC) and it ranges between 18.7-23.9 Gallic acid equivalent (GAE) mg/g. The iodine values in the range of 164-174 using ASE and Soxhlet extraction shows that the hexane extracts contain a significant amount of unsaturated fatty acids; coffee oils with a low acid number, in the range of 4.74-6.93, contain few free fatty acids. The characterization of separated coffee oil has shown that it mainly consists of linoleic acid, oleic acid, palmitic acid, stearic acid and a small number of phenolic-type compounds.