Spent coffee grounds improve the nutritional value in elements of lettuce (Lactuca sativa L.) and are an ecological alternative to inorganic fertilizers

Spent coffee grounds as an alternative fertilizer: impact on bioaccessibility of antioxidants and commercial quality of lettuce

BACKGROUND

During the processing of spent coffee grounds (SCGs) several residues are obtained, which are mostly disposed of in landfills. There is an urgent need for a comprehensive waste management strategy for these residues. This study evaluates the potential of SCGs as a biofertilizer by assessing their effects on lettuce leaves and the release of antioxidants following in vitro digestion and fermentation.

RESULTS

Lettuce plants were grown with different amounts of SCGs (0-150 g kg-1) in the substrate. High SCG concentrations in the soil generated lighter colored tissues, a decrease in the green color, less root development, and lower dry weight of leaves (P < 0.05). The SCG levels also affected the release of antioxidants by the final product. This effect was more pronounced in the digested fraction: applying the Ferric Reducing Antioxidant Power (FRAP) method, the addition of SCGs from 10 g kg-1 to 125 g kg-1 increased the amount of antioxidant from 43.88 ± 4.81 to 105.96 ± 29.09 μmol Trolox g-1 of dry weight (P < 0.05). The Indigo Carmine Reducing Capacity (ICRED) method also showed a similar trend, but in this case the highest value was obtained with 150 g kg-1 of SCGs (16.41 ± 3.93 mmol catechin g-1 of dry weight) (P < 0.05). Moreover, in the fermented fraction a significant increase in the antioxidant released was found with low levels of SCG(P<0.05), while lettuces fertilized with intermediate amounts of SCGs (25 and 50 g kg-1) presented the highest amount of insoluble antioxidant (P < 0.05).

CONCLUSION

A compromise should be found in order to achieve a product with a high antioxidant capacity and an acceptable visual quality. © 2024 Society of Chemical Industry.

Exploring Spent Coffee Grounds: Comprehensive Morphological Analysis and Chemical Characterization for Potential Uses

The agroindustry generates substantial quantities of byproducts, particularly in coffee production, which yields significant waste, most notably spent coffee grounds (SCGs). This study explores the potential of SCGs as a versatile resource for applications in both food and nonfood sectors. A comprehensive chemical analysis revealed that SCGs consist of 30.2 wt.% cellulose, 25 wt.% hemicellulose, and 12 wt.% lignin. Morphological characterization was performed using field emission scanning electron microscopy (FESEM). Additional analyses included attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) and thermogravimetric analysis (TGA). ATR-FTIR identified key polysaccharides and oils, whereas TGA offered insights into the thermal degradation behavior of SCGs, confirming the presence of typical plant cell wall components. X-ray diffraction (XRD) patterns revealed low crystallinity, consistent with SCGs' amorphous structure. Mineral content was assessed using inductively coupled plasma atomic emission spectrometry (ICP-AES) and atomic absorption spectrophotometry (AAS). The results showed that mineral concentrations in SCGs (per 0.01 kg) were within recommended daily intake limits, confirming their safety for potential human consumption. These findings establish SCGs as a valuable lignocellulosic biomass with applications in composite materials. Additionally, it can serve as an organic soil amendment after fermentation to prevent stress on plants. This approach supports effective waste management and advances resource sustainability practices in the agro-industrial sector.

Enhanced phytoremediation of vanadium using coffee grounds and fast-growing plants: Integrating machine learning for predictive modeling

Vanadium (V) contamination posed a significant environmental challenge, while phytoremediation offered a sustainable solution. Phytoremediation performance was often limited by the slow growth cycles of traditional plants. A novel approach to enhancing V phytoremediation by integrating coffee grounds with fast-growing plants such as barley grass, wheat grass, and ryegrass was investigated in this study. The innovative use of coffee grounds leveraged not only their nutrient-rich composition but also their ability to reduce oxidative stress in plants, thereby significantly boosting phytoremediation efficiency. Notably, ryegrass achieved 48.7% V5+ removal within 6 d with initial 20 mg/L V5+ (0.338 mg/L·d·g ryegrass). When combined with coffee grounds, V5+ removal by using wheat grass increased substantially, rising from 30.51% to 62.91%. Gradient Boosting and XGBoost models, trained with optimized parameters including a learning rate of 0.1, max depth of 3, and n_estimators of 300, were employed to predict and optimize V5+ concentrations in the phytoremediation process. These models were evaluated using mean squared error (MSE) and coefficient of determination (R2) metrics, achieving high predictive accuracy (R2 = 0.95, MSE = 1.20). Feature importance analysis further identified the initial V5+ concentration and experimental duration as the most significant factors influencing the model's predictions. The addition of coffee grounds not only mitigated the stress of heavy metals on ryegrass, leading to significant reductions in CAT (87.2%), POD (98.8%), and SOD (39.2%) activities in ryegrass roots, but also significantly altered the microbial community abundance in the plant roots. This research provided an innovative enhancement to traditional phytoremediation methods, and established a new paradigm for using machine learning to predict and optimize V5+ remediation outcomes. The effectiveness of this technology in multi-metal polluted environments warrants further investigation in the future.

Bioactive Compounds and Valorization of Coffee By-Products from the Origin: A Circular Economy Model from Local Practices in Zongolica, Mexico

The by-products of green coffee processing are rich in compounds that can be recycled for their possible use in the production of beverages, fertilizers and weed control in production areas. The objective of this work was to identify the organic and inorganic bioactive compounds of green coffee and the coffee by-products related to the production of origin, such as dried cascara (skin-pulp), parchment and silverskin (unroasted), in order to investigate the role their biomolecules may have in reuse through practices and local knowledge, not yet valued. The metabolomic profile by HPLC-ESI-HRMS of the aqueous extract of the dried cascara highlighted 93 non-volatile molecules, the highest number reported for dried cascara. They belong to groups of organic acids (12), alkaloids (5), sugars (5), fatty acids (2), diglycerides (1), amino acids (18), phospholipids (7), vitamins (5), phenolic acids (11), flavonoids (8), chlorogenic acids (17), flavones (1) and terpenes (1). For the first time, we report the use of direct analysis in real-time mass spectrometry (DART-MS) for the identification of metabolites in aqueous extracts of dried cascara, parchment, silverskin and green coffee. The DART analysis mainly showed the presence of caffeine and chlorogenic acids in all the extracts; additionally, sugar adducts and antioxidant compounds such as polyphenols were detected. The mineral content (K, Ca, P, S, Mg and Cl) by EDS spectrometry in the by-products and green coffee showed a relatively high content of K in the dried cascara and green coffee, while Ca was detected in double quantity in the silverskin. These metabolomic and mineral profile data allow enhancement of the link between the quality of green coffee and its by-products and the traditional local practices in the crop-growing area. This consolidates the community's experience in reusing by-products, thereby minimizing the impact on the environment and generating additional income for coffee growers' work, in accordance with the principles of circular economy and bioeconomy.

A novel process for the complete recycling of exhausted coffee capsules with a fully circular approach: Design of the industrial plant and Techno-Economic analysis of the process

The objective of this paper is to present the technical and feasibility analysis of an innovative mechanical recycling system for exhausted coffee capsules. This recycling process involved the sorting of spent coffee grounds (SGC) and the subsequent drying and melt-mixing of a portion of these grounds with the remaining capsule components, mainly composed of polypropylene (PP), along with optional virgin PP. These newly developed composite materials exhibited mechanical and rheological properties comparable or even surpassing those of virgin PP. They were also successfully utilized for the injection of new capsule shells, thus alignin with the principles of the circular economy. In addition to the technical aspects, this paper present a comprehensive Techno-Economic Analysis (TEA) of the proposed recycling processes, considering the inclusion of virgin PP (0-20 %) and the initial moisture content (MSGC) of SGC(5-55 %) as varying factors. An industrial plant, designed to handle up to 190 million exhausted coffee capsules and produce up to 1500 tons of recycled compund was appropriately sized. The analysis revealed that processes are profitable across all examined scenarios and that the Net Present Value ranged between 800 k€ (for vPP = 20 % and MSGC = 55 %) and 2000 k€ (for vPP = 0 % and MSGC = 5 %).

Short-term impact of different doses of spent coffee grounds, salt, and sand on soil chemical and hydrological properties in an urban soil

Natural and human activities have deteriorated urban soil's health and ecological functions as compared to forest soils. Therefore, we hypothesized that any intervention in poor quality soil in urban area will change their chemical and water retention properties. The experiment was conducted in Krakow (Poland) in completely randomized design (CRD). The soil amendments used in this experiment consisted of control, spent coffee grounds (SCGs), salt, and sand (1 and 2 t ha-1) in order to evaluate the impact of these soil amendments on the urban soil chemical and hydrological properties. Soil samples were collected after 3 months of soil application. The soil pH, soil acidity (me/100 g), electrical conductivity (mS/cm), total carbon (%), CO2 emission (g m-2 day-1), and total nitrogen (%) were measured in laboratory condition. The soil hydrological properties like volumetric water content (VWC), water drop penetration time (WDPT), current water storage capacity (Sa), water storage capacity after 4 and 24 h (S4 and S24), and capillary water Pk (mm) were also determined. We noted variations in soil chemical and water retention properties in urban soil after the application of SCGs, sand, and salt. It was observed that SCGs (2 t ha-1) has reduced soil pH and nitrogen (%) by 14 and 9%, while the incorporation of salt resulted in maximum soil EC, total acidity, and soil pH. The soil carbon (%) and CO2 emission (g m-2 day-1) were enhanced and declined by SCGs amendment. Furthermore, the soil hydrological properties were significantly influenced by the soil amendment (spent coffee grounds, salt, and sand) application. Our results showed that spent coffee grounds mixing in urban soil has considerably enhanced the soil VWC, Sa, S4, S24, and Pk, whereas it decreased the water drop penetration time. The analysis showed that the single dose of soil amendments had not improved soil chemical properties very well. Therefore, it is suggested that SCGs should be applied more than single dose. This is a good direction to look for ways to improve the retention properties of urban soil and you can consider combining SCGs with other organic materials like compost, farmyard manure, or biochar.

N-Doped porous carbons obtained from chitosan and spent coffee as electrocatalysts with tuneable oxygen reduction reaction selectivity for H2O2 generation

Nitrogen-containing porous carbons prepared by the pyrolysis of adequate biopolymer-based precursors have shown potential in several electrochemical energy-related applications. However, it is still of crucial interest to find the optimal precursors and process conditions which would allow the preparation of carbons with adequate porous structure as well as suitable nitrogen content and distribution of functional groups. In the present work we suggested a straightforward approach to prepare N-doped porous carbons by direct pyrolysis under nitrogen of chitosan : coffee blends of different compositions and using KOH for simultaneous surface activation. The synthetized carbon materials were tested for the electrochemical oxygen reduction to hydrogen peroxide (H₂O₂). A higher fraction of chitosan in the precursor led to a decrease in meso- and nano-porosity of the formed porous carbons, while their activity towards H₂O₂ generation increased. The nitrogen species derived from chitosan seem to play a very important role. Out of the synthesized catalysts the one with the largest content of pyridinic nitrogen sites exhibited the highest faradaic efficiency. The faradaic efficiencies and current densities of the synthesized materials were comparable with the ones of other commercially available carbons obtained from less renewable precursors.

Total Zn of foods and bioaccesible fractions in the small and large intestine after in vitro digestion and fermentation with fecal material of healthy adults and children: Influence of culinary techniques

The healthy status of human beings is associated with an appropriate nutritional status in Zn, which must firstly be bioavailable. We measured the total Zn amount and its bioaccesibility in raw foods and after cooking by common culinary techniques. These foods were submitted to an in vitro digestion and fermentation with faecal inocula from healthy adults and children to evaluate Zn bioaccesibility in the small and large intestine. Mean total Zn amount provided by foods was 8.080 μg/g. Zn amount released from food in the small intestine was significantly different among several food groups and lower in raw vegetal foods compared to cooked ones (frying, roasting and grilling; p < 0.05); the same behaviour was found in the large intestine for healthy children. Zn bioaccesibility in the large intestine varied statistically according to the subjects' idiosyncrasies, and was higher in healthy children (p < 0.05) probably due to growth demands and different composition of the colonic microbiota. In healthy adults and children, the bioaccesible fractions were 33.0 ± 20.4 % for the small intestine, 16.4 ± 22.0 and 59.6 ± 29.9% for the large one, and the non-bioaccessible ones 50.6 ± 19.9 and 7.4 ± 9.1%, respectively.

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.

Evaluation of thermal/acoustic performance to confirm the possibility of coffee waste in building materials in using bio-based microencapsulated PCM

As the demand for coffee has increased, by-product disposal has become a challenge to solve. Many studies are being conducted on how to use coffee waste as building materials to recycle it. In this study, the thermal performance and acoustic performance of a composite developed using bio-based microencapsulated phase change material (MPCM) and coffee waste were evaluated, and the composite was applied as building material. The coffee waste was successfully degreased with ethanol to produce composites, and removal of contaminants and oils was confirmed via scanning electron microscopy. In the phase change process of MPCM, an appropriate amount of thermal energy is absorbed and stored, and the temperature is maintained. MPCM was used in the mixture and the improved thermal performance was evaluated via differential scanning calorimetry analysis, revealing a latent heat of 3.8 J/g for MPCM content of 10%. Further, thermal imaging cameras revealed that an increase in the proportion of MPCM leads to a slower decrease in temperature because of the heat preserved by MPCM over time. In an acoustic performance evaluation, impedance tube test results showed different aspects depending on low, mid, and high-frequency bands. Specifically, at medium frequencies, which correspond to the range of noise generated in cafes, specimens fabricated using MPCM were confirmed to exhibit a higher sound absorption coefficient and an improved acoustic performance. Hence, the composite can be considered an eco-friendly building material with promising thermal and acoustic performance.

The wastes of coffee bean processing for utilization in food: a review

A few million cubic tons of waste are generated annually as a result of coffee processing. As a beverage, coffee in itself is a rich source of melanoidins, phenolic compounds, and other phytonutrients which confer a wide range of health benefits. These wastes generated every year are usually discarded as landfill mass, mixed with animal fodder, or incinerated. Coffee wastes, due to their high content of tannins and caffeine, can degrade the soil quality and induce carcinogenicity when mixed with animal fodder. This review aims to identify the potential of coffee silver skin and spent coffee grounds, both generated as a result of the roasting process and instantization processes. Coffee husk and coffee flour are also well-known for their excellent bioactive roles. The proximate composition of coffee silverskin indicates a rich dietary fibre source and finds wide applications in bakery and other allied food products. This process could generate a value-added product and alleviate the disposing quality of remnant spent coffee grounds. Companies are exploring novel ideas of producing coffee flour obtained from drying and milling of coffee cherries for applications in day-to-day food products. Coffee and coffee waste combined with its high concentration of fibre, colorant pigments, and antioxidant compounds, has immense potential as a functional ingredient in food systems and needs to be explored further for its better utilization.

Posidonia Natural Residues as Growing Substrate Component: An Ecofriendly Method to Improve Nutritional Profile of Brassica Microgreens

The aim of this study was to test Posidonia oceanica (L.) Delile seagrass residues (leaves and fibers) as growing media component to improve the nutritional quality of two different brassica microgreens (Mizuna and Rapini). We hypothesized that addition of posidonia residues in the substrate would result in higher concentration of certain mineral nutrients in the edible parts of plants. Substrates were obtained by mixing leaves and fibers, each material at the rate of 25, 50 and 75% (v/v), with a peat based commercial substrate, that was also used at 100% rate as a control treatment. Two experiments were carried out (Experiment 1: Mizuna microgreens production in growth chamber conditions; Experiment 2: Mizuna and Rapini microgreens production in greenhouse conditions). Plant growth measurements and chemical analysis on edible parts (mineral tissue composition and main bioactive compounds - polyphenol, chlorophylls and carotenoids contents) were performed in order to evaluate the effects of the different substrates on growth and nutritional composition of brassica microgreens. In order to evaluate the consumer safety, daily intake, percentage of recommended daily allowance for I (RDA-I) and hazard quotient (HQ) for I intake through consumption of 50 and 100 g portions of Rapini microgreens were calculated. Posidonia in the growing media mixtures increased I and B content in edible parts of microgreens. The calculated HQ underlines the safety of these products. Results confirm the possibility to improve nutritional profile of brassica microgreens by using this natural material as a growing media component, resulting in a sustainable approach.

Ca and Mg Concentrations in Spices and Growth of Commonly Sporulated and Non-Sporulated Food-Borne Microorganisms According to Marketing Systems

Ca and Mg levels were determined in five spices according to marketing system (in bulk or commercialized in glass or polyethylene terephthalate (PET) containers) and correlated with microbial growth of commonly sporulated (Clostridium perfringens and Bacillus cereus) and non-sporulated (Listeria monocytogenes, psychrophilic and mesophilic bacteria, and yeasts and molds) food-borne pathogens present in them, when they were previously added to the microbial culture media. The basil had the highest mean Ca and Mg level and showed the highest microbial growth in the food-borne pathogenic microorganisms studied (p < 0.001). For Ca, the lowest levels were measured in cloves (p < 0.001), which had the lowest capacity for microbial contamination. Ca and Mg contents in spices correlated linear and positively (p < 0.05). Ca concentrations weakly and positively correlated (p < 0.05) with microbial counts for almost all studied microorganisms, and Mg levels for B. cereus, C. perfringens, and mesophilic bacteria (p < 0.05), possibly acting as a growing factor for some sporulated and non-sporulated foodborne pathogens. These relationships are especially significant when PET vs. glass was used as a packaging material for spices.

Washed hydrochar from spent coffee grounds: A second generation of coffee residues. Evaluation as organic amendment

Spent coffee grounds (SCG) hydrochar is a second-generation solid waste obtained by hydrothermal carbonization (HTC). Two washed hydrochars from SCG (175 and 185 °C; 12 MPa of N₂) were tested as organic amendments of an agricultural soil (Cambic Calcisol), at doses of 1 and 2.5%, in an in vitro assay using Lactuca sativa as a crop plant. The washed hydrochars differ from the SCG in organic carbon (OC) (56 vs 47%), C/N ratio (29 vs 24), polyphenols (186 vs 77 mg GAE/g), pH (4.1 vs 5.8), assimilable P (186 vs 1274 ppm) and K (32 vs 2475 ppm). The particles of washed hydrochars have a lower size and a more porous structure than SCG particles. Higher HTC temperatures generate greater differences with SCG. The effects on the soil of washed hydrochars are similar to SCG, regarding OC, total N, C/N ratio, available K and P contents. The influence of SCG and washed hydrochars on lettuces is also similar: both give rise to plant growth inhibition and increase in the contents of Ca, Mg, Cu, Fe and Mn. Nevertheless, washed hydrochars seem to be more effective in the mobilization of elements in the soil than SCG, which could be attributed to their higher content of polyphenols. For example: Ca (139 mg/100 g with SCG and 160 mg/100 g with hydrochar) and Fe (0.742 mg/100 g with SCG and 1.45 mg/100 g with hydrochar). Therefore, it can be concluded that SCG hydrochars could be used as organic amendments with similar limitations and advantages to SCG.

Zn, Cu, and Fe Concentrations in Dehydrated Herbs (Thyme, Rosemary, Cloves, Oregano, and Basil) and the Correlation with the Microbial Counts of Listeria monocytogenes and Other Foodborne Pathogens

Zn, Cu, and Fe concentrations were measured in dehydrated herbs (thyme, rosemary, cloves, oregano, and basil) marketed in bulk or packaged in glass or polyethylene terephthalate (PET). Microbial counts of Listeria monocytogenes and other five foodborne pathogens were also checked when herbs were previously added to the growing media. The highest mean concentrations were found in basil for Zn and Cu, and in thyme and basil for Fe; the lowest ones for these minerals were in cloves (p < 0.05). Basil had significantly higher microbial counts in five of the six foodborne pathogens studied (p < 0.05). Cloves have the best hygienic quality as there is no microbial growth of L. monocytogenes, Clostridium perfringens, and Bacillus cereus; they therefore could be used as a natural preservative in food. Aromatic herbs marketed in bulk showed a significantly higher microbial count (p < 0.05). Zn, Cu, and Fe concentrations were positively correlated with microbial growth for L. monocytogenes, C. perfringens, B. cereus, and psychrophilic microorganisms (p < 0.05), so they could act as a growing factor for the foodborne pathogens.

Potential Use of Waste Activated Sludge Hydrothermally Treated as a Renewable Fuel or Activated Carbon Precursor

In this work, dewatered waste activated sludge (DWAS) was subjected to hydrothermal carbonization to obtain hydrochars that can be used as renewable solid fuels or activated carbon precursors. A central composite rotatable design was used to analyze the effect of temperature (140–220 °C) and reaction time (0.5–4 h) on the physicochemical properties of the products. The hydrochars exhibited increased heating values (up to 22.3 MJ/kg) and their air-activation provided carbons with a low BET area (100 m²/g). By contrast, chemical activation with K₂CO₃, KOH, FeCl₃ and ZnCl₂ gave carbons with a well-developed porous network (BET areas of 410–1030 m²/g) and substantial contents in mesopores (0.079–0.271 cm³/g) and micropores (0.136–0.398 cm³/g). The chemically activated carbons had a fairly good potential to adsorb emerging pollutants such as sulfamethoxazole, antipyrine and desipramine from the liquid phase. This was especially the case with KOH-activated hydrochars, which exhibited a maximum adsorption capacity of 412, 198 and 146 mg/g, respectively, for the previous pollutants.

Can we trust biomarkers identified using different non-targeted metabolomics platforms? Multi-platform, inter-laboratory comparative metabolomics profiling of lettuce cultivars via UPLC-QTOF-MS

INTRODUCTION

Data analysis during UPLC-MS non-targeted metabolomics introduces variation as different manufacturers use specific algorithms for data treatment and this makes untargeted metabolomics an application for the discovery of new biomarkers with low confidence in the reproducibility of the results under the use of different metabolomics platforms.

OBJECTIVES

This study compared the ability of two platforms (Agilent UPLC-ESI-QTOF-MS and Waters UPLC-IMS-QTOF-MS) to identify biomarkers in butterhead and romaine lettuce cultivars.

METHODS

Two case studies by different metabolomics platforms: (1) Waters and Agilent datasets processed by the same data pre-processing software (Progenesis QI), and (2) Datasets processed by different data pre-processing software.

RESULTS

A higher number of candidate biomarkers shared between sample groups in case 2 (101) than in case 1 (26) was found. Thirteen metabolites were common to both cases. Romaine lettuce was characterised by phenolic compounds including flavonoids, hydroxycinnamate derivatives, and 9-undecenal, while Butterhead showed sesquiterpene lactones and xanthosine. This study demonstrates that high percentages of the most discriminatory entities can be obtained by using the manufacturers' embedded pre-processing software and following the recommended processing data guidelines using commercial software to normalise the data matrix.

Phytotoxicity and chelating capacity of spent coffee grounds: Two contrasting faces in its use as soil organic amendment

Spent coffee grounds (SCG) are a bioresidue generated in large amounts worldwide, which could be employed as either fresh or transformed organic soil amendment, by means of different treatments in order to improve its agronomic qualities. An in vitro experiment was conducted in order to evaluate the effect of using different bioamendments derived from spent coffee grounds (SCG) on biomass and Zn, Cu and Fe content of lettuces. Application of 7.5% (w/w) fresh SCG, vermicompost, compost, biochars (at 270 and 400 °C; pyrolysis), SCG washed with ethanol and water, and hydrolysed SCG was carried out in an agricultural soil (Cambic Calcisol). In order to compare with conventional agriculture, the addition of NPK fertilizer was also assessed. Only vermicompost and biochar at 400 °C overcome the growth limitation of SCG. However, these treatments diminished Zn, Cu and Fe concentrations in lettuce probably due to the destruction (microbial degradation/thermal treatment) of natural chelating components (polyphenols). Increase in mineral content was observed in those treatments that did not completely eliminate polyphenols. NPK fertilizer gave rise to lettuces with higher biomass but lower micronutrients content. The results lead us to the possible solution for the use of SCG as organic amendment by vermicomposting and biocharization in order to eliminate toxicity.

Circular reutilization of coffee waste for sound absorbing panels: A perspective on material recycling

The increase in coffee consumption has led to increased production of coffee waste. Methods to recycle coffee waste are constantly being researched. Coffee powder is a porous material that can effectively be used to absorb sound. In this study, sound-absorbing panels were developed using coffee waste combined with resin. A sound absorption characterization of the new material was performed. Then, the noise reduction potential using coffee-waste sound absorbers was investigated in cafés. A café has several noise sources, such as coffee machines, music, and the voices of people. The noise reduction effect was evaluated using the ODEON simulation software together with the improvement in both the clarity and reverberation time in a case study café. In the investigated room, the acoustic definition (D50) increased up to 0.8, while the reverberation time (RT) reduced to 0.6 s. The results of this study demonstrate that the noise generated in the café was reduced by recycling the coffee waste produced as a by-product in the same building. Finally, this study presents a new construction material manufactured through coffee waste that is in turn applied to cafés where the coffee waste itself is produced.

Modulation of gut microbiota by spent coffee grounds attenuates diet-induced metabolic syndrome in rats

Coffee brewing produces spent coffee grounds as waste; few studies have investigated the health benefits of these grounds. This study investigated responses to spent coffee grounds in a diet-induced rat model of metabolic syndrome. Male Wistar rats aged 8-9 weeks were fed either corn starch-rich diet or high-carbohydrate, high-fat diet for 16 weeks, which were supplemented with 5% spent coffee grounds during the last 8 weeks. Rats fed non-supplemented diets were used as controls. High-carbohydrate, high-fat diet-fed rats developed metabolic syndrome including abdominal obesity, impaired glucose tolerance, dyslipidemia, and cardiovascular and liver damage. Body weight, abdominal fat, total body fat mass, systolic blood pressure, and concentrations of plasma triglycerides and non-esterified fatty acids were reduced by spent coffee grounds along with improved glucose tolerance and structure and function of heart and liver. Spent coffee grounds increased the diversity of the gut microbiota and decreased the ratio of Firmicutes to Bacteroidetes. Changes in gut microbiota correlated with the reduction in obesity and improvement in glucose tolerance and systolic blood pressure. These findings indicate that intervention with spent coffee grounds may be useful for managing obesity and metabolic syndrome by altering the gut microbiota, thus increasing the value of this food waste.

Mineral profile of weight loss related foods marketed in Spain

Low calorie foods are products designed to replace complete meals or to control snacking in many hypocaloric diets. These products provide many nutrients to the human diet, but little is known about their mineral elements composition. Here we study the mineral profile of weight loss related products, including the analysis of 22 elements (As, Ba, Be, Bi, Cd, Co, Cr, Cu, K, Mn, Mo, Na, Ni, P, Pb, Th, Tl, Sb, U, V, Y and Zn) in 73 commercial products marketed in Spain. In general a portion of these products provide up to 20-30% of the daily dietary reference intake of essential trace minerals like Cr or Mo. On the contrary, some of these foods have large concentrations of toxic minerals like As, Cd or Pb. In fact, the intake of those products with higher concentrations of toxic elements during a weight loss program could pose a risk to human health.