Characterization, bioavailability and protective effects of phenolic-rich extracts from almond hulls against pro-oxidant induced toxicity in Caco-2 cells

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.

Almond By-Products: A Comprehensive Review of Composition, Bioactivities, and Influencing Factors

One of today's major environmental and economic challenges is the fight against both agro- and industrial-waste. Almond production and industrial processing exemplifies this issue, as it generates tons of waste and by-products, with hulls and shells accounting for about 70% of the total fruit's weight while skins represent about 6% of the shelled kernel. Since the edible kernel, about 23% of the total fruit weight, holds the highest commercial value, there has been growing interest within the scientific community in exploring the potential of these by-products. However, almond by-products contain a wide range of phytochemicals, mainly phenolic compounds (flavonoids and non-flavonoids), and triterpenoids, with great potential as antioxidant, antimicrobial, anti-inflammatory, and prebiotic properties. Although these by-products are being explored as alternative sources in the textile, pharmaceutical/cosmetic, and food industries, their primary use remains in livestock feed or bedding, or as biofuel. This review compiles recent scientific data on almond by-products' phytochemical composition and bioactivities aiming to support sustainable and holistic agricultural practices.

Upcycling commercial nut byproducts for food, nutraceutical, and pharmaceutical applications: A comprehensive review

This article presents a comprehensive overview of upcycling commercial nut byproducts (such as Brazil nut, cashew, hazelnut, macadamia, peanut (also known as a legume), pecan, pine nut, pistachio, and walnut) for food, nutraceutical, and pharmaceutical applications. Upcycling nut byproducts, namely husk/hull, hard shell, brown skin, defatted flour/meal/cake, pine cone, cashew nut shell liquid, cashew apple, walnut septum, and dreg/okara, has great potential, not only to reduce/minimise waste, but also to fit within the circular economy concept. Each byproduct has its own unique functional properties, which can bring significant value. These byproducts can be used as value-added ingredients to promote better health and well-being, due to their rich sources of diverse bioactive components/phytochemicals, polysaccharides, fibre, lignin, prebiotics, oils, proteins, bioactive peptides, minerals, and vitamins, among other components. This comprehensive review provides a basis for future research and development of product applications for nut byproducts. More studies are needed on novel product development to valorise nut byproducts.

Evaluation of the Genotoxicity of Almond Hull: Implications for Its Use as a Novel Food Ingredient

Almond hull, a substantial byproduct comprising more than half of almond fresh weight, has recently gained attention due to its functionality and sustainability benefits. Despite heightened interest, information regarding its toxicity remains limited. In order to assess its genotoxic potential, we conducted Good Laboratory Practice-compliant in vitro and in vivo studies following Organization for Economic Co-operation and Development (OECD) guidelines. No evidence of toxicity or mutagenicity was observed in a bacterial reverse mutation assay using five tester strains, evaluating almond hull at concentrations up to 5 mg/plate, with or without metabolic activation. Almond hull did not induce chromosome structural damage in a chromosome aberration assay using Chinese hamster ovary cells, nor did it cause any spermatogonial chromosomal aberration in tested male BALB/c mice. To evaluate its ability to induce DNA damage in rodents, a combined micronucleus assay was conducted in KM mice of both sexes. Almond hull was administered at doses of 1250, 2500, and 5000 mg/kg/day via gavage once daily for 2 days. No adverse effects of almond hull were observed in the micronucleus assay. Our results indicate no evidence of the genotoxic potential of almond hull administered up to the maximum concentrations of 5 g/kg, as recommended by OECD guidelines.

Studies on the Effects of Fermentation on the Phenolic Profile and Biological Activity of Three Cultivars of Kale

Fermentation is used not only to preserve food but also to enhance its beneficial effects on human health and achieve functional foods. This study aimed to investigate how different treatments (spontaneous fermentation or fermentation with the use of starter culture) affect phenolic content, antioxidant potential, and cholinesterase inhibitory activity in different kale cultivars: 'Halbhoner Grüner Krauser', 'Scarlet', and 'Nero di Toscana'. Chosen samples were further tested for their protective potential against the Caco-2 cell line. HPLC-MS analysis revealed that the fermentation affected the composition of polyphenolic compounds, leading to an increase in the content of rutin, kaempferol, sinapinic, and protocatechuic acids. In general, kale cultivars demonstrated various antioxidant activities, and fermentation led to an increase in total phenolic content and antioxidant activity. Fermentation boosted anti-cholinesterase activity most profoundly in 'Nero di Toscana'. Extracts of spontaneously fermented 'Scarlet' (SS) and 'Nero di Toscana' (NTS) showed cytoprotective properties, as revealed by the malondialdehyde (MDA), lactate dehydrogenase (LDH), superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) assays. Additionally, strong anti-inflammatory activity of NTS was shown by decreased release of cytokines IL-1β and TNF-α. Collectively, the conducted studies suggest fermented kale cultivars as a potential source for functional foods.

PhInd-Database on Polyphenol Content in Agri-Food By-Products and Waste: Features of the Database

Timely access to topic-relevant datasets is of paramount importance for the development of any successful strategy (food waste reduction strategy), since datasets illuminate opportunities, challenges and development paths. PhInd is the first comprehensive database on polyphenol content in plant-based by-products from the agri-food sector or the wastewater sector and was developed using peer-reviewed papers published in the period of 2015-2021. In total, >450 scientific manuscripts and >6000 compound entries were included. Database inclusion criteria were polyphenol contents = determined using HPLC/UHPLC quantitative methods. PhInd can be explored through several criteria which are either 'open' or checkboxes. Criteria are given in subsections: (a) plant source; (b) by-product industrial processing; (c) pre-treatment of by-products before the isolation of polyphenols; and (d) the extraction step of polyphenols. Database search results could be explored on the website directly or by downloading Excel files and graphs. This unique database content is beneficial to stakeholders-the food industry, academia, government and citizens.

Acute Oral Toxicity Evaluation of Almond Hull Powders in BALB/c Mice

Almond hull, a substantial byproduct constituting more than half of almond fresh weight, has garnered recent attention due to its abundance in fiber and bioactive content. Despite this huge interest, data on its toxicity remain scarce. In line with the Organization for Economic Cooperation and Development (OECD) 423 guidelines, this study conducted an acute oral toxicity test using almond hull powders processed from three major almond varieties of Butte, Monterey, and Nonpareil on BALB/c female mice, administering dosages of 300 mg/kg body weight (bw), 2000 mg/kg bw, and 5000 mg/kg bw, with observations over a 14-day period. The results indicated that almond hull powders were non-toxic, aligning with the Globally Harmonized System's classification. Administering up to 5000 mg/kg bw of all three varieties of almond hull powders (female BALB/c mice) and 10,000 mg/kg bw of Monterey almond hull powders (both female and male mice) induced no adverse effects in terms of mortality, body weight changes, food intake, organ to weight ratio, and clinical biochemistry. Additionally, histopathological examination revealed no organ abnormalities. This study demonstrates the non-toxic nature of almond hull as an edible food ingredient under experimental conditions, encouraging the further exploration of its potential for safe consumption and its health benefits.

Effect of high levels of almond hulls supplementation on performance and meat oxidative stability in lambs

The main objective of this study was to evaluate if high dietary levels of almond hulls could influence performance and meat oxidative stability in lambs. Twenty lambs, at an average body weight of 28.8 ± 0.30 (SD) kg, were divided into two experimental groups and fed ad libitum for 40 days either with a control diet (cereal-based concentrate, control group) or with a similar diet in which part of the cereals was replaced with 40% of almond hulls on a dry matter basis (AH40 group). Dietary AH did not affect dry matter intake but reduced final body weight, average daily gain, feed conversion ratio or carcass weight. In meat, TBARS values were lower (P < 0.001) in the AH40 group than in control group. The partial replacement of cereals with 40% almond hulls in the diet negatively affecting the growth parameters of the animals but can improve meat shelf-life by reducing lipid oxidation.

Simultaneously Determined Antioxidant and Pro-Oxidant Activity of Randomly Selected Plant Secondary Metabolites and Plant Extracts

Oxidative stress is a well-known phenomenon arising from physiological and nonphysiological factors, defined by the balance between antioxidants and pro-oxidants. While the presence and uptake of antioxidants are crucial, the pro-oxidant effects have not received sufficient research attention. Several methods for assessing pro-oxidant activity, utilizing various mechanisms, have been published. In this paper, we introduce a methodology for the simultaneous determination of antioxidant and pro-oxidant activity on a single microplate in situ, assuming that the FRAP method can measure both antioxidant and pro-oxidant activity due to the generation of pro-oxidant Fe2+ ions in the Fenton reaction. Systematic research using this rapid screening method may help to distinguish between compounds with dominant antioxidant efficacy and those with dominant pro-oxidant effects. Our preliminary study has revealed a dominant pro-oxidant effect for compounds with a higher number of oxygen heteroatoms, especially sp2 hybridized compounds (such as those containing keto groups), such as flavonoids and plant extracts rich in these structural types. Conversely, catechins, carotenoids, and surprisingly, extracts from birch leaves and chestnut leaves have demonstrated dominant antioxidant activity over pro-oxidant. These initial findings have sparked significant interest in the systematic evaluation of a more extensive collection of compounds and plant extracts using the developed method.

Bioactive Compounds of Portuguese Fruits with PDO and PGI

The European Union has established two designations, Protected Designation of Origin (PDO) and Protected Geographical Indication (PGI), to guarantee the authenticity of products with valued specificities associated with the regions where they are produced. The valorization of these products, particularly fruits, not only preserves their natural origins but also promotes the cultivalion of specific regional fruit varieties. This contributes to the preservation of biodiversity and the development of innovative bio-based products in the regions of production. In recent years, substantial efforts have been made to characterize PDO and PGI fruits, particularly in relation to the presence of bioactive compounds with antioxidant and antimicrobial properties. Portugal, with its diverse range of climates and geographical characteristics, is home to numerous fruits with unique flavors, textures, and appearances, many of which are now recognized with PDO or PGI seals. This review compiles data from the production of Portuguese fruits with PDO designations, such as the 'Maça Bravo de Esmolfe' (apple) and 'Pera Rocha do Oeste' (pear), and PGI designations, such as 'Citrinos do Algarve' (citrus)and 'Cereja da Cova da Beira' (cherry), and summarizes studies focusing on the bioactive compounds present in these fruits. The presence of bioactive compounds is a significant aspect of nutritious food, associated with health benefits that consumers are increasingly aware of and value.

Polysaccharides as antioxidants and prooxidants in managing the double-edged sword of reactive oxygen species

Polysaccharides, a class of naturally occurring carbohydrates, were widely presented in animals, plants, and microorganisms. Recently, health benefits of polysaccharides have attracted much attention due to their unique characteristics in reactive oxygen species (ROS) management. ROS, by-products of aerobic metabolism linked to food consumption, exhibited a dual role in protecting cells and fostering pathogenesis collectively termed double-edged sword. Some interesting studies reported that polysaccharides could behave as prooxidants under certain conditions, besides antioxidant capacities. Potentiation of the bright side of ROS could contribute to the host defense that was vitally important for the polysaccharides acting as biological response modifiers. Correspondingly, disease prevention of polysaccharides linked to the management of ROS production was systematically described and discussed in this review. Furthermore, major challenges and future prospects were presented, aiming to provide new insight into applying polysaccharides as functional food ingredients and medicine.

Effect of Phenolic Compounds from Almond Skins Obtained by Water Extraction on Pork Patty Shelf Life

The extraction of phenols from almond skin using water has not been applied before. The purpose of this study was to obtain aqueous extracts from almond skin to be added to pork patties to prolong their shelf life. Four different varieties of almonds were studied and aqueous extracts were obtained. The antioxidant capacity and composition of phenol compounds of the extracts were determined. Results showed that the use of water produces extracts with phenol compounds and antioxidant capacity, with the Antoñeta variety presenting the best performance in terms of antioxidant behavior. The most abundant phenolic compounds identified were isorhamentin-3-O-rutinoside, catechin and protocatechuic acid, all of them had a hydrophilic character due to the -OH groups in their molecules. The effect of almond skin extracts (ALMOND) on the shelf life of pork patties was compared with the effects of a control without extract (CONTROL NEG) and a control with sodium ascorbate (CONTROL POS). Throughout storage, values of pH, weight loss, headspace composition, color, TBARs and psychrotrophic aerobic bacteria were studied. CONTROL POS samples showed the lowest lipid oxidation values in comparison to CONTROL NEG or ALMOND extract samples.

Influence of almond hulls in lamb diets on animal performance and meat quality

Almond hulls (AH) were fed to lambs to study effects on performance and meat quality. Thirty Sarda lambs were allotted to three experimental groups and fed for 40 days either a cereal-based concentrate diet (control) or diets in which cereals were replaced with 15% (AH15) or 30% (AH30) almond hulls on a DM basis. Diets did not affect final body weight, dry matter intake, average daily gain, feed conversion ratio or carcass weight. Replacing part of the cereal mix (i.e., barley and maize) with AH did not affect meat fatty acid profiles. After 5 and 7 days of refrigerated storage respectively for cooked and raw meat, AH15 and AH30 treatments reduced meat lipid oxidation (P < 0.001). Our results suggest feeding almond hulls up to 30% in fattening lamb diets can improve meat oxidative stability without compromising growth performance.

Effect of roasted peanut allergen Ara h 3 protein on the sensitization of Caco-2 cells

BACKGROUND

Roasted peanut is widely loved as a kind of food with rich taste. However, peanut allergy is one of the major threats to human health, which affects about 5% of children and 1.4-2% of adults in the world.

RESULTS

To evaluate the sensitization mechanism of peanut allergen Ara h 3, Caco-2 cells as the model, which has the similar structure and function to differentiated small intestinal epithelial cells. Compared with Ara h 3-raw (purified from raw peanut) group, more significant results such as the inhibited Caco-2 cell viability and proliferation, the increased secretion of reactive oxygen species (ROS) and the decreased transepithelial electrical resistance were obtained in Ara h 3-roasted (purified from roasted peanut) group. Accordingly, oxidative stress and NF-κB signaling pathway were more imbalanced, which lead to the increased of thymic stromal lymphopoietin (TSLP), interleukin 6 (IL-6), IL-8 and monocyte chemotactic protein 1 (MCP-1). Then, the gene expression of tight junction proteins ZO-1, occludin and JAM-1 were reduced, which proved that the integrity of the Caco-2 monolayer barrier is severely damaged.

CONCLUSION

These finding identify the mechanisms of the allergenicity of roasted peanut allergy proteins are probably associated with intestinal uptake and cytokine dependent allergies. The aggravated allergic reaction might be caused by the increment of TSLP, IL-6, IL-8 and MCP-1 due to the activated NF-κB signaling pathway, and the enhanced transport of Ara h 3-roasted protein by Caco-2 monolayer. © 2021 Society of Chemical Industry.

Revalorization of Almond By-Products for the Design of Novel Functional Foods: An Updated Review

The search for waste minimization and the valorization of by-products are key to good management and improved sustainability in the food industry. The great production of almonds, based on their high nutritional value as food, especially almond kernels, generates tons of waste yearly. The remaining parts (skin, shell, hulls, etc.) are still little explored, even though they have been used as fuel by burning or as livestock feed. The interest in these by-products has been increasing, as they possess beneficial properties, caused by the presence of different bioactive compounds, and can be used as promising sources of new ingredients for the food, cosmetic and pharmaceutical industry. Additionally, the use of almond by-products is being increasingly applied for the fortification of already-existing food products, but there are some limitations, including the presence of allergens and mycotoxins that harden their applicability. This review focuses on the extraction technologies applied to the valorization of almond by-products for the development of new value-added products that would contribute to the reduction of environmental impact and an improvement in the sustainability and competitiveness of the almond industry.

Almond By-Products: Valorization for Sustainability and Competitiveness of the Industry

The search for waste minimization and the valorization of by-products are key practices for good management and improved sustainability in the food industry. The production of almonds generates a large amount of waste, most of which is not used. Until now, almonds have been used for their high nutritional value as food, especially almond meat. The other remaining parts (skin, shell, hulls, etc.) are still little explored, even though they have been used as fuel by burning or as livestock feed. However, interest in these by-products has been increasing as they possess beneficial properties (caused mainly by polyphenols and unsaturated fatty acids) and can be used as new ingredients for the food, cosmetic, and pharmaceutical industries. Therefore, it is important to explore almond’s valorization of by-products for the development of new added-value products that would contribute to the reduction of environmental impact and an improvement in the sustainability and competitiveness of the almond industry.

Impact of Adding Polysaccharides on the Stability of Egg Yolk/Fish Oil Emulsions under Accelerated Shelf-Life Conditions

Polysaccharides can form interfacial complexes with proteins to form emulsions with enhanced stability. We assessed the effect of adding gum guar or gum arabic to egg yolk/fish oil emulsions. The emulsions were produced using simple or high-pressure homogenization, stored for up to 10 days at 45 °C, and characterized for their particle size and distribution, viscosity, encapsulation efficiency, oxidative stability, and cytotoxicity. Emulsions containing gum guar and/or triglycerides had the highest viscosity. There was no significant difference in the encapsulation efficiency of emulsions regardless of the polysaccharide used. However, emulsions containing gum arabic displayed a bridging flocculation effect, resulting in less stability over time compared to those using gum guar. Emulsions produced using high-pressure homogenization displayed a narrower size distribution and higher stability. The formation of peroxides and propanal was lower in emulsions containing gum guar and was attributed to the surface oil. No significant toxicity toward Caco-2 cells was found from the emulsions over time. On the other hand, after 10 days of storage, nonencapsulated fish oil reduced the cell viability to about 80%. The results showed that gum guar can increase the particle stability of egg yolk/fish oil emulsions and decrease the oxidation rate of omega-3 fatty acids.

Bioactive fractions of Eucalyptus camaldulensis inhibit important foodborne pathogens, reduce listeriolysin O-induced haemolysis, and ameliorate hydrogen peroxide-induced oxidative stress on human embryonic colon cells

Extract of E. camaldulensis was partitioned into aqueous and ethanol fractions by a precipitation and sedimentation-based technique and profiled for phytochemical components. Antimicrobial evaluation yielded inhibitory concentrations of 16-64 and 158-316 µg/mL, and bactericidal concentrations of 32-64 and 316->2528 µg/mL for ethanol and aqueous fractions, respectively. Antioxidant activities evaluated using 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic) acid assays showed IC₅₀ values of 7.07 and 65.67 µg/mL, and 17.96 and 201.3 µg/mL for aqueous and ethanol fractions. Total phenolic content of 9.04 ± 0.26 and 3.58 ± 0.04 GAE/mg fraction, and flavonoid content of 2.07 ± 0.02 and 3.37 ± 0.05 QE/mg fraction were recorded for aqueous and ethanol fractions. At subinhibitory concentrations fractions significantly reduced listeriolysin O-induced haemolysis (p < 0.05), and ameliorated H₂O₂-induced toxicity by 8-23 and 15-83%. Nitrite production reduced by 4-17 and 3-14 µM following fractions treatment. The fractions showed bioactive properties, with oxidative stress amelioratory effects, and could be a potentials source of preservatives and functional food additives.

Genoprotective Properties and Metabolites of β-Glucan-Rich Edible Mushrooms Following Their In Vitro Fermentation by Human Faecal Microbiota

A variety of bioactive compounds, constituents of edible mushrooms, in particular β-glucans, i.e., a group of β-d-glucose polysaccharides abundant in the fungal cell walls, have been linked to immunomodulating, anticancer and prebiotic activities. The aim of the study was the investigation of the genoprotective effects of edible mushrooms produced by Pleurotus eryngii, Pleurotus ostreatus and Cyclocybe cylindracea (Basidiomycota). Mushrooms from selected strains of the species mentioned above were fermented in vitro using faecal inocula from healthy volunteers. The cytotoxic and anti-genotoxic properties of the fermentation supernatants (FSs) were investigated in Caco-2 human colon adenocarcinoma cells. The FSs were cytotoxic in a dose-dependent manner. Non-cytotoxic concentrations were used for the genotoxicity studies, which revealed that mushrooms’ FSs have the ability to protect Caco-2 cells against tert-butyl hydroperoxide (t-BOOH), a known genotoxic agent. Their global metabolic profiling was assessed by ¹H-NMR spectroscopy. A total of 37 metabolites were identified with the use of two-dimensional (2D) homo- and hetero-nuclear NMR experiments. Multivariate data analysis monitored the metabolic variability of gut microbiota and probed to biomarkers potentially associated with the health-promoting effects of edible mushrooms.