Hazelnut skin as an industrial coproduct: Novel source of polyphenols and dietary fibre for functional food applications and health benefits
Global hazelnut production generates significant quantities of skin, an underutilized coproduct currently restricted to low-value applications despite its rich bioactives, dietary polypehnols, and dietary fibres. Valorising this residue aligns with circular economy principles by transforming agro-industrial waste into high-value resources. Hazelnut skin is identified as an exceptional source of dietary fibre (∼70%), vitamin E, and dietary polyphenols, exhibiting antioxidant activity significantly superior to hazelnut kernel. Its unique fibre composition, particularly specific pectin and xyloglucan structures, has been proposed, primarily based on in vitro and animal studies, to contribute to prebiotic-like effects. These proposed mechanisms include the stimulation of certain microbial genera (e.g., Prevotella and Lactobacillus) and increased short-chain fatty acid production; however, these structure–function relationships remain hypothetical and require validation in human studies. Furthermore, hazelnut skin serves as a novel source of functional ingredient in a range of food matrices, including bakery, dairy, beverage, and meat products, among others. Overall, the evidence suggests that that hazelnut skin represents a promising and sustainable functional ingredient, the valorisation of which may support gut health-related benefits while contributing to the development of circular and resource-efficient food systems. This review critically examines the current knowledge on the chemical composition, functional properties, technological applications, and health-related benefits of hazelnut skin, with particular emphasis on modulation of colonic microbiota, providing a foundation for future research exploring its novel applications in functional food development.
https://doi.org/10.1016/j.foodchem.2026.148851
Rethinking the ageing process of spirits: Nutshells as a sustainable alternative to wood
Aguardente bagaceira, a Portuguese grape marc spirit (GMS), represents an opportunity for sustainable innovation in ageing process. This study investigates the use of nutshells (almond, hazelnut, walnut, chestnut) as alternative ageing materials to conventional wood. Spirits were aged for six months in 20 L stainless steel vessels (50 g/L, chestnut tested at 12.5 and 25 g/L). An unaged sample and oak wood chips served as controls. Total phenolics (TPC), tannins (TAN), flavonoids (TF), pH, acidity, dry extract, and chromatic characteristics were monitored monthly. GMS aged with chestnut shells showed the highest levels of TPC (2.02 ± 0.17 g GAE/L), TAN (1.91 ± 0.07 g/L) and TF (0.250 ± 0.007 g CE/L) among the tested materials. Sensory analysis highlighted enhanced flavour complexity in chestnut-aged GMS after three months. These results demonstrate the potential of nutshells as sustainable, circular-economy alternatives to oak in spirit ageing, reducing ageing time without compromising quality.
https://doi.org/10.1016/j.foodchem.2026.147899
Physically crosslinked polyphenol-chitosan edible coating for the application of walnut kernels during roasting
This study developed an edible chitosan-based coating incorporating the main polyphenols from walnut kernel seed coats (gallic acid, ferulic acid, and ellagic acid) to enhance the oxidative stability and sensory quality of fresh walnut kernels during roasting. SEM and AFM analysis revealed that gallic acid-loaded chitosan films exhibited a uniform yet rough morphology, while zeta potential measurements (36-41 mV) confirmed improved film stability. The gallic acid-loaded film demonstrated superior wettability (contact angle: 21.45°) and low water vapor permeability (2.87 × 10-3 g/(mm∙h∙kPa)), ensuring strong adhesion. FTIR and UV-Vis analyses confirmed hydrogen-bonded crosslinking between polyphenols and chitosan. Thermal stability increased, with DSC and TGA peaks at 181.97 °C and 343 °C for the gallic acid-loaded film. Coated kernels exhibited significantly lower oxidation, with peroxide and acid values (0.04 g/100 g, 0.5 mg/g) outperforming uncoated samples. These findings suggested that gallic acid-loaded chitosan coatings effectively improve walnut kernel quality during roasting.
https://doi.org/10.1016/j.foodchem.2026.147846
Cashew nut protein concentrate as a potential ingredient for the emerging alternative protein industry
This study evaluated protein concentrates obtained from cashew nuts defatted by three different strategies: mechanical pressing (PE), hexane extraction (HE), and aqueous extraction (AE). Protein concentrates (PC-A, PC-P, and PC-H, from AE, PE, and HE, respectively) were produced through alkaline extraction followed by isoelectric precipitation. PCs were characterized for protein functionality, nutritional and chemical profiling. Protein contents were 59.34 % (PC-P), 85.45 % (PC-H), and 69.02 % (PC-A). All samples had high in vitro digestibility, above 90 %, and a balanced amino acid profile. Maximum protein solubility was achieved for all PCs at pH 8 and above (>50 %). PC-A showed superior oil-holding capacity and emulsifying capacity, similar gelation properties and reduced water holding capacity when compared to the other PCs. Overall, AE emerges as an ecofriendly alternative for producing high-quality cashew protein concentrate with less environmental impact than HE, while hexane extraction remains the most efficient method for oil removal.
https://doi.org/10.1016/j.foodchem.2025.146855
Deciphering metabolomics modulations in peanut induced by nonthermal plasma: A quasi-targeted approach
Nonthermal plasma (NTP) is a promising food processing technology that enhances food safety and quality while preserving nutrition. This study used a novel quasi-targeted metabolomics approach to analyze NTP's effects on peanuts (Arachis hypogaea) under three treatment conditions (90, 270, 450 s at 160 kV, 150 Hz) and a control. The quasi-targeted method combines the strengths of targeted and untargeted metabolomics, offering high throughput, extensive coverage, and increased sensitivity. Of 1175 identified metabolites, 247 were significantly altered (135 upregulated, 112 downregulated). Key findings include upregulation of antioxidants like ascorbic acid (+23 %) and naringenin (+18 %) and markers of lipid peroxidation such as malondialdehyde (+42 %) and 4-hydroxy-2-nonenal (+30 %), indicating oxidative stress. Notably, Sulfur-containing amino acids, such as L-cysteine (+15 %) and homocysteine (+18 %), emerged as novel biomarkers for NTP-induced oxidative stress. Moderate treatment (270 s) enhanced antioxidant levels and maintained membrane integrity, whereas prolonged exposure (450 s) caused excessive oxidative stress, leading to nutrient degradation and protein oxidation. PCA and pathway analysis revealed changes in energy metabolism, amino acid biosynthesis, and secondary metabolites. These findings underscore NTP's potential to enhance peanut nutritional quality and shelf life, but the treatment must be optimized to balance its benefits with oxidative damage. Additionally, this study introduces sulfur-containing amino acids as innovative biomarkers for oxidative stress, offering new directions for monitoring NTP treatment effects and guiding industrial applications.
https://doi.org/10.1016/j.foodchem.2025.145156
Meeting the challenge of varietal and geographical authentication of hazelnuts through lipid metabolite fingerprinting
Hazelnuts are high-quality products with significant economic importance in many European countries. Their market price depends on their qualitative characteristics, which are driven by cultivar and geographical origin, making hazelnuts susceptible to fraud. This study systematically compared two lipidomic fingerprinting strategies for the simultaneous authentication of hazelnut cultivar and provenance, based on the analysis of the unsaponifiable fraction (UF) and triacylglycerol (TAG) profiles by gas chromatography-mass spectrometry coupled with chemometrics. PLS-DA classification models were developed using a large sample set with high natural variability (n = 309) to discriminate hazelnuts by cultivar and origin. External validation results demonstrated the suitability of the UF fingerprint as a hazelnut authentication tool, both tested models showing a high efficiency (>94 %). The correct classification rate of the TAG fingerprinting method was lower (>80 %), but due to its faster analysis time, it is recommended as a complementary screening tool to UF fingerprinting.
https://doi.org/10.1016/j.foodchem.2024.141203
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.
https://doi.org/10.1016/j.foodchem.2024.142222
Pistachio (Pistacia vera L.) consumption improves cognitive performance and mood in overweight young adults: A pilot study
This pilot study evaluated the impact of pistachio consumption on cognitive performance and mood in overweight young adults. Pistachios were characterized (chemical and nutraceutical), and a baseline-final, uncontrolled nutritional intervention was performed (28 g of pistachio/28 days). Psychometric tests were applied to estimate cognitive performance and mood; anthropometric evaluation, biochemical analysis, and plasma antioxidant activity were included. The main component of nuts was lipids (48.1%). Pistachios consumption significantly (p ≤ 0.05) reduced waist circumference (−1.47 cm), total cholesterol (−10.21 mg/dL), LDL (−6.57 mg/dL), and triglycerides (−21.07 mg/dL), and increased plasma antioxidant activity. Pistachio supplementation improved risk tolerance (p ≤ 0.006) and decision-making strategy (p ≤ 0.002; BART-task), executive functions (BCST-task; p ≤ 0.006), and selective and sustained attention (Go/No-Go-test; p ≤ 0.016). The mood state was positively modulated (p ≤ 0.05) for anxiety, anger-hostility, and sadness-depression. These results show for the first time the benefits of pistachio consumption on cognitive performance and mood in overweight young adults. https://doi.org/10.1016/j.foodchem.2024.140211
Extraction of bioactive compounds from pecan nutshell: An added-value and low-cost alternative for an industrial waste
The pecan nutshell [Carya illinoinensis (Wangenh) C. Koch] (PNS) is a source of bioactives with important beneficial properties for the human health. PNS represents between 40-50 % of total mass of the nut, resulting as waste without any added value for the food industry. Even though a variety of methods were already developed for bioactive extraction from this waste, unconventional methodologies, or those which apart from green chemistry principles, were discarded considering the cost of production, the sustainable development goals of United Nations and the feasibility of real inclusion of the technology in the food chain. Then, to add-value to this waste, a low-cost, green and easy-scalable extraction methodology was developed based on the determination of seven relevant factors by means of a factorial design and a Response Surface Methodology, allowing the extraction of bioactives with antioxidant capacity. The pecan nutshell extract had a high concentration of phenolic compounds (166 mg gallic acid equivalents-GAE/g dry weight-dw), flavonoids (90 mg catechin equivalent-CE/g dw) and condensed tannins (189 mg CE/g dw) -related also to the polymeric color (74.6 %)-, with high antioxidant capacities of ABTS+. radical inhibition (3665 µmol Trolox Equivalent-TE/g dw) and of iron reduction (1305 µmol TE/g dw). Several compounds associated with these determinations were identified by HPLC-ESI-MS/MS, such as [Epi]catechin-[Epi]catechin-[Epi]gallocatechin, myricetin, dihydroquercetins, dimers A and B of protoanthocyanidins, ellagitannins and ellagic acid derivatives. Hence, through the methodology developed here, we obtained a phenolic rich extract with possible benefits for human health, and of high industrial scalability for this co-product transformation. https://doi.org/10.1016/j.foodchem.2024.139596
Effects of enzymatic hydrolysis combined with pressured heating on tree nut allergenicity
Hazelnut, pistachio and cashew are tree nuts with health benefits but also with allergenic properties being prevalent food allergens in Europe. The allergic characteristics of these tree nuts after processing combining heat, pressure and enzymatic digestion were analyzed through in vitro (Western blot and ELISA) and in vivo test (Prick-Prick). In the analyzed population, the patients sensitized to Cor a 8 (nsLTP) were predominant over those sensitized against hazelnut seed storage proteins (Sprot, Cor a 9 and 14), which displayed higher IgE reactivity. The protease E5 effectively hydrolyzed proteins from hazelnut and pistachio, while E7 was efficient for cashew protein hydrolysis. When combined with pressured heating (autoclave and Controlled Instantaneous Depressurization (DIC)), these proteases notably reduced the allergenic reactivity. The combination of DIC treatment before enzymatic digestion resulted in the most effective methodology to drastically reduce or indeed eliminate the allergenic capacity of tree nuts.
https://doi.org/10.1016/j.foodchem.2024.139433