Progress and challenges in valorisation of biomass waste from ornamental trees pruning through pyrolysis processes. Prospects in the bioenergy sector.

Nowadays, the scarcity of energy resources is promoting the search for alternative energy sources, boosting interest in the use of forest lignocellulosic residue in the energy sector. In this study, the focus is on the energy recovery from two lignocellulosic residues originated during the pruning of ornamental trees (Horse Chestnut, CI, and False Acacia, FA). Both conventional and flash pyrolysis techniques were applied. The experimental pyrolysis variables were obtained from the study of the thermal behaviour of the pruning residues in thermogravimetric analysis. It was carried out under 5 heating rates and kinetic parameters were estimated using Flynn-Wall-Ozawa method. Results denoted higher maximum mass loss rate values for the same release temperature regions under FA experiments. Also, FA samples had lower final residues for the processes. However, activation energy values were so close for both species. FA was also linked to the faster reactions according frequency factor outcomes. Conventional pyrolysis of pruning residues was carried out in a horizontal oven of original design at a heating rate of 25 °C/min, at 750 °C and 60 min of permanence at that temperature; flash pyrolysis was tested in that oven at 750 and 850 °C. In these pyrolysis processes, three fractions were obtained: bio-char, bio-oil and gas. The physicochemical attributes of the bio-chars suggested their potential utility as biofuels (28.4-29.8 MJ/kg), adsorbent precursors or soil additives. Conventional pyrolysis bio-oils had a dominant monoaromatic hydrocarbons nature, with phenols being the most abundant (≥60%), while flash bio-oils contain mainly polycyclic aromatic hydrocarbons. Conventional pyrolysis gases contained up to 60 vol% of CO2; flash pyrolysis gases had high combustible gas content (CO, CH4, H2) and a low CO2 content (<25 vol%). As a result, their calorific value (18.06 MJ/kg) exhibited a threefold increase compared to the gas produced through conventional pyrolysis (6.04 MJ/kg).

The use of artificial neural network for modelling adsorption of Congo red onto activated hazelnut shell.

Activated hazelnut shell (HSAC), an organic waste, was utilized for the adsorptive removal of Congo red (CR) dye from aqueous solutions, and a modelling study was conducted using artificial neural networks (ANNs). The structure and characteristic functional groups of the material were examined by the FTIR method. The BET surface area of the synthesized material, named HSAC, was 812 m2/g. Conducted in a batch system, the adsorption experiments resulted in a notable removal efficiency of 87% under optimal conditions. The kinetic data for hazelnut shell activated carbon (HSAC) removal of CR were most accurately represented by the pseudo-second-order kinetic model (R2 = 0.998). Furthermore, the equilibrium data demonstrated a strong agreement with the Freundlich model. The maximum adsorption capacity of HSAC for CR was determined to be 34.8 mg/g. The optimum adsorption parameters were determined to be pH 6, contact time of 60 min, 10 g/L of HSAC, and a concentration of 400 mg/L for CR. Considering the various experimental parameters influencing CR adsorption, an artificial neural network (ANN) model was constructed. The analysis of the ANN model revealed a correlation of 98%, indicating that the output parameter could be reliably predicted. Thus, it was concluded that ANN could be employed for the removal of CR from water using HSAC.

Characterization of phenolic constituents in hazelnut kernels.

Hazelnuts contain biologically active phenolic compounds and are widely used for their nutritional value. In this study, the phenolic compounds contained in hazelnuts were isolated from the kernels of Corylus avellana L. and investigated. Spectral analyses revealed 2 new acetophenone glycosides, characterized as 2',4',6'-trihydroxyacetophenone-4'-O-(2-O-ß-d-apiosyl)-ß-d-glucoside and 2',4',6'-trihydroxyacetophenone-4'-O-(2-O-ß-d-apiosyl-6-O-α-l-arabinosyl)-ß-d-glucoside, and 4 known compounds. Four high-molecular-mass condensed tannin fractions were detected in the water-soluble fraction of the extract, characterized as B-type procyanidin consisting of extension and terminal units. Gel permeation chromatography analyses revealed that the average molecular mass, based on the polystyrene standard, was approximately 15 000-113 000. These high-molecular-mass condensed tannin fractions were chemically characterized and exhibited different molecular weights. The fractions of high-molecular-mass condensed tannins were obtained from hazelnuts and tested for 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity. The EC50 values indicated significant activity for all the fractions.

Hazelnut (Corylus avellana L.) shells as a potential source of dietary fibre: impact of hydrothermal treatment temperature on fibre structure and degradation compounds.

BACKGROUND: Hemicellulose extraction from lignocellulosic biomasses has gained interest over the years, and hydrothermal treatment is one of the most common methods employed for this purpose. This work aimed to deeply study hazelnut (Corylus avellana L.) shells as a new source of dietary fibre, evaluating the effect of hydrothermal treatment temperatures on the type and structure of fibre extracted, but also on the formation of side-products derived from lignocellulose degradation. RESULTS: Different process temperatures led to diverse polysaccharides in the hydrothermal extract. Pectin was identified for the first time in hazelnut shells when experimenting with extraction at 125 °C, whereas at 150 °C a heterogeneous mixture of pectin, xylan, and xylo-oligosaccharides was present. The highest yield in terms of total fibre was gained at 150 and 175 °C, and then decreased again at 200 °C. Finally, more than 500 compounds from different chemical classes were putatively identified and they appeared to be present in the extracted fibre with a different distribution and relative amount, depending on the heat treatment severity. A generally high content of phenols, phenyls, oligosaccharides, dehydro-sugars, and furans was observed. CONCLUSIONS: Modulation of the hydrothermal treatment temperature allows fibre extracts with very different compositions, and therefore different potential end uses, to be obtained from hazelnut shells. A sequential temperature-based fractionation approach, as a function of the severity of the extraction parameters, can also be considered. Nevertheless, the study of the side-compounds formed from lignocellulosic matrix degradation, as a function of the applied temperature, needs to be fully addressed for a safe introduction of the fibre extract within the food chain. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

On the Traceability of the Hazelnut Production Chain by Means of Trace Elements.

The production chain of hazelnuts has been studied by analyzing three sets of samples produced in purity from three different pools of hazelnuts of cultivar "Tonda Gentile Trilobata", "Tonda Gentile Romana" and "Mortarella", all cultivated in Italy. From each pool, five processed products were obtained: roasted hazelnuts, hazelnut paste, hazelnut cream, Gianduja paste and Gianduiotto paste. After pre-treatment by means of dry ashing, all samples from each cultivar, including raw hazelnuts, were then analyzed by means of Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). A good discrimination was obtained among the different chain stages according to the distribution of the trace elements, as expected. More interesting was the discrimination among the different cultivars: it was possible to distinguish the samples produced from the respective cultivar by means of specific chemical markers, particularly Mo and Ni.

Giffonins, Antioxidant Diarylheptanoids from Corylus avellana, and Their Ability to Prevent Oxidative Changes in Human Plasma Proteins.

With the aim to explore the ability of diarylheptanoids to reduce oxidative changes in human plasma proteins, a phytochemical investigation of the MeOH extract of Corylus avellana leaves was perfomed. Analysis by LC-ESI/LTQOrbitrap/MS/MSn guided the isolation of two new diarylheptanoid derivatives, giffonins W (1) and X (2). The structures 1 and 2 were assigned by analysis of NMR data combined with a QM (quantum mechanical)/NMR approach. The absolute configurations of 1 and 2 were established by analysis of electronic circular dichroism (ECD) spectra compared with the TDDFT-simulated curves. The antioxidant activity of the new and known giffonins was evaluated by inhibition of human plasma lipid peroxidation. Giffonins with the highest inhibitory activity were tested for their ability to reduce oxidation of thiol groups and carbonylation in plasma proteins, and some of them exhibited higher antioxidant activity than curcumin.

Effect of sequential pretreatment combinations on the composition and enzymatic hydrolysis of hazelnut shells.

Hazelnut shells, a high lignin containing biomass, were subjected to individual and sequential liquid hot water (LHW), alkaline (AP) and dilute acid pretreatments (DAP). Among the single pretreatments, LHW demonstrated the highest cellulose recovery of 98.1%, DAP resulted in the highest hemicellulose solubilization of 56.0%, and AP of the highest lignin removal of 49.6%. Employing two-step pretreatment on hazelnut shells, in general, demonstrated an enhanced action of the second pretreatment; therefore, the sequence of the pretreatment methods had a significant impact on both substrate characteristics and enzymatic hydrolysis efficiency of biomass. In terms of delignification, AP-LHW achieved 60.7% lignin removal, while LHW-DAP showed the highest hemicellulose removal of 93.8% and DAP-LHW resulted in the highest cellulose recovery of 94.0%. Structural properties of raw and pretreated hazelnut shells were observed by FTIR. The maximum glucose recovery of 54.9% was observed in DAP-LHW pretreated samples. For this pretreatment combination, almost 1.8 MJ total energy was required to recover 10.2 g glucose. The findings indicated that complete removal of the physical barrier of lignin and hemicellulose might not be essential; partial relocation of lignin and alteration of cellulose structure may also be efficient in increasing the sugar recovery from the lignocellulosic biomass.

Effect of Sample Preparation on the Detection and Quantification of Selected Nuts Allergenic Proteins by LC-MS/MS.

The detection and quantification of nut allergens remains a major challenge. The liquid chroma-tography tandem mass spectrometry (LC-MS/MS) is emerging as one of the most widely used methods, but sample preparation prior to the analysis is still a key issue. The objective of this work was to establish optimized protocols for extraction, tryptic digestion and LC-MS analysis of almond, cashew, hazelnut, peanut, pistachio and walnut samples. Ammonium bicar-bonate/urea extraction (Ambi/urea), SDS buffer extraction (SDS), polyvinylpolypyrroli-done (PVPP) extraction, trichloroacetic acid/acetone extraction (TCA/acetone) and chloro-form/methanol/sodium chloride precipitation (CM/NaCl) as well as the performances of con-ventional tryptic digestion and microwave-assisted breakdown were investigated. Overall, the protein extraction yields ranged from 14.9 ± 0.5 (almond extract from CM/NaCl) to 76.5 ± 1.3% (hazelnut extract from Ambi/urea). Electrophoretic profiling showed that the SDS extraction method clearly presented a high amount of extracted proteins in the range of 0-15 kDa, 15-35 kDa, 35-70 kDa and 70-250 kDa compared to the other methods. The linearity of the LC-MS methods in the range of 0 to 0.4 µg equivalent defatted nut flour was assessed and recovery of internal standards GWGG and DPLNV(d8)LKPR ranged from 80 to 120%. The identified bi-omarkers peptides were used to relatively quantifier selected allergenic protein form the inves-tigated nut samples. Considering the overall results, it can be concluded that SDS buffer allows a better protein extraction from almond, peanut and walnut samples while PVPP buffer is more appropriate for cashew, pistachio and hazelnut samples. It was also found that conventional overnight digestion is indicated for cashew, pistachio and hazelnut samples, while microwave assisted tryptic digestion is recommended for almond, hazelnut and peanut extracts.

Hazelnut Shells as Source of Active Ingredients: Extracts Preparation and Characterization.

Hazelnut shells represent a waste material (about 42% of the total biomass) deriving from hazelnut harvest. These are mainly used as a heating source; however, they represent an interesting source of polyphenols useful in health field. The impact on phenolic profile and concentrations of hazelnut shell extracts obtained by three extraction methods (maceration, ultrasonic bath, and high-power ultrasonic), as well as temperature, extraction time, and preventive maceration, was studied. The prepared extracts were characterized in terms of chemical composition, antioxidant and antimicrobial activities. Eighteen different phenolic compounds were identified and quantified by chemical analysis and gallic acid was the most abundant in all the extracts analyzed. Other relevant compounds were chlorogenic acid, protocatechuic acid and catechin. Preventive maceration had a positive effect on the extraction of different types of compounds regardless of the method performed. Application of the high-power ultrasonic method had different effects, either positive or negative, depending on the type of compound and extraction time. All the prepared extracts showed antioxidant activity especially those prepared by maceration, and many of them were able to inhibit the growth of both B. subtilis and B. cereus.

Advances in cultivar choice, hazelnut orchard management, and nut storage to enhance product quality and safety: an overview.

European hazelnut (Corylus avellana L.) is a major species of interest for nutritional use within the Betulaceae family and its nuts are widely used throughout the world in the chocolate, confectionery, and bakery industries. Recently its cultivation has been expanded in traditional producer countries and established in new places in the southern hemisphere, including Chile, South Africa, and Australia. Introducing hazelnut in new environments could reduce its productivity, lead the trees to experience eco-physiological disorders, and expose the crop to high pressure from common and new pests and diseases. Thus, new approaches in cultivar choice guidance, in the sustainable orchard management and even in nut storage and kernel quality evaluation are urgently required to improve the hazelnut production and processing chain. The main objective of this study was to systematize the published information regarding recent findings about the cultural operations that directly influence nut and kernel quality, support varietal choice for new plantations, and list the recent advances in nut storage and in quality and safety evaluation. © 2020 Society of Chemical Industry.

Kaolin, Ascophyllum nodosum and salicylic acid mitigate effects of summer stress improving hazelnut quality.

BACKGROUND: Various strategies are needed to mitigate the negative impact on or to increase fruit quality. The effect of spraying kaolin (K), Ascophyllum nodosum (An) and salicylic acid (SA), in trees with and without irrigation, on quality and sensorial attributes of hazelnut (Grada de Viseu cultivar) was investigated during two consecutive years (2016 and 2017) in a commercial orchard located in Moimenta da Beira, Portugal. RESULTS: The treatments affected positively the biometric parameters nut and kernel weight, length, width, thickness and volume as well as the vitamin E level, antioxidant activity and content of some individual phenolics, such as protocatechuic acid, gallocatechin, catechin and epicatechin. The levels of amino acids in hazelnut kernels decreased in all the assayed treatments, while the kernel colour and sensorial attributes were not affected by the treatments. Hazelnut physical properties (nut and kernels), chemical and phytochemical composition and antioxidant activities were positively related. CONCLUSIONS: The application of K, An and SA improved the hazelnut tree response to climate change, without compromising the hazelnut chemical and sensorial quality. Furthermore, due to the similar observations for the same treatments with and without irrigation, it can be stated that K, An and SA can be efficient and cost-effective tools to mitigate summer stress in rain-fed orchards. © 2020 Society of Chemical Industry.

High porosity with tiny pore constrictions and unbending pathways characterize the 3D structure of intervessel pit membranes in angiosperm xylem.

Pit membranes between xylem vessels play a major role in angiosperm water transport. Yet, their three-dimensional (3D) structure as fibrous porous media remains unknown, largely due to technical challenges and sample preparation artefacts. Here, we applied a modelling approach based on thickness measurements of fresh and fully shrunken pit membranes of seven species. Pore constrictions were also investigated visually by perfusing fresh material with colloidal gold particles of known sizes. Based on a shrinkage model, fresh pit membranes showed tiny pore constrictions of ca. 20 nm, but a very high porosity (i.e. pore volume fraction) of on average 0.81. Perfusion experiments showed similar pore constrictions in fresh samples, well below 50 nm based on transmission electron microscopy. Drying caused a 50% shrinkage of pit membranes, resulting in much smaller pore constrictions. These findings suggest that pit membranes represent a mesoporous medium, with the pore space characterized by multiple constrictions. Constrictions are much smaller than previously assumed, but the pore volume is large and highly interconnected. Pores do not form highly tortuous, bent, or zigzagging pathways. These insights provide a novel view on pit membranes, which is essential to develop a mechanistic, 3D understanding of air-seeding through this porous medium.

Metabolomics and hormonomics to crack the code of filbert growth.

INTRODUCTION: Plants respond to changes in their environments through hormonal activation of a physiological cascade that redirects metabolic resources and growth. In filberts (Corylus sp.), chelated iron promotes the growth of new shoots but the mechanism(s) are not understood. OBJECTIVES: To use untargeted metabolomics and hormonomics approaches to generate novel hypotheses for the morphoregulatory role of ferric ethylenediamine-N,N'-di-(ortho-hydroxyphenyl) acetic acid (Fe-EDDHA) in filbert shoot organogenesis in vitro. METHODS: Data were generated using previously optimized standardized untargeted metabolomics protocols with time of flight mass spectrometry. Multivariate statistical tools (principal component and partial least squares discriminant analysis) did not detect significant differences. Discovery tools Significance Analysis of Microarrays (SAM), multiple linear regression analysis, Bayesian analysis, logical algorithms, machine learning, synthetic biotransformations, targeted hormonomics, and online resources including MetaboAnalyst were used. RESULTS: Starch/sucrose metabolism and shikimate pathway metabolites were increased. Dose dependent decreases were found in polyphenol metabolism, specifically ellagic acid and its methylated derivative 3,4,3'-tri-O-methylellagic acid. Hormonomics analysis revealed significant differences in phytohormones and their conjugates. FeEDDHA treatment reduced indole-3-acetic acid, abscisic acid, salicylic acid, jasmonic acid conjugates (JA-Trp, JA-Ile, OH-JA) and dihydrozeatinglucoside in regenerating explants. Serotonin (5HT) was decreased in FeEDDHA-treated regenerating tissues while the related metabolite melatonin was increased. Eight phenolic conjugates of 5HT and eight catabolites were affected by FeEDDHA indicating that metabolism to sequester, deactivate and metabolize 5HT was induced by Fe(III). Tryptophan was metabolized through kynurenine but not anthranilate. CONCLUSION: Seven novel hypotheses were generated to guide future studies to understand the regulatory control(s) of shoot organogenesis.

IgE cross-reactivity measurement of cashew nut, hazelnut and peanut using a novel IMMULITE inhibition method.

Background Tree nut-allergic individuals are often sensitised towards multiple nuts and seeds. The underlying cause behind a multi-sensitisation for cashew nut, hazelnut, peanut and birch pollen is not always clear. We investigated whether immunoglobulin E antibody (IgE) cross-reactivity between cashew nut, hazelnut and peanut proteins exists in children who are multi-allergic to these foods using a novel IMMULITE®-based inhibition methodology, and investigated which allergens might be responsible. In addition, we explored if an allergy to birch pollen might play a role in this co-sensitisation for cashew nut, hazelnut and peanut. Methods Serum of five children with a confirmed cashew nut allergy and suffering from allergic symptoms after eating peanut and hazelnut were subjected to inhibition immunoassays using the IMMULITE® 2000 XPi. Serum-specific IgE (sIgE) to seed storage allergens and pathogenesis-related protein 10 (PR10) allergens were determined and used for molecular multicomponent allergen correlation analyses with observed clinical symptoms and obtained inhibition data. Results IgE cross-reactivity was observed in all patients. Hazelnut extract was a strong inhibitor of cashew nut sIgE (46.8%), while cashew nut extract was less able to inhibit hazelnut extract (22.8%). Peanut extract showed the least inhibition potency. Moreover, there are strong indications that a birch pollen sensitisation to Bet v 1 might play a role in the observed symptoms provoked upon ingestion of cashew nut and hazelnut. Conclusions By applying an adjusted working protocol, the IMMULITE® technology can be used to perform inhibition assays to determine the risk of sIgE cross-reactivity between very different food components.

Lignins from Agroindustrial by-Products as Natural Ingredients for Cosmetics: Chemical Structure and In Vitro Sunscreen and Cytotoxic Activities.

The growing concern about the environmental impact and human health risk related to the excessive use of synthetic ingredients in cosmetics and topical formulations calls for the exploration of safe and sustainable natural alternatives. Lignin-rich lignocellulosic industrial wastes such as hazelnut and walnut shells were used as a lignin polymer source. Agro-derived lignins were evaluated as a potential natural active ingredient for health care products. Aside from the structural characteristics of isolated lignins, which were identified by GPC, Py-GC-MS, and 2D HSQC NMR techniques, functional properties such as antioxidant power and UV absorption ability were investigated. The SPF values found for creams containing 5% of hazelnut and walnut lignin content were 6.9 and 4.5, respectively. Additionally, both lignin types presented appropriate protection against UVA radiation, highly interesting property to block the full ultraviolet spectrum. The biological activity of isolated lignins assessed at different concentrations (0.01-1 mg/mL) and different times (24, 48, and 72 h) on murine fibroblast cell line 3T3 suggested their suitability for cosmetic applications.

Synthesis and Matrix Properties of α-Cyano-5-phenyl-2,4-pentadienic Acid (CPPA) for Intact Proteins Analysis by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry.

The effectiveness of a synthesized matrix, α-cyano-5-phenyl-2,4-pentadienic acid (CPPA), for protein analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in complex samples such as foodstuff and bacterial extracts, is demonstrated. Ultraviolet (UV) absorption along with laser desorption/ionization mass spectrometry (LDI-MS) experiments were systematically conducted in positive ion mode under standard Nd:YLF laser excitation with the aim of characterizing the matrix in terms of wavelength absorption and proton affinity. Besides, the results for standard proteins revealed that CPPA significantly enhanced the protein signals, reduced the spot-to-spot variability and increased the spot homogeneity. The CPPA matrix was successful employed to investigate intact microorganisms, milk and seed extracts for protein profiling. Compared to conventional matrices such as sinapinic acid (SA), α-cyano-4-hydroxycinnamic acid (CHCA) and 4-chloro-α-cyanocinnamic acid (CClCA), CPPA exhibited better signal-to-noise (S/N) ratios and a uniform response for most examined proteins occurring in milk, hazelnut and in intact bacterial cells of E. coli. These findings not only provide a reactive proton transfer MALDI matrix with excellent reproducibility and sensitivity, but also contribute to extending the battery of useful matrices for intact protein analysis.

Design and Development of Spray-Dried Microsystems to Improve Technological and Functional Properties of Bioactive Compounds from Hazelnut Shells.

An extract obtained from hazelnut shells by-products (HSE) has antioxidant and chemopreventive effects on human melanoma and cervical cancer cell lines, inducing apoptosis by caspase-3 activation. A clinical translation is limited by poor water solubility and low bioavailability. Dried plant extracts often show critical characteristics such as sticky/gummy appearance, unpleasant smell, and instability involving practical difficulties in processing for industrial use. A spray drying method has been applied to transform raw HSE in a microparticulate powder. The biopolymeric matrix was based on l-proline as loading carrier, hydroxyethylcellulose in combination with pectin as coating polymers; lecithin and ethanol were used as solubility enhancers. A Hot-Cold-Hot method was selected to prepare the liquid feed. The thus prepared powder showed good technological properties (solid-state, particle dimensions, morphology, and water dissolution rate), stability, and unchanged chemopreventive effects with respect to the unprocessed HSE.

Untargeted metabolomics with multivariate analysis to discriminate hazelnut (Corylus avellana L.) cultivars and their geographical origin.

BACKGROUND: In the present study a metabolomics-based approach was used to discriminate among different hazelnut cultivars and to trace their geographical origins. Ultra-high-pressure liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UHPLC-ESI/QTOF-MS) was used to profile phenolic and sterolic compounds. RESULTS: Compounds were identified against an in-house database using accurate monoisotopic mass and isotopic patterns. The screening approach was designed to discern 15 hazelnut cultivars and to discriminate among the geographical origins of six cultivars from the four main growing regions (Chile, Georgia, Italy, and Turkey). This approach allowed more than 1000 polyphenols and sterols to be annotated. The metabolomics data were elaborated with both unsupervised (hierarchical clustering) and supervised (orthogonal projections to latent structures discriminant analysis, OPLS-DA) statistics. These multivariate statistical tools allowed hazelnut samples to be discriminated, considering both 'cultivar type' and 'geographical origin'. Flavonoids (anthocyanins, flavanols and flavonols - VIP scores 1.34-1.49), phenolic acids (mainly hydroxycinnamics - VIP scores 1.35-1.55) together with cholesterol, ergosterol, and stigmasterol derivatives (VIP scores 1.34-1.49) were the best markers to discriminate samples according to geographical origin. CONCLUSIONS: This work illustrates the potential of untargeted profiling of phenolics and sterols based on UHPLC-ESI/QTOF mass spectrometry to discriminate hazelnut and support authenticity and origin. © 2019 Society of Chemical Industry.

Signal pattern plot: a simple tool for time-dependent metabolomics studies by 1H NMR spectroscopy.

We show an alternative way to visualize time course NMR data without the application of multivariate data analysis, based on the temporal change of the metabolome of hazelnuts after mold infestation. Fresh hazelnuts were inoculated with eight different natural mold species and the growth was studied over a period of 14 days. The data were plotted in a color-coded scheme showing metabolic changes as a function of chemical shift, which we named signal pattern plot. This plot graphically displays alteration (trend) of a respected signal over time and allows visual interpretation in a simple manner. Changes are compared with a reference sample stored under identical conditions as the infected nuts. The plot allows, at a glance, the recognition of individual landmarks specific to a sample group as well as common features of the spectra. Each sample reveals an individual signal pattern. The plot facilitates the recognition of signals that belong to biological relevant metabolites. Betaine and five signals were identified that specifically changed upon mold infestation. Graphical abstract.

Plant Specialized Metabolites in Hazelnut (Corylus avellana) Kernel and Byproducts: An Update on Chemistry, Biological Activity, and Analytical Aspects.

Corylus avellana (hazelnut) is one of the most popular tree nuts on a worldwide basis. The main products of C. avellana are kernels, a nutritious food, with a high content of healthy lipids, contained in a hard shell. In recent years, along with the ongoing research carried out on hazelnut kernels, a growing interest has been addressed to the hazelnut byproducts including hazelnut skin, hazelnut hard shell, and hazelnut green leafy cover as well as hazelnut tree leaf. These byproducts deriving from the roasting, cracking, shelling/hulling, and harvesting processes have been found as a source of "phytochemicals" with biological activity. The aim of this review is to provide a comprehensive and critical update on the chemistry and biological activity of specialized metabolites occurring in hazelnut kernels and byproducts. Phenolics are the most abundant phytochemicals not only in the kernels, but also in other processing byproducts. Attention has been also devoted to taxane derivatives isolated from C. avellana leaves. An overview on the biological activity, mainly antioxidant, antiproliferative, and antimicrobial along with less common biological effects, has been provided, contributing to highlight C. avellana as a source of bioactive phytochemicals with the potential to exert beneficial effects on human health. Finally, analytical techniques for the quali-quantitative analysis of specialized metabolites occurring in the different parts of C. avellana have been reviewed.