Phenolic profiles and antioxidant activity of Turkish Tombul hazelnut samples (natural, roasted, and roasted hazelnut skin)

A Comprehensive Review of Bioactive Tannins in Foods and Beverages: Functional Properties, Health Benefits, and Sensory Qualities

Tannins, a diverse class of polyphenolic compounds, are widely present in a variety of plant-based foods and beverages, where they contribute significantly to flavor, astringency, and numerous health benefits. Known for their antioxidant, anti-inflammatory, and cardioprotective properties, tannins are associated with a reduced risk of chronic diseases such as cardiovascular disease, cancer, and diabetes. Their bioavailability and metabolism are influenced by factors such as polymerization, solubility, and interactions with the gut microbiota. Tannin-rich beverages, including tea, wine, fruit juices, and cider, offer a range of health-promoting effects, including antioxidant, cardioprotective, and antimicrobial activities. In addition, tannins contribute significantly to the sensory and nutritional characteristics of fruits, nuts, and vegetables, influencing flavor, color, and nutrient absorption. The levels and efficacy of tannins are subject to variation due to factors such as ripeness and food processing methods, which can increase their impact on food quality and health. This review provides a comprehensive examination of the bioactive roles of tannins, their nutritional implications, and their sensory effects, highlighting their importance in both dietary applications and overall well-being.

Hazelnut skin polyphenolic green extract as a promising natural antioxidant in pork burgers: Assessment of quality parameters and consumer acceptance

Given the increasing consumer focus on healthier and environmentally friendly foods, the use of natural antioxidants in food production is becoming more common. The recovery of these antioxidants from agri-food waste is crucial for a circular economy, as it revalues matrices that would otherwise become waste. This study aimed to assess the antioxidant capacity of hazelnut skin and its green polyphenolic extract and to evaluate their effect on some qualitative parameters of pork burgers. Three types of burgers were formulated: a control group, and two experimental groups with the addition of 2.5 % of hazelnut skin or 1 % of hazelnut green extract. On days 0 and 7 of refrigerated storage (0-2 °C) parameters such as color, cooking losses, tenderness, lipid oxidation, and volatile profile were evaluated. Additionally, a group of panelists was asked to assess the acceptability of color and the potential for purchase. In both raw and cooked burgers, at all times examined, the two experimental groups showed a significant improvement in oxidative stability and lower production of volatile fat oxidation compounds compared to the control in which the main indicators of pork meat spoilage were detected. Although, even if on the 7th day of storage, the HS and HSE burgers exhibited better color stability, these groups showed a worsening in terms of color acceptability and tenderness. Overall, despite trade-offs, the hazelnut skin and their green extract showed high potential to emerge as food additives in meat products.

In vitro fecal microbiota modulation properties of pectin and xyloglucan from hazelnut (Corylus avellana L.) skin, an industrial byproduct, and their incorporation into biscuit formula

The aim of this study was to extract water-soluble dietary fibers (WSDFskin), pectin (PECskin), and xyloglucan (XGskin) from hazelnut skin and to determine their impacts on colonic microbiota and metabolic function. WSDFskin, PECskin, and XGskin were extracted by water, acid, and alkali treatments, respectively. Monosaccharide analysis revealed WSDFskin and PECskin were dominated by uronic acids, while the XGskin was found to contain xyloglucan- and pectin-associated sugars. In vitro fecal fermentation analysis showed that WSDFskin, PECskin, and XGskin are fermented to different microbial short-chain fatty acid profiles by identical microbiota. 16S rRNA sequencing demonstrated that PECskin promoted Faecalibacterium prausnitzii and Lachnospiraceae related operational taxonomic units (OTUs), which are recognized as beneficial members of the human gut, whereas WSDFskin and XGskin stimulated Bacteroides OTUs. Interestingly, increased abundances of F. prausnitzii and Lachnospiraceae OTUs in PECskin were higher than those in commercially available pectin. Finally, PECskin and XGskin were tested in a biscuit model and the results showed that either PECskin or XGskin can be incorporated into biscuit formulations without impacting physical, textural, and sensory properties of the final product. Overall, our results demonstrated that hazelnut skin, an industrial byproduct, can be utilized for the production of functional dietary fibers, especially pectin, to improve colonic health.

Unrevealing the Halyomorpha halys Damage Fingerprint on Hazelnut Metabolome by Multiomic Platforms and AI-Aided Strategies

The brown marmorated stink bug (Halyomorpha halys) poses a significant threat to hazelnut crops by affecting kernel development and causing quality defects, reducing the market value. While previous studies have identified bitter-tasting compounds in affected kernels, the impact of stink bug feeding on the hazelnut metabolome, particularly concerning aroma precursors, remains underexplored. This study aims to map the nonvolatile metabolome and volatilome of hazelnut samples obtained by caging H. halys on different cultivars in two locations to identify markers for diagnosing stink bug damage. Using a multiomic approach involving headspace solid-phase microextraction (HS-SPME), comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOF MS), and liquid chromatography-high-resolution mass spectrometry (LC-HRMS), both raw and roasted hazelnuts are analyzed, with artificial intelligence (AI) and machine learning tools employed to explore data correlations. The study finds that the hazelnut metabolome and volatilome exhibit high chemical complexity with significant classes of compounds such as aldehydes, ketones, alcohols, and terpenes identified in both raw and roasted hazelnuts. Multivariate analysis indicates that the orchard location significantly impacts the metabolome, followed by damage type, with cultivar differences being less pronounced. Partial least-squares discriminant analysis (PLS-DA) models achieve high predictive accuracy for orchard location (99%) and damage type (≈80%), with the roasted volatilome showing the highest predictive accuracy. Correlation matrices reveal significant relationships between raw hazelnut metabolites and aroma compounds in roasted samples, suggesting potential markers for stink bug damage that could guide the quality assessment and mitigation strategies. Data fusion techniques further enhance classification performance, particularly in predicting damage type, underscoring the potential of integrating multiple data sets for comprehensive quality assessment.

Artificial intelligence decision making tools in food metabolomics: Data fusion unravels synergies within the hazelnut (Corylus avellana L.) metabolome and improves quality prediction

This study investigates the metabolome of high-quality hazelnuts (Corylus avellana L.) by applying untargeted and targeted metabolome profiling techniques to predict industrial quality. Utilizing comprehensive two-dimensional gas chromatography and liquid chromatography coupled with high-resolution mass spectrometry, the research characterizes the non-volatile (primary and specialized metabolites) and volatile metabolomes. Data fusion techniques, including low-level (LLDF) and mid-level (MLDF), are applied to enhance classification performance. Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) reveal that geographical origin and postharvest practices significantly impact the specialized metabolome, while storage conditions and duration influence the volatilome. The study demonstrates that MLDF approaches, particularly supervised MLDF, outperform single-fraction analyses in predictive accuracy. Key findings include the identification of metabolites patterns causally correlated to hazelnut's quality attributes, of them aldehydes, alcohols, terpenes, and phenolic compounds as most informative. The integration of multiple analytical platforms and data fusion methods shows promise in refining quality assessments and optimizing storage and processing conditions for the food industry.

By-product hazelnut seed skin characteristics and properties in terms of use in food processing and human nutrition

The hazelnut seed skins (HSS) are by-products from roasting or blanching hazelnuts without direct second utilization. The generation of HSS creates an economic and environmental problem. The object of the study was a comprehensive analysis of the properties for reuse of HSS. Water extraction of industrial HSS was applied (water with sonication of the HSS for 10 min at 90 ℃). The extracts obtained were freeze-dried to facilitate analysis and future application. The HSS and their extracts were analysed. Polyphenols, antioxidants, allergens, antimicrobial properties and instrumental sensory analysis were examined. The total polyphenol content in the samples was 37.8-44.0 mg gallic acid equivalent g-1. Gallic acid was the major phenolic compound. The antioxidant capacity of the samples was 198.9-250.6 mg VCEAC g-1 (vitamin C equivalent) according to the ABTS method and 98.4-106.8 mg VCEAC g-1 in the DPPH method. The extracts inhibited all tested strains of pathogenic bacteria. Allergen content was reduced in HSS and the extracts. Instrumental sensory analysis showed differences between taste parameters and odour profile samples. HSS can be reused in food production as a bacteriostatic, antioxidant additive and sensory-creating factor due to various chemical compounds corresponding with taste and odour.

Evaluation of the Antioxidant and Anti-Inflammatory Activities and Acute Toxicity of Caco Seed (Chrysobalanus icaco L.) in Murine Models

Chysobalanus icaco L. (C. icaco) is a plant that is native to tropical America and Africa. It is also found in the southeast region of Mexico, where it is used as food and to treat certain diseases. This study aimed to carry out a phytochemical analysis of an aqueous extract of C. icaco seed (AECS), including its total phenol content (TPC), total flavonoid content (TFC), and condensed tannins (CT). It also aimed to examine the antioxidant and metal-ion-reducing potential of the AECS in vitro, as well as its toxicity and anti-inflammatory effect in mice. Antioxidant and metal-ion-reducing potential was examined by inhibiting DPPH, ABTS, and FRAP. The acute toxicity test involved a single administration of different doses of the AECS (0.5, 1, and 2 g/kg body weight). Finally, a single administration at doses of 150, 300, and 600 mg/kg of the AECS was used in the carrageenan-induced model of subplantar acute edema. The results showed that the AECS contained 124.14 ± 0.32 mg GAE, 1.65 ± 0.02 mg EQ, and 0.910 ± 0.01 mg of catechin equivalents/g dried extract (mg EC/g de extract) for TPC, TFC and CT, respectively. In the antioxidant potential assays, the values of the median inhibition concentration (IC50) of the AECS were determined with DPPH (0.050 mg/mL), ABTS (0.074 mg/mL), and FRAP (0.49 mg/mL). Acute toxicity testing of the AECS revealed no lethality, with a median lethal dose (LD50) value of >2 g/kg by the intragastric route. Finally, for inhibition of acute edema, the AECS decreased inflammation by 55%, similar to indomethacin (59%, p > 0.05). These results demonstrated that C. icaco seed could be considered a source of bioactive molecules for therapeutic purposes due to its antioxidant potential and anti-inflammatory activity derived from TPC, with no lethal effect from a single intragastric administration in mice.

Groundnut and tree nuts: a comprehensive review on their lipid components, phytochemicals, and nutraceutical properties

The health benefits of nut consumption have been extensively demonstrated in observational studies and intervention trials. Besides the high nutritional value, countless evidences show that incorporating nuts into the diet may contribute to health promotion and prevention of certain diseases. Such benefits have been mostly and certainly attributed not only to their richness in healthy lipids (plentiful in unsaturated fatty acids), but also to the presence of a vast array of phytochemicals, such as polar lipids, squalene, phytosterols, tocochromanols, and polyphenolic compounds. Thus, many nut chemical compounds apply well to the designation "nutraceuticals," a broad umbrella term used to describe any food component that, in addition to the basic nutritional value, can contribute extra health benefits. This contribution analyses the general chemical profile of groundnut and common tree nuts (almond, walnut, cashew, hazelnut, pistachio, macadamia, pecan), focusing on lipid components and phytochemicals, with a view on their bioactive properties. Relevant scientific literature linking consumption of nuts, and/or some of their components, with ameliorative and/or preventive effects on selected diseases - such as cancer, cardiovascular, metabolic, and neurodegenerative pathologies - was also reviewed. In addition, the bioactive properties were analyzed in the light of known mechanistic frameworks.

Hazelnut and Walnut Nutshell Features as Emerging Added-Value Byproducts of the Nut Industry: A Review

The hard-shelled seed industry plays an important role in the global agricultural economy. In fact, only considering hazelnut and walnut, the global nut supply is over 5.6 tons. As a result considerable amounts are produced year by year, burnt or discarded as waste, bypassing a potential source of valuable compounds or features. This review deals with the recent scientific literature on their chemical composition as well as functional applications as an approach to sustain the utilization of the main byproduct derived from industry. Indeed, nutshells have received great interest due to their lignin, antioxidant, physical and mechanical features. It was found that these properties vary among cultivars and localities of plantation, influencing physical and structural features. The inconsistencies regarding the above-mentioned properties of nutshells lead to exploring the status of hazelnut and walnut shell applications in sustainable bio-economy chains. In fact, in terms of potential applications, the state of the art links their use to the construction industry and the manufacture of materials, such as resin or plastic composites, particleboards or construction panels, or vital infrastructure and as a filler in cement pavements. However, their current use continues bypassing their great antioxidant potential and their interesting chemical and mechanical features.

Leveraging new opportunities and advances in high-pressure homogenization to design non-dairy foods

High-pressure homogenization (HPH) and ultrahigh-pressure homogenization (UHPH) are emerging food processing techniques for stabilizing emulsions and food components under the pressure range from 60 to 400 MPa. Apart from this, they also support increasing nutritional profile, food preservation, and functionality enhancement. Even though the food undergoes the shortest processing operation, the treatment leads to modification of physical, chemical, and techno-functional properties, in addition to the formation of micro-sized particles. This study focuses on recent advances in using HPH/UHPH on plant-based milk sources such as soybeans, almonds, hazelnuts, and peanuts. Overall, this systematic review provides an in-depth analysis of the principles of HPH/UHPH, the mechanism of action, and their applications in other nondairy areas such as fruits and vegetables, meat, fish, and marine species. This work also deciphers the role of HPH/UHPH in modifying food components, their functional quality enhancement, and their provision of oxidative resistance to many foods. HPH is not only perceived as a technique for size reduction and homogenization; however, it does various functions like microbial inactivation, improvement of rheologies like texture and consistency, decreasing of lipid oxidation, and making positive modifications to proteins such as changes to the secondary structure and tertiary structure thereby enhancing the emulsifying properties, hydrophobicity of proteins, and other associated functional properties in many nondairy sources at pressures of 100-300 MPa. Thus, HPH is an emerging technique with a high throughput and commercialization value in food industries.

A Review of Plant-Based Drinks Addressing Nutrients, Flavor, and Processing Technologies

Plant-based drinks have garnered significant attention as viable substitutes for traditional dairy milk, providing options for individuals who are lactose intolerant or allergic to dairy proteins, and those who adhere to vegan or vegetarian diets. In recent years, demand for plant-based drinks has expanded rapidly. Each variety has unique characteristics in terms of flavor, texture, and nutritional composition, offering consumers a diverse range of choices tailored to meet individual preferences and dietary needs. In this review, we aimed to provide a comprehensive overview of the various types of plant-based drinks and explore potential considerations including their nutritional compositions, health benefits, and processing technologies, as well as the challenges facing the plant-based drink processing industry. We delve into scientific evidence supporting the consumption of plant-based drinks, discuss their potential roles in meeting dietary requirements, and address current limitations and concerns regarding their use. We hope to illuminate the growing significance of plant-based drinks as sustainable and nutritious alternatives to dairy milk, and assist individuals in making informed choices regarding their dietary habits, expanding potential applications for plant-based drinks, and providing necessary theoretical and technical support for the development of a plant-based drink processing industry.

Hazelnut and its by-products: A comprehensive review of nutrition, phytochemical profile, extraction, bioactivities and applications

As output of hazelnut increases worldwide, so does the amount of by-products, leading to huge waste and environmental stress. This paper focuses on the varieties of hazelnut that have been studied more in the past two decades, and summarizes the research status of hazelnut and its by-products from the aspects of nutritional value, phytochemicals, extraction methods, biological functions and applications. Hazelnut and its by-products are rich in a variety of bioactive constituents, mainly polyphenols, which have antioxidant, antibacterial and prebiotic effects. Moreover, hazelnut shells, husks, and leaves contain taxanes such as paclitaxel, which can inhibit the proliferation of cancer cells. They are potentially good natural sources of paclitaxel compared to the slower growing yew. Therefore, it is essential to further integrate the extraction techniques and health-promoting properties of these nutrients and bioactive substances to expand their application and enhance their value.

The Effect of Altitude on Phenolic, Antioxidant and Fatty Acid Compositions of Some Turkish Hazelnut (Coryllus avellana L.) Cultivars

Turkey is the leading producer and exporter of hazelnuts, producing approximately 64% of global hazelnut production. This research investigated the effects of cultivars and altitude on the phenolic, antioxidant, and fatty acid compositions of five hazelnut cultivars grown at three different altitudes, 100 m, 350 m, and 800 m, in Ordu province, one of the territories that produce the most hazelnuts. The results showed that the cultivar and location significantly affected phenolic compounds, antioxidant activity, and fatty acid (FA) content. The lowest (2.30 mg/kg-Yağlı) and highest (21.11 mg/kg-Kara) gallic acids were obtained at 100 m. The highest total phenolic content and antioxidant activity were found in the nuts grown at 350 m in the Kara and Palaz cultivars, at 100 m in the Yağlı and Sivri cultivars, and at 800 m in the Çakıldak cultivar. Oleic acid was the predominant FA in the cultivars and possessed a diverse trend according to the altitude and cultivar, ranging from 76.04% to 84.80%, increasing with altitude in all cultivars except Çakıldak. Palmitic acid was the predominant saturated FA followed by stearic acid, which significantly varied according to the elevations. This study suggests that the responses of hazelnuts to altitude depend on the cultivar; hence, a proper approach to producing nuts containing more phenolic, fatty acids, and antioxidant activity includes choosing a suitable cultivar for a specific elevation.

Phytoextracts for Human Health from Raw and Roasted Hazelnuts and from Hazelnut Skin and Oil: A Narrative Review

The objectives of this narrative review are as follows: an evaluation of the bromatological composition of hazelnuts and a comparison of the nutritional properties of raw versus roasted hazelnuts, taking into account potential differences among varieties from different production territories such as Turkey, Italy, Chile, and New Zealand; an evaluation of nutrients contained in hazelnut skin; and an evaluation of nutrients contained in hazelnut oil. This review incorporates 27 scientific articles that measured and reported the concentrations of macro- and micro-nutrients in hazelnuts. These hazelnuts were subjected to different processing methods, originated from various geographical areas, or belonged to different varieties. Our results showed that the different varieties and territories where the hazelnuts were cultivated influence their bromatological composition, and we found that different processing steps can largely influence the concentration of specific nutrients. The removal of the skin, which contains a very high concentration of compounds with antioxidant action, is particularly critical. We should give greater attention to the skin, considering it not as a waste product, but as an important part of the hazelnut due to its nutritional properties of primary relevance in the Mediterranean diet. We provide a detailed assessment of the nutritional properties of the hazelnut kernel, skin, and oil, evaluating nutrient compositions and possible modifications (increases or reductions) that occur during the roasting process or that depend on the production territory and origin.

Sex-dependent colonic microbiota modulation by hazelnut (Corylus avellana L.) dietary fiber

Although many efforts have been made to characterize the functional properties of hazelnut constituents (mainly its oil, protein, and phenolics), those of its dietary fiber (DF) have not been elucidated yet. Here, we aimed to investigate the impact of DF of natural and roasted hazelnuts, and hazelnut skin on the colonic microbiota in vivo (C57BL/6J mouse models) by determining their composition through 16S rRNA sequencing and microbial short-chain fatty acids (SCFAs) using gas chromatography. Our results revealed that hazelnut DF generally showed an acetogenic effect in male mice, whereas the same trend was not observed in the female counterparts. The 16S rRNA sequencing results showed that hazelnut DF, especially that of natural hazelnuts, increased the relative abundances of Lactobacillus-related OTUs that have probiotic potential. LEfSe analysis indicated that, for female mice, Lachnospiraceae, Prevotella, Ruminococcaceae, and Lactobacillus were found to be discriminators for DF of natural hazelnuts, roasted hazelnuts, hazelnut skin, and control, respectively, whereas Bacteroides, Lactobacillus, Prevotella, and Lactococcus were the discriminators for the male counterparts, respectively. This study clearly indicates that, although the roasting process slightly alters the functionalities, hazelnut DF favors beneficial microbes and stimulates beneficial microbial metabolites in the colon in a sex-dependent way, which could be a contributing factor to the health-promoting effects of hazelnuts. Furthermore, hazelnut skin, a byproduct of the hazelnut industry, was found to have potential to be utilized to produce functional DF targeting colonic health.

UPLC-MS/MS profiling, antioxidant and anti-inflammatory activities, and potential health benefits prediction of phenolic compounds in hazel leaf

Hazel leaf, one of the by-products of hazelnut, which is widely used in traditional folk medicine around the world. In the present study, the profile of free, conjugated, and bound phenolic compounds from hazel leaf was detected and their antioxidant and anti-inflammatory activities were investigated. The potential health benefits of different phenolic compounds were also predicted. The results showed that the 35 phenolic substances of free, conjugated and bound forms were identified including phenolic acids, flavonoids and catechins. Most of the hazel leaf phenolics were presented in free form, followed by conjugated and bound form. All the fractions effectively inhibited the production of reactive oxygen species and malondialdehyde in TBHP-stimulated human umbilical vein endothelial cells by enhancing endogenous superoxide dismutase, and accordingly alleviated inflammatory cytokines (NO, IL-1β, TNF-α, and IL-6) in LPS-stimulated RAW264.7 cells, showing obvious antioxidant and anti-inflammatory capacity. Moreover, combined with network pharmacology, the potential therapeutic effects and functional pathways of hazel leaf phenolics were predicted, which provided value basis for exploring their treatment on diseases and developing health products in the future.

Nuts as functional foods: Variation of nutritional and phytochemical profiles and their in vitro bioactive properties

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Nutritional, biological and in vitro anti-diabetic, -obesity, -cholinergic of nuts.

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Polymeric procyanidins dominant polyphenols.

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Oleanic and pomolic acids dominant triterpenes.

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Nuts are low in Cu, Zn, Mn, Na, but rich in K and Mg.

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All nuts showed high activity in inhibiting intestinal α-glucosidase.

The aim of the present study was to examine the nutritional (fat, fatty acids, minerals, sugars) and bioactive compounds (polyphenols, tocochromanols, triterpene) and their influence on in vitro anti-diabetic (pancreatic α-amylase and intestinal α-glucosidase), anti-obesity (pancreatic lipase) and anti-cholinergic (AChE and BuChE) inhibitory activity of 8 different popular nuts—pecan, pine, hazelnuts, pistachio, almonds, cashew, walnuts, and macadamia.

The total content of phenolic compounds in nuts ranged from 432.9 (walnuts) to 5.9 (pistachio) mg/100 g. The dominant polyphenols are polymeric procyanidins (walnuts – 415.1 mg/100 g). Nuts are rich in tocochromanols (832.9–4377.5 μg/100 g), especially α- and γ-tocopherols. The highest content of α-tocopherol (vitamin E) was detected in hazelnuts and almonds (2551.0 and 2489.7 μg/100 g, respectively) while the lowest amounts were detected in macadamia, cashew and walnuts. The most abundant in nuts are oleanic and pomolic acids (35 and 22 % of total, respectively), while betulin, uvaol and erythrodiol are less characteristic triterpenes for nuts (<1%). Pine nuts are the nuts with the highest content of triterpene (690.3 mg/100 g). Pistachio and almonds are the richest in total fat (>45 %), but monounsaturated (17.5–79.3 %; hazelnuts, almonds, cashew, macadamia, pistachio and pecan) and polyunsaturated (7.5–69.3 %; pine, walnuts) are the dominant fatty acids. Moreover, nuts are low in Cu, Zn, Mn and Na content, but rich in K (464.5–1772.3 mg/100 g) and Mg (197.0–502.5 mg/100 g). Macadamia, walnuts and cashew are good sources of Se. Pistachio, almonds and cashew were characterized by the highest content of sugars, but the dominant sugar was saccharose (58.2–2399.3 mg/100 g). All nuts showed high activity in inhibiting intestinal α-glucosidase (>90 %), but lower ability to inhibit pancreatic α-amylase and pancreatic lipase activity. The activity in inhibiting acetyl- and butylcholinesterase was up to 30 %.

As described above, all nuts contain various compounds that improve the nutritional value. Therefore they should be one of the important components of the daily human diet rich in functional foods.

Recovery and Concentration of Polyphenols from Roasted Hazelnut Skin Extract Using Macroporous Resins

Hazelnut skin is a rich source of polyphenols but is generally discarded during the roasting process of hazelnuts. Previous studies reported the extraction and identification of these compounds using different solvents and procedures; however, there are few reports on their enrichment and purification. In this study, three types of Amberlite macroporous resins (XAD 16, XAD 4, and XAD 7) were compared to evaluate the enrichment of polyphenols via adsorption and desorption mechanisms. The operating condition parameters for polyphenol adsorption/desorption of each resin were determined, the kinetics of adsorption were examined, and a method for polyphenol recovery was developed using static and dynamic adsorption/desorption. Antioxidant activity and high-performance liquid chromatography-diode array detection were used to confirm the increase in polyphenols obtained using the adsorption/desorption technique. XAD16 showed the highest adsorption capacity, with a recovery of 87.7%, and the adsorption kinetics fit well with a pseudo-second-order model. The highest poly-phenol desorption ratio was observed using an ethanol/water solution (70% v/v) at a flow rate of 1.5 bed volume/h.

Effects of Hazelnut Consumption on Cardiometabolic Risk Factors and Acceptance: A Systematic Review

Despite being rich sources of monounsaturated fat and a number of vitamins, minerals, and phytonutrients, hazelnuts have received less attention than some other nut types. A qualitative systematic review was carried out to determine the effects of hazelnut consumption on acceptance and markers of cardiometabolic health, including blood lipids and lipoproteins, apolipoproteins A1 and B100, body weight and composition, blood pressure, glycemia, antioxidant status, oxidative stress, inflammation, and endothelial function. In total, 22 intervention studies (25 publications) met our inclusion criteria. The findings indicate some improvements in cardiometabolic risk factors; however, limitations in study design mean interpretation is problematic. The inclusion of hazelnuts in the diet did not adversely affect body weight and composition. Acceptance of hazelnuts remained stable over time confirming nut consumption guidelines are feasible and sustainable. Future studies using more robust study designs in a variety of populations are required to draw more definitive conclusions on the health benefits of hazelnut consumption.

The Influence of Hazelnut Skin Addition on Quality Properties and Antioxidant Activity of Functional Yogurt

There is an increasing interest in applying fruit-processing wastes as functional food ingredients. Hazelnut skin, an interesting and innovative ingredient has recently been evaluated as one of the richest edible sources of polyphenolic compounds. This study aimed to evaluate the use of hazelnut skin as a functional additive in yogurt and to determine the effect of various percentages (2%, 3%, and 4%) of hazelnut skin on the physicochemical, microbiological, rheological, biochemical, and sensorial properties of yogurt. The results showed that the addition of hazelnut skin significantly increased total solids from 16.5% to 17.7% and fat content from 3.45% to 4.60% and decreased titratable acidity by up to 36%. The enrichment with hazelnut skin also improved the viability of yogurt bacteria, water holding capacity (WHC), and antioxidant activity of yogurts. Better results for WHC and antioxidant values were found in yogurt enriched with 4% hazelnut skin. Total phenolic content and Fe²⁺ chelating activity of yogurts increased with the increasing hazelnut skin ratio. However, yogurts with hazelnut skin had low instrumental texture parameters and apparent viscosity values. On the other hand, acceptable sensorial properties similar to control yogurts increase the consumption potential of yogurts enriched with hazelnut skin.

Effects of hazelnut supplemented diet on doxorubicin-induced damage of reproductive system in male rats

The present study was objected to investigate the effect of hazelnut supplemented diet on the levels of oxidative stress and fertility parameters against doxorubicin-induced testicular and epididymal tissue damage of male rats. Rats were randomly divided into four groups (each n = 8), namely control group (CG), doxorubicin group (DG), doxorubicin + hazelnut group (DHG), and doxorubicin + vitamin E group (DEG). This is the first study designed using DHG. Doxorubicin was intraperitoneally injected into all diet groups except CG at a dose of 3 mg/kg body weight on days 1, 7, 14, 21, and 28. In addition, DHG was supplemented with a hazelnut diet at a dose of 3 g/kg body weight/day and vitamin E was added to the drinking water of DEG at a dose of 50 mg/kg body weight/day. DHG reversed the side effects of doxorubicin and positively improved the epididymis sperm quality, testicular and epididymal tissue injury, testosterone level, epididymis oxidative stress index, and lipid peroxidation in male rats. These findings suggest that hazelnut has positive effects against doxorubicin dependent damage on male rats and it may be a promising supplement for amelioration of testicular toxicity. PRACTICAL APPLICATIONS: Hazelnut has numerous positive health effects due to its macronutrients, micronutrients, lipid-soluble compounds and bioactive phenolics. Studies have shown that regular consumption of hazelnut may have a positive effect on lipid parameters, oxidative stress, inflammation markers, and endothelial dysfunction in both healthy people and patients with chronic diseases. Although doxorubicin (Adriamycin, DOX) is an antibiotic that has been widely used in cancer treatment for nearly 30 years, it causes organ toxicity including testicular tissue. Hazelnut may have positive effects on the damage caused by DOX in the reproductive system. However, studies on the effect of hazelnut on male reproductive health are scarce. Therefore, this study provided a basis for the clinical evaluation of the effects of hazelnut on the reproductive system.

Kernel Nutrient Composition and Antioxidant Ability of Corylus spp. in China

Hazelnut (Corylus) is an important woody oil tree species in economic forests. China, as one of the original countries of native Corylus species, had 8 species and 2 varieties. However, little information is available on the hazelnut nutritional quality of these Chinese Corylus species. In this study, four main wild Corylus species (C. heterophylla Fisch., C. mandshurica Maxim., C. kweichowensis Hu., and C. yunnanensis Franch.) originating in China and one main cultivar of hybrid hazelnut (Corylus heterophylla Fisch. × C. avellana L.) cv. 'Dawei' from China were used to analyze the basic nutritional composition (content of oil, fatty acid, protein, saccharide, aminao acid, vitamin C, tocopherol, total phenols, and total flavonoids) and antioxidant ability. The results showed that oil content ranged from 52.97 to 60.88 g/100 g DW and highly unsaturated fatty acid (UFA) content was over 91%. Oleic was the most dominant UFA in these hazelnut kernels, and the relative content was ranging from 71.32 to 85.19%. Compared with other four hazelnut kernels, C. heterophylla Fisch. was the lowest oil content of hazelnut with lower oleic acid content and higher linoleic acid content, obviously. The total protein content ranged from 13.15 to 18.35 g/100 g DW, and all amino acids were detected as hydrate amino acids, but Tryptophan, an essential amino acid, was not detected as free amino acid in these hazelnut kernels. Kernel of C. heterophylla Fisch. was with the highest content of protein and amino acid. Saccharose was the most essential and abundant disaccharide in the hazelnut kernels. C. mandshurica Maxim. was the highest saccharide content among these hazelnut kernels. α-tocopherol was the main type of tocopherol found in the hazelnut kernels. Wild hazelnut kernels generally had higher bioactivity substance content (vitamin C, total tocopherol, total phenol and total flavonoid) and antioxidant capacity. Compared to the four wild hazelnut kernels, the hybrid hazelnut cv. 'Dawei' had higher content of oil, oleic acid, α-tocopherol and sugar. Overall, there were great differences in the nutritional composition of different hazelnut species. Wild species are a good source of breeding materials because of their own characteristics in nutrition composition, and the hybrid hazelnut cv. 'Dawei' with good quality has the value of commercial promotion.

Variation of Morphological, Agronomic and Chemical Composition Traits of Local Hazelnuts Collected in Northern Spain

Hazelnut is a traditional crop in northern Spain, where it grows wild as well as being cultivated. A field collection of 41 local and 17 non-local accessions, including 15 well-known cultivars, was established at SERIDA in Villaviciosa, Spain. Here, phenotypic variation was documented for phenological and morphological traits and chemical composition. A large degree of variation for most morphological and phenological traits, except nut maturity date, was revealed. Estimates of broad-sense heritability were high (>0.75) for most of the assessed characters, except for the first male bloom date (0.65), male and female flowering periods (0.40, 0.31), kernel weight (0.69), and kernel percentage (0.33). Local accessions produced smaller nuts and kernels than well-known cultivars but with higher kernel percentage. Limited overlapping between the male and female flowering periods (dychogamy) was observed, except for 'Forcinas 1', 'Forcinas 2', and 'Morell'. The local accessions generally exhibited significantly later male and female flowering compared with the reference cultivars. The local materials showed similar nutritional values to those reported previously for hazelnut. Moreover, the local accessions presented average values similar to the non-local accessions for total fat, ash and carbohydrate contents, as well as energy value, but their protein contents were lower. Their oils were rich in functional compounds, such as unsaturated fatty acids (average: 90.1%), tocopherols (514 mg/kg) and squalene (294.3 mg/kg). A hierarchical clustering on principal components analysis grouped the accessions and differentiated eight local accessions from the rest, including the landrace 'Casina'. This finding provides potential new cultivars, as well as sources of desirable traits, for European hazelnut breeding programs.

Detection and Comparison of Bioactive Compounds in Different Extracts of Two Hazelnut Skin Varieties, Tonda Gentile Romana and Tonda Di Giffoni, Using a Metabolomics Approach

Agro-wastes are one of the major sources for nutritional and therapeutic benefits along with other beneficial properties. Dark brown pellicular pericarp (skin or testa), covering the hazelnut seed, is removed before consumption after the roasting of a kernel. Defatted skins of both hazelnut varieties, Tonda Gentile Romana and Tonda di Giffoni, were profiled by a metabolomics-based approach and this was used to discriminate between these two different hazelnut cultivars. In particular, an untargeted metabolomic extract from hazelnut by-products was investigated by UHPLC-Mass spectrometry followed by multivariate statistics analysis, and significant qualitative and quantitative metabolic differences were observed between them. Samples were also assessed for their total phenolic and antioxidant capacity using two different assays. Although no significant differences were found in total phenolic contents and antioxidant capacity, the Flavone, Flavonol, Flavonoid, and Phenylpropanoid Biosynthesis pathway was significantly higher in the Romana rather than in the Giffoni variety, whereas Myricetin and Syringetin compounds were more representative in Giffoni cultivars. These results indicated that hazelnut skin, especially from the Romana variety, could potentially be used as an ingredient in healthy food. Healthy food is a new food category with an expanding demand from future generations.

Choline Chloride-Lactic Acid-Based NADES As an Extraction Medium in a Response Surface Methodology-Optimized Method for the Extraction of Phenolic Compounds from Hazelnut Skin

Deep eutectic solvents (DESs) are promising green solvents for the extraction of compounds from food byproducts. Hazelnut (Corylus avellana L.) is one of the most commonly cultivated tree nuts worldwide. The skin represents one of the major byproducts of the hazelnut industry and accounts for 2.5% of the total hazelnut kernel weight. It is a rich source of phenolic compounds like flavan-3-ols, flavonols, dihydrochalcones, and phenolic acids. In this work, fifteen DESs based on choline chloride and betaine, with different compositions, were studied in order to test their phenolic compounds extraction efficiency through the determination of their total concentration via Folin–Ciocalteu assay. A qualitative analysis of extracted phenolic compounds was assessed by HPLC with UV and MS detection. Using the DES with the best extraction efficiency, a new ultrasound-assisted solid liquid extraction (UA-SLE) method was optimized though the response surface methodology (RSM), taking into account some extraction parameters. Efficient recovery of extracted phenolic compounds was achieved using a 35% water solution of choline chloride and lactic acid (molar ratio 1:2) as an extraction solvent, working at 80 °C and with a solid-to-solvent ratio of 1:25 gmL⁻¹. The optimized conditions made it possible to recover 39% more phenolic compounds compared to a classic organic solvent.

Diversity of Chemical Structures and Biosynthesis of Polyphenols in Nut-Bearing Species

Nuts, such as peanut, almond, and chestnut, are valuable food crops for humans being important sources of fatty acids, vitamins, minerals, and polyphenols. Polyphenols, such as flavonoids, stilbenoids, and hydroxycinnamates, represent a group of plant-specialized (secondary) metabolites which are characterized as health-beneficial antioxidants within the human diet as well as physiological stress protectants within the plant. In food chemistry research, a multitude of polyphenols contained in culinary nuts have been studied leading to the identification of their chemical properties and bioactivities. Although functional elucidation of the biosynthetic genes of polyphenols in nut species is crucially important for crop improvement in the creation of higher-quality nuts and stress-tolerant cultivars, the chemical diversity of nut polyphenols and the key biosynthetic genes responsible for their production are still largely uncharacterized. However, current technical advances in whole-genome sequencing have facilitated that nut plant species became model plants for omics-based approaches. Here, we review the chemical diversity of seed polyphenols in majorly consumed nut species coupled to insights into their biological activities. Furthermore, we present an example of the annotation of key genes involved in polyphenolic biosynthesis in peanut using comparative genomics as a case study outlining how we are approaching omics-based approaches of the nut plant species.

Effect of Food Processing on Antioxidant Potential, Availability, and Bioavailability

Antioxidants are understood to play a key role in disease prevention; because of this, research and interest in these compounds are ever increasing. Antioxidative phytochemicals from natural sources are preferred, as some negative implications have been associated with synthetic antioxidants. Beans, nuts, seeds, fruits, and vegetables, to name a few, are important sources of phytochemicals, which have purported health benefits. The aforementioned plant sources are reportedly rich in bioactive compounds, most of which undergo some form of processing (boiling, steaming, soaking) prior to consumption. This article briefly reviews selected plants (beans, nuts, seeds, fruits, and vegetables) and the effects of processing on the antioxidant potential, availability, and bioavailability of phytochemicals, with research from our laboratory and other studies determining the health benefits of and processing effects on bioactive compounds.

Antioxidant and Antiglycation Effects of Polyphenol Compounds Extracted from Hazelnut Skin on Advanced Glycation End-Products (AGEs) Formation

The advanced glycation end-products (AGEs) arise from non-enzymatic reactions of sugar with protein side chains, some of which are oxido-reductive in nature. Enhanced production of AGEs plays an important role in the pathogenesis of diabetic complications as well as in natural aging, renal failure, oxidative stress, and chronic inflammation. The aim of this work is to study antiglycation effects of polyphenol compounds extracted by hazelnut skin that represents an example of polyphenols-rich food industry by-product, on AGEs formation. AGEs derived from incubation of bovine serum albumin (BSA) and methylglyoxal (MGO) were characterized by fluorescence. The phenolics identification and total polyphenol content in hazelnut skin extracts were analyzed by HPLC-MS and the Folin–Ciocalteu method, respectively. Antioxidant efficacy was evaluated by monitoring total antioxidant activity to assess the ABTS radical scavenging activity of samples by TEAC assay and oxygen radical absorbance capacity (ORAC) assay, expressed as millimoles of Trolox equivalents per gram of sample. Data here presented suggest that phenolic compounds in hazelnut skin have an inhibitory effect on the BSA-AGEs model in vitro, and this effect is concentration-dependent. The putative role of the hazelnut skin antioxidative properties for hindering AGEs formation is also discussed. Because of AGEs contribution to the pathogenesis of several chronic diseases, foods enriched, or supplements containing natural bioactive molecules able to inhibit their production could be an interesting new strategy for supporting therapeutic approaches with a positive effect on human health.

Bioactive phenolic components and potential health effects of chestnut shell: A review

Chestnut kernels are often used for direct consumption; or processed to produce marron glacé, chestnut purée, and gluten-free products, while chestnut by-products (inner shell and outer shell) are treated as waste residues. Many in vivo and in vitro studies have proved how chestnut shell extract functions as an antioxidant and exhibits anticancer, anti-inflammatory, antidiabetic, and anti-obesity activities. This review introduces the main components of phenolic compounds in chestnut shells, traditional and modern extraction methods, and reported potential health effects. The aim is to have a better understanding of the functional active ingredients in chestnut shells and their value-added uses, to increase understanding of future applications of this agricultural and sideline product in the food, pharmaceutical, and cosmetic industries. PRACTICAL APPLICATIONS: In recent years, chestnut shells have become a hot research topic because of their rich bioactive ingredients. Due to the large amount of phenolic compounds in chestnut shells and their potential health functions (antioxidant, anticancer, antibacterial, anti-inflammatory, hypoglycemic, and treatment of obesity), extracts of chestnut shells have high biological value in the treatment of diseases. Therefore, this review introduces the main components of phenolic compounds in chestnut shells, traditional and modern extraction methods, and the potential health effects of these compounds. The aim of this review is to better understand the functional, active ingredients in chestnut shells and their value-added uses, and to increase understanding of future applications of this agricultural and sideline product in the food, pharmaceutical, and cosmetic industries.

Comparative transcriptome and flavonoids components analysis reveal the structural genes responsible for the yellow seed coat color of Brassica rapa L

Background

Seed coat color is an important horticultural trait in Brassica crops, which is divided into two categories: brown/black and yellow. Seeds with yellow seed coat color have higher oil quality, higher protein content and lower fiber content. Yellow seed coat color is therefore considered a desirable trait in hybrid breeding of Brassica rapa, Brassica juncea and Brassica napus.

Methods

Comprehensive analysis of the abundance transcripts for seed coat color at three development stages by RNA-sequencing (RNA-seq) and corresponding flavonoids compounds by liquid chromatography-tandem mass spectrometry (LC-MS/MS) were carried out in B. rapa.

Results

We identified 41,286 unigenes with 4,989 differentially expressed genes between brown seeds (B147) and yellow seeds (B80) at the same development stage. Kyoto Encyclopedia of Genes and Genomes enrichment analysis identified 19 unigenes associated with the phenylpropanoid, flavonoid, flavone and flavonol biosynthetic pathways as involved in seed coat color formation. Interestingly, expression levels of early biosynthetic genes (BrCHS, BrCHI, BrF3H, BrF3’H and BrFLS) in the flavonoid biosynthetic pathway were down-regulated while late biosynthetic genes (BrDFR, BrLDOX and BrBAN) were hardly or not expressed in seeds of B80. At the same time, BrTT8 and BrMYB5 were down-regulated in B80. Results of LC-MS also showed that epicatechin was not detected in seeds of B80. We validated the accuracy of our RNA-seq data by RT-qPCR of nine critical genes. Epicatechin was not detected in seeds of B80 by LC-MS/MS.

Conclusions

The expression levels of flavonoid biosynthetic pathway genes and the relative content of flavonoid biosynthetic pathway metabolites clearly explained yellow seed color formation in B. rapa. This study provides a foundation for further research on the molecular mechanism of seed coat color formation.

Phenolic profiles and antioxidant activities of free, esterified and bound phenolic compounds in walnut kernel

The free, esterified and bound forms of 37 phenolic compounds (including hydroxybenzoic acid, hydroxycinnamic acids, flavanols, flavonols and flavones) from walnut kernel (Juglans regia L.) were investigated in this study. Results showed that the majority of walnut phenolics were presented in the free form (51.1%-68.1%), followed by bound (21.0%-38.0%) and esterified forms (9.7%-18.7%). Ellagic acid, gallic acid, ferulic acid, sinapic acid and caffeic acid were widely distributed in three forms. Differently, jeuglone, kaempferol, quercetin-7-o-β-d-glucoside and dihydroquercetin were only found in free phenolics. Among the three forms, free phenolics had the highest radical scavenging activity (IC₅₀: DPPH, 15.5 µg/ml; ABTS, 13.6 µg/ml). The correlation coefficients between the antioxidant activities of phenolics and their corresponding contents were 0.82-0.92. More soluble phenolics (free and esterified forms) could be extracted by acetone, while methanol was better at extracting insoluble bound phenolics.

Fatty acid profile, mineral content and bioactive compounds of cocoa spreads supplemented with baru almonds (

The present study aimed to perform a chromatographic and spectrophotometric characterization of the bioactive compounds, antioxidants, phenolics, profile of fatty acids and minerals in spreads supplemented with different contents of baru almonds. The addition of baru almonds (P1 treatment) enhanced the concentrations of vitamin C, antioxidants, gallic acid, calcium, magnesium, sulfur, manganese and oleic acid. In contrast, the absence of this oil in P3 treatment resulted in an increase in the concentrations of vanillin, p-coumaric acid, ferric acid, o-coumaric acid, linoleic acid and saturated and polyunsaturated fatty acids. When the tannin, beta-carotene/linoleic acid, trans-cinnamic acid, monounsaturated fatty acids, hypocholesterolemic and hypercholesterolemic fatty acid contents and atherogenic and thrombogenic indices were evaluated, no significant (p > 0.05) differences were detected between treatments.

The Antioxidant Content of Coffee and Its In Vitro Activity as an Effect of Its Production Method and Roasting and Brewing Time

Coffee is one of the most popular beverages in the world. The high production and health properties of coffee make it one of the best among daily drinks. Coffee is wrongly identified as only a stimulant because of its caffeine content. On the other hand, coffee is one of the best sources of other bioactive compounds, such as flavonoids and phenolic acids. Organic coffee is produced without artificial fertilizers and pesticides. Not only the high quality of beans but also roasting and brewing times guarantee the best taste and quality of coffee beverages. The aim of the present experiment was to determine the best level of roasting and brewing time for organic and conventional coffee. The experiment was carried out with Peru coffee beans from organic and conventional farms. The contents of caffeine and bioactive compounds were measured in different roasted and brewed coffee drinks. The obtained results showed that the conventional coffee contained significantly more caffeine, total flavonoids, and quercetin derivatives than the organic coffee. On the other hand, the organic coffee was characterized by a higher level of almost all bioactive compounds. The best level of roasting was determined to be medium, and the optimal brewing time was 3 minutes.

Chemical Composition, Total Phenols and Flavonoids Contents and Antioxidant Activity as Nutritive Potential of Roasted Hazelnut Skins (Corylus avellana L.)

The present study evaluates natural composition of Serbian roasted hazelnut skins (HS) with potential role in application as functional nutrient of various food products. Total phenols (TPC) and flavonoids contents (TFC) in HS extracts obtained with different ethanol concentrations (10%—I, 50%—II and 96%—III) and their antioxidant activities were investigated. The highest total phenols content (706.0 ± 9.7 mgGAE/g_extract) was observed in 96% ethanol HS extract. Ethanol HS extracts showed very high antioxidant activity with effective concentrations (EC₅₀) ranged between 0.052 and 0.066 mg/mL. The phenol and flavonoid content of roasted HS extracts I–III was determined by HPLC-ESI-MS/MS analyses. Contents of lipids, proteins, carbohydrates, metals, and C, H, N, S elements in roasted HS were also determined. Relatively high C/N, C/P and C/N/P ratios, rich metal contents and fatty acids composition indicated that hazelnut skin might be a good candidate for use as either human or fungal functional nutrient. In addition, possible application of phenolic HS extracts as UV booster was studied by recording UV spectra (220–440 nm) of 10 mg/L of HS extracts I–III combined with 10 mg/L of chemical sunscreen agent benzophenone-3 and in vitro sun protection factor (SPF) was calculated.

Green-Sustainable Recovery of Phenolic and Antioxidant Compounds from Industrial Chestnut Shells Using Ultrasound-Assisted Extraction: Optimization and Evaluation of Biological Activities In Vitro

Chestnut processing industry generates large amounts of by-products, including leaves, burs and shells that are a source of bioactive compounds. The purpose of this study was to establish an ultrasound-assisted extraction (UAE) of phenolic and antioxidant compounds from industrial chestnut shells. A central composite design (CCD) was conducted to analyze the effects of time (4–46 min) and temperature (34–76 °C) in the antioxidant activity (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP)) and total phenolic compounds (TPC) of chestnut shells extracts. The optimal extraction conditions were obtained at 70 °C for 40 min. The optimal extract was characterized regarding phenolic profile, radical scavenging capacity, and effects on intestinal and dermal cell lines. The optimal extract revealed high amounts of ellagic acid (40.4 µg/mg dw), followed by caffeic acid derivative (15.4 µg/mg dw) and epigallocatechin (15.3 µg/mg dw). Indeed, the extract exhibited the highest scavenging efficiencies against NO● (IC₅₀ = 0.1 µg/mL) and HOCl (IC₅₀ = 0.7 µg/mL) and did not conducted to a decrease on HaCaT and HFF-1 viability up to 100 μg/mL. Oppositely, a decrease on Caco-2 and HT29-MTX viability was observed. This study suggests that UAE could be a sustainable option to valorize chestnut shells as raw material for different industries.

Dietary fibre profiles of Turkish Tombul hazelnut (Corylus avellana L.) and hazelnut skin

Dietary fibre (DF) profiles of natural hazelnut, roasted hazelnut and hazelnut skin were analyzed. Insoluble (IDF) and soluble (SDF) DFs were examined for monosaccharide and glycosyl-linkage compositions using gas chromatography-mass spectrometry (GC-MS). Total DF contents of natural hazelnut, roasted hazelnut, and hazelnut skin were 17.8, 15.4, and 69.8%, respectively; majority of which (>96%) were water-insoluble. IDFs of natural and roasted hazelnuts were composed of cellulose (~49%), pectic polysaccharides (~30%), and xyloglucans (~15%), whereas that of hazelnut skin made up lignin (~55%) and fibre polysaccharides (cellulose, pectic polysaccharides, and xyloglucans, ~45%). Unlike the ones from other sources, pectic polysaccharides in IDFs had lower proportion of smooth region and higher proportion of hairy region that is heavily branched with arabinan and galactan side chains. Xyloglucans were also densely branched with monomeric and/or dimeric side chains. SDFs of the samples were composed of heavily branched heteromannans (~60%), slightly branched pectic polysaccharides (~25%), and xyloglucans possessing monomeric side chains (~5%). These results suggest that hazelnut is rich in DFs that have potential to improve large bowel function and hazelnut skin, a byproduct of hazelnut roasting process, could be utilized for the production of functional carbohydrates having prebiotic capacities.

Phenolic Compounds from Nuts: Extraction, Chemical Profiles, and Bioactivity

Nuts contain a vast array of phenolic compounds having important biological properties. They include substances allocated into the five major groups named phenolic acids, flavonoids, tannins, phenolic lignans, and stilbene derivatives. The complexity in composition does not allow for setting a universal extraction procedure suitable for extraction of all nut phenolics. The use of non-conventional extraction techniques, such as those based on microwave, ultrasound, and compressed fluids, combined with generally recognized as safe solvents is gaining major interest. With regard to the latter, ethanol, water, and ethanol-water mixtures have proven to be effective as extracting solvents and allow for clean, safe, and low-cost extraction operations. In recent years, there has been an increasing interest in biological properties of natural phenolic compounds, especially on their role in the prevention of several diseases in which oxidative stress reactions are involved. This review provides an updated and comprehensive overview on nut phenolic extraction and their chemical profiles and bioactive properties.

Changes in Antioxidant Activity, Profile, and Content of Polyphenols and Tocopherols in Common Hazel Seed (Corylus avellana L.) Depending on Variety and Harvest Date

The aim of the study was to evaluate the influence of variety and the date of harvest of hazelnut seeds on their antioxidant potential and the profile and content of polyphenols and tocopherols. The research material included the hazelnut seeds of six varieties, harvested from July to September at equal 30-day intervals. Hazelnuts were analyzed for total fat content and antioxidant properties, whereby UPLC-PDA-ESI-MS analysis was used to determine the profile and content of polyphenols, and the HPLC method to determine the content of tocopherols. It was found that the content of fat and tocopherols in nuts increased with the ripening of the nuts. The highest fat content was found in walnut seeds of the Kataloński variety (September) and tocopherols in walnut seeds of the Olbrzym z Halle variety (177.67 mg/kg d.m.). In turn, antioxidant properties and total polyphenols content decreased with the later harvest date. The strongest antioxidant potential was found in the case of Cosford nuts harvested in July (66.93 mmol TE/100 g d.m.). These nuts were also characterized by the highest total polyphenol content (1704.9 mg/100 g d.m.). UPLC-MS analysis allowed the identification of 15 polyphenolic compounds such as phenolic acids, catechins and ellagic acid hexoside in nut seeds.

Chemical modifications of Tonda Gentile Trilobata hazelnut and derived processing products under different infrared and hot-air roasting conditions: a combined analytical study

BACKGROUND

For the processing industry, it is crucial to know what effect the roasting process and conditions have on hazelnut quality. The present study investigates, for the first time, the effects of hot-air and infrared (IR) roasting at different time-temperature combinations on Tonda Gentile Trilobata hazelnut: whole kernels and derived processing products (paste and oil).

RESULTS

The nutritional and physical characteristics of hazelnuts and processing products were investigated to determine the influence of the different roasting conditions as a function of intended use. The antioxidant profile (2.2-diphenyl-1-picrylhydrazyl radical, oxygen radical absorbance capacity and total phenolic content) were analyzed on roasted hazelnut and paste extracts. For a comprehensive understanding of the complex biochemical phenomena occurring during roasting, E-nose and near-IR spectroscopy were also applied. All analytical data were processed using univariate and multivariate data analyses. Hazelnuts derived from IR roasting at higher temperatures (195 °C) showed a richer antioxidant profile and a more intense flavour. On the other hand, the yield associated with the oil extraction under the same conditions was unsatisfactory, making this process completely inadequate for oil production. Oil obtained by hot-air roasting and IR roasting at lower temperature (135 °C) was found to be of good quality, showing rather similar acidity grade, peroxide number and acidic composition. In particular, a slightly but significantly lower acidity was related to lower roasting temperatures (0.21-0.22% versus 0.27% for higher temperatures). All roasting conditions tested allowed the quantitative homogeneous hazelnut paste to be obtained and, from a rheological point of view, a higher roasting temperatures resulted in pastes characterized by higher density and viscosity values.

CONCLUSION

The use of IR was found to be a promising alternative method for hazelnut roasting, as a result of its capability with respect to preserving nutritional values and enhancing organoleptic quality. © 2018 Society of Chemical Industry.