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.

ONE QUALITY concept: a narrative perspective to unravel nutritional challenges, controversies, and the imperative need of transforming our food systems.

Ensuring a healthy and sustainable diet for all should be a global priority, and to achieve this goal the food system requires substantial changes. Adopting a one-size-fits-all approach is not feasible, and we need to consider the cultural particularities of each geography and not try to export models that work in one place but may be unsustainable in others. Our discussion will center on two key aspects within this overarching process: (a) the combination of a rigorous evidence-based approach with existing or proposed Nutritional Guidelines and policies required to realize the "ONE HEALTH" and "ONE QUALITY" concepts. Examining the Mediterranean diet and the latest findings on saturated fats will aid us in comprehending the necessary paradigm shift required to formulate new guidelines with substantial impact in preventing the rising prevalence of Non-Communicable Diseases worldwide; (b) the adequacy and scope of the data bank necessary to develop a global, science-based approach.

A multiplatform metabolomics/reactomics approach as a powerful strategy to identify reaction compounds generated during hemicellulose hydrothermal extraction from agro-food biomasses.

Hydrothermal treatment is commonly used for hemicelluloses extraction from lignocellulosic materials. In this study, we thoroughly investigated with a novel approach the metabolomics of degradation compounds formed when hazelnut shells are subjected to this type of treatment. Three different complementary techniques were combined, namely GC-MS, 1H NMR, and UHPLC-IM-Q-TOF-MS. Organic acids, modified sugars and aromatic compounds, likely to be the most abundant chemical classes, were detected and quantified by NMR, whereas GC- and LC-MS-based techniques allowed to detect many molecules with low and higher Mw, respectively. Furans, polyols, N-heterocyclic compounds, aldehydes, ketones, and esters appeared, among others. Ion mobility-based LC-MS method was innovatively used for this purpose and could allow soon to create potentially useful datasets for building specific databases relating to the formation of these compounds in different process conditions and employing different matrices. This could be a very intelligent approach especially in a risk assessment perspective.

Plant-Based: A Perspective on Nutritional and Technological Issues. Are We Ready for "Precision Processing"?

The rapid evolution of consumers' preference despite being still rooted in taste is rapidly combining with an exponential growth of environmental awareness. Both are forcing innovation into the food industry sector. Today, it is common in the scientific literature to find awareness of nutrition and sustainability, functionality and freshness, taste, and pollution; the most relevant and recognized trends are evolving with unprecedent speed toward a new paradigm. The perfect storm of fast-growing population, together with an exploding level of environmental pollution, is combining with the request for functional foods with more defined health properties and is strongly pushing the food sector to new defined innovation objectives to keep and develop the economic role of most loved brands around the world. The most debated conundrum is how to provide healthy food for all human beings, without further affecting our Mother Earth. Innovation in food raw materials as well as innovation in food processing seems to be the magic solution to provide twice with half, that is, to double the food production combined with declining resources. One of the fastest growing segments in the food industry is the plant-based segment. The status of the available options in food processing applied to plant-based food will be discussed, with a special focus on novel physical processing technologies and atomic force microscopy as possible complementary weapons in science-based definition of a sustainable nutrition approach. A call for a new paradigm such as "precision processing" should be adopted to drive the evolution of the whole food system.

Oxysterols as Reliable Markers of Quality and Safety in Cholesterol Containing Food Ingredients and Products.

Cholesterol is a lipid of high nutritional value that easily undergoes oxidation through enzymatic and non-enzymatic pathways, leading to a wide variety of cholesterol oxidation products (COPs), more commonly named oxysterols. The major oxysterols found in animal products are 7α-hydroxycholesterol, 7ß-hydroxycholesterol, 7-ketocholesterol, 5α,6α-epoxycholesterol, 5ß,6ß-epoxycholesterol, cholestan-3ß,5α,6ß-triol, and 25-hydroxycholesterol. They are all produced by cholesterol autoxidation, thus belonging to the non-enzymatic oxysterol subfamily, even if 7α-hydroxycholesterol and 25-hydroxycholesterol are, in part, generated enzymatically as well. A further oxysterol of the full enzymatic origin has recently been detected for the first time in milk of both human and bovine origin, namely 27-hydroxycholesterol. Nowadays, gas or liquid chromatography combined to mass spectrometry allows to measure all these oxysterols accurately in raw and in industrially processed food. While non-enzymatic oxysterols often exhibited in vitro relevant cytotoxicity, above all 7ß-hydroxycholesterol and 7-ketocholesterol, 27-hydroxycholesterol, as well as 25-hydroxycholesterol, shows a broad spectrum in vitro antiviral activity, inhibition of SARS-CoV-2 included, and might contribute to innate immunity. Quantification of oxysterols was afforded over the years, almost always focused on a few family's compounds. More comprehensive COPs measurements, also including oxysterols of enzymatic origin, are, nowadays, available, which better display the many advantages of systematically adopting this family of compounds as markers of quality, safety, and nutritional value in the selection of ingredients in processing and storage. Regarding foodstuff shelf life, COPs monitoring already provided useful hints for more suitable packaging. The identification of a subset of non-enzymatic and enzymatic oxysterols to be routinely assessed in food production and storage is proposed.

Production of xylo-oligosaccharides (XOS) of tailored degree of polymerization from acetylated xylans through modelling of enzymatic hydrolysis.

Xylo-oligosaccharides (XOS) are emerging prebiotics that have recently been gained a great interest in the market of functional foods. Since their beneficial activity strictly depends on their chemical structure and on their degree of polymerization (DP), in this work an enzymatic method was developed to produce XOS with variable and modellable DPs, involving a combination of a commercial endo-ß-1,4-xylanase M3 from Trichoderma longibrachiatum and a deacetylase, using a commercial acetylated standard xylan as substrate. A Design of Experiment (DoE) was developed and through the variation of some hydrolysis conditions, some experiments allowed to obtain significant amounts of XOS with DP 7-10, up to 11%, despite XOS with DP 2-4 were always the most abundant (60-96% of total XOS). The most impacting parameter on the XOS distribution was the order of addition of the xylanase and deacetylating enzyme, while pH showed to have a great influence on the total yield. The method was also tested on an acetylated xylan extracted from grape stalks, structurally similar to the commercial standard xylan. The model was found to work in a very similar way also on the non-purified xylan sample, allowing the manipulation of enzymatic hydrolysis on a low-cost by-product, with the potential to obtain on a large scale XOS with high added value and with a specific DP, depending on the final application.

Potential Valorization of Hazelnut Shells through Extraction, Purification and Structural Characterization of Prebiotic Compounds: A Critical Review.

Hazelnuts are one of the most widely consumed nuts, but their production creates large quantities of by-products, especially shells, that could be upcycled into much more valuable products. Recent studies have shown that hazelnut shell hemicellulose is particularly rich in compounds that are potential precursors of xylooligosaccharides and arabino-xylooligosaccharides ((A)XOS), previously defined as emerging prebiotics very beneficial for human health. The production of these compounds on an industrial scale-up could have big consequences on the functional foods market. However, to produce (A)XOS from a lignocellulosic biomass, such as hazelnut shell, is not easy. Many methods for the extraction and the purification of these prebiotics have been developed, but they all have different efficiencies and consequences, including on the chemical structure of the obtained (A)XOS. The latter, in turn, is strongly correlated to the nutritional effects they have on health, which is why the optimization of the structural characterization process is also necessary. Therefore, this review aims to summarize the progress made by research in this field, so as to contribute to the exploitation of hazelnut waste streams through a circular economy approach, increasing the value of this biomass through the production of new functional ingredients.

An effective chromatographic fingerprinting workflow based on comprehensive two-dimensional gas chromatography - Mass spectrometry to establish volatiles patterns discriminative of spoiled hazelnuts (Corylus avellana L.).

The volatile fraction of hazelnuts encrypts information about: cultivar/geographical origin, post-harvest treatments, oxidative stability and sensory quality. However, sensory features could be buried under other dominant chemical signatures posing challenges to an effective classification based on pleasant/unpleasant notes. Here a novel workflow that combines Untargeted and Targeted (UT) fingerprinting on comprehensive two-dimensional gas-chromatographic patterns is developed to discriminate spoiled hazelnuts from those of acceptable quality. By flash-profiling, six hazelnut classes are defined: Mould, Mould-rancid-solvent, Rancid, Rancid-stale, Rancid-solvent, and Uncoded KO. Chromatographic fingerprinting on composite 2D chromatograms from samples belonging to the same class (i.e., composite class-images) enabled effective selection of chemical markers: (a) octanoic acid that guides the sensory classification being positively correlated to mould; (b) Æ´-nonalactone, Æ´-hexalactone, acetone, and 1-nonanol that are decisive to classify OK and rancid samples; (c) heptanoic and hexanoic acids and Æ´-octalactone present in high relative abundance in rancid-solvent and rancid-stale samples.