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

Abstract

BackgroundHemicellulose 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.ResultsDifferent 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.ConclusionsModulation 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.

Recent Innovations on the Reuse of Almond and Hazelnut By-Products: A Review

“…Being a lignocellulosic material, the shell is mainly constituted by cellulose (15.4%), lignins (25.9%), and hemicellulose (22.4%), making up the majority of the fibre content of the shells. Phenolic compounds are also present in this fraction [96,111]. Phenolics could be exploited as valuable substances for possible effects on human health, including antioxidant, anti-inflammatory, and antimicrobial properties [96,109].…”

“…High antioxidant activity was detected for the polyphenolic phase of the extracts [109]. In relation to fibre content, Fuso et al [111] tested the use of a hydrothermal treatment performed at various temperatures to implement and optimise the extraction of these components from the shells. The results show that the highest extraction yield was obtained at 150 • C, followed by 175 • C, and it subsequently decreased at 200 • C. Moreover, different extraction temperatures also influenced the extraction profile in terms of monosaccharides, indicating that the highest amount of xylose derived from the 150 • C extraction.…”

“…Figure 4.Hazelnut by-products and innovative applications described in the literature for each fraction. Shell (fortified food[108], molecules extraction[96,[109][110][111][112][113], and materials[114][115][116][117]); skin (fortified food[118][119][120][121][122][123] and molecules extraction[96,109,110,124]); and oil cake (fortified food[125][126][127]). …”

Pomelo (Citrus grandis (L.) Osbeck) sponge layers as a potential source of soluble dietary fiber: Evaluation of its physicochemical, structural and functional properties

“…In the past, fibers such as wheat, corn and rice had been used for the production of SDF due to their health properties and technical features [ 4 ]. Nowadays, with the growing challenges of food security and environmental issues, there was an increased interest in the high-value utilization of agricultural waste [ 5 ]. Additionally, consumer interested in healthy, nutritious and clean-labeled foods were on the rise.…”

“…By-products of fruits and vegetables processing had been reported to be a rich source of novel and economical functional health ingredients, including peel, stems and cores [ 6 ]. However, these by-products were usually disposed of in the form of landfills or incineration, and small amounts were consumed through animal feed [ 5 ]. Therefore, it is necessary to develop some methods to utilize these by-products and wastes.…”