Food Security beyond Cereals: A Cross-Geographical Comparative Study on Acorn Bread Heritage in the Mediterranean and the Middle East

This article aims to contribute to the limited literature on traditional gastronomic knowledge concerning acorn-based bread by ethnographically documenting the ingredients, preparation techniques and consumption practices of baked goods made from acorn seeds and flour that are still used today or at least still present in living memory. A qualitative comparative case method was adopted, and ethnographic data were gathered from 67 people in six selected Mediterranean, Central Asian and Middle Eastern countries. The analysis highlighted distinct trajectories in the development of acorn-based bread, showing some differences in terms of ingredients, preparation techniques and baking methods in the two cultural and geographical macro-regions. By exploring the evolution of the alimentary role of acorn bread in the past century, our findings also support the hypothesis that the product, at least during the last two centuries, has mostly been used as a famine food. By acknowledging the cultural importance of acorn fruits and acorn-based products, this study suggests that the rediscovery of acorn-based products and associated traditional knowledge may foster the sustainable development of rural and marginal regions in the Mediterranean, Middle East and Central Asia. This could help to reinforce the resilience of local communities and thus increase food security. Furthermore, reassessing acorns as a foodstuff may aid in developing innovative products in line with emerging trends in the food sector, which is looking for new non-cereal-based bakery products and other novel culinary applications.

Valorization and Development of Acorn Starch as Sustainable and High-Performance Papermaking Additive for Improving Bagasse Pulp and Paper Properties

Improving bagasse pulp and paper properties using forest-byproduct biomass, native Acorn starch (NAS), was compared with conventional wet-end additive cationic corn starch (CCS). The extracted acorn starch was characterized by SEM, XRD, and GPC. The results clearly showed irregular granular shape (6-12 μm) with rough surfaces, C_A-type XRD pattern, and 436.2 kDa molecular weights for NAS. The bagasse pulp retention and drainage as keys of operation performance and runnability were superior by NAS in comparison with CCS, while the lowest dosage of NAS (0.5%) showed superior results than the highest dosages of CCS (1% & 1.5%). The higher NAS adsorption onto the fiber surfaces compared to CCS could be concluded by higher water retention value (WRV) of the pulp together with higher density (up to 20%) and mechanical properties of the produced paper, e.g., tensile (up to 63%), burst (up to 37%) and tear (up to 11%) indices. NAS exploiting naturally as a papermaking additive would provide performance higher than commercial chemically-modified starch.

The Rheological Performance and Structure of Wheat/Acorn Composite Dough and the Quality and In Vitro Digestibility of Its Noodles

Wheat flour was partially replaced by debittered acorn flour (DAF) with 0%, 10%, 15%, 20% as well as 25%. Rheological properties of wheat/acorn dough and quality and in vitro digestibility of its noodles were determined. Results showed that DAF addition significantly improved pasting viscosity and dough stability time while excessive addition weakened the protein network and decreased maximum fermentation height. Furthermore, noodles with substitutions exhibited promising technological properties as a food ingredient for noodle making (higher hardness, chewiness, gumminess, firmness, and less cooking time) but poor extensibility, smaller lightness values, and a slight deterioration in cooking quality. Furthermore, PCA and correlation analysis demonstrated a significant relationship between textural and cooking properties and pasting and mixing parameters. Moreover, SEM images of acorn noodles presented coarser surfaces but a tighter cross-section structure. Finally, in vitro digestibility results indicated that DAF addition significantly reduced the susceptibility of the starches to enzyme hydrolysis, while the addition of acorn flour slightly decreased the overall acceptability. Thus, the partial substitution of wheat flour with acorn flour can favorably be used in noodles formulation.

Direct Ethanol Production from Xylan and Acorn Using the Starch-Fermenting Basidiomycete Fungus Phlebia acerina

During our search for ethanol-producing basidiomycete fungi for a wide range of substrates, we isolated Phlebia acerina, which is a white rot basidiomycete fungus. It favorably converted starch into ethanol with approximately 70% yield. Although the yield decreased as the starch concentration increased, growth and fermentation were observed even at 200 g/L of starch. P. acerina produced ethanol from glucose, galactose, mannose, xylose, cellobiose, and maltose with 93%, 91%, 86%, 72%, 92%, and 68% yields, respectively. Additionally, P. acerina, which secreted xylanase and xylosidase, was capable of assimilating xylan and directly converting it to ethanol with a yield of 63%. Furthermore, P. acerina produced ethanol directly from acorns, which are plant fruits containing starch and tannins, with a yield of 70%. Tannin delayed mycelia growth, thus prolonging ethanol production; however, this did not particularly affect the yield. These results were similar to those of fermentation in a medium with the same amounts of starch and tannin as the target crop acorn, thus suggesting that P. acerina could successfully produce environmentally friendly ethanol from starch-containing lignocellulosic biomass, unlike previously reported ethanol-producing basidiomycete fungi.

Composition, Physicochemical Properties, and Uses of Acorn Starch

The major component of acorn is starch, which may amount up to 55% of the dry weight. Lack of systematic knowledge on acorn starch greatly hinders the further development of acorns as sustainable crops. This review aims to summarize the current knowledge of the isolation, chemical composition, physicochemical properties, and uses of acorn starches and to provide future research directions. The amylose content of the acorn starches is reported to vary in the range of 20–39%. Moisture content, lipid, ash, and protein contents of the acorn starches have been reported varying from 2.20 to 15.50%, 0.23 to 2.64%, 0.01 to 1.41%, and 0.01 to 6.7%, respectively. Thermal and pasting properties that have usually been determined using differential scanning calorimeter (DSC) and rapid viscoanalyzer (RVA) are also discussed in this article. Acorn starch has great potential for various food and nonfood applications due to the unique structural and functional features.

Biobutanol production from municipal solid waste: Technical and economic analysis

Novel processes for the production of acetone-butanol-ethanol (ABE) from municipal solid waste (MSW) were developed and simulated using Aspen Plus®. In scenario 1, a conventional distillation system was used, while a gas stripping system was coupled with a fermenter in scenario 2. In scenario 3, pervaporation (PV) and gas stripping systems right after the fermentation reactor were applied. Gas stripping increased the total ABE produced while the addition of the PV module decreased the number of distillation columns from 6 to 2 as well as created 6.4% increments in the amount of butanol in comparison with scenario 1. Economical evaluation resulted in having payout periods of 15.9, 4.4, and 2.9 years for scenarios 1 to 3, respectively. These results show that using MSW as an inexpensive sugar-rich feedstock together with gas stripping PV system is a promising solution to overcome the major obstacles in the way of the ABE production.

Efficient biohydrogen and advanced biofuel coproduction from municipal solid waste through a clean process

The cleanest form of energy, i.e., biohydrogen, and advanced biofuel, i.e., biobutanol, were produced from the organic fraction of municipal solid waste (OFMSW). Ethanol as a byproduct of this process was used for the pretreatment of this substrate, and this pretreatment was improved by other process byproducts, i.e., acetic acid and butyric acid. The pretreatment was conducted with 85% ethanol and 0-1% (w/w) acetic/butyric acid at 120 and 160 °C for 30 min. The pretreatment catalyzed by 1% (w/w) acetic acid at 120 °C resulted in a hydrolysate with 49.8 g/L total fermentable sugars, which was fermented to the highest overall yield of acetone, butanol, and ethanol (ABE) and hydrogen. Through this process, 114.1 g butanol, 43.8 g acetone, 15.1 g ethanol, 97.5 L hydrogen were obtained from each kg of OFMSW, producing 270 g ABE and 151 L H₂ from each kg of substrate, corresponding to 6000 kJ energy production.

Simultaneous organosolv pretreatment and detoxification of municipal solid waste for efficient biobutanol production

Municipal solid waste (MSW) was used as a source for biobutanol production via acetone, butanol, and ethanol (ABE) fermentation. Organosolv pretreatment was used for simultaneous extraction of inhibitors, particularly tannins, and pretreatment of lignocellulosic fraction prior to hydrolysis. The hydrolysates of the pretreated MSW contained appreciable amounts of sugars and soluble starch together with a tolerable amount of inhibitors for Clostridium acetobutylicum. The hydrolysate obtained from MSW pretreated with 85% ethanol at 120 °C for 30 min fermented to the highest ABE concentration of 13.06 g/L with the yield of 0.33 g/g carbon source. Through this process, 102.4 mg butanol, 40.16 mg acetone, and 13.14 mg ethanol were produced from each g of organic fraction of MSW (OFMSW). The pretreatment at mild conditions with higher ethanol concentration accompanied with the lowest glucose yield (0.145 g/g) and the highest starch recovery resulted in the uppermost ABE yield of 0.16 g/g OFMSW.

Integrated ethanol and biogas production from pinewood

Efficient conversion of cellulose to ethanol and hemicellulose to biogas after dilute acid pretreatment.