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Projeto de investigação
Resgate de bolotas com um Superalimento Tradicional Mediterrânico - PRIMA/0005/2022
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Publicações
Comparison of nutritional and bioactive properties of acorn flour with and without tannins
Publication . Ben Rhouma, Hiba; Carocho, Márcio; Barros, Lillian
The Quercus spp. are a varied group of evergreen and deciduous trees native to temperate and tropical regions. There are about 600 species of Quercus worldwide, which differ in their flowering and fruiting dynamics as well as maturity index. Acorns, the nuts of Quercus spp. trees, offer a comprehensive nutritional profile, being rich in proteins, fibers, starch, bioactive compounds including tannins and phenolic acids, essential vitamins, like vitamins A and E, and minerals, such as potassium, iron, calcium, and magnesium. However, this fruit presents a problem for the food industry regarding the astringency caused by tannins, which are anti-nutrients found in acorns. Therefore, this study aims to evaluate the potential of acorn flour for the baking industry by comparing the nutritional value and bioactive compounds of acorn flour with and without tannins. The whole flour (SPM21) and a tannin-free flour (SPM21F4) were analysed, having both been supplied by the company Landratech. The elimination of tannins, which was accomplished by leaching the flour three times with water at 15 °C, resulted in a reduction in several nutrients, such as crude protein, ash, and fiber. However, the SPM21F4 flour showed increased levels of moisture, crude fat, starch, total carbohydrates, and energy content. Soluble sugars were found exclusively in the SPM21 flour, indicating that the leaching treatment affected the sugar content in the SPM21F4 sample. The fatty acid profile of the SPM21F4 flour revealed higher levels of polyunsaturated fatty acid (PUFA) and monounsaturated fatty acid (MUFA), while the flour containing tannins had higher levels of saturated fatty acids (SFA). Ten phenolic compounds were detected, and the tannin free flour had a much lower overall phenolic content. In conclusion, properly processed acorn flour can improve the nutritional profile of bread by providing bioactive chemicals and appealing sensory features, hence increasing its popularity in the baking business. However, further research is needed to optimize tannin extraction and fully understand the nutritional and industrial potential of acorn flour.
Exploring acorn shells: Phenolic composition and bioactive potential for sustainable valorization
Publication . Mateus, Cristiano; Alonso-Esteban, José Ignacio; Finimundy, Tiane C.; Mandim, Filipa; Oliveira, Izamara; Babo, Pedro; Ferreira, Isabel C.F.R.; Barros, Lillian
Pedunculate (Quercus robur L.), holm (Quercus rotundifolia Lam.), and cork (Quercus suber L.) oaks are abundant across the Portuguese landscape. This study aims to evaluate the phenolic composition and bioactivities of acorn shell samples and determine their potential as a functional compound source. In total, five acorn shell samples collected in different locations and from different species were analyzed: Q. rotundifolia (Q. rot-1 and Q. rot-2), Q. suber (Q. sub-1 and Q. sub-2) and Q. robur (Q. rob-1). A total of nine phenolic compounds were tentatively identified, namely gallic and ellagic acids and derivatives. Digalloyl hexoside was the compound detected in higher concentrations in all extracts (2.093 – 8.3 mg/g extract). Q. suber samples exhibited the lowest IC50 values for TBARS assay, lower than the positive control used (Trolox). Overall, the studied samples demonstrated the capacity to inhibit the proliferation of all tumor cell lines tested. Sample Q. sub-1 demonstrated the most promising antibacterial capacity. According to the results, the acorn shell extracts exhibited promising potential, and it may be interesting to conduct a deeper study on the samples of this species.
Smart carving of hard-shell fruit with CO2 laser
Publication . Farrero, Bernardo; Babo, Pedro; Ribeiro, Luís Frölén
The application of CO₂ laser technology in food processing has gained significant attention due to its precision and adaptability. This study presents an intelligent system for carving hard-shell fruits, specifically acorns, to facilitate their shelling process. The proposed approach integrates real-time control and monitoring technologies to enhance precision and efficiency. A key challenge in acorn processing is the size and shell thickness variability, which complicates mechanical carving. The developed system employs a CO₂ laser to create precise incisions, ensuring optimal shell cracking during dehydration while preventing kernel damage. Experimental tests conducted at the Polytechnic Institute of Bragança identified optimal parameters—6 seconds of laser exposure at 40𝑊 power—for consistent and controlled carving. A thoughtful analysis system was implemented to assess pre- and post-carving
conditions, enabling real-time adjustments to laser settings. This self-optimizing process improves the efficiency of the shell carving while reducing waste. The results demonstrate the feasibility of automated acorn carving using CO₂ laser technology, offering a scalable solution for industrial food processing with continuous control of the shell incision. Future research could explore advanced automation techniques to enhance system robustness and adaptability to different fruit types.
Acorn pre-drying: implications for the food industry
Publication . Farrero, Bernardo; Ribeiro, Luís Frölén; Famiglietti, Antonio; Babo, Pedro
In industry, 74% of the energy consumed is used in the form of heat. The food sector is characterised by a high share of processes that rely on industrial heat [1]. However, 90% of this thermal energy currently comes from fossil fuels, and only 9% is supplied by renewable sources [2]. The adoption of solar thermal technologies in the food industry offers multiple benefits that support its viability as an energy alternative to overcome this caveat. Firstly, by relying on a renewable and stable source. Manufacturers can reduce production costs and limit their exposure to the volatility of fossil fuel prices, thereby ensuring greater long-term price stability and predictability [3]. These reductions in energy costs may also be reflected in lower prices for the end consumer. Solar-assisted dehydration enables a decrease in moisture content, thereby limiting microbial growth and food spoilage [3]. In this regard, Solar Heat for Industrial Processes (SHIP) may also address food security concerns as storage losses are estimated to reach up to 20%, posing a critical challenge to food security [4].
The installation of in-situ pre-dehydration systems near harvesting zones provides clear benefits for energy efficiency and product quality. The Iberian Peninsula, notably, benefits from very high solar radiation, with many clear-sky days and extended sunlight periods, making it particularly suitable for solar-based pre-dehydration systems. By lowering produce weight and moisture before transportation, these systems decrease fossil energy demand during both industrial drying and large-scale transport [5]. This approach reduces the final product cost, as demonstrated by an in-situ solar dryer used for acorns in Alentejo holm oak groves. The passive, indirect mobile dryer, fitted with hanging bags, reduces acorn moisture content by 15% after 72 hours of drying, delays fruit spoilage, and cuts large-scale industrial heat input [6,4]. Thermal energy data from a factory case at Landratech, an acorn food producer involved in the MEDACORNET project, indicate that 15% in-situ pre-dehydration cuts thermal energy use by 52% during both initial and final drying stages of acorn flour manufacture [3]. This combined method lowers fossil fuel use, reduces losses, improves energy efficiency, and supports sustainability in the food processing sector.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
PRIMA Section 2 - 2022
Número da atribuição
PRIMA/0005/2022