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The use of by-products as a source of bioactive compounds with economic added value is one of the objectives of a circular economy. The olive oil industry is a source of olive pomace as a by-product. The olive pomace used in the present study was the exhausted olive pomace, which is the by-product generated from the air drying and subsequent hexane extraction of residual oil from the olive pomace. The objective was to extract bioactive compounds remaining in this by-product. Various types of green extraction were used in the present study: solvent extraction (water and hydroalcoholic); ultrasound-assisted extraction; Ultra-Turrax-assisted extraction; and enzyme-assisted extraction (cellulase; viscoenzyme). The phenolic profile of each extract was determined using HPLC-DAD and the total phenolic content (TPC) and antioxidant activity (ABTS, DPPH, and ORAC) were determined as well. The results showed significant differences in the yield of extraction among the different methods used, with the enzyme-assisted, with or without ultrasound, extraction presenting the highest values. The ultrasound-assisted hydroethanolic extraction (USAHE) was the method that resulted in the highest content of the identified phenolic compounds: 2.021 ± 0.29 mg hydroxytyrosol/100 mg extract, 0.987 ± 0.09 mg tyrosol/100 mg extract, and 0.121 ± 0.005 mg catechol/100 mg extract. The conventional extraction with water at 50 °C produced the best results for TPC and antioxidant activity of the extracts. The extracts from the USAHE were able to inhibit Gram-positive bacteria, especially Bacillus cereus , showing 67.2% inhibition at 3% extract concentration.

BACKGROUND The olive oil industry generates significant amounts of semi‐solid wastes, namely olive pomace. Olive pomace is a by‐product rich in high‐value compounds (e.g. dietary fibre, unsaturated fatty acids, polyphenols) widely explored to obtain new food ingredients. However, conventional extraction methods frequently use organic solvents, while novel eco‐friendly techniques have high operational costs. The development of powdered products without any extraction step has been proposed as a more feasible and sustainable approach. RESULTS: The present study fractionated and valorized the liquid and pulp fraction of olive pomace obtaining two stable and safe powdered ingredients, namely a liquid‐enriched powder (LOPP) and a pulp‐enriched powder (POPP). These powders were characterized chemically, and their bioactivity was assessed. LOPP exhibited a significant amount of mannitol (141 g kg−1), potassium (54 g kg−1) and hydroxytyrosol derivatives (5 mg g−1). POPP exhibited a high amount of dietary fibre (620 g kg−1) associated with a significant amount of bound phenolics (7.41 mg GAE g−1 fibre DW) with substantial antioxidant activity. POPP also contained an unsaturated fatty acid composition similar to that of olive oil (76% of total fatty acids) and showed potential as a reasonable source of protein (12%). Their functional properties (solubility, water‐holding and oil‐holding capacity), antioxidant capacity and antimicrobial activity were also assessed, and their biological safety was verified. CONCLUSIONS: The development of olive pomace powders for application in the food industry could be a suitable strategy to add value to olive pomace and obtain safe multifunctional ingredients with higher health‐promoting effects than dietary fibre and polyphenols. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Olive pomace management represents a great concern to the olive oil industry. This work focused on the development of a "zero waste" strategy for olive pomace based on a fractionation approach resulting in the obtention of different value-added fractions. The physicochemical composition of edible fractions obtained (liquid and pulp) was analysed. The potential use as a solid biofuel of the non-edible fraction (stones) was evaluated. High amounts of hydroxytyrosol (513.61–625.76 mg/100 g dry weight) were present in the liquid fraction. Pulp fraction was demonstrated to be a good source of fibre (53–59% dry weight) with considerable antioxidant activity both from free and bound phenolics. The stones fraction exhibited substantial high heating values (18.65–18.94 megajoule (MJ/kg). All these results support the added value of the olive pomace fractions combining the biofuel potential from the stones fraction and the functional food ingredients' potential both from liquid and pulp fractions. The present methodology seems to be a feasible whole valorisation approach to achieve the circularity in the olive oil sector, prioritising obtaining high over low added-value products. [ABSTRACT FROM AUTHOR]

Liquid-enriched powder (LOPP) and pulp-enriched powder (POPP) obtained from olive pomace were incorporated into yoghurt, not only, to increase its content in dietary fibre, hydroxytyrosol and unsaturated fatty acids, but also to understand the lipids-phenolics interaction by simultaneous incorporation of olive oil. POPP (2%) and LOPP (1%) addition to yoghurt allowed fulfilling the condition of being a "source of fibre" and provided 5 mg of hydroxytyrosol and derivatives in a standard yoghurt (120 g), respectively. Yoghurts' unsaturated fatty acids profile was positively influenced by the addition of only POPP and olive oil + LOPP or + POPP. All OP powder-fortified yoghurts exhibited higher total phenolic content and antioxidant activity than the control (p < 0.05). After in vitro digestion the bioaccessibility of total phenolics (more 25.58%) and hydroxytyrosol (more 68.71%) in LOPP-yoghurts was improved by the addition of olive oil. In conclusion, OP powderś incorporation gave additional and essential healthy properties to yoghurt. Image 1 • Powders obtained from olive pomace exhibited potential as food ingredients. • Yoghurt with POPP (2%) fulfilled the nutritional claim "source of fibre". • LOPP (1%) provides 5 mg of hydroxytyrosol and derivatives in a standard yoghurt. • POPP and olive oil addition enhanced yoghurts' profile. • Olive oil addition improved the hydroxytyrosol bioaccessibility in LOPP-yoghurts. [ABSTRACT FROM AUTHOR]