Abstract
The increase in diet-related chronic diseases has prompted the search for health-promoting compounds and methods to ensure their quality. Blueberry pomace is a rich yet underutilized source of bioactive polyphenols. For these high-value bioactive molecules, ultrasound-assisted extraction (USAE) is an attractive and green alternative to conventional extraction techniques for improving purity and yields. This study aimed to assess the impact of USAE parameters (sonication time, solvent composition, solid/liquid ratio, pH and temperature) on the recovery of phenolic compounds from blueberry pomace and antioxidant activity of the extracts. Total phenolic, flavonoid and anthocyanin contents (TPC, TFC and TAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity were analysed. USAE in 50% ethanol/water was the most efficient, yielding the highest TPC (22.33 mg/g dry matter (DM)), TFC (19.41 mg/g DM), TAC (31.32 mg/g DM) and DPPH radical scavenging activity (41.79 mg Trolox/g DM). USAE in water showed the lowest values even at low (1/40) solid/liquid ratio (7.85 mg/g DM, 3.49 mg/g DM, and 18.96 mg/g DM for TPC, TFC and TAC, respectively). Decreasing the solid/liquid ratio in water or 50% ethanol significantly increased TPC, TFC, TAC and DPPH radical scavenging. With ethanol, increasing the temperature in the range 20–40 °C decreased TPC but increased TFC and DPPH radical scavenging activity. Anthocyanin profiles of water and ethanolic extracts were qualitatively similar, consisting of malvidin, delphinidin, petunidin and cyanidin. These findings indicate that USAE is a method of choice for extracting high-value bioactive phenolics from blueberry pomace. Selective enrichment of different phenolic fractions is possible under select extraction conditions.
Highlights
Polyphenols are natural secondary metabolites produced by plants
This study is the first to investigate the influence of ultrasound-assisted extraction (USAE) conditions on the recovery of phenolic compounds from blueberry pomace and antioxidant activity of the extracts
The present study showed that the efficiency of ultrasound-assisted extraction of phenolic compounds from blueberry pomace is significantly influenced by the proportion of ethanol in the aqueous solvent, solid/solvent ratio, extraction temperature, sonication time and pH
Summary
Polyphenols are natural secondary metabolites produced by plants. They are classified into different groups as phenolic acids (derivatives of benzoic acid and cinnamic acid), flavonoids (flavonols, flavones, isoflavones, flavanones, anthocyanidins and flavanols (e.g., catechins and proanthocyanidins)), stilbenes and lignans [1]. Polyphenols are known for their strong antioxidant properties and potential health benefits, including the prevention of chronic illnesses such as cardiovascular diseases, type 2 diabetes, osteoporosis, neurodegenerative diseases and some cancers, their protective action goes beyond the modulation of oxidative stress [2] They are increasingly used as nutritional supplements, nutraceuticals, as well as ingredients in foods, functional foods, pharmaceutical and cosmetic products. Berries such as blueberries (Vaccinium section Cyanococcus spp.) contain abundant phenolic compounds, including anthocyanins (derived from anthocyanidins by glycosylation), flavonols and chlorogenic acids, which are mainly found in berry skin [3,4,5]. Blueberry production in Canada, the second largest producer worldwide after the United States, reached 176,641 tons in
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