Kaunas University of Technology,
Keywords: berry pomace, biorefining, functional ingredients, phytochemicals, antioxidants
Summary:According to the FAO, roughly one-third of edible agro-food materials for human consumption is lost or wasted. Currently the majority of agro-food waste generated during processing are used inefficiently, while they contain valuable nutritive substances, which may be converted into valuable ingredients. The International Energy Agency Bioenergy Task 42 on Biorefineries defined the concept of biorefining as: “a sustainable processing of biomass into a spectrum of bio-based products (food, feed, chemicals, and materials) and bioenergy (biofuels, power and/or heat)”. This concept should be wider applied for increasing the sustainability in utilization of agro-food resources towards development of “zero waste” processing technologies. Many berry species are known for their excellent flavor and abundance of healthy phytochemicals. However, due to a rapid decay after harvesting, the major part of berry crops is processed into longer shelf-life products. Pressing of fruit juice results in large quantities of by-products, which are called pomace. These residues are very rich in various valuable compounds; however, currently and in many cases they are used for animal feed and composting or even discarded as a waste, mainly due to a lack of scientific, technological and economic studies required for waste valorization by applying conventional and modern processing methods. This study provides examples of processing of raspberry [1, 2], black currant , chokeberry [4-6], bilberry , sea-buckthorn , guelder-rose berry , cranberry, blackberry and strawberry pomace into high value ingredients by using supercritical carbon dioxide, pressurized liquid, microwave hydro-diffusion and gravity, ultrasound-assisted, bead-milling and enzyme assisted extraction methods. It was demonstrated that different types of high value substances may be recovered from berry pomace by the combination of various methods. Firstly, lipophilic fractions consisting mainly of polyunsaturated fatty acid-rich triacylglycerols and tocopherols were recovered by supercritical carbon dioxide at optimized by Response Surface Methodology. At optimal conditions, the yields of oily extracts were dependent on berry species and were from 3% (chokeberry pomace) up to 20% in (raspberry pomace). The residue was further extracted by using subcritical water or its mixtures with ethanol (green solvents) at 10 MPa and different temperatures. This step, depending on berry type and process parameters, produced 20-60% of soluble fractions, and finally, enzyme assisted extraction  enabled to recover different amounts of water soluble substances such as oligosaccharides and others. Phytochemicals and bioactivities of fractions were analyzed by chromatography and mass spectrometry, while antioxidant properties were evaluated by the batch in vitro assays (ABTS, FRAP, ORAC, Folin-Ciocalteu values) and the on-line HPLC-UV-DPPH radical scavenging assay. The results indicate that the fractions isolated from berry pomace contain valuable bioactive compounds and may find applications in functional foods, nutraceuticals, cosmetics and other products. For instance, strong antioxidants recovered from raspberry , chokeberry and cranberry pomace improved oxidative and microbiological stability of meat products. Moreover, it is hypothesized that phytochemicals recovered from berry pomace might mitigate adverse effects (carcinogenic) of processed meat products to human health. Currently the preliminary studies of such effects on cancer cells are performed using in vitro digestion models.