Document Type

Theses, Ph.D


Available under a Creative Commons Attribution Non-Commercial Share Alike 4.0 International Licence

Publication Details

Thesis successfully submitted for the award of Doctor of Philosophy (Ph.D.) to the Technological University Dublin in 2014.


By-products from the cider and brewing industries, including apple pomace (AP) and brewer’s spent grain (BSG) respectively, constitute major environmental problems due to the large quantities produced every year. They are sources of valuable compounds such as protein, fibre, essential fatty acids, phenolic compounds and minerals, some of them with antioxidant and prebiotic properties. Their high nutritional value leads to their potential use as human food products and several applications have been considered recently. The aims of this work include i) the nutritional and compositional characterisation of AP, BSG and final extruded and baked prototypes containing these by-products and ii) the extraction of the bioactive compounds present using environmentally green methods for potential food applications. The nutritional and compositional characterisation showed that AP contained mainly carbohydrates (51 %) and fibre (42 %) while BSG was composed mainly of fibre (61 %) and protein (21 %) and both were a potential source of antioxidants. The content of fibre and antioxidant properties of baked scones and extruded snacks increased with incorporation of up to 20 % of AP with no loss of nutritional value. The same findings were observed for breadsticks and extruded snacks incorporated with up to 20 % of BSG with an increase also in protein content. AP phenolic extracts with high antioxidant activities were produced by extraction with water and food compatible aqueous organic solvents (40 % methanol and 40 % acetone). Arabinoxylans (AX) -rich extracts from BSG with high prebiotic potential were produced by ultrasound-assisted extraction (UAE), with a significant reduction of time and less energy consumption than the conventional method used. AP and BSG are possible ingredients in enhancing some baked and extruded snacks properties and possible sources for isolating antioxidants and prebiotics.