Background: Seaweed is an underutilised food source in Britain, despite being abundant on the surrounding shores, it is only found in localised dishes such as laverbread . Seaweed has been shown to be a source of basic nutrients such as protein and fibre as well as a source of vitamins and minerals. It has been identified as potential source of bioactive compounds including antioxidants. The seaweed Ascophylfum nodosum is an edible brown seaweed common to the British Isles. The main aims of this study were to evaluate if ultrasound-assisted extraction (UAE) was an efficient and environmentally friendly alternative to conventional solvent extraction for extracting antioxidants from of dried Ascophyllum nodosum; to analyse the effect of particle size, agitation and heat treatment on extraction; and to evaluate physical characteristics and consumer acceptability of a bakery product (crackers) containing different levels of the seaweed sample. Methods: The dried seaweed samples were treated at ultrasound amplitudes of 30, 70 and 100~m and compared against conventional solvent extraction. To evaluate impact of heat and time on extraction, samples were heated to 160°C, 180°C, 2000C and 220°C without ultrasound treatment and were treated for periods of 5,10,15 and 20 min. The bioactives were assessed by chemical assays . . To investigate feasibility of inclusion in the UK diet, the seaweed was incorporated into crackers at 5,10,15 and 20% levels with both particle sizes. Results: The investigation found particle size to have a significant impact on the antioxidant capacity with the fine grade (300 - 45~m) Ascophy/lum nodosum producing extracts with higher antioxidant capacity across all amplitudes. It was also observed that the addition of a shaking pre-treatment significantly improved the antioxidant capacity at all amplitudes and with both particle sizes (p<0.05). The use of water as a solvent compared to methanol was found to improve the antioxidant capacity; this was found to be significant across all tests at 70~m amplitude (p<0.05). In all the assays the ultrasound treated extracts showed a significant (p<0.05) improvement upon the control. The ultrasound treatment was shown to have a greater effect on the medium grade (355 - 850 ~m) Ascophyllum nodosum. The addition of heat decreased the antioxidant capacity at all time and temperatures when compared to the control. The colour of the seaweed was shown to change with the addition of heat over a period of time. The crackers produced with the fine grade Ascophyllum nodosum were considered unpalatable across all incorporations, the medium grade scored higher than the fine. The sample with 5% medium grade inclusion showed no significant difference to the control and was considered palatable. Conclusion: Ultrasound has shown to significantly improve the solid liquid extraction bioactive yield from Ascophyllum nodosum. The use of a shaking during the sol id liquid extraction and use of water as a solvent was shown to improve yield . Ascophyllum nodosum has shown potential to be used as an alternative ingredient in cracker production, producing a nutrient rich cracker with increased fibre content and potential bioactive effects. Crackers incorporating 5% Ascophyllum nodosum medium grade were found to be acceptable via sensory evaluation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:591091 |
| Date | January 2013 |
| Creators | Normansell, Helen Louise |
| Publisher | Manchester Metropolitan University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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