Process development for functional food ingredients with gut health benefits from the brown seaweed Ecklonia radiata

Author: Suvimol Charoensiddhi

Charoensiddhi, Suvimol, 2017 Process development for functional food ingredients with gut health benefits from the brown seaweed Ecklonia radiata, Flinders University, School of Medicine

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Abstract

South Australia has among the world’s highest diversity of seaweeds, with up to 1,500 described species, of which approximately 62% are endemic to the region. There is a growing recognition that seaweeds are important sources of bioactive compounds with a variety of biological activities. The aim of this study was to develop efficient seaweed processing technology and assess the potential of using South Australian brown seaweed as higher-value functional foods and nutraceuticals. Enzyme- and microwave-assisted processing techniques were developed to assist with the extraction of bioactive compounds from seaweed, as conventional techniques are impeded by the high degree of structural complexity in seaweed cell walls. In this study, Ecklonia radiata was selected as the experimental species due to its abundance in the region and possessing chemical constituents of commercial interest. Using microwave-assisted enzymatic extraction, phlorotannin content and total antioxidant activity of the extracts were increased by approximately 23% and 30%, respectively, compared with the conventional acidic extraction. These phenolic compounds are of interest as their functional properties have been widely demonstrated. Polysaccharides (alginate, fucoidan, and laminarin) represent the major functional components in this brown seaweed, which may provide health benefits to humans though a prebiotic effect. The critical processing parameters (enzyme, pH, and buffer) for the oligo- and polysaccharide production were investigated. Enzyme type and pH had minor impacts on the total sugar yield, but each affected the sugar composition and MW profile of the carbohydrate extracts differently. Acidic extraction yielded lower MW components compared to neutral and alkali extraction, while the inclusion of hydrolytic enzymes further reduced the MW of the extracted polysaccharides by 20–50%, compared with extraction using pH-adjusted water-only. High concentrations of buffer salts were found to inhibit polysaccharide extraction. The prebiotic effects of the seaweed extracts were enhanced when the enzyme-assisted extraction was used. When added to an in vitro anaerobic fermentation system containing human faecal inocula, the extracts underwent fermentation and stimulated the production of SCFA. Furthermore, the extracts demonstrated the capacity to promote the growth of beneficial microbes. The key potential fermentable components were further fractionated in order to investigate their specific prebiotic potential. The high MW polysaccharide-enriched fraction showed greater potential for improving gut health as this fraction was not digestible by enzymes present in the small intestine, and induced significantly higher butyric acid production compared with the positive control, inulin. During in vivo studies, rats were fed with a polysaccharide-supplemented diet, raw seaweed-supplemented diet, and basal feed control diet. Significant improvements in cecum digesta weight, total SCFA, and the abundance of the key butyrate producer F. prausnitzii, and a decrease in potentially toxic phenol and p-cresol were observed for rats fed with the polysaccharide-supplemented diet. Industrial process modelling and economic feasibility analyses were performed to assess the commercial feasibility and profitability of four production processes. The results showed that the fractionation of seaweed crude extract and the production of value-added product improved the overall economic performance of crude extract production alone. The key findings achieved from this work contribute to develop and expand new platform of seaweed utilisation for higher-value products, particularly to functional food and nutraceutical industries in order to serve the social demand for health awareness and support economic development.

Keywords: Enzymatic process, Functional food, Macroalgae, Phlorotannin, Polysaccharide, Prebiotic activity
Subject: Medicine thesis

Thesis type: Doctor of Philosophy
Completed: 2017
School: School of Medicine
Supervisor: Prof Wei Zhang