Methode ontwikkeling van zure suikers m.b.v. HPLC-PAD : Het bepalen van de M/G-ratio in alginaat geëxtraheerd uit macroalgen
Özdemir, B. (2018). Methode ontwikkeling van zure suikers m.b.v. HPLC-PAD : Het bepalen van de M/G-ratio in alginaat geëxtraheerd uit macroalgen
. NIOZ Royal Institute for Sea Research: Yerseke. 50 pp.
In the year of 2050 there will be 10 billion people walking on planet earth. Food should be available for these people. An important food source where not much attention is paid for, is the biomass production from macroalgae. Because of the lack of attention for this kind of food source, it is important to determine the taste, aroma, colour, and texture of the macroalgae. The texture of macroalgae is an important property for consumers but also for producers. The texture of macroalgae is determined by alginate. Alginate is a polysaccharide that occurs in brown algae and consists of the two acidic sugars β-D-mannuronic acid (ManA) and α-L-guluronic acid (GulA). The application of alginate is determined by the ratio of GulA and ManA which is defined as the M/G ratio. With High Performance Liquid Chromatography (HPLC) combined with an Anion-Exchange column and Pulsed Ampereometric Detection (PAD) the M/G ratio can be determined without any need for dervatization. The acidic sugars have a relative high affinity for the column. Because of this a pusher eluent is needed to elute the compounds of the column. In this research a method is developed and optimized with standards. The M/G ratio for five different species of brown algae is determined: Fucus serratus, Fucus vesiculosus, Ascophyllum nodosum, Undaria sp., Sargassum muticum. The alginate is extracted from the different species and is hydrolysed with TFA. The acidic sugars degrade at different hydrolysis times and TFA concentrations. Because of this the two sugars are hydrolysed at different hydrolysis times and TFA concentrations. This is done for GulA for 6 hours and 2 M TFA and for ManA for 18 hours and 1 M TFA. A method is developed for the analysis of the acidic sugars. The method uses 170 mM NaOAc as pusher eluent and 10 mM NaOH at a flow rate of 0.3 mL/min. The method had a good linearity up to 90 µM and the LOD and LOQ are determined. The hydrolysis time and TFA concentration for each alginate is different because GulA is relatively easily hydrolysed than ManA. Due to problems with the HPLC-PAD an internal standard galacturonic acid (GalA) is used. The M/G ratios are determined of the different species and compared with reference values. Undaria sp. has a higher flexibility because the ratio is relative higher. Low ratios give more firmer macroalgae. This is due to the fact that GulA determines the structure of the alginate. The seasonal changes and location of sampling the macroalgae can have an effect on the M/G ratio.
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