Chemical characterization of chitin from New Zealand plants and their use as digestive aids : A dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science at Lincoln University

Abstract

Natural polysaccharide, Chitin is a biopolymer isolated from shells and exoskeletons of fungal, algal, insect, molluscs and crustacean sources, and the extraction method varies among different sources. Among all these sources, crustaceans produce millions of tonnes of this polysaccharide every year, and are discharged in the form of snow in the sea floor, causing harm to the marine ecosystem. Known for their biocompatible, biodegradable and non-toxic nature, chitin and its monomers finds significant role in different sectors of economy. Even though, extraction of chitin from marine sources increases their economic value, one important factor, which is limiting this process, is the inconsistency in raw material supply annually and variability in physicochemical characteristics, owing to difference of process conditions. To overcome these problems and to develop clean labeled chitin polymers, alternative sources could be considered which offers consistent production. This work hence focuses on extraction of chitin from leaves of New Zealand plant- Phormium tenax, using Agaricus bisporus mushroom as positive control. Leaves were considered, as seeds of the same plant gave comparable results to standard chitin extraction, when carried out previously at Lincoln University. Leaves of Phormium tenax are known for their known fibre content and exhibits properties and applications similar to chitin. The leaf fibres are used by Maori community mainly for wound healing, and textile applications and are an important part of New Zealand bio-diversity. The fibre Approximately 37 g/100g and 38 g/100g of Chitin are obtained respectively from Agaricus bisporus (positive control) and pure chitin (standard chemical) after extraction, as quantified by HPLC-FLP method. Overall, the recovery is comparatively low, hence disproving the hypothesis that this extraction method works successfully in extracting chitin from all sources. Also, the chitin recovered from Phormium tenax leaf is non-quantifiable comparing to mushrooms and pure chitin, hence indicating the chance of some complex interaction between chitin and other bioactive components present in leaves. The last part of the study was the development of a fermented functional beverage, kefir and study of its physico-chemical properties. 5 different formulations of kefir (4 with milk as base and 1 with carrot juice as base); with roasted and un-roasted white and brown button mushrooms (Agaricus bisporus) were considered to study if mushrooms had a stabilization effect on kefir. The results of viscosity and pH clearly indicate that roasted white mushrooms offers a stabilization effect on kefir, compared to unroasted and roasted brown mushrooms. However no significant results were obtained in TSS and syneresis studies.