The effects of model foods rich in bioactive compounds on brain-gut regulation and neurodegeneration : A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Lincoln University

• Main Author: Hossain, A K M Mofasser
• Format: Dissertation
• Language: English

Content Partner: Lincoln University. A compelling interaction between the diet, gut and host physiology has emerged. Biologically active compounds particularly dietary fibre (DF) and polyphenols in a diet have long been appreciated due to their inverse relation with rising chronic diseases, particularly metabolic disorder, obesity, type 2 diabetes and cancers. Research has illustrated a complex interaction of multiple peptides (gut endocrine systems) and nutritional inputs physiologically affect appetite control and host immunity. Despite the potential health benefits of consuming a diet rich in bioactive compounds, little is known about the bio-functional interactions such as digestibility, effects of digested and fermented metabolites on the attenuation of gut endocrine system and immunity of the host. This study developed a cookie from wholemeal cereals which incorporated different proportions (0, 5, 10 and 15 %) of blackcurrant or astaxanthin-rich microalgae Haematococcus pluvialis powder as a replacement of wheat, barley and oat flours. The study evaluated the effects of blackcurrant/astaxanthin on cookie textural properties. The in-vitro carbohydrate digestibility of the cookies demonstrated the glycaemic control. Inclusion of blackcurrant/astaxanthin powder in wholemeal cereals cookies significantly (p < 0.05) decreased the rate of glucose release, when compared with wholemeal cereals cookie control. The 15 % blackcurrant and astaxanthin powder incorporated cookies had a significantly (p < 0.05) higher fibre fraction, compared to the control flour cookies. Blackcurrant powder contains about 25 % and astaxanthin-rich H. pluvialis powder contains more than 30 % DF. Using an in-vitro fermentation model, the prominent gut bacterial growth and fermentative properties of the indigestible cookie fraction were evaluated. The combination of four bacterial species Lactobacillus and Bifidobacterium was utilised using the isolated fibre fractions from different cookies as substrates. These fibre fractions significantly increased the microbial growth and their metabolite (short-chain fatty acids, SCFAs) production. The blackcurrant/astaxanthin incorporated substrates significantly increased the bacterial populations, lowered fermentation pH and increased optical density (OD600) at 6, 12, 24 and 48 h incubation when compared with negative (medium only) and positive control (wholemeal cereals cookies). The increased concentrations of SCFAs production from the in-v