Browsing by Author "Bisht, Akshay"

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    Development of a novel functional yogurt containing anti-inflammatory bioactive compounds : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Albany, New Zealand
    (Massey University, 2019) Bisht, Akshay
    The consumption of bioactive compounds is increasingly becoming popular due to their beneficial effects on health and wellbeing. The anti-inflammatory properties of bioactives such as curcumin are well established. However, curcumin has low bioavailability, hence it is frequently consumed in capsules to enable the delivery of the required dosage to achieve optimum health benefits. Synergistic effects may be achieved by combining curcumin with other anti-inflammatory bioactive compounds. Recent investigations on lupeol and chlorogenic acid (CGA) have reported that these bioactive compounds show similar therapeutic benefits to curcumin. Furthermore, delivery of bioactives via a food matrix, such as fermented coconut yogurt, may improve bioavailability. Thus, this research investigated the potential of an anti-inflammatory combination of curcumin with CGA or lupeol with the objective of developing coconut yogurt to deliver the combined bioactives to humans. This research was performed in two parts. In part 1, the anti-inflammatory potential of three bioactive compounds (curcumin, CGA and lupeol), individually and in combination, was investigated using an in vitro model of human THP-1 macrophages stimulated with LPS. Differentiated THP-1 cells were treated with variable concentrations of curcumin, CGA and lupeol and their effects on the production of TNF-α, a pro-inflammatory cytokine, and cell viability was measured using ELISA and MTT assays, respectively. Curcumin alone significantly (p≤0.05) suppressed TNF-α production in a dose dependent manner. Curcumin in combination with lupeol gave an additional 15-35 % reduction in TNF-α level. However, the reduction in TNF-α production by curcumin + lupeol was accompanied by cell death. In contrast, treatment with CGA appeared to protect the THP-1 cells from LPS toxicity and its co-administration with curcumin at a 1:1 ratio reduced TNF-α production without impacting cell viability. Further, it is proposed that the latter combination showed anti-inflammatory activity by reducing mRNA expression of pro-inflammatory cytokines and COX-2 enzyme via suppressing NF-κB, IκB-β-kinase and TLR-4 receptor. Thus, a 1:1 combination of curcumin with CGA was selected to be delivered in coconut yogurt. In part 2, coconut yogurt enriched with turmeric and coffee to deliver the benefits of curcumin and CGA, respectively, was developed. Addition of 100 mg of each bioactive compound to 150 g coconut cream did not have any significant (p≤0.05) effect on the viable cell counts of the yogurt culture, pH and titratable acidity during fermentation. However, slight changes in pH, titratable acidity, viable cell counts and colour were noted during refrigerated storage of the yogurt for 15 days; no changes in syneresis was observed in the control and bioactive added samples. By the end of the storage period, 63.31±3.20 % and 84.81±3.17 % of curcumin and CGA, respectively, were retained in the yogurt samples. The yogurt samples with added bioactive compounds were well accepted by consumer sensory evaluation panellists. Thus, from the obtained data it can be concluded that coconut yogurt may be a potential delivery medium for health promoting curcumin and CGA to consumers.
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    The tale of the shear-thickening mamaku polysaccharide, from forest to gut : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Food Technology), Massey University, Palmerston North, New Zealand. EMBARGOED to 26 April 2025.
    (Massey University, 2023) Bisht, Akshay
    The New Zealand black tree fern (Cyathea medullaris, ‘mamaku’ in the Māori language) is grown across the Pacific Islands and has a long history of use for therapeutic benefits or as food by Māori people. The water-soluble gum extract from mamaku fern contains a novel glucuronomannan biomacromolecule, called mamaku polysaccharide (MP), which has been shown to exhibit a unique shear-thickening (i.e., increase in viscosity on shearing) behaviour at a similar shear rate as that found in the human stomach. Herein, the objective was to gain a better technical and physiological understanding of MP for designing a novel shear-thickening ingredient for the industry with proven effects in humans. The shear-thickening behaviour of MP was sensitive to the harvesting age of mamaku fronds and industrial operations such as high temperature and shear. With the increase in harvesting age, the molecular weight of MP reduced, which consequently reduced the shear viscosity. The shear-thickening behaviour was lost in MP from old fronds. Furthermore, the temperature treatment disintegrated the backbone of MP into smaller fragments which caused a reduction in viscosity and extent of shear-thickening. Similar rheological trends were observed post-shear treatment, however, there was no evidence of depolymerisation. A combination of in vitro models revealed that mamaku gum extract could improve host gut functioning by reducing the activity of digestive enzymes (α-amylase, pepsin and lipase) and binding bile acids. Mamaku gum can act as a substrate for colonic fermentation, promote the production of short-chain fatty acids and alter the colonic microbial composition. Upon ingesting mamaku gum, the shear-thickening behaviour may develop in the oesophagus causing a possible choking hazard. Therefore, the potential of using the whole pith—natural entrapment of MP in the tissue of pith—as an alternative to gum extract was studied. Freeze-dried pith was ground to powder. The powder particles swelled upon rehydration with water and released the water-soluble MP into the continuous phase in a time-dependent manner. The presence of enough MP in the continuous phase to form polymer-polymer interactions resulted in a shear-thickening behaviour of the pith powder suspension similar to the MP extract solution. Moreover, the co-consumption of 1 h pre-hydrated mamaku pith powder with a carbohydrate-rich meal significantly reduced the postprandial glycaemic response (blood glucose peak height) in human participants. Additionally, the consumption of mamaku pith powder in rats could alter colonic microbiota. Interestingly, more than half of the MP (uronic acid) consumed by rats survived the gut transition and was obtained in faeces, suggesting that MP could potentially be used as a laxative. Thus, mamaku pith could be used as an alternative to gum extract to develop a natural shear-thickening ingredient which may potentially help to manage diabetes and improve colon health.