Bioactivity of food-grade curcuminoids and their incorporation into coconut yogurt : a thesis submitted in partial fulfilment of the requirements for the degree of Masters of Food Technology, Massey University, Albany, New Zealand
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Date
2018
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Massey University
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Abstract
Curcuminoids are the bioactive components of turmeric, which comprises pf of 77% curcumin,
17% demethoxycurcumin (DMC) and 3% bisdemethoxycurcumin (BDMC). The application of
curcuminoids is limited by its low oral bioavailability due to poor aqueous solubility, low
absorption from the gut, rapid metabolism and rapid systemic elimination, which can be improved
by incorporating curcuminoids into a suitable food matrix. Thus, the present study aimed at
developing a coconut yogurt as a potential vehicle for the delivery of bioactive curcuminoids.
This research project was carried out in three phases. Phase I involved the screening of 10 different
commercial food-grade curcuminoid products in three types of yogurt. Each of the 10 food-grade
curcuminoid products, were added (0.4% w/w) to three types of commercial yogurt: cow’s milk
yogurt, coconut cream yogurt and a goat’s milk yogurt and subjected to pH measurement and
sensory evaluation with a view to selecting the most promising curcuminoid and delivery medium.
Results showed that coconut yogurt with added curcuminoids (C7 and C9) were the most
acceptable to the sensory panellists.
In phase 2, the two selected curcuminoid products (C7 and C9) were subjected to a cell-based, in
vitro analysis to measure their anti-inflammatory activity and cytotoxicity using THP-1
macrophages stimulated with lipopolysaccharide (LPS). The anti-inflammatory activity of the two
curcuminoid products was compared to analytical grade curcumin (Pure C) as positive control and
a dimethyl sulfoxide (DMSO) vehicle control. C7 and C9, as well as pure curcumin presented a
varied degree of toxicity towards LPS stimulated macrophages, as measured by the MTT (3-(4,5-
Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) colorimetric assay. All curcuminoid
samples were found to be non-toxic to THP-1 cells at 10 µM. At this concentration, the test
products and the control down-regulated the expression of TNF-α by 2.5-fold in the differentiated
THP-1 cells stimulated with LPS. Concentrations of DMSO as high as 0.5% were well tolerated
by the macrophages. As there were no significant differences (p>0.05) in the anti-inflammatory
activity of the food-grade curcuminoid samples, the both the test products in coconut cream yogurt
were tested in phase III.
Samples of coconut cream were fortified with food-grade curcuminoids (C7 and C9) at 400
mg/150g, prior to yogurt fermentation; a negative control without curcumin was also included.
The physico-chemical, microbiological and sensory properties of the fermented coconut cream
yogurts were compared to the control coconut yogurt. Results showed curcuminoids did not have
any effect on fermentation of coconut cream. During storage (4°C) for 15 days, acidity, yogurt
microflora and syneresis of the curcuminoid enriched yogurts were not significantly different from
the control yogurts. However, addition of curcuminoids resulted in formation of a weaker gel
compared to the control yogurt, and the viscosity of the gels varied during storage. The
concentrations of curcuminoids in the coconut cream yogurt during storage of the fermented
products were measured by reversed phase HPLC. HPLC analysis showed that 70-75% of the
bioactives were retained in the yogurt at the end of the 15-day storage period. The two fermented
coconut yogurts fortified with curcuminoids (C7 and C9) were well-accepted by a consumer
sensory panel (n=180). Based on the pH, acidity, sensory, texture, microbiological and HPLC
results, it can be inferred that coconut yogurt may serve as a suitable delivery medium for bioactive
curcuminoids.
Description
All Figures in the Literature Review have been removed for copyright reasons except for Figure 2.2, which is licensed under a Creative Commons Attribution 3.0 Unported License (CC BY 3.0).
Keywords
Bioactive compounds, Health aspects, Turmeric, Therapeutic use, Curcumin, Solubility, Yogurt