PRE-ABSORPTIVE METABOLISM OF

DISSERTATION

Presented in Partial Fulfillment of the Requirements for

the Degree of Doctor of Philosophy in the Graduate

School of The Ohio State University

By

Sagar K. Thakkar

***** The Ohio State University 2009 Dissertation Committee: Approved by

Dr. Mark L. Failla, Adviser Dr. Earl H. Harrison Dr. Hugo Melgar-Quiñonez ______Dr. Ouliana Ziouzenkova Adviser The Ohio State University Nutrition Graduate Program

ABSTRACT

Vitamin A deficiency (VAD) is still a major public health issue in developing

countries. Biofortification of staple crops with pro-VA carotenoids is proposed as a complementary and sustainable approach to alleviate VAD. However, it is unknown if the additional pro-VA carotenoids accumulated in the staple crops will be bioavailable.

First, I focused on screening the relative bioaccessibility of β-carotene (BC) from ten cultivars of cassava using the coupled in vitro digestion/Caco-2 cell model. All-trans-BC,

9-cis-BC, and 13-cis-BC were the most abundant carotenoids in boiled cassava and recoveries after digestion exceeded 70%. Efficiency of micellarization of total BC was

30% for various cultivars with no significant difference among isomers and was linearly proportional to concentration in cooked cassava. Accumulation of all-trans-BC by Caco-

2 cells incubated with the diluted micelle fraction for 4 h was proportional to the quantity present in micelles. In addition to boiling, cassava is also traditionally prepared by fermentation and roasting. These different methods of preparation have the potential to affect both the retention and bioaccessibility of BC. So I next focused on the effects of traditional preparation of cassava on retention and bioaccessibility of BC in boiled cassava, gari (fermentation and roasting), and fufu (fermentation and boiling the paste).

Apparent retention of BC was approximately 90% for boiled cassava and fufu. In contrast, roasting fermented cassava at 195°C for 20 min to prepare gari decreased BC

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content by 90%. Retention was increased to 63% when temperature was decreased to

165°C and roasting was limited to 10 min. The efficiency of micellarization of all-trans

and cis isomers of BC during simulated digestion was 25-30% for boiled cassava and

gari and independent of cultivar. However, micellarization of BC isomers during

digestion of fufu was only 12-15%. These differences in retention and bioaccessibility of

BC from cassava products prepared according to traditional processing methods suggest

that gari and fufu may provide less retinol activity equivalence (RAE) than isocaloric

intake of boiled cassava.

It is noteworthy that cassava has only BC as the primary in the tuber.

However, maize, another staple crop targeted for biofortification also has β-cryptoxanthin

(B-CX) and lutein (LUT) and zeaxanthin (ZEA). Studies have demonstrated interaction

between carotenoids, therefore primary aim of my next study was to examine if LUT and

ZEA attenuate the bioaccessibility of pro-VA carotenoids at amounts and ratios present in

maize. BC incorporation into micelles during chemical preparation and during in vitro

digestion of carotenoid-enriched oil was slightly increased when the concentration of

LUT was 6-fold or greater than BC. Likewise, the efficiency of BC micellarization was

slightly increased during simulated small intestinal digestion of white maize porridge

supplemented with oil containing 9-fold molar excess of LUT to BC. Mean efficiencies

of micellarization of BC, BCX, LUT and ZEA were 16.7, 27.7, 30.3 and 27.9%,

respectively, and independent of the ratio of LUT plus ZEA to pro-VA carotenoids

during simulated digestion of maize porridge prepared from