Flavonol profile of cactus fruits (Opuntia ficus-indica) enriched cereal-based extrudates: Authenticity and impact of extrusion
2015
Moussa-Ayoub, Tamer E. | Youssef, Khaled | El-Samahy, Salah K. | Kroh, Lothar W. | Rohn, Sascha
In previous studies, it was hypothesized that isorhamnetin glycosides are the dominant flavonol derivatives occurring in the peels and cladodes of cactus Opuntia ficus-indica fruits and might be used as markers for analyzing the authenticity of food products containing (whole) cactus fruits or cladodes. In the present work, use of the whole yellow-orange fruit from cactus O. ficus-indica as an ingredient of rice- and corn-based snacks was evaluated. The impact of extrusion cooking on the flavonol profile was characterized in rice- and corn-based extruded products fortified with a freeze-dried preparation from the whole cactus fruit. HPLC analysis showed that the flavonol profile of cactus O. ficus-indica consisted of five prominent isorhamnetin glycosides with a concentration of 148.9μg/100mg dw. In contrast, the rice or corn grits used in the present study did not contain any flavonol at all. The freeze-dried fruit was added in different ratios (0, 2, 6, and 10%) to the rice or corn grits prior to the extrusion process. Analysis of the final extrusion products showed that flavonol profiles from the fortified rice or corn products, even at the lowest level of addition (2%), were similar to the original profile of the fruit before processing. Furthermore, the total flavonol content in extruded products was not significantly affected by extrusion cooking. This study showed that the unique flavonol profile of fruits from cactus O. ficus-indica might serve as a biochemical marker for the evaluation of the authenticity of products made from whole cactus fruit or the fruit's peel.
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