Graz University of Technology Austria Institute of Biochemistry ...

Chemistry of Functional Foods
Group leader: Michael Murkovic
PhD students: Alam Zeb, Yuliana Reni Swasti
Diploma students: Elham Fanaee Danesch, Tatjana Golubkova, Zivile Rocyte
Technician: Alma Ljubijankic
Honorary Professor: Klaus Günther, Forschungszentrum Jülich, Germany
Visiting Professors: Evangelos Katzojannos, TEJ of Athens, Greece; Zhong Hayan, Central
South University of Forestry and Technology, China
General description
Antioxidants have different functions depending on the location of action. Is it the protection
of biological systems maintaining the integrity of the system or the protection of foods against
oxidation leading to health threatening substances The exposure to oxidation products is
either described as oxidative stress or the oxidized substances have an acute or chronic
toxicity or are carcinogenic. The production of healthier and safer foods is of primary interest
of this research group.
The antioxidants of interest are polyphenols including anthocyanins and carotenoids. The
evaluation of their occurrence in food and their behavior during processing and cooking is
important especially when these substances are used as food additives. The safety evaluation
of these compounds includes the evaluation of possible degradation products.
Heating of food is a process that is normally done to improve the safety and digestibility and
improve the sensory attributes like texture, color, and aroma. During the heating reactions
occur that lead to the degradation of nutritive constituents like carbohydrates, proteins, amino
acids and lipids. Some of the reaction products are contributing to the nice aroma, color, and
texture of the prepared food and many of them are highly toxic and/or carcinogenic. However,
these hazardous compounds occur in rather low concentrations being normally not acute
toxic. The substances have a very diverse chemical background like heterocyclic amines,
polycondensated aromatic compounds, acrylamide or furan derivatives. The aim of the
research is to investigate the reaction mechanisms that lead to the formation of these
hazardous compounds and establish strategies to mitigate the formation and thereby reducing
the alimentary exposure.
Carotenoids thermal oxidation in triacylglycerols
β-Carotene is one of most important and widespread carotenoids present in food. It is an
important source of provitamin A. It acts as antioxidant in biological systems including the
complex system of lipids. We studied the oxidation of β-carotene in model triacylglycerol
systems, comparable to most of the high oleic edible oil. An HPLC electrospray ionization
mass spectrometric method was developed for the separation and identification of
triacylglycerols and its oxidation products (Figure 1). β-Carotene was found to act as
antioxidant at lower temperature like 90°C and 100°C, while oxidation of triacylglycerols was
closely correlated with the oxidation of β-carotene after 8 hours of thermal oxidation at 110
°C. The oxidized products of β-carotene were epoxides, peroxides and apocarotenals,
separated and analyzed using C30 reversed phase HPLC-DAD and APCI-MS. We found that
110 °C and 120 °C were the favorable temperatures for studying the oxidation reaction of
carotenoids, while 110 °C, 120 °C and 130 °C were favorable for triacylglycerol oxidation.
33