Oleuropein as a bioactive constituent of functional milk and yogurt
In recent years, interest in antioxidants isolated from plants has arisen due to their vital role in the protection of cell damage caused by the excess of free radicals (oxidative stress) . Moreover, antioxidants are also used by food industries, as additives for the improvement of several properties of foods (biofunctional foods). One of the most important and developing category in this area is the dairy products, which are natural sources of high nutritional value . Oleuropein is an important constituent of olive fruits. According to in vivo and in vitro studies, oleuropein exhibits anti-ischemic, antioxidative, and hypolipidemic effects . In the present study, two functional dairy products were prepared by addition of oleuropein. An analytical method for the measurement of oleuropein in milk and yogurt was developed and validated. The new products were examined about the stability of oleuropein during their treatment. The results showed that oleuropein was resistant during heating of milk at 90oC for 5min. Furthermore, during coagulation of milk, oleuropein was not hydrolysed by the produced acids, it was not metabolized by lactic acid bacteria and it did not stop their growth. Also its stability during the maintenance of milk and yogurt for 35 days at 4 oC was proven. The functional milk and yogurt production was performed in laboratory and semi-industrial scale. Oleuropein was completely soluble in the selected concentration (0.1mg/ml) and it did not give any peculiar taste, as the products had the same taste and flavor with the conventional ones . The selection of the concentration was based on the oleuropein quantity corresponding to consumption of 15 olive drupes per day. All the above results show that oleuropein can be added as active ingredient in milk and yogurt and two new biofunctional products can be produced, whose properties remain constant, during the overall process.
Acknowledgement: The project was funded by the General Secreteriat for Research and Technology of Greece (Program 03ΔΣBEΠPO –83)
References: 1. Visioli, F., Galli, C. (2002). Critical Reviews in Food Science and Nutrition 42: 209–221.
2. Tamine, A.Y., Robinson, R.K. (1999). Woodhead Publishing in Food Science and Technology, 2nd edition.
3. Andreadou, I. et al. (2006). J Nutr. 136: 2213–2219