Conclusion
The present work is considered as the first report concerning
the addition of oleuropein in milk and yogurt to produce novel
foodstuff preparations. For this purpose, two efficient methods
have been developed and validated for the reliable determination
of oleuropein in milk and yogurt preparations. The results herein
indicated that oleuropein is resistant during heating of milk. During
coagulation of milk, oleuropein was not hydrolysed by the produced
acids, it was not metabolised by lactic acid bacteria and did
not inhibit their growth. Oleuropein was completely soluble in the
selected concentrations (0.1 mg/ml or 0.2 mg/ml) without adding
any peculiar taste or flavour, while its stability during the milk
and yogurt storage at 4 C was unequivocally proven. Since from
the technological point of view, the presence of oleuropein does
not interfere with milk and yogurt manufacturing process and considering
the significant biological value of oleuropein, proved
repetitively by numerous research reports, it is concluded that this
molecule can be added as an active ingredient in milk and yogurt
preparations for the production of novel functional foods with significant
health benefits. This finding also implies that olive extracts
enriched in oleuropein (e.g., from olive leaf or olive fruit) could also
be useful materials for development of similar dairy products and
this is currently under investigation.