The aim of this study was to optimize the extraction of oleuropein from olive leaves through a systematic study of the effects of different parameters of ultrasound- assisted extraction (USAE) on the oleuropein yield, in comparison with conventional maceration extraction. A range of operational parameters were investigated for both conventional maceration extraction and USAE: solvent type, olive leaf mass- to-solvent volume ratio, and extraction time and temperature. Oleuropein yield was determined using high- performance liquid chromatography, with total phenolics content also determined. The optimized conditions (water–ethanol, 30:70 [v/v]; leaf-to- solvent ratio, 1:5 [w/v]; 2 hr; 25°C) provided ~30% greater oleuropein extraction yield compared to conventional maceration extraction. The total phenolics content obtained using the optimized USAE conditions was greater than reported in other studies. USAE is shown to be an efficient alternative to conventional maceration extraction techniques, as not only can it offer increased oleuropein extraction yield, but it also shows a number of particular advantages, such as the possibility of lower volumes of solvent and lower extraction times, with the extraction carried out at lower temperatures.
COBISS.SI-ID: 4893560
Olive cake and olive leaves are by-products (plant waste) of cultivation and processing of olives which, when disposed off unprocessed in high quantities on small areas, can have adverse effects on the environment. These by-products of olive oil production do not have considerable nutritional value, but can be nonetheless a valuable source of nutrients and energy for the animals. Additionally they contain secondary plant metabolites – polyphenols, which have beneficial effects on the health of animals and on the quality of their products. Olive cake and leaves also contain antinutritive substances (lignin, tannins, copper, polyphenols in higher concentrations), therefore they can be supplemented to the animal feeds in limited quantities. In Slovenia there is no systematic research regarding nutritional value and the use of olive by-products in animal nutrition. Chemical composition and nutrients content of olive by-products, especially of olive cake, is highly variable due to different environmental factors and processing technologies, which represent considerable obstacle in the use of olive by-products in the animal feeds. In the paper, the results of the target research programme (CRP) entitled »Utilization of olive growing by-products« comprising of the two year systematic sampling and analysis of chemical and nutrient composition of olive cake and the preliminary results of feeding trial on broiler chickens, supplemented with 5 % or 10 % of olive leaves or olive cake, will be presented.
COBISS.SI-ID: 4152968