Optimization of ultrasound-assisted extraction (UAE) of phenolic
compounds from olive cake
Revised: 18 July 2017 / Accepted: 18 December 2017 / Published online: 3 February 2018
Ó Association of Food Scientists & Technologists (India) 2018
Abstract The use of ultrasound in ultrasound-assisted
extraction (UAE) is one of the main applications of this
technology in food industry. This study aimed to optimize
UAE conditions for olive cake extract (OCE) through
response surface methodology (RSM). The optimal UAE
conditions were obtained with extraction temperature of
56 °C, extraction time of 3 min, duty cycle of 0.6 s, and
solid to solvent ratio of 3.6%. At the optimum conditions,
the total phenolic compounds (TPC) content and antioxi-
dant activity (AA) were measured 4.04 mg/g and 68.9%,
respectively. The linear term of temperature had the most
effect on TPC content and AA of OCE prepared by UAE.
Protocatechuic acid and cinnamic acid were characterized
as the highest (19.5%) and lowest (1.6%) phenolic com-
pound measured in OCE extracted by UAE. This research
revealed that UAE is an effective method to extract phe-
nolic compounds from olive cake. RSM successfully
optimized UAE conditions for OCE.
Keywords Olive cake Á Ultrasound-assisted extraction Á
Phenolic compounds Á Optimization Á Response surface
Nowadays, the awareness of food consumers about the
importance of natural bioactive compounds with
nutraceutical activity is increasing day by day. Hence, the
food industry is seeking these compounds from processed
agricultural products and their by-products (Yolmeh and
Mahoonak 2016). In addition to economic efﬁciency, the
using by-products of food industry have environmental
importance through decreasing environmental hazards
(Wijngaard et al. 2012).
Olive (Olea europaea L.) and processed olive products
are containing many bioactive compounds such as phenolic
compounds. This fruit is one of the oldest oil sources,
which have been used in all over the world (Azizpour et al.
2017). Black olive mill wastewater, solid waste, and olive
cake are by-products of olive oil industry. Since these by-
products constitute major part of olive oil industry (35 kg
olive cake and 440 l wastewater per 100 kg of olive)
control them is important (Alu’datt et al. 2010).
Olive cake is recognized an inexpensive biomass for
phenolic compounds, which is widely available in
Mediterranean countries and the northern provinces of Iran.
However, these by-products of olive oil industry represent
environmental problems (Lesage-Meessen et al. 2001).
Thus, many researchers have aimed to decrease these
environmental problems and on other hand increase eco-
nomic value. So far, olive cake has been used as animal
feed, fuel, and fertilizer (Keskin and Kaya 2010).
Several potentially bioactivity such as antioxidant, anti-
viral, anti-cancer, anti-inﬂammatory, hypoglycaemic and
hypolipidaemic have been reported for phenolic com-
pounds of olive. Olive mill waste is containing consider-
able amount (98%) of the total phenolic compounds (TPC)
content of whole olive (Tripoli et al. 2005; Alu’datt et al.
The traditional extraction methods are very time-con-
suming and need large amount of solvents for bioactive
compounds. Currently, several modern extraction methods
have been developed for extraction of phenolic
& Zohreh Mojerlou
Department of Food Science and Technology, Azad Islamic
University of Sabzevar, Sabzevar, Iran
J Food Sci Technol (March 2018) 55(3):977–984