262
Some molecules can be hidden deeper in the plant and may require finer grinding
for allowing a good extraction. This depends on the histolocalization of the targeted
metabolites. A good knowledge of the selected plants is therefore particularly
important for controlling the extraction of the compounds of interest (Komaty et al.
2016). In plant, phenolic compounds are present in the tissue in cellular and subcellular levels with differences between insoluble and soluble phenolics (Naczk and
Shahidi 2004). Usually, when indicating, the raw material is pulverized between 0.2
and 1 mm (Bakirtzi et al. 2016; Mouratoglou et al. 2016; Georgantzi et al. 2017;
Jancheva et al. 2017; Karageorgou et al. 2017; Molnar et al. 2018; Chanioti and Tzia
2018; Ozturk et al. 2018; Obluchinskaya et al. 2019). Sieves ranging from 20 to 80
mesh (841 μm to 177 μm) are used to standardize the sample size (Li et al. 2015,
2016; Wei et al. 2015a, b; Qi et al. 2015; Cui et al. 2015, 2018; Peng et al. 2016,
2018; Zhuang et al. 2017; Wang et al. 2017, 2018a, b, 2019; Ma et al. 2018; Sang
et al. 2018; Cao et al. 2018a, b; Vieira et al. 2018; Shang et al. 2018; Duan et al.
2019; Saha et al. 2019; Mansur et al. 2019; Xu et al. 2019).
Storing samples before extraction is also an important step (Naczk and Shahidi
2004). The sample can be stored in the dark, at room temperature or keeping cold.
Mouratoglou et al. specify that samples of lemon peel, once dried and pulverized,
are stored “in the dark, at ambient temperature, for no longer than 7 days” to preserve the compounds (Mouratoglou et al. 2016).
Key Parameters for Extraction
A great number of variables may affect the extraction efficiency (Chanioti and Tzia
2018; Duan et al. 2019; Choi and Verpoorte 2019) and could be leveraged for
increasing the extractive performance and optimizing the processes. The plant-tosolvent ratio, the temperature, the duration of extraction, the nature of deep eutectic
solvent through variation of HBD and/or HBA, and the water content in the deep
eutectic solvents are the main factors which may influence the extraction efficacy
(see Table 7.3) (Cvjetko Bubalo et al. 2018). All play a critical role, with possible
interactions between each other. These parameters could also strongly depend on
the technologies employed, and of course technologies have a true impact on the
performance (Table 7.3). Many research works use multivariate approaches to consider the interactions between these variables (Bi et al. 2013; Bosiljkov et al. 2017;
Ivanović et al. 2018; Panić et al. 2019b). Ivanović et al., for example, studied the
interactions of three extraction parameters including the duration of microwave irradiation, the quantity of water in the deep eutectic solvent, and the temperature. They
showed the influence of these interactions on the polyphenol extraction rate
(Ivanović et al. 2018). The amount of water and the temperature were found to have
a major effect, while the microwave irradiation time had a minor influence.
L. Percevault et al.
Some molecules can be hidden deeper in the plant and may require finer grinding
for allowing a good extraction. This depends on the histolocalization of the targeted
metabolites. A good knowledge of the selected plants is therefore particularly
important for controlling the extraction of the compounds of interest (Komaty et al.
2016). In plant, phenolic compounds are present in the tissue in cellular and subcellular levels with differences between insoluble and soluble phenolics (Naczk and
Shahidi 2004). Usually, when indicating, the raw material is pulverized between 0.2
and 1 mm (Bakirtzi et al. 2016; Mouratoglou et al. 2016; Georgantzi et al. 2017;
Jancheva et al. 2017; Karageorgou et al. 2017; Molnar et al. 2018; Chanioti and Tzia
2018; Ozturk et al. 2018; Obluchinskaya et al. 2019). Sieves ranging from 20 to 80
mesh (841 μm to 177 μm) are used to standardize the sample size (Li et al. 2015,
2016; Wei et al. 2015a, b; Qi et al. 2015; Cui et al. 2015, 2018; Peng et al. 2016,
2018; Zhuang et al. 2017; Wang et al. 2017, 2018a, b, 2019; Ma et al. 2018; Sang
et al. 2018; Cao et al. 2018a, b; Vieira et al. 2018; Shang et al. 2018; Duan et al.
2019; Saha et al. 2019; Mansur et al. 2019; Xu et al. 2019).
Storing samples before extraction is also an important step (Naczk and Shahidi
2004). The sample can be stored in the dark, at room temperature or keeping cold.
Mouratoglou et al. specify that samples of lemon peel, once dried and pulverized,
are stored “in the dark, at ambient temperature, for no longer than 7 days” to preserve the compounds (Mouratoglou et al. 2016).
Key Parameters for Extraction
A great number of variables may affect the extraction efficiency (Chanioti and Tzia
2018; Duan et al. 2019; Choi and Verpoorte 2019) and could be leveraged for
increasing the extractive performance and optimizing the processes. The plant-tosolvent ratio, the temperature, the duration of extraction, the nature of deep eutectic
solvent through variation of HBD and/or HBA, and the water content in the deep
eutectic solvents are the main factors which may influence the extraction efficacy
(see Table 7.3) (Cvjetko Bubalo et al. 2018). All play a critical role, with possible
interactions between each other. These parameters could also strongly depend on
the technologies employed, and of course technologies have a true impact on the
performance (Table 7.3). Many research works use multivariate approaches to consider the interactions between these variables (Bi et al. 2013; Bosiljkov et al. 2017;
Ivanović et al. 2018; Panić et al. 2019b). Ivanović et al., for example, studied the
interactions of three extraction parameters including the duration of microwave irradiation, the quantity of water in the deep eutectic solvent, and the temperature. They
showed the influence of these interactions on the polyphenol extraction rate
(Ivanović et al. 2018). The amount of water and the temperature were found to have
a major effect, while the microwave irradiation time had a minor influence.
L. Percevault et al.