1. Introduction
The
evergreen shrub Camellia
oleifera Abel., belonging to Camellia genus of Theaceae family,
is a unique woody edible oil species widely distributed in southern
China (Gao et al., 2020).Camelliaseed oil, known as the “oriental olive oil” (Cheng et al., 2018; Ma et
al., 2011), contains abundant unsaturated fatty acids, among which the
total amount of oleic acid and linoleic acid is over 85% (Wei et al.,
2015; Yang et al., 2016; Zhu et al., 2019). The edible value ofCamellia seed oil is high, for it also contains various
nutritional ingredients such as polyphenols, sterols and tocopherols (Wu
et al., 2018; Ye et al., 2014; Zhou et al., 2019). Meanwhile, its
bioactive properties, e.g., anti-inflammatory, anti-oxidant activity and
anti-obesity (Fattahi-far et al., 2006; Guan et al., 2011; Wang et al.,
2019), rendering Camellia seed oil a great application potential
in cosmetic and medicinal field (Chaikul et al., 2017). Recommended by
FAO as high quality edible oil (Zhou et al., 2019),Camelliaseed oil is now in great demand for people have higher requirements for
health, and thus the corresponding industry has a promising prospect in
the future.
Cold pressing and solvent extraction are the most commonly used
industrial methods in oil extraction process (Yang et al., 2019). Over
refinement could be avoided by cold pressing via cutting down the high
temperature pretreatment ofCamelliaseed, the decolorization and deodorization of crude oil (Moslavac et
al., 2014). Thus the quality of cold pressing oil is guaranteed by
reducing the loss of bioactive compound which is sensitive to heat and
also by reducing the formation of benzopyrene and glycidyl ester at high
temperature (Qi et al., 2015; Wei et al., 2015; Wu et al., 2012).
Organic solvent extraction method has obvious defects such as solvent
residue, and environmental pollution. This method is still in use
especially in the treatment of pressed seed cake for the economic reason
(Shao et al., 2015). In comparison, cold pressed oil showed stronger
antioxidant and antimicrobial activities than oil extracted by organic
solvent (Zhou et al., 2014). Supercritical CO2extraction (SCCE) has been widely applied as a green technology. It is
superior to traditional technology as it is non‐toxic, fast and high
efficient. Besides that, its critical temperature and critical pressure
(T c = 304.2 K, P c = 7.38
MPa) are moderate to reach (Duan et al., 2013). The oil quality
extracted by SCCE is superior both in higher bioactive constituents
content such as squalene and sterols, and also better physicochemical
characteristics like lighter color, stronger aroma, lower acid value
(AV) and peroxide value (POV) (Shao et al., 2015). The oil quality
differs obviously when extracted by different processes, and this
implies that developing a proper methodology to distinguish oil from
different sources appears to be meaningful.
In the PRC National Standard (GBT11765-2018), to classifyCamellia seed oil by quality, the physicochemical parameters and
the corresponding analytical procedures, are defined listed in Table 1.
Conventional analytical techniques such as HPCL and GC-MS have certain
drawbacks, e.g., expensive instruments, complex sample pretreatment and
consuming more time (Aparicio et al., 2013; Semenov et al., 2019). In
recent years, electronic tongue (e-tongue) technique, as an analytical
technique mimicking the human senses of taste, owing to its simple,
rapid and precise characters, has been widely explored in food, cosmetic
and pharmaceutical industries (Sliwinska et al., 2014). Many qualitative
and/or quantitative applications of e-tongue for olive oils have been
reported successfully. Quality parameters such as
peroxide,
anisidine values and total tocopherols (Semenov et al., 2019),
carotenoid (Semenov et al., 2019), oxidative stability and polyphenols
(Rodrigues et al., 2019) were correlated and assessed using e-tongue
system combined with chemometrics. Studies of classification of the
olive oil base on quality (Tahri et al., 2018; Veloso et al., 2018),
discrimination of adulterate olive oil (Harzalli et al., 2018; Oliveri
et al., 2009), olive oil shelf-life estimation (Buratti et al., 2018;
Rodrigues et al., 2017) and olive oil sensory assessment (Rodrigues et
al., 2019; Rodrigues et al., 2018) were also well achieved indicating
broad application of e-tongue in oil characterization. ForCamellia oil, chemometrics combined with electronic nose was
found effective to discriminate the geographical origins (Peng et al.,
2020). Methods of FTIR (Han et al., 2020) or NIR (Chu et al., 2017)
spectroscopy combined with chemometrics was developed to identifyCamellia oil adulteration with rapeseed oil or vegetable oil. To
the best of our knowledge, discrimination of Camellia seed oils
produced by different processes has not been reported.
The aim of the present work was to evaluate the versatility of e-tongue
for the characterization of Camellia seed oils (pressed,
extracted with organic solvent and scCO2) and simulation
of peroxide value (POV) and acid value (AV) associated with sensory
assessment. For this, chemometric quantitative approach (multiple linear
regression models) is applied to establish predictive multivariate
models.