Introduction
Oleoresins are phytocomplexes extracted from plant sources, herbs and
oilseeds as oil-rich viscous materials. These resinous extracts include
terpenoids, fatty acids, phospholipids, essential oils, proteins, and
phenolic compounds (Napoli et al., 2019). Oleoresins offer great
potential for value-added food applications (e.g., beverages, sauces and
meat products, baked products, and confectionaries) related to their
chemical stability, uniformity, complex composition of biopolymers,
lipids, polar lipids, and health beneficial phytochemicals. Oleoresins
carry surface active molecules, such as phospholipids and proteins. The
interactions between these proteins, triacylglycerols and phospholipids
are responsible for the integrity and stability of their dispersions and
emulsions.
The extraction method plays an important role in the stability,
composition, yield and structural characteristics of oleoresins.
Conventional solvent extraction involves the use of organic solvents,
such as ethanol, hexane or ethyl acetate, to simultaneously obtain
volatile and non-volatile phytochemicals with functional properties
(Khasanah et al., 2017). Ultrasound- and microwave-assisted extraction
systems were used to increase the extraction yield (Ayub et al., 2023).
Wet milling strategies, such as ball milling, can be used to improve the
extraction efficiency by breaking solid enclosures where the oleoresins
are trapped. For example, ball milling was used to extract sesame paste
from seeds with improved viscosity and reduced particle size (Jin et
al., 2022). A similar strategy was used for the improving the functional
properties of the proteins, such as surface activity, solubility, and
hydrophobicity of proteins
extracted from hempseed (Julakanti et al., 2023).
In addition to the extraction method, the type of solvent determines the
extraction efficiency and physicochemical properties of the oleoresins.
The poly-ionic liquids (ILs) are molten organic salts below
100oC, which combine the characteristics of different
ionic chemicals, received considerable attention as substitutes of
volatile organic solvents due to their versatility, less toxicity,
remarkable solubilization for organic and inorganic compounds (Tolesa et
al., 2017). ILs offer great potential to enhance the extraction
efficiencies for complex material, such as oleoresins containing
biopolymers, surface active molecules and small phytochemicals and to
provide control over their composition. Among the four general groups
(imidazolium, phosphonium, pyridinium, and ammonium), imidazolium based
ILs were widely used for their low viscosity and stability in oxidative
and reductive conditions. In addition, they can also provide high
affinity for lipids and phenolic molecules as compared to conventional
organic solvents, such as ethyl acetate, methanol, and hexane. The
objectives of this study are to investigate the combined effects of wet
milling (i.e., ball milling) and novel ILs
(1-n-Hexyl-3-methylimidazolium chloride, 98% and
1-Ethyl-3-methylimidazolium chloride, 97%) on the on the extraction
efficiency of oleoresins from waxy sorghum rich in phenolics and
evaluate their yield, composition (protein, lipid, fatty acid, phenolic
contents) and structural properties of their dispersions (particle size,
zeta potential and FT-IR spectrum) in comparison to conventional solvent
extraction (i.e., ethanol and dichloromethane).