Chinese red dates: Ultrasonic power and microwave extraction boosts functionality
Researchers from the Northwest A&F University in China wrote that polysaccharides from Chinese red dates (Z. jujube) boast immunity, antioxidant, antitumor, hepatoprotective, and hypoglycemic activities.
However, they found they can be most effectively extracted using microwave-assisted and ultrasonic-assisted methods, which better maintain the structure of polysaccharides compared to traditional hot water extraction.
“Recent phytochemical and pharmacological studies have shown that the polysaccharides, one of the major biologically active components of the jujuba fruit, have various biological effects, including immunity, antioxidant, antitumor, hepatoprotective, and hypoglycemic activities, and gastrointestinal-protective effects,” they wrote in the journal Food Chemistry.
Long used in Chinese herbal medicine, the basic method of extraction involves breaking the outer layer of the cell wall from the inner layer carefully to avoid damaging the polysaccharides’ structure.
“Extraction in hot or boiling water is the classical and most convenient method of laboratory extraction, and is widely used in industry,” the review noted.
“However, the disadvantages of hot water extraction include the long times and high temperatures required, low efficiency, and the possible degradation of polysaccharides.”
The most efficient extraction saw researchers use 120W of ultrasonic power, an extraction time of 15 minutes, and extraction temperature of 55°C that produced a final yield of 4.47%, said the review.
“When some of the extraction parameters were modified, including lowering the temperature, and ultrasonic power, yet increasing the ultrasonic treatment time, the yield of polysaccharides improved to 8.11%,” they added.
Meanwhile, the review identified an effective microwave-assisted extraction, which also increased the yield of the polysaccharides.
The optimal extraction conditions use microwave power of 400W, a microwave time of 60 minutes, and extraction temperature of 70°C, and water: material ratio of 30:1.
“Under these conditions, the yield of crude polysaccharides from Z. jujuba fruit harvested in Southern Khorasan Province in Eastern Iran was 9.02%,” the review noted.
“These assisted extraction methods have improved the extraction efficiency for Z. jujuba polysaccharides, shortened the processing time, and reduced the solvent consumption and the energy required.”
Clinical studies
But while the isolation, structural characterisation, and the bioactivities of polysaccharides from red dates have been extensively investigated in recent years, the review said to better determine the polysaccharides’ effects on human health, in vivo studies in animals and clinical studies must be conducted.
“There are still opportunities and challenges in polysaccharide research. The increasing number of modern studies of bioactive polysaccharides, especially Z. jujuba polysaccharides, in biomedicine suggests that these macromolecular compounds will have great medical significance in the future,” the researchers concluded.
Source: Food Chemistry
DOI:10.1016/j.foodchem.2017.01.074
“Isolation, structures and bioactivities of the polysaccharides from jujube fruit (Ziziphus jujuba Mill.): A review”
Authors: Xiaolong Ji, Qiang Peng, et al.
