Underwater shockwaves improve antioxidant levels in yuzu juice: study
Yuzu, a sour fruit, is cultivated mainly in Japan and Korea for use in food, confectionary, beverages, cosmetics, perfumery, and aromatherapy with almost all parts of the fruit, including the peel, juice, and seeds, put to use.
Writing in Food Chemistry, researchers highlighted the fruit’s important bioactive compounds.
“These include vitamin C, beta-carotene, flavonoids, limonoids, and dietary fibre. The predominant citrus fruit-derived flavonoids are glycosides, which also function as antioxidants…Therefore, a high intake of these biological compounds in citrus fruits may reduce the risk of a range of diseases,” notes the study, while a trial from Korea earlier this year highlighted the potential of yuzu peel for diabetes treatment.
In order to test the impact of underwater pre-treatment shockwaves, a whole piece of yuzu fruit was placed in a silicone tube and subjected to the instantaneous high pressure load produced by the underwater shockwave.
The functional compound content was evaluated to determine whether this pre-treatment affects the characteristics of its juice.
Researchers at the National Institute of Technology in Okinawa discovered that employing the shockwave pre-treatment at an increased discharge and energy of 3.5 kV and 4.9 kJ respectively, led to an increase in the flavanone glycoside content and oxygen radical absorbance capacity (ORAC).
For one type of Yuzu, that grown in Rikuzentakata, the ORAC value increased by around 1.7 times upon underwater shockwave pre-treatment.
Effective extraction
“[When] employing our shockwave pretreatment method, the cell walls were disintegrated and yuzu fruits were softened, thus allowing access to the juice inside the fruits,” the researchers wrote.
“This pressurisation also allowed efficient extraction of functional compounds from the tissues of the fruit. These results indicate that the efficient extraction of ascorbic acid, flavanone glycosides, and limonoids from yuzu fruit can be achieved.”
They added that the technique was reliable and exhibited excellent performance in the extraction of functional antioxidant components from yuzu fruits when employed as a pre-processing method before the squeezing process.
“We herein demonstrated the high applicability and reliability of an underwater shockwave pre-processing treatment for improving the antioxidant functionality of yuzu fruit juice,” concludes the study.
“This methodology therefore has potential for application in a wide range of extraction processes, such as the extraction of food oils and essential oils from plants. In fact, the innovative underwater shockwave pre-treatment method may also be useful in the powdering of rice and grain.
“The dynamic control of instantaneous high pressure based on an underwater shockwave could pave the way for a new field of industrial technology.”
Source: Food Chemistry
216 (2017) 123–129
“Improving the antioxidant functionality of Citrus junos Tanaka (yuzu)
fruit juice by underwater shockwave pretreatment”
Authors: Eisuke Kuraya, et al
