Aoyuzu, or green yuzu, is yuzu that has not ripened completely. It possesses the quintessential yuzu aroma sought after by so many. The peel is green and has lower sugar and higher acidity. Unlike Sudachi and Kabosu, Aoyuzu and Yellow Yuzu can be used anytime The peel and juice are also used for their nutritional and health benefits. They are full of vitamin C and minerals.
Yuzu peel contains the aromatic elements of Limonene and Pinene and is said to have the power to relax the mind and spirit. The indentations in the peel contain Yuzunone (6Z,8E)-undeca-6,8,10-trien-3-one) , the source of the string pleasant aroma. The peel should be squeezed for maximum aroma.
Monoterpene and Diterpene hydrocarbons make up 92% of the Yuzu essential oils. d-Limonene is especially abundant making up about 60% of the total.However, this does not produce yuzu’s characteristic aroma.
Citric Acid, the chemical behind the acidic taste has the power to restore energy and is good for digestion. Yuzu also contains Vitamin C, and Pectin. However, due to the way Yuzu is usually consumed, it’s probably a good idea not to expect large nutritional gains from the small consumed amounts.
Here is a great excerpt from:
Novel Character Impact Compounds in Yuzu (Citrus junos Sieb. ex Tanaka) Peel Oil
Yuzu (Citrus junos Sieb. ex Tanaka), a tree-grown fruit similar to a kind of sour orange, is widely used in Japanese food/cooking for its pleasant flavor. To clarify the odor-active volatiles that differentiate yuzu from other citrus fruits, sensory evaluations were conducted on yuzu peel oil. The results revealed that the polar part of yuzu peel oil was the source of the characteristic aroma of fresh yuzu fruit. By aroma extract dilution analysis (AEDA) of the polar volatile part of yuzu peel oil, seven odorants were newly identified as odor-active volatiles in yuzu peel oil in the highest flavor dilution (FD) factors of 128 and 32: oct-1-en-3-one, (E)-non-4-enal, (E)-dec-4-enal, 4-methyl-4-mercaptopentan-2-one, (E)-non-6-enal, (6Z,8E)-undeca-6,8,10-trien-3-one (Yuzunone), and (6Z,8E)-undeca-6,8,10-trien-4-ol (Yuzuol). Among the most odor-active volatiles in yuzu, (E)-non-6-enal and Yuzunone were identified for the first time solely in yuzu peel oil and not in the peel of other citrus species, and Yuzuol was identified for the first time in nature. Sensory evaluation of yuzu aroma reconstitutions revealed that the newly identified compound, Yuzunone, contributes greatly to the distinct yuzu aroma.