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Open AccessArticle

Melatonin in Apples and Juice: Inhibition of Browning and Microorganism Growth in Apple Juice

College of Horticulture, China Agricultural University, Beijing 100193, China
Author to whom correspondence should be addressed.
Molecules 2018, 23(3), 521;
Received: 12 January 2018 / Revised: 21 February 2018 / Accepted: 23 February 2018 / Published: 27 February 2018
Synthetic melatonin (N-acetyl-5-methoxytryptamine, MT) is popular in the US and Asian markets as a health supplement. Here, we identified a naturally occurring melatonin source in apple juice. Melatonin was present in all 18 apple cultivars tested. The highest melatonin level of the edible part of apple was detected in the apple peel. The melatonin content in ‘Fuji’ apple juice is comparable to the level of its flesh. Melatonin was consumed during the process of juicing due to its interaction with the oxidants. Melatonin addition significantly reduced the juice color change to brown (browning). The mechanism is that melatonin scavenges the free radicals, which was indicated by the ASBT analysis; therefore, inhibiting the conversion of o-diphenolic compounds into quinones. Most importantly, melatonin exhibited powerful anti-microorganism activity in juice. The exact mechanisms of this action are currently unknown. These effects of melatonin can preserve the quality and prolong the shelf life of apple juice. The results provide valuable information regarding commerciall apple juice processing and storage. View Full-Text
Keywords: melatonin; apple; juice processing; antioxidant; anti-microorganism melatonin; apple; juice processing; antioxidant; anti-microorganism
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MDPI and ACS Style

Zhang, H.; Liu, X.; Chen, T.; Ji, Y.; Shi, K.; Wang, L.; Zheng, X.; Kong, J. Melatonin in Apples and Juice: Inhibition of Browning and Microorganism Growth in Apple Juice. Molecules 2018, 23, 521.

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