|CHANG, LENG CHEE - University Of Hawaii|
|WEI, YANZHANG - Clemson University|
Submitted to: Journal of Herbs, Spices and Medicinal Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2014
Publication Date: 3/25/2015
Citation: Wall, M.M., Nishijima, K.A., Sarnoski, P.J., Keith, L.M., Chang, L., Wei, Y. 2015. Postharvest ripening of noni fruit (Morinda citrifolia) and the microbial and chemical properties of its fermented juice. Journal of Herbs, Spices and Medicinal Plants. 21:294-307.
Interpretive Summary: Noni fruit and juice extracts are reportedly therapeutic for diabetes, high blood pressure, and certain types of cancer. Noni juice is available as a nutritional supplement in the marketplace, but the processing of noni lacks standardization. Consequently, juice products may vary in chemical, physical and microbial properties depending on the processing method and duration. Research was conducted to identify and measure the microbial and chemical properties of fresh and fermented noni juice. Major changes in fungal and bacterial populations, sugars, organic acids, and ethanol were quantified during the fermentation process. The optimum fermentation time was 14 to 21 days, and the need for pasteurization was clearly demonstrated. These results will be useful in developing a standard method for producing consistent quality noni juice.
Technical Abstract: Noni (Morinda citrifolia) is a tropical plant used traditionally in Polynesia, Southeast Asia and other regions for medicinal purposes. Noni fruit and juice extracts are reportedly therapeutic for diabetes, high blood pressure, and certain types of cancer. Research was conducted to determine the physiology of noni fruit ripening, as well as the chemical and microbial changes that occur during noni juice fermentation. Mature noni fruit were held in sealed glass jars for juice production up to 42 days at 22 ºC. Ripening noni fruit had a non-climacteric respiratory pattern with an average rate of 34 mg CO2/kg-h, and no detectable ethylene production. The fungus, Mucor circinelloides f. sp. circinelloides, was consistently isolated from fermented noni juice, with peak populations at 14 days storage coincident with an increase in headspace CO2 and a decline in pH and total soluble solids. These changes preceded the highest juice yield at 21 days. Bacterial populations were greatest at 42 days. Erwinia pyrifoliae and the acetic acid bacterium, Gluconobacter frateurii, were isolated from fermented juice. Total sugar concentration (64.8 mg/mL) decreased by 37% after 7 days, whereas total organic acids (26.6 mg/mL) were highest at 28 days. The major non-volatile acids identified in noni juice included acetic, ascorbic, dehydroascorbic, galacturonic, malonic, succinic, and tartaric acids. Ethanol and acetic acid were the main fermentation products detected in noni juice.