J Food Process Preserv. 2018;e13831. wileyonlinelibrary.com/journal/jfpp | 1 of 8 https://doi.org/10.1111/jfpp.13831 © 2018 Wiley Periodicals, Inc. 1 | INTRODUCTION Probiotics are living microorganisms that are beneficial for health upon adequate consumption. Conventionally, probiotics are added to milk‐based medium to produce fermented functional foods, such as yoghurts and cheeses (Yoon, Woodams, & Hang, 2006). Although milk is highly nutritious as it contains various vitamins and miner‐ als especially calcium, it is associated with a number of drawbacks, including high fat and cholesterol content as well as allergic reac‐ tions (Yoon et al., 2006). Individuals with lactose intolerance are also having difficulties in consuming dairy‐based probiotic‐containing products (Granato, Branco, Nazzaro, Cruz, & Faria, 2010). Previous studies utilized tomato juice (Yoon, Woodams, & Hang, 2004), beet juice (Yoon, Woodams, & Hang, 2005), cab‐ bage juice (Yoon et al., 2006), carrot juice (Tamminen, Salminen, & Ouwehand, 2013) and noni juice (Wang, Ng, Su, Tzeng, & Shyu, 2009) as substrates to produce non‐dairy probiotic drinks. Based on these previous studies, successful production of probiotic juice depends greatly on the type of vegetables or fruits and probiotic strains used. In other studies, cabbage juice (Semjonovs, Shakizova, Received: 8 May 2018 | Revised: 21 September 2018 | Accepted: 9 October 2018 DOI: 10.1111/jfpp.13831 ORIGINAL ARTICLE Effect of refrigerated storage on the physicochemical characteristics and viability of Lactobacillus plantarum in fermented watermelon juice with or without supplementation with inulin or fructooligosaccharide Elvina Amanda | Wee Sim Choo School of Science, Monash University Malaysia, Bandar Sunway, Malaysia Correspondence Wee Sim Choo, School of Science, Monash University Malaysia, Jalan Lagoon Selatan, 47500, Bandar Sunway, Selangor, Malaysia. Email: choo.wee.sim@monash.edu Funding information School of Science, Monash University Malaysia Abstract A non‐dairy probiotic drink was produced through the fermentation of watermelon juice using Lactobacillus plantarum ATCC 8014. Watermelon juice was supplemented with or without inulin or fructooligosaccharides (FOS) and fermented for 6 hr at 37°C. The effect of two weeks of refrigerated storage at 4°C on the physicochemical characteristics and viability of L. plantarum were measured. The viability of L. plan‐ tarum with or without inulin or FOS supplementation was maintained at about 11 log CFU/mL until week 2 of refrigerated storage. The pH of fermented watermelon juice continued to decrease, whereas lactic acid concentration continued to increase until week 1 of storage. The supplementation of inulin or FOS increased the total soluble solids of the juice. There was notable change of color in all fermented watermelon juices measured using colorimeter. The concentration of glucose, fructose and citric acid measured using HPLC varied over the two weeks of storage. Practical applications Watermelon is widely consumed and accepted by consumers around the world. This paper presents an alternative to process this fruit by producing a non‐dairy probiotic drink using watermelon juice as the substrate. Experimental results indicated that wa‐ termelon juice was a suitable substrate to produce probiotic drink and refrigeration for two weeks was able to maintain the quality of the juice. This drink may have the poten‐ tial to be commercialized for consumers who would prefer a fruit‐based probiotic drink.