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Citrus is considered the most consumed fruits in many parts of the world especially orange, and the world production of orange in 2018 was estimated to be 75.4 million tons, while in Egypt was estimated to be 3.24 million tons (FAO, 2020). Orange fruits (Balady cultivar, Citrus aurantium) are very important nutritional, industrial, and commercial crop in Egypt (Khedr, 2017). Juice is the main product of orange which consumed either fresh or processed, and in both cases, the need for natural high-quality juice with minimal or no heat treatment has considerably increased (Bull et al., 2004). Natural juices are consisting of two phases: a dispersing phase (serum) and a dispersed phase (cloud) (Mei, Hao, Zhu, Gao, & Luo, 2007). The activities of both, the spoilage microorganisms and the endogenous enzymes such as pectin methylesterase (PME), will determine the quality as well as the shelf life of the orange juice (OJ). Pectin is considered to be the main component of the cell wall of plants and contributes to the rigidity and the integrity of plant tissues. PME (EC 3.1.1.11) catalysis the hydrolysis of the methyl group on C6 position of the polygalacturonic acid units of pectin resulting acidic pectin and methanol (Jolie, Duvetter, Van Loey, & Hendrickx, 2010). Therefore, endogenous plant PMEs have a great role in different plant