Composition, physicochemical properties, and thermal inactivation kinetics of polyphenol oxidase from wax apple (S yzgiu
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ORIGINAL PAPER
Composition, physicochemical properties, and thermal inactivation kinetics of polyphenol oxidase from wax apple (Syzgium samarangense) juice Eng‑Keng Seow1 · Soon‑Ming Yeap1 · Azhar Mat Easa1 · Thuan‑Chew Tan1 Received: 7 September 2020 / Accepted: 18 November 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Thermal treatment can reduce the microbial load and enzymatic activity, which is important to produce a safe and good quality product in the fruit juice industry. Hence, it is crucial to determine suitable thermal processing condition parameters based on the composition and thermal properties of enzymes present in fruit juice to avoid over-processing. The aim of this work was to determine the enzymatic inactivation kinetics of wax apple to obtain useful information for production of ready-to-drink wax apple juice. The wax apple juice prepared in the present study complied with Malaysia Food Regulations 1985 Regulation 235. The main sugars present in the wax apple juice are fructose and glucose, and traces of sucrose. High content of potassium was detected in the wax apple juice. In addition, wax apple juice contains a considerable amount of phenolic compounds. The thermal inactivation kinetics of polyphenol oxidase (PPO) followed the first order kinetic model. The activation energy, enthalpy changes, D88.4 °C, and z value of PPO obtained were 75.93 kJ/mol, 62.14 kJ/mol, 5.89 min, and 36.9 °C, respectively. In conclusion, the results evidenced that PPO which is more heat resistant than peroxidase, is a better enzyme inactivation indicator for the thermal treatment of wax apple juice. Therefore, PPO could be used as a heat treatment index for thermal processing that would be useful in designing thermal process for manufacturing of ready-todrink wax apple juice. Keywords Composition · Enzymatic inactivation kinetics · Wax apple juice · Physicochemical properties · Polyphenol oxidase
Introduction Wax apple (Syzygium samarangense) is a non-climacteric tropical fruit that is widely cultivated in Malaysia and other Southeast Asia countries, such as Thailand and Indonesia [1]. The fruits are pear-shaped with a subtly sweet taste and are generally juicy and crisp. Wax apples are usually green, pink, or light red in colour and almost all of the fruits are edible. The fruits can be consumed fresh or used to produce food products, such as sauces and jellies. Due to its juiciness,
* Eng‑Keng Seow [email protected] * Thuan‑Chew Tan [email protected] 1
Food Technology Division, School of Industrial Technology, Universiti Sains Malaysia (USM), 11800 Penang, Malaysia
the juice can also be extracted from the fruits to become thirst quenching drinks. In addition, wax apple is a rich source of phenols, flavonoids, and polyphenolic antioxidant compounds [2]. Due to the presence of these antioxidant compounds, it has been reported that the wax apple may have great potential benefits for human health [3]. Shen and Chang have postulated that the juice extract from wax apple can
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