Effect of UV-C irradiation on the inactivation kinetics of oxidative enzymes, essential amino acids and sensory properti

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ORIGINAL ARTICLE

Effect of UV-C irradiation on the inactivation kinetics of oxidative enzymes, essential amino acids and sensory properties of coconut water Sudheer Kumar Yannam1 • Ankit Patras1 • Brahmaiah Pendyala1 • Matt Vergne2 • Ramasamy Ravi1 • Vybhav Vipul Sudhir Gopisetty1 Michael Sasges3



Revised: 16 January 2020 / Accepted: 31 March 2020 Ó Association of Food Scientists & Technologists (India) 2020

Abstract The impact of ultraviolet light (UV-C) irradiation on oxidative enzymes [Polyphenol oxidase (PPO) and Peroxidase (POD)], free essential amino acids and sensory profile of coconut water were investigated. PPO and POD activities were lost to 94 and 93%, respectively of its original value at fluence level of 400 mJ/cm2. Inactivation kinetics of both enzymes were fitted to nonlinear Weibull model with an increase in UV dosage with a high coefficient of determination (R2 [ 0.97) and low root mean square error (RMSE \ 0.06). No significant change was observed in all essential amino acids (p [ 0.05) after UV-C treatment up to maximum delivered fluence of 400 mJ/ cm2. Sensory attributes of coconut water up to a treated UV-C fluence level of 200 mJ/cm2 were well retained in terms of chosen descriptors (p [ 0.05). This study allow to further investigate the development of UV-C light technology for inhibition of spoilage enzymes and prolonged shelf-life of low acid beverages. Keywords Ultraviolet irradiation  Coconut water  Polyphenol oxidase  Peroxidase  Amino acids  Sensory attributes

& Ankit Patras [email protected] & Brahmaiah Pendyala [email protected] 1

Food Biosciences and Technology Program, Department of Agricultural and Environmental Sciences, Tennessee State University, Nashville, TN 37209, USA

2

Department of Pharmaceutical Sciences, Lipscomb University, University Park Drive, Nashville, TN 37067, USA

3

Aquafine Corporation, Valencia, CA, USA

Introduction Coconut water is a popular beverage consumed widely in Asia, South America, and Northern America. The mineral composition, low acid, and sugar content make coconut water a potential rehydrating drink (Prades et al. 2012; Saat et al. 2002). The increase in demand for coconut water has been growing worldwide because of its sensory and nutritional properties. The demand for coconut water is growing up considerably, global coconut water market was valued at * 2.2 billion USD in 2017, and forecast to reach 8.3 billion USD by 2023 (Conway 2019). Polyphenol oxidase (PPO) and peroxidase (POD), play a major role in discoloration and quality degradation occurring during the preservation of juices (Toma´s-Barbera´n and Espı´n 2001). PPO can oxidize the phenolic substrates (majorly oxidation of o-dihydroxy phenols to o-quinones) which is responsible for the production of brown colored pigments (Terefe et al. 2014). POD along with hydrogen peroxide can oxidize a wide range of phenolic compounds. These enzymes in coconut water is liable for brown, yellow or pink coloring during storage (Prades et al. 2012). Thermal inactivation of oxidative e