Science Letters

Influence of power ultrasound on the quality parameters of grapefruit juice during storage

Rana Muhammad Aadil a, Xin-An Zeng a*, Arshad Mehmood Abbasi a, d, Muhammad Saeed Khan a, Saud Khalida, Saqib Jabbar b, Muhammad Abid c

a College of Light Industry and Food Sciences, South China University of Technology, 510641, Guangzhou, China

b Institute of Food Science and Nutrition, University of Sargodha, Sargodha, Pakistan

c Department of Food Technology, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi, Pakistan

d Department of Environmental Sciences, COMSATS Institute of Information Technology, Abbottabad, Pakistan

Abstract

Fresh grapefruit juice samples were subjected to ultrasound treatment at various treatment times (30, 60 and 90 min) in a bath type sonicator at a frequency of 28 KHz, radiating power of 70% (420 W) and 20°C. Grapefruit juice samples were stored in sterilized polypropylene tubes at 4�1°C for a period of 28 days. This study was initiated with the objective of calculating the effect of ultrasound treatment and storage time on acidity, pH, �Brix, electrical conductivity (EC), hunter color values (L*, a* and b*), non-enzymatic browning (NEB), cloud value (CV) and bioactive compounds of grapefruit juice. Results showed that there was no change in pH, �Brix and acidity, while a significant decrease in all the color values (L*, a* and b*) and significant increase in EC, cloud value, total antioxidant capacity (TAC), DPPH free radical scavenging activity, total phenolics (TP), total flavonoids (TF) and total flavonols was observed in all the juice samples sonicated for 30, 60 and 90 min as compared to control. During storage, NEB and hunter color values (L*, a* and b*) were increased, while CV, DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging activity, TAC, TP, TF and total flavonols were decreased significantly in all the ultrasound treatments, but more stability was determined in sonication treatment of 90 min as compared to control during storage period of 28 days. The findings of this study suggested that sonication for 90 min may be employed successfully in the processing of grapefruit juice at industrial scale.

Keywords: Ultrasound processing; grapefruit juice; storage; cloud value; polyphenols; antioxidant capacity.

Received August 5, 2013 Revised October 14, 2014 Published online first November 16, 2014

*Corresponding author Prof. Dr. Xin-An Zeng E-mail: xazeng@scut.edu.cn Phone: +86-20-87113668