The effect of ultrasound on particle size, color, viscosity and polyphenol oxidase activity of diluted avocado puree

• Published in: Ultrasonics sonochemistry 2015-11, Vol.27, p.567-575
• Main Authors: Bi, Xiufang, Hemar, Yacine, Balaban, Murat O., Liao, Xiaojun
• Format: Article
• Language: English
• Subjects: Avocado puree; Carbon Dioxide - pharmacology; Catechol Oxidase - metabolism; Color; Food Handling - methods; Particle Size; Persea - chemistry; Persea - drug effects; Persea - enzymology; PPO; Ultrasonic Waves; Ultrasound; Viscosity
• ISSN: 1350-4177; 1873-2828
• DOI: 10.1016/j.ultsonch.2015.04.011

•Ultrasound treatment of defatted avocado puree significantly decreased particle size.•Viscosity increased significantly.•Measured PPO activity increased by 180% depending on treatment.•US treatment brings measured PPO activity closer to available PPO activity. The effect of ultrasound treatment on particle size, color, viscosity, polyphenol oxidase (PPO) activity and microstructure in diluted avocado puree was investigated. The treatments were carried out at 20kHz (375W/cm2) for 0–10min. The surface mean diameter (D[3,2]) was reduced to 13.44μm from an original value of 52.31μm by ultrasound after 1min. A higher L∗ value, ΔE value and lower a∗ value was observed in ultrasound treated samples. The avocado puree dilution followed pseudoplastic flow behavior, and the viscosity of diluted avocado puree (at 100s−1) after ultrasound treatment for 1min was 6.0 and 74.4 times higher than the control samples for dilution levels of 1:2 and 1:9, respectively. PPO activity greatly increased under all treatment conditions. A maximum increase of 25.1%, 36.9% and 187.8% in PPO activity was found in samples with dilution ratios of 1:2, 1:5 and 1:9, respectively. The increase in viscosity and measured PPO activity might be related to the decrease in particle size. The microscopy images further confirmed that ultrasound treatment induced disruption of avocado puree structure.