title: The effect of ultrasound on particle size, color, viscosity and polyphenol oxidase activity of diluted avocado puree.
abstract: 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 20 kHz (375 W/cm(2)) for 0-10 min. The surface mean diameter (D[3,2]) was reduced to 13.44 μm from an original value of 52.31 μm by ultrasound after 1 min. 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 100 s(-1)) after ultrasound treatment for 1 min 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.
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China. Electronic address: bxf1221@163.com.
authors.forename: Xiufang
authors.initials: X
authors.lastname: Bi
authors.affiliation: School of Chemical Sciences, University of Auckland, 23 Symonds Street, Auckland 1010, New Zealand. Electronic address: y.hemar@auckland.ac.nz.
authors.forename: Yacine
authors.initials: Y
authors.lastname: Hemar
authors.affiliation: Chemical and Materials Engineering Department, University of Auckland, 20 Symonds Street, Auckland 1142, New Zealand. Electronic address: m.balaban@auckland.ac.nz.
authors.forename: Murat O
authors.initials: MO
authors.lastname: Balaban
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China. Electronic address: liaoxjun@hotmail.com.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Liao
mesh_terms: D002245:Carbon Dioxide / Q000494:pharmacology; D004156:Catechol Oxidase / Q000378:metabolism*; D003116:Color; D005511:Food Handling / Q000379:methods*; D010316:Particle Size; D027421:Persea / Q000737:chemistry* / Q000187:drug effects / Q000201:enzymology*; D000069453:Ultrasonic Waves; D014783:Viscosity
chemical_list: D002245:Carbon Dioxide; D004156:Catechol Oxidase
keywords: Avocado puree; PPO; Particle size; Ultrasound; Viscosity