title: Green tea extract as an anti-browning agent for cloudy apple juice.
abstract: BACKGROUND
  Enzymatic browning of fruits and vegetables and their products is an important factor worsening their quality. The influence of five green tea extracts at the concentrations of 1 g L-1, 2 g L-1and 3 g L-1on polyphenol oxidase (PPO) activity in fresh cloudy apple juice was investigated. Moreover, PPO inhibition by tea extract and colour stability of juice during short-time refrigerated storage was studied. The changes of juice colour during storage was expressed as the total colour differences (ΔE*), browning index (BI), yellowness index (YI), and the absorbance at 420 nm (A420).
  
  
  RESULTS
  All extracts inhibited PPO activity in fresh apple juice in concentration-dependent manner. PPO activity in pure apple juice decreased by 7% after 48 h, whereas PPO activity in samples with 1 g L-1, 2 g L-1and 3 g L-1tea extract decreased by 53%, 74%, and 96%, respectively. Browning of apple juice during storage decreased with increased concentration of green tea extract. After 48 h, extract at 1 g L-1, 2 g L-1and 3 g L-1inhibited browning of juice expressed as BI by 48%, 60%, and 86%, respectively, comparing to pure apple juice.
  
  
  CONCLUSIONS
  Green tea extract may be an effective anti-browning agent for short-time stored cloudy apple juices. © 2016 Society of Chemical Industry.
authors.affiliation: Poznań University of Economics and Business, Faculty of Commodity Science, al. Niepodległości 10, 61-875, Poznań, Poland.
authors.forename: Inga
authors.initials: I
authors.lastname: Klimczak
authors.affiliation: Poznań University of Economics and Business, Faculty of Commodity Science, al. Niepodległości 10, 61-875, Poznań, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Gliszczyńska-Świgło
mesh_terms: D000975:Antioxidants / Q000032:analysis; D004156:Catechol Oxidase / Q000037:antagonists & inhibitors*; D003116:Color; D005511:Food Handling / Q000379:methods*; D061353:Food Storage; D000067030:Fruit and Vegetable Juices / Q000032:analysis*; D027845:Malus / Q000737:chemistry* / Q000201:enzymology; D010936:Plant Extracts; D013662:Tea / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D010936:Plant Extracts; D013662:Tea; D004156:Catechol Oxidase
keywords: apple juice; colour stability; enzymatic browning; green tea extract; tyrosinase inhibition