title: Study of the antioxidant properties of extracts obtained from nopal cactus (Opuntia ficus-indica) cladodes after convective drying.
abstract: BACKGROUND
  The process of convective drying was evaluated in terms of the bioactive compounds contained in nopal samples before and after dehydration. Total polyphenol, flavonoid, flavonol, carotene and ascorbic acid contents were determined in undehydrated and dehydrated samples. Two drying temperatures (45 and 65 °C) and two air flow rates (3 and 5 m s(-1) ) were evaluated. The rheology of samples under the best drying conditions was also studied, since it provides important information regarding processing (mixing, flow processing) as well as the sensory attributes (texture) of rehydrated samples.
  
  
  RESULTS
  Non-Newtonian shear-thinning behaviour was observed for samples dried at 45 °C, while samples dried at 65 °C showed shear-thickening behaviour, possibly caused by thermal chain scission of high-molecular-weight components.
  
  
  CONCLUSIONS
  The best conditions for bioactive compound preservation were a drying temperature of 45 °C and an air flow rate of 3 m s(-1) , resulting in 40.97 g phenols, 23.41 g flavonoids, 0.543 g β-carotene and 0.2815 g ascorbic acid kg(-1) sample as shown in table 3.
authors.affiliation: Departamento de Ingeniería Química, Facultad de Química, Edificio 'E', Lab-213, Universidad Nacional Autónoma de México (UNAM), 04510 México, DF, Mexico.
authors.forename: Luis
authors.initials: L
authors.lastname: Medina-Torres
authors.forename: E Jaime
authors.initials: EJ
authors.lastname: Vernon-Carter
authors.forename: J Alberto
authors.initials: JA
authors.lastname: Gallegos-Infante
authors.forename: Nuria E
authors.initials: NE
authors.lastname: Rocha-Guzman
authors.forename: E E
authors.initials: EE
authors.lastname: Herrera-Valencia
authors.forename: Fausto
authors.initials: F
authors.lastname: Calderas
authors.forename: Rubén
authors.initials: R
authors.lastname: Jiménez-Alvarado
mesh_terms: D000975:Antioxidants / Q000032:analysis*; D001205:Ascorbic Acid / Q000032:analysis; D055598:Chemical Phenomena; D005419:Flavonoids / Q000032:analysis; D005511:Food Handling / Q000379:methods*; D055951:Functional Food / Q000032:analysis; D006358:Hot Temperature; D008800:Mexico; D029747:Opuntia / Q000737:chemistry*; D010636:Phenols / Q000032:analysis; D035261:Plant Components, Aerial / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry*; D059808:Polyphenols; D012212:Rheology; D014783:Viscosity; D014867:Water / Q000032:analysis; D019207:beta Carotene / Q000032:analysis
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D010636:Phenols; D010936:Plant Extracts; D059808:Polyphenols; D019207:beta Carotene; D014867:Water; D001205:Ascorbic Acid