title: Enhancing aspalathin stability in rooibos (Aspalathus linearis) ready-to-drink iced teas during storage: the role of nano-emulsification and beverage ingredients, citric and ascorbic acids.
abstract: BACKGROUND
  The effects of citric and ascorbic acids on the stability of aspalathin in rooibos (Aspalathus linearis) ready-to-drink (RTD) formulations containing fermented rooibos extract (FR), aspalathin-enriched green rooibos extract (GR) and aspalathin-enriched green rooibos extract ascorbic acid solubilisate (GR-solubilisate) were investigated during storage (12 weeks at 25 °C).
  
  
  RESULTS
  Storage of iced tea formulations containing FR and GR extracts reduced their flavonoid content. The aspalathin content of FR iced tea without citric or ascorbic acid was reduced to undetectable levels by week 8 of storage. Addition of citric acid resulted in improved stability of aspalathin, but ascorbic acid did not impart additional stability. Iso-orientin and orientin were less affected than aspalathin, presumably owing to partial conversion of aspalathin to these flavones. Similar results were obtained for GR iced tea formulations. Improved stability of aspalathin was noted in iced tea containing GR-solubilisate with or without citric acid. Lower pH was shown to favour stability, especially for fermented rooibos iced teas.
  
  
  CONCLUSIONS
  Citric and ascorbic acids contribute to the stability of rooibos flavonoids during storage. Differences in stability between formulations are not due to pH differences but may be related to the matrix.
authors.affiliation: Agricultural Research Council (Infruitec-Nietvoorbij Institute), Post-Harvest and Wine Technology Division, Private Bag X5026, Stellenbosch 7599, South Africa. dbeerd@arc.agric.za
authors.forename: Dalene
authors.initials: D
authors.lastname: de Beer
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Joubert
authors.forename: Melvi
authors.initials: M
authors.lastname: Viljoen
authors.forename: Marena
authors.initials: M
authors.lastname: Manley
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D036903:Aspalathus / Q000737:chemistry*; D001628:Beverages / Q000032:analysis*; D047188:Chalcones / Q000737:chemistry*; D019343:Citric Acid / Q000737:chemistry*; D005285:Fermentation; D005419:Flavonoids / Q000737:chemistry; D061353:Food Storage; D005960:Glucosides / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D010936:Plant Extracts / Q000737:chemistry; D013997:Time Factors
chemical_list: D047188:Chalcones; D005419:Flavonoids; D005960:Glucosides; D010936:Plant Extracts; C517016:aspalathin; D019343:Citric Acid; C065886:orientin; D001205:Ascorbic Acid