title: Improving the water solubility of Monascus pigments under acidic conditions with gum arabic.
abstract: BACKGROUND
  Monascus pigments (Mps) are natural food colorants and their stability in acidic solutions is important for application in the food industry. This study aimed to evaluate the use of gum arabic (GA) as a stabilizer for maintaining the solubility of Mps in an acidic aqueous solution exposed to a high temperature, and to analyze the molecular interactions between GA and Mps.
  
  
  RESULTS
  Mps dispersed (0.2 g kg-1) in deionized water at pH 3.0-4.0 without GA formed precipitates but remained in a stable solution in the presence of GA (1 g kg-1). The significant improvement of Mps water solubility under acidic conditions was attributed to the formation of Mps-GA complexes, as indicated by a sharp increase in the fluorescence intensity. The results on particle size, zeta potential, and transmission electron microscopy further suggested that molecular binding of Mps to GA, electrostatic repulsion, and steric hindrance of GA were contributing factors to preventing the aggregation of Mps in acidic solutions. A mechanistic model was presented for GA-Mps interactions and complex structures.
  
  
  CONCLUSIONS
  GA was proven to be an effective stabilizer of natural food colorants in acidic solutions. © 2016 Society of Chemical Industry.
authors.affiliation: Department of Applied Biology and Chemical Technology, State Key Lab of Chinese Medicine and Molecular Pharmacology in Shenzhen, The Hong Kong Polytechnic University, Kowloon, Hong Kong.|Department of Medical Technology, Xiamen Medical College, Xiamen, 361000, China.|College of Food Science, South China Agricultural University, Guangzhou, 510642, China.
authors.forename: Wenjie
authors.initials: W
authors.lastname: Jian
authors.affiliation: College of Food Science, South China Agricultural University, Guangzhou, 510642, China.
authors.forename: Yuanming
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Department of Applied Biology and Chemical Technology, State Key Lab of Chinese Medicine and Molecular Pharmacology in Shenzhen, The Hong Kong Polytechnic University, Kowloon, Hong Kong.
authors.forename: Jian-Yong
authors.initials: JY
authors.lastname: Wu
mesh_terms: D005505:Food Coloring Agents / Q000737:chemistry*; D006170:Gum Arabic / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D032741:Monascus / Q000737:chemistry*; D010860:Pigments, Biological / Q000737:chemistry*; D012995:Solubility; D055672:Static Electricity
chemical_list: D005505:Food Coloring Agents; D010860:Pigments, Biological; D006170:Gum Arabic
keywords: acidic pH; gum arabic; high temperature; natural pigments; solution stability