title: Thermal inactivation reaction rates for ricin are influenced by pH and carbohydrates.
abstract: Ricin is a lethal protein toxin produced by the castor bean plant. Ricin is known to possess significant heat resistance. Therefore, we placed it in a variety of foods to study the influence of the food matrix on behavior of a thermally stable protein toxin. First order rate constants for the thermal inactivation of ricin in foods and simple buffers were measured using cytotoxicity assays. We observed greater thermal stability at 75 °C for the cytotoxic activity of ricin when it was placed in a yogurt-containing fruit drink compared to its stability when placed in the other foods tested. We found that galactose and high molecular weight exopolysaccharides present in various dairy products contributed to the thermal stability of ricin. Differential scanning calorimetry also showed enhanced thermal stability for ricin at pH 4.5. Our results demonstrate the importance of considering pH and the presence of stabilizing ligands in the thermal inactivation of protein toxins in foods.
authors.affiliation: Illinois Institute of Technology, Institute for Food Safety and Health, 6502 S. Archer Rd., Bedford Park, IL 60501, USA. zhangzhe@cfsa.net.cn
authors.forename: Zhe
authors.initials: Z
authors.lastname: Zhang
authors.forename: Odbert A
authors.initials: OA
authors.lastname: Triplett
authors.forename: Kiet T
authors.initials: KT
authors.lastname: Nguyen
authors.forename: William B
authors.initials: WB
authors.lastname: Melchior
authors.forename: Kelly
authors.initials: K
authors.lastname: Taylor
authors.forename: Lauren S
authors.initials: LS
authors.lastname: Jackson
authors.forename: William H
authors.initials: WH
authors.lastname: Tolleson
mesh_terms: D000818:Animals; D002241:Carbohydrates / Q000737:chemistry*; D002460:Cell Line; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D051379:Mice; D012276:Ricin / Q000037:antagonists & inhibitors* / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D002241:Carbohydrates; D012276:Ricin
keywords: Bioterrorism; Castor beans; Cytotoxicity; Infant food; Ricin; Thermal stability