title: Effect of oxygen concentration on photo-oxidation and photosensitizer bleaching in butter.
abstract: The effect of headspace oxygen concentration and color of light on photo-oxidation and degradation of photosensitizers in butter was studied. Butter samples were stored under 0%, 0.4%, 0.8%, 1.6%, 3.0%, 5.0%, 21% oxygen, and exposed to violet, green or red light. Storage time was 36 h. Degree of photo-oxidation was measured by a trained sensory panel. Photobleaching of six different photosensitizers was estimated based on front face fluorescence excitation and emission landscapes and spectral curve resolution (parallel factor analysis). The higher oxygen concentration, the more sensory degraded were the samples. Violet light resulted in slightly higher degrees of photo-oxidation than green and red light for low oxygen concentrations. Bleaching rate and course as function of O(2) concentration differed between the photosensitizers. It is suggested that the rate of photobleaching is a balance between type I and type II photoreactions.
authors.affiliation: MATFORSK AS, Norwegian Food Research Institute, Norway. jens.petter.wold@matforsk.no
authors.forename: Jens Petter
authors.initials: JP
authors.lastname: Wold
authors.forename: Annette
authors.initials: A
authors.lastname: Veberg Dahl
authors.forename: Frank
authors.initials: F
authors.lastname: Lundby
authors.forename: Asgeir Nikolai
authors.initials: AN
authors.lastname: Nilsen
authors.forename: Asta
authors.initials: A
authors.lastname: Juzeniene
authors.forename: Johan
authors.initials: J
authors.lastname: Moan
mesh_terms: D002079:Butter; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D017319:Photosensitizing Agents / Q000737:chemistry*
chemical_list: D017319:Photosensitizing Agents; D002079:Butter; D010100:Oxygen