title: Powder X-ray diffraction can differentiate between enantiomeric variants of calcium lactate pentahydrate crystal in cheese.
abstract: Powder X-ray diffraction has been used for decades to identify crystals of calcium lactate pentahydrate in Cheddar cheese. According to this method, diffraction patterns are generated from a powdered sample of the crystals and compared with reference cards within a database that contains the diffraction patterns of known crystals. During a preliminary study of crystals harvested from various Cheddar cheese samples, we observed 2 slightly different but distinct diffraction patterns that suggested that calcium lactate pentahydrate may be present in 2 different crystalline forms. We hypothesized that the 2 diffraction patterns corresponded to 2 enantiomeric forms of calcium lactate pentahydrate (L- and DL-) that are believed to occur in Cheddar cheese, based on previous studies involving enzymatic analyses of the lactate enantiomers in crystals obtained from Cheddar cheeses. However, the powder X-ray diffraction database currently contains only one reference diffraction card under the title “calcium lactate pentahydrate.” To resolve this apparent gap in the powder X-ray diffraction database, we generated diffraction patterns from reagent-grade calcium l-lactate pentahydrate and laboratory-synthesized calcium dl-lactate pentahydrate. From the resulting diffraction patterns we determined that the existing reference diffraction card corresponds to calcium dl-lactate pentahydrate and that the other form of calcium lactate pentahydrate observed in cheese crystals corresponds to calcium l-lactate pentahydrate. Therefore, this report presents detailed data from the 2 diffraction patterns, which may be used to prepare 2 reference diffraction cards that differentiate calcium l-lactate pentahydrate from calcium dl-lactate pentahydrate. Furthermore, we collected crystals from the exteriors and interiors of Cheddar cheeses to demonstrate the ability of powder X-ray diffraction to differentiate between the 2 forms of calcium lactate pentahydrate crystals in Cheddar cheeses. Powder X-ray diffraction results were validated using enzymatic assays for lactate enantiomers. These results demonstrated that powder X-ray diffraction can be used as a diagnostic tool to quickly identify different forms of calcium lactate pentahydrate that may occur in Cheddar cheese.
authors.affiliation: Department of Nutrition and Food Sciences, University of Vermont, Burlington 05405-0086, USA.
authors.forename: G F
authors.initials: GF
authors.lastname: Tansman
authors.forename: P S
authors.initials: PS
authors.lastname: Kindstedt
authors.forename: J M
authors.initials: JM
authors.lastname: Hughes
mesh_terms: D000818:Animals; D017610:Calcium Compounds / Q000737:chemistry* / Q000145:classification; D002611:Cheese / Q000032:analysis*; D003460:Crystallization; D005504:Food Analysis / Q000379:methods*; D005511:Food Handling / Q000379:methods; D007773:Lactates / Q000737:chemistry* / Q000145:classification; D019344:Lactic Acid / Q000032:analysis; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D017610:Calcium Compounds; D007773:Lactates; C110051:calcium lactate; D019344:Lactic Acid