title: New insight on crystal and spot development in hard and extra-hard cheeses: Association of spots with incomplete aggregation of curd granules.
abstract: Chemical composition and structure of different types of macroparticles (specks, spots) and microparticles (microcrystals) present in hard and extra-hard cheeses were investigated. Light microscopy revealed that the small hard specks had the structure of crystalline tyrosine, as confirmed by amino acid analysis. Spots showed a complex structure, including several curd granules, cavities, and microcrystals, and were delimited by a dense protein layer. Spots contained less moisture and ash than the adjacent cheese area, and more protein, including significantly higher contents of valine, methionine, isoleucine, leucine, tyrosine, and phenylalanine. Microcrystals were observed by light and electron microscopy and analyzed by confocal micro-Raman. Among others, calcium phosphate crystals appeared to consist of a central star-shaped structure immersed in a matrix of free fatty acids plus leucine and phenylalanine in free form or in small peptides. A hypothetical mechanism for the formation of these structures has been formulated.
authors.affiliation: Department of Food Environmental and Nutritional Sciences, State University of Milan, 20133 Milan, Italy. Electronic address: paolo.dincecco@unimi.it.
authors.forename: P
authors.initials: P
authors.lastname: D'Incecco
authors.affiliation: Department of Food Environmental and Nutritional Sciences, State University of Milan, 20133 Milan, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Limbo
authors.affiliation: Department of Agricultural and Environmental Sciences - Production, Landscape, Agroenergy, State University of Milan, 20133 Milan, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Faoro
authors.affiliation: Department of Food Environmental and Nutritional Sciences, State University of Milan, 20133 Milan, Italy.
authors.forename: J
authors.initials: J
authors.lastname: Hogenboom
authors.affiliation: Department of Food Environmental and Nutritional Sciences, State University of Milan, 20133 Milan, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Rosi
authors.affiliation: Institute of Sciences of Food Production-Italian National Research Council, 20133 Milan, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Morandi
authors.affiliation: Department of Food Environmental and Nutritional Sciences, State University of Milan, 20133 Milan, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Pellegrino
mesh_terms: D000596:Amino Acids / Q000032:analysis / Q000737:chemistry; D000818:Animals; D002130:Calcium Phosphates / Q000737:chemistry; D002611:Cheese / Q000032:analysis*; D003460:Crystallization; D005230:Fatty Acids, Nonesterified / Q000032:analysis; D005511:Food Handling; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008894:Milk Proteins / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D002130:Calcium Phosphates; D005230:Fatty Acids, Nonesterified; D008894:Milk Proteins; C020243:calcium phosphate
keywords: calcium phosphate crystal; cheese ultrastructure; electron microscopy; free amino acids; hard and extra hard cheeses