title: Crystallization mechanisms in cream during ripening and initial butter churning.
abstract: The temperature treatment of cream is the time-consuming step in butter production. A better understanding of the mechanisms leading to partial coalescence, such as fat crystallization during ripening and churning of the cream, will contribute to optimization of the production process. In this study, ripening and churning of cream were performed in a rheometer cell and the mechanisms of cream crystallization during churning of the cream, including the effect of ripening time, were investigated to understand how churning time and partial coalescence are affected. Crystallization mechanisms were studied as function of time by differential scanning calorimetry, nuclear magnetic resonance and by X-ray scattering. Microstructure formation was investigated by small deformation rheology and static light scattering. The study demonstrated that viscosity measurements can be used to detect phase inversion of the emulsion during churning of the cream in a rheometer cell. Longer ripening time (e.g., 5h vs. 0 h) resulted in larger butter grains (91 vs. 52 µm), higher viscosity (5.3 vs. 1.3 Pa · s), and solid fat content (41 vs. 13%). Both ripening and churning time had an effect on the thermal behavior of the cream. Despite the increase in solid fat content, no further changes in crystal polymorphism and in melting behavior were observed after 1h of ripening and after churning. The churning time significantly decreased after 0.5h of ripening, from 22.9 min for the cream where no ripening was applied to 16.23 min. Therefore, the crystallization state that promotes partial coalescence (i.e., aggregation of butter grains) is obtained within the first hour of cream ripening at 10 °C. The present study adds knowledge on the fundamental processes of crystallization and polymorphism of milk fat occurring during ripening and churning of cream. In addition, the dairy industry will benefit from these insights on the optimization of butter manufacturing.
authors.affiliation: Department of Food Science, Aarhus University, Blichers Allé 20, PO Box 50, 8830 Tjele, Denmark.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Buldo
authors.affiliation: Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen, Denmark.
authors.forename: Jacob J K
authors.initials: JJK
authors.lastname: Kirkensgaard
authors.affiliation: Department of Food Science, Aarhus University, Blichers Allé 20, PO Box 50, 8830 Tjele, Denmark. Electronic address: lars.wiking@agrsci.dk.
authors.forename: Lars
authors.initials: L
authors.lastname: Wiking
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002079:Butter / Q000032:analysis*; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D003611:Dairy Products / Q000032:analysis*; D004655:Emulsions / Q000737:chemistry; D005227:Fatty Acids / Q000032:analysis; D005511:Food Handling; D009682:Magnetic Resonance Spectroscopy; D010316:Particle Size; D013696:Temperature; D013997:Time Factors; D014783:Viscosity
chemical_list: D004655:Emulsions; D005227:Fatty Acids; D002079:Butter
keywords: butter; milk fat crystallization; partial coalescence; viscosity