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Characterizing cocoa butter seed crystals by the oil‐in‐water emulsion crystallization method
Author(s) -
Hindle Scott A.,
Povey Malcolm J. W.,
Smith Kevin W.
Publication year - 2002
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-002-0593-4
Subject(s) - nucleation , crystallization , seed crystal , emulsion , crystal (programming language) , materials science , crystal growth , isothermal process , chemical engineering , crystallography , chemistry , thermodynamics , organic chemistry , single crystal , physics , computer science , engineering , programming language
Unambiguous quantitative evidence for the catalytic action of seed crystals in cocoa butter is presented. We used an ultrasound velocity technique to determine the isothermal growth of solid fat content in cocoa butter oil‐in‐water emulsions, in which the probability of finding a seed crystal in any one droplet was around 0.37 at 14.2°C. The upper limit for the size of seed crystals in West African cocoa butter was around 0.09 μm, the Gibbs free energy for nucleation was 0.11 mj m −2 , and the concentration of seed crystals was in the range of 10 16 to 10 17 m −3 . X‐ray diffraction measurements showed that emulsified cocoa butter crystallizes in the α polymorph and does not appear to transform to the β′ form within the first 25 min of crystallization. Primary nucleation events in cocoa butter emulsions are accounted for by seed crystals. Collision‐mediated nucleation, a secondary nucleation mechanism, in which solid droplets (containing seed crystals) catalyze nucleation in liquid droplets, is shown to account for subsequent crystallization. This secondary nucleation mechanism is enhanced by stirring.