Structure evolution and bloom formation in tempered cocoa butter during long‐term storage

Abstract

Structure evolution and bloom formation in tempered cocoa butter during long-term storageStructural evolution in tempered cocoa butter (CB) and CB mixed with a cocoa butter equivalent (CBE) was examined during 26 wk of storage (at 25 7C) using atomic force microscopy, X-ray powder diffraction, colorimetry and pulsed nuclear magnetic resonance. The form V-to-VI polymorphic transition in CB started after 1 week of storage. However, fat bloom was not detected until week 3 when large crystals started to appear on the CB surface. Changes in surface topography coincided with an increase in the surface whiteness index. Addition of CBE delayed bloom development by 1-2 wk. The solid fat content (SFC) of both CB and CB 1 CBE increased gradually during the early wk of storage before reaching a summit and then decreasing slowly with time (at 25 7C). Concurrently, the surface roughened and the whiteness index increased for both CB and CB 1 CBE. We postulate that, upon bloom formation, parallel phenomena took place: (i) There was exclusion of triglyceride molecules from the CB and CB 1 CBE fat crystal networks due to continued contraction, and (ii) less stable crystals melted due to the heat release from the (re)crystallization of liquid fat onto existing surface crystals and from the ongoing form V ? VI polymorphic transition. These events resulted in the gradual decrease in SFC seen at longer storage times. In conclusion, this study demonstrated that kinetic and thermodynamic phenomena take place in CB long after it has been tempered.

Fat Bloom and Polymorphism in Chocolate Prepared with Modified Tea Seed Oil

“…This is perhaps due to the more complex crystalline forms (polymorphic structures) provided by modified oil (EIS) in the chocolate sample (Osborn and Akoh, 2002). This result is similar to that of Sonwai and Rousseau (2006), who reported that addition of cocoa butter equivalent to chocolate formulation delays bloom development by 1~2 weeks. Our finding is also in agreement with Osborn and Akoh (2002).…”

“…Values L*, a* and b* were measured using a Hunter-Lab colorimeter (Hunter Associated Laboratory, Inc., Reston, Virginia, USA) and converted to whiteness index (WI) values according to the following equation (Sonwai and Rousseau, 2006): An X-ray diffractometer (Philips, X' pert, The Netherlands) equipped with a CuKα (λ=1.54 Å) radiation source was employed to determine the polymorphic forms of the samples. The instrument setting was 40 kV with filament currents of 40 mA.…”

“…Fat bloom is a physical defect that during storage appears as dusty white spots or as a white film on the chocolate surface (Loisel et al, 1998;Sonwai and Rousseau, 2006). This defect is a major concern to chocolate industry because it makes the visual and textural quality of the product undesirable to consumer (Schenk and Peschar, 2004).…”

Blending of mango kernel fat and palm oil mid-fraction to obtain cocoa butter equivalent

“…The recommended fat blend from the above section was mixed with CB in a ratio of 5.64:1 (wt) for CB/CBE which mimicked that of typical dark chocolate where 5 % of CBE is added to the finished product (Sonwai and Rousseau 2006). Assuming that the total fat content of typical dark chocolate is 33.2 %wt of the final product, chocolate that contains 5 % CBE will contain 28.2 % CB and this will give a ratio of 5.64:1 for CB/CBE in the product.…”

“…The samples were tempered using a procedure described elsewhere (Sonwai and Rousseau 2006), then moulded into solidified discs (diameter 0 30 mm, thickness 3 mm) and put inside a temperature-controlled cabinet. L*, a* and b* values of the moulded side of the samples were measured once every week and converted to WI values using Eq.…”