Chocolate bloom

Industrially, milk fat is commonly added to cocoa butter to produce milk chocolate. However, there is a thermodynamic incompatibihty between the miUc fat and cocoa butter solids which results in eutectic phase behavior. This eutectic formation leads to a chocolate with a decreased hardness (Timms 1980 Bama et al. 1992 Bystrom and Hartel 1994 Reddy et al. 1996). Extensive work has been carried out on the addition of milk fat to cocoa butter because of its abihty to reduce the incidence of bloom formation in chocolate (Hartel 1996 Kleinert 1961 Dimick et al. 1993). Chocolate bloom is evident as a white-gray layer on top of the chocolate surface and eventually the chocolate will acquire a crumbly texture. 

Nucleation tempering of the stiU molten fat is necessary because the cocoa butter, if left to itself, can soHdify in a number of different physical forms, ie, into an unstable form if cooled rapidly, or into an equally unacceptable super stable form if cooled too slowly, as commonly happens when a chocolate turns gray or white after being left in the sun. The coarse white fat crystals that can form in the slowly cooled center of a very thick piece of chocolate are similarly in a super stable form known in the industry as fat bloom. 

Zey, J.N., Bloom, T.F. Pottem. L.M. (1990a) Industrywide Studies Report of an Industrial Hygiene Survey at Monsanto Chemical Company, Chocolate Bayou Plant, Alvin, Texas (Report No. 84.20.16), Cincinnati, OH, National Institute for Occupational Safety and Health... 

Adding a sucrose ester to chocolate can prevent the unappetising white bloom of cocoa butter crystals which sometimes forms on its surface. In Europe, sucrose esters are given an E-code number, E473, which means they have been passed as safe to be used as food additives in all the countries of the EU. 

Research on blending milk fat and its fractions with cocoa butter to reduce costs and/or to improve stability against fat bloom in chocolates has had mixed results. Milk fat hard fractions have been reported to inhibit fat bloom formation in both milk and dark chocolates (Versteeg et al., 1994 Dimick et al., 1996b Bricknell and Hartel, 1998) but to accelerate fat bloom in compound coatings based on palm kernel oil (Ransom-Painter et al., 1997). Reddy et al. (1996) showed the importance of modifying the... 

Tietz and Hartel (2000) studied the effects of removing or adding minor components naturally present in milk fat on the crystallization of milk fat-cocoa butter blends. They suggested that at low concentrations, minor lipids act as sites for nucleation and promote the rate of crystallisation and at higher concentrations inhibit crystallisation. They concluded that the presence of minor lipids, at the concentrations naturally occurring in milk fat, were sufficient to affect crystallisation rates, chocolate microstructure and fat bloom formation in chocolate. 

Dimick, P.S., Thomas, L.N., and Versteeg, C. (1993). Potential use of fractionated anhydrous milk fat as a bloom inhibitor in dark chocolate. INFORM. 4, 504. 

Figure 22.2. Pictures of bloomed chocolate due to (A) storage, (B) fat migration, (C) heat hit, (D) over-tempering, (E) non-tempering (Lonchampt and Hartel 2004).

More recent studies have shown that bloom (or dull) can occur for both tempered and untempered chocolate (Lonchampt and Flartel 2004 Lonchampt and Hartel 2006). For untempered chocolate, the blooming essentially comes from the transition from low melting point polymorphs (thermally unstable crystals) to high melting point polymorphs (usually VI). During this transition, the material mobility is increased and the migration of fat crystals to the surface is facilitated. For tempered chocolate the different causes of blooming are ... 

Bricknell, J. and Hartel, R. W. (1998). Relation of fat bloom in chocolate to polymorphic transition of cocoa butter. Journal of the American Oil Chemists Society, 75(11) 1609-1615. 

Lonchampt, P. and Hartel, R.W. (2004). Fat bloom in chocolate and compound coatings. European Journal of Lipid Science and Technology, 106(4) 241-274. 

Walter, P. and Comillon, P. (2001). Influence of thermal conditions and presence of additives on fat bloom in chocolate. Journal of the American Oil Chemists Society, 7S(9) 927-932. 

Proper control of the crystalline microstructure leads to products with the desired textural properties and physical characteristics. For example, tempering of chocolate prior to molding or enrobing is designed to control crystallization of the cocoa butter into a large number of very small crystals that are aU in the desired polymorphic form. When controlled properly, the cocoa butter crystals in chocolate contribute to the desired appearance (shine or gloss), snap, flavor release, meltdown rate upon consumption, and stability during shelf life (fat bloom). Similar... 

Bohenin (BOB) is the name given to glycerol 1,3-behenate 2-oleate, which inhibits fat bloom when added to chocolate. It is produced in Japan by enzymic interesterification of triolein and behenic (22 0) acid or ester in the presence of a 1,3 stereospecific lipase. 

Confectionery-Liquors and Liqueur. In chocolate confectionery and for pastry creams, it is the physical properties linked to the fusion and the crystallization of the fat that are essential. For milk chocolate, for coating or in bars, AMF can be used in proportions that depend on its compatibility with cocoa butter, whose properties of hardness and rapid fusion at 35°C cannot be altered. Thus it is currently accepted that AMF with high fusion levels obtained by the fractionation technique can be used. In general, milkfat has an interesting characteristic it inhibits the appearance of fat bloom (133). 

Due to the low level of milkfat in dark chocolate, fat bloom is a problem with this product. The hard fraction of milkfat (milkfat stearin) has been reported to act as an antibloom in dark chocolate, giving the chocolate an increased shelf life. However, the use of hardened milkfat is limited in several major chocolate producing countries (133). 

Tietz, R.A., and R.W. Hartel, Effects of Minor Lipids on Crystallization of Milk Fat-Cocoa Butter Blends and Bloom Formation in Chocolate, J. Am Oil Chem. Soc. 77 163-11 (2000). 

Adenier, H., H. Chaveron, and M. Ollivon, Mechanism of Fat Bloom Development on Chocolate, in Shelf-Life Studies of Foods and Beverages Chemical, Biological, Physical, and Nutritional Aspects, edited by G. Charalambous, Amsterdam, Elsevier Science Publishers B.V., 1993, pp. 353-389. 

Differential Scanning Calorimetry as a Means of Predicting Chocolate Fat-Blooming... 

Visual Fat-Bloom Assessment. Undertempering and shorter cooling lead to a faster and more pronounced fat-bloom development. The slightly overtempered chocolate (second set-up) only shows a loss of gloss when cooled during 20 min. 

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