In the competent literature, opinions were expressed to the effect that main reasons for chocolate turning grey during storage are temperature fluctuations and inadequate tempering conditions, inducing migration of fats through the matrix of chocolate particles, that follows their recrystallization on the surfaces. The loss of brilliance and emersion of turning grey are the consequences of dissipation of light on the ��clusters�� of crystals [18�C21].Brilliance is an important quality parameter of chocolate and it is a key factor for tempering control [21]. Brilliance is an optical phenomenon connected by the appearance and represents ability of the surface to reflect a direct light [22].

There exists an opinion that the turning grey of chocolate represents a development of a new phase in the fatty phase of the chocolate, which appears as the result of the polymorphous transformations of the fourth crystal form into the fifth, i.e. into the sixth one [23]. Therefore, if the chocolate is stored at temperatures below 15��C, it is possible to inhibit these polymorphous transformations [24].Changes of chocolate surface colors are mainly evaluated sensorially (using visual techniques), or by colorimetric or spectrophotometric instrumental measurement methods [9,25�C28]. The whiteness index (WI) could be used as one of the parameters of the defining of color quality characteristics (whitening of chocolate surface), which is, most probably, a consequence of AV-951 color changes induced by inadequate conditions during equalization of chocolate temperature, after the cooling phase, as well as any inadequate storage conditions [29].

2.?Materials and Methods2.1. MaterialsDuring storage of dietary chocolates after 0 �C 30, 90, 180, 270 and 360 days, two sets of experiments have been carried out in parallel:analysis of color blooming by means of CIE and CIEL*a*b* detection by an instrumental method (Minolta CR 400 colorimeter)measurement of sensory properties of the chocolates using experienced panelists.Dietary chocolate samples of different compositions produced under industrial conditions were used. The chocolate samples had the following compositions:Sample 1 – Fructose, cocoa butter, whole milk powder (19%), cocoa mass, skimmed milk powder, hazelnut paste, emulsifier (lecithin), aroma. Cocoa content at least 35%.Sample 2 – Fructose, cocoa butter, inulin, skimmed milk powder, cocoa mass, milk fat, hazelnut paste, emulsifier (soy lecithin), aroma, table salt. Cocoa parts at least 35%, milk parts at least 14%.Sample 3 – Fructose, cocoa mass, whole milk powder, cocoa butter, inulin, hazelnut mass, emulsifiers (soy lecithin, polyglycerol, polyricinolate), vanillin aroma. Cocoa parts dry basis at least 30%, fat-free dry substance at least 10.5%.