Influence of Initial Filling Fat Concentration and Storage Temperature on Nougat-filled Dark Chocolate Candies Quality
Dipl.-Ing. I. Rothkopf, Dipl.-Ing. W. Danzl,
Fraunhofer Institute for Process Engineering and Packaging IVV
Freising, Germany

Undesired optical and flavor changes, such as fat bloom, softening of the chocolate, and hardening of the filling, limit shelf life of nougat-filled dark chocolates. The suspected activators for quality loss are increasing fat fractionation, βV to βVI transformation, high storage temperature, low shell thickness, entrained filling fats and fat migration. Enrobed products are particularly susceptible, because filling fats are absorbed and thus enriched in the liquid chocolate during the enrobing process. This study will look at the combined effect of fat migration during production and fat migration during storage, using the example of nougat-filled dark chocolate pralines.
Model praline shells were produced via cold stamping, to ensure equal shell thickness, and filled with nougat. Selected amounts between 0 % and 5 % of hazelnut oil (HNO) were added to the shell chocolate, to simulate filling fat entrainment. Each lot was divided and stored at 18°C, 20°C and 23°C and analyzed periodically to observe changes over time.
To quantify HNO migration, solid fat content (SFC), the amount of crystallized fat in the sample as determined by pNMR; βV to βVI transformation was indicated by the melting temperature, measured by DSC melting curves; fat bloom was evaluated using the DigiEye System, a digital camera in an enclosed box with defined lighting conditions.
Fat bloom is enhanced on the one hand by high storage temperatures and on the other hand by high amounts of initial HNO. If there is no initial HNO, then fat bloom relates entirely to SFC. Otherwise, higher amounts of initial HNO cause lower SFC starting values but have no effect on the migration speed of HNO from the nougat-filling.
Considering all influencing factors, a storage-temperature dependent expiration date can be predicted, if the initial HNO concentration is known.