Controlling temperature may be key to ensuring no oil migration from an oily filling to its chocolate coating, says a new study.
The study, which looked at peanut butter-chocolate formulations, has implications for all formulators to reduce the migration of oil from the filling to the coating that adversely affects the quality of the finished food.
Kathryn McCarthy and Michael McCarthy from the University of California, Davis report their findings in this month’s issue of the Journal of Food Science.
According to Datamonitor, the global confectionary market is valued at around $63 billion (€42.8 billion).
“Migration of oil from high oil content filling to the chocolate coating can result in undesirable quality changes in filled chocolate confectionery products,” explained the researchers. “The objective of this study was to monitor and model peanut oil migration in a 2-layer chocolate-peanut butter paste model confectionery.”
The two McCarthys formulated five two-layer chocolate systems, with variations in the milk fat content, the chocolate particle size (45 to 60 micrometres), and temperature (20 and 30 degrees Celsius). All chocolate formulations contained 26.65 and 73.35 per cent fat and non-fat solids, respectively
Using both magnetic resonance imaging and fitting this with a Fickian-based diffusion model, the researchers observed that, while migration of oil was observed at 20 degrees Celsius, significant mass transfer occurred at 30 degrees Celsius. This result indicated the importance of the temperature.
During storage, a separation of peanut oil from the peanut butter paste was observed, with the oil reaching the surface after seven days in samples stored at 20 and 30 degrees.
“This study describes the dynamic nature of the interface between the chocolate and peanut butter paste layers, quantifies the mass transfer from the peanut butter paste to the chocolate, and reinforces the importance of temperature control,” stated the researchers.
Hershey provided the samples used in the study.
In the past 15 years, cocoa crops have fallen foul to destructive diseases and drought that have seen growers lose some $700 million annually. A domino effect, the hit to supplies continues to push prices up for chocolate makers: in the past year prices have risen by almost 50 per cent on the back of shrinking supplies.
Seventy per cent of the world's cocoa is grown in Africa.
Source: Journal of Food Science
August 2008, Volume 73, Issue 6, Pages E266-E273, doi: 10.1111/j.1750-3841.2008.00797.x
“Oil Migration in Chocolate–Peanut Butter Paste Confectionery as a Function of Chocolate Formulation”
Authors: K.L. McCarthy, M.J. McCarthy