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Hot chocolate: No heat resistant solution, says review

By Nathan Gray , 18-Feb-2011

Although many previous attempts have shown that heat resistant chocolate is possible, more research is needed to produce a simple, inexpensive, and tasty chocolate that is resistant to melting, according to a new review.

The study, published in Trends in Food Science & Technology, reviewed historical attempts to produce a heat resistant chocolate. The processes and formulas used to produce a melting resistant treat were outlined and critiqued, and recommendations for future work were given by the authors from the University of Guelph, Canada.

“Numerous patents from around the world indicate that much research on this topic has been done … It is a lucrative subject area in which many people have invested both time and money in hopes of finding the magic formula,” said the reviewers, led by Terri Stortz.

“Through this literature review it is evident that a heat resistant chocolate can be made. However, none of the examples illustrate a simple, inexpensive, and successful heat resistant chocolate,” they said.

The authors called for more research to be carried out and reported in peer reviewed journals, “so that a better understanding of previous attempts to produce heat resistant chocolate can be reached.”

The melting pot

Chocolate generally melts at 33.8°C, when solid cocoa butter transitions to its liquid phase. The authors noted that “it is desirable to increase this melting point, or structure chocolate in such a way that it remains solid-like at elevated temperatures.”

Manufacturers in the confectionery industry have made various attempts to produce a chocolate which doesn't melt in hot conditions, however techniques to improve heat resistance have generally resulted in poor taste or textures, making the majority of methods unsuitable.

The desirable qualities of chocolate include a shiny gloss on the surface, snap when the chocolate is broken, and a smooth texture that becomes apparent only when the chocolate melts in the mouth; the authors said that it is important to retain such qualities in a heat resistant chocolate.

Review details

The reviewers revealed the main strategies that have been employed in the past to produce heat resistant chocolate. These include enhancing network microstructure of chocolate, the addition of oil or fat binding polymers to the formula, and increasing the melting point of the fat phase.

Stortz and colleagues explained that many techniques exist to generate a sugar network in chocolate, which may prevent melting. Such techniques include the incorporation of water into formulations, and processing the chocolate in such a way that some surfaces of the sugar remain uncoated by fat.

The addition of oat flour, gelatin or cornstarch to chocolate as a binding polymer has also been successful in increasing heat resistance. However such additions can also have significant effects on flavour and texture qualities.

“Increasing the melting point of the fat phase is a well known method of producing heat resistant chocolate,” said the authors.

They noted that use of interesterification or addition of a fat with a higher melting point are two ways in which this can be achieved, but added that the majority of current techniques only raise the melting point of chocolate by a few degrees.

Looking to the future

Stortz and colleagues explained that standards for the definition and identity of chocolate are very strict. Therefore, it may be advantageous to produce heat resistant chocolate with a formulation that is least altered from conventional chocolate.

They said that as such, the addition of “non-conventional ingredients” (such as high melting fats, surfactants, or polyols) may be limited by the standards of identity of chocolate in most countries.

“It is surprising that so many attempts have been made to incorporate water into chocolate while during conventional chocolate processing water is purposefully avoided,” they said.

They added that in future studies on the subject, “it is recommended that water be eliminated from any formula or method developed.”

Source: Trends in Food Science & Technology
Published online ahead of print, doi: 10.1016/j.tifs.2011.02.001
Heat Resistant Chocolate”
Authors: T.A. Stortz, A.G. Marangoni

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