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Protrusions linked to chocolate fat bloom with novel analysis method – study

By Oliver Nieburg , 12-Apr-2012

Raman horizontal and depth scans showed that the protrusions and pores continue at least 10 μm into the chocolate shell
Raman horizontal and depth scans showed that the protrusions and pores continue at least 10 μm into the chocolate shell

Researchers using a combined method of microscopy have connected protrusions in chocolate to oil migration and fat bloom.

In EU-Commission funded research, Hanna Dahlenborg et al. used Confocal Raman microscopy to analyse whether imperfections of the surface of chocolate were linked to a network of pores beneath the surface that led to fat bloom.

The results, ‘Study of the porous structure of white chocolate by confocal Raman microscopy’ suggested a link and were published online ahead of publication in the European Journal of Lipid Science and Technology.

Fat migration in chocolate products can lead to fat bloom that negatively affects the appearance and texture of products. 

Chocolate fat bloom creates unappealing white specks on the surface. Photo Credit Dr. Rodrigo Campos

Fat bloom link

“This study shows that there are actually protrusions at the chocolate surface,” said the researchers.

Previous studies using different methods of analysis had suggested that pores and protrusions on the surface of chocolate were part of a network beneath the surface.

The researchers suggested that protrusions created empty pores through temperature changes, which could lead to networks below the surface.

They said that these empty pores have shells of fat at the surface that can collapse and leave a hollow pore and channel beneath the surface.

This, they said, supports the notion that the pores are connected to oil migration in filled chocolate products and thus to fat bloom development.

Confocal Raman microscopy

Researchers in this study analysed white chocolate pralines with a hazelnut filling using Confocal Raman microscopy.

“The mechanism of fat migration in chocolate pralines is until today not fully understood, and hence the detailed developed of fat bloom remains unclear,” they said.

Confocal Raman microscopy combines two techniques: confocal microscopy and Raman spectrometry.

“This technique has evolved into a fast, direct and non-destructive method applicable in food research," said the study.

“Confocal Raman microscopy offers the possibility to scan a sample to acquire a Ramn spectrum providing chemical information, with a resolution down to optical diffraction limit,” it continued.

Hanna Dahlenborg, Anna Millqvist-Fureby,  Birgit D. Brandner, Bjorn Bergenstahl (2012) ‘Study of the porous structure of white chocolate by confocal Raman microscopy.’  European Journal of Lipid Science and Technology. DOI: 10.1002/ejlt.201200006

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