How to predict mouthfeel in chocolate using analytical instrumentation

Abstract

Chocolate is an affordable yet luxurious treat with mature markets in Europe and North America and developing markets around the world. The secret of chocolate’s almost universal appeal is in the mouthfeel – the “snap” of the first bite, how the chocolate melts and how it coats the inside of the mouth. Despite being a consumer experience, mouthfeel is strongly related to the materials science of chocolate as a composite material. 

The particle size and rheology of the chocolate are critical factors in determining and predicting mouthfeel. In this whitepaper we will describe how laser diffraction and rheology can be used to characterise the mouthfeel of chocolate.

Introduction

Chocolate is one of the world’s favourite snack foods: over $100 billion was spent on chocolate in 2015 [1]. The unique appeal of chocolate lies in its taste, aroma and mouthfeel, or texture. These three attributes combine into the complex flavour of chocolate. As the natural ingredients of chocolate vary according to growing conditions, chocolate manufacturers go to some lengths to ensure the flavour of their chocolate products is consistent with their signature flavour. As with many food products, consumers are intensely loyal to their favourite brands and resist any changes to the flavour they expect [2]. Ensuring that the signature flavour is replicated across batches requires correlation of analytical techniques with expensive sensory testing, since it is not feasible to taste test every batch that emerges from a chocolate factory, however desirable that job might be!

The importance of particle size and rheology in chocolate manufacture

Several factors are considered important for increasing the appeal of chocolate. These include:

• Melting temperature of 37°C, so that it melts in the mouth
• Shine, so that it looks appealing
• Smooth texture, which gives a pleasant mouthfeel
• Snap, so there is an initial “bite” [3]

The textural component is critical: as consumers we prefer a smooth chocolate to a “gritty” one, and we tend to assume a smooth chocolate is a more luxurious product. Extensive consumer testing by chocolate manufacturers over decades has established that particles of cocoa solids, sugar and milk are detected as a gritty mouthfeel at sizes over 30 μm. However, the particle grinding processes in chocolate manufacture are expensive, lengthy and energy intensive so largescale manufacturers optimise their processes to achieve the required particle size as efficiently as possible. This optimisation is underpinned by regular particle size measurements, which are increasingly performed by laser diffraction instruments. While particles affect grittiness, the flow properties of the fat phase (cocoa butter, which may be mixed with other fats) control how the chocolate coats the mouth and influences the perception of flavour. The flow, or rheological, properties of the chocolate also have significant impact on the chocolate manufacturing process. Reducing the particle size increases viscosity, potentially causing blockages as the liquid chocolate is piped through the factory. The final product may be a bar, or tablet, of solid chocolate, or the chocolate may be used in an enrobing process to surround a filling centre. Chocolate for enrobing processes is often optimised to achieve good coverage and may have a different recipe than chocolate for tablets.

>> Download the full Application Note as PDF

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