Top Editors ... Evolution in chocolate technology

Title: Evolution in chocolate technology
Date: 21/05/2008
Autor: By Claire Rowan

Today’s traditional and much loved chocolate products continue to be created using more and more sophisticated technology

Milk chocolate was invented by Daniel Peter as far back as 1875 and many of the best selling brands such as Nestlé’s KitKat and Masterfoods’ Mars Bar were developed more than 70 years ago, yet the need for technological advances remains great.
According to expert teams at ZDS Solingen, the Central College of the German Confectionery Industry, the need for further development work encompasses every stage of production from ensuring that cocoa remains a sustainable crop to new tempering techniques.
Much of the cocoa grown today is susceptible to destruction by pests and diseases, according to ZDS, which highlights that work remains to be done in finding environmentally acceptable and affordable methods of overcoming these problems, as well as developing methods of boosting the flavour of the finished chocolate through optimising the cocoa growing and processing conditions.
The Research Group of Industrial Microbiology and Food Biotechnology of the Vrije University Brussels (VUB) has recently conducted research on behalf of the chocolate processing specialist Barry Callebaut into the bacteria responsible for flavour creation during the fermentation of cocoa beans. Cocoa beans develop their flavour during fermentation (the process of removing the beans from the pods and leaving them, often under banana leaves or wooden boxes, to ferment for about a week, according to ZDS). During this time, the cocoa beans undergo several biochemical changes, which determine their aroma and ultimately the final chocolate product.
“This research is of great importance, because the spontaneous fermentation of cocoa, which takes place in the bush, is the basis of the entire chocolate-making process,” said Herwig Bernaert, innovation manager, healthier chocolate, Barry Callebaut, who has revealed that good fermentation is the result of the specific characteristics of lactic acid bacteria and acetic acid bacteria.
The researchers identified key metabolic pathways in Lactobacillus plantarum, Lactobacillus fermentum, and Acetobacter pasteurianus, and discovered new kinds of bacteria, such as the lactic acid bacterium, Weissella ghanensis, and the acetic acid bacterium, Acetobacter ghanensis, which are all active in developing the characteristic flavour of chocolate.
“The secrets of the spontaneous cocoa bean fermentation process are gradually being unraveled thanks to the application of a combination of microbiological and chromatographic techniques on the one hand and modern molecular and mass spectrometric techniques on the other,” explained Professor Luc De Vuyst of the VUB research group, whose findings are likely to influence Barry Callebaut’s entire chocolate making process, according to Mr Bernaert. Barry Callebaut’s expertise in chocolate, that it says ‘always goes back to the bean’, has also recently led to the development of its Acticoa production process, which is designed to preserve the high levels of polyphenols naturally present in the cocoa bean; as well as a method of producing probiotic chocolate.
Perfected in conjunction with Lal’food, the probiotic specialist, Barry Callebaut’s probiotic chocolate combines two specific strains of probiotic bacteria microencapsulated using Lal’food’s patented Probiocap encapsulation
technology.
“Ensuring the sufficient distribution of the probiotic micro-organisms in chocolate on an industrial scale is no easy task,” said Hans Vriens, chief operating officer, Barry Callebaut. “High temperatures and pressures can have a negative influence on the cell-counts of probiotic strains. We therefore developed a production system that guarantees a homogeneous blend of the probiotics in the chocolate, within a restricted temperature range, and we have succeeded in developing a special process which guarantees the survival of the probiotics in the chocolate matrix.”
Further technological advances are behind the launch at Fi Europe last year of Barry Callebaut’s white chocolate with fruit in 10 combinations such as white chocolate & banana, passion fruit, blood orange and strawberry. For healthy options with exciting new flavour opportunities, Barry Callebaut has also developed its white chocolate with cranberry, blackberry, bilberry or grape skin, for example.

Chocolate production
Clearly, although the amount and quality of cocoa beans is important to the end product, processing technology remains key to final product quality and innovation potential. Chocolate processing involves grinding the solid particles (cocoa, sugar and dried milk), usually on a roll refiner, to less than 0.03mm.
“If larger particles remain, the chocolate will taste gritty in the mouth. Although further grinding makes the chocolate smoother and creamier, it sometimes makes it melt less easily in the mouth, so control of the solid particle size is critical,” said Andréa Pernot-Barry, technical director, ZDS Solingen. “As operation of the roll refiner is not easy and needs frequent adjustment, the latest equipment automatically measures the thickness of
material leaving the top roller and uses this measurement to control the crushing parameters of the refiner.”
Refining results in a lumpy, powdery mass, which is fed into a conche, which coats the solid particles with fat – mainly cocoa butter, with or without milk fat – to create a thick liquid. The conching process is said to help develop new flavours, remove any undesirable acidic notes that are formed during fermentation, and improve the texture of the finished chocolate by further smoothing the particles.
“The conching process has changed little since it was invented in the 19th Century. It can take four to six hours for standard chocolate and as much as 72 hours to produce the highest grades,” said Mahmood Akhtar, who has been working with Professor Bronek Wedzicha at the Food Chain CIC to perfect a new process that can reduce conching time to a matter of minutes and also thereby reduce energy consumption.
The new system involves the liquid chocolate being poured onto the centre of a fast spinning heated disc. The centrifugal force creates a thin film which enables very rapid heat transfer between the disc and the liquid chocolate, according to Dr Akhtar, and this thin layer of chocolate releases any unwanted volatiles.
“We have done quantitative analysis to demonstrate that 85% of the unwanted flavours/chemicals in chocolate can be removed instantly,” said Dr Akhtar. “The spinning disc reactor not only dramatically speeds up the conching process but is also much smaller than the equipment currently used for conching.”
Further development of the technology is being part-funded by Yorkshire Forward through the Food Chain CIC, with the support of the equipment manufacturer Protensive.

Tempering
The final stage of the chocolate making process is tempering, which is used to promote cocoa butter crystallisation, with temperature adjustments being used to promote the formation of seed crystals into the right thermodynamically stable polymorphic forms to determine a chocolate’s ‘snap’, contraction, gloss and shelf life characteristics. Achieving the right crystal form depends critically on the sheartemperature- time process used.
Today’s tempering machines consist of multi-stage heat exchangers through which chocolate passes at widely differing rates making it difficult to monitor the optimum conditions required, according to researchers at the Centre for Food Quality, SIPBS, the University of Strathclyde in Glasgow, Scotland; the Nestlé Product Technology Centre in York; and Matthew Algie & Co of Glasgow, Scotland, in a recent paper - Recent Advances in Tempering & Polymorphism of Fat Crystals during Chocolate Manufacture. The paper highlights the temper metre technology
from Tricor Systems in the USA, which can be used to measure the critical parameters required for optimum tempering. Tricor System’s Temper Meter uses a built-in algorithm to calculate the degree of temper in chocolate temper units together with a temper index (slope), to define numerically the state of temper.
Tricor has recently introduced its latest Model 225 Chocolate Temper Meter: a single, compact, low-cost, easy-to-operate unit that can be used in the laboratory or on the production line. It allows operators to fill a sample cup with chocolate, place it in the unit and print or display the temper results within minutes, thereby allowing corrective action to be taken before production yield and quality or shelf life are affected. A specially designed thermoelectric cooling system combined with a design that controls sample size, probe depth and probe insertion temperature is said to eliminate measurement errors.
The chocolate equipment specialist Sollich recently unveiled its latest TurboTemper Champ TCN technology, which is designed to improve the tempering process in all known chocolate and fat masses. It is fitted with a Tempergraph that measures and saves the tempering conditions throughout production for continuous monitoring of the temper quality. Sollich can supply the system with an integrated decrystallisation function or with a TurboTemper AIRO for aeration of chocolate masses for fat-based fillings, for example.

Bloom
Despite the use of the best tempering processes, a proportion of unstable crystals can remain and, in the case of exposure to heat or poor storage conditions, can cause fat to be pushed to the surface of the chocolate where it sets giving a white bloom.
According to ZDS, an alternative process has been developed to avoid bloom, which crystallises cocoa butter to the optimum condition and then adds it into totally melted chocolate. This cocoa butter then forms the template for crystallisation during subsequent cooling (* Reference 1). “As the method is quite new and hardly any comparative studies have been run yet, it is for the time being not possible to conclude whether one method is better than the other.
It is very likely that it will depend on the further use of the chocolate,” said Ms Pernot-Barry, ZDS.
The Nestlé Product Technology Centre is currently working with the Centre for Food Quality at the University of Strathclyde to design predictive models to study the tempering behaviour of chocolates and the development of fat bloom in untempered, under-tempered and over-tempered products.
“Our focus is on structures in chocolate, mechanisms of bloom formation, oil migration mechanisms and recrystallisation in chocolate to track the early onset of fat bloom, and to go some way towards eventually discovering more effective ways of eliminating it,” said Emmanuel Ohene Afoakwa, Centre for Food Quality, University of Strathclyde. “With this work we are moving towards understanding the mechanism of the fat bloom phenomenon at a molecular level.”