We have all experienced the disappointment. Opening a box of expensive praline chocolates with pleasurable anticipation - only to discover that they appear to have gone off, even though it is well before their 'use-by' date.
© Fotolia, 2012
Covered with a dull, white film, they look as if they have gone mouldy.
In reality, it is not as bad as it looks. That apparent mould is nothing more than what is known in the chocolate industry - admittedly unappetisingly - as 'fat bloom'. Caused by fats penetrating from the praline centre to the surface of the chocolate and forming a thin crystallised layer, it is no danger to human health.
But it is fatal to our enjoyment of the chocolates. They certainly cannot be offered to friends and guests. More often than not, the chocolates end up in the bin - or taken back to the shop.
It is a major problem for the European chocolate industry. As much as 143,000 tonnes of chocolate are affected either by 'fat bloom' or by cracking, with a cost to the European industry of 1.2 billion euros a year.
The European chocolate sector is a world-leader, comprising around 2,000 firms, mostly small or medium sized enterprises (SMEs), employing some 200,000 people. Its exports are worth 3 billion euros a year.
And yet it is beset by what seems an intractable problem. Its products, which consumers quite reasonably expect to be presented in perfect condition, are extraordinarily vulnerable to the dangers of fat bloom and cracking. The reputation of a fine luxury brand can be destroyed in an instant.
On the flipside, if the industry could find a way of extending shelf-life and creating more certainty that its products would reach the consumer unspoiled, it could create a huge boost in sales and exports.
That was why the EU chose to fund a research project called PROPRALINE, a three year programme involving leading brand chocolate producers including Belgium's Guylian, large suppliers to the industry, specialist research institutes and SME associations, to come up with a much-needed solution.
The group conducted intensive research into ways of preventing both fat bloom and cracking. Cracking is caused when liquid content from the filling passes into the outer casing of chocolate, making the sugar and cocoa particles there swell. This results in stresses to the chocolate, which lead to cracks.
As a result of the research, funded under an EU programme intended to stimulate cooperation and innovation among SMEs, the teams identified a number of key control factors. High on this list is the process of 'tempering' the cocoa butter - the treatment of it before it crystallises and becomes solid. A consistent, reliable and reproducible process is vital.
The cooling of the chocolate is also key, as is the shape and thickness. The composition and processing of the filling are also important considerations, with the type of oil used in fat-based fillings being a key determinant of bloom development. Cracking can be exacerbated when the filling and the casing contract differently during cooling.
The PROPRALINE project clearly demonstrated that the world of high-class praline chocolates is a refined and technically complex one. There is indeed more to that box of chocolates than meets the eye.
Fortunately, with the research results due to be made available to the industry through a series of workshops and other initiatives, it can be confidently expected that fat bloom and cracking will be things that meet the consumer's eye with much less frequency.
And Europe's chocolatiers can continue to lead the world.