More consumers with more money and a busy urban lifestyle are placing new demands on industrial bakers. Competition is increasing, too. That makes premium bakery products one of todays biggest opportunities for growing market share.

Innovative baked products with a captivating taste and texture are a must for manufacturers looking to expand their share of market. Bake-stable chocolate filling, which gives cookies, croissants and cakes a soft centre that stays smooth, creamy and glossy right through shelf-life is gaining popularity in Asia. However, maintaining the quality and soft centre of bake-stable chocolate filling over time is still among the biggest hurdles to overcome.

SO, WHATS THE PROBLEM?

Filling fat comprises around 30 percent of the bake-stable filling. The kind of fat chosen has far-reaching implications for the processing and sensory quality of the bake stable filling, not to mention storage and shelf-life.

Fat migration from bakery fillings is a frequent challenge in products wher the filling is baked with the dough or batter. Fillings become dry and dull as a result, often shrinking to leave a hole in their place. In the outer cookie, recrystallisation of the migrated fat leads to an unpleasant texture.

In general, liquid oil migrates from the interior of a composite product to the surface. This causes undesirable surface softening, filling drying out, interior collapse and the appearance of fat bloom on the final product surface. Because of the relatively long shelf-life of a cookie, the water content of the filling tends to be very low to prevent any potential microbiological problems.

Fat or oil migration is thus one of the most important causes that affect the quality of bake-stable chocolate fillings. Other causes like particle size of the filling ingredients can affect the fillings stability and the amount of oil migration.

BAKE STABLE STUDY

Most filled cookies are made by first baking the cake dough separately and finished by injecting the bake filling into the baked cookie dough so as to avoid the filling being exposed to high temperatures during baking.

Filled cookies wher the filling is baked together with the cookie dough can, after baking or during storage, be ruined by fat migration from the filling to the surface of cookie dough. This would cause an empty hole in the centre of cookie/cake wher the filling should be.

Also, lower levels of melt can possibly collapse a stabilised filling structure, which leads to density and texture abnormalities and eventually adds to the difficulty of creating a fluffy and creamy, yet stable filling that can withstand a bake.

The consistency and texture of the filling is crucial to maintain the quality of the filled cookie and it should be as creamy, smooth and glossy as possible. Filling consistency is mostly dependent on the property of the fat system; fat in the filling constitutes almost 30 percent of the ingredients.

A fat system with a high amount of saturated fatty acids gives a hard consistency at room temperature due to its high solid fat content and can give a waxy mouth feel when the melting point is higher than the mouth temperature. In contrast, a fat system with a higher amount of unsaturated fatty acids, that therefore possesses a melting point that lies closer to the mouth temperature, gives a creamier consistency and smoother texture.

The ratio of triglycerides in solid state to the total amount of triglycerides is termed solid fat content (SFC) and gives a measurement of the consistency at specific temperatures. SFC can be determined by the methods nuclear mass resonance (NMR) and differential scanning calorimetry (DSC).

The fat systems melting point and SFC affect the oil binding capacity (OBC) in the fat systems crystal network. OBC describes the crystal networks ability to enclose triglycerides in liquid state, without which the oil migrates out of the crystal network. The fat systems OBC is thus crucial for the quality when baking filled cookies.

Other than the fat system, the filling consists of other ingredients like lecithin, sugar and flavour, such as cocoa powder. All the ingredients are mixed homogenously and should be stable without any oil separation. In addition to fast crystallisation of the fat after baking, trials have revealed another important factor with an influence on stability—the particle size of the filling ingredients.

In a collaboration by university graduate Sandra Åman and AAK, a producer of value-added specialty vegetable fats, the stability of filled cookies was studied through bake trials and physical analysis of the filling. In the bake trial, the fat system of the fillings and the particle size were varied and the sugar in the cookie dough was varied between icing sugar or granulated sugar.

The baking was varied by using two different baking temperatures and cooling rates after baking. The cookies were evaluated and results showed that oil migrated from the filling to the surface of cookie dough. The physical analysis consisted of texture analysis, DSC and an elasticity modulus.

The result of the bake trial and the physical analysis also showed that the choice of sugar in the cookie dough affected perceived dryness. No significant difference in oil migration between the two different baking temperatures was found. However, the most important finding was that of the sensory evaluation and the texture analysis, which showed that the particle size can affect the fillings stability and the amount of oil migration.

FRUIT OF RESEARCH

Bake stable fillings therefore need to have the right texture, consistency, meltdown properties, and flavour release. In order to do this, it is necessary to build up knowledge of how different fats work in combination and in the presence of other ingredients.

For example, for nuts and nut oil, which filling fats would provide the optimum processing efficiency? Or, how do fats reach under varying storage conditions? How can high and fluctuating temperatures be overcome when maintaining the quality of chocolate fillings over time?

Over the years, manufacturers have come up with suitable solutions for the industry for bake stable filling applications. For example, AAK has developed a functional confectionery fat, designed for bake-stable chocolate fillings.

The fat provides cookies, croissants and cakes a soft centre that stays smooth, creamy and glossy right through shelf-life. It is a creamy vegetable fat blend that is highly resistant to fat separation and oxidation.

After baking, the blend crystallises rapidly on cooling. Trials were conducted and results showed that it played a key role in preventing fat migration from bakery fillings during storage, such that cookies kept their crispy exterior, while the filling remained soft and moist.

Trials in the application lab also compared the performance of two cookie fillings made with the functional fat and a control filling fat respectively. The results of the sensory evaluation and texture analysis confirmed the improved softness of the filling made with the functional fat after four months in storage.

Comprising lauric and non-lauric fats, the fat thus delivers the functionality and sensory properties required for long-life bakery products.

A HEALTHIER CHOICE

On many markets today, a trans-free label is a sign of quality and safety. Non-hydrogenated fat is used in the functional confectionery fat, which also comprises a balance of saturated and unsaturated fat content. With their lower melting point, the unsaturated fats make an important contribution to the creamier, smoother texture.

The bakery industry has stepwise improved the health profile of their products. As a result of this, many countries have lowered the acceptable trans fat content, improving things further by changing to non-trans and, at the same time, focusing on using non-hydrogenated oils and fats. With the recommendations from the World Health Organisation (WHO) about reducing the intake of saturated fats as a base, the next step is to improve health even further by also lowering the saturated content in bakery products.