There are many challenges to improve the nutritional profile of our diet, including a reduction in fat and sugar content and enhancement of fibre. In the first of a series of articles, we will introduce methods developed at Campden BRI to reduce the fat content of biscuits. In subsequent articles, we will discuss routes to reduce the sugar content and increase the fibre content of biscuits, together with ways to reduce the fat and sugar content of biscuit cream fillings.
Fat reduction in biscuits
There are many drivers to limit the total fat content of our foods. These can be based on calorie reduction, since fat is a calorie dense nutrient, but there are also drivers to remove specific fat types from our diet, notably trans and saturated fatty acids. Fat not only contributes to the eating qualities of biscuits but also plays a functional role in dough handling and baking. Since fat has a range of technical roles, it’s important to ensure that these roles are still met in reduced fat products or in those containing a replacement material.
An innovative approach
Campden BRI has developed a novel water-in-oil emulsion which makes it possible to make a zero trans fat, reduced saturated fat and reduced total fat biscuits with the mouth feel and functionality of harder, more saturated fat.
The novel water-in-oil emulsion consists of an aqueous phase of fine droplets of an alginate solution containing sequestered calcium in an oil, which can be an everyday polyunsaturated oil such as sunflower or canola/rapeseed oil. By carefully controlling calcium release into the aqueous phase of the emulsion, a micro-dispersed alginate gel-in-oil emulsion is formed. Unlike conventional water-in-oil emulsions, the alginate gel provides a thermally stable structural component, giving the emulsion the mouth feel and technical properties of hard fats with all the benefits of reduced calories and reduced total fat with a healthier fat profile.
The ingredient, which evolved from conventional water-in-oil emulsion technology, was developed as part of a research project funded by Campden BRI’s industrial members.
The role of fat in biscuits
Fat is one of the most important ingredients in biscuits and is present at high levels in short dough biscuits. High fat products such as shortbread will typically contain up to 35% by weight of fat in the dough.
The key role of fat in biscuit dough has been described as shortening, which gives biscuits their characteristic ‘melt in the mouth’ crumbly texture. The mechanism by which fat contributes this property to biscuits is by coating flour particles during the mixing of the biscuit dough. This fat coating prevents gluten from absorbing water during mixing and becoming elastic and extensible. Gluten development is essential in bread dough but is undesirable in biscuit dough because it produces tough and chewy biscuits.
A secondary role of fat is to coat any air bubbles present in order to enhance their stability during baking. This role is similar to the stabilising effects that fats have on bubbles in bread dough and cake batter which prevent the bubbles rupturing and coalescing into larger bubbles.
While both liquid and solid fat can be used to coat wheat particles to restrict gluten development, the firmness, and therefore the machine-ability of dough, is directly related to the solid fat index (SFI) of the dough fat. Short doughs that contains liquid oil at the point of handling are difficult to machine resulting in irregular shapes . The ability to coat bubbles to retain integrity during dough handling and baking is also best found in a fat with a developed crystalline structure rather than in liquid oil. Hard fats, rather than oils, are used to provide the required functionality in biscuit dough, with the naturally produced ingredients of choice being either palm oil, which has a melting point of about 36°C, or butter, which melts at 32-35°C. The use of saturated fats is therefore central to biscuit technology.
Biscuit dough containing alginate gel-in-oil and gel-in-fat emulsions could be moulded in a rotary moulder to make satisfactory short dough biscuits. In some cases, varying amounts of recipe water were added in addition to the water introduced through the emulsion to enable moulding. At higher levels of fat replacement very little additional recipe water was added. The final biscuit moisture contents varied and oven settings were adjusted to bake out any additional water. The baking temperature for biscuits containing gel-in-fat emulsions was higher than that for those containing alginate gel-in-oil emulsions, probably reflecting the need for extra energy to melt the fat.
Examples of biscuits made using the alginate gel-in-oil emulsion to replace 50% of the butter can be seen in Figure 1 (Speirs and Bishop, 2013). Dough made with 50% butter was difficult to mould. However, dough with 50% butter and 50% of the 50:50 alginate gel-in-oil emulsion was easily mouldable, and when baked, produced biscuits of good eating quality, comparable to the control containing 100% butter.
Comparison of the total fat and saturated fat content of the control biscuits and of biscuits made with 50% of the fat replaced with a 50:50 alginate gel-in-oil is given in Table 1. The reduced fat biscuits showed a decrease of 21% in total fat and a significant decrease of 41% in saturated fat compared to the control.
We concluded that alginate gel-in-oil emulsions can be used as a partial shortening substitute in short dough biscuits, enabling significant reductions in both total and also saturated fat content to be made. It is inevitable that fat reduction will lead to changes in biscuit properties but this alginate technique produced biscuits of good quality. It would be possible to modify the recipe, processing and baking procedures to further improve the textural properties.
Figure 1: Biscuits made with alginate gel-in-oil technology. From left to right (1) control 100% butter, (2) 50% butter, (3) 50% butter plus 50% of 50:50 alginate, (4) 50% butter plus 50% of 75:25 alginate, and (5) 25% butter plus 75% of 50:50 alginate.
Table 1: Calculated fat content of biscuits
|Sample||Total fat (g/100g)||Saturated fat (g/100g)|
|Control 100% fat||21.6||10.0|
|50% fat, 50% 50:50 alginate gel-in-oil||17.0||5.9|
Authors : Andrew Hughes and Charles Speirs
Department of Baking and Cereal Processing