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There are certain items of science that are fundamental to premium bakery products.
Some bakery products have a long shelf life while others have a relatively short life. In some products, the shelf life is limited not by the bakery component but by the filling, e.g. meat pies and cream cakes. In general, the longevity of long-life products is due to their low moisture content, which is too low for spoilage organisms to grow.
The relevant parameter is not only the water content but the water activity. Water activity is a thermodynamic concept invented to explain why materials with different levels of water content do not behave in the same way chemically or biologically. The water activity reflects the ability of the water to be used in chemical or biological reactions. It is the concentration corrected for the differences in the ability of the water to undertake chemical reactions.
If a non-volatile solute were dissolved in water then the vapour pressure should decrease in a certain way for a perfect mixture. A thermodynamically ideal substance would always have a water activity of one. Originally, water activity could only be measured indirectly. One such method that was used in the food industry was to measure the weight loss of the product when held at a range of controlled relative humidities. This had the effect of holding the product over a range of water activities.
If the product was held at its own water activity it would neither gain nor loose weight. This water activity was said to be its equilibrium water activity.
A related property is the dew point. This is the point at which condensation occurs on cooling. When products are cooled the temperature must not fall to the dew point or condensation will occur. If condensation occurs on the product then product spoilage is likely.
THE SCIENCE OF PROTEINS
Proteins have been studied for a long time. Work on the solubility was continued by Osborne to produce the classifications of vegetable proteins that are still used. Studies of the solubility of proteins remains important both in characterising and purifying proteins.
The history of protein chemistry can be summarised as improved purification techniques combined with new methods of protein characterisation allied to theoretical interpretation of the results obtained. Improved computational techniques have also helped considerably.
The Wheat Seed
The wheat kernel or caryopsis is divided into three anatomical regions: the bran, the embryo, and the endosperm. Bran consists of the pericarp, the testa, the nucellar layer, and the aleurone layer.
The embryo contains lipids, enzymes (lipases and lipoxygenase), vitamins and globulin storage proteins. The largest proportion of the wheat seed is the endosperm, which contains the nutrients necessary for germination.
There is a composition gradient across the grain, with the percentage of both starch and protein rising. There is also a gradient in protein quality, with the protein nearest the center having the best baking quality. Apart from the desire for brighter products this quality gradient is the reason for the continued use of patent flour.
The enzymes in wheat, and hence in flour, that often cause problems in the bakery are present in the seed to make nutrient available to the seed. Similarly, this is why sprouted wheat causes problems if it is allowed to get into flour.
Wheat and its Proteins
The proteins that are of most interest in baking are the proteins from wheat. The wheat that is normally used is Triticum aestivum not Triticum durum which is used to make pasta.
The distinguishing property of wheat proteins is that some of them can develop into the viscoelastic mass known as gluten. The only other grain that has proteins with similar properties is rye, but the protein development is
Given that some of the protein, particularly that in wheat bran, does not form gluten it is obvious that the quality of the protein is as important as the quantity. Unfortunately, measuring the quantity of protein is easier and less controversial.
The Utility of Research on Flour Proteins
A question that occurs to those involved in the baking industry is the usability of this research on proteins regarding producing baked products. The research has in general aimed at identifying those proteins that are most important in making bread. This is because of the importance of bread. To date, the research has been used to investigate different cultivars of wheat so that the benefit to the baking industry is likely to be in enhanced supplies of wheat in both quantity and quality.
THE SCIENCE OF STARCH
Starch is a major component of almost all baked products. It most commonly is incorporated into products in the form of wheat flour but various forms of nearly pure starch such as corn flour (maize starch), wheat starch and potato starch are occasionally used.
While wheat protein is important in products such as bread, starch is important in any product made from flour. The mess that occurs if bread is made from flour with too much amylase present shows what happens if the starch is broken up by the amylase.
The food industry is now under considerable pressure over the nutritional properties of its products, so that those working in the industry have more need of nutritional knowledge than before.
The baking industry has even developed soft grain bread and other multigrain bread to supply consumers’ nutritional needs.
A major nutritional need is an energy. The amount needed varies from individual to individual and depends on the amount of energy expended.
Colligative properties are defined as depending on the number of particles present rather than the nature of the particles. In sugar confectionery the most important of these is the elevation of boiling point.
Because sugars are very soluble, very large boiling point elevations are produced, e.g. as large as 50°C. As the elevation of the boiling point is proportional to the concentration of the solute, the boiling point is,unsurprisingly, used as a measure of the concentration and hence as a process control.
The boiling point of a liquid is the temperature at which its vapour pressure is equal to the atmospheric pressure. If the pressure is increased the boiling point will increase, while reducing the pressure will reduce the boiling point. Sugar syrups are often made by boiling up a mixture of sugars to concentrate them. The use of a vacuum has several advantages. Energy consumption is reduced, browning is reduced and the process is speeded up. A common practice is to boil a mixture of sugars under atmospheric pressure to a given boiling point. A vacuum is then applied. This causes the mixture to boil under reduced pressure. This not only concentrates the mixture, but the latent heat of evaporation cools
the mixture rapidly, speeding up the production process since the product will ultimately have to be cooled to ambient temperature.
Another area where boiling points are important is regarding steam. A large proportion of food industry plant is heated by saturated steam, i.e. steam at its boiling point. The temperature of steam can be regulated by controlling the pressure. One side-effect of using vacuum boiling rather than boiling at atmospheric pressure is the that lower steam pressures are needed because the boiling point has been reduced. Lower steam pressures produce a considerable saving in terms of the capital cost of steam boilers and pipe work since they do not have to be built to stand the higher pressures.
In controlling a process the level of vacuum obtained controls the amount of water in the product, which is obviously important. The level of vacuum applied can be measured in several ways. Mercury manometers are not now used although they may once have been. The commonest measuring instrument is probably the Bourdon gauge, although various designs of pressure sensor are also used. The gauge could be calibrated in several different units Calibrations in units of length, e.g. inches or millimetres of mercury, are common – a legacy of using a mercury manometer. Alternative units of pressure used are pounds per square inch or newtons per square metre. Another system uses bars or millibars (where one bar equals one atmosphere)
What does the future hold for baked products and their manufacture?
It is reasonable to suppose that the development of biotechnology will lead to still more enzymes being used in baked products. This could lead to a rapid biochemical system that would replace the Chorleywood bread process with a rapid enzyme-based dough development system.
Another trend that is likely to affect the bakery business is the move to healthier food. This could lead to an increase in products based on wholemeal flour as well as products based on sugar replacers rather than sugar. Special sugar-free bakery products are currently made particularly for the benefit of diabetics.
Yet another trend that is likely to increase is the greater range of products available. Increased travel has produced a demand for more exotic premium bakery products.