Technical Talk – October 2009
September 17, 2009
By John Michaelides
Baked goods, like all other foods, must be safe when consumed. At the
same time, they need to be of good quality, delivering satisfactory
taste and texture. Food manufacturers have relied on many ingredients
to ensure the safety and quality of their baked goods.
|Optimizing the safety, quality and shelf life of baked goods requires a number of carefully selected ingredients.
Continuing our series on the basic ingredients for baking, what’s the role of various ingredients in ensuring food safety and quality and shelf life extension of baked goods? What are these ingredients?
Baked goods, like all other foods, must be safe when consumed. At the same time, they need to be of good quality, delivering satisfactory taste and texture. Food manufacturers have relied on many ingredients to ensure the safety and quality of their baked goods.
The safety of baked goods is primarily concerned with microbiological contamination, as well as the danger of chemical contamination with natural toxins such as mycotoxins. The mycotoxins issue is normally controlled by the close monitoring of these toxins in flour, with bakers relying on suppliers to provide certificates of analysis confirming levels of such toxins.
Microbiological contamination, however, with the exception of spore-forming bacteria, mostly occurs after the baking process. For this reason, a variety of preservatives are used in baking formulations to ensure microbes are controlled and do not grow during the shelf life of the product. These ingredients provide safety by controlling possible pathogens as well as ensuring quality by preventing the growth of spoilage organisms. They can be synthetic chemicals or natural extracts.
Some of the commonly used synthetic antimicrobials or class II preservatives in baked goods are benzoates and sorbates, specifically the potassium and sodium salts of such compounds. Benzoates are weak antimicrobials that work best against fungi, yeast and some bacteria in foods that are acidic (low pH). As such, they are commonly used in beverages such as fruit juices, sparkling drinks and soft drinks, as well as other acidified foods such as pickles.
Propionates are also antimicrobials that are used in bakery products. They are considered more natural, because propionic acid occurs naturally in some fruits, grains and cheese. Propionates work well against bread moulds and the spore-forming bacteria that cause the “ropy” bread condition. Most bakers are familiar with this condition, which can contaminate the whole bakery; it causes the bread crumb to lose its structure, take on a characteristic pinkish colour and smell like melon.
Some of the popular natural antimicrobials are vinegar (making the food more acidic), other natural acids and raisin juice concentrate, as well as juice concentrates from other fruits. Other antimicrobials include nisin and parabens – antibiotics that may be used in food in some countries.
Preservatives do not necessarily mean that they function as antimicrobials alone. They can usually be grouped into three types: antimicrobials, which act against bacteria, moulds or yeasts; antioxidants, which slow oxidation of fats and lipids that lead to rancidity; and those agents that prevent spoilage and extend the life of fruits and vegetables from over-ripening after harvest by retarding the activity of certain enzymes.
For example, after being cut or peeled, apples and potatoes will turn brown due to an enzyme naturally present in these foods. Certain acids such as ascorbic acid (vitamin C) and citric acid prevent or slow down this process by reducing the pH at levels that prevent the activity of this enzyme. So, when you buy sliced apples to make apple pies, remember that these most likely have been treated with these acids to prevent the onset of browning.
Another spoilage mechanism of foods relates to the oxidation of fats and oils, specifically those we consider more healthful, such as the mono- and poly-unsaturated lipids. These are much more prone to oxidation than saturated fats. The oxidation process is caused by the activity of certain enzymes such as lipases and peroxidises, or by the auto-oxidation phenomenon when these lipids are exposed to oxygen.
Therefore, as soon as the grain kernel is broken open, the oxidation process begins. By exposure to heat it is possible to deactivate these enzymes and extend the shelf life of cereal ingredients such as wheat germ and bran. However, the auto-oxidation process will continue and the addition of antioxidants will be required to extend the shelf life of these products or ingredients.
Several antioxidants are available for use in the market. These include synthetic, such as BHA (Butylated Hydroxy Anisole) PG (Propyl Gallate) and TBHQ (Tertiary Butyl Hydroxy Quinone), and natural, such as rosemary extract, tocopherols (vitamin E), cloves and cinnamon.
Bakers are also phasing out the problem of staling, particularly bread products. Staling of bread is a complex issue and has been extensively investigated by many researchers. Crust staling results in soft and leathery appearance and loss of aroma as well as the development of bitter taste. Crumb staling, on the other hand, is more important and results in harder, tougher and crumblier appearance and feel.
These processes are accelerated when the bread is stored at refrigeration temperatures and quite reversible when it is exposed to heat. We may want to store bread at low temperatures to slow microbial growth but this practice will result in accelerated staling. Several ingredients are available that can be added to formulations to prevent staling and extend the shelf life of baked goods.
For example, emulsifiers and surfactants result in crumb softening by forming complexes with the gelatinizing starch and thus prolong the shelf life of baked goods by retarding the staling process. Mono and diglycerides and sodium stearoyl – 2 – lactylate (SSL) are effective crumb softeners. Many emulsifiers are available to be used for different functional effects in the production of baked goods. Most of these emulsifiers are human-made synthetic chemicals.
Mono and diglycerides may also be classified as natural, as they are found naturally in various fats and oils. However, modified ones such as ethoxylated mono and diglycerides – produced by reacting with ethylene oxide, or diacetyl tartaric acid esters of mono and diglycerides (DATEM) produced by the reaction with diacetyl tartaric acid – will not be considered natural.
Lecithin, a naturally occurring compound, was one of the first emulsifiers to be used extensively in the baking industry. The use of lecithin may be revisited since the demand for natural ingredients is increasing and consumers are looking for food products that are more natural and organic. Additional anti-staling ingredients such as enzymes are very effective in preventing staling and extending the shelf life of many baked goods.
Always keep in mind, however, thatin attempting to use these ingredients to preserve quality or ensure safety of food products, we must ensure they
are permitted for us in foods in Canada and in any other country to which we are planning to export the finished products.
Funding for this report was provided in part by Agriculture and Agri-Food Canada through the Agricultural Adaptation Council’s CanAdvance Program.
Dr. John Michaelides is Guelph Food Technology Institute’s director of research and technology. For more information, or fee-for-service help with product or process development needs, please contact GFTC at 519-821-1246 or email@example.com .
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