Tackling Mould and Bacterial Infestation in Bakeries

Mould in baked products is one of the facets in which food safety is being compromised. Mould consists of multi-cell micro-organisms (in contrast to most single-cell bacteria). It multiplies through the formation of spores.

Mould and its spores are everywhere in the environment: in the air, on living and non-living materials, and therefore also on food. Mould is a fungus, which is widespread throughout nature. Contamination with mould spores can take place through raw materials, room air, machinery and tools, as well as through personnel.

The Menace of Mould

Some types of mould can settle on food, which can lead to its spoilage. Individual types of mould prefer different nutrient substrates. Generally, only a few types of mould are characteristic of the spoilage of a specific group of foodstuff. . Other types of mould are used specifically for the purpose of enhancement, e.g. in the production of cheese.

Infestation of foodstuff occurs through direct contact or through spores present in the air. Mould infestation is initially only visible under a microscope. First of all, the spores germinate on a suitable (damp) breeding ground (e.g. bakery products) and develop a widespread, invisible mesh of threads (Myzel) in this product. It is only later that visible tube-like structures form on the surface – the spore carriers (mould layer), on the ends of which new spores are formed.

Mould infestation can cause myco-allergies in skin, and respiratory tracts as a result of breathing in spores. It can also cause acute and chronic mycotoxicosis. Some types of mould can form poisons (mycotoxins). A lot of mycotoxins are dangerous and damaging to health. The extremely poisonous aflatoxins are particularly notorious.

Acute symptoms of mould infestation can manifest themselves in the form of organ damage (liver, kidneys, skin and mucosa), damage to the central nervous system, and impairment of the immune system. Toxins from mould infestation that do not trigger any acute symptoms of disease may have carcinogenic characteristics and can cause genetic defects or deformities in embryos.

That is why bakery products which have become visibly mould infested must be thrown away completely. However, in order to prevent distribution of the spores throughout the environment, disposal of these mould infested products must take place carefully (without sudden movements or throwing away vigorously).

Adherence to hygiene measures during all phases of production and storage of baked goods should be the method of choice in order to minimise the attacks of mould. Here it deserves a mention that the acetic acid that is formed during sourdough leavening has a slight mould fungus-restricting effect.

During dough prepration, addition of the preservatives sorbic or propionic acid, in compliance with the food law of the country, is a means to prevent mould infestation.  During baking process, opting for sealed, firm bread crust is an option to prevent mould infestation.

During storage and packing of bakery operations, rapid cooling of baked products in atmospheres with lowest possible level of bacteria; cool and dry storage; thermal pasteurisation of cut bread in sealed packages; controlled atmosphere (CA) packaging with CO2 or a mixture of CO2 and nitrogen, in gas-tight foil are pragmatic measures to check mould infestation.

Maintaining the equipments in spic and span condition is another of the factors which can contribute towards prevention of mould infestation. Regular thorough cleaning; disinfection of machineries and operating premises if needed, is required. Regular cleaning and maintenance of ceilings and ceiling attachments such as lighting fixtures, pipelines, etc. is also needed. Mould fungus-restricting (non-toxic) ceiling and wall paint, filter and dust separation in ventilation systems, filter and ventilation duct cleaning at regular intervals are also required. Mouldy baked products should be segregated outside of production and sales premises.

The Bacterial Attack

Besides mould infestation on baked products, there is also bacterial infestation on baked products. They can occur through Bacillus species, in particular through Bacillus subtilis infection.

Bacterial infection can be spread further by the use of infected residual dough (and bread), and through inadequate cleaning of dough machinery.

The vegetative (living) cells of Bacillus subtilis are killed by the heat of the baking oven; the spores, however, survive temperatures of up to 130°C. The baking process only achieves core temperatures between 95-98°centigarde.

The spores continue to germinate in the baked products’ crumbs. Rapid reproduction takes place under favourable conditions (damp and warm). Growth of bacterial spores in the baked products’ crumbs takes place at 16 °C(pH > 5.5) and their optimum reproduction is during 28 – 40°C9(pH ≥ 6.0).

The bacterial infestation of baked products generally goes through four stages. In the stage 1, we find slightly bitter taste to the crumb with sweet, fruity smell. In the second stage the crumb is yellow coloured and decomposed, with an unpleasant smell, in the third stage we find a red-brown, greasy crumb, emanating a disgusting smell, and in the fourth stage, the crumb collapses and can be pulled apart into fine, spider’s web-like shiny threads.

The bacterial infestation in baked products mainly affects wheat breads, breads with sugar and fat content, e.g. toast breads, in unleavened bakery products, particularly those with a large diameter, wheat/rye mixed breads, and in yeast and baking powder cakes, particularly those with a low sugar and high water content.

One of the types of bacterial spoilage of bakery products takes place through rope bacteria. The rope bacteria cause an increased enzymatic decomposition through amylases and proteases. A rise in rope bacteria in bread has been observed during the recent years.

Vomiting, diarrhoea, stomach cramps, headache and sweating are the symptoms which can happen after the consumption of rope bacteria infested bread.

Dough acidification is a means of combating rope bacteria in bakery operations. Addition of baking agents against rope spoilage (including acetic acid and its salts), baking products thoroughly, rapid cooling of baked products, appropriate storage of baked goods, regular washing down of work materials with acetic acid additive are some of the other ways of combating rope bacteria in bakery operations.

The author is the MD of König Laminiertechnik GmbH. He is a Food Technologist with 35 years experience in bakery technology.

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