Like bacteria, moulds play an important role in foods. They can usually be seen by the naked eye (unlike bacteria). They are multi-cellular, consist of many cells connected with together.
Moulds are saprophytes and break down complex organic materials into simpler substance. This can encourage the decay of rotting matter. In this way moulds contribute to food spoilage, i.e. the visible decay of foods that occurs after ripening or damage but which is itself does not normally lead to food poisoning.
Basically most foods can be affected by moulds. Their presence will be apparent when they start to produce blue/green ‘fur’ or orange spots on foods.
Sometimes mould growth is useful, for example they can help ripening process in some certain cheeses. Examples of product in which moulds are used are Brie and Camembert which have a white mould on the outside; Danish Blue and Stilton have blue moulds through them.
A few moulds can cause infection in man for example farmer’s lung, athlete’s foot, etc.
Typically a mould constitutes long, branched, threadlike filaments of cells called hyphae that form a mycelium, a tangled mass or tissue like aggregation.
In some fungi, protoplasm streams through hyphae, uninterrupted by cross walls. These hyphae are called coenocytic. The hyphae of other fungi have cross walls called septa with either a single pore or multiple pores that permit protoplasmic streaming. These hyphae are termed septate.
Moulds reproduce by the production of spores which are finally blown away to settle on some suitable foodstuff and develop into new mycelium.
Mould spores can be formed either by asexual or sexual methods.
Asexual reproduction occurs in several ways:
- A parent cell can divide into two daughter cells by central constriction and formation of a new cell wall.
- Somatic vegetative cells may bud to produce new organisms. This is very common in the yeasts.
- The most common method of asexual reproduction is the production of spores. Asexual spore formation occurs in an individual fungus through mitosis and subsequent cell division.