WJEC Level 3 Certificate in Food Science and Nutrition

Electron microscope greatly enlarged image of spores escaping from a sporangium Electron microscope greatly enlarged image of spores from different species of moulds Visible mould colony growing on bread 10 The life cycle of moulds Moulds will grow on the surface of foods in large, visible colonies. They reach the food in the following way: 1. The tiny spores travel through the air and land on the surface of the food. 2. In optimum conditions, the spores germinate and the mould plants start to grow. Moulds get their energy and nutrients from the food on which they land by decomposing (decaying) it. They do this by releasing enzymes, which break down large molecules in the food and release nutrients and energy, which the moulds then absorb and use. 3. A large interconnected web of hyphae, called the mycelium, develops in the food and the sporangia start to grow. 4. When they are ‘ripe’, the sporangia burst and release the spores they contain into the air. The development and presence of moulds on food make it unfit to eat (except for those edible moulds that are used in the production of foods, such as blue-veined and soft cheeses, where they enhance the flavour and texture). Some pathogenic species of moulds also make it dangerous to eat, because they produce poisonous by-products called mycotoxins , which go into the food and can be harmful to humans and other animals if they eat the food. Yeasts Yeasts are also fungi, but are single-celled, so tend to be treated separately from moulds. They also need optimum conditions in which to grow and multiply: ⦁ A suitable temperature: 25°C to 30°C is optimum, but they can grow (slowly) in cooler temperatures ⦁ A suitable pH: pH4–4.5 (acidic) is optimum for most yeasts ⦁ A supply of moisture ⦁ A supply of energy and nutrients: particularly carbohydrates ⦁ The right level of oxygen (some species of yeasts are aerobic and some are anaerobic) ⦁ Sufficient time. Image of hyphae that have become interconnected into a mycelium 1 2 3 4 Mycotoxins – poisons produced by moulds Key term Section 1: Food Safety (LO1) Chapter 1: Micro-organisms and food safety