Cheese is one of the oldest food items obtained using microbes.
Important points
- A wide range of cheeses is consumed in different parts of the world.
- Different varieties of cheese are known by their characteristic texture, flavour and taste.
- The specificity of cheese varieties comes from the microbes used during their preparation.
- Swiss cheese is prepared using a bacterium called Propionibacterium shermanii and is characterised by the presence of large holes.
- Roquefort cheese is prepared using a fungus called Penicillium roqueforti.
- Cheese can be prepared using cow milk, buffalo milk or even sheep milk.
NCERT: the large holes in Swiss cheese are due to the production of a large amount of CO2 by the bacterium Propionibacterium sharmanii (NCERT’s spelling). Roquefort cheese is ripened by growing a specific fungus on it, which gives it a particular flavour.
How microbes are used in making cheese
- Souring of milk – lactic acid bacteria (LAB) convert the milk sugar lactose into lactic acid, which lowers the pH.
- Curdling – the milk protein casein coagulates to form curd. This is often helped by the enzyme rennet (chymosin).
- Separation – the solid curd is separated from the liquid whey, then pressed and salted.
- Ripening – specific bacteria or fungi are allowed to grow in or on the cheese over weeks to months, giving each variety its texture, flavour and holes.
Quick revision: Swiss cheese – bacterium (Propionibacterium), large holes due to CO2; Roquefort cheese – fungus (Penicillium roqueforti), ripened by fungal growth. Other NCERT examples of microbes in food: Lactobacillus (curd), Saccharomyces cerevisiae (bread dough, baker’s yeast) and fermented foods like dosa and idli.