Defects in Cheese

A smooth surface with a perfect sheen is the desired quality in good Mozzarella cheese. Some of the defects reported in Mozzarella cheese are poor meltability,discolouration, putrid smell, bitter taste and abnormal texture.

Traditional fresh Mozzarella and low moisture Mozzarella produced as string cheese or pizza cheese should have a very delicate flavour originating exclusively from the lactic fermentation by the starter culture. Because the flavour is very mild, other flavour notes are readily detected at low intensities and are generally considered defects. The most common flavour defects in cheeses are bitterness and high acid(sour), but rancid or unclean flavours can occur if poor-quality milk is used.

Textural defects are particularly problematical in pizza cheese because the quality of pizza cheese is defined largely by shredding and melting properties. Pizza cheese with a soft body due to high fat or moisture content, low calcium content, or excessive proteolysis may gum up the shredding equipment and take longer to process through the equipment. The resulting cheese shreds may be deformed in shape, sticky and prone to matting. When melted, such cheese may flow excessively (soupy) and lack stretch, elasticity and chewiness. At the other extreme, pizza cheese with an abnormally firm body due to low moisture or fat content may also take longer to shred and shatter and form fines during shredding. Such cheese may melt to a very tough and elastic consistency that is overly chewy. It may also blister excessively on pizza. Blisters occur when stable bubbles are formed at the cheese surface during baking, resulting in dehydration and the formation of a dried skin at the top pf the bubble. Cheese that melts to a tough, fibrous consistency will tend to form more stable bubbles and be more prone to blister formation than cheese that is less fibrous and elastic when melted. Non -enzymatic browning reactions involving reducing sugars (lactose or galactose) and amine groups (mostly from peptides and amino acids) may occur readily at the blister site and may give rise to brown or in extreme cases, black patches.

Either excessive or inadequate release of free oil from pizza cheese during melting represents important defect for pizza cheese. Excessive release of free oil results in unattractive greasy pools of oil at the surface of the pizza, whereas inadequate free oil release can lead to poor meltability, widespread skin formation and scorching at the melted cheese surface.