Question

Bottled fruit juices are clearer as compared to those made at home. Explain.

Answer 1

Hint: The cell wall of fruits have pectin and proteins. To make the juices clearer we need to remove these substances.

Complete Answer:
The cell wall of fruits has cellulose, hemicellulose, pectin and proteins. The pectin is found in the primary and middle lamella of cell walls of plants, where it acts like a structural heteropolysaccharide. During ripening of fruits, these pectin are broken down by the enzyme called pectinase. Cell walls of fruits also have proteins.

Bottled juices are treated with following two enzymes in order to make them clear:
1. Pectinase: Pectinase is a class of enzyme which is used to break down pectin. These enzymes are also referred to as pectic enzymes, that includes pectolyase, polygalacturonase and pectozyme. Out of these pectinases are used in breaking down this pectin polymer into monomer monosaccharide units i.e. galacturonic acid. Pectinase enzymes are also used in various industries including juice making to improve the quality of juice.

2. Proteases: These are the enzymes which break down the peptide linkage in the amino acids to release the simplest compounds called amino acids. This therefore helps in making the fruit juices clearer.

Note: The pectinase and protease requirement is different for different types of juices. For e.g. Guava juice requires more pectinase and protease treatment compared to grape and watermelon juice.