Egg Quality Deterioration Indicator

The primary indicator of deterioration in egg quality among the given options is the increased alkalinity of the egg white. This change is directly linked to the natural aging process of eggs.

Understanding Egg Deterioration

• As an egg ages, carbon dioxide ($\text{CO}_2$) escapes from the egg through the pores in the shell.
• The loss of $\text{CO}_2$ causes the $\text{pH}$ of the egg white to rise, making it more alkaline. A fresh egg typically has a $\text{pH}$ around 6.0-6.5, while an older egg's white can reach a $\text{pH}$ above 7.0, indicating increased alkalinity.
• This increased alkalinity affects the egg white's properties, such as its viscosity and ability to foam.

Evaluating Other Options

The other options indicate good egg quality or freshness:

• Egg shell is intact: A sound shell is a sign of good quality, not deterioration. Cracks indicate potential contamination or breakage.
• Small air cell: The air cell forms as the egg contents contract upon cooling after being laid. A small air cell signifies a fresh egg. As the egg ages, moisture evaporates, and the air cell enlarges.
• Firm chalazae holding the yolk in the centre: The chalazae are rope-like structures that suspend the yolk. Firm chalazae indicate a fresh egg where the yolk is stable. Weakening chalazae allow the yolk to move more freely, signalling age or poorer quality.

Therefore, increased alkalinity is the specific sign of egg quality deterioration.