What is meant by i) invert sugar and ii) non reducing sugar.

i) Invert Sugar

Invert sugar is a mixture of glucose and fructose in nearly equal amounts, formed when sucrose (a disaccharide) is hydrolyzed by either:

• Acid hydrolysis (e.g., heating with dilute acids like citric acid or invertase enzyme).
• Enzymatic hydrolysis (using the enzyme invertase).

The name "invert sugar" arises because the optical rotation of the solution changes from +66.5° (for sucrose) to -20° (for the glucose + fructose mixture), i.e., it "inverts" from dextrorotatory (+) to levorotatory (−).

Example: Honey and commercial invert sugar syrups contain this mixture.

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ii) Non-Reducing Sugar

Non-reducing sugars are carbohydrates that do not reduce Benedict’s solution or Fehling’s solution under normal conditions because they lack a free aldehyde or ketone group to act as a reducing agent.

Glucose (reducing)Glucose (reducing)

Examples:

• Sucrose (glucose + fructose linked α-1,β-2; no free anomeric carbon).
• Trehalose (two glucose units linked α-1,α-1).

Test for Non-Reducing Sugars:

1. Hydrolyze with dilute acid or enzyme (e.g., invertase for sucrose) to break glycosidic bonds.
2. The resulting reducing sugars (e.g., glucose/fructose) can then reduce Benedict’s solution.

Glucose (reducing)Glucose (reducing)