Question

Which one of the following is NOT used as a cryoprotectant during freeze drying of starters?

• A. Monosodium glutamate
• B. Dimethylsulphoxide
• C. Dimethyl sulphide
• D. Mannitol

Hint:

Starter Cryoprotectants:
Valid Cryoprotectants = Glycerol, DMSO (Dimethyl Sulphoxide), MSG, Mannitol, Trehalose, Sucrose.
NOT Cryoprotectants = Dimethyl Sulphide (DMS - volatile sulfur off-flavor).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Cryopreservation and lyophilization biophysics: cryoprotectants and lyoprotectants (DMSO, MSG, mannitol, glycerol, trehalose) stabilize cellular membrane bilayers and prevent ice crystal damage; dimethyl sulfide (DMS) is a volatile sulfur off-flavor compound.

Step 2: Detailed Explanation:
In starter culture preservation, cryobiology, and freeze-drying (lyophilization) technology:
1. Cryoprotective & Lyoprotective Agents: Compounds added to cell suspensions prior to freezing to prevent intracellular ice crystallization, membrane lipid peroxidation, and protein denaturation:
- Monosodium Glutamate (MSG) (A): Lyoprotectant salt stabilizing cell surface proteins.
- Dimethylsulphoxide (DMSO) (B): Penetrating cryoprotectant preserving membrane bilayers.
- Mannitol (D) Trehalose Skim Milk Powder Glycerol: Non-penetrating sugar polyols preserving vitrification.
2. Dimethyl Sulphide (DMS) (C): A volatile organic sulfur compound ($ ext{(CH}_3)_2 ext{S}$) responsible for cowy/maltery off-flavors in milk; it has no cryoprotective properties and is NOT used as a cryoprotectant.

Step 3: Final Answer:
Hence, Dimethyl sulphide is NOT used as a cryoprotectant, corresponding to option (C).