Livestock Products Technology- ICAR JRF/SRF 2024

• Bulgarian Buttermilk $\to$ (III) L. bulgaricus: High-acid fermented milk produced by monoculture inoculation of Lactobacillus delbrueckii subsp. bulgaricus, producing up to $2.0\text{--}4.0\%$ lactic acid.
• Kumiss $\to$ (IV) L. acidophilus and L. bulgaricus: Traditional fermented mare's milk involving both lactic acid bacteria (L. bulgaricus, L. acidophilus) and lactose-fermenting yeasts (Kluyveromyces marxianus) producing lactic acid and alcohol ($1\text{--}2.5\%$).
• Kefir $\to$ (II) Streptococcus lactis and Betabacterium caucasicum: Effervescent fermented milk prepared using symbiotic kefir grains containing lactic streptococci, lactobacilli (Betabacterium caucasicum / L. kefir), and yeasts.
• Yoghurt $\to$ (I) L. bulgaricus and Streptococcus thermophilus: Classic symbiotic 1:1 starter culture producing acetaldehyde, diacetyl, and lactic acid.

Correct option: (2) (A) - (III), (B) - (IV), (C) - (II), (D) - (I)

• Foaming Capacity of Egg White (Albumen):
• Egg white proteins (primarily ovalbumin, ovotransferrin, and globulins) possess remarkable amphiphilic surfactant properties.
• Upon mechanical whipping, proteins rapidly unfold and orient at the air-water interface, coagulating slightly to form a viscoelastic film that traps air bubbles into a stable foam.
• Meringues and Angel Food Cake:
• Meringues rely entirely on the volume and thermal stability of whipped egg white foams sweetened with sucrose.
• In contrast, mayonnaise and salad dressings rely on egg yolk lecithin for emulsion stabilization; scrambled eggs rely on thermal protein coagulation.

Correct option: (1) Meringues

• Nisin Production and Biology:
• Nisin (E234) is an internationally approved ribosomally synthesized antimicrobial peptide (bacteriocin / Class I lantibiotic) containing unusual amino acids (lanthionine and $\beta$-methyllanthionine).
• Produced naturally by the food-grade lactic acid bacterium Lactococcus lactis subsp. lactis.
• Mode of Action: Binds to lipid II in Gram-positive bacterial cell walls, forming stable trans-membrane pores that cause rapid leakage of ions and ATP, effectively inhibiting foodborne pathogens such as Listeria monocytogenes and Clostridium botulinum spores.

Correct option: (3) Lactococcus lactis