Processing of Food Commodities

Protein functionality in surimi gel manufacturing:

• Sarcoplasmic proteins (water-soluble enzymes, myoglobin) impede gel formation and are intentionally washed away during surimi dewatering.
• Myofibrillar proteins (primarily actomyosin, comprising myosin and actin, accounting for $65\text{--}75\%$ of fish muscle protein) are salt-soluble proteins indispensable for surimi manufacturing; upon adding $2\text{--}3\%\ \text{NaCl}$ and thermal cooking, they solubilize, unfold, and cross-link to form a strong, elastic three-dimensional heat-induced gel.
• Collagen (stromal connective protein) is insoluble and does not form the elastic surimi gel.
• Proteases are endogenous enzymes that degrade muscle proteins.

Egg yolk proteins are segregated into insoluble lipovitellins, phosvitin (granule fraction), low-density lipoproteins (LDL), and water-soluble globular livetins (the plasma supernatant fraction, constituting about $10\%$ of total yolk protein). Livetins ($\alpha$-, $\beta$-, and $\gamma$-livetin) are true water-soluble globular proteins derived from hen blood serum proteins (serum albumin, $\alpha_2$-glycoprotein, and $\gamma$-globulin respectively).

Option analysis:

• Livetin: Correct, the principal water-soluble protein fraction of avian egg yolk.
• Ovalbumin: Major protein of egg white (albumen), not egg yolk.
• Globulin: Salt-soluble protein class, not the specific yolk water-soluble fraction.
• Conalbumin: Ovotransferrin, a primary protein of egg white.

Exogenous plant proteases are widely utilized for post-mortem tenderization of tough meat cuts by enzymatically hydrolyzing myofibrillar proteins and connective tissue collagen. Papain (cysteine endopeptidase from Carica papaya latex), Bromelain (from Ananas comosus stems/fruit), and Ficin (from Ficus carica latex) are all classical food-grade meat-tenderizing enzymes.

Option analysis:

• Papain from papaya: Established meat tenderizer.
• Bromelain from pineapple: Established meat tenderizer.
• Ficin from figs: Highly active meat tenderizer.
• All the three mentioned in 1, 2 and 3: Correct, all three plant thiol proteases are standardly used for tenderizing meat.