Food additive humectants: their functions and applications in aquatic products such as freshwater fish and seafood.

In seafood products, water‑holding agents play a pivotal role in preventing juice loss and textural dryness caused by freezing or processing. By modulating pH, chelating metal ions, and disrupting protein structures, they enhance water retention, tenderness, and yield. When used in compliance with regulations, they are safe; their primary ingredients are phosphates.

Core Mechanism of Action

pH Adjustment: Elevate the muscle system to a slightly alkaline pH (6.0–6.5), shifting it away from the isoelectric point of proteins and enhancing electrostatic repulsion, thereby causing muscle fibers to swell and retain water.

Chelating metal ions: complexes with calcium, magnesium, and other ions, thereby blocking their mediated protein cross-linking, softening the meat matrix, and inhibiting lipid oxidation.

Increasing ionic strength promotes the dissociation of actomyosin, releasing myosin to form a network gel that physically locks in free water.

Antifreeze protection: Reduces mechanical damage to cell membranes caused by freezing ice crystals, maintaining a plump morphology and elasticity after thawing.

Main application scenarios and effects

Frozen fresh products (shrimp, fish fillets, squid): After thawing, they minimize drip loss, maintain tender, plump texture, and prevent shrinkage and a dry, tough mouthfeel.

Fish surimi products (fish balls, crab sticks, shrimp paste): enhance protein gel strength and viscoelasticity, prevent disintegration during cooking, and improve the smoothness of the cut surface.

Prepared dishes and cooked seafood: improve texture after reheating, minimize nutrient loss, and maintain color and flavor stability.

Long-distance transportation and storage: extend shelf life, maintain consistent product appearance, and reduce losses due to quality deterioration.

Common Types and Compliance Standards

Main varieties: sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, disodium hydrogen phosphate, etc. (often used in combination to achieve synergistic effects).

Limitation: According to GB 2760-2024, the maximum permitted level of phosphate-based moisture‑retaining agents in frozen aquatic products is 5.0 g/kg (expressed as PO₄³⁻), and they shall be added in appropriate amounts as required by production needs.

Safety Note: When used in compliance with regulations, it poses no health risks; however, excessive use may result in a bitter taste, mask the spoilage of raw materials, or even constitute fraud (e.g., weight gain). Long-term overconsumption could impair the absorption of calcium, iron, and zinc.

Precautions: Distinguish between “ice coating” and “water‑retaining agent”: ice coating provides physical protection (an icy barrier), while the water‑retaining agent offers chemical improvement; the two complement each other rather than substitute for one another.

Identifying abnormalities: Legitimate water‑retaining products show no noticeable bitterness or astringency after washing and soaking; if the foam is excessive and the texture is unusually stiff or bitter, it may indicate unauthorized over‑addition of ingredients.

Buying advice: Prioritize products with clear, standardized labeling that comply with national standards. There’s no need to panic over the presence of “water-retaining agents,” but be wary of unmarked, bulk‑sold, low‑quality items.