Thanks to good nutrition retention and convenient storage & transportation, freeze‑dried shrimp is a popular exported aquatic product from Southeast‑Asia and is largely sold to China, Japan, South Korea, Europe and North America for instant seafood snacks, freeze‑dried soup ingredients and pre‑cooked food. Nevertheless, as high‑protein high‑moisture aquatic raw‑material, shrimp has low production tolerance. Many processors encounter common defects including volume shrinkage, tough meat texture, poor rehydration and surface agglomeration. To obtain plump freeze‑dried shrimp with excellent rehydration performance, strict control must run through pretreatment, pre‑freezing, sublimation and desorption‑drying.
Pretreatment lays the foundation of quality. Raw shrimp need shelling, deveining and thorough rinsing. Blanching for enzyme inactivation is critical. Water temperature and soaking duration must be strictly controlled. Insufficient blanching leaves protein‑enzymes active and leads to flavor deterioration during storage; over‑blanching causes excessive protein denaturation and tough shrunken meat. After blanching, rapid cooling and full draining of surface free water are required. Heavy surface free‑water will greatly extend drying cycles and cause frozen agglomeration among shrimp. Spread shrimp in single layer on trays and avoid heavy stacking and squeezing.
Pre‑freezing: thorough deep pre‑freezing is mandatory for high‑protein shrimp. Insufficient pre‑freezing temperature or holding‑time leaves part of internal water unfrozen. Partial melting occurs under sublimation vacuum and results in severe shrinkage and hardened texture. Pre‑freezing holding‑time shall vary according to shrimp size; larger‑sized shrimp need longer holding‑time to guarantee complete freezing at shrimp core.
During sublimation drying, strictly control shelf heating rate and avoid rapid temperature rise. Sharp heating triggers fast protein denaturation and bad texture. Keep stable vacuum without frequent large‑range adjustment to prevent material impact. Ice shall sublimate and escape steadily instead of explosive vaporization.
In desorption‑drying phase, bound water shall be reduced to reasonable residual‑moisture range. Too‑high residual‑moisture leads to moisture absorption and spoilage during long‑distance sea‑transport and high‑temperature storage and shortens shelf‑life. However, excessively prolonged desorption‑drying further aggravates meat shrinkage. End‑point moisture target shall be set according to expected shelf‑life.
Besides, shrimp of different origins and sizes cannot share one fixed‑process curve. Factories shall build parameter archives for commonly‑used shrimp specifications. After discharging, finish vacuum nitrogen‑filled sealing packaging as soon as possible to isolate air and moisture and guarantee product quality during cross‑border long‑sea‑transport.
