Comparative studies of the effect of soaking with phosphate and salt on quality changes of white shrimp ( Penaeus vannamei) and black tiger shrimp ( Penaeus monodon)

The difference of water retention effect between white shrimp ( Penaeus vannamei, WS) and black tiger shrimp ( Penaeus monodon, BTS) after soaking in phosphate and salt was studied. The meat yield of WS (50.39%) was significantly higher than that of BTS, while the water content in BTS was comparatively lower (81.67%), and its protein content was relatively elevated (17.1%). After stirring and soaking, the weight gaining rate of WS reached 25.75%, significantly surpassing that of BTS (16.47%). Both shrimp species showed increased moisture content and cooking loss after soaking. Biexponential fitting of the transverse relaxation (T2) data revealed three to four populations in all shrimp samples, T 2b (strongly bound water), T 21 (weakly bound water), T 22 (immobilized water) and T 23 (free water). After soaking treatment, the T 21 and T 22 of both shrimp were significantly increased, indicating an enhance in water mobility. The T 2 of BTS were consistently lower than WS, revealing the lower water mobility and the narrow space between myofibrils, which was verified by microstructure. The astaxanthin content of shrimp meat determined by HPLC demonstrated that BTS can provide better reddish- orange color to increase the attractiveness of shrimp paste. The outcomes of this research provide insights for shrimp paste industrial advancement.