Several seafood-based additives for Pacific white shrimp (Litopenaeus vannamei) are proposed: chitin whiskers (CTWK), chitosan whiskers (CSWK), and oligochitosan (OligoCS) which are all water-based nano-sized chitin and chitosan products. By simply soaking fresh shrimps in the additives, the shrimp quality, especially, the color and the texture can be maintained for as long as 48 h under storage at 4 °C. The treatment by CSWK 0.25% (w/v) in combination with 2.5% NaCl and 1% NaHCO₃ at pH 8 is an optimal condition leading to weight gain and cooking yield for as high as ∼14% and ∼18% respectively, which is similar to the treatment by using mixed phosphate compounds (MPC) (p < 0.05). CSWK swells the gaps inside the myofibrillar fibers of the shrimp flesh, resulting in a layer structure similar to that of the fresh shrimp. This is the first use of these nano-sized chitin and chitin materials as food additives for improving shelf life of freshly caught shrimp while maintaining quality.