Shrimps contain the active muscle protein actomyosin, which is responsible for binding water in the muscle. In the living shrimp muscle a natural phosphate, ATP (Adenosin Tri Phosphate) is controlling the structure of actinomyosin which naturally bonds or holds water. However during postmortem storage, biochemical reactions reduce the ATP resulting in a lower PH or acid condition in the muscle. The muscle protein clings together and the water binding capacity of the meat is lost. The edible meat can become dry, tough and stringy. Phosphates have the unique ability to react analogue to ATP, so that the natural water binding capacity of the protein can be restored. The high specific effect of phosphates on the water retention and the strong influence on the water binding capacity of shrimps is due to specific polyanionic effects or altered surface charges on the muscle proteins.
Phosphates are natural components of almost all foods and are also used as functional food additives in food processing. In the seafood industry phosphates have a wide application and are providing many functional uses. The most important advantages of phosphate chemical treatment of shrimp are as follows:
■ Increased water holding capacity by effective disassociation of actomyosin. Reductionof drip losses, cooking losses and thawing losses. Retention of natural nutrients. Prevention of moisture migration during thawing, reheating and storage. More juiciness and less purge, better retention of natural moisture. Improved texture and tenderness.
■ Effective sequestering of calcium and magnesium ions, resulting in better water retention.
■ Controlled PH for optimum water retention by protein swelling and for optimum color development.
■ Increased water holding capacity by effective disassociation of actomyosin. Reductionof drip losses, cooking losses and thawing losses. Retention of natural nutrients. Prevention of moisture migration during thawing, reheating and storage. More juiciness and less purge, better retention of natural moisture. Improved texture and tenderness.
■ Effective sequestering of calcium and magnesium ions, resulting in better water retention.
■ Controlled PH for optimum water retention by protein swelling and for optimum color development.
■ Less oxidative deterioration during processing by effective sequestering of prooxidative metal ions. Less potential for rancidity development and undesirable color development. Protection of flavor, color and texture.
STPP (Sodium Tri Poly Phosphate) was used as function food additive with table salt NaCl (Sodium Chloride) in drip loss analysis of value-added shrimp preparation.
Specification of STPP
Appearance White Powder
PH Value
PH Value
(1% Solution) 9.6-9.7
Solubility Complete
P2O5 57.5-58%
Na2O 42%
Solubility Complete
P2O5 57.5-58%
Na2O 42%
Guidelines
■ According to specification and legislation, certain treatments may be applied to shrimps to improve organoleptic quality, preserve yield or preserve them for further processing.
■ Examples would include sodium metabisulphite to reduce shell blacking, sodium benzoate to extend shelf-life between processes, sulphites to prevent black spot formation autolysis and sodium tri poly phosphates to maintain succulence through processing and prevent black spot after peeling, whilst common salt would be added as brine for flavour.
■ Additives should be used according to Council Directive 95/2/EC and as per buyer’s specification. Generally 2% sodium tri polyphosphate (intake penetration 0.2-0.3% in flesh) with 1% sodium chloride (table salt) is generally used for one hour soaking time.
■ The ratio and concentration of brine or polyphosphate solution to shrimp should be adjusted according to the desired product.
■ At whatever stage ingredients and additives are added, it is essential to monitor the process and product to ensure that any legislative standards are not exceeded, quality parameters are met and that where dip baths are used, the contents are changed on a regular basis according to drawn up plans.
■ The time of immersion and the temperature should be controlled to obtain the desired product. Chilled condition to be maintained throughout.
