Effect Of Ultra-High Pressure Treatment On The Qualities Of Low Salt Surimi

Sodium chloride(NaCl)solutions(2%-3%;0.47-0.68 M)are commonly used during surimi products processing to solubilize the myosin proteins and to promote protein unfolding.However,long-term consumption of foods rich in salt may increase the risk of developing certain diseases,such as hypertension and cardiovascular diseases.On the other hand,reducing the salt content tends to reduce the product quality because of the inadequate solubilization of myosin.However,excessive salt intake poses a potential hazard to human health.Ultra-high pressure(UHP)treatment is a non-thermal physical processing technology that has been successfully used in the improvement of protein quality of food.UHP treatment has been reported to lead to structural changes in protein molecules due to different extents of unfolding and denaturation,which result in modification of their functional properties,such as coagulation,aggregation,or gelation.This work is aimed at exploring the effects of UHP treatment on myosin and surimi,with a view to providing a reference for producing low-salt products using UHP treatment.Results were as follows:1.Moderate UHP treatment promote the accumulation of volatile compounds in the surimi,resulting in the increase of fresh and sweet free amino acids.The potential activities of AMP deaminase and acid phosphatase were decreased after UHP treatment(150～300 MPa),which may cause the increase of ATP,IMP and AMP.However,greater UHP treatment led to disruption of lysosomes and leakage of the enzyme,thus causing activation of AMP deaminase and acid phosphatase activity.GC-MS results showed that there are 40 types of volatile compounds in the surimi,of which the main ones are aldehydes,ketones and alcohols.After appropriate UHP treatment,the relative content of aldehydes and ketones was increased.2.The research showed that gel properties of low salt surimi products were significantly improved by ultra-high pressure treatment.However,heat treatment masked the effect of ultra-high pressure on surimi.The gel strength,textural properties and water binding capacity of low salt surimi products firstly increased and then decreased with increasing pressure(p<0.05),and achieved the best overall performance at 450 MPa,which showed better effects than the high salt control group.In addition,whiteness of surimi products increased with the pressure enhancing on single ultra-high pressure treatment,and this trend was also masked by the heat treatment.The results demonstrated that ultra-high pressure could compensate for the negative impact of reduced salt.3.UHP treatment(≤ 150 MPa)promote the interaction between protein groups,resulting in an increased of myosin gel strength.Upon increases in pressure(0.1-600 MPa),myosin unfolded from an a-helix to a P-sheet,leading to the exposure of buried hydrophobic and sulfhydryl groups.Therefore,the surface hydrophobicity and the reactive sulfhydryl content increased at both NaCl concentrations.The rheological modulus of groups in a low NaCl concentration(0.3 M)reached a maximum value of 150 MPa,but it decreased upon further increases in pressure(300-600 MPa);a similar tendency was also observed in the groups in a higher NaCl concentration(0.6 M).The low-field pulsed nuclear magnetic resonance data of the low-NaCl groups indicate that moderate UHP treatment(≤ 300 MPa)strengthened the water retention and structure properties of the myosin gel,while stronger UHP treatment(≥ 450 MPa)weakened them.This undesirable effect of excess UHP treatment was somewhat mitigated in the 0.6 M concentration groups.These findings show the potential use of UHP treatment in improving the gelling properties of myosin in a low salt concentration.