Effects Of Different Processing Methods On The Structure And Properties Of Tilapia Meat And Skin

Tilapia,the world’s second-largest farmed freshwater fish(after carp),originated in Africa and was gradually cultivated in southern China.Tilapia has strong ability to adapt to the environment,strong reproductive ability,and fast growth rate.The output of tilapia in my country is increasing year by year,and the annual output of aquaculture reached its peak in 2016.There are three main processing methods of tilapia in China:live fish,frozen whole tilapia and frozen tilapia fillets.Frozen tilapia fillets are the main processing method of tilapia,and the products are mainly sold abroad.However,in recent years,due to the impact of the trade war and the epidemic,the sales of all export products have been affected,and tilapia fillets are no exception.Therefore,in order to relieve the pressure on the sales of frozen tilapia fillets,it is necessary to change the export to domestic sales and increase domestic sales.It is necessary to arouse people’s enthusiasm for consumption and to develop new tilapia meat products.Using tilapia meat to process Shanghai smoked fish technology and flavor characteristics,while inheriting and promoting traditional cuisine,it provides new cooking methods for the opening of tilapia meat in the domestic market.The effect of salt addition on the appearance,moisture content,quality changes,texture characteristics and flavor substances of Shanghai smoked fish in tilapia meat processing was mainly studied.The experimental results showed that the amount of salt added had no effect on the appearance,moisture content and texture characteristics of Shanghai smoked fish processed by tilapia meat.However,there were significant differences in texture properties during processing,and frying and smoking treatments increased the hardness,gumminess,chewiness of tilapia meat.Tilapia meat processing Shanghai smoked fish still has traditional smoked fish flavors;2,6-dimethylpyrazine,2,5dimethylpyrazine,2,5-diethylpyrazine,3-ethyl-pyrazine 2,5-Dimethylpyrazine.And at 1.0%salt addition,the detected content of key flavor substances was the highest,and the detected concentrations by GC-MS were:1.727,3.573,1.483 and 4.483 μg/kg,respectively.And in terms of appearance,taste,aroma,color and sensory quality,it is also the best smoked fish with 1.0%salt added.This provides a new cooking method for the development of tilapia meat food and a new idea for the subsequent production of tilapia meat food.Tilapia fillets are the most important processed products of tilapia in the factory,but when producing tilapia fillets,a large amount of scraps will be produced,mainly including internal organs,fish heads,fish bones,fish skins,fish scales and fish fins..If a large amount of scraps cannot be value-added,developed and utilized,it will cause waste of resources and pollute the environment.Because the scraps are rich in substances,high in protein,low in fat and a lot of trace elements,they have attracted people’s attention and aroused research interest.However,the attention on tilapia scraps mainly focuses on the extraction and oxidation activity of other active substances such as gelatin and collagen,but the utilization rate is still relatively low.In order to improve the utilization rate of fish skin,it is necessary to develop fish skin value-added food.The paper mainly studies the effects of different processing methods on the appearance,pH value,yellowness value,basic components and flavor substances of tilapia skin.The experimental results show that the thermal processing method can increase the pH value of the fish skin.The pH value of the untreated fish skin is 7.07,the minimum pH is 7.65 for the steaming treatment,and the maximum pH is 8.55 for the air frying treatment.Different processing methods also have a certain impact on the appearance of fish skin.In the thermal processing method,the maximum moisture loss in roasting was 70.8g/100g,the highest protein content in microwave treatment was 57.88%,and air frying and microwave treatment had similar fat content of 2.31 and 2.08g/100g,respectively;frying and microwave treatment detected the most There are at most 53 kinds of characteristic flavor substances detected by microwave.Tilapia skin has always been stored and transported at low temperature,so there is a large amount of expenses in storage and transportation.In order to reduce costs,tilapia skin can be pretreated to make it at room temperature.It can be stored and transported without compromising the quality of the food.Vacuum freeze-drying technology is a process in which the product is frozen and then vacuum-dried to sublime water,which has the characteristics of color protection,flavor preservation and high rehydration.The effects of vacuum freeze-drying treatment of tilapia skin on the properties of skin,the molecular properties of extracted gelatins,and the emulsion stabilization properties of extracted gelatins were studied.The results suggested that all the bound,entrapped,and free water molecules were simultaneously sublimated(quickly at the first 30 min and then slowly)by sublimation in the vacuum freeze-drying process.Long vacuum freeze-drying times(60 and 150 min)decreased the amount of the four bands in SDS-PAGE pattern,increased β-sheet and random coil percentages,and decreased other three secondary structure percentages of extracted gelatins.Finally,vacuum freeze-drying of tilapia skin increased the emulsion stability of fish oil-loaded oil-inwater emulsions.This work provided basic knowledges to illustrate the effect of vacuum freeze-drying of proteinenriched tissues on the molecular and functional properties of extracted proteins.It also provided a potential route to increase the emulsion stabilization ability of proteins.