Inestigation Of Vacuum Freeze-drying Process Of Squid

There are a lot of problems and difficulties during the producing of freeze-dryingsquid in china. This thesis studied the water-holding and amendment agents of North Pacificsquids, optimized the process of freeze-drying and then studied the freeze drying kinetic ofsquids. Finally, we obtained freeze-drying squid products,which had good taste andrehydration with a combining method of experiment and theory. The results were showedas following:Firstly, this thesis optimized the water-holding agents of North Pacific squids. Usingcooking loss rate as an indicator, sodium tripolyphosphate, sodium pyrophosphate andsodium hexametaphosphate were chosen to study the effect on water holding capacity ofsquid muscle. Water-holding agents were optimized by response surface methodology,which was based on single factor experiment. The results showed that the best combinationwas sodium tripolyphosphate1.5%, sodium pyrophosphate1.25%and sodiumhexametaphosphate0.75%,which had the lowest cooking loss rate.Then, the amendment agents were also studied. Freeze-drying cooked squid wasregarded as research subject, the impact of6kinds of amendment such as fucose,hydrogenated starch hydrolysates, dextrin, sucrose, sorbitol and fructooligosaccharide onthe rehydration of it was studyed. The best combination was gained from single factors andorthogonal experiments. The results showed that fucose, hydrogenated starch hydrolysatesand sucrose could get better effect. The best combination was fucose3%, hydrogenatedstarch hydrolysates4%and sucrose2%.Under this condition, the rehydration ratio offreeze-dried squid was observed to be5.163.This thesis optimized the process of freeze-drying. The influence of the heatingtemperature, material thickness and pressure of drying house on drying velocity andfreeze-dried quality of squid were studied. By the single factor test and orthogonal test,wecan get the better vacuum freeze-drying process parameters: the heating temperature45℃,material thickness5mm, pressure of drying house50Pa. Under these conditions, dryingvelocity of squid was observed to be1.58g/g·h. We also studied the theoretical calculation and verification about lyophilizing time of squid. The predicted time was12.1h and theexperimental time was12.5h, and the error of it is3.31%. so the model was credible.Last, we studied the freeze drying kinetic of squid. Page equation, Classic diffusionmodel and Index model were used to validate the relationship between the water rate afterfreeze-drying and the heating temperature, material thickness, pressure of dryinghouse.We know Page equation is the best model in the study of freeze-drying kinetic ofsquid. At last, the freeze drying dynamic model is the M_R=e^-rtN, of whichr=e^{-5.8490.002+0.00000831x2},N=0.942+0.001x0.0000025x2, and it can show thechanges of the water rate during freeze-drying of squid.