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Studies on the Drying Modle and Technology of Tilapia by Heat Pump

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Tutor: GuanZhiQiang
School: Guangdong Ocean University
Course: Aquatic Products Processing and Storage Engineering
Keywords: Tilapia,equilibrium moisture content,thinlayer drying,model,water activity
CLC: TS254.4
Type: Master's thesis
Year:  2011
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Abstract:
The drying behavior of tilapia in the flow direction of hot air by heat pump was investigated,and the suitable mathematical model was established. 1. This paper researched heat pump drying of fresh tilapia in different temperature, wind speed, thickness and shape. Results show that the impact of temperature, wind speed and thickness on the tilapia drying rate is very significant, the shape of tilapia have less effect upon the drying rate. Temperature, wind speed and specific surface and drying rate were positively correlated, and the thickness of fish and drying rate were significantly negatively correlated.2. One important property of celery is its isothermal curves during drying processing and storage. The adsorption isotherms and desorption isotherms were brought down by increase of temperature and relative moisture. When the relative moisture was small, the increasing of adsorption isotherms and desorption isotherms were little. When the relative moisture is greater than 60%, the increasing of adsorption isotherms and desorption isotherms is rising fast. And relative moisture has more influence than temperature. Desorption isotherms was bigger than adsorption isotherms, and there was hysteresis phenomenon between them.3. On the base of the above researches, the experiment data are analyzed with the SPSS17.0. The results showed that Modified Henderson model , Chang-Pfost model, Halsey model and Modified Oswin model were good due to the predicted values consistent with the observed values,and Page model was best fitted for modeling.4. Thin layer heat pump drying of fresh tilapia fillets was investigated. Meanwhile the suitable mathematical model which can be used to describe the relationship of moisture ratio and drying time was established by SPSS17.0 in this paper. The proof test results showed that Page model and Modified Page model were good due to the predicted values consistent with the observed values,and Page model was better.5. The effects of some lowering water activity additives including propylene glycol,glycerol,sodium chloride and ethanol etc. On the water activity, rehydration rate and chromatic aberration of tilapia fillets in the drying process were investigated by single factor method and L9 (34) orthogonal method. The results showed that the propylene glycol,glycerol,sodium chloride and ethanol may effectively reduce the water activity of dried tilapia fish. The experiment data of water activity,rehydration rate and chromatic aberration was analyzed by comprehensive weighted method of multiple marks that effectiveness of additives on the results of comprehensive evaluation is in this order: sodium chloride>glycerol>propylene glycol>ethanol.The optimized technological parame- ters are as follow: 3%propylene glycol,5%glycerol, 1%sodium chloride and 3%ethanol.
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