Study On Thermodynamics Concentrating Characteristic Of Orange Juice And The Loss Of Aroma

Concentration is an important unit operations in the processing of fruit juice. The ideal concentration process for fruit juice should maintain the nutritional value and flavors of fresh fruit and have similar qualities with the fumet after diluted. As the fruit juice is heat-sensitive materials, it has brought difficults to the concentration process. Thus, choosing the right evaporation equipment for fruit juice concentration process is very important. This study is connection with the requirements of fruit juice heat evaporating concentration. Using orange juice as experimental material and the scraper film evaporator as the main experimental equipment. Focused on scraper film evaporator heat transfer characteristics and the aroma loss of orange juice during evaporating concentration process. The experiment datum show that:(1) By analyzing the effect of main operating parameters on heat transfer coefficient of evaporator:it increased with the material flow first and then decreased with it, and increased with the evaporation temperature, and decreased with the material concentration.(2) By analyzing the effect of main operating parameters on evaporation efficiency of scraper film evaporator:it increased with the evaporating temperature and the heating temperature, and decreased while the material concentration increased. Evaporation efficiency of the device can up to78%when the material is distilled water, and can up to75%and64%separately while using the initial Brix is10%and12%of orange juice as material.(3) In this study,92aroma components were identified from fumet. Among these aromatic substances, the key aromatic substances of orange juice is15kinds. Total relative contents of these aroma is98.523%. One of the most important aromatic components is limonene, and its relative contents is92.07%.(4) By analyzing the aromatic substance test datum:15kinds of key aromatic substances divided into two groups:one group reduced with the increased heating temperature, and another another group increased with the increased heating temperature during the scraper film evaporator concentrating orange juice.(5) Through linear regression the datum of total aroma components and the total key aroma components relative content which changed with the heating temperature, got relational expressions and found the changes in line with second-order polynomial curves which means its first increased and then decreased with the heating temperature, and there is a peak. But overall, the loss of key aroma components is small during the scraper film evaporator concentrating orange juice, as it only lost up to5.7%.