Study On The Quality And Physical Characters Of Concentrated Pineapple Juice

The manufacture and physical characteristic of concentrated pineapple juice made of Hanna pineapple were researched in this paper. The physical character studied included rheological properties, the changes of volatile composition and content of aroma, the relation between the color and sensory evaluation, and the kinetics model of color was established for predicting the storage life of concentrated pineapple juice.The optimum process condition was vacuum 0.1 MPa, concentrated temperature 55℃,obtained by the analysis of essential composition, sensory evaluation and the volatile composition and content of aroma.Pineapple juices of low concentration(12.24,36°Brix )behaved as Newtonian flow, whose equation was y=kx, and 48°Brix, 60°Brix juices both were non-Newtonian flow, whose equation was s=s₀+k(e)ⁿ. 48°Brix concentrated juice was the Binghan flow. 60°Brix juice was the pseudoplastic flow. The effect of temperature on the viscosity could be described by Arrhenius equation: η=K₀exp(Ea/RT), The effect of soluble solid content could be described by exponential function: η=Kexp(AC), The combined effect of concentration and temperature on the viscosity could be described by η=3.2597 ×10^-4 exp(2.3981× 10⁴/RT-0.0575C+0.0024 C²).The changes of aroma composition and content of pineapple juice under different conditions were identified by GC-MS. The results were as follows: the analysis of pineapple juice with different pulp contents told that ester was the most primary component, and there was little diversity in the volatile components and contents. With the concentrated temperature increased, the contents of 60% aroma component decreased. The contents of furfural and 5-(Hydroxymethyl)-2-furfural. increased by 25%.The original aroma components minished with the process of concentration. The pineapple scent became thin. When reached the certain concentration, the main body odor of pineapple juice consisted of manifold...