Physical and chemical properties of pineapple juice, agglomerate and drink

S.Y. Lee

Abstract

Pineapple juice can be converted to powder or agglomerate by the process of fluidized bed drying and agglomeration. Ground sugar was used as a carrier while other essential minor additives i.e. anhydrous citric acid, pineapple flavour and permitted food colour, were used to boost up flavour, sugar-acid balance and eye appeal of the product. Optimum process variable used were 40 °C as the process temperature, 20 m3/ha as the volumetric airflow rate which resulted in an air velocity of 1.5 m/s, an atomization pressure of 3 bar and a pump flow rate of 6 g/min. Fresh pineapple juice was used as a binder for the agglomeration process in the fluidized bed dryer which was sprayed at the beginning of the drying process. The juice recovery was 43.82% and the fruit moisture content was relatively high at 88.36%. The strained juice was light yellow with colour value of L* = 44.44, a* = 1.14, b* = 25.43, total titratable acidity (TTA) = 0.47%, pH = 3.75, total soluble solids (TSS) = 9.5 and viscosity = 2.55 cP. Particle size distribution of the agglomerate showed that less than 10% of the particles were retained on the larger mesh no. i.e. mesh nos. 20, 30, 40 and 45. About 15% of the particle size was between 250–300 μm and 45% of the particles were finer than 250 μm. The colour of the pineapple agglomerate was L* = 90.57, a* = –0.51, b* = 25.93, the bulk density was 0.67 g/ml and the moisture content was 3.1%. The pineapple drink was compared to the fresh pineapple juice which had colour values of L* = 64.62, a* = 0.53, b* = 25.90, the TTA was 0.40%, the pH was 2.88 and the TSS was 9.0. The viscosity was slightly more viscous than the juice at 2.77 cP. Results of sensory evaluation showed that there were no significant differences in the colour, flavour, sweetness, sourness and overall acceptability of the drink and the juice. However, all the attributes had higher scores given to the juice except for the overall acceptability which was given the same score for both the drink and juice. The chemical analysis of the pineapple agglomerate showed that the total sugar content, total carbohydrate content and energy values were high because sugar was used as the carrier. The values of the other elements were considered relatively low except for the potassium content for the pineapple agglomerate as compared to the orange flavoured drink powder which had high contents of calcium, sodium, potassium and vitamin C. This can be explained by the fact that fortification of the orange flavoured drink powder was added to boost up the values of these contents.

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