CHAPTER 5 CONCLUSIONS AND RECOMMENDATION 5.1 CONCLUSIONS
Primarily, the feasibility study of tamarind powder production was carried out, using a two fluid-nozzle atomizer. In this study, the mass flow rate of the liquid feed and the air-to-liquid feed mass ratio were fixed at 1.016 kg/h, and 7.084, respectively. The operating conditions, i.e. the inlet air-temperature, type and concentration of drying aids were studied for their effects on the product qualities, and then the suitable condition was proposed. Two types of drying aids were used, namely Flomax 8®, and maltodextrin (DE10). The qualities of the product powder used as the criteria were moisture content, bulk density, hygroscropicity, degree of caking and solubility in term of reconstitution time. The qualities of the reconstituted tamarind paste were also measured for total color change, acidity, and rheology parameters, and compared with the fresh paste. The following results showed the effects of the operating parameters on the product qualities.
Moisture content was significantly affected by inlet air temperature and concentration of drying aids, but not by the types of drying aids. An increase in the inlet air-temperature and drying aids led to a reduction of moisture in the powder. It was also found that only concentration of the drying aids had significantly influence on the hygroscopicity (HG) of the powder. Another quality indicating the stability of the powder product is the degree of caking (DC), which was significantly effected by three operating variables.
That is, the HG and DC values could be reduced by adding more drying aids. Conversely, an increase in the temperature of hot air resulted in an increase in the DC value as a result of high porosity.
It was observed that the particle sizes reduced with an increase concentration of both drying aids on account of their functionality of reduction the surface tension. In addition, the high temperature of hot air resulted in large particle size probably due to melting of droplets being dried. However, the amount of drying aids showed the dominating effect on the particle size rather than the temperature of hot air. Moreover, the bulk density, which is a combination effect of particle size and moisture, was affected by the temperature of hot air as well as the concentration of drying aids, but not by the type of drying aids.
Solubility as reconstitution time of powder depended on the inlet air-temperature, type and concentration of drying aids. The powder made from maltodextrin could be dissolved in water easier than the product made from Flomax 8®. However, the consistency of reconstituted pasted obtained from Flowmax 8® was higher that of maltodextrin. Based on the Power law model, adding the drying aids trended to increase the flow behavior index of the paste from 0.774 for the fresh paste to 0.875-0.994 for the reconstituted paste.
Compared with the fresh tamarind paste, acidity and the color change (ΔE value) were influenced by three operating parameters. An increase temperature of hot air and a reduction in the amount of the drying aids resulted in an increase in ΔE value. On the other words, the amount of drying aids dilutes the solution to reduce the browning effect of the product undergone high temperature of drying. It was also found that the acidity increased with an increase temperature of the hot air and a reduction in the drying aids.
To mainly comply with Thai industry standard product (TISI), that is the moisture content of dried products shall not be greater than 7% (d.b.), the suitable condition of producing tamarind powder at 130oC of the inlet air-temperature with 0.50 kg drying aids/ kg total solids was chosen with the consideration of other properties, i.e. degree of caking, hygroscopicity, and ΔE value in order to achieve the reconstituted paste similar to the fresh paste prior to drying. Flomax 8® and Maltodextrin could be used as the drying aids for drying of the tamarind paste, depending on the consumer requirement. Maltodextrin gave the powder that was easy to dissolve, whereas Flomax 8® gave the reconstituted paste with high consistency index.
5.2 RECOMMENDATION
To reduce agglomeration of the product powder, the secondary drying using fluidized bed should be further studied. To reduce the degree of caking, the effect of anti-caking on improving the shelf life of the product powder should be studied.