Effects of processing conditions on the quality of spray-dried coconut milk and skim milk | |
| Author | Douwes Dekker Malik |
| Call Number | AIT Diss. no.AE-95-03 |
| Subject(s) | Spray drying Coconut products |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Technical Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. AE-95-03 |
| Abstract | A study of the spray drying process of coconut milk and coconut skim milk was made to determine the experimental conditions necessary for production powders, and their influence on the power quality. The experimental laboratory-scale spray drying unit was specifically designed, constructed and tested for its performance. Experimental variable consisted to the conditions of the drying air and the use of additives in formulating the feed solution. Air absolute humidifies of about 0.0157 kg H2o/kg dry air and lower with inlet and outlet temperatures of about 126'c and 95'c for coconut milk, and 102'c and 90'c for coconut slim milk could be used successfully to produce spray-dried coconut milk (SCM) and spray-dried coconut skim milk (SCSM) powders. These conditions corresponded to the drying air velocity of about 0.2 and 0.3 m/s for SCM and SCSM, respectively, The formation of spray droplets was facilitated when the total solids in feed solution ranged approximately from 20 to 25% when using compressed air at a pressure of approximately 0.5 and 1 kg/cm2 with a corresponding feed flow rate of about 0.4 and 0.5 kg/h for SCM and SCSM, respectively. Under the above conditions, SCSM could be produced without the addition of maltodextrin, although maltodextrin improved the powder recovery. However, SCM could only be produced by using at least 40% maltodextrin of 10% sodium caseinate based on the total solids in the feed solution separately or their combination at reduced levels. When used in combination, the minimum levels of maltodextrin and sodium caseinate to produce SCM were determined to be 20% and 5% of the total solids present in the feed solution, respectively. The SCM and SCSM could attain equilibrium moisture contents (EMCs) only in a limited ranged of relative humidity upon exposure. These equilibrium relative humidity (ERH) limits were determined to be approximately 75% for SCM and 63% for SCSM and corresponded to the EMC limits of 10%d.b and 17.5%d.b, respectively, When exposed to relative humidifies (RHs) higher than ERHs, the appearance of SCM and SCSM sampled revealed their distinct transformation into a glassy or liquid-like product over a period of time. The model developed for estimating EMCs of SCM at exposure temperatures ranging from 30'c to 50'c accounted for the effects of RH, temperature, maltodextrin, and sodium caseinate, However, the EMC was determined to be the function only of RH and temperature in the case of the SCSM samples. In general, SCSM samples absorbed more moisture in comparison with SCM samples. In equilibrium conditions, the moisture adsorption characteristics of both SCM and SCSM samples could be represented adequately in the form of a modified logarithmic model. In non-equilibrium conditions where the sample moisture content continued to increase indefinitely, an alternative model represented the experimental data satisfactorily. Empirical relationships representing moisture adsorption characteristics of SCM and SCSM samples under equilibrium and non-equilibrium conditions showed good agreement between the estimated and experimental values of moisture contents, and thus indicated the suitability of the questions developed for general application. The use of additives (maltodextrin and sodium caseinate in the case of SCM and only maltodextrin in SCSM) in the feed solutions prior to spray drying affected the whiteness, solubility, and particle density of the spray-dried samples. The addition of maltodextrin in 0 to 50% range to produce SCM samples using 10% sodium caseinate improved the whiteness of the powder by about 26.8%. However, the addition of maltodextrin in producing SCSM samples showed only a slight improvement of about 6.3% in the whiteness. Both SCM and SCSM had high solubility in water with mean approximate values of about 93.2 and 95.9%, respectively, The addition of sodium caseinate appeared to improve the solubility of SCM. However, the addition of maltodextrin improved the solubility of SCSM slightly and showed no improvement in the case of SCM. In the case of SCSM, the addition of maltodextrin led to an increase in particle density. The electrical conductivity of reconstituted samples with solid concentration ranging from 5 to 25% varied from 1.2 to 5.5 mS/cm for SCM and from 4.3 to 15.4 mS/cm in the case of SCSM. The electric conductivity values increased with an increase in solids concentration and sodium caseinate levels. The electrical conductivity, however, was decreased for samples containing in creasing levels of maltodextrin. |
| Year | 1995 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. AE-95-03 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Food Engineering (AE) |
| Chairperson(s) | Jindal, V.K.; |
| Examination Committee(s) | Gupta, C.P.;Exell, R.H.B.;Athapol Noomgorm; |
| Scholarship Donor(s) | Eastern Indonesia Universities Development Project (EIUDP);CIDA; |
| Degree | Thesis (Ph. D.) - Asian Institute of Technology, 1995 |