| Author | Yu, Jian-ping |
| Call Number | AIT Thesis no. AE-98-10 |
| Subject(s) | Freeze-drying
|
| Note | A thesis submitted in partial fulfillment of the requirements
for the degree of Master of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | A laboratory scale freeze concentration machine was designed and developed to study two
processes of freeze concentration, batch process freeze concentration and progressive freeze
concentration (PFC). The main components of the machine consist of freezing unit and a
progressive device which can offer constant submerging speeds of 1.6, 2.1, 2.8 cm/h by
selecting suitable gears and stir sample at 200rpm up to near 2000rpm. Salt solution was
cooled by the freezing unit to act as freezing source.
Two kinds of salt were tested to study the possibility of using inorganic salt as coolant in
freeze concentration. Both sodium chloride and calcium chloride can be used in freeze
concentration. Equations for relationship between concentration and freezing point of the salts
were found. NaCl gave lower temperature than CaC12 did at same concentration. Costs of
CaCl2 were 21.0%, 13.1%and10.2% higher than NaCl at temperatures of -3, -6, and -1 0 °C.
The effect of process parameters, e.g. supercooling temperature, freezing time, agitation,
sample initial concentration, nucleation time, submerging speed on separation result were
studied. In both two processes, high initial concentration resulted in high loss in ice portion. In
batch process, lower temperature allow faster freezing but an optimal super-cooling
temperature appeared at -2.5 °C while the concentrating rate was 0.92 and loss was 2.14%.
Amount of nuclei acquired from 5 and 10 minutes nucleation of sample had little effect on
concentration results. More complete separation due to prolonging the freezing time but there
was a concentration limit due to sample solidification.
In PFC, loss can be dominated by increasing agitation (11 OOrpm), keeping suitable bath (-10°
C) temperature, and slow submerging (1 .6 cm/h). PFC was unsuitable for solution which
concentration was higher than 30%. Although the amount of loss had some difference, the
concentration of concentrates were same for sugar solution and pineapple juice of same initial
TSS suffered PFC. Empirical equations on concentration rate for both processes were derived.
Amounts of ascorbic acid retained in pineapple juice from various processes were quite
different from each other. It was 3.35 mg/lOO g in freeze concentrated juice which accounted
for 78% of fresh juice. Statistical analysis did not show significant difference in qualities of
freeze concentrated and vacuum evaporated juice at 5% level. |
| Year | 1998 |
| Type | Thesis |
| 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) | Athapol Noomhorm; |
| Examination Committee(s) | Jindal, V. K. ;Vincent, J. C.; |
| Scholarship Donor(s) | The Royal Government of Netherlands ; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1998 |