| Author | Sarinprapa Klinsrisuk |
| Note | A thesis submitted in partial fulfillment of the requirements for the
degree of Master of Science in
Food Engineering and Bioprocess Technology, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | Herbal tea production consists of two processing, namely; pretreatment and drying
herbal plants. The aim of this work is to study the effect of different blanching
pretreatments and drying conditions on qualities of dried drumstick leaves and its infusion.
Three blanching methods, namely; hot water, steam and microwave pretreatment varying
blanching times were treated in drumstick leaves prior to drying. Microwave blanching at
600W for 30 sec was effectively drumstick leaves blanching from the results in the
efficiency on peroxidase enzyme inactivation and preserving the amount of total
chlorophyll content and color when compared to water and steam blanching.
In drying process, four drying methods (hot air drying, vacuum drying, microwave
drying and freeze drying) varying drying temperature (50, 60, 70 and 80°C) or microwave
power level (180, 450, 600 and 850Watt) were investigated. The result of drying
characteristics is distinctly that microwave method could reduce drying time by more than
80% of hot air, vacuum and freeze drying. Two mathematical models which are Simple
Exponential equation (Lewis’s model), and General Page equation (Page’s model) were
built up to describe the behavior of drumstick leaves dryings. Page’s equation was
appropriate for predicting the drying behavior of drumstick leaves which had higher values
of R2 and lower values of root mean square (RMSE) and reducing chi-square (χ2) than
Lewis’s equation in three drying methods (hot air, vacuum and microwave drying). The
value of kinetic constant (k) was increased linearity by the increasing in drying
temperature and microwave power level.
The physical properties which are color and rehydration ratio of dried drumstick
leaves were examined. The increase of drying temperature and microwave power resulted
in inferior color quality except in vacuum dried samples. Oppositely, the effect of higher
drying temperature and power level gained in better rehydration characteristics of dried
leaves. In case of nutritional compositions (protein and minerals), high drying temperature
and microwave power caused in degradation of protein and minerals excluding Calcium
and Iron level. Antioxidant characteristics of dried drumstick powder and its infusion were
investigated using the Folin-Ciocalteu method for total phenolic content, Aluminium
Chloride Colorimetric for total flavonoid and flavonol content and DPPH radical
scavenging activity assay. The results indicated that bioactive substances and antioxidant
activity were degraded with the increasing drying temperature and power level.
Furthermore, the effect of duration time also affected considerably on total flavonol
content.
In conclusion, consideration on all performance qualities of dried drumstick leaves
and its infusion, microwave drying at 180Watt was the most appropriate drying of
drumstick leaves and drumstick herbal tea production. Drying time was only 9 min and
high qualities in appearance, nutritional values, antioxidant potential and sensory
acceptability. |
| Year | 2009 |
| 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 | Food Engineering and Bioprocess Technology (FB) |
| Chairperson(s) | Athapol Noomhorm; |
| Examination Committee(s) | Rakshit, Sudip K. ;Anal, Anil Kumar; |
| Scholarship Donor(s) | Royal Thai Government Fellowship; |