Performance of UVC irradiation with dean vortex technology on clear and turbid tamarind (Tamarindus indica l.) juice
Tamarind juice is commonly treated by thermal treatment to inactivate microorganisms. However, thermal treatment causes changes in appearance and taste of tamarind juice. Ultraviolet (UV) irradiation has emerged as an alternative to thermal processing. Nonetheless, the application of UV irradiati...
Saved in:
| Main Author: | |
|---|---|
| Format: | Thesis |
| Language: | English |
| Published: |
2016
|
| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/67108/1/FK%202016%20168%20UPMIR.pdf |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | Tamarind juice is commonly treated by thermal treatment to inactivate
microorganisms. However, thermal treatment causes changes in appearance and
taste of tamarind juice. Ultraviolet (UV) irradiation has emerged as an alternative
to thermal processing. Nonetheless, the application of UV irradiation on tamarind
juice is not sited in the literature. In addition, the implementation of UV system with
Dean Vortex technology are still limited. Therefore, the present study was aimed
to investigate the performance of UVC irradiation on the quality and microbial
reduction of clear and turbid tamarind juice. Results of microbiological analyses
showed that UVC dosage of 35 mJ/cm2 was found effective in reducing microbial
load to a 5-log reduction. The survival curves of viable bacteria (Escherichia coli
and native microflora) were best-fitted with the log linear with tailing model (R2
=0.999). UVC treatment significantly reduced the total soluble solids of tamarind
juice by 18-21% (p<0.05) but successfully retains the pH, titratable acidity and
colour of tamarind juices (p>0.05). Differences in turbidity were significant in UVCtreated
clear tamarind juice as UVC dosage increases. Dean Vortex technology
was able to reduce the influence of turbidity in UV treatment. In comparison to
thermal treatment, the inactivation of microbes by UVC treatment were not as
efficient. Thermally treated juice exerted a good resemblance to UVC-irradiated
juice in terms of pH, titratable acidity and colour. It also retained the total soluble
solids of tamarind juice better than UVC-irradiated juice. Nonetheless, the
differences in turbidity were significant (p<0.05) after thermal treatment especially
in clear tamarind juice. During seven weeks of storage, the pH of tamarind juices
had changed significantly (p<0.05). Total soluble solids had increased (p<0.05) in
clear tamarind juice after storage period. The titratable acidity of thermally-treated
clear tamarind juice had increased from 0.43% to 0.48% (p<0.05) whereas the
titratable acidity of UVC-irradiated turbid tamarind juice decreased from 0.40% to
0.30% (p<0.05). In terms of turbidity, UVC-treated juices showed the lowest
turbidity values compared to fresh and thermally-pasteurised juice after seven
weeks. On the other hand, there were no effects of different treatments on the
lightness, hue angles and chroma after seven weeks of storage. UVC-treated juice exerted the lowest overall changed in colour throughout seven weeks of storage.
From microbial analysis, UVC-treated juice showed good stability of viable
bacteria during storage. Nonetheless, tamarind juice was spoiled due to outgrowth
of yeast and mould after two weeks. Contradictory, thermal treatments
successfully retained microbial loads to below detection level during refrigerated
storage. In conclusion, the existing UVC treatment may not be a suitable
alternative in replacing thermal pasteurisation especially for long-term storage. |
|---|