Effects of thermal and non-thermal processing on quality attributes of chokanan mango juice (Mangifera Indica L.) / Vicknesha a/p Santhirasegaram
The increasing demand for high quality fruit juice, along with safety standards have spurred the development of non-thermal processing such as sonication and ultraviolet-c (UV-C) light treatment. In this study, freshly squeezed Chokanan mango juice was subjected to thermal treatment (at 90 °C for...
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| Format: | Thesis |
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2015
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| Online Access: | http://studentsrepo.um.edu.my/6504/ http://studentsrepo.um.edu.my/6504/1/Vicknesha_Santhirasegaram%2DThesis_Final.pdf |
| Summary: | The increasing demand for high quality fruit juice, along with safety standards have
spurred the development of non-thermal processing such as sonication and ultraviolet-c
(UV-C) light treatment. In this study, freshly squeezed Chokanan mango juice was
subjected to thermal treatment (at 90 °C for 30 and 60 seconds), sonication (for 15, 30
and 60 minutes at 25 °C, 40 kHz frequency) and UV-C treatment (for 15, 30 and 60
minutes at 25 °C, 254 nm). In addition, combination of sonication (for 15 and 30
minutes at 25 °C, 40 kHz frequency) and UV-C treatment (for 15 and 30 minutes at 25
°C, 254 nm) in a hurdle concept was also conducted. The effects of thermal and nonthermal
treatments on various quality parameters (microbial inactivation,
physicochemical properties, colour, clarity, browning index, total carotenoid and
ascorbic acid content, antioxidant activities, sensory attributes) were evaluated and
compared with untreated juice (control).
After thermal and non-thermal treatments, no significant changes were observed in pH,
total soluble solids and titratable acidity. However, significant differences in colour,
browning index and ascorbic acid content of juice were observed after treatments
(thermal and non-thermal). Non-thermal treatments showed significant improvement in
selected quality parameters. Overall, sonication and UV-C treatment (as a stand-alone
and combined treatment) exhibited significant enhancement in clarity, antioxidant
activities, and extractability of carotenoids, polyphenols, and flavonoids, when
compared to the control. In addition, significant reduction in microbial load was
observed in non-thermal and thermal treatments. Although thermal treatment was
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effective in completely inactivating microbial growth in juice, significant quality loss
was observed.
The individual phenolic compounds in juice were identified and quantified using liquid
chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The results showed
better retention of individual phenolic compounds in non-thermal treated juice, when
compared to the control and thermally treated juice. Sensory attributes (colour, odour,
taste, and overall acceptability) were evaluated by 90 panellists using a hedonic scale,
and results showed that non-thermal treated juice was preferred more than thermally
treated juice. The sensory evaluation verified that the combination of sonication and
UV-C was the most acceptable treatment of the selected non-thermal treatments.
The shelf life of the thermally treated juice stored at 4 °C was extended for at least five
weeks longer than control. With regards to sonication and UV-C treatment (as a standalone),
the shelf life of juice stored at 4 °C was extended for at least four weeks longer
than control. Besides that, combined treatment prolonged the shelf life of juice stored at
4 °C for at least five weeks longer than control. The results obtained support the use of
non-thermal treatments (ultrasound and UV-C) for better retention of quality along with
safety standards in Chokanan mango juice processing. Combination of ultrasound and
UV-C therefore, is a promising alternative to thermal treatment. |
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