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African Journal of Biotechnology

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Changes in the quality of zobo beverages produced from Hibiscus sabdarifa (Linn roscelle) and the effects of extract of ginger alone or in combination with refrigeration

IS Ogiehor, OE Nwafor, UB Owhe-Ureghe

Abstract


Quality changes in zobo beverage produced from Hibiscus sabdarifa during storage and the effects of extracts of ginger (Zingiber officinale) alone or in combination with refrigeration at 6C were evaluated
for six (6) weeks duration. Results shows that the total viable bacterial count increased from 0.9 ± 0.01 log10 cfu/ml to 8.42 ± 0.1 Log10 cfu/ml at the 9th day of storage and thereafter decrease steadily till the
end of the storage period (21) days. While the total viable fungi count increased steadily from no growth after boiling and filtration to 6.14 ± 0.1 log10 cfu/ml at the 14th day of storage and thereafter decrease
steadily till the end of the storage period. Treatment with 0.2% extract of ginger at ambient laboratory temperature (30.5 ± 2C) retarded the total viable bacterial and fungi count for 10 days with minimal
growth from the 14th day which increase sluggishly. However treatment with 0.2% extract of ginger and refrigeration at 6C further retarded the total viable bacteria and fungi count for 21 days with
insignificant growth from the 28th day which was not sustained. The pH decreased gradually from 5.10 ±0.01 to 2.98 ± 0.00 while the titratable acidity (TA) increased from 0.021 to 0.060 during storage for 21
days. Slight changes were observed in samples treated with 0.2% extract of ginger whereas the pH and TA were fairly stable in samples treated with 0.2% extract of ginger refrigerated at 6C for 42 days.
Gradual increase was recorded in the total soluble solids (TSS), vitamin C, protein and carbohydrate contents up to the 6th and 9th day of storage and thereafter decreased sharply till the end of the storage
period for freshly prepared samples. However minimal changes were noted and recorded in samples treated with 0.2% extract of ginger all through the storage period. Whereas, sample treated with 0.2%
extract of ginger and refrigerated at 6C were fairly stable for 42 days of storage. Overall sensory evaluation shows that acceptability was in the order 0.2% ginger extract + 6C > 0.2% extract of ginger >
freshly prepared samples.



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