Effect of Roasting Temperature and Time on Precursors, Volatile Components and Flavour Quality of Cocoa Beans During Nib Roasting
The effect of roasting temperature and time on precursors, volatile components and quality of cocoa beans during nib roasting was studied using response surface methodology (RSM) which consisted two independent variables of temperature (110-170˚C) and time (5-65 min). Steam Distillation Extraction...
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| Format: | Thesis |
| Language: | English English |
| Published: |
1997
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/8379/1/FSMB_1997_8_A.pdf |
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| Summary: | The effect of roasting temperature and time on precursors, volatile components
and quality of cocoa beans during nib roasting was studied using response surface
methodology (RSM) which consisted two independent variables of temperature (110-170˚C) and time (5-65 min). Steam Distillation Extraction (SDE) method was used to
extract and gas chromatograph-mass spectrometry equipped with an ICIS data system
was used to identity the volatile compounds. The pH linearly increased during roasting
period at 120˚C. The colour was used for 1.20-1.80 Fermentation index value. The
moisture content of the nib decreased (to 1.1%) as the roasting time and temperature
were increased. Fifty three volatile compounds had been detected in roasted nib.
Among them, pyrazines and esters were two major groups which constituted of 34 different compounds. Tetramethylpyrazine, trimethylpyrazine, phenethyl acetate,
isoamyl acetate, 3-methylbutyl acetate, 2-methylbutyl acetate, phenylacetaldehyde, and
benzaldehyde were present in all treatments. The pyrazines formation increased as
roasting time and temperature were increased. When roasting time was increased from
5 to 35 and 65 min at 140°C, the number of pyrazines increased from 4 to 10 and 11,
respectively. The ratio value of esters increased when the roasting time was increased
from 15 to 65 min (at 110-120°C). However, the ratio value of carbonyls linearly
decreased with an increasing roasting temperature at shorter time (5-25 min). The ratio
value of phenols was enormously reduced at the highest roasting temperature (170°C)
with the longest roasting time (65 min) while that of alcohols slightly decreased as
roasting temperature and time were increased. With the increase in roasting
temperature and time, the concentration of free amino acids, reducing and non-reducing
sugars had decreased. The concentration of total free amino acids decreased
by 23.0% and 73.3% in the range of 1287.34 - 76.43 mg/100g. Sugars concentration
decreased from 24.87 to 12.98 and 11.30 mg/l00g respectively as roasting
temperature was increased from 110 to 140 and 170°C. The nib roasted at 140°C had
higher response percent of cocoa taste, moderate response of bitter taste and low
response of sour; astringent and absent of smoky. However, the nib roasted at 170°C
had the lowest percent of cocoa taste but higher in bitter and high roast taste. |
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