Different charcoal components, especially the volatile
matter, may form different PAHs during grilling
(Olsson & Petersson 2003), and these PAHs may
directly deposit onto the surface of the food (Chen &
Lin 1997). Therefore, in this study, charcoals with
different compositions were produced at different carbonisation
temperatures. The charcoal was then burnt
in a furnace at 650°C to determine the PAH content of
the smoke generated.
Mangrove charcoal was produced at carbonisation
temperatures of 500, 750 and 1000°C. The charcoal
compositions were analysed in terms of moisture content,
volatile matter, ash, fixed carbon and yield, as
shown in Table 2. The carbonisation temperature significantly
affected the charcoal composition and yield.
Charcoal produced at 500°C presented the highest 18%
volatile matter content and fixed carbon content (77%).
In contrast, charcoal produced at 750 and 1000°C presented
about 7% volatile matter and 80% fixed carbon
content. In addition, no significant differences in the
composition of charcoal produced at 750 and 1000°Cwere observed. These results indicated that higher carbonisation
temperatures purify the charcoal, resulting
in a lower volatile matter content and a lower yield.
These results showed the same trend as reported
by others (Demirbas 1999): that different charcoal
compositions were obtained from hazelnut shells carbonised
at different temperatures. At a high carbonisation
temperature (777°C), the charcoal derived from
hazelnut shell was purer and had a lower volatile matter
content, a higher fixed carbon content and a high
heating value.
Normally, pyrolysis of wood biomass, i.e., cellulose
and hemicelluloses, is achieved at temperatures around
400°C. Tar, a residue formed in charcoal production, is
in the form of a liquid at RT and becomes volatile at
high temperature, typically above 850°C (Antal et al.
1996). Thus, carbonisation temperatures of 750 and
1000°C leads to a decrease in the volatile matter content
of the charcoal.
As volatile matter in charcoal may form PAHs in
smoke generated during grilling, leading in a contamination
of grilled food with PAHs (Olsson & Petersson
2003), this study suggested producing charcoal at high
carbonisation temperature in order to lower a risk of
PAH contamination of grilled food. However, using a
high carbonisation temperature results in a higher cost
of charcoal production and a lower yield of charcoal
compared with a low carbonisation temperature; this
impact should be taken into account