[Stoves] LPG import in India

[Crispin Pemberton-Pigott]

Dear Andrew

Then perhaps I can contribute the following from our tests, first monitoring the maximum temperature reached in the smoker and second, the ‎results from the food quality lab in Accra which happened to be literally next door.

There is a clear relationship between the BaP level and the processing temperature. Given that most 'professional' smokers use 85 C as the processing temp, we kept ours to <105 and when doing so, the BaP was one part per billion, which is also the detection limit. The other three species demanded by the EU were undetectable (i.e. Less than 1 ppb).

When the temperature was allowed to rise to 115, 120, 130 and 140, even briefly, the contamination was significantly higher (many times, like 5, 8, 10).

To me this confirms the importance of temperature over fuel and 'smoke' (there was very little smoke - the term is used loosely, they were in fact dried).

It is important to mention that these were all downdrafting heated chambers which drops all oil from the fish onto the fish below or onto the sand bed at the bottom. At no time was ‎'dropped oil' anywhere near a fire. This is a big difference from the traditional smokers which have that oil dripping onto the side of the combustion chamber, the spreader, or the fire. In all cases like that, the BaP is very high (30).

So there were three elements of the success: downdrafting heating cupboard, with a chimney pulling it down, which requires a 'bleeder' to dump heat from the fire into the chimney, a temperature max of 105 at the top of the chamber, and a reasonably clean burning fire which in that case, was bbased on the grate and air supply of the Keren Super (not the Super 2 and not the Super Nova). It has a grate elevated at the back only with back air or side air. Both worked.

Regards
Crispin





On 29 December 2017 at 02:31, Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:
> Dear Andrew
>
> Re the Benzo(A)pyrene
>
> Do you recall that last year I was working with James Robinson at SNV in Ghana? We produced a fish smoker that reduced the BaP dramatically (97%) by changing the temperature of processing.

Yes I do remember your mention of it.

>
> It is in the meat. But is it in the vegetables? We demonstrated that it is produced by overheating the fish oil, and is not from the smoke. I think most foodie people believe it is from the wood. It seems to be almost entirely from the heating of the food.

I don't know the route to PAH and it might just be that the
triglycerides offer a better species source of PAH. I also don't know
why benzo[a]pyrene is selected as an indicator for PAHs in general,
there seems to be some debate as to whether it is the most noxious.
What seems beyond doubt is that is is formed as a product of
incomplete combustion (partial oxidation) of any organic compounds as
well as diesel or coal. It is also formed at above 400C and that is
the region where we see some interesting changes from aliphatic
(chainlike compounds like cellulose) to phenolic ones containing
complete carbon rings. If you look at the structure of cellulose you
will see it only needs the substitution of an oxygen atom by a carbon
one to complete a benzene ring. One of the ways graphite is formed is
to take an organic compound, form a shape and then heat it to
progressively to remove oxygen and hydrogen until at around 3000C all
the carbon atoms form carbon rings in a stack of graphene sheets.
>
> High oil fish dried traditionally or in the FAO promoted 'improved smokers' have very high BaP‎ and the non-oily fish do not. Same fuel.

It makes sense that it is the oil then, note also flame grilled meats
are high in PAHs.
>
> Has anyone measured BaP in smoke? Philip, maybe?

I don't have any means of measuring it but woodsmoke (maybe from
wildfires) is widely reported as a major source, presumably good
secondary combustion prevents their formation  but would cold smoking
do also?. We do know it's significance in sump oil and coal smoke as
it is implicated in two cancers which became early reported industrial
diseases, scrotum cancer in young chimney sweeps and young auto
mechanics.

Andrew

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