Peppers

It has always disappointed me as an inorganic chemist, that every first year student can tell you the formula and structure of salt, but not even at the postgraduate level will you find many students that have any idea at all about what is in pepper!

Bell Peppers

Bell peppers

A wealth of information is available from the Northern Carolina Cooperative Extension Service on growing commercial vegetables.
Leaflet 21 includes Bell peppers and pim(i)ento (the pepper).

A recent paper in J. Sci. Food Agric., 1995, 67, 189-196 by S.M. van Ruth, J.P. Roozen and J.L. Cozijnsen, describes flavour components in Bell peppers.
Out of 47 compounds identified, 12 could be detected by assessors at a sniffing port on a GC. A simulation of their GC is shown as a sensitive map GC/MS, and the MS files can be downloaded in JCAMP-DX format by selecting the appropriate box.

The 12 compounds were:

3 (2220) 2-Methylpropanal MS
9 2-Methylbutanal MS
10 3-Methylbutanal MS
13 (2370) 2,3-Butanedione
15 (3382) 1-Penten-3-one
19 (2557) Hexanal MS
25 (2540) Heptanal MOL
29 β-Ocimene MOL
35 trans-3-Hepten-2-one
39 Dimethyltrisulfide
45 (3132) 2-isobutyl-3-methoxypyrazine PDB
47 (3639) β-Cyclocitral MOL

other compounds found in reasonable quantities were:

14 (3098) Pentanal PDB
21 1-Methyl-1H-pyrrole MOL
23 (3584) 1-Penten-3-ol PDB
26 (2633) (R)-(+)-Limonene MS
36 cis-2-Heptenal MOL
40 (2782) Nonanal PDB
42 (2805) 1-Octen-3-ol PDB
44 (2362) Decanal PDB

The numbers on the left are the peak numbers identified in their GC, the numbers in brackets are the FEMA codes (Flavor and Extract Manufacturers' Association of the USA).

The structure of capsaicin, one of the chemicals giving the pungent flavour, is shown above.

The compound described as the character imparting compound in Bell peppers is 2-isobutyl-3-methoxypyrazine. This very powerful odourant has a threshold in water of 1 part in 10¹².

Hot peppers

Jamaica is well known for hot peppers such as "Scotch Bonnet". Work is in progress on establishing a hotness scale for these peppers and more on this later.

Hot peppers

GC of hot pepper -JCAMP-DX file

In the meantime, check out these links on spices and chiles, the chileheads project and the fire and spice page.

An article in Chem and Eng News, March 4, 1996, pps30-31, outlines the novel use of hot peppers as an additive to bird seed to make it unpalatable to squirrels. Apparently birds are not affected by the heat but the squirrels avoid the birdseed treated with sufficient pepper to give a 20,000 Scoville heat unit.

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Created and maintained by Prof. Robert J. Lancashire,
The Department of Chemistry, University of the West Indies,
Mona Campus, Kingston 7, Jamaica.

Created Feb 1995. Links checked and/or last modified 8th August 2014.
URL http://wwwchem.uwimona.edu.jm/lectures/pepper.html