The source of MCP was Ethyblock
®
(Floralife,
Burr Ridge, IL), a powder which releases MCP
gas at the rate of 1.83mll
1
in a 1000-l chamber
when1gisdissolved in 20 ml of 2% potassium
hydroxide solution (Floralife, Ethyblock product
specification sheet). The ability of the supplied
material to release the stated amount of MCP was
confirmed by analysing the gas in a sealed cham-ber 30 min after the reaction was initiated. The
method used was described by Sisler and Serek
(1997) and utilised flame ionization gas chro-matography with an n-octane:porasil C column
and the peak response was calibrated against 1-butene. A treatment unit of four florets (100 g)
was placed at 20 or 5°C in a 10-l plastic container
together with the required weight of Ethyblock
®
in a glass beaker into which 2% potassium hy-droxide solution (20 ml) was added, and the con-tainer immediately sealed for 1 – 6 h. A control
unit was treated in a similar manner but without
the addition of MCP. After treatment, the broc-coli was stored at 20 or 5°C in 4-l containers
which were flushed with humidified air containing
0.1 mll1
ethylene at a flow rate of 20 l h
1
.
Storage in the ethylene atmosphere was used to simulate a probable commercial environment. A
randomised block design was used for experi-ments with three replicates in each treatment.