and canned in the Institute de
Investigacions Marinas.
Gutted ®sh were steam-cooked (102±103C) for 90
min, the temperature in the core of the ®sh being about
65C. After being cooked and then allowed to cool,
the ®sh were skinned and ®lleted. Light muscle from the
®llets was taken for ®lling RO-100 type cans (diameter:
6.52 cm, height: 3 cm), and 2 g of sodium chloride were
added. Oil was poured in to completely cover the ¯esh.
The cans were hermetically closed and then sterilised at
115C for 60 min.
As it was found more practical to distribute the ®sh
¯esh preserved in ethanol, instead of in cans, samples of
canned tuna muscle were processed as in the following
paragraphs.
At ®rst oil was removed by blotting the ¯esh with ®l-
ter paper, then lipids were extracted by incubating the
¯esh for 24 h in a mixture of chloroform/methanol/
water, 1/2/0.8 (v/v/v). To one part by weight of defatted
tuna muscle, two parts by volume of absolute ethanol
were added; after stirring for 2 h, the ethanol was dec-
anted and fresh ethanol was added. The ethanol was
then poured o and the muscle pieces were divided into
0.5 g portions and placed in cryogenic vials (2 ml). To
these 0.5 g portions of muscle, 1 ml volumes of ethanol
were applied. Samples were then sent to the participants
by ordinary (air) mail. Mixtures of tuna ¯esh from two
species were prepared by weighing equal amounts of
canned, defatted light muscle of each species, adding
ethanol and stirring the mixture for 30 min. Ethanol
was poured o and the mixed muscle was allowed to dry
before weighing it in vials. Fresh ethanol was then
added.
For each tuna species, reference material and sample
were from the same canned specimen.