3 Storage and Detoxification of Bivalve Molluscs as a Tool in a Marketing Strategy
29
lysates. Each shellfish sample was acidified at pH <3.5 with 5 N HCl solution to
stabilize the toxins. The analysis was then performed by LC/FLD, according to the
method developed by Diener et al. (2006). A. minutum toxin content was estimated
by the Oshima HPLC method (1995). Contrary to the method commonly used to
quantify PSPs, the Diener method measures GTX and STX in a single step. Toxins
were separated on a Gemini reversed phase C18 chromatographic column 5 m,
(250 4.6 mm) at 20
ı C. For each test solution, three samples were injected three
times to determine each toxin concentration and the associated variation coefficients
during each experiment.
For DSP toxins, homogenized mussel digestive glands (2 g aliquots) were
extracted with 8 ml of a 95/5 methanol/water solution. Then, the extract (1 ml
aliquot) was tested by alkaline hydrolysis for the detection of okadaic acid (OA)
derivatives (diol- or fatty acid-esters). The hydrolysed extract was ultra-filtered
on an 0.2 m membrane and 5 l of the filtrate was injected on a Hypersil
MOS C8 column (50 2 mm 3 m) and analysed by a triple quadripole
mass spectrometer (API 2000, MRM positive ion mode). OA concentrations were
quantified by comparing the response obtained with a calibration curve based on
OA reference solution (IBM/NRC, Halifax, Canada).Toxin quantification in mussels
exposed to H 2 O 2 detoxification was applied daily in triplicate: digestive gland
samples were stored in liquid nitrogen until the end of the experiment. Later,
they were thawed, ground, extracted with acetone and then analyzed by LC-ESIMS/MS (Ion Trap, Finnigan LCQ). DTXs were quantified according to a procedure
described by Mondeguer et al. (2010).
Economic Analysis
The first objective was to develop a methodology capable of assessing the financial
losses that toxic algae cause to the shellfish industry. Since the aim of the newly
devised methods was to minimize these losses, the benefit they offer needs to be
compared with the investment and running costs of them in a cost-benefit analysis.
It was considered that in the case of a harvesting closure in a bay, sales would
be delayed, thus causing the usual markets to be lost. This scenario means that
shellfish would have to be sold on the wholesale market instead. Thus, the financial
loss per kg is the gap between the expected retail price and the actual wholesale
price.
As a consequence the total financial loss L is determined as follows:
L D .Pr Pw/Q
d
(3.2)
where Pr is the expected price (usually the retail price), Pw the wholesale price,
Q the daily sales in kg and d the number of days of closure.
Our case study was the oyster farming industry in Bourgneuf Bay (French
Atlantic coast). On the basis of a field survey, three groups of farmers were defined
29
lysates. Each shellfish sample was acidified at pH <3.5 with 5 N HCl solution to
stabilize the toxins. The analysis was then performed by LC/FLD, according to the
method developed by Diener et al. (2006). A. minutum toxin content was estimated
by the Oshima HPLC method (1995). Contrary to the method commonly used to
quantify PSPs, the Diener method measures GTX and STX in a single step. Toxins
were separated on a Gemini reversed phase C18 chromatographic column 5 m,
(250 4.6 mm) at 20
ı C. For each test solution, three samples were injected three
times to determine each toxin concentration and the associated variation coefficients
during each experiment.
For DSP toxins, homogenized mussel digestive glands (2 g aliquots) were
extracted with 8 ml of a 95/5 methanol/water solution. Then, the extract (1 ml
aliquot) was tested by alkaline hydrolysis for the detection of okadaic acid (OA)
derivatives (diol- or fatty acid-esters). The hydrolysed extract was ultra-filtered
on an 0.2 m membrane and 5 l of the filtrate was injected on a Hypersil
MOS C8 column (50 2 mm 3 m) and analysed by a triple quadripole
mass spectrometer (API 2000, MRM positive ion mode). OA concentrations were
quantified by comparing the response obtained with a calibration curve based on
OA reference solution (IBM/NRC, Halifax, Canada).Toxin quantification in mussels
exposed to H 2 O 2 detoxification was applied daily in triplicate: digestive gland
samples were stored in liquid nitrogen until the end of the experiment. Later,
they were thawed, ground, extracted with acetone and then analyzed by LC-ESIMS/MS (Ion Trap, Finnigan LCQ). DTXs were quantified according to a procedure
described by Mondeguer et al. (2010).
Economic Analysis
The first objective was to develop a methodology capable of assessing the financial
losses that toxic algae cause to the shellfish industry. Since the aim of the newly
devised methods was to minimize these losses, the benefit they offer needs to be
compared with the investment and running costs of them in a cost-benefit analysis.
It was considered that in the case of a harvesting closure in a bay, sales would
be delayed, thus causing the usual markets to be lost. This scenario means that
shellfish would have to be sold on the wholesale market instead. Thus, the financial
loss per kg is the gap between the expected retail price and the actual wholesale
price.
As a consequence the total financial loss L is determined as follows:
L D .Pr Pw/Q
d
(3.2)
where Pr is the expected price (usually the retail price), Pw the wholesale price,
Q the daily sales in kg and d the number of days of closure.
Our case study was the oyster farming industry in Bourgneuf Bay (French
Atlantic coast). On the basis of a field survey, three groups of farmers were defined