Food or edible material: processes – compositions – and products – Inhibiting chemical or physical change of food by contact... – Including step of packaging
Reexamination Certificate
1997-07-09
2001-01-09
Weier, Anthony J. (Department: 1761)
Food or edible material: processes, compositions, and products
Inhibiting chemical or physical change of food by contact...
Including step of packaging
C426S323000, C426S643000
Reexamination Certificate
active
06171626
ABSTRACT:
BACKGROUND OF THE INVENTION
Paralytic Shellfish Poisoning (PSP) has been known for centuries and it has been responsible for many deaths (Kao, 1966). The toxins responsible of PSP are tetrahydropurines that block sodium channels, resulting in respiratory and heart paralysis (Hall, 1982). At least 18 types of PSP toxins have been described (FIG.
1
), mainly from marine dinoflagellates and shellfish that feed on toxic algae. Attempts to isolate PSP toxins began more than one century ago (Salkowski, 1885), but their occurrence as mixtures of compounds with diverse ionizable residues complicated their purification. The development of ionic exchange chromatography, guided by mouse bioassay, eventually allowed the isolation of a basic toxin, water soluble, from Alaska clams (
Saxidomas giganteus
) (Schantz et al., 1957). This compound was named saxitoxin (STX) and therefore the group of paralytic toxins, saxitoxins (Schuett and Rapoport, 1962). The STX structure is shown in FIG.
1
and was established by X ray crystalography (Schantz et al., 1975) and chemical synthesis (Tan et al., 1977; Kishi, 1980; Jacobi et al., 1984; Martinelli et al., 1986).
In most cases, PSP toxins correspond to sulphatated derivatives of STX, such as the 11-hydroxysaxitoxin sulphates (gonyautoxins GTX2 and GTX3) or N-sulphocarbamoyl derivatives (B1, C1 and C2). It is possible to find also the N-1-hydroxysaxitoxin or neosaxitoxin (NEO) and their sulphates (B2, GTX1, GTX4, C3 and C4), as well as the less common decarbamoyl toxins (
FIG. 1
) (Sullivan et al., 1983). The STXs potencies, measured by mouse bioassay, vary enormously. Generally, the carbamoyl toxins are the most potent, the sulphocarbamoyl toxins are the less potent, and the decarbamoyl toxins have intermediate potency (Oshima et al., 1992).
Shellfish acquire and concentrate the STXs as a result of feeding with toxic dinoflagellates. Several species of dinoflagellates have been associated with paralytic toxins, including
Alexandrium catenella
(Schantz et al., 1966; Proktor et al., 1975; Bates et al., 1978),
A. excavatum
(Desbiens et al., 1990),
A. fundyense
(Anderson et al., 1990) and
A. tamarensis
(Prakash, 1967; Anderson and Po-on Cheng, 1988) in the northern latitudes, and in the southern latitudes,
Gymnodinium catenatum, Pyrodinium bahamense
(Taylor, 1985; Anderson et al., 1989) and
Gonyaulax polyedra
(Bruno et al., 1990). The dinoflagellate cysts, deposited in marine sediments, can remain toxic for several months (Selvin et al., 1984). The composition of paralytic toxins varies enormously depending on the dinoflagellate specie from which they were isolated (Boyer et al., 1985; Cembella et al., 1987). Also there are intra-specie variations (Maranda et al., 1985; Cembella et al., 1987). However, toxin composition of a certain dinoflagellate strain, isolated from a particular geographical zone, is extremely constant.
Shellfish produces important changes in the paralytic toxin profile. Due to the differences in toxin potencies, a shellfish can change drastically its total toxicity without modifying the total quantity of toxin (Oshima et al., 1990). Other changes in the toxin profile can occur due to non enzymatic processes. Without exception, the gonyautoxins suffer epimerization, with the equilibrium displaced to the alpha forms, that are energetically more favourable (Fix Wichmann et al., 1981; Hall, 1982). The conversion speed is dependant on the pH and chemical structure, with a faster epimerization near to neutral pH. All paralytic toxins are quickly oxidized to non toxic products if the pH is not controlled during their extraction. Conditions of neutral and alkaline pH favour the oxidation. Under extremely acidic pHs (1M of free acid) carbamoyl groups are removed, while at pH 1 and 100° C. the lost group corresponds to the sulphate (sulphocarbamoyl) of the sulphocarbamoyl toxins, with a complete conversion in 5 min (Hall and Reichardt, 1984). Due to the low toxicity of the sulphocarbamoyl toxins and to the high toxicity of the carbamoyl toxins, the loss of the sulphate group produces an increase in the total toxicity.
Although it is possible to predict the time of the year, and in some parts of the world, the exact localization of the PSP proliferation, the toxicity vary enormously from year to year. Therefore, monitoring programs are absolutely necessary in order to protect the shellfish industry and the consumer. The mouse bioassay has been a standard method for PSP toxins detection and quantification for more than 50 years (Sommer and Meyer, 1937; McFarren, 1958; Helrich, 1990). Due to the use of experimental animals, the variability of the results and because the sensitivity of the mouse bioassay is very close to the regulatory limits, attempts have been made to replace this method with other methods, for example, toxin detection by HPLC. However, the mouse bioassay is simple and quick. On the other hand, this method is a direct measurement of toxicity, which is an important consideration for the security of the shellfish, particularly because of the discovery of new toxins. The HPLC method is based on a chromatographic ion pairing-separation of toxins in a RP8 column. Subsequently, through a post column derivatization, toxins are alkaline oxidated and then fluorometrically detected (Sullivan et al., 1988; Oshima et al., 1988).
The occurrence of intoxication due to paralytic toxin has increased consistently throughout the world in the past years. Until 1970, some 1700 cases of PSP have been registered, mainly in North America and Europe (Prakash et al., 1971). On the other hand, in the period 1971-1984 around 900 additional cases have been described, especially in zones of the world where PSP was practically unknown (WHO 1984). In China, PSP appeared at the beginning of the 1950s, in Japan and Norway at the end of the 1960s, in Malaysia, The Philippines, New Guinea, Australia, Indonesia, Argentina and Chile at the end of the 1970s and the beginning of the 1980s, in Sweden, Denmark, Guatemala, Venezuela, Mexico and Uruguay at the end of the 1980s and the beginning of the 1990s. Actually large parts of the world-wide coasts have or had recurrent proliferation of the PSP producer algae. This has generated a growing problem in Public Health, especially concerning the prevention of intoxication in human beings. With the continual increase in the world-wide areas that are contaminated with PSP producer algae, the areas designated for shellfish collection and cultivation are becoming more limited. This has caused a reduction in production in many areas, with a consequent socioeconomic impact of the involved fishermen. This situation is driving the need to evaluate seriously how to utilize PSP contaminated shellfish.
One alternative is to use PSP-containing shellfish detoxified to levels that are not toxic to human beings. The maximal level of PSP accepted on a world-wide basis as being safe for shellfish was 80 &mgr;g of equivalent STX for each 100 g of mollusc flesh
Shellfish PSP detoxification data found in the literature are scarce and non systematic. The proposed shellfish detoxification processes can be grouped in 4 classes of strategies:
1.—Detoxification of live shellfish.
2.—Chemical treatment.
3.—Removal of the more toxic parts.
4.—Processing.
1.—Detoxification of live shellfish
This can be done by transplanting the toxic shellfish to a non toxic area. In this circumstance the shellfish suffer detoxification by depuration unless re-toxification occurs. Actually detailed information is known only about the detoxification kinetic of 3 species of scallops:
Patinopecten yessoensis, Placopecten magellanicus,
and
Chlamys nipponensis
(Medcof et al., 1947; Jamieson and Chandler, 1983; Shumway et al., 1988). The facts now available suggest that within the filter-feeding bivalve molluscs, scallops can be classified as species that retain the toxins for a long time. For example, the retention of paralytic toxins in
P. magellanicus
has been identified for periods that run from several months to 2 years (Medcof et al., 1947; Ja
Blamey Jenny
Chiong Mario
Hinrichsen Juan Pablo
Lagos Nestor
Lopez Claudia
Lackenbach Siegel Marzullo Aronson & Greenspan P.C.
Tepual S.A.
Weier Anthony J.
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