2-11. DETERIORATIVE AND UNACCEPTABLE CONDITIONS--INTRODUCTION
a. General. Like fish, shellfish are highly perishable, and due to their filtering
mechanisms, unacceptable conditions may be present. As previously stated, mollusks
obtain their food and oxygen by forcing water across their gills. As plankton and other
microscopic organisms are trapped by the cilia, any undesirable organisms present may
be trapped, ingested, or retained in the gills, producing unacceptable or possibly toxic
conditions. In paragraphs 2-12 through 2-14, these conditions are discussed by
b. Shellfish Poisoning. Paralytic shellfish poisoning results from eating
mollusk that contains saxitoxin. Some shellfish growing areas are normally
contaminated with a microscopic plant named Gonyaulax catanella, from the order
Dinoflagellata. These small plants lay dormant until climatic conditions develop that
induce reproduction. Reproduction may reach levels that give the water a reddish cast,
referred to as the "red tide." The consumption of these plants by mollusk results in a
buildup of saxitoxin. This in turn produces paralytic shellfish poisoning in humans that
may result in illness or even death.
2-12. DETERIORATIVE AND UNACCEPTABLE CONDITIONS OF OYSTERS
a. Spawny Oysters. Spawny oysters can be identified by the presence of a
translucent, milky-colored material. When moderate pressure is applied to the body of a
shucked oyster, this fluid is released from within the oyster. The condition develops
when the water approaches 50o to 70o F (10o to 21o C) during late spring and early fall.
As the waters on the Pacific coast seldom reach 50o F, there is a tendency for spawning
to continue throughout the summer months. Since 2 to 5 percent of the Pacific coast
oysters are spawny by this definition, a tolerance of one spawny oyster per pint has
been established for each shipment of oysters.
b. Undernourished, Elongated Gills. Undernourished, elongated gills are a
condition that may develop in oysters after the heavy spawning periods and normally
occurs in late spring or early fall. The gills become thin, watery, and brownish in color.
The body is thin and somewhat brownish, not whitish, the color that would indicate a fat
oyster of high quality. There are many other factors that may produce this condition, for
example, salinity of the water, lack of food, and turbidity of the water.
c. Pink or Red Oysters. Pink or red color is a condition that develops in
oysters subsequent to shucking and packing (caused by poor plant sanitation). The
condition is normally caused by a yeast growth that can develop at temperatures as low
as 0oF. On frozen oysters, it appears as small pink or red pinpoint specks; however, in
the chilled or thawed state, the discoloration diffuses into the oyster liquor. The
inspector will check for this condition at destination inspection and at cold storage sites.
Slicing oyster samples and holding them for 24 hours can detect this condition.