Oysters can be purchased opened (shucked) in the half-shell or closed. Closed live oysters have a longer shelf-life. If purchasing opened oysters look at the meat and shell qualities, the oyster should appear similar to this:
Opened oysters stored covered in the refrigerator, below 5 degC, may remain in good condition for up to 3-4 days. If purchasing live oysters, get them as close to harvest date as possible if you want to keep them for a week or so. Store in the refrigerator with the flat shell upwards, so the cup of the shell retains the liquor if the oyster opens. A damp cloth may be used to weigh down the top shells preventing them from opening and drying out. They are best opened just before serving.
The angasi oyster is a higher priced oyster than the Pacific oyster as it takes more than twice as long to grow and needs more attention to prepare it for market.
Oysters Available In Australia
Globally Pacific oysters are the most widely consumed oyster. The Pacific oysters (Crassostrea gigas) grown in Australia are native to south east Asia. The two main species of native oysters in Australia are Sydney rock (Saccostrea glomerata) and angasi (Ostrea angasi). These native oysters have different characteristics. Both are uniquely full flavoured slow growing oysters taking 3 to 4 years to reach market. Sydney rock oysters broadcast spawn (like Pacific oysters) with fertilisation occurring in the water, whereas angasi oysters brood larvae within, releasing spat (larvae seed) into the surrounding waters. Sydney rocks thrive in the inter-tidal zone whereas the preferred habitat of the angasi is sub-tidal to deep waters.
In Australia oysters are predominantly produced by off-bottom aquaculture with a small number entering the market as a result of by-catch from dredge fisheries and the like. The Oyster Province oysters are grown in the top 4m of 10m deep water.
Food Safety And Quality Assurance Program
In Australia shellfish producers are required by law to follow a Food Safety Plan to ensure industry best practice in delivering food safe produce to market. Each grower’s Food Safety Plan is independently audited annually and growers have to gain Department of Primary Industry Accreditation. Part of the Quality Assurance Program is carried out by government laboratories which conduct weekly scientific water quality monitoring and testing shellfish samples as necessary.
From time to time there are naturally occurring toxic algal blooms that do not adversely affect the shellfish but can have harmful health implications for the consumer. Rainfall events can also affect water quality, reducing salinity and raising E. coli levels. Shellfish growers supply the water and meat samples to the scientists who in turn inform the growers of the results and declare the marine farm as OPEN or CLOSED for harvest according to the test results.
Warning – Eating Shellfish Off The Rocks At The Beach Is Not Safe
Toxic algal species may be present in an area where wild shellfish are apparently thriving. Just looking good to eat unfortunately is no guarantee of their safety.