Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

In search of the perfect oyster

07.10.2004


What is actually a “good” oyster? How can we evaluate and grade ”quality”? And how can we produce the quality we wish?



The European flat oyster has been used as food as long as man has inhabited the European coastline. The ancient Romans established oyster farms, and oyster culture and harvest gradually developed as an important activity along the coasts of Europe. Today, the oyster industry is important. The Pacific oyster, which is now the dominant species, is cultivated all over the world at the incredible rate of more than three million tonnes a year.

All over the world, oysters are a popular seafood, which are presented in a variety of species, forms and qualities. Many oyster consumers have strong opinions of the quality and origin of their preferred oysters. But, in spite of the long history of oyster culture and the high status of this seafood product, there are surprisingly enough, neither standardised quality grades nor defined, applicable quality parameters . . . and very few scientific papers describing the sensory quality of oysters have been written. This field is a wide-open challenge . . .


Stein Mortensen (Institute of Marine Research) and Arne Duinker (NIFES) have taken up the challenge. Mortensen has strong opinions about oysters and is convinced that Norwegian oyster growers are capable of producing ”the perfect oyster” - if they can learn how to optimise quality through a perfect production chain, including grading and correct handling. Without measurable quality standard parameters the industry will never attain this goal.

The first step of the work has been to define some sensory (appearance, taste, smell, texture) parameters to be used to evaluate oyster quality. Chef Morten Schakenda joined a team from the sensory panel at NORCONSERV in Stavanger, under the supervision of colleagues from the Norwegian University of Agriculture at Ås, in order to define some recognisable sensory attributes.

These were used in an experiment in which oysters were stored live under various conditions for several weeks. A panel of experts with different backgrounds and expertise then sampled and analysed the oysters. Did the sensory profile of the oysters change? How? How fast? Did they die as a result of prolonged storage times and unsuitable conditions? Did the bacterial load increase? And were there changes in the different oyster tissues? The answers to these questions have been published in the August 2004 issue of the Journal of Food Science.

Storage in fresh seawater best

The results obtained by the research team showed that the sensory profile of live oysters stored on ice and in a cool storage room was significantly different from that of live oysters stored in seawater. Oysters kept in freshwater ice suffered the most pronounced changes, and also displayed detrimental tissue alterations caused by the low storage temperature. Dead and live oysters could easily be distinguished by measuring the pH of their flesh with a probe pressed directly into the adductor muscle.

A gradual death

Lisbeth Harkestad from IMR and Kristin Hopkins from the National Veterinary Institute open and measure oisters. Studies of death and autolysis of oyster tissues during the experiment also produced some interesting results. As the bivalves lack a central nervous system, individual organs gradually stop functioning one by one. We may say that the oyster dies “a bit at a time”. If the temperature is low – as it should be during storage – the death process is slow. Moribund oysters may in fact respond to a stimulus and be considered ”live” at the same time as an autolytic process is going on inside their ”dead” digestive tissues. Such oysters, of course, are not edible.

The experiments showed that the human nose may be trained to become a very sensitive sensory instrument to evaluate oyster quality. Positive olfactory parameters such as ”sea”, ”fresh fish” and ”shellfish”, and negative parameters like ”mud”, ”rotten seaweed” ”ammonia” and ”spoiled shellfish” are relatively easy to learn. The results also verified the important and practical point that oysters should be kept cool – but not on ice.

Oysters do have a remarkable ability to survive if they are stored correctly – that means cool and humid and with a light pressure on top of them, which keeps them from opening. It is therefore tempting to expect that they can also retain a satisfactory quality for a long period of time. Unfortunately, they do not! If we want “the perfect oyster”, we have to accept that the fresh “sea” taste disappears rather quickly. The oyster stays fresh for only a few days after it has been harvested. It may seem to be a paradox, but professional logistics and live storage facilities are essential – even in the production of a bivalve that can be kept alive for weeks!

Now, Mortensen and Duinker are starting work on the second step in their process – using the experience they have gained from the storage experiments and the establishment of a sensory profile in order to develop a quality grading system that can be used by producers, wholesalers and chefs. “The perfect oyster” has to be good enough. If not, it will soon be “dead” in the market. In collaboration with Eivind Bergtun at Bømlo Skjell and a network of oyster growers south of Bergen, they are collecting and evaluating the quality of oysters in the entire region. Measure, weigh, look and taste . . . According to Mortensen the results are promising. “The perfect oyster” should not be too far away . . .

Stein Mortensen | alfa
Further information:
http://www.imr.no/english/

More articles from Agricultural and Forestry Science:

nachricht New insight into why Pierce's disease is so deadly to grapevines
11.06.2018 | University of California - Davis

nachricht Where are Europe’s last primary forests?
29.05.2018 | Humboldt-Universität zu Berlin

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Graphene assembled film shows higher thermal conductivity than graphite film

22.06.2018 | Materials Sciences

Fast rising bedrock below West Antarctica reveals an extremely fluid Earth mantle

22.06.2018 | Earth Sciences

Zebrafish's near 360 degree UV-vision knocks stripes off Google Street View

22.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>