May I make a few comments re the "difference" between fresh seafood which by definition has not been subjected to temps below minus 1 C. and frozen seafood which has.
Seafood begins to freeze at about minus 1.5 C or about .5 C colder than ice/salt slurries. At about -1.5 C ice crystals start to form in flesh, permanent damage to eye tissue occurs and extremities such as fins begin to desiccate.
The principal reason for "snap freezing" is to take the product through the temperature range of minus 1 through minus 5 C as quickly as possible to prevent formation of large ice crystals in flesh that will have a deleterious effect on flesh texture -- noticeable after thawing. Glazing techniques also help to prevent desiccation of body extremities so that seafood that has been frozen (here, as pointed out by Allan Bremmer, we need to insert "properly") may have few detectable differences when thawed and compared with fresh product relative to flavour and texture of flesh.
But my experience with Australian public perceptions of labelling such as: fresh, fresh-frozen and frozen (but thawed for your convenience) agrees with Mark Boulter's comments in that there is a definite public preference for fresh, meaning never frozen, but kept iced.
I don't know of any organoleptic testing that may have been undertaken as a means of providing a definitive range of differences between identical species that differ only as being either fresh or frozen. Might prove interesting.
Regards,
Don Tuma
----- Original Message -----
From: Mark Boulter
To: Steve_Lamming@youngsbluecrest.com ; seafood@ucdavis.edu
Cc: Allan Bremner
Sent: Thursday, April 12, 2007 9:07 AM
Subject: RE: "Fresh" vs Frozen.
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What a very interesting question you pose Steve.
I have attached below a copy of a section of the 'hot of the press' Australian Quality Index Manual, that was written by Allan Bremner, the respected seafood scientist. I think this will be useful to such a debate as it raises the issue of what parameters do you measure products against, to compare product A against product B, whether that be fresh vs frozen or supplier X vs supplier Y. I have found Allan's explainations of these issues to be very insightful.
Here at Sydney Fish Market we have found that it is not so much what the technical 'freshness' of a product is that matters the most, but the public's opinion and market research that our company has conducted has shown that regardless of the technical merits of a frozen product the public prefers product that is 'fresh never frozen'.
Regards,
Mark
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Mark Boulter
Quality, Environment and Safety Manager
Sydney Fish Market Pty Ltd
Bank Street, Pyrmont NSW 2009
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QI and Freshness and Quality
Freshness and quality are really marketing and consumer terms and have no scientific and technical validity, unless they are very tightly defined. Even then, disputes and confusion readily arise as both words (quality and freshness) are used in many different contexts and the user often slips between one context and the other, even within the one sentence. They are very useful, common, everyday terms but their use should be avoided in technical matters. Thus in assessing seafood, it is far better to stick to objective descriptions and to evaluate discrete properties and attributes (Bremner 2002).
"Quality Index" is therefore used here in the sense that it provides a guide to the "quality" of the seafood when it is finally eaten. The term is adopted because of the widespread acceptance and understanding of the European Quality Index Method (QIM).
The Australian Seafood Standard states that "fresh" seafood refers to product that has not been frozen, cooked, or preserved by any method other than chilling. This meaning of the word as applied to seafood that has not been frozen is common. Freshness is also often used in the context of time elapsed since the fish was harvested but, strictly speaking, the temperature must also be taken into account so that this concept of freshness can be related to the number of icedays. Sometimes fresh is also used in the context of meaning 'freshly thawed' for frozen product that has just been thawed, or in the phrase 'freshly cooked' for product just recently cooked, perhaps even from frozen and thawed material.
The word quality can bring in several more concepts such as the end use for the product, the workmanship involved in preparing it, whether it is to be fried, baked or steamed for example, or whether it's colour is more acceptable in the market place, as may happen with Atlantic Salmon. These examples indicate the multiplicity of problems that occur with the use of the words freshness and quality. It is much less controversial to use descriptors of attributes and properties and the number of equivalent icedays as indicators to evaluate the product and predict remaining shelf life.
What is Shelf life?
There is no such thing as a set shelf life for any species of fish or fish product; Shelf life varies according to circumstances and criteria chosen to determine it. It depends entirely on who is using the information and what the product is to be used for (Barbosa et al. 2002). The shelf-life of seafood to be consumed raw, is clearly shorter than for that which is to be cooked, and different criteria apply.
Thus, the shelf-life of any seafood depends on limits that are arbitrarily set. These limits may range from expert opinion, through 'rules of thumb' based on experience, or they may be set by rigorous investigations of market and consumer opinion. A good indication of shelf life is when the seller no longer wishes to have their name on the product. As an example, in order to protect their brand name as a supplier of top product, many traders sell poorer product under a separate name, although it may still be quite fit for consumption.
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From: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu] On Behalf Of Steve_Lamming@youngsbluecrest.com
Sent: Wednesday, 11 April 2007 10:28 PM
To: seafood@ucdavis.edu
Subject: "Fresh" vs Frozen.
Hi all,
There are a lot of claims and counter-claims in the UK at present about the relative merits of "fresh" fish vs frozen in terms of quality. Is anyone aware of any objective research conducted on this topic, or do any of you have a clear opinion or experience in the field?
(I know there will be some who say the you can't get fresher than frozen at sea!)
Thanks and regards,
Steve
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