4 replies to this topic

[dougn7110]

what's the total maximum Pseudomonas in shellfish allowed ? or acceptable ?

[jdpaul]

I think most would measure histamine since it a bacterial signal molecule

 

1. https://op.europa.eu...dbf/language-en

 

2. https://www.fsai.ie/...amine_fish.html (Quote below from source)

 

 

How is histamine produced? 

Histamine is produced when bacteria that naturally occur in the skin, gills and gut of fish break down histidine, an amino acid found in the muscles of certain fish species that contain naturally high levels of this amino acid (mackerel/herring/sardines/tuna). The production of histamine is directly related to the mishandling of food as a result of storage at incorrect temperatures. Histidine decarboxylase, the enzyme responsible for breaking down histidine into histamine, can remain active even after the bacteria responsible for producing it have been inactivated or killed. The enzyme continues histamine production slowly at refrigeration temperatures and remains stable if frozen, thus allowing it to rapidly recommence activity after thawing. Although the enzyme that produces histamine can be inactivated by cooking, once histamine has been produced, it cannot be eliminated by normal cooking or freezing temperatures, and its toxicity remains intact.

 What are the signs of food spoilage that can result in high levels of histamine? 
Harmful levels of histamine can build up in fish before any signs of spoilage develop, such as a bad smell or taste. For these reasons, control strategies focus on prevention through the use of strict temperature control throughout the food chain.

 Which bacteria are involved? 
A wide range of bacteria are capable of producing histamine. Examples include Morganella morganii, Klebsiella spp., Pseudomonas, Clostridium, Citrobacter freundii and more. Many of these bacteria are found naturally in fish environments.

 

3. https://eur-lex.euro...046:0047:EN:PDF

[Charles.C]

what's the total maximum Pseudomonas in shellfish allowed ? or acceptable ?

Hi doug,

 

Offhand I cannot recall ever seeing a mention of Pseudomonas spp in shellfish specifications although some species in the genus are pathogenic.

 

Is there some particular context to your query, eg freshwater/farmed/marine product/customer complaint ?

[dougn7110]

Hi

It was one that the lab we use included in our testing suite for cooked shellfish e.g crab meat whole crab lobster and langoustines etc. I’d drop it if we could justify it

[Charles.C]

Hi

It was one that the lab we use included in our testing suite for cooked shellfish e.g crab meat whole crab lobster and langoustines etc. I’d drop it if we could justify it

afai can see from a quick literature scan, the main interest in P.x in seafood is its significance as a spoilage bacterium/shelf life predictor. For example this abstract -

 

Microbial activity and spoilage of Norway lobster (Nephrops norvegicus) from Greek temperate waters, stored in air at 20, 5 and 0 °C was assessed. Microbial spoilage population, Total Volatile-Base Nitrogen (TVB-N), Trimethylamine-Nitrogen (TMA-N), pH and organoleptic changes were determined. Shelf-life of Norway lobster stored at 20, 5 and 0 °C was 24, 72 and 96 h respectively. The product was spoiled due to the development of TVB-N and melanosis of the carapace, as TVB-N was apparent from the early stages of storage and correlated very well with microbial growth and shelf-life. Pseudomonas sp. was the predominant spoilage bacterium. Product rejection coincided with TVB-N levels of 330–400 mg kg−1 and Pseudomonas sp. population level of about 5 × 105 cfu g−1. Pseudomonas sp. and TVB-N are presumably the Specific Spoilage Organism and the Chemical Spoilage Index of the product.

 

 

And this observation for tropical shrimp -

 

In general, a high concentration (8–9 log CFU/g) of the inoculated [Pseudomonas] bacteria in cooked shrimps was obtained at the sensory rejection times, while the microbial concentration of Pseudomonas spp. in fresh shrimps at the sensory rejection times was lower.

 Prediction of Spoilage of tropical shrimp.pdf   858.08KB   1 downloads

 

The UK  document detailing micro. guidelines for commercialized RTE foods has this comment -
 

 

An ACC of less than 10⁶ cfu/g is usually associated with a mixed flora. Above this level there is usually a predominant
organism, and the acceptability and organoleptic quality of the food will depend on which type of organism
predominates. In meat products for example the flora frequently consists almost entirely of lactic acid bacteria
(mainly lactobacilli and streptococci), which can grow well at refrigeration temperatures. Spoilage will eventually
occur at a level of around 10⁹ cfu/g due to the production of lactic acid. If the predominant organism or group of
organisms consists of Gram-negative bacteria, spoilage is likely to be noticeable at 10⁷ – 10 ⁸ cfu/g; pseudomonads
tend to produce taints, discolouration, and slime whilst other Gram-negative bacteria frequently produce slime.
Yeasts may cause spoilage at slightly lower levels (10⁶ –10⁷ cfu/g) due to acid and gas production. If high levels of
Bacillus spp. are found this may be due to the addition of pepper or other spices after any heat treatment; investigations of the full preparation process is needed.
If ACCs are high it is therefore important to identify the predominant organism type in order to fully interpret the
significance of the level. Tests by the laboratory for catalase and oxidase production and a Gram stain are usually sufficient to achieve the differentiation needed to interpret results

(There is no mention of limiting guideline values for P.x)

 

I anticipate that the P.x lab results for your samples were far below levels  such as discussed above?