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Improved quality and shelf life of desalted cod and easy to use product of salted cod.

Objective


The main objective of this project is to obtain knowledge about the sensorial, microbial and chemical aspects of desalted cod in order to assure the product quality by controlling the desalting process. High product quality is defined as safe and stable products of high sensorial quality that fulfil the consumer's demands. Since many of the technological and microbiological aspects of the desalting process as well as the desalted products are not understood yet, the purpose of this project is to:
- Develop easy-to-use desalted cod products, with the same sensorial characteristics of the traditional desalted (dried) salted cod, by optimising the traditional technology and using a new one (vacuum desalting).
- Improve the shelf life and the safety of these easy-to-use products.
- Disseminate the knowledge obtained to the industry, especially in what concerns product quality and necessary hygienic conditions according to the HACCP standards.

RESEACH TASKS

The work will proceed in three phases, summarised as follows:

Phase 1: Analyses of commercial available products

Task 1. Optimisation and standardisation of methodologies.
Task 2. Characterisation of the local sensorial preferences in some consumer countries.
Task 3. Investigations of the extent of recontamination in desalted cod products.
Task 4. Production of reference samples of dried salted cod.

Phase 2. Study the effect of desalting methods, both the traditional and new developed

Task 5. Performance of desalting trials.
Sub-task 5.1. Desalting with traditional methods.
Sub-task 5.2. Testing and development of desalting by vacuum technology

Phase 3. Study the effect of different treatments and storage conditions of desalted cod

Task 6. Performance of desalted product treatments and storage under different conditions.
Sub-task 6.1 Freezing, cold storage and thawing.
Sub-task 6.2 Immersion in hot water and steam followed by chilled storage in normal and vacuum packages.
Sub-task 6.3 Combined treatments of microwaves, hot air and/or vacuum Impregnation.
Sub-task 6.4 Addition of preservatives followed by chilled storage w/o vacuum
Sub-task 6.5 Different heat treatments plus the addition of a preservative followed by chilled storage in normal and vacuum packages.

OVERALL METHODOLOGY

The desalting methods will be similar to the ones used in the industry, but scaled down to laboratory scale. Each partner will choose experimental conditions leading to sensorial preferred products in their country.

Sensorial analysis will play a major role in the project, as the sensorial quality is one of the two criteria for evaluation of whether the changes in the desalting procedure and treatments during storage of the products have been successful. The analyses will be carried out both by trained and untrained panels. "Untrained panels" means internal panels of staff that work with non-related subjects, and therefore represent the consumers. Common schemes will be used in order to make comparison of the sensorial evaluations possible. The development of the common schemes is described under task 1.

Physico-chemical analysis such as proximate composition, salt concentration, water holding capacity, as well as colour and texture will be measured by well established methods by each partner. All the partners will use the same methods as far as possible, including how the samples are taken and prepared, as this will make statistical analyses of results among the partners possible. In case of colour and texture measurements, which are done with special instruments, a variation between the partners has to be accepted due to different equipment. However, the different instruments will be calibrated using common samples for all the partners, according to task 1.
Microbial analysis. The load of microorganisms in the products will be analysed by colony formation on suitable agar plate media and incubation conditions. Growth media for detection of halophilic and salt tolerant bacteria in light and heavy salted fish, including spoiling bacteria, have been developed by partner 1. The number of spoiling bacteria is correlated to remaining shelf life of desalted cod. The analyses are therefore important in evaluation of the desalting processes (phase 2) and storage conditions (phase 3)..

The content of hygienic indicators and pathogens like total/faecal coliforms, faecal streptococci, and pathogenic strains like Staphylococcus aureus coagulase , Pseudomonas, Listeria, Salmonella, Vibrio, as well as yeasts and moulds will be determined using selective media and instrumental techniques (Vitek system). The vitek system uses a biochemical identification principle, based on the study of bacterial growth kinetics in the presence of specific substrates. It uses cards, which are inoculated containing 30 micro wells with substrate required for the various reactions. The workstation combined with the card performs the various preparation and interpolation steps without manual interventions. Analyses of pathogens will be especially focused in phase 3 of the project, since the risk of food poisoning of pathogenic organisms is higher in products with long shelf life than in products that are rapidly spoiled..

The physiology of the organisms will be characterised by traditional microbial methods, such as Gram staining, selective media and enzymatic tests. In addition, the growth rate at different salt concentrations, temperatures and oxygen levels will be determined, and their survival during freezing and thawing will be investigated. These analyses will give indications of how the organisms could be removed or inhibited in the products, which is considered to be important in this project. However, these analyses do not give an accurate identification of the organisms. The dominating organisms in the products will therefore be analysed by some DNA-analyses (restriction enzymes and, if considered necessary, dot-blot or RAPD fingerprinting) and compared with some of the known spoilage organisms in fish, in order to investigate whether the products are spoiled by some of these.

In all the phases of the project there will be used statistical experiment designs.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

NORWEGIAN INSTITUTE OF FISHERIES AND AQUACULTURE LTD
Address
University Campus Breivika
Tromsö
Norway

Participants (2)

Instituto de Investigacao das Pescas e do Mar
Portugal
Address
Avendida De Brasilia
1449-006 Lisboa
UNIVERSIDAD POLITECNICA DE VALENCIA
Spain
Address
Camino De Vera S/n
46022 Valencia