Development of a Turbidimetric Sequential Injection System to Monitor the Codfish Desalting Process
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Development of a Turbidimetric Sequential Injection System to Monitor the Codfish Desalting Process Inês C. Santos & Raquel B. R. Mesquita & Andrea C. Galvis-Sánchez & Ivonne Delgadillo & António Osmaro S. S. Rangel
Received: 7 March 2011 / Accepted: 5 April 2011 / Published online: 17 April 2011 # Springer Science+Business Media, LLC 2011
Abstract Salt-cured codfish represents an ancient process of preservation but requires the rehydration of the codfish with the correspondent salt removal. This work describes the development of a sequential injection system for the online turbidimetric determination of chloride during a simulated desalting process. The samples are directly aspirated to the manifold with no need for previous offline treatments; this was possible due to the use on an inline dialysis process; a quantification range from 50.0 mg/L to 20.0 g/L was established using the same manifold configuration. For monitoring the entire process, involving several chloride determinations (ca. 10), less than 3 mL of the desalting water was needed. Furthermore, the overall reagent consumption was quite low: 0.211 mg of AgNO3, 30.6 mg of HNO3, and 31.1 μg of PVA per determination.
I. C. Santos : R. B. R. Mesquita : A. C. Galvis-Sánchez : A. O. S. S. Rangel (*) CBQF/Escola Superior de Biotecnologia, Universidade Católica Portuguesa, R. Dr. António Bernardino de Almeida, 4200-072 Porto, Portugal e-mail: [email protected] R. B. R. Mesquita Laboratory of Hydrobiology, Institute of Biomedical Sciences Abel Salazar (ICBAS) and Institute of Marine Research (CIIMAR), Universidade do Porto, Lg. Abel Salazar 2, 4099–003 Porto, Portugal A. C. Galvis-Sánchez : I. Delgadillo Departamento de Química, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
The accuracy of the system was evaluated by comparison with a potentiometric reference method. The determination rate was 28 and 31 h −1 according to the chloride concentration range. Several simulated desalting processes, under different conditions, were effectively monitored with the developed method. Keywords Codfish desalting . Sequential injection analysis . Dialysis . Turbidimetric chloride determination
Introduction Salt-curing was an ancient method used for the preservation of codfish and it is still being applied due to tradition. Drying and salting preserve and inhibit the decomposition of the fish by microorganisms’ action. The salt dehydrates the codfish by difference on osmotic pressure and penetrates the fish, lowering its water activity (aw). Since water activity is essential for microbial reproduction, with its decrease, the codfish is preserved during long periods of time at room temperature. This method of preservation also allows the development of characteristic flavor (Zhang and Xia 2008). Salted codfish is usually desalted prior to its consumption. Nowadays, due to changes in the lifestyle of the consumers, high-quality and ready-to-use codfish is demanded by the consumers. For that reason and in order to adapt the codfish indu
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