Salting and Desalting of Fresh and Frozen‐thawed Cod (Gadus morhua) Fillets: A Comparative Study Using 23Na NMR, 23Na MRI, Low‐field 1H NMR, and Physicochemical Analytical Methods

Abstract

Fresh and frozen-thawed cod raw materials were subjected to brining, dry salting, and rehydration. The effects of salting and desalting on fillet water-related properties, salt content, and salt distribution were studied using 23 Na MRI, 23 Na NMR, and low-field (LF) 1 H NMR. The results were compared with the Volhard titration method for salt determination, fillet pH, water content, and water-holding capacity. The rehydrated end product showed significant difference only with respect to water-holding capacity (unfrozen raw material higher) when fresh and frozen-thawed raw materials were compared. Excellent correlation was obtained between quantitative salt determinations using 23 Na NMR and Volhard titration. When using a typical salting method, it was shown that the salt uptake and salt distribution in the fillets were inhomogeneous. Proton relaxation times, obtained from LF 1 H NMR, were processed using either a 2-exponential model or the CONTIN algorithm. In several instances, a clear dependence on fillet pH, water-holding capacity, or salt content during fish processing was observed. Our results indicate that NMR and MRI can be used as useful tools to evaluate and optimize fish processing unit operations and that rapid (LF) NMR methods have the potential for replacing traditional salt and water-related analytical methods.

Injection of fish protein solutions of fresh saithe (Pollachius virens) fillets studied by low field Nuclear Magnetic Resonance and physicochemical measurements

“…Most studies report 2-3 water populations in fish and meat muscle, depending on their proton relaxation properties (Jepsen et al 1999;Erikson et al 2004;Bertram and Andersen 2007;Bertram et al 2009;Aursand et al 2009). Bertram and Andersen (2007) and Bertram et al (2009) identified three water populations in pork at 1-3 ms (T 2B ), suggested to correspond to water closely associated with macromolecules and proteins, at 40-80 ms (T 21 ), suggested to correspond to myofibrillar water or water located within organized protein structures and at 200-400 ms (T 22 ) corresponding to extra-myofibrillar water.…”

“…No significant difference was seen in the relaxation times between the chilled salt injected fillets and the control fillets, although the added salt affected the water distribution. The amount of water in the middle relaxing water pool (A 2b ) increased as a result of muscle swelling and water uptake caused by the electro-repulsive forces within the muscle structure caused by the added salt (Erikson et al 2004), while the amount of water in the shortest relaxing water pool (A 2a ) decreased. Injection of salt in combination with HFP(a) and/or gelatine resulted in the longest relaxation times, indicating that the injection of these proteins affected the characteristics of these water pools the most compared to the control fillets.…”

“…Transversal relaxation time measurement have shown to give strong correlations to various physicochemical properties of fish and meat muscle, such as moisture content (Andersen and Rinnan 2002), water holding capacities and drip loss (Jepsen et al 1999;Erikson et al 2004) and has been used to indicate pH-induced structural changes occurring in the muscle post mortem (Bertram et al 2000) as well as the effects of frozen storage on protein denaturation in fish (Steen and Lambelet 1997). The technique can give valuable information about the distribution of water throughout the muscle and how it is changed by various handling or processing (Jepsen et al 1999;Erikson et al 2004;Bertram and Andersen 2007;Bertram et al 2009;Aursand et al 2009) and is therefore an excellent technique for studies on the effects of protein injection to fish muscle.…”

Evaluation of Physicochemical Characteristics of Smoked River Catfish Prepared from Fresh and Frozen Raws

“…Analisis water holding capacity daging ikan dilakukan menurut metoda Eidi et al (1982) dan Erikson et al (2004). Sampel ikan (fillet dan belah) dihaluskan dengan grinder dan disentrifugasi selama 5 menit pada 1477 rpm (264 x g).…”

“…Perbedaan antara nilai rata-rata dari setiap perlakuan dideterminasi menggunakan Uji Beda Nyata Terkecil. (Barroso et al 1998); (Erikson et al 2004); (Hurling dan McArthur 1996); (Mackie 1993); (Regost et al 2004); dan (Solberg et al 2000). Menurunnya water holding capacity daging ikan yang disimpan beku dapat disebabkan oleh perubahan struktur daging ikan akibat pembekuan.…”