Innovative Nondestructive Measurements of Water Activity and the Content of Salts in Low-Salt Hake Minces

Abstract

Impedance spectroscopy (IS), low-field proton nuclear magnetic resonance (LF 1 H NMR), chloride titration, ion chromatography, and an ion selective electrode were used to investigate the physicochemical parameters and measure sodium and potassium contents in low-salt brines and fish. Salt solutions (0−3 w/w, %) and model products of minced hake with added NaCl (0.5−3.0 w/w, %), or a mixture of NaCl and KCl (50/50 w/w, %), were analyzed. Good correlation was observed between the sodium content determined by using the ion selective electrode method and ion chromatography (R 2 = 0.97). In both salt solutions and fish minces, the impedance spectroscopy measurements could detect the difference in salt contents in mince with salt contents down to 0.5%. The NMR transversal relaxation time T 2 measurements clearly distinguished samples with 0, 0.5, and 1.0−3.0% salt, based on principal component analysis (PCA). Therefore, LF 1 H NMR seems to be a suitable technique for studies of low-salt products.

Effects of type and concentration of salts on physicochemical properties in fish mince

“…By comparison, addition of 0.5% NaCl or NaCl/KCl to raw mince of hake increased the T 21 proton relaxation time to 59e61 ms whereas the T 22 value remained largely unchanged. Further addition of salt increased both T 21 and T 22 relaxation times, with mean values of 67e71 ms and 286e496 ms, respectively (Greiff et al, 2014). Compared to the conventional methods for characterization of cooked mince, these results show that the LF 1 H NMR T 2 relaxation method can provide additional information about to changes in the protein structure as result of addition of salt.…”

“…Sodium was determined at ambient temperature with a Na-selective electrode (Ross ® Sodium Ion Selective Electrode, Thermo Fisher Scientific, USA) and a Dual Star pH/ISE meter (Thermo Fisher Scientific, Waltman, MA, USA), under constant stirring (Kivikari, 1996) as modified by Greiff et al (2014). The analytical uncertainty of the method was determined by analysing three extracts from each of three replicates of the same cooked mince.…”

“…LF 1 H NMR samples preparation and analysis was performed according to Aursand, Gallart-Jornet, Erikson, Axelson, and Rustad (2008), Greiff et al (2014) as follows. Three subsamples (about 1 Â 1 Â 3 cm, approximately 2e3 g) from each cooked mince were placed in NMR tubes (diameter 10 mm).…”

Applications of Non-invasive and Novel Methods of Low-Field Nuclear Magnetic Resonance and Magnetic Resonance Imaging in Aquatic Products

“…In addition, LF-NMR provided more information on swelling mechanisms than conventional methods, establishing its potential for further investigation. Greiff et al (46) used LF-NMR to study the effects of different concentrations of salt additives on the protein structure of carp surimi. As the concentration increased, T 21 and T 22 gradually increased, and the cooking loss rate and WHC decreased because the interaction between water molecules and proteins in the muscle fibers was suppressed.…”

LF 1H NMR T2 relaxation rate as affected by water addition, NaCl and pH in fresh, frozen and cooked minced hake

“…LF 1 H NMR in seafood has been used to evaluate raw material characteristics, including anatomical location (Andersen & Rinan, 2002;Løje, Green-Petersen, Nielsen, Jørgensen & Jensen, 2007;Aursand, Erikson & Veliyulin, 2010), fat, water content and seasonal variation (Jensen, Jørgensen, Nielsen & Nielsen, 2005), wild vs. farmed (Gudjónsdóttir et al, 2010), the effect of post-mortem events such as pre-slaughter handling stress (Aursand et al, 2010), rigor mortis development (Aursand, Veliyulin, Bocker, Ofstad, Rustad & Erikson, 2009 or different processing and storage factors on product characteristics such as salting, desalting, dry salting and rehydration (Aursand et al, 2009;Gudjonsdottir, Arason & Rustad, 2011;Greiff et al, 2014;Carneiro et al, 2016), smoking (Løje et al, 2007), superchilling (Erikson et al, 2012), pressure treatment (Shang, Liu, Zheng, Wang & Yin, 2015), freezing rates and freezing methods (Sánchez-Alonso, Moreno & Careche, 2014;Erikson et al, 2016), time and temperature of storage (Lambelet, Renevey, Kaabi & Raemy, 1995;Steen & Lambelet, 1997;Jepsen, Pedersen & Engelsen, 1999;Yano, Tanaka, Suzuki & Kanzaki, 2002;Erikson, Veliyulin, Singstad & Aursand, 2004;Sánchez-Alonso, Martínez, Sánchez-Valencia & Careche, 2012Sánchez-Valencia, Sánchez-Alonso, Martinez & Careche, 2015;Erikson et al, 2016), or presence of additives (Carneiro, Marsico, Ribeiro, Conte, Alvares & De Jesus, 2013a,b;Gudjónsdóttir, Karlsdóttir, Arason & Rustad, 2013;Nikoo, Regenstein, Ghomi, Benjakul, Yang & Xu, 2015;Asli, Ofstad, Ulrike, Jessen, Einen & Morkore, 2016).…”