(23)Na-MRI quantification of sodium and water mobility in pork during brine curing

A model study on movements of sodium ions in pork loin during brining was carried out using ²³Na-magnetic resonance imaging (²³Na-MRI). Samples of different pH and post-mortem age were mounted in Plexiglas^® cylinders with built-in phantoms and cured in 18.9% and 18.1% NaCl (w/v), respectively. One-dimensional ²³Na-MRI and apparent diffusion coefficient (ADC) profiles were obtained over 5 days with intervals of 24 h. On day 5 the meat was cut into 1 cm slices and analyzed for chloride content. ²³Na-MRI and ADC profiles of meat provided detailed non-destructive information about salt and water movements during brine curing. Quantification of salt concentration in meat by one-dimensional ²³Na-MRI profiling proved successful at values above 0.9 g NaCl/100 g sample in the meat. ²³Na measurements were calibrated against chemically determined chloride, yielding a linear relationship. ²³Na-MRI profiles suggested that the diffusion of salt into whole meat cuts cannot be described by simple ordinary Fickian diffusion with a constant diffusion coefficient. The diffusion coefficient is suggested to be affected by changes in NaCl concentration, swelling and degree of dehydration.     

鸭腿减盐滚揉腌制过程中的传质动力学

用减盐（30% KCl＋70% NaCl）和氯化钠食盐（即普通食盐,NaCl质量分数≥99.1%）分别腌制肉鸭鸭腿,测定滚揉腌制过程中鸭腿肉总质量、水分质量分数、食盐质量分数变化情况,获得鸭腿肉在不同食盐腌制时的传质动力学数据,并进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳实验,研究不同食盐滚揉腌制过程对鸭腿肉蛋白质的影响。结果显示：氯化钠腌制和减盐腌制中鸭腿肉的总质量变化量（ΔMt0）、水分质量分数变化量（ΔMtw）以及盐分含量变化量（ΔMts）均与腌制时间的平方根（t0.5）呈现出较好的相关性,而且前4 h ΔMt0、ΔMtw以及ΔMts增长较快;氯化钠腌制和减盐腌制的有效扩散系数De分别为4.432×10－8 m2/s和4.462×10－8 m2/s,相差较小;十二烷基硫酸钠-聚丙烯酰胺凝胶电泳图谱显示两种腌制方法肌原纤维蛋白都在不断降解。综上,减盐腌制和氯化钠腌制相比,对传质速率并无明显影响。     

Tenderness and Sodium Content of Pectoralis superficialis from Broilers Chilled in Potassium or Sodium Chloride Ice Slush

Cooked light meat (Pectoralis superficialis) from broiler carcasses chilled (4 hr, with agitation) in 5% (w/w) sodium chloride (NaCl), 5% (w/w) potassium chloride (KCl), or ice slush was evaluated for moisture content, tenderness (shear force), chloride ion (Cl) concentration, and sodium ion (Na) concentration. Water uptake of the carcasses during chilling was determined. Chilling in either salt solution increased cooked meat moisture, increased chloride ion concentration, and decreased shear force values. Sodium level and water uptake were increased by NaCl brine ice-slush chilling. Samples chilled in NaCl had higher chloride concentrations and lower shear force than samples chilled in KCl.     

NaCl对猪肉干燥过程中质构特性的影响

以猪背最长肌为研究对象,经不同浓度NaCl溶液腌制后,60 ℃下热风干燥后其质构特性参数随含水率和NaCl含量的变化规律。结果表明:随含水率降低,各样品的剪切力值、硬度及咀嚼性均逐渐增加,而弹性、内聚性则逐渐下降;在相同含水率下,腌制液NaCl浓度≤8%腌制样的剪切力值、硬度、咀嚼性随NaCl浓度的增大而增大,腌制液NaCl浓度＞8%腌制样的上述参数随NaCl浓度增大而减小,各腌制样的弹性随腌制液NaCl浓度升高而逐渐减小,内聚性受NaCl浓度的影响较小。由部分物理指标与质构特性参数之间的相关性分析可知:肉样的质构特性参数与样品的含水率、横向收缩比(LSR)、纵向收缩比(TSR)、体积变化率等极显著相关(p<0.01),而相关系数的大小与腌制液NaCl浓度有关。研究结果为腌制肉的品质控制提供参考。     

Sodium diffusion in cured pork determined by (22)Na radiology

A (22)Na-radioisotope method was developed as a non-destructive method for studying NaCl diffusion in meat. Scanning a well-defined cylindrical geometry with diffusion from one end gave reliable sodium diffusion profiles in meat. The diffusion coefficients derived from the profiles amounted to 5-7×10(-10)m(2)/s at 21°C, largely in accordance with the general findings of the literature. Subsequent autoradiography carried out on the same samples demonstrated the feasibility of this method for validation of different experimental set-ups. The diffusion profiles were skewed showing a wall effect which, however, did not prevent consistent determination of the diffusion coefficient. The results suggest that the diffusion of salt in meat may depend on the individual animal. The present study appears to be the first to employ radioactive (22)Na as a tracer for NaCl diffusion in meat; it is concluded that the method is promising for studying salt diffusion in meat.     

1H and 23Na MRI studies of Atlantic salmon (Salmo salar) and Atlantic cod (Gadus morhua) fillet pieces salted in different brine concentrations

BACKGROUND: Applicability of magnetic resonance imaging (MRI) to quantitative analysis of sodium in salted fish products is usually impaired by the partial ²³Na MRI ‘invisibility’ phenomena as well as high investment costs of the MRI equipment. RESULTS: Salmon and cod fillet pieces, unsalted and brine salted (50, 100, 150, 200 and 250 g kg^?1 NaCl) for 48 h, were studied using ¹H and ²³Na MRI. Based on MRI results, T₁ and T₂ relaxation times were calculated for ¹H and the T₂ time for ²³Na nuclei. In addition, water diffusion images for all fillet samples and reference brine solutions were obtained. Variation of the nuclear magnetic resonance relaxation times and water diffusion constants with brine concentration is discussed in terms of the muscle structural changes. Sodium MRI visibility factors for the MRI method used were determined for all fish samples. CONCLUSION: Observed changes in proton and sodium NMR relaxation times with the salt content reflect complex counteraction of several factors related to the muscle structural changes. Sodium MRI visibility factors appear to be dependent on a number of experimental factors in a complex matter, making quantitative sodium analysis by the MRI technique used non‐trivial. Copyright © 2007 Society of Chemical Industry     

Dietary tea catechins and iron-induced lipid oxidation in chicken meat, liver and heart

The aim of the research was to determine water binding and holding capacity and to measure the force and work of penetration of minced pork and beef cured with brine of varying concentrations of sodium chloride and lactic acid and then heated. M. biceps femoris was cut out from chilled pork and beef carcasses three times from each species. Minced meat was subjected to curing. Each of the 20 experimental treatments resulted from appropriate combinations of salt (0.0-2.0%) and lactic acid (0.0-1.5%). The individual concentrations of these two compounds differed by 0.5%. The addition of the curing brine containing only sodium chloride or only lactic acid caused an increase of water holding and binding capacity. The additions of curing brines containing various concentrations of mixtures of salt and acid cause lowering of water holding and binding capacity. Higher penetration force and work had to be applied for pork than for beef samples. With the increase of salt and lactic acid concentrations applied together, after the initial increase of the penetration force and work, their values were found to decrease at higher concentrations of mixtures of these substances in meat.     

Zn-porphyrin formation in cured meat products: Effect of added salt and nitrite

Zn-porphyrin (Zn-pp) was quantified by fluorescence spectroscopy in the cured and dry cured meat products: Parma ham, Iberian ham, dry-cured ham with added nitrite, cooked ham with added nitrite, raw ham meat, raw bacon and Karree-Speck. The highest amount of Zn-pp was found in dry-cured Parma ham and Iberian ham, while the use of nitrite as curing agent was found to inhibit completely the formation of Zn-pp in meat products. A positive correlation between both Zn content and Fe content and the logarithmic transformed Zn-pp content (measured as fluorescence intensity I_fl) was found for the different cured and dry cured meat products, with correlation coefficients of 0.79 (p < 0.001) and 0.71 (p < 0.01), respectively. Log I_fl correlates best with the Zn content, indicating that the formation of Zn-pp is proportional to the Zn content. A model system with vacuum packed pork in brine with different added levels of sodium chloride with or without nitrite and Zn acetate was investigated in order to further elucidate the mechanism of Zn-pp formation. Zn-pp increased with time (up to 42 days investigated) in non-cured meat and for meat cured solely with NaCl lower than 9%. Addition of nitrite or Zn(II) in the curing brine was found to inhibit formation of Zn-pp confirming the observations from the various cured meat products. It is suggested that a chloride anion assisted dissociation of iron from myoglobin could be rate-determining for Zn-pp formation in meat products.     

The effect of selected functional additives and heat treatment on nitrosamine content in pasteurized pork ham

The influence of pasteurization and sodium chloride, sodium ascorbate, polyphosphates and sodium nitrite coupled with pasteurization on nitrosamine contents in pork was studied. Nitrosamines: dimethylonitrosamine (DMNA) and diethylonitrosamine (DENA) were extracted from raw material, distilled, condensed in an evaporator under lowered pressure and analyzed chromatographically. An inhibitory effect of NaCl and sodium ascorbate on volatile nitrosamines (DMNA and DENA) was seen. Adding solutions of polyphosphates to the meat caused a slight increase in nitrosamine contents, higher than noted with sodium chloride. The effect of these compounds on nitrosamine formation depended on the presence of polyphosphates and sodium nitrite in the brine. If the brine contained nitrites, the adverse effect of sodium ascorbate and NaCl on nitrosamine formation was weaker. Moreover, a strong inhibitory effect of pasteurization on DMNA and DENA formation was observed.     

Influence of high intensity ultrasound application on mass transport,microstructure and textural properties of pork meat (Longissimus dorsi) brined at different NaCl concentrations

The aim of this work was to evaluate the effect of high intensity ultrasound and NaCl concentration on the brining kinetics (5 ± 1 °C) of pork loin as well as its influence on the textural and microstructural changes. In order to identify the effect of both factors on NaCl and moisture transport, kinetics were analyzed by taking the diffusion theory into account. The textural and microstructural analysis of raw and brined meat both with and without ultrasound application was carried out. The experimental results showed that the brine NaCl concentration not only determined the final NaCl content in meat samples but also the direction of water transport. The NaCl and moisture effective diffusivities were improved by ultrasound application. The final NaCl and moisture content and the ultrasound application promoted changes in instrumentally measured meat texture, which were confirmed via microstructural observations.     

Histological Changes in Collagen Related to Textural Development of Prawn Meat During Heat Processing

Heat processing enhanced firmness and degree of shrinkage deformation of kuruma prawn Penaeus japonicus meat. In histological experiments, most collagen fiber in perimysium, epimysium, and subcuticular connective tissue maintained structures after heat-processing in hot water at 70°C for 30 min. Crude collagen fiber fractions (residues after alkali extraction, RS-AL) prepared from the muscle were measured for hot-water solubility and compared with the RS-AL from the muscle of carp Cyprinus carpio. Collagen in the RS-AL of prawn muscle had very low hot-water solubility (about 23.5% at 70°C) compared with that of carp. These results suggested that collagen had important functions in promoting thermal shrinkage and hardening of prawn meat and in maintaining mechanical strength of heat-processed meat.     

Heme pigment content in meat as affected by the addition of curing agents

The effects of curing agents on the content of heme pigments (HP) in meat were examined. Minced porcine skeletal muscle was treated with NaCl, NaNO(2) and sodium ascorbate (NaAsA), separately or in combination, and stored at 2-3°C for 7 days. HP content decreased with increase in NaCl concentration and the decrease was about 50% and 80% at NaCl concentrations of 2% and 10%, respectively. Two percent NaCl prevented HP destruction, when previously mixed with 100 ppm NaNO(2) or 0·1% NaAsA. Although some decrease in HP content was noted following application of a mixture of NaCl, NaNO(2) and NaAsA, it was essentially the same as that of the control during 7 days of refrigerated storage. In a model solution containing the same curing agents as those applied to the meat. NaCl had no effect and myoglobin (Mb) content remained constant during storage. From the present results, endogenous muscle constituents appear to act in concert with NaCl to bring about a decrease in HP content.     

Survival of Escherichia coli O157:H7 in meat product brines containing antimicrobials

Brine solution injection of beef contaminated with Escherichia coli O157:H7 on its surface may lead to internalization of pathogen cells and/or cross-contamination of the brine, which when recirculated, may serve as a source of new product contamination. This study evaluated survival of E. coli O157:H7 in brines formulated without or with antimicrobials. The brines were formulated in sterile distilled water (simulating the composition of freshly prepared brines) or in a nonsterile 3% meat homogenate (simulating the composition of recirculating brines) at concentrations used to moisture-enhance meat to 110% of initial weight, as follows: sodium chloride (NaCl, 5.5%) + sodium tripolyphosphate (STP, 2.75%), NaCl + sodium pyrophosphate (2.75%), or NaCl + STP combined with potassium lactate (PL, 22%), sodium diacetate (SD, 1.65%), PL + SD, lactic acid (3.3%), acetic acid (3.3%), citric acid (3.3%), nisin (0.0165%) + ethylenediamine tetraacetic acid (EDTA, 200 mM), pediocin (11000 AU/mL) + EDTA, sodium metasilicate (2.2%), cetylpyridinium chloride (CPC, 5.5%), or hops beta acids (0.0055%). The brines were inoculated (3 to 4 log CFU/mL) with rifampicin-resistant E. coli O157:H7 (8-strain composite) and stored at 4 or 15 °C (24 to 48 h). Immediate (0 h) pathogen reductions (P < 0.05) of 1.8 to ≥ 2.4 log CFU/mL were observed in brines containing CPC or sodium metasilicate. Furthermore, brines formulated with lactic acid, acetic acid, citric acid, nisin + EDTA, pediocin + EDTA, CPC, sodium metasilicate, or hops beta acids had reductions (P < 0.05) in pathogen levels during storage; however, the extent of pathogen reduction (0.4 to > 2.4 log CFU/mL) depended on the antimicrobial, brine type, and storage temperature and time. These data should be useful in development or improvement of brine formulations for control of E. coli O157:H7 in moisture-enhanced meat products. PRACTICAL APPLICATION: Results of this study should be useful to the meat industry for developing or modifying brine formulations to reduce the risk of E. coli O157:H7 in moisture-enhanced meat products.     

The effects of salt concentration on conformational changes in cod (Gadus morhua) proteins during brine salting

The effects of different salt concentrations (6%, 15%, 18% and 24% NaCl (w/w)) on the conformational changes of cod muscle proteins during brine salting were examined in this study. Proteins were extracted from the brine salted samples with solutions of 1 M (5.9%) and 4 M (23.4%) NaCl and the quantity of salt soluble proteins (SSP), disulfide bond (S–S), total sulfhydryl (SH) and available SH content in the soluble fraction were determined. Increased salt concentration in cod muscle promoted protein denaturation and aggregation. The SSP and total SH content decreased, whereas the S–S bond and available SH content increased with increased salt concentration in cod muscle. Disulfide bond formation correlated (r = −0.6) with a decrease in total SH groups. Higher SSP and available SH groups of the samples at lower brine concentrations was explained by smaller concentration gradients and salt diffusion rates, resulting in stronger salting-in at early stages of the brining process. There was a significant difference in conformational changes in proteins extracted with a salt solution of 1 and 4 M, mainly due to a different degree of protein aggregation.     

Spermine and spermidine concentrations in pork loin as affected by storage, curing and thermal processing

Spermine and spermidine concentrations in pork loin as affected by three factors used in food processing [immersion-curing (10% brine: NaNO₂ and NaCl content of 0.6 and 99.4 g/l, respectively, and 20% brine: NaNO₂ and NaCl content of 0.6 and 199.4 g/l, respectively), boiling and grilling (70 °C core temperature) and storage of raw loin chops (“non-stored” versus storage at 4 °C for 5 days)] were studied. Spermidine and spermine concentrations of the “non-stored” raw loin chops were 2.7±0.7 and 19.8±1.5 mg/kg (fresh weight), respectively. Storage effects were negligible. Curing in 20% brine resulted in statistically significant spermidine decreases as compared to non-cured meat (p=0.04). Statistically significant decreases of spermine were observed for curing in 20% brine as compared with 10% brine (p=0.08), and boiling of meat in an equal amount of water compared to raw meat and grilled meat (p=0.03). Combined curing in 20% brine and cooking in an equal amount of water resulted in 2.0±1.0 mg/kg spermidine and 14.4±2.6 mg/kg spermine. Combined common food processing techniques resulted in a decrease of spermine and spermidine concentrations in pork loin of maximum 26% only. The latter should be considered as relevant for consumers for which the dietary polyamine uptake is critical.     

Ultrasound assisted diffusion of sodium salt replacer and effect on physicochemical properties of pork meat

In an attempt to reduce the high intake of dietary salt, the processed meat industry is continuously looking for alternative solutions for salt replacement. The objective of this study was to investigate the effect of employing sonication on the diffusion of sodium salt (NaCl) and a salt replacer (SR) into pork meat. Ultrasound‐assisted brining experiments were carried out using 5% NaCl or SR at power levels of 9.0 and 54.9 W cm^?2 for 120 min. Samples were assessed for cooking loss, water mobility, deformation, while thermal behaviour was analysed using differential scanning calorimetry (DSC). Experimental data obtained were used to estimate the mass transfer coefficient of the brining process. The mass transfer equation was solved using the Runge–Kutta method. Results showed that the ultrasonic treatment had a low influence on the mass transfer of salt into pork samples. Only at high ultrasonic power was the mass transfer coefficient higher than the static brining. This study has improved our understanding of the effect of sonication on diffusion of NaCl and SR in pork meat and will enable a more systemic approach to future healthy meat product development.     

Measurement of effective diffusivities of ionic and non-ionic solutes through beef and pork muscles using a diffusion cell

A diffusion cell in conjunction with a new mathematical model was used to measure the apparent diffusion coefficients of sodium chloride, potassium nitrate and glucose through beef semitendinosus and pork longissimus dorsi muscles. The apparent diffusion coefficient was obtained within less than 180 min with a coefficient of variation less than 10% in most cases. The influence of temperature can be adequately explained by the Arrhenius-type law with activation energy between 19 and 26 kJ/mol depending on the diffusant. However, these values were not significantly different. Finally, we showed that the apparent diffusion coefficient of sodium chloride is not affected by the direction of the muscle fibre to the axes of diffusion while glucose diffusion parallel to the muscle fibre can be three times greater than diffusion at a right angle to the muscle fibre.     

Beef sausage structure affected by sodium chloride and potassium lactate

A histological and ultrastructural study was conducted to characterize changes in the muscle fibre structure of three fresh sausage preparations, depending on meat composition, sodium chloride (NaCl) and potassium lactate (K-lactate) contents. After addition of 0.8% and 1.6% NaCl, 65% and 51%, respectively, of the area observed showed well preserved fibres (histological data). The altered regions presented a large disorganization of the myofilaments and a solubilization of the sarcolemma and of the Z lines. K-lactate addition had no marked effects on meat structure. The preparation containing some sheep meat was more sensitive to salt than the others containing only bovine meat. The level of alteration was much lower than those obtained in pork meat in another study. Technological conditions used to modify the internal muscle fibre structure during sausage processing depend on the species used. Therefore, the classification of the sausage preparation to “meat preparation” or “meat product” under the EU regulation (EC) No. 853/2004 (which assign meat preparations to meat if the product has undergone a process insufficient to modify the internal muscle fibre structure of the meat) must be systematically controlled when changing the meat sausage composition.     

Beef sausage structure affected by sodium chloride and potassium lactate

A histological and ultrastructural study was conducted to characterize changes in the muscle fibre structure of three fresh sausage preparations, depending on meat composition, sodium chloride (NaCl) and potassium lactate (K-lactate) contents. After addition of 0.8% and 1.6% NaCl, 65% and 51%, respectively, of the area observed showed well preserved fibres (histological data). The altered regions presented a large disorganization of the myofilaments and a solubilization of the sarcolemma and of the Z lines. K-lactate addition had no marked effects on meat structure. The preparation containing some sheep meat was more sensitive to salt than the others containing only bovine meat. The level of alteration was much lower than those obtained in pork meat in another study. Technological conditions used to modify the internal muscle fibre structure during sausage processing depend on the species used. Therefore, the classification of the sausage preparation to “meat preparation” or “meat product” under the EU regulation (EC) No. 853/2004 (which assign meat preparations to meat if the product has undergone a process insufficient to modify the internal muscle fibre structure of the meat) must be systematically controlled when changing the meat sausage composition.     

Influence of sodium replacement on the salting kinetics of pork loin

The partial replacement of sodium chloride by other salts has been proposed as a possible strategy to reduce the sodium content of cured meat products. Nevertheless, there is very little knowledge as regards the influence of salts other than sodium chloride on salting kinetics.The aim of this study was to evaluate the effect brought about by substituting sodium chloride with potassium, calcium and magnesium chloride on the salting kinetics of dry cured loins. The results showed very important changes in the salting pattern depending on the type of salts. Partial substitution of sodium affected both water and ion transport during the salting process. The presence of KCl decreased water loss while CaCl₂ and MgCl₂ had the opposite effect. However, replacement of up to 50% NaCl by KCl had no significant effect on the salting kinetics in the case of the control formulation. Calcium and magnesium cations penetrated with difficulty into the muscle remaining in the brine formed during the pile salting process. Moreover, the presence of calcium and magnesium cations considerably reduced the sodium and potassium content of the salted loin.