Meat Science 96 (2014) 65–72

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Salt uptake and water loss in hams with different water contents at thelean surface and at different salting temperatures

Núria Garcia-Gil, Israel Muñoz, Eva Santos-Garcés, Jacint Arnau, Pere Gou ⁎IRTA, Institut de Recerca i Tecnologia Agroalimentàries, Food Technology, XaRTA, Finca Camps i Armet, E-17121 Monells, Girona, Spain

⁎ Corresponding author. Tel.: +34 972 630 052; fax:E-mail address: pere.gou@irta.cat (P. Gou).

0309-1740/$ – see front matter © 2013 Elsevier Ltd. Allhttp://dx.doi.org/10.1016/j.meatsci.2013.06.012

a b s t r a c t

a r t i c l e i n f o

Article history:Received 11 April 2013Received in revised form 6 June 2013Accepted 10 June 2013

Keywords:Salt uptakeDry-cured hamSurface water contentTemperature

The salt uptake homogeneity is crucial in assuring quality in dry-cured hams. The aim of this study was to eval-uate the effect of the water contents at the lean surface before salting and of the temperature during salting onthe salt uptake. Pieces of loin stored at 3 °C for 3 days before salting absorbed less salt through a surface that hasbeen dried during storage. A group of raw hams were subjected to different pre-salting storage times (0, 3 and6 days) and another group subjected to different set room temperatures during salting (−1.0, 0.5 and 4.0 °C).The duration of storage before salting and the temperature during salting had a negative and a positive effecton the average salt absorption, respectively. The most important effects appeared after 6 days of storage andat 4 °C. No significant differences in salt uptake homogeneity were found between storage times and betweensalting temperatures.

© 2013 Elsevier Ltd. All rights reserved.

1. Introduction

In Mediterranean countries, the traditional elaboration process ofdry-cured ham has three fundamental stages: dry-salting, resting anddrying/ageing. During the salting stage, the amount of salt absorbed bythe hams is often highly variable. The amount of salt affects the dryingprocess (Comaposada, Gou, & Arnau, 2000; Gou, Comaposada, & Arnau,2003) and the biochemical reactions during thewhole process, e.g. prote-olysis (Arnau, Guerrero, & Gou, 1997; Arnau, Guerrero, & Sárraga, 1998;Martín, Antequera, Córdoba, Timón, & Ventanas, 1998; Morales, Serra,Guerrero, & Gou, 2007) and lipolysis (Andrés, Cava, Ventanas, Thovar, &Ruiz, 2004; Andrés, Cava, Martin, Ventanas, & Ruiz, 2005), which are inpart responsible for the quality of the dry-cured ham. Therefore, the var-iability in the salt absorption causes heterogeneous behaviour of the hamsthroughout the next stages of the process, hindering their control, andobtaining final products with heterogeneous sensory and nutritionalcharacteristics which could also negatively influence the purchase deci-sion of consumers.

There is a current tendency to reduce the salt content in dry-curedhams in linewith the recommendations from theWorldHealthOrganiza-tion to reduce sodium dietary consumption (World Health Organization—WHO, 2003). However, the reduction of added salt, without a previousreduction of the variability in salt absorption, results in a higher percent-age of hams showing both quality and microbial stability problems dueto insufficient salt content.

Salting can be explained as a two phase process. In the first phase,NaCl is dissolved on the ham surface which results in brine formation

+34 972 630 980.

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(Raoult-Wack, 1994) but some water on the lean surface is necessaryto initiate the salting process. In the second phase, the Cl− and Na+

ions from the brine diffuse towards the internal part of the meat(Costa-Corredor, Muñoz, Arnau, & Gou, 2010; Djevel & Gros, 1988;Fox, 1980; Sabadini, Carvalho, Sobral, Do, & Hubinger, 1998). Factorsaffecting these two phases are therefore expected to contribute tothe salt uptake heterogeneity.

Before salting, hams are stored in cold rooms for different periodsof time (from hours to several days) due to differences in transportand processing time schedules. The duration and the conditions ofstorage until salting may affect the water content at the lean andrind surfaces, which in turn could affect the salt uptake during salting.Moreover, the temperature and relative humidity of the salting roomcan also affect the hydration level of NaCl.

Temperature during salting is set below 5 °C to reduce microbiolog-ical growth, but over 0 °C to avoid freezing. Although temperature ismaintained within a narrow range of values, temperature variationcan also contribute to the salt uptake variability.When the temperatureof the salt in the salt pile is below 0.15 °C and thewater contained in thesalt-water mixture is below 38.1%, the NaCl hydrates and crystals ofNaCl · 2H2O are formed (Hall, Sterner, & Bodnar, 1988). The formationof these crystals on the lean surface of the hams can affect salt absorp-tion. The temperature also affects the salt diffusion in the meat matrix(Djevel & Gros, 1988; Fox, 1980; González-Méndez, Gros, & Poma,1983). However, the above studies were focused on a higher range oftemperatures (from 3 °C to 40 °C) which represent only a part of thetemperatures used during the salting process. The effect of tempera-tures closer to the freezing point of meat (−1.5 °C) (James, Lejay,Tortosa, Aizpurua, & James, 2005), which produces the maximum re-duction in bacterial growth in fresh meat, has not yet been studied.

66 N. Garcia-Gil et al. / Meat Science 96 (2014) 65–72

The aim of this study was to evaluate the effects of both the watercontent at the lean surface before salting and the temperature duringsalting on salt uptake and water loss (both on average values andstandard deviations) in hams.

2. Materials and methods

Three independent studies were performed in order to evaluatethe effect of both the water content at the lean surface (Experiment1 with loins, as a model of ham, and Experiment 2 with hams) andthe temperature during salting (Experiment 3 with hams) on salt up-take and water loss.

The storage times before salting applied in Experiment 2 as well asthe temperatures during salting applied in Experiment 3 were set tocomply with the range of values obtained in a survey carried out at20 dry-cured ham companies of Protected Designation of Origin(PDO) Teruel (Pérez-Beriain, 2012).

2.1. Experiment 1. Effect of water content at the surface of loins on saltuptake and water loss.

Four pork loins from different animals were obtained from a com-mercial slaughterhouse at 24 h post-mortem. Each loin was longitudi-nally divided into six pieces of 50 mm length, forming three pairs ofadjacent pieces (Fig. 1). Two pieces of 20 mm length from each loinwere also obtained to determine the basal NaCl content (0.25 ±0.01%). For each pair of pieces, the area of the adjacent surfaces was cal-culated by averaging the two surface areas estimated using Image-Pro®

12 piece

12 piece

(surfac

Drying l

ventilatio

Water content determination of the adjaSpectroscopy

Contro

Adjac

Surface

Dry-salting for 1, 2, 4 or 7 days (at 3-5 ºCof the adjacent loin surfaces with the salt

24 loin pieces

(50 mm length)

NaCl content determinations of the w

Fig. 1. Experimental desi

Plus software (2008 ©Media Cybernetics). One piece from each pairwas completelywrappedwith 3 layers of a food grade PVC film (polyvi-nyl chloride, 9 μm thick, water-vapour transmission rate 200 g/m2/24 h at 38 °C and 90% RH (ASTM, 1995); Macopal, S.L., Lliçà de Vall,Spain) (control, C); while the other piece was also wrapped except forthe adjacent surface (surface-dried, D), where most of the water losswas expected to occur. The loin pieces were stored together at 3–5 °C,60–70% relative humidity and constant ventilation for 3 days. In orderto stress differences in surface water content between C and D loinpieces, a ventilation of 3 m/s during storage was applied. Thereafter,the adjacent surfaces of C loin pieces were unwrapped and the watercontent at the adjacent surfaces of C and D loin pieces were determinedby means of Near Infrared Spectroscopy (NIR) (Collell, Gou, Arnau, &Comaposada, 2011). All the loin pieces were dry-salted through theiradjacent surfaces by contact with dry salt (4.7 ± 0.17% moisture) in acold room at 3–5 °C and 80–90% relative humidity. Groups of threepairs of loin pieces were salted for 1, 2, 4 and 7 days. At the end of salt-ing, the loin pieceswere individuallyminced to determine their salt andwater contents. The weight of the loin pieces was recorded when fresh,after 3 days of storage (just before salting) and after salting.

Salt uptake (Ms, kg NaCl/m2) was calculated with Eq. (1):

Ms ¼S�Was−Sb �Wf

� �=100

Að1Þ

where, S (%) is the NaCl content after salting, Sb is the basal NaCl con-tent (0.25%), W (kg) is the loin piece weight when fresh (f) or aftersalting (as) and A (m2) is the area of adjacent surface.

s wrapped with film (control loins)

s with one of the surfaces uncovered

e-dried loins)

evels (3-5 ºC, 60-70% RH and constant

n for 3 days):

cent loin surfaces by Near Infrared

l loins

ent surfaces

-dried loins

and 80-90% RH) by contact

Salt

hole lean tissue

gn for Experiment 1.

67N. Garcia-Gil et al. / Meat Science 96 (2014) 65–72

Water loss during salting (Mw, kg H2O/m2) was calculated withEq. (2):

Mw ¼ Wbs−Was

AþMs ð2Þ

where,W (kg) is the weight of the loin piece just before salting (bs) orafter salting (as), Ms is the salt uptake (kg NaCl/m2) and A (m2) is thearea of adjacent surface.

In order to show the drying effect at different depths, water con-tent profiles in C and D loin pieces of two additional loins just beforesalting were determined. Three pairs of pieces 50 mm length wereobtained from each loin, wrapped and dried as explained aboveresulting 6 C and 6 D loin pieces. After drying, each piece was slicedresulting in five slices 10 mm thick. Slice 1 was the one correspondingto the adjacent surface and slice 5 to the opposite surface. Each slicewas minced and the water content was determined.

2.2. Experiment 2. Effect of storage conditions of hams before salting onsalt uptake.

Hams from twenty-one carcasses were obtained from a commer-cial slaughterhouse, associated to PDO Teruel, at 24 h post-mortem.The weight of hams and the pH, measured on the Semimembranosusmuscle, were recorded. The weight ranged from 11.20 to 12.72 kgand the pH value from 5.57 to 6.19. The hams were stored in a coldroom at 3–5 °C, 70–80% relative humidity and constant ventilationfor 0, 3 or 6 days according to the experimental design shown inTable 1. In order to stress time-induced variations in surface watercontent between hams, a ventilation of 3 m/s during storage was ap-plied. After storage, the surface water content at the lean tissue wasdetermined by means of NIR (Collell et al., 2011).

The hams were processed according to the specifications of PDOTeruel (Boletín Oficial del Estado, 1993). In brief, immediately aftereach storage time, a mixture containing 0.3 g of KNO3, 0.5 g ofNaNO2, 0.5 g of sodium ascorbate and 10 g of fine NaCl per kg ofham was applied to the surface by rubbing. Thereafter, the hamswere covered with coarse salt in a pile consisting of three levels andleft in a cold room at 3–5 °C and 80–90% relative humidity for12 days. The hams from each storage time were uniformly distributedbetween the three levels in the salt pile. Pairs of hams from the samecarcass were placed at the same level in the salt pile. After salting, thehams were washed with water at 12 °C to remove excess salt andkept at 3–5 °C and 80–90% relative humidity for 65 days (resting).After resting, the hams were boned and the lean tissue was mincedto determine both salt and water contents to calculate the salt con-tent (%) on a dry matter basis, which was considered as an estimateof the salt uptake. Weight gain due to salt uptake (WGs,%) of thehams was calculated with Eq. (3):

WGs ¼S�War

Wbsð3Þ

where, S (%) is the NaCl content after resting and W (kg) is the hamweight before salting (bs) or after resting (ar).

Table 1Experimental design for Experiment 2. The pairs of hams (P) from the same carcass(1 to 21) were subjected to different storage times before salting according to anuncompleted block design.

Storage time before salting

0 days 3 days 6 days

(n = 14) (n = 14) (n = 14)

P1–P7 P1–P7 P8–P14P15–P21 P8–P14 P15–P21

Computed Tomography (CT) was used to estimate the salt contentin three zones of the Biceps femoris muscle of 18 hams from 9 car-casses (6 hams for each storage time): the inner zone (5 mm widthand 25 mm height as reported by Santos-Garcés, Muñoz, Gou, Sala,& Fulladosa, 2012) and two zones (20 mm width and 10 mm heighteach one) adjacent to the subcutaneous fat and close to Vastusmedialis and Semitendinosus muscles. These salt determinationswere performed at different stages of the process: after salting (day 12),halfway through and at the end of the resting period (days 35 and 65).CT was also used to determine both the maximum thickness and widthof a central slice after storage at the same stages of the processmentionedabove.

The weight of the hams was recorded at different time points ofthe process: when fresh, after storage, after salting and at the end ofresting. The weight losses after storage and salting are referred tothe weight of the fresh hams. The weight loss at the end of restingis referred to the weight of the hams when fresh as well as to theweight of the hams after storage (just before salting). The estimatedweight loss due to the water loss (WLw, %) during salting was calcu-lated with Eq. (4):

WLw ¼ WGs þ 100�Wbs−Was

Wbsð4Þ

where,WGs (%) is the weight gain due to salt uptake andW (kg) is theham weight before salting (bs) or after salting (as). It was assumedthat the lean, rind and bones contained the same NaCl content,although it is known that NaCl is higher in the rind and lower in thebones compared to the lean (Boadas, Gou, Valero, & Arnau, 2000).

2.3. Experiment 3. Effect of salting temperature on ham salt uptake.

Hams from eighteen carcasses were obtained from a commercialslaughterhouse, associated to PDO Teruel, at 24 h post-mortem. Theweight of hams and the pH, measured on the Semimembranosus mus-cle, were recorded. The weight ranged from 11.47 to 12.97 kg and thepH value from 5.37 to 6.12. The hams were rubbed with a mixturecontaining 0.3 g of KNO3, 0.5 g of NaNO2, 0.5 g of sodium ascorbateand 10 g of fine NaCl per kg of meat. Thereafter, the hams were cov-ered with coarse salt in a pile consisting of three levels and left for12 days in three different cold rooms at 80–90% relative humidityand at different set room temperatures (−1.0 °C, 0.5 °C or 4.0 °C)according to the experimental design shown in Table 2. Before salting,the salt piles were kept in the corresponding cold rooms until theyachieved the target temperatures. The pairs of hams from the samecarcass were placed at the same level in the salt piles. The tempera-ture of each salt pile was recorded at 20 cm below the pile surfaceduring the salting process with a CRISON TM 65 probe (CRISONInstruments S.A., Alella, Spain). The temperatures of the salting pileswere −0.95 ± 0.09 °C, 0.44 ± 0.19 °C and 4.18 ± 0.33 °C for thecold rooms set at−1.0 °C, 0.5 °C and 4.0 °C, respectively. After salting,the hams were processed as in Experiment 2.

CT was also used to estimate the salt content of the inner zone ofthe Biceps femoris in 18 hams from 9 carcasses (6 hams for each saltingtemperature) (Santos-Garcés et al., 2012). These salt determinations

Table 2Experimental design for Experiment 3. The pairs of hams (P) from the same carcass(1 to 18) were salted at different room temperatures according to an uncompletedblock design.

Temperature during salting

−1 °C 0.5 °C 4 °C

(n = 12) (n = 12) (n = 12)

P1–P6 P1–P6 P7–P12P13–P18 P7–P12 P13–P18

Table 3Water content mean values (%) and standard deviation (SD) measured by the traditionalmethod (AOAC, 1990) of different slices (10 mm thick) from the control (C) and surface-dried (D) loin pieces before salting.

Slices C loin pieces (n = 6) D loin pieces (n = 6)

1 73.4a ± 0.6 65.7b ± 1.42 73.2 ± 0.9 72.4 ± 0.93 73.1 ± 0.9 73.0 ± 0.64 73.1 ± 0.4 73.3 ± 0.95 72.8 ± 0.5 73.3 ± 1.0

a,bMeans within a row without a common letter are significantly different (P b 0.05).Tukey's test.

68 N. Garcia-Gil et al. / Meat Science 96 (2014) 65–72

were performed halfway through and at the end of the resting period(days 35 and 65).

2.4. Near Infrared Spectroscopy analysis

At the end of the storage previous to salting, water content at thelean surface of both loin pieces (Experiment 1) and raw hams (Exper-iment 2) was measured by Near Infrared Spectroscopy (NIR). The NIRequipment used was a remote measurement head Q410/A Nema 4(Bruker Optik GmbH, Ettlingen, Germany). Loin pieces and hamswere scanned at four areas of the lean surface avoiding the fat andthe connective tissue. The spectra acquisition and water content pre-diction were performed according to Collell et al. (2011).

2.5. Computed Tomography (CT) analysis

CT analysis was performedwith a HiSped Zx/i scanner from GeneralElectric Healthcare (GE Healthcare, Barcelona, Spain). An axial protocolwas applied with the setting at 80 and 120 kV, 250 mAs and with a ro-tation time of 2 s. Image size was 512 × 512 voxels and displayed fieldof view (DFOV) was 461 mm. One 10 mm thick slice was scanned at100 mm from the aitch bone in the distal direction throughout the dif-ferent stages of the process as described by Garcia-Gil et al. (2012). Im-ages were reconstructed applying the algorithm STD + from GeneralElectric and analysed to predict salt content using the mathematicalmodel published by Fulladosa, Santos-Garcés, Picouet, and Gou(2010). This model was obtained from samples at temperatures of3 ± 2 °C.

2.6. Water content and chloride content analyses

Water content was determined by drying at 103 ± 2 °C untilreaching constant weight (AOAC, 1990). Chloride content was deter-mined according to ISO 1841–2 (1996) using a potentiometric titrator785 DMP Titrino (Metrohm, Herisau, Switzerland). All analyses wereperformed in duplicate.

2.7. Statistical analysis

Data were analysed for each experiment by means of ANOVAusing the GLM procedure of SAS (2008). The linear models includedas fixed effects: the storage time (0 or 3 days) and the pair of loinpieces for Experiment 1; the storage time (0, 3 or 6 days) and thecarcass for Experiment 2; the set temperature in cold rooms duringsalting (−1.0, 0.5 or 4.0 °C) and the carcass for Experiment 3. The dif-ferences between means were tested by Tukey's test and the homo-geneity of variances (differences between standard deviations) byLevene's test.

3. Results and discussion

3.1. Experiment 1. Effect of water content at the surface of loins on saltuptake and water loss

After the three days of storage previous to salting, the weight losseswere significantly lower in the control loin pieces (C) (3.66 ± 1.87%)than in the surface-dried loin pieces (D) (8.40 ± 1.97%). These differ-ences inweight lossmust have beendue towater loss and produced dif-ferences in water content, especially at the surface (Table 3). D loinpieces showed lower water content at the surface (10 mm depth) incomparison to C loin pieces. The water content at the surfacemeasuredwith NIR (ca. 2 mm depth) (Collell et al., 2011) showed even more im-portant differences between C loin pieces (71.5 ± 3.2%) and D loinpieces (51.7 ± 3.3%).

C loin pieces showed higher water loss (Mw) and salt uptake (Ms)during salting than D loin pieces at any salting time (Table 4).

According to Fick's law, the diffusion of a component in a given foodmatrix depends on both its content gradient and its diffusivity coeffi-cient. In the case of NaCl diffusion, Gou et al. (2003) proposed the gra-dient of NaCl/water ratio as the driving force for salt diffusion. At thebeginning of salting, D loin pieces had lower water content at the sur-face than C loin pieces, resulting in higher gradients of water andNaCl/water ratio between the inner and the outer part of the loinpieces, which was expected to increase the water flow from insideto outside and the NaCl flow from outside to inside. However, manystudies have proven that the water diffusivity (Dw) coefficient inmeat decreases when water content decreases (Gou, Comaposada, &Arnau, 2004; Okos et al., 1992; Ruiz-Cabrera, Gou, Foucat, Renou, &Daudin, 2004), slowing down the water flow. Similarly, it has beenreported that the salt diffusivity (Ds) coefficient in meat diminisheswhen water content decreases (Costa-Corredor, Pakowski, Lenczewski,& Gou, 2010), also slowing down the salt flow. In D loin pieces, theexpected negative effect of the lower water content on both the Dw

and Ds coefficients could have been more important than the expectedpositive effect of the water content at the surface on the water andNaCl/water ratio gradients. Contrarily, the importance of the positiveeffect of the water content at the surface could have been higher thanthe importance of the negative effect of the water content in C loinpieces.

There was a positive relationship between the Ms and Mw duringsalting in C loin pieces (Fig. 2), which would indicate that bothmass transfers were driven by some common factors (i.e. same sur-face area of exchange, same length of samples, same structure andthe relationship between water and salt/water ratio gradients). How-ever, the relationship between the Ms and Mw during salting was notclearly observed in D loin pieces. At the beginning of salting (twodays), although they had lost water, the salt uptake had not increased.This could be related to the fact that it is necessary to dissolve NaCl inorder to form the brine at the loin surface before the Cl− and Na+ ionscan diffuse from the brine towards the internal part of the loin. There-fore, enough water on the lean surface is needed to initiate the saltingprocess. The low amount of water (Mw) supplied by the D loins beforetwo days of salting might not have been enough to form the brine andso the salting process was delayed. Despite the fact that the salt crys-tals were removed, the presence of some salt crystals stuck on thesurface after salting, which was independent of the salting time,would explain the slight increase in the salt uptake detected for thefirst two days of salting in D loin pieces. These crystals would haveremained in the sample when mincing for chemical analysis.

After 7 days, the salt uptake was approximately 70% more in C loinpieces than in D loin pieces. This result gives an insight into the im-pact of the differences in water content at the loin surface on thesalt uptake homogeneity.

3.2. Experiment 2. Effect of storage conditions of hams before salting onsalt uptake

The water content at the lean surface obtained by NIR (Table 5) in-dicated that the highest decrease of the water content at the lean

Table 4Salt uptake (Ms, kg NaCl/m2) and water loss (Mw, kg H2O/m2) during salting of the Cand D loin pieces subjected to different salting times (1, 2, 4 and 7 days).

Salting time(days)

Ms ± SD Mw ± SD

C loin pieces(n = 3)

D loin pieces(n = 3)

C loin pieces(n = 3)

D loin pieces(n = 3)

1 0.90a ± 0.05 0.16b ± 0.03 2.76a ± 0.07 1.19b ± 0.222 1.25a ± 0.12 0.16b ± 0.01 3.96a ± 0.14 1.78b ± 0.254 1.44a ± 0.15 0.40b ± 0.18 4.87a ± 0.53 2.97b ± 0.357 1.98a ± 0.16 0.63b ± 0.16 7.35a ± 0.38 4.71b ± 0.18

SD, standard deviation.a,bFor each parameter, means within a row without a common letter are significantlydifferent (P b 0.05). Tukey's test.

Table 5Physicochemical traits of the hams from Experiment 2 subjected to different storagetimes before salting throughout different stages of the elaboration process.

Storage time before salting

0 days 3 days 6 days

(n = 14) (n = 14) (n = 14)

Water content at the leansurface (%) ± SD⁎

70.2a ± 1.7 63.4b ± 1.9 62.7b ± 1.7

Weight loss (%) ± SDafter storage

– 1.06b ± 0.22 3.28a ± 0.67

Weight loss (%) ± SDafter salting

5.85b ± 1.43 6.49b ± 1.01 8.37a ± 1.07

Water loss (WLw) ± SDduring salting

9.96 ± 1.41 9.83 ± 1.37 9.35 ± 1.29

NaCl (% DM) ± SD 12.60b ± 1.15 12.98a ± 1.01 11.69c ± 0.92Weight loss (%) ± SDat the end of restingReferred to theweight of fresh hams

17.61 ± 1.87 17.93 ± 1.74 17.36 ± 1.33

Referred to theweight of hams after storage

17.61a ± 1.87 17.05a ± 1.74 14.72b ± 1.47

SD, standard deviation; DM, dry matter.a,b,cLeast square means within a row without a common letter are significantlydifferent (P b 0.05). Tukey's test.⁎ Water content at the lean surface measured by NIR.

69N. Garcia-Gil et al. / Meat Science 96 (2014) 65–72

surface took place during the first 3 days of storage. The decrease ofwater content at the surface from 3 days to 6 days of storage was toosmall to be detected by NIR due to the water content was estimated inthe most superficial zone of the lean (ca. 2 mm depth) (Collell et al.,2011). Considering, on the one hand, the results from the loin assay (Ex-periment 1) and on the other hand, that salt penetrates mostly throughthe lean tissue in hams (Frøystein, Sörheim, Berg, & Dalen, 1989;Garcia-Gil et al., 2012), it was expected that dehydration of the lean sur-face would also have a negative effect on the salt uptake in the hams. Inconcordance with this expectation, the hams subjected to 6 days ofstorage showed a salt content on a drymatter basis (estimate of salt up-take) significantly lower compared to the hams subjected to shorterstorage times. However, the hams stored for 3 days presented thehighest salt content. This behaviour in salt uptake reinforces the expla-nation presented in Experiment 1, i.e., that there are two effects of theinitial water content at the surface on the salt flow from outside to in-side the ham. Decreasingwater content at the surface results in a higherNaCl/water ratio gradient, which could positively affect the salt flow,but at the same time Ds decreases when low water contents areachieved, which could negatively affect the salt flow. The global net ef-fect would depend on the importance of each one. The highest decreasein water content at the surface was achieved during the first 3 days ofstorage, producing the highest increase in the NaCl/water ratio gradientat the beginning of salting. This would explain the highest salt uptake inthose hams. Three additional days of storage only slightly decreased thewater content at the surface (about 2 mm depth), but it must have de-creased the water content in the superficial zone deeper than 2 mm,according to the weight losses shown after storage (Table 5). The

1

4

7

2

1

2

4

7

1

7

2

4

12

7

421

4

7

1

7

2 4

0.00

0.50

1.00

1.50

2.00

2.50

0 2 4 6 8 10

Ms

(kg

NaC

l/m2 )

Mw (kg H2O/m2)

C loin pieces

D loin pieces

Fig. 2. Salt uptake (Ms) versuswater loss (Mw) during salting of both C and D loin piecessalted for different days. For each point the salting days are indicated.

negative effect of the water content reduction in this superficial zoneon the Ds could be more important than the positive effect of the in-creased NaCl/water ratio gradient.

Several studies have reported that water holding capacity (WHC)in meat changes throughout post-mortem time (Huff-Lonergan &Lonergan, 2005; Joo et al., 1995; Kim, Warner, & Kaufman, 1993;Kristensen & Purslow, 2001). In pork meat, Kristensen and Purslow(2001) observed that WHC was lower after 4 days post-mortem com-pared to that observed after 1 day post-mortem. The decrease of WHCduring early post-mortemwas attributed to the outflow of water fromintra- to extracellular compartments due to post-mortem shrinkage.This extracellular allocation of water could cause a higher transferof the superficial water to the salt, resulting in a higher formation ofbrine. This fact could contribute in part to the higher salt uptake ob-served in hams with 3 days of storage.

In spite of the differences in salt uptake, the duration of the stor-age time before salting did not significantly modify the standard devi-ation in salt uptake within a batch of salting (Levene's test was notsignificant).

The differences in width observed before salting could also havecontributed to the different salt uptake behaviour of the hamssubjected to different storage times before salting (Table 6). Duringstorage, the rind lost water and shrunk. Tensions due to the rindshrinkage caused a deformation in the ham shape. This fact was spe-cially observed in the hams stored for 6 days since they showed arounder shape than the hams stored for shorter times (Table 6,Fig. 3). The hams with 0 and 3 days of storage had a flatter shape be-fore salting (Table 6, Fig. 3). A flat shape contributes to keeping brineon the surface for a longer time and could consequently facilitate ionabsorption (Arnau, 2007). Garcia-Gil et al. (2012) also reported thatthe flat shape due to the application of the partial skinning as wellas the pressing before salting could contribute to an increase in thesalt uptake.

The NaCl contents in the Biceps femoris (BF) muscle were deter-mined by CT at three distinct zones and at different stages of the elab-oration process (Table 7). In general, the salt content in the innerzone of BF muscle tended to increase more slowly in hams storedfor 6 days before salting. This was due to the facts that they showeda lower global salt uptake (Table 5) and that the salt absorbed bythe lean surface had to cross a longer distance to reach the BF muscle(Table 6). Additionally, the drier rind shown by these hams could

Table 6Morphometric parameters (maximum thickness and width of a central slice) determined by computed tomography of the hams from Experiment 2 at different stages of the elab-oration process.

Maximum thickness* (cm) ± SD Maximum width* (cm) ± SD

0 days 3 days 6 days 0 days 3 days 6 days

(n = 6) (n = 6) (n = 6) (n = 6) (n = 6) (n = 6)

After storage 15.4 ± 0.7 15.1 ± 0.9 16.3 ± 0.5 30.8a ± 0.8 31.0a ± 1.5 28.3b ± 1.3After salting 13.9 ± 0.5 13.6 ± 0.8 14.4 ± 0.6 32.1 ± 1.4 32.2 ± 1.5 29.8 ± 1.2Mid resting 14.4 ± 0.9 13.8 ± 0.7 15.1 ± 0.7 29.0 ± 2.1 29.9 ± 1.5 27.3 ± 0.8End of resting 14.4 ± 1.0 13.4 ± 0.9 14.9 ± 0.7 27.7 ± 2.1 27.6 ± 1.7 26.8 ± 0.6

SD, standard deviation.a,b,cFor each parameter, least square means within a row without a common letter are significantly different (P b 0.05). Tukey's test.

70 N. Garcia-Gil et al. / Meat Science 96 (2014) 65–72

have reduced the salt absorption by the rind which in turn wouldhave diminished the amount of salt supplied by the rind to the subcu-taneous fat and later to the BF muscle (Boadas et al., 2000). This state-ment can be supported by the lowest amount of salt shown in thezone of BF close to ST of the hams stored for 6 days at the end of rest-ing (Table 7) as well as by the images obtained by CT (zone 3 inFig. 3b and d). The whiter appearance of BF muscle of the hams storedfor 3 days (Fig. 3b) compared with the hams stored for 6 days(Fig. 3d) indicates that the salt content was higher in the former.

It is known that salt has a relevant function on microbiological sta-bility (Baldini, Campanini, Pezzani, & Palmia, 1984; Rastelli, Giraffa,Carminati, Parolari, & Barbuti, 2005). According to the specificationsof PDO Teruel (Boletín Oficial del Estado, 1993), the duration ofresting has to range between 45 and 90 days in order to ensure aNaCl content higher than 1% on a fresh basis in the inner and outermuscles. In this experiment the duration of resting was 65 days. Atday 65, the NaCl content (expressed as % on fresh basis) in thewhole Biceps femorismuscle was higher than 1% in all hams. However,significant differences in NaCl content were observed in the hamssubjected to different storage times (P b 0.05) at the end of resting.Therefore, the different storage times previous to salting and the du-ration of the resting period applied in this study complied with PDOTeruel requirements. Further studies are needed to elucidate whetherthese differences comply with PDO Teruel for NaCl content whenshorter salting and resting times (e.g. 45 days) are applied.

Aftersalting

A. 3 days of storage

End of resting

a

b

1

1

2

2

3

3

ST

SF

BF

VM

Fig. 3. CT cross sections after salting and at the end of resting from one ham after 3 days of(panel B, c–d) from the same carcass. The three zones where the salt content was estimatsubcutaneous fat (SF) and close to the Vastus medialis (VM) muscle and (3) zone adjacent

The hams subjected to 6 days of storage previous to saltingshowed the highest weight loss (WL) after salting because this WL in-cluded the water lost during the storage period (Table 5). They alsoshowed the lowest water loss (WLw) though the difference was notstatistically significant. Hams stored for 6 days showed the lowestWL at the end of resting when it was referred to the weight of thehams after storage (just before salting). However, this differencewas not observed when it was referred to the fresh weight. This resultcould be important for those ham producers who make the decisionto extend the resting period of the dry-cured ham elaboration processuntil a target weight loss is achieved.

3.3. Experiment 3. Effect of salting temperature on ham salt uptake

The hams salted at 4 °C absorbed significantly more salt comparedto those salted at lower temperatures, taking into account the NaClcontent on a dry matter basis (Table 8). These differences were statis-tically significant (P b 0.05). Several studies have reported that saltdiffusion in meat increases with increasing temperatures (Djevel &Gros, 1988; Fox, 1980; González-Méndez et al., 1983). Although theabove studies were carried out using temperatures over 3 °C, the pos-itive effect of the temperature on salt diffusion described could ex-plain the differences observed in salt uptake between the hamssalted at 4 °C compared to the hams salted at lower temperatures.However, we did not find significant differences in the global NaCl

B. 6 days of storage

d

c

1

1

2

23

3

storage before salting (panel A, a–b) and one ham after 6 days of storage before saltinged in the Biceps femoris muscle are indicated: (1) inner zone, (2) zone adjacent to theto the SF and close to the Semitendinosus (ST) muscle.

Table 7Salt content (%) in three zones of Biceps femoris of the hams from Experiment 2 deter-mined by computed tomography at different stages of the elaboration process.

Storage time before salting

0 days 3 days 6 days

(n = 6) (n = 6) (n = 6)

Inner zone of BFAfter salting 1.10a ± 0.12 1.11a ± 0.36 0.86b ± 0.11Mid resting 1.56ab ± 0.29 1.86a ± 0.57 1.22b ± 0.25End of resting 2.52ab ± 0.65 2.79a ± 0.65 1.91b ± 0.28

Zone close to VMAfter salting 0.86 ± 0.32 1.21 ± 0.61 0.74 ± 0.50Mid resting 1.21 ± 0.38 1.44 ± 0.40 0.92 ± 0.24End of resting 1.93 ± 0.43 1.53 ± 0.31 1.46 ± 0.34

Zone close to STAfter salting 0.49 ± 0.12 0.45 ± 0.21 0.35 ± 0.12Mid resting 0.76 ± 0.21 1.07 ± 0.47 0.49 ± 0.22End of resting 1.32a ± 0.41 1.41a ± 0.48 0.89b ± 0.34

SD, standard deviation; BF, Biceps femoris muscle, VM, Vastus medialis muscle; ST,Semitendinosus muscle.a,b,cLeast square means within a row without a common letter are significantlydifferent (P b 0.05). Tukey's test.

71N. Garcia-Gil et al. / Meat Science 96 (2014) 65–72

content on a dry matter basis between the hams salted at −1 °C andthose salted at 0.5 °C. Thus, the possible formation of NaCl · 2H2O didnot have any effect on salt diffusion. Similarly, Pérez-Álvarez et al.(1997) neither detected significant differences in salt content be-tween hams salted at 1.5 ± 1 °C nor hams salted at 3.5 ± 1 °C.

The NaCl contents in the inner zone of Biceps femoris muscleobtained using CT (Table 6) were in line with salt uptake results.The NaCl content in the inner part of the hams (Biceps femorismuscle)was significantly higher in the hams salted at 4 °C than in the hamssalted to 0.5 °C (P b 0.05). Therefore, in order to reduce the variabilityin salt uptake between batches, the control of salting temperature isvery important, especially when the temperature can range between0.5 °C and 4 °C. The salt content at the end of resting (day 65) wasabove 1% (minimum value at the end of resting proposed by PDOTeruel in all hams, Boletín Oficial del Estado, 1993). Further studiesare needed to elucidate whether these differences comply with thePDO Teruel requirements in terms of NaCl content when shorter saltingand resting times (e.g. 45 days) are used.

Although salt absorption was temperature dependent above 0.5 °C,the variability (SD) in salt uptake within batches was not significantlyreduced at any of the temperatures applied during salting in thisstudy according to Levene's test.

4. Conclusions

The duration of storage before salting as well as the temperatureduring salting tested in this study had relevant effects on salt absorp-tion although no particular condition reduced the variability in salt

Table 8NaCl content of the hams subjected to different temperatures during salting and theestimated NaCl content using CT analysis in the inner zone of Biceps femoris (BF) musclethroughout different stages of the elaboration process.

Temperature during salting

−1.0 °C 0.5 °C 4.0 °C

(n = 12) (n = 12) (n = 12)

NaCl (% DM) ± SD NaCl (%) ±SD in the inner zone of BF⁎

11.31b ± 0.94 11.25b ± 0.82 12.23a ± 1.10

Mid resting 1.70ab ± 0.10 1.55b ± 0.22 1.86a ± 0.32End of resting 2.55ab ± 0.14 2.29b ± 0.40 2.81a ± 0.52

DM, dry matter; SD, standard deviation.a,bLeast square means within a row without a common letter are significantly different(P b 0.05). Tukey's test.⁎ The number of hams used by treatment for CT analysis was 6.

uptake within batches. The most important effect of pre-salting stor-age appeared at 6 days of storage and the most important effect ofsalting temperature was observed at 4 °C. Therefore, pre-salting andsalting conditions should be controlled to reduce the variability insalt uptake between batches, especially when storage times longerthan 3 days and salting temperatures above 0.5 °C are used.

Acknowledgments

This research was supported by INIA (Contract No. PET-2007-08-C11-08 del Plan Específico de investigación de Teruel). We thankQuim Arbonés, Alex Morente and Bernardo Guerra for their technicalassistance. Emine Asik is especially acknowledged for her participationin the experimental part. Acknowledgements are extended to CarlosLiébana from “el Consejo Regulador de la Denominación de OrigenProtegida Jamón de Teruel” for his help in the selection of the rawhams and finally, to the company Jamones y Embutidos Alto Mijares,S.L for facilitating the task of ham selection.

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