Relationship between water content, NaCl content, pH and texture parameters in dry-cured muscles

The aim of the present study was to describe the effect of NaCl and pH on the relationship between water content and hardness, cohesiveness and springiness in dry-cured muscles. The experiment was undertaken using 18 hams, selected in a commercial slaughterhouse. Half of the hams had a pH < 5.7 and the rest a pH > 6.2, measured on the semimembranosus muscle at 24-h postmortem. The semimembranosus and biceps femoris muscles were cut from hams, cured and individually packaged in bags and were laid in trays in a room at 2 ± 2 °C for 45 days. Thereafter nine samples from each muscle were shaped like a parallelepiped and dried until different levels of drying, ranging from 28.5% to 59.7% water content, were attained. The rest of the muscle was ground and packaged until its subsequent physicochemical analysis. At the end of the drying period, a Texture Profile Analysis was used to determine textural parameters. The results indicated that for a range of X (kg H₂O/kg dry matter) between 0.8 and 1.3 the hardness remains practically unchanged while for X < 0.6 the hardness increases substantially. The samples from hams with low pH_SM had greater hardness, cohesiveness and springiness than those from hams with high pH_SM. Dry-cured muscles with lower NaCl content showed lower hardness, cohesiveness and springiness, especially in those with pH_SM > 6.2. At X values lower than 0.6 the hardness was more influenced by water content than by NaCl content or pH_SM.     

Proteomic analysis of semimembranosus and biceps femoris muscles from Bayonne dry-cured ham

The aim of the study was to delineate and compare the proteomic maps of two muscles of dry-cured ham: the biceps femoris and the semimembranosus. For this purpose, we used two-dimensional electrophoresis on a subcellular muscle fraction: insoluble protein in low ionic strength buffer. After protein identification by MALDI-TOF mass spectrometry and bioinformatic analyses, we found differences in expression levels in the two muscles. Seventy-three proteins or fragments were differentially expressed: 43 were over-represented in semimembranosus and 30 in biceps femoris. Although the study was performed on the insoluble protein fraction in low strength ionic buffer, protein and fragment identifications by mass spectrometry showed that most of the proteins were involved in energy metabolism. The differences observed between the two muscles can be explained by the differences in salt and moisture content in the course of dry-cured ham processing.     

Development of a rapid, specific and efficient procedure for the determination of proteolytic activity in dry-cured ham: definition of a new proteolysis index

A method was adapted to determine proteolytic activity in dry-cured ham using fluorescamine-specific labelling of N-terminal α-amino groups of peptides and amino acids. Fluorescence of the complex was measured using a microplate procedure and optimum excitation and emission wavelengths of 375nm and 475nm, respectively. A new proteolysis index (PI) was defined as the percentage ratio of the N-terminal α-amino group content to the total protein content of the ham extract. The robustness of the method was evaluated by measuring PI in pork meat samples subjected to standardized processing conditions and in samples extracted from industrial hams taken at different stages of processing. For the industrial samples, a comparison with the classic nitrogen procedure of PI determination was performed and a formula relating the two PIs was established. The rapidity, sensitivity and specificity of the procedure make it a good candidate for a screening test to evaluate ham quality in industry.     

Biochemical and sensory changes in dry-cured ham salted with partial replacements of NaCl by other chloride salts

The reduction of the content of sodium chloride in dry-cured ham was studied in to prevent the problems related to high sodium intake (i.e. the hypertension). One of the possibilities to reduce the sodium content is the partial replacement of sodium chloride by mixtures of potassium, magnesium and calcium chloride salts. The effect of two salting formulations (formulation II: 50% NaCl-50% KCl and formulation III: 55% NaCl, 25% KCl, 15 CaCl₂ and 5 MgCl₂) on the protease activity through the dry-curing process and on the sensory characteristics of the final product was evaluated and compared to those of control hams (formulation I, 100% NaCl). Sensory attributes were all affected in the hams containing CaCl₂ and MgCl₂ while hams containing 50% KCl and NaCl (formulation II) were better valued, except for the attribute taste probably due to the potassium contribution to bitter taste.     

Reduction of NaCl content in restructured dry-cured hams: Post-resting temperature and drying level effects on physicochemical and sensory parameters

The effects of post-resting temperature (5 °C, 15 °C and 25 °C) and drying level (low and high, corresponding to final water contents (w/w) of 57% and 50%, respectively) were evaluated in restructured dry-cured hams. The reduction of NaCl content, with and without the addition of K-lactate as NaCl substitute was also evaluated. Physicochemical and instrumental colour and texture (Stress Relaxation test) parameters and sensory attributes were measured. The main effects of reducing the NaCl addition from 30 g/kg to 15 g/kg in restructured dry-cured hams were the reduction of saltiness and the increase of a_w, proteolysis and softness. The addition of K-lactate (19.7 g/kg) contributed to reduce these effects. Hams from high drying level had a longer processing time and a higher proteolysis index, but lower water content and harder texture. The increase of post-resting temperature to above 5 °C reduced the processing time and the metallic flavour, but at 25 °C restructured hams were spoiled. Therefore, the problems due to the reduction of NaCl to 15 g/kg in restructured dry-cured hams can be reduced by adding K-lactate and drying at 15 °C (after 3.5 months of resting at 5 °C) until a final weight loss of around 45% is reached.     

Prediction of salt and water content in dry-cured hams by computed tomography

Application of computed tomography (CT) in meat science is based on the different X-ray attenuations that tissues of different density produce. Processed data generate images (tomograms) where different biological structures may be distinguished. CT is of special interest for the study of the meat curing processes since a high density of salt ions produce a marked increase of CT attenuation values. Therefore, salt diffusion and distribution can be easily followed throughout the process. In this study, prediction models for salt and water content in dry-cured ham have been developed, obtaining errors of prediction of 0.3% NaCl and 1.5% water. Fat content and drying level significantly affect the precision of salt and water content predictions. A certain underestimation of salt content in fatty samples was observed. CT and the developed predictive models may be useful in the meat industry as a tool for characterizing and optimizing salting processes.     

Effect of brine thawing/salting for time reduction in Spanish dry-cured ham manufacturing on proteolysis and lipolysis during salting and post-salting periods

The simultaneous brine thawing/salting operation has been proposed as an effective alternative for the accelerated processing of frozen cured hams. The aim of the present study was to study the effect of this new technology on the lipolytic and proteolytic enzymes responsible for the generation of flavour precursors during the salting and post-salting stages of the manufacturing of Spanish dry-cured ham. The effect of the frozen and thawed process produced a higher proteolytic and lipolytic activity than in the fresh traditional salted hams (FPS) that was detected by a higher concentration in free amino acids and free fatty acids. On the other hand, the brine thawed/salted treatments, at atmospheric pressure (BTS) and with vacuum impregnation (BTS-TP), produced an acceleration of the myofibrillar degradation that occurred in the BTS and BTS-TP hams in comparison to FPS. However, the lipolysis was affected by the frozen treatment but not by the brine thawed treatments, as few differences in free fatty acids and lipase activity were detected among the frozen and brine thawed hams at the end of post-salting stage.     

Accelerated processing of dry-cured ham. Part 2. Influence of brine thawing/salting operation on proteolysis and sensory acceptability

In a previous study, the brine thawing/salting operation using frozen hams as raw material was studied as a valid alternative for the accelerated processing of dry-cured hams. But no information was available on how this treatment could affect some important biochemical mechanisms and the sensory quality of hams. The aim of this work was to study the influence of the simultaneous brine thawing/salting operation on proteolysis and sensory acceptability of the produced dry-cured hams. The results confirm that dry-cured hams can be produced by using brine thawing/salting with a substantial reduction in the thawing and salting time needed. This accelerated process resulted in similar or even better sensory preferences than hams produced through the traditional method. However, the preference of consumers based on the appearance was lower for most of the hams than when using the traditional method, probably due to a wider slice section of the brined hams that can be corrected by adequate pressure during the salting. Thus, this treatment can be used without affecting the quality of dry-cured hams.     

Effect of low-temperature preservation on the quality of vacuum-packaged dry-cured ham: Refrigerated boneless ham and frozen ham cuts

The effect of storage on dry-cured ham quality was studied. Sixteen vacuum-packaged boneless dry-cured hams and sixteen vacuum-packaged dry-cured ham cuts were stored in darkness under refrigeration (4±2°C; 8 months) or freezing (-18±1°C; 24 months), respectively. Instrumental colour and texture, physico-chemical and biochemical parameters, sensory profile and consumer acceptability and purchase satisfaction were measured throughout storage. The overall quality of refrigerated boneless dry-cured hams and frozen dry-cured ham cuts showed only limited changes throughout long-term storage. Significant changes involved loss of odour and flavour, increased adhesiveness and modification of hardness, the Semimembranosus muscle became tender while Biceps femoris became harder, leading to a higher textural homogeneity. In agreement with those changes, the overall acceptability assessed by a trained panel decreased throughout storage, though this was significant regarding only frozen hams. However, consumer evaluation of acceptability, as well as satisfaction with hypothetical purchasing, did not vary significantly throughout storage.     

The effect of green ham pH and NaCl concentration on cathepsin activities and the sensory characteristics of dry-cured hams

There is a tendency to reduce the amount of NaCl in the manufacturing process of Spanish dry-cured ham. NaCl, pH and temperature determine the stability of this product. This study was concerned with the evaluation of green ham pH and sodium chloride concentration on cathepsin activities, physico-chemical parameters and sensory characteristics of dry-cured hams. Two different amounts of salt (55 and 80 g kg⁻¹) and two different pH levels (pH at 24 h post mortem <5·8; pH at 24 h post mortem >6·2) were used. Physico-chemical composition, cathepsin activity and a number of sensory parameters were evaluated. Hams with high pH displayed lower cathepsin activity, NPN, saltiness and hardness whereas the levels of brightness, crumbliness, pastiness and adhesivity were found to be higher than in normal hams. A high level of salt produced greater cathepsin B and B+L activity and lower pastiness and adhesivity than the samples with a low NaCl level. © 1998 SCI.     

High pressure applied to frozen ham at different process stages. 1. Effect on the final physicochemical parameters and on the antioxidant and proteolytic enzyme activities of dry-cured ham

This paper describes the effect of high pressure (400MPa and 600MPa) applied to frozen hams at early stages of the dry-cured ham process: green hams (GH) and hams at the end of the resting stage (ERS), on some physicochemical parameters and on antioxidant and proteolytic enzyme activities in the final product. No significant differences were observed among treatments either in the drying kinetics or in the physicochemical characteristics. However, when high-pressure was applied to frozen GH hams it produced a superficial denaturation that affected salt absorption and, consequently, the proteolysis index. The high-pressure treatment applied during the processing of previously frozen GH and ERS hams reduced the antioxidant enzyme activities slightly (superoxide dismutase, catalase and glutathione peroxidase) but did not affect the cathepsin B and the cathepsin B+L activities.     

Accuracy of near infrared spectroscopy for prediction of chemical composition, salt content and free amino acids in dry-cured ham

The capability of near infrared (NIR) spectroscopy was examined for the purposes of quality control of the traditional Slovenian dry-cured ham “Kraški pršut.” Predictive models were developed for moisture, salt, protein, non-protein nitrogen, intramuscular fat and free amino acids in biceps femoris muscle (n = 135). The models' quality was assessed using statistical parameters: coefficient of determination (R²) and standard error (se) of cross-validation (CV) and external validation (EV). Residual predictive deviation (RPD) was also assessed. Best results were obtained for salt content and salt percentage in moisture/dry matter (R_CV² > 0.90, RPD > 3.0), it was satisfactory for moisture, non-protein nitrogen, intramuscular fat and total free amino acids (R_CV² = 0.75–0.90, RPD = 2.0–3.0), while not so for protein content and proteolysis index (R_CV² = 0.65–0.75, RPD < 2.0). Calibrations for individual free amino acids yielded R_CV² from 0.40 to 0.90 and RPD from 1.3 to 2.9. Additional external validation of models on independent samples yielded comparable results. Based on the results, NIR spectroscopy can replace chemical methods in quality control of dry-cured ham.     

Processing of dry-cured ham in a reduced-oxygen atmosphere: Effects on physicochemical and microbiological parameters and mite growth

The effects of a reduced-oxygen atmosphere (ROA) ([O₂] < 4.5%) during part or the whole of dry-cured ham processing on microbiological and physico-chemical parameters and mite growth were investigated in two independent experiments. In Experiment 1, six hams were processed in ROA and six in air for 275 days; in Experiment 2, where lower RH was used, six hams were processed in ROA for 289 days, six for 214 days in air + 75 days in ROA, and six in air for 289 days. Microbiological analyses during the process and physicochemical analyses in final products were carried out. The use of ROA during the whole process increased the L∗ colour parameter in the subcutaneous fat and proteolysis index and decreased b∗ in the external part of the subcutaneous fat and cholesterol oxide concentration. The use of ROA combined with low RH retarded microbial growth and prevented mite growth.     

Effect of the relative humidity of drying air during the resting period on the composition and appearance of dry-cured ham surface

This study evaluates the effect of three different relative humidities (RH) during the resting period on the composition of the external part of Semimembranosus muscle (2 mm thick) and the appearance of the surface of the dry-cured ham after resting and ageing. Forty-eight hams stored after salting for 40 days at 4±1 °C and three different RH (52±3, 78±3 and 85±3%) were studied. Half of the hams in each treatment were sampled after the resting period and the rest were aged for 8 additional months at the same temperature and RH. Storage of hams at 52% RH during resting produced a white appearance in some parts of the rind and increased the surface covered with oil drip. Hams stored at 78% showed a similar composition to those stored at 52%, except for the higher moisture content and lower Na/moisture ratio at the end of the resting period, and potassium content (on dry matter, dm) at the end of the process. At the end of resting no white rind was observed, and at the end of the process the surface covered with oil drip was slightly lower than at 52%. Storage of hams at 85% RH increased the surface pH, Na2HPO4.12H2O crystallisation, Mg (dm), Mg/moisture, K (dm) and NPN/NT at the end of the resting period, and increased the pH and Mg (dm), Mg/moisture, Na/moisture, K/moisture, the ash (dm) and ash/moisture contents and decreased the a_w and the surface covered with oil drip at the end of the process.     

Influence of partial replacement of NaCl with KCl, CaCl2 and MgCl2 on lipolysis and lipid oxidation in dry-cured ham

Sodium intake above nutritional recommendations may involve harmful consequences to health such as the increased risk of cardiovascular diseases. Dry-cured ham constitutes a product with a relatively large amount of sodium. Thus, to obtain a healthier product for consumers with reduced sodium content, two formulations containing KCl alone (formulation II) or mixed with CaCl2 and MgCl2 (formulation III) have been proposed to partially replace NaCl. Lipolysis and lipid oxidation occurring in hams processed with these formulations have been studied since they have direct influence on the final flavor. No significant differences in acid lipase activity or lipid oxidation were found at the end of the process between the alternative formulations and formulation I (control with 100% NaCl). Differences in some free fatty acids, generated along the processing, were detected among treatments and at the end of dry-curing. Data suggests a slight trend towards a major lipolysis during treatment III.     

Effect of the inoculation of a starter culture and vacuum packaging (during resting stage) on the appearance and some microbiological and physicochemical parameters of dry-cured ham

The effect of the inoculation of a starter culture and vacuum packaging (during the resting stage) on dry-cured ham appearance, microbiological and physicochemical parameters was studied. Half of the 36 processed hams were inoculated, after salting, with a commercial starter culture containing lactic-acid bacteria, Gram-positive catalase-positive cocci and yeasts. 18 hams per group (inoculated and non-inoculated) remained vacuum packaged during resting. Microbiological analyses were carried out on the lean surface during processing, on subcutaneous fat tissue at the drying stage and on lean tissue in the finished product. Appearance was evaluated during processing. Physicochemical analyses (NaCl, H(2)O, proteolysis index, a(w)) were done on Semimembranosus and Biceps femoris in the final product. Inoculation caused a reduction of mould growth and oil drip. Vacuum packaging induced increased proteolysis and increases in all microbial counts and a reduction of oil drip, mould growth and weight loss during processing.     

High-pressure treatment of dry-cured Iberian ham. Effect on colour and oxidative stability during chill storage packed in modified atmosphere

Slices of dry-cured Iberian ham were pressurized at 200 and 400 MPa for 15 min and subsequently packed in two different modified atmospheres of 30% carbon dioxide or 30% carbon dioxide and 5% oxygen (both balanced with nitrogen). Non-pressurized ham slices were also packed in two different modified atmospheres and all packages were stored at 5 °C for 39 days in illuminated chill cabinets. Measurements of colour and oxidative stability were performed after 1, 18 and 39 days of storage. High-pressure treatments at the level of 400 MPa resulted in the highest value for the tristimulus lightness L ^*-parameter during storage, reaching the maximum values after 39 days. Redness, measured as the tristimulus a ^*-parameter, was affected by pressure treatment, since samples submitted to treatment of highest pressure had significantly lower initial red colour. Oxygen was found to have a detrimental effect on nitrosylmyoglobin content since the extractable content was significantly lower after 18 and 39 days of storage in the 5% oxygen atmosphere. The effect of high pressure on oxidative stability was statistically significant after 39 days of chill storage with slices pressurized at 400 MPa showing the highest content in TBARS. High-pressure treatment at 400 MPa resulted in discoloration and oxidative degradation of lipids in dry-cured Iberian ham during subsequent illuminated chill storage.     

Effect of IGF-II (insulin-like growth factor-II) genotype on the quality of dry-cured hams and shoulders

The aim of this study was to investigate the effect of the paternal allele (homozygous AA and heterozygous AG) of the IGF-II gene on the fat content, fatty acid composition and sensory characteristics of dry-cured hams and shoulders. The effects were more evident in the subcutaneous fat thickness than in the intramuscular fat (IMF) content, and in the dry-cured hams rather than the dry-cured shoulders. Subcutaneous fat thickness was significantly higher in AG dry-cured hams and shoulders; however, IMF content was only significantly higher in AG dry-cured hams. These effects produce changes in fatty acid composition and sensory characteristics when comparing both batches of each product, but the behavior differed with the type of product. Sensory characteristics were similar in both batches of dry-cured hams in spite of the differences in IMF content. Nevertheless, AG dry-cured shoulders showed higher scores in most of the attributes evaluated, despite the IMF content being similar between batches.