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.     

Antihypertensive effect and antioxidant activity of peptide fractions extracted from Spanish dry-cured ham

This study examined the antihypertensive and antioxidant activities of water soluble fractions of a Spanish dry-cured ham extract. Antihypertensive activity of a fractionated peptide extract, by size-exclusion chromatography was determined by measuring changes in systolic blood pressure of spontaneously hypertensive rats after oral administration. Every sample exhibited antihypertensive activity, pooled fractions corresponding to 1700 Da or lower were the most antihypertensive with a decrease of 38.38 mm Hg in systolic blood pressure. In vitro experiments revealed marked in vitro angiotensin I-converting enzyme inhibitory activity in fractions corresponding to these elution volumes. Some of the fractions exhibited great 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity, ranging from 39% to 92% as well as superoxide ion extinguishing ability with values ranging from 41.67% to 50.27% of the antioxidant activity, suggesting the presence of peptides with antioxidant activity. These findings suggest that Spanish dry-cured ham contains peptides with antioxidant and antihypertensive activities.     

High pressure applied to frozen ham at different process stages. 2. Effect on the sensory attributes and on the colour characteristics 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 the appearance, some texture and flavour parameters and on the instrumental colour characteristics of dry-cured hams. Pressurized hams showed slightly lower visual colour intensity than the control ones. In general, pressurization did not have a significant effect on the flavour characteristics of the final product. The 600-MPa hams from the ERS process showed significantly lower crumbliness and higher fibrousness scores than the control and the 400-MPa hams. However, none of these differences were enough to affect the overall sensory quality of the hams negatively. Regarding instrumental colour characteristics (L(?)a(?)b(?)), an increase in lightness was observed in the biceps femoris muscle from GH hams pressurized at 400MPa and 600MPa but not in the ERS hams.     

High pressure treatment of dry-cured Iberian ham. Effect on radical formation,lipid oxidation and colour

The effect of high-pressure treatment (200, 400, 600 and 800 MPa) on radical formation in solid samples of dry-cured Iberian ham and in ham slurries was evaluated using the spin-trapping technique and electron spin resonance (ESR) spectroscopy. In addition, hexanal was, as a secondary lipid oxidation product, assessed by gas chromatography. The effect of pressure treatments on ESR signals determined in the spin-trapping assay following pressure treatment in solid samples of dry-cured Iberian ham was not statistically significant. However, the lowest level of pressure applied initiated radical formation and promoted lipid peroxidation, whereas intermediate to high levels of pressure seemed to promote further reaction and disappearance of free radicals. Pressure significantly affected hexanal content in the same way as seen for formation of free radicals. Regarding the slurries prepared from dry-cured ham, pressure significantly increased the tendency of radical formation as seen from the ESR signals and significantly increased the hexanal content. The different pattern between solid ham and ham slurries points toward an initiation mechanism associated with the membrane phospholipids for oxidation. In addition, surface colour (L*, a* and b* values and percent reflectance values) of non-pressurized and pressurized (200–800 MPa) dry-cured Iberian ham samples was assessed. Non-pressurized samples showed a higher lightness than pressurized samples, and redness significantly decreased with pressure treatment.     

High pressure treatments on the inactivation of Salmonella Enteritidis and the physicochemical, rheological and color characteristics of sliced vacuum-packaged dry-cured ham

The effect of high pressure (HP) on Salmonella Enteritidis in sliced dry-cured ham stored under temperature abuse (8°C) during 60d was investigated. After treatment, reductions of S. Enteritidis were 1.06, 2.54 and 4.32 log units in ham treated at 400, 500 and 600MPa for 5min at 12°C, compared to non-pressurized samples. After 60d, counts of S. Enteritidis in ham treated at 400 and 500MPa were 2.56 and 2.66 log units lower than in non-treated ham, whereas the pathogen was only detected after enrichment in ham treated at 600MPa. Lipid oxidation increased with storage and pressurization, whereas total free amino acid contents were similar in HP and control samples after 60d. Dry-cured ham treated at the highest pressures exhibited lower shear resistance, whereas the maximum force to compress the sample was slightly changed. Color (L*, a* and b*) varied with pressurization and storage. Changes induced by HP in dry-cured ham were attenuated during storage.     

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.     

Volatile compounds in dry-cured Serrano ham subjected to high pressure processing. Effect of the packaging material

The effect of high pressure treatment (400 MPa, 10 min at 12 °C) on the volatile profile of Spanish dry-cured Serrano ham, packaged with or without aluminum foil in a multilayer polymeric bag, was investigated. The analysis of the volatile fraction was carried out by dynamic headspace extraction coupled to gas chromatography–mass spectrometry. Pressure treatment only had a slight effect on the volatile fraction of Serrano ham. Most compounds affected by pressurization, such as alkanes (C₉–C₁₂), 2-undecene, 2-nonanone, 1-octen-3-one, 1-heptanol, 2-hexanol, 2-heptanol, ethyl pentanoate, benzaldehyde and styrene, presumably originated from the metabolism of moulds. A significant effect of pressurization on the migration of compounds from the plastic material was found. Linear and branched chain alkanes, alkenes as well as benzene compounds, were generally less abundant in pressurized samples than in untreated samples. A scalping effect was also observed for compounds such as butanal, pentanal, ethyl esters and pyrazines.     

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.     

Efficiency of mitochondrial DNA restriction analysis and RAPD-PCR to characterize yeasts growing on dry-cured Iberian ham at the different geographic areas of ripening

The efficiency of mitochondrial DNA (mtDNA) restriction analysis and random amplification of polymorphic DNA (RAPD)-PCR to characterize yeasts growing on dry-cured Iberian ham was evaluated. Besides, the distribution of the main species and biotypes of yeasts in the different ripening areas of this product was investigated. MtDNA restriction analysis allowed yeast characterization at species and strain level. RAPD-PCR with the primers (GACA)₄ and (GAC)₅ was inappropriate for characterization at species level. Most of the mtDNA restriction patterns detected in dry-cured Iberian ham were consistent with Debaryomyces hansenii. Several yeasts biotypes were associated to specific geographic areas of dry-cured Iberian ham ripening.     

Texture changes in dry-cured ham pieces by mild thermal treatments at the end of the drying process

The present study evaluated the effects of mild thermal treatments at the end of the drying process on physicochemical characteristics and instrumental and sensory texture in dry-cured ham. Experiment 1: effect of thermal treatments (4–46 °C) for 4 h and 24 h. Experiment 2: time effect (4–168 h) of thermal treatments at 30 °C and 36 °C. Both experiments were done on small dry-cured ham dices. Experiment 3: time effect (4–168 h) of thermal treatment at 30 °C on both instrumental and sensory texture of 4-cm-thick sections of dry-cured ham. The thermal treatment at 30 °C for 168 h on both dry-cured ham muscle dices (20 mm × 20 mm × 15 mm) and dry-cured ham sections (4 cm thick) decreased softness, adhesiveness and pastiness in BF muscle, without increasing hardness in SM muscle or affecting moisture, a_w and proteolysis index.     

Effect of exposure to light on physico-chemical quality attributes of sliced dry-cured Iberian ham under different packaging systems

Dry-cured Iberian ham slices were stored under vacuum and under two different atmospheres (N₂ = 70% N₂ + 30% CO₂; Ar = 70% Ar + 30% CO₂) and exposed to lightness or darkness. Physico-chemical, sensory and microbial analysis was carried out throughout 60 days storage. Vacuum samples showed the highest a*-value compared to N₂ and Ar after 30 (P < 0.05) and 60 days (P < 0.05). The influence of illumination during storage was evident after 60 days of storage, L* and a*-values being lower (P < 0.01) in hams exposed to light than those kept in darkness, which can be ascribed to the lower nitrosylmioglobin content in samples exposed to light after 60 days (P = 0.001). Ham slices stored in darkness showed the lowest TBARS values (P < 0.05) and hexanal content (P < 0.05) after 60 days. Slices of ham packed in vacuum showed lower TBARS values than N₂ and Ar batches (P = 0.001), these samples being perceived as more rancid (P < 0.05). The rest of the sensory attributes were not generally affected by gas mixture or illumination (P > 0.05).     

Influence of low-sodium mixtures of salts on the post-salting stage of dry-cured ham process

The reduction of added sodium chloride in dry-cured ham has been proposed to decrease the amount of sodium in the diet. The effect of substituting sodium chloride by potassium chloride, calcium chloride and magnesium chloride in some physicochemical characteristics of dry-cured ham throughout the post-salting stage was evaluated. The partial replacement of NaCl had significant effects on salt content at the end of the post-salting stage in the traditional process and this significantly affected a_w. The results showed that lower sodium hams, salted with a combination of NaCl and KCl, needed a maximum of 16 days more (32% increase) of post-salting than hams salted with 100% NaCl, while hams salted with a combination of NaCl, KCl, CaCl₂ and MgCl₂ needed a maximum of 26 days more (52% increase).     

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.     

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.     

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.     

Vitamin (B1, B2, B3 and B6) content and oxidative stability of Gastrocnemius muscle from dry-cured hams elaborated with different nitrifying salt contents and by two ageing times

The effect of the amount of added nitrate and nitrate plus nitrite to dry-cured hams on the vitamin (B1, B2, B3, B6) content, the antioxidant enzyme superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx) activities and the thiobarbituric acid reactive substances (TBARS) was assessed in Gastrocnemius muscle at the end of two ripening processes. Five different curing mixtures (Hi–N: 600 KNO₃; Lo–N: 150 KNO₃; Hi–Mix: 600 KNO₃ + 600 NaNO₂; Lo–Mix: 150 KNO₃ + 150 NaNO₂; Hi–Mix/Asc: 600 KNO₃ + 600 NaNO₂ + 500 sodium ascorbate, expressed as mg of salts added on surface per kg of fresh ham) were evaluated in dry-cured hams aged for 11.5 months (standard process, SP) and 22 months (long process, LP).     

Lipid and protein oxidation and sensory properties of vacuum-packaged dry-cured ham subjected to high hydrostatic pressure

The effect of HHP treatment (600 MPa) on the oxidative stability of lipids and proteins of vacuum-packaged Iberian dry-cured ham and the impact on the sensory characteristics of the product was investigated. In order to assess how different commercial presentations are affected by HHP treatment, three different presentations of vacuum-packaged Iberian dry-cured ham were considered, namely, (i) intact format (IF) corresponding to non-sliced vacuum-packaged dry-cured ham, (ii) conventional-sliced format (CSF) corresponding to dry-cured ham slices placed stretched out in the package and (iii) alternative-sliced format (ASF) corresponding to dry-cured ham slices piled up horizontally. The oxidation of dry-cured ham lipids and proteins was enhanced by HHP-treatment with the presentation being highly influential on these oxidative reactions. Pre-slicing dry-cured ham results in a more susceptible product to oxidative reactions during pressurisation and subsequent refrigerated storage. Possible mechanisms, by which HHP-induced oxidative reactions would affect particular sensory traits in vacuum-packaged Iberian dry-cured ham such as colour, texture and flavour attributes, are discussed.     

Carcass and ham quality characteristics of heavy pigs from different genetic groups intended for the production of dry-cured hams

Carcass and ham quality characteristics of pig populations divided by harvest weights — HW (130 and 160 kg) were evaluated to determine the effects of gender (barrows and gilts) and distinct genetic groups — purebred (DUDU) and crossbred Duroc (DULA, DUWI and DULL) as well as purebred Large White (WIWI) on the suitability for use in dry-cured ham production. At 130 kg, DUDU pigs yielded the highest fat thickness of the ham (P < 0.01) and an intramuscular fat content (IMF) of 3.15% in Semimembranosus muscle (SM). DUDU pigs also had a SM pH_u of 5.7. This genetic group met the specifications for dry-cured ham production. No differences could be found in meat quality characteristics between genetic groups harvested at 160 kg. However at this HW, gilts produced significantly (P < 0.05) heavier and leaner hams compared to barrows.     

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.