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.     

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.     

Volatile compounds of dry-cured Iberian ham as affected by the length of the curing process

Volatile compounds from 10 dry-cured Iberian hams ripened for two different processing times, a prolonged traditional one (600 days) and a shortened process (420 days), were analysed by purge and trap coupled to gas chromatography-mass spectroscopy. Eighty-three compounds were identified which agreed with the major classes found in other ham types. The amount of methyl branched alkanes was much higher than in other dry-cured ham types, probably due to the feeding regime. The percentages of 2- and 3-methylbutanal were higher (p<0.0001 and p<0.0003, respectively) in the longer aged hams, whereas the amounts of some compounds from lipid oxidation decreased from 420 to 600 days aging. In agreement with these observations, 600-day hams had higher scores for those odour and flavour traits usually considered to be positive attributes and lower scores for rancidity. A positive and significant correlation between 2-methyl butanal and cured flavour was found.     

Factors affecting dry-cured ham consumer acceptability

The objectives of the present study were (1) to compare the relative importance of price, processing time, texture and intramuscular fat in purchase intention of dry-cured ham through conjoint analysis, (2) to evaluate the effect of dry-cured ham appearance on consumer expectations, and (3) to describe the consumer sensory preferences of dry-cured ham using external preference mapping. Texture and processing time influenced the consumer preferences in conjoint analysis. Red colour intensity, colour uniformity, external fat and white film presence/absence influenced consumer expectations. The consumer disliked hams with bitter and metallic flavour and with excessive saltiness and piquantness. Differences between expected and experienced acceptability were found, which indicates that the visual preference of consumers does not allow them to select a dry-cured ham that satisfies their sensory preferences of flavour and texture.     

Sex and crossbreed effects on the characteristics of dry-cured ham

The right ham of 76 gilts and 82 barrows from five different crossbreeds, which included Duroc (DU), Landrace (LR), Large White (LW) and Belgian Landrace (BL) lines - DUx(LRxLW), LWx(DUxLW), LWx(LRxLW), BLx(DUxLW) and BLx(LRxLW) - were processed to produce dry cured hams. The external appearance of the hams, and the colour and thickness of the subcutaneous fat were determined. Chemical analyses, appearance, texture, flavour and odour were evaluated on biceps femoris (BF) muscle. The hams from the barrows showed a thicker and whiter layer of subcutaneous fat, higher marbling and lower processing loss than those from gilts. Hams from DU-sired pigs presented the highest marbling, but the worst texture characteristics. The texture characteristics of the hams from the LBx(LRxLW) cross were similar to those of the hams from DU-sired pigs. The hams from the LW-sired crosses showed the highest intensity of holes surrounding the coxo-femoral joint. The LBx(DUxLW) could be the most suitable among the five crosses studied for dry-cured ham production under the processing conditions used in this study.     

Effect of irradiation on colour and lipid oxidation of dry-cured hams from free-range reared and intensively reared pigs

The effect of irradiation dose (0, 5 and 10 kGy) of vacuum-packaged Iberian dry-cured ham slices from pigs fed on concentrate (CON) or free-range reared (FRG) was studied in relation to TBA-RS, hexanal content and instrumental colour changes. TBA-RS values increased after irradiation in the two sets of hams and the increase was dose-dependent. FRG samples showed higher TBA-RS values than CON samples in all treatments, although differences in the rate of formation of thiobarbituric acid-reactive substances were different in the two types of hams, being higher in CON samples than in FRG ones. Irradiation of dry-cured ham slices significantly increased hexanal contents in both sets of hams. Irradiation produced statistically significant increases in vacuum-packed dry-cured ham slices lightness (L^⁎-value), yellowness (b^⁎-value) and chroma (C^⁎-value). Irradiation resulted in significantly lower hue angle (h°) values and higher a^⁎-values in both sets of hams indicating a redder colour of irradiated samples than non-irradiated, and these changes were greater in FRG samples than in CON samples. Differences in composition characteristics of raw material could play an important role in the irradiation-induced changes on colour and lipid oxidation of vacuum-packaged dry-cured ham slices.Industrial relevanceIberian ham is dry-cured meat product with a high sensory quality due to pig fattening feature and the characteristics of its processing. Both factors lead to a product with characteristic cured red colour of the lean, an intense, characteristic and pleasant flavour, unique in dry-cured hams, derived from intense lipid oxidative phenomena. New commercialization formats of dry-cured Iberian hams include vacuum-packed sliced ham. Although the low Aw, NaCl and nitrite/nitrate contents make dry-cured ham not adequate for the growth of pathogens and spoilage microorganisms (cocci gram+ and yeast), those may be present on the surface of whole hams and reach the sliced product during the final boning, slicing and packaging operations even with the observation of strict hygienic procedures despite the implementation of modern technologies and HACCP systems, constituting a permanent risk of contamination. Dry-cured Iberian ham, as a result of its chemical characteristics, is a product with a long shelf-life at refrigeration temperature, however the risk of spoilage or pathogen growth could increase in the case of temperature abuse for a long stored period. Finally, due to health concerns, salting and curing process of dry-cured Iberian hams tend to a reduction in levels of NaCl and nitrite used. That could increase the risk associated to microorganism presence in dry-cured sliced hams. The use of irradiation could minimizes this risk, however irradiation could have important effects on overall quality of dry-cured Iberian products in which colour and extent of lipid oxidation and lipid oxidation-derived volatile compounds play an important role in consumer acceptation of the product.     

Contribution of a selected fungal population to proteolysis on dry-cured ham

The proteolytic changes taking place in dry-cured hams lead to increases in free amino acids. Such free amino acids not only contribute to flavour, but also serve as precursors of volatile compounds. Several months of ripening time are required to allow the particular flavour to develop. The fungal population allowed to grow on the surface of some types of dry-cured could play a key role on proteolysis, as it has been shown for dry-cured sausages. The purpose of this work was to study the possible contribution of fungi to proteolysis in dry-cured ham. For this, a strain each of non-toxigenic Penicillium chrysogenum (Pg222) and Debaryomyces hansenii (Dh345), selected for their proteolytic activity on myofibrillar proteins, were inoculated as starter cultures. Changes in the high ionic strength-soluble proteins of an external muscle (adductor) revealed in only 6 months higher proteolysis in the inoculated hams when compared to non-inoculated control hams. Proteolytic strains among the wild fungal population on non-inoculated control hams prevented from obtaining similar differences at the end of processing. However, inoculation with Pg222 and Dh345 led to higher levels for most free amino acids at the external muscle in fully dry-cured hams. In addition, the concentration for some of the more polar free amino acids (i.e. Asp, Glu, Ser and Gln) in inoculated hams was higher at external than at internal (biceps femoris) muscles. These promising results deserve further studies to know the impact of a selected fungal population on the volatile compounds and sensory properties of dry-cured ham.     

Influence of dietary fat, on fatty acid composition and sensory properties of dry-cured Parma ham

A feeding trial with 27 pigs was performed in order to estimate the effect of different dietary fats on the fatty acid composition, flavour and sensory properties of dry-cured Parma hams, ripened for 16 months. The animals received a pelleted diet supplemented with different fat sources: tallow (TA), corn oil (CO), and rapeseed oil (RO). The sensory quality of the hams was evaluated by means of sensory analyses and by instrumental procedures such as gas chromatography-mass spectrometry of the volatile aroma compounds. A treatment effect was detected for linolenic acid in RO vs. CO and TA hams (P<0.01) and for MUFA content (P<0.01) that was higher in RO and TA compared with CO. The results of panel test showed a significant difference (P<0.05) between TA vs. CO and RO hams. Volatile compounds showed limited differences even if in CO group the amount of singular compound is higher than TA and RO.     

Effects of high pressure application (400 and 900 MPa) and refrigerated storage time on the oxidative stability of sliced skin vacuum packed dry-cured ham

The effect of high pressure processing at 400 MPa and 900 MPa on the oxidative stability of sliced and vacuum packaged commercial dry-cured ham was determined by analyzing the antioxidant enzyme activities, TBARS levels (thiobarbituric acid reactive substances), vitamin E content and physicochemical characteristics during refrigerated storage for 50 days in different light conditions. In dry-cured ham pressurized at 400 MPa color changes and sensory analyses were also assessed. The high pressure process at 900 MPa produced a decrease in superoxide dismutase (SOD) and glutathione peroxidase (GSHPx) activities and increased vitamin E content. In contrast, pressurization at 400 MPa, increased SOD activity, and showed no effect on vitamin E content and GSHPx activity. In general the physicochemical parameters determined (fat, moisture and collagen) were unaffected by pressurization. Treatment at 400 MPa increased the instrumental color measurement of lightness (L* values, CIELAB). This level of pressure also modified the hardness, chewiness, saltiness and color intensity. These changes of the sensory attributes in dry-cured ham were significant, but small.     

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.     

Effects of potassium lactate and high pressure on transglutaminase restructured dry-cured hams with reduced salt content

Ten raw hams (from 5 carcasses) were boned and salted either with salt reduction (15 g/kg NaCl) or salt reduction with addition of potassium lactate (15 g/kg NaCl and 39.74 g/kg of a 60% K-lactate solution). Subsequently, the ham pieces were assembled together with transglutaminase, vacuum packed into water-permeable plastic bags and kept at 3 °C and 85% RH until reaching above 30% weight losses. The effects of K-lactate addition and the high-pressure (HP) treatment at 600 MPa on the physicochemical, instrumental colour and texture (Tensile test) and sensory characteristics of the biceps femoris (BF) muscle were evaluated. The addition of K-lactate did not have a negative effect on colour, flavour or texture of restructured dry-cured hams. The HP treatment increased significantly the pH, L^∗, a^∗ and b^∗ values and the breaking stress, and decreased the water-holding capacity and elasticity (apparent Young’s modulus) of BF muscle. The HP treatment also affected significantly the flavour (increasing saltiness, umami and sweetness) and the sensory texture attributes (increasing muscle binding, hardness, gumminess and fibrousness and decreasing adhesiveness and pastiness), as well as slice appearance (increasing brightness and iridescence and decreasing colour homogeneity).     

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.     

金华火腿特征风味物质研究进展

金华火腿是我国传统的干腌火腿,以其特殊的风味而著称。通过对金华火腿及其它干腌火腿主要风味物质、形成机理、提取及鉴定方法等研究现状的综述,表明对金华火腿特征风味物质的深入研究有利于了解风味物质形成规律,为金华火腿加工工艺控制及火腿调味料开发应用提供理论基础。     

Relationship between pH before salting and dry-cured ham quality

The effect of pH before salting on pork quality was studied in two sets of experiments: 904 hams, set A; and 104 hams, set B; the latter was used to verify the results from A. After pH measurements, the hams were subjected to the traditional process for producing Spanish dry-cured ham and then evaluated by an expert panel to correlate the sensory characteristics to the pH measurement before salting. The parameters evaluated were pastiness, softness, anomalous cut colour, crusting and white spots. Moisture, non-protein nitrogen, salt, protein, nitrate and nitrite were determined in samples from both experiments. The results obtained in experiment A showed that pastiness is closely related to the pH before salting (p<0.001), but not softness. From the receiver operating characteristics curve, a cut-off point of pH of 5.55 was selected to classify the raw material in two groups: normal-pH and low-pH hams. The pH before salting can also be correlated with the appearance of anomalous cut colour and crusting in hams. White spots were absent in both pH groups. Regarding compositional parameters, there were significant differences in moisture (p<0.001), salt (p<0.001), protein (p<0.001), non-protein nitrogen (p<0.001) and nitrate (p<0.05) contents between low-pH and normal-pH hams. The results from experiment B, confirmed the relationship between pH before salting and the appearance of defective texture and colour in the final product. Also results from experiment B confirmed the compositional parameters found in experiment A. Thus, the pH before salting is a good predictor for meat quality allowing the classification of the raw material in the first stage of manufacture. After classification, some modifications to the processing can improve the final characteristics of dry-cured hams.     

The effects of castration on the eating quality of dry-cured ham

The influence of the castration of entire male pigs on the eating quality of dry-cured ham was evaluated. Forty-eight dry-cured hams (435-day aged) were studied from entire and castrated males of two different crossbreeds. The proximate composition of the meat and the androstenone, indole and skatole fat content were determined. The entire hams were classified according to the androstenone and skatole content. Sensory analysis was carried out by a trained panel, evaluating marbling, juiciness, saltiness, graininess, toughness, overall flavour, boar odour and boar flavour. Also carried out was a preference and acceptability paired test by consumers. Castration increased meat fattening and reduced the androstenone and skatole levels of the fat. Significant differences (P<0.05) were found between entires and castrates for the average values given in all the sensory attributes studied. The dry-cured ham from castrates was scored as more flavoured, more marbled and softer. It was also perceived as less grainy, less salty and having less boar odour and flavour. The sensory perception of boar odour was more intense than that of flavour in dry-cured ham and appears to be related to the level of androstenone and skatole in fat. Dry-cured ham from castrated males was also more accepted and more preferred by consumers, especially women and habitual consumers. Castration of male pigs contributes to improve the quality of dry-cured ham. The rejection caused by boar odour and flavour is reduced, improving the overall flavour, texture and juiciness. In addition, the saltiness is less pronounced in ham from castrates. For this reason, the production of high quality dry-cured ham will have to shoulder the extra costs associated with processing castrated pigs.     

Postmortem meat quality and sex affect textural properties and protein breakdown of dry-cured ham

Texture measurements by instrumental texture profile analysis (TPA) and protein degradation analysis by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) were performed on 30 dry-cured hams resulting from four different post-mortem meat qualities categories (PSE, RSE, RFN and DFD). The main differences were observed in dry-cured hams from PSE and RFN meat qualities. Penetration force (80%), hardness, springiness, cohesiveness and chewiness, were significantly lower (P<0.05) in PSE than in RFN quality classes. The rate of the ripening process was affected as a higher proteolysis and absence of fragments at 150 and 85 KDa in PSE in relation to RFN classes, and with an intermediate proteolysis of RSE and DFD classes. The effect of sex was observed as a significant (P<0.05) low hardness in the hams obtained from female pigs. The duration of the ripening, for a better uniformity in dry-cured ham production, should be adapted to the initial pH and to drip loss parameters of the raw material.     

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.     

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).