Effect of prefreezing hams on endogenous enzyme activity during the processing of Iberian dry-cured hams

The use of frozen/thawed raw material in the processing of Iberian dry-cured ham has been studied to determine its effect on the sensory quality of the final product. The proteolysis and lipolysis processes were measured by the proteolytic and lipolytic enzyme activities and free amino acids and free fatty acids. The thawed Iberian hams had lower salt contents throughout the process. The use of thawing raw material did not affect the proteolytic enzymes, cathepsins, aminopeptidases and dipeptidylpeptidases, only the activity of dipeptidylpeptidase III was reduced due to thawing. Moreover, there were no differences in the content of free amino acids between fresh and thawed hams during the whole process. However, the use of thawing hams affected the lipolytic activity. The activity of phospholipase and neutral lipase were significantly higher in the thawed hams and also the content of free fatty acids, at all the stages analyzed. Consumer sensory analysis showed thawed Iberian hams had the lowest hardness, probably due to an intense proteolysis. The acceptability of the Iberian hams was similar between fresh and thawed hams.     

Use of simultaneous brine thawing/salting in dry-cured Iberian ham production

The study of simultaneous brine thawing/salting as an alternative to the traditional stages in Iberian dry-cured ham processing was carried out employing 75 pre-cured frozen hams from Iberian pigs. The frozen hams were simultaneously thawed and salted with saturated brine for periods of 3, 5, and 7 days with and without the application of a vacuum pulse in order to reach the same salt concentration as the traditional procedure. The post-salting behaviour of the brine/thawed hams was also studied. The results obtained indicated that simultaneous thawing and salting would considerably reduce the time needed to reach the same salt concentration as with the traditional procedure (77% and 63% reduction with and without vacuum pulse, respectively). This also implied lower dehydration, so an increase in the post-salting time or in the weight lost during this stage is required.     

Post-salting studies in Spanish cured ham manufacturing. Time reduction by using brine thawing-salting

The use of the simultaneous brine thawing/salting on frozen raw material was compared in a previous work with the traditional pile salting method. The aim of this study was to characterise and compare the post-salting stage in Spanish cured ham production by processing fresh and thawed raw material with the traditional pile salting method (which can be considered as the reference method), with the results obtained using the brine thawing/salting method, with and without applying vacuum impregnation. The obtained results show that the thawed salted hams exhibited a higher NaCl diffusion than the fresh ones, implying a shorter post-salting period. Post-salting stage could be reduced from the 50 days employed in the traditional fresh raw material salting, to 25 days when using frozen hams brine thawed/salted. No influence of the use of vacuum impregnation during the salting stage was observed on the post-salting period.     

Accelerated processing of dry-cured ham. Part I. Viability of the use of brine thawing/salting operation

In a previous study, the brine thawing/salting operation using frozen hams as raw material was proposed in order to obtain accelerated processing of dry-cured hams. The time needed to reach the same NaCl concentration on a dry weight basis and the same NaCl concentration in the ham liquid phase for the deeper areas at the end of the post-salting stage were determined.

The aim of this work was to study the influence of the brine thawing/salting operation on the whole dry-cured ham manufacturing process, using the traditional thawing and salting methods as control.

The obtained results indicate that although a strong reduction in the thawing, salting and post-salting stages is obtained by using brine thawing/salting, the time needed in the dry-curing and maturing phases increases compared to those traditionally processed, probably due to the absence of pile salting and thus the reduction in the thickness of the ham piece as a consequence of the ham pressing. From the composition and microbiological point of view, no significant differences were observed among the hams processed by the different treatments.     

The effect of using PSE meat in the manufacture of dry-cured ham

 Drying, salting, protein changes, colour and the sensory quality were studied in dry-cured ham manufactured from refrigerated and frozen/thawed raw pale, soft and exudative (PSE) meat. The results obtained showed that the use of PSE meat increases the level of drying, salting and proteolysis of the dry-cured ham, although it does not significantly affect the sensory quality. Freezing and thawing of the raw material accentuates the proteolytic and exudative nature of the meat during the curing process, and as a result the salting and drying levels increase to such an extent that the PSE effect in these hams is practically undetectable. Received: 6 June 1997 / Revised version: 17 July 1997     

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.     

Pre-cure freezing affects proteolysis in dry-cured hams

Several parameters (sodium chloride, moisture, intramuscular fat, total nitrogen, non-protein nitrogen, white precipitates, free tyrosine, L* a* b* values and acceptability) related with proteolysis during the curing were compared in dry-cured hams manufactured from refrigerated and frozen/thawed raw material. Pre-cure freezing increased the proteolysis levels significantly (p<0.05) in the zones of the ham where water losses and absorption of salt is slowest. Frozen hams present a high incidence of white precipitates, formed mainly by tyrosine crystals. The colour and acceptability scores are similar in frozen and refrigerated hams. The previous freezing and thawing process accentuates the water losses, salt absorption and proteolysis of the cured meat, although it does not significantly affect the sensory quality of the dry-cured ham.     

Effect of brine thawing/salting on endogenous enzyme activity and sensory quality of Iberian dry-cured ham

Simultaneous brine thawing/salting process was applied as an alternative to traditional pile salting process using 51 frozen Iberian hams. The effect of this type of salting process on endogenous enzyme activity and sensory quality of Iberian dry-cured hams was analysed. The frozen hams were simultaneously thawed and salted with saturated brine, with and without vacuum pulses, and were compared to hams thawed under refrigeration and traditionally salted. The peptidase and lipase activities were measured at the end of salting and post-salting stages. The activity of cathepsin B+L was reduced in the two brine salted batches while few differences among batches were observed for the other peptidases. Several lipase activities were significantly reduced in the two brine salted batches. The brine thawed processing affected the free fatty acid content at the different stages although the differences were more appreciated at the beginning of the process and no differences were observed at the end. The long ripening time makes these differences negligible and the consumer did not appreciate any differences between the sensory quality of Iberian brine/thawed hams and traditional Iberian thawed pile salted hams.     

Analysis of raw meat to predict proteolysis in Parma ham

Four hundred and thirty-seven pigs (223 purebred Italian Large White, 97 Italian Landrace, and 117 Duroc), were studied to examine the effect of breed on meat quality and assess the possibility of relating proteolysis of dry-cured hams to raw meat quality. The Duroc pigs had intramuscular fat contents and water holding capacities (M. Semimembranosus) significantly higher than those of the Large White and Landrace. The latter had a significantly higher pH(24h) and cathepsin B activities significantly lower than the Duroc breed. The dry-cured hams (M. Biceps femoris) from the three breeds were significantly different in proximate composition, proteolysis and weight loss at the end of ageing. Data for green hams (including salt content) were used to compute a model to fit the proteolysis of the corresponding dry-cured hams. The variables included in the model (R(2)=0.53 and P<0.01) were cathepsin B activity of raw ham, pH(24h), weight loss after the first salting step, and the salt content of the dry-cured ham. The raw hams with the highest cathepsin B activities, the lowest pH(24h), and the highest weight loss after the first salting were those in which greatest proteolysis occured.     

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.     

Lipolytic and proteolytic properties of dry-cured boneless hams ripened in modified atmospheres

We studied proteolytic and lipolytic properties of dry-cured boneless ham (porcine quadriceps femoris) made with chilled (10°C, 48 h) or frozen/thawed meat (frozen at -20°C frozen for 90 days and followed by thawing at 10°C for 48 h) were determined. Dry-cured meats were stored in modified atmosphere packages (100% N(2) and a mixture of 75% N(2)+25% CO(2)) at 15°C with the intention of reducing ripening space. Results showed that dry-cured hams made with frozen/thawed raw meat had more salt, volatile fatty acids and free fatty acid content after salting and smoking. Whereas, samples prepared with chilled meats contained more nitrogenous compounds (water-soluble nitrogen, non-protein nitrogen, and free amino acids). Volatile and free fatty acid contents in all samples significantly increased with storage. Acetic acid was the predominant volatile fatty acid. To confirm lipolytic activity in dry-cured ham stored in modified atmospheres, we calculated the lipolytic coefficient. The lipolytic coefficients of all samples were positive values and significantly (P<0.05) increased with storage indicating lipolysis in samples were still active. Furthermore, nitrogenous compounds in dry-cured ham significantly (P<0.05) increased with storage indicating proteolysis in samples were not affected by modified atmosphere storage. Aerobic, anaerobic and lactic acid bacteria counts in dry-cured meats were stable to modified atmospheres storage for 20 weeks at 15°C. Flavor, texture and color score in sensory evaluation for dry-cured ham made with chilled meat were significantly higher than that made with frozen/thawed meat. All samples had high overall acceptance scores in sensory evaluation. Results in this study suggested that dry-cured boneless ham stored in modified atmospheres for 20 weeks at 15°C was another feasibility to ripen the meat without affecting lipolysis, proteolysis, microbiology and sensory quality.     

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.     

Relationships of genotype and slaughter time with the appearance and texture of dry-cured hams

The influence of genetics and slaughter time on the sensory characteristics of dry-cured hams was studied. To this end, 341 dry-cured hams, selected from 1257 pigs from five different crosses, including Duroc, Landrace and Large White, in five slaughters distributed over a year (namely, December 2000, March, April, July and November 2001) were sensorially evaluated according to the ISO 8586-2:1994. The sensory parameters assessed were pastiness, softness, colour, ring colour, crusting and marbling. Analysis of the results revealed that both the genetics and slaughter time had a significant effect on the dry-cured ham quality. Thus, warmest months provide dry-cured hams of the highest quality, but with a higher incidence of crusting. Dry-cured hams with the best sensory evaluation for texture and colour were from crossbreed A [(LR × LW) × DU]; while crossbreed D [(LR × LW × DU) × DU] provided the highest percentage of faulty dry-cured hams, except for incidence of crusting. Other parameters, such as the ham weight, relationship between salting days and ham weight, pH before salting and total weight loss, also influenced the properties of the end-product.     

Electronic nose for the identification of pig feeding and ripening time in Iberian hams

An electronic nose system to control the processing of dry-cured Iberian ham is presented. The sensors involved are tin oxide semiconductors thin films. They were prepared by RF sputtering. Some of the sensors were doped with metal catalysts as Pt and Pd, in order to improve the selectivity of the sensors. The multisensor with 16 semiconductor sensors, gave different responses from two types of dry-cured Iberian hams which differ in the feeding and curing time. The data has been analysed using the PCA (principal component analysis) and backpropagation and probabilistic neural networks. The analysis shows that different types of Iberian ham can be discriminated and identified successfully.     

Data Mining on MRI-Computational Texture Features to Predict Sensory Characteristics in Ham

In this study, data mining technique was applied on computational texture features obtained from the analysis of magnetic resonance imaging (MRI) of hams, with the main objective of determining sensory attributes of dry-cured ham non-destructively. For that, fresh and dry-cured hams were scanned and then the MRI images were analyzed by three methods of computational texture features. Data mining was applied on the computational texture features from fresh and dry-cured hams for obtaining prediction equations of the sensory attributes of dry-cured hams. The correlation coefficient (R) was used to analyze the results. Accurate prediction was found for 13 sensory attributes as a function of computational texture features of fresh ham, and three from dry-cured ham. In addition, a sensory analysis of dry-cured hams was also carried out to validate the predicted results. Similar values were found between the predicted attributes and those determined by sensory analysis. Thus, it is possible to predict sensory attributes of dry-cured hams by applying data mining on computational texture features of MRI from fresh and dry-cured hams. This supposes the chance of determining non-destructively sensory attributes of dry-cured hams, even before the curing process starts.     

Effect of high-pressure treatment on the survival of Listeria monocytogenes Scott A in sliced vacuum-packaged Iberian and Serrano cured hams

High-pressure treatment is useful for increasing the microbiological safety of ready-to-eat foods. With dry-cured hams, this treatment can be applied to the finished product after slicing and vacuum packaging. The effect of high-pressure treatment on the survival of inoculated Listeria monocytogenes Scott A and on the sensory characteristics of two Spanish dry-cured hams, Iberian and Serrano, was investigated. Ham slices were inoculated with L. monocytogenes at 6 x 10(6) CFU/g and held at 4 degrees C for 20 h before high-pressure treatment. During this holding period, the population of the pathogen declined by 0.44 and 0.51 log CFU/g in Iberian and Serrano hams, respectively. Treatment at 450 MPa for 10 min at 12 degrees C reduced L. monocytogenes populations by 1.50 and 1.16 log CFU/g in Iberian and Serrano hams, respectively. During the first week of storage at 4 or 8 degrees C, L. monocytogenes populations declined by an average 0.89 log CFU/g in pressurized Iberian ham and 2.09 log CFU/g in pressurized Serrano ham. After 60 days at 4 or 8 degrees C, the respective populations in pressurized and control hams were 3.24 and 4.70 log CFU/g for Iberian ham and 2.73 and 5.07 log CFU/g for Serrano ham. The color parameters L* and a* were not influenced by high-pressure treatment, and parameter b* was increased only in Iberian ham. Sensory characteristics of hams were not affected by high-pressure treatment. Treatment of Iberian and Serrano hams at 450 MPa for 10 min significantly reduced the population of L. monocytogenes Scott A without a detrimental effect on the sensory characteristics of the hams.     

Influence of pre‐cure freezing on the profile of volatile compounds during the processing of Iberian hams

BACKGROUND: This work was designed to study the effect of pre‐cure freezing of raw thighs from Iberian pigs on the profile of volatile compounds during the processing of hams. RESULTS: Generation of volatile compounds during Iberian ham processing was similar in both pre‐cure frozen and refrigerated hams, the main differences being at the final stage. The levels of 2‐methylbutanal, 2‐methyl‐1‐butanol, 2,3‐butanediol and 2‐heptanol were significantly higher in dry‐cured hams that were pre‐cure frozen than in refrigerated ones, whereas the content of most detected esters was statistically lower in pre‐cure frozen than in refrigerated hams. CONCLUSION: The effect of pre‐cure freezing of Iberian ham on the profile of volatile compounds during ripening was not remarkable. Few differences were found in the final product, which would not greatly modify the aroma and flavour features of the dry‐cured hams. Copyright © 2010 Society of Chemical Industry     

Characterisation of the most odour-active compounds of bone tainted dry-cured Iberian ham

The most odour-active compounds of different bone tainted dry-cured Iberian hams were researched using the detection frequency method. Most of the odourants identified were found in all the Iberian hams (spoiled and unspoiled). Some compounds (ethyl butanoate, dimethyl disulfide, phenylacetaldehyde, acetic, propanoic, butanoic, 3-methylbutanoic and pentanoic acids) were identified in the spoiled hams as Iberian ham odourants for the first time. The detection frequency (DF) values for the spoiled and the unspoiled hams were markedly different. The main differences were found for 2-methylpropanal, ethyl-2-methylpropanoate, ethyl-2-methylbutanoate, phenylacetaldehyde and methional (the lowest DF values were found in the unspoiled ham) and hexanal (the largest DF value was found in the unspoiled ham). Spoiled hams with a different global odour had different DF values.     

中西方干腌火腿风味成分比较及形成机理分析

风味对干腌火腿的质量十分重要 ,它与生产所用原料、生产工艺和参数密切相关。文中比较了金华火腿与欧洲几种著名火腿的风味成分 ,结果显示 ,中西方火腿的风味组成相似 ,醇、醛、酮、酯、含硫化合物、含氮化合物、烷、烯烃类物质是干腌火腿的共有成分 ,但各成分的含量在中西方火腿中存在明显差异 ,金华火腿中烷、烯烃含量最高 ,欧洲的几种火腿中醛类物质含量最高。文中同时分析了干腌火腿中各风味成分的特征和可能的形成机理。