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.     

Analysis of raw hams using SELDI-TOF-MS to predict the final quality of dry-cured hams

The relationship between protein profiles of Gluteus medius (GM) muscles of raw hams obtained from 4 pure breed pigs (Duroc, Large White, Landrace, and Piétrain) with the final quality of the Semimembranosus and Biceps femoris muscles of dry-cured hams was investigated. As expected, Duroc hams showed higher levels of marbling and intramuscular fat content than the other breeds. Piétrain hams were the leanest and most conformed, and presented the lowest salt content in dry-cured hams. Even if differences in the quality traits (colour, water activity, texture, composition, intramuscular fat, and marbling) of dry-cured hams were observed among the studied breeds, only small differences in the sensory attributes were detected. Surface-enhanced laser desorption/ionisation time-of-flight mass spectrometry (SELDI-TOF-MS) was used to obtain the soluble protein profiles of GM muscles. Some associations between protein peaks obtained with SELDI-TOF-MS and quality traits, mainly colour (b*) and texture (F₀, Y₂, Y₉₀) were observed. Candidate protein markers for the quality of processed dry-cured hams were identified.     

Chemical and structural changes in dry-cured hams (Bayonne hams) during processing and effects of the dehairing technique

Pigs of similar genetic backgrounds and feeding regimes were slaughtered in two abattoirs, one carrying out dehairing by scalding and the other by singeing. One ham from each of 80 carcasses was retained. Sixteen fresh hams (8 from each dehairing technique) were used for analysis while 64 hams were processed into dry-cured ham. Sixteen hams (8 from each dehairing technique) were taken for analysis at end of salting (day 14), end of rest (day 78), mid-processing (day 127) and end of processing (day 251). During processing, the water content of all muscles decreased while the salt content increased. The salt concentration in muscle water tended to equalize in all muscles. The nitrogen content of desalted dry matter (i.e. dry muscle tissue) decreased in both Biceps femoris and Semimembranosus. The content of every free amino acid increased with time, except for taurine and glutamine. Electrophoresis of the low ionic strength-soluble fractions showed all protein bands decreased during processing. Electrophoresis of the myofibrillar fractions indicated changes in all bands except actin (42kDa). These changes were more marked in the Semimembranosus than the Biceps femoris in the earlier processing steps. Ultrastructural changes were more marked in Semimembranosus than Biceps femoris. Hardness and chewiness increased in both muscles during the first half of processing then returned to values close to the initial ones in Semimembranosus but changed little in Biceps femoris. The scalded hams lost more weight than the singed ones during processing. The salt content was higher in scalded hams. Water-soluble nitrogen and NPN were higher in singed hams at the end of processing. The scalded hams were saltier and pungent. They had more pronounced aromas of dry ham, rancidity and hazelnut, and less aroma of fresh meat. Their texture was drier and less mellow.     

Changes of free amino acids and biogenic amines during extended ageing of Italian dry-cured ham

Sixty-two fresh hams were sub-grouped to undergo different processing times (15, 19 and 23 months), and corresponding dry-cured hams were analysed for changes in moisture, protein, NaCl, pH, proteolysis, free amino acids (FAAs) and biogenic amines (BAs) as related to the extended ageing. Dry-cured hams were influenced by ageing time, showing a decrease in moisture and water activity and an increase in pH, nonprotein nitrogen (NPN) and FAAs in more aged samples. The increase in FAAs and BAs progressively observed until the last sampling time might be enhanced by the moderate salt content (≈5 g NaCl/100 g muscle) and relatively high a_w (>0.90) of dried hams even at 23 months of processing. Among FAAs, arginine did not increase with ageing, which might be due to arginine hydrolysis to ammonia and ornithine, followed by decarboxylation to putrescine, i.e. molecules largely present in the more aged hams. Tyramine, the most abundant among BAs, putrescine and cadaverine showed a dependence on time and proteolysis indices (NPN and FAAs). In this respect, the practice of extending the standard ageing time of typical italian dry-cured ham (13-15 months), regarded as a tool for improving sensory property of this product, should be supported by further studies, mainly at the manufacturing level, to minimize FAA and BA generation.     

Relations between compositional traits and sensory qualities of French dry-cured ham

The left hams of 20 pig carcasses were processed by dry-curing for either 179 (n = 10) or 273 days (n = 10). The Biceps femoris was taken at the end of the processing and submitted to chemical and sensory analyses. The following chemical traits were determined: pH, moisture, salt content, fatty acid content and composition of lipid classes (triglycerides, phospholipids, free fatty acids), nitrogen fractions (soluble and insoluble protein, non-protein nitrogen, free amino acids) and volatile compounds. Sensory analysis was performed by a panel of 12 trained members, who scored texture traits (firmness, dryness, fibrousness, mellowness), taste (salty, acid), intensity of aromas (typical of dry ham, fresh meat, fat, cured meat, rancid, metal), persistence of dry ham aroma, persistence of taste after deglutition, persistence of astringency, persistence of metallic taste. The sensory qualities of dry-cured ham showed noticeable changes between days 179 and 273. Firmness, dryness and intensities of aromas typical of dry-cured ham and cured meat were enhanced with time. Neither pH, moisture nor salt content played a noticeable role in determining the sensory quality of dry-cured ham. Among the volatile compounds, the levels of several ketones and 1-butanol were significantly correlated with the aromas of dry ham and cured meat, while rancid aroma was related to aldehydes, ethylacetate, 2,3-pentanedione and nonane. Therefore, the aromas of dry ham and cured meat appeared to be determined mainly by the products of lipid oxidation. However, they were related also to unidentified volatile compounds, whose identification would be of particular interest.     

Influence of pre-cure freezing of Iberian ham on proteolytic changes throughout the ripening process

This work aimed to investigate the effect of pre-cure freezing Iberian hams on proteolysis phenomena throughout the ripening process. Non-protein nitrogen (NPN), peptide nitrogen (PN) and amino acid nitrogen (AN) as well as amino acid and dipeptide evolution followed the same trend in both refrigerated (R) and pre-cure frozen (F) Iberian hams during processing. At the different stages of ripening, there were no differences in the content of NPN and AN while F dry-cured hams had higher levels of PN than R hams at the final step. This seemed to be more related to the salt content (lower in F than in R hams) than to the pre-cure freezing treatment. Most amino acids and dipeptides detected showed higher concentrations in F than in R Iberian hams at the green stage, being rather similar at the intermediate phases. At the final stage, the effects of pre-cure freezing of Iberian hams were not well defined, higher levels of some amino acids and dipeptides were found in R than in F Iberian hams whereas other amino acids were lower in R than in F hams.     

Salt distribution in dry-cured ham measured by computed tomography and image analysis

Forty-seven hams were scanned four times by computed tomography (CT) while being manufactured into dry-cured hams. An image-processing algorithm measured CT values in the lean part of the hams and provided line profiles reflecting the magnitude and spatial location of salt gradients. At the end of manufacturing, seven entire hams were dissected and the salt content of the lean part determined. Likewise, in the remaining 40 hams, the lean meat of the slices corresponding to the CT images was dissected, analyzed chemically for NaCl and compared to the CT value. The salt content of entire dry-cured hams correlated well (r(2)=0.94) to the CT value of a 10 mm section located at the center of femur bone, perpendicular to the length axis of the hams. In the same position, significant correlations between the CT values before (r(2)=0.71) and after (r(2)=0.80) the ageing period and actual chemical analysis of the same section were demonstrated. Line profiles illustrating the combined salt distribution and dehydration within a ham related to the physical characteristics of the ham as well as to the manufacturing process. These findings reveal that the effects of altered manufacturing practices can be followed non-invasively, while hams are still in production. Computed tomography combined with appropriate image analysis offers advantages as a non-invasive tool in both research and product development.     

Phenotypic correlations among quality traits of fresh and dry-cured hams

In this study, fresh and processing quality traits were collected on a total of 312 Country Hams. Phenotypic correlations between traits were estimated and numerous values were significantly different (P<0.05) from zero. Yield was significantly correlated with several fresh pork quality traits measured on the fresh hams, including subjective color (0.34) and lipid percentage (0.32). Some meat color traits were significantly correlated, including associations between the color scores taken on the fresh and cured hams. Correlations between fresh pork quality traits were also determined, with results showing significant correlations between ultimate pH and other pork quality traits. The results indicate that yield can be maximized if hams with good fresh pork quality parameters are used for curing. The correlations estimates are helpful for understanding of the biological mechanisms behind the production of dry-cured hams and can potentially be used to improve the efficiency of the dry-cured ham production chain.     

FREE AMINO ACIDS AND DIPEPTIDES IN DRY-CURED HAM

Six types of dry-cured hams were chemically profiled for proximate composition and low molecular weight nonprotein nitrogen (NPN) fractions including free amino acids (FAA) and two dipeptides (carnosine and anserine). Results indicate that FAA were present in the six classes at different (mg/100g protein) concentrations, with Iberian and Serrano containing greater (P<0.05) amounts of most FAA. However, when analyzed as percentage (mg/100g total FAAs) values, FAA contents of Iberian and Serrano hams exhibited lower (P<0.05) tyrosine and greater (P<0.05) aspartic acid and threonine values. Within each class, large variation coefficients (>10%) for nonprotein nitrogen paralleled inconsistent values of salt content, to which NPN and FAAs were negatively correlated (P<0.01). NPN was also negatively affected by moisture in the dried muscle, indicating limited saltiness and greater muscle shrinkage as two major determinants in developing of nonprotein fractions, hence of free amino acids.     

The genetic relationship between enzymatic activity of cathepsin B and firmness of dry-cured hams

This study aimed to investigate the genetic relationship between enzymatic activity of raw hams and firmness of dry-cured hams. Instrumental firmness and sensory panel firmness scores were obtained from 2058 and 3275 dry-cured hams, respectively. On a sub-sample of 988 raw hams for dry-curing, enzymatic activity of cathepsin B was determined through a fluorimetric analytical method. A multiple-trait animal model was used to estimate heritability and genetic correlations of these traits. Estimates of heritability were moderate, ranging from 0.11 for sensory panel firmness scores to 0.25 for cathepsin B activity. Genetic correlations between firmness measures on dry-cured hams and enzymatic activity of raw hams were low. The efficiency of a selection program aimed to reduce the incidence of excessive softness in dry-cured hams on the basis of enzymatic activity of cathepsin B of raw hams is expected to be very limited.     

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.     

Use of computed tomography to study raw ham properties and predict salt content and distribution during dry-cured ham production

Varying salt content in hams of equal brand is a major challenge for Norwegian dry-cured ham producers. This study was thus undertaken to test existing computed tomography (CT) calibration models for salt on entire hams, regarding predictability of salt content at different processing times including final ham and to study salt distribution during processing of dry-cured ham. Twenty-six hams were scanned by computed tomography (CT) 11 times during dry-curing for this purpose. However, previously established calibration models had to be adjusted as they overestimated salt in dry samples. Prediction of ultimate salt content was more accurate approaching the end of the dry-curing process (RMSEP = 0.351-0.595% salt). Inclusion of remaining weight loss improved the prediction accuracy in un-dried samples by approximately 0.1% NaCl. The prediction errors were sufficiently low to be of practical interest.     

Sensory characteristics of Iberian ham: Influence of salt content and processing conditions

Sensory characteristics of Semimembranosus and Biceps femoris muscles from 24 dry-cured Iberian hams were assessed. Hams were salted with different amounts of salt (6% and 3% w/w) and then ripened at different temperature conditions (traditional processing vs. modified processing). Hams manufactured using modified processing showed higher scores for dryness (P<0.05), hardness (P<0.05) and rancid flavour (P<0.001) in the Semimembranosus muscle than those processed in a traditional way. The Biceps femoris muscle of hams salted with 6% of salt was drier (P<0.05), harder (P<0.05) and more fibrous (P<0.01) than in hams salted with 3% salt. Salty taste was more intense in the Semimembranosus and Biceps femoris from hams with a higher level of salt (P<0.01 and P<0.001, respectively). A more intense rancidity in hams ripened in modified processing could affect the overall aroma. A decrease in salt content produces less salty hams, but the changes in texture traits should be also considered.     

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.     

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.     

Bind, Sensory and Chemical Properties of Restructured Dry-cured Hams

Restructured, boneless, dry-cured ham product was processed from intact, bone-in, dry-cured hams (DC). Processing variables included tumbling and addition of ground, dry-cured ham meat. Restructured treatments were more tender (P<0.05), less salty (P<0.01), and had less off-flavors (P<0.05) with similar country ham flavor compared to the DC control. Addition of ground meat decreased tenderness (P<0.05) and increased Instron binding values. Tumbling decreased off flavors (P<0.05). Sensory bind scores of restructured hams were greater (P<0.05) than fresh, restructured controls (FR); however, Instron binding values were higher (P<0.001) for FR. An acceptable restructured product could be made from traditionally processed dry-cured hams.     

干腌肉制品低盐加工技术及其减盐机制研究进展

干腌肉制品因其独特的风味而深受消费者的喜爱,但较高的含盐量制约了其进一步发展。随着人们对适度低盐饮食的关注,如何在保证产品品质和安全性的同时实现减盐的目的成为该领域的研究热点。本文在分析钠盐含量与干腌肉制品品质关系基础上,从钠盐替代物、真空/超高压/超声波/脉冲电场等新型腌制技术、增强咸味感知技术3 个方面综述当前的低盐加工策略及技术,并探讨不同减盐方法的减盐机制、咸味感知机理以及对产品品质特性的影响,指出现有研究和技术的局限性,以期为低盐干腌肉制品的研发提供一定的理论和技术参考。     

RELATIONSHIPS BETWEEN MUSCLE TISSUE CHARACTERISTICS AND SENSORY QUALITIES OF DRY-CURED HAM

Forty dry-cured hams were identified at the end of 9 months processing. The Biceps femoris was analyzed for dry matter, pH, protein, lipids, acid value, hydroxyproline, Cl^-, pigment, glycogen, lactic acid and protein fractions, and average diameter and metabolic type of fibers. Sensory analysis involved color scoring on a whole slice of ham; assessment (by sniffing) of the acceptability on the semimembranosus of all 40 hams; and evaluation of odor, texture, taste and aroma on the biceps femoris of 26 hams. Among the traits under study, dry matter, glycogen, lactic acid, Cl^- and pH appeared as the most important determinants of sensory qualities of dry-cured ham. High levels of glycogen, lactic acid and Cl^- and low pH were associated with dry texture and high intensity of dry ham and cured meat aroma. The other components studied revealed scarce and generally low correlations with sensory traits.     

Color Formation in Nitrite-Free Dried Hams as Related to Zn-Protoporphyrin IX and Zn-Chelatase Activity

ABSTRACT:  The development of red pigment Zn-protoporphyrin IX (ZPP) in nitrite-free Parma hams was investigated in 5 leg muscles at several stages of processing and the activity of muscle Zn-chelatase was concurrently assayed for its potential role in ZPP formation. A steady increase of the pigment was observed throughout the manufacturing stages at mild temperatures while no development was observed during the prior cold resting phase. The enzyme was partly inactivated according to a muscle-dependent pattern, resulting in similar ZPP contents, hence color, in finished hams. It is concluded that enzyme-dependent synthesis of ZPP in nitrite-free dried hams contributes to color development, enabling muscles in dried hams to become more similar in redness than in green thighs. Therefore, checking raw meat for the enzyme content may be a means to control color formation in nitrite-free dry-cured meat derivatives.