Muscle individual phospholipid classes throughout the processing of dry-cured ham: Influence of pre-cure freezing

This paper aims to study the profile of phospholipid (PL) classes of Iberian ham throughout its processing and the changes it underwent due to the influence of the pre-cure freezing treatment. The general profile of each PL class did not vary during the ripening stage. Phosphatidylcholine (PC) showed the highest proportion, followed by phosphatidyletanolamine (PE) and phosphatidylserine (PS) and phosphatidylinositol (PI) being the minor PL. The four PL classes were highly hydrolysed during the salting stage and their degradation continued during the rest of the processing. Pre-cure freezing of Iberian ham influenced the levels of the four PL classes at the initial stage, all of them being higher in refrigerated (R) than in pre-cure frozen (F) hams. Moreover, the pattern of hydrolysis was not the same in these two groups.     

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.     

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.     

Influence of pre-cure freezing of Iberian hams on lipolytic changes and lipid oxidation

The purpose of this work was to study the influence of pre-cure freezing of Iberian hams on lipolysis and lipid oxidation during the ripening of the product. At the green stage, the levels of fatty acids (FA) in the free fatty acids fraction were higher in pre-cure frozen (F) than in refrigerated (R) hams, whereas in the polar lipid fraction, FA and dimethyl acetals (DMA) values were higher in R than in F Iberian hams. These results point out the existence of lipolysis phenomena during the freezing storage. At the end of post-salting and at the final stage, both R and F hams showed similar FA and DMA profiles. The effect of pre-cure freezing of hams influenced lipolysis evolution throughout the processing. The development of lipid oxidation was similar in R and F hams, but Thiobarbituric acid-reactive substances (TBAR) values were significantly higher in F hams at the initial stage and at the end of post-salting and drying steps. Despite all these differences, at final stage the FA and DMA composition as well as TBAR levels were quite similar in R and F hams.     

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.     

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.     

Evolution of volatile aldehydes in Iberian ham matured under different processing conditions

To evaluate the influence of the Iberian ham processing conditions in the evolution of volatile aldehydes, 35 hams were processed in two plants following different conditions of relative humidity and temperature. For this, free fatty acids, peroxide values and volatile aldehydes were quantified in the hams. The highest increases in free fatty acids were noted during the drying stage in both processing plants. The drying period also revealed the greatest increase in peroxide values, where the highest values were in those hams processed at higher temperatures. The temperature during post-salting and drying had a marked influence on the formation of volatile aldehydes, being responsible for the differences in volatile compounds of matured hams.     

Effect of intensifying high‐temperature ripening on proteolysis,lipolysis and flavor of Jinhua ham

BACKGROUND: The flavor quality of dry‐cured ham comes from proteolysis, lipolysis and lipid oxidation, Maillard reaction and Strecker amino acid degradation. Intense proteolysis, lipolysis and lipid oxidation make major contributions to flavor development of dry‐cured ham. Increasing the temperature in fermenting and ripening could promote these reactions and accelerate flavor development in dry‐cured hams. The specific aroma flavor of Jinhua ham is developed only during long‐time high‐temperature ripening in July and August. Our objective was to effectively shorten the process time by intense high‐temperature ripening based on the flavor and quality features of traditional Jinhua ham. RESULTS: Muscle dehydration rate of 80‐day ripened hams (29.43 ± 1.16%) was higher than that of the traditional process (P < 0.05). The total free fatty acids in ripened hams of 45–80 days were all higher than that of traditional hams (P < 0.05) and the level of TBARS was significantly lower (P < 0.01). The flavor profile of modern‐processed hams was different from that of the traditional Jinhua ham. The contents of carboxylic acids and aldehydes were obviously higher than those of the traditional products (P < 0.05). The results of organoleptic evaluation for flavor and quality showed that 80‐day ripened hams reached the first‐grade level of traditional Jinhua ham. CONCLUSION: Long‐time (25–30 days) intensifying high‐temperature ripening (35–37 °C) could accelerate the proteolysis, lipolysis, lipids oxidation, flavor development and effectively shorten the process time based on the traditional flavor and quality features of dry‐cured ham. Copyright © 2009 Society of Chemical Industry     

Influence of partial replacement of NaCl with KCl on formation of volatile compounds in Jinhua ham during processing

The influence of partial replacement of NaCl with KCl on formation of volatile compounds during Jinhua ham processing was evaluated using GC/MS system. Jinhua ham was treated with either 100% NaCl (I) or 60% NaCl and 40% KCl (II). Formation of volatile compounds increased in Jinhua hams during processing for both salt formulations, particularly at the end of the salting period. There were differences in volatile compound formation between formulations I and II after 45 days of processing. Contents of lipid-derived volatiles (hexanal) and Strecker aldehydes (2-methylbutanal and 3-methylbutanal) were higher in Jinhua hams treated with formulation II after 45 days of processing. Partial salt replacement of NaCl with KCl changed formation of volatile compounds in Jinhua hams and may have affected the flavor of finished products.     

Changes in the volatile flavour components of Jinhua ham during the traditional ageing process

Changes in volatile flavour compounds of Jinhua ham were studied during the traditional ageing process of sun‐drying, loft‐ageing and post‐ageing. About seventy‐eight volatile compounds were tentatively identified, including aldehydes (ten to fifteen), carboxylic acids (eight to ten), alcohols (thirteen to fourteen), ketones (eight), esters (eight to ten), aromatic hydrocarbons (five), sulphur‐containing compounds (two to three) and pyrazines (zero to four) which were the main components. The percentage content of aldehydes and ketones reduced over time as the temperature rose with each stage of the process, whereas alcohols, carboxylic acids, esters, pyrazines and sulphur‐containing compounds increased gradually. Jinhua ham's high‐temperature maturating process (40 days at 30–37 °C) made the percentage content of carboxylic acids arising from Maillard reactions markedly increase (from sun‐dried ham 8.45% to fully aged ham 19.23%). This was the most obvious difference between Jinhua ham and the Mediterranean dry‐cured hams, and was the main factor leading to the unique flavour of Jinhua ham.     

Free amino acids and other non-volatile compounds formed during processing of Iberian ham

Fifty-five legs from Iberian pigs were traditionally processed into dry cured hams. Free amino acids and other non-volatile compounds in the water-soluble fraction from the biceps femoris muscle were analyzed by HPLC. At the drying stage and in the last months in the cellar the largest increases in these water-soluble compounds took place. There was a clear influence on free amino acid formation of salt content and on the formation of peptides of the temperature at each processing stage. As the amount of non-volatile compounds in the water-soluble fraction increases with processing time, their determination could provide a maturation index for Iberian ham.     

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.     

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.     

金华火腿中挥发性风味物质形成过程及变化规律研究

以60只杂交猪后腿为原料,按照传统工艺加工金华火腿,采用固相微萃取(SPME)技术和气谱-质谱联用仪(GC-MS)分离、鉴定技术,研究了金华火腿股二头肌中挥发性风味化合物的形成变化规律。从6个不同加工时期的样品中共鉴定出191种物质,包括43种烃、31种醛、24种酮、21种酯、19种醇、17种羧酸、16种杂环化合物、5种内酯、5种含氯化合物、4种含硫化合物、2种酚、2种酸酐、1种酰胺和1种醚。其中醛类、醇类、烃类、酮类、酸类和酯类化合物含量较高,但各类风味物质的化合物种类和含量的变化规律各不相同。随着加工进行,肌肉中的挥发性化合物种类逐渐增多,但化合物总含量以晒腿结束和成熟中期最高。研究结果表明,与国外干腌火腿相比,金华火腿成品中羧酸、支链化合物、芳香族化合物及杂环化合物种类和含量较多,可能是金华火腿的风味特征。     

Biochemical changes during processing of traditional Jinhua ham

Jinhua ham is the most famous traditional meat product of China and one of the most famed dry-cured hams in the world. Its processing consists of six stages: green ham preparation, salting, washing and sun-drying and shaping, ripening, and post-ripening. Intense proteolysis and lipolysis occur during processing period. As a result, the content of free amino acids in final ham products is 14-16 times that of green ham, and 191 volatile compounds have been identified during processing, which make a major contribution to the flavor of Jinhua ham.     

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.     

A tentative characterization of white dry-cured hams from Teruel (Spain) by SPME-GC

Forty-six volatile compounds were identified and quantified in four parts (subcutaneous fat, and biceps femoris, semitendinosus and semimembranosus muscles) of 41 samples from Spain, France and Italy. The Univariate Brown–Forsythe test was used to determine the volatile compounds from each part of the ham that can distinguish the hams of Teruel from Iberian and white hams. Stepwise linear discriminant analysis was used in-tandem to refine the most discriminating volatile compounds. Six compounds (2-propanone, butanol, 3-methylbutanol, 3-methylbutanal, hexanal and limonene) were able to distinguish the dry-cured hams from Teruel, Iberian hams, and French and Spanish white hams simultaneously. MDS was also applied to the volatiles selected by SLDA. Information on the series of volatiles and individual compounds is also displayed.     

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.     

Effect of Iberian × Duroc genotype on composition and sensory properties of dry‐cured ham

BACKGROUND: Dry‐cured ham quality from three different Iberian × Duroc genotypes was studied: GEN1, Iberian × Duroc1; GEN2, Duroc1 × Iberian; GEN3, Duroc2 × Iberian. GEN1 and GEN2 are reciprocal crosses, while the difference between GEN2 and GEN3 is the Duroc sire line. The line Duroc1 (DU1) was selected for the manufacture of dry‐cured meat products, whereas the line Duroc2 (DU2) was selected for meat production with low carcass fat. RESULTS: Dry‐cured hams from all genotypes had similar chemical composition. However, intramuscular fat of dry‐cured hams from GEN3 was more unsaturated than that from GEN2, while GEN1 was intermediate. Lipid oxidation, measured as 2‐thiobarbituric acid‐reactive substances (TBARS) and hexanal content, was similar between genotypes. The colour of hams was affected by genotype; hams from GEN2 showed higher lightness (CIE L*), while those from GEN3 had a less intense colour (lower a* and C*). Texture measured instrumentally did not differ between genotypes; however, in the sensory analysis, panellists considered hams from GEN3 more fibrous, while those from GEN2 were considered juicier. Hams from GEN3 were also perceived as saltier and more acid. CONCLUSION: Genotype affected the quality of Iberian hams, with those from GEN3 being of lower quality, and this genotype was considered less suitable for the manufacture of Iberian dry‐cured ham. Copyright © 2007 Society of Chemical Industry     

Study of salting and post-salting stages of fresh and thawed Iberian hams

Fresh raw material has been traditionally used to obtain dry-cured Iberian ham, although the use of thawed raw material is increasing. This type of raw material has been previously studied for dry-cured production employing White pigs, where the salting time has been reduced to reach similar NaCl concentrations. The aim of this work was the analysis of salting and post-salting stages of Iberian hams, employing fresh or thawed raw materials. The results showed that fresh Iberian hams had higher salt concentrations than thawed Iberian hams for the salting time ratio used, a ratio established to reduce the freezing/thawing effect that was previously observed working with White ham. This fact shows that the Iberian raw material in dry-cured ham manufacturing is less affected, by the freezing/thawing process than the White raw material.