Time-related changes in nitrogen fractions and free amino acids of lean tissue of frech dry-cured ham

The 80 hams of 40 pig carcasses from one slaughter batch were taken on the day after slaughter. The 40 left hams were dry-cured. Groups of 10 hams were taken for analysis at 74 days (end of rest), 81 days (end of heating), 179 days (mid-seasoning) and 273 days (end of seasoning) after the beginning of processing. A slice of about 150 g was taken in the middle of the Biceps femoris and used for analysis of nitrogen fractions and free amino acids by HPLC. Levels of insoluble nitrogen compounds did not vary significantly, while levels of soluble protein nitrogen decreased strongly from 26 to 16% of total nitrogen, with the fastest decrease observed between days 179 and 273. Levels of non-protein nitrogen increased regularly during the processing from 12 to 23% of total nitrogen. Nitrogen of free amino acids ranged from 3·6% in fresh muscle to 16·6% of total nitrogen at day 179, then decreased to 4·4% of the total nitrogen at the end of the processing. The HPLC method allowed the identification of 29 compounds, among which 27 were amino acids and 2 were dipeptides. The average levels of free amino acids of non-protein origin tended to decrease before day 74, then to increase until day 179 and to decrease again. The levels of compounds of protein origin increased or tended to increase from the beginning until day 179, then decreased.     

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.     

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.     

Effect of pH(24), NaCl content and proteolysis index on the relationship between water content and texture parameters in biceps femoris and semimembranosus muscles in dry-cured ham

The aim of the present study was to determine the effect of pH level and NaCl content on the relationship between water content and texture parameters in semimembranosus and biceps femoris muscles in dry-cured ham. The experiment was undertaken using 18 hams, selected in a commercial slaughterhouse. Half of the hams had a pH<5.7 and the rest a pH>6.2, measured in the semimembranosus muscle at 24-h post mortem (pH(SM24)). The hams were treated with 20, 50 or 80g of NaCl per kg of ham. At the end of the aging process nine samples from semimembranosus and biceps femoris muscles were dried to different levels of water content covering the range from 22.4% to 58.5%. At the end of the drying period, a Texture Profile Analysis was used to determine textural parameters. Samples from biceps femoris muscle and samples from hams with low pH(SM24) showed a higher proteolysis index (100×non-protein nitrogen/total nitrogen) than samples from semimembranosus muscle and samples from hams with high pH(SM24), respectively. The proteolysis index decreased when the added NaCl amount increased. The proteolysis index was the parameter that best explained the modifications in the relationship between water content and the texture parameters (hardness, cohesiveness and springiness) of dry-cured ham muscles and it would be considered in order to predict the texture in dry-cured ham at different drying levels. Dry-cured hams with a lower proteolysis index were more prone to present harder texture at low water contents, which is typical of hams with crustiness problems.     

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.     

Changes of alanyl aminopeptidase activity and free amino acid contents in biceps femoris during processing of Jinhua ham

Sixty experimental Jinhua hams were processed by a traditional method. The potential alanyl aminopeptidase (AAP) activity in biceps femoris was determined. The effects of temperature, salt content, sodium nitrate content and pH on muscle AAP were evaluated using response surface methodology. Porcine muscle was found to possess very strong potential AAP activity that decreased gradually during processing from 201,635 U g⁻¹ before salting to 6147 U g⁻¹ after aging. Temperature, pH and salt content had significant exponential effects on AAP activity (P < 0.001). Both temperature and salt content interacted with pH in their effects on AAP activity (P < 0.01). However, 0–50 mg L⁻¹ sodium nitrate had no detectable effect on AAP activity (P > 0.05). The regression model showed muscle AAP maintaining its activity all through Jinhua ham processing, indicating that muscle AAP may generate free amino acids during the processing and storage of Jinhua ham. The concentrations of free amino acids increased significantly (P < 0.05) during Jinhua ham processing, except for arginine and cystine. The concentrations of most free amino acids were 5–20 times higher in the final product than in hams before salting. Final concentrations exceeded thresholds for sensory detection, thus implicating an important role of free amino acids in the determination of Jinhua ham flavor.     

部分KCl替代NaCl对强化高温成熟工艺干腌火腿肌肉色泽形成的影响

采用强化高温成熟现代工艺(36℃强化高温成熟45 d,用盐量6.5%,以火腿质量计)制作干腌火腿,分析加工过程中火腿半膜肌盐分含量、水分含量、p H值、色差值、肌红蛋白氧化状态、血红素类色素和锌卟啉(Zn-protoporphyrin,Zn-PP)Ⅸ含量,研究火腿色泽的形成及KCl替代Na Cl对火腿加工过程中色泽变化的影响。结果表明:盐量30%KCl替代Na Cl对干腌火腿产品理化特性、色差值及色素状态和含量没有显著影响(P0.05);干腌火腿的独特色泽是由肌红蛋白的氧化状态、红色色素的含量及肌肉组织的状态共同形成的,火腿加工过程中氧合肌红蛋白(oxymyoglobin,OMb)和高铁肌红蛋白(metmyoglobin,MMb)相对含量分别上升约22.07%和25.21%,脱氧肌红蛋白(deoxymyolglobin,DMb)相对含量下降约47.27%,DMb与亮度L*值呈极显著正相关(P0.01),OMb、MMb与L*值呈极显著负相关(P0.01),并受OMb与MMb相对含量比值极显著影响(P0.01)。在较低范围内(0%~27.49%),MMb相对含量越高红绿度a*值越大,并且MMb的影响力大于OMb。血红素类色素和Zn-PPⅨ含量在火腿加工过程中都显著增加,约394%和5 296%,并与a*值和色饱和度C值呈极显著正相关关系(P0.01)。     

Time-related changes in volatile compounds of lean tissue during processing of French dry-cured ham

The Biceps femoris muscles from 50 hams were used in the study. Ten samples were taken for analysis on the day after slaughter. Forty hams were drycured and taken for analysis by groups of 10 at days 74, 81, 179 and 273 after the beginning of processing. Volatile compounds were extracted from the middle part of the Biceps femoris muscle by dynamic headspace extraction, then analysed by gas chromatography and mass spectrometry. More than 100 peaks were detected, among which 74 were identified and 52 were quantified. Most identified compounds originated from either lipid oxidation or amino acid degradation. The total quantity of extracted compounds increased dramatically between day 0 and day 74. Propanone was by far the most abundant compound, followed by the other ketones, alcohols and aromatic hydrocarbons (66·5, 9·9, 9·2 and 8·4% of the total chromatogram area, respectively, at the end of processing). The levels of individual compounds varied greatly during processing. There was some evidence of independence between the reactions producing volatile compounds from lipids and those involving amino acids.     

Changes of arginyl and leucyl aminopeptidase activities in biceps femoris along Jinhua ham processing

Sixty experimental Jinhua hams were processed by a traditional method. The potential arginyl (RAP) and leucyl (LAP) aminopeptidase activities in biceps femoris were determined. The effects of temperature, salt content, sodium nitrate content and pH value on muscle RAP and LAP activities were evaluated using response surface methodology. Porcine muscle was found to possess very strong potential RAP and LAP activities that decreased gradually during processing from 165,980.97Ug(-1) and 89,201.52Ug(-1) before salting to 3164.70Ug(-1) and 5373.66Ug(-1) after aging, respectively. Temperature, pH value and salt content had significant effects on RAP and LAP activities (P<0.0001). They interacted with each other in their effects on RAP activity (P<0.0001) and influenced LAP activity in exponential way (P<0.05). However, 0-50mgL(-1) sodium nitrate had no detectable effect on either RAP or LAP activity (P>0.05). The regression models showed that muscle RAP and LAP maintained their activities all through Jinhua ham processing. LAP could display very strong actual activity during aging and post-aging, indicating that muscle LAP may play the most important role in generating free amino acids during the processing of Jinhua ham.     

FRESH AND PROCESSED QUALITIES OF COUNTRY-STYLE CURED HAMS FROM PUREBRED DUROC AND GENETICALLY UNDEFINED MARKET HOGS

The objective of this study was to determine country-style processing differences between hams from purebred Duroc market hogs and market hogs of unknown genetic makeup. Genetically undefined hams purchased from commercial suppliers were sampled the same day as hams from Duroc market hogs. Processing and curing followed standard commercial procedures. After curing, hams were weighed and sliced using a band saw. Slices from the approximate center of the ham were utilized to evaluate cured objective color, moisture content, pH, and salt content. There were no significant differences in cured ham yield between Duroc and genetically undefined market hogs. Intramuscular fat content was greater (P< 0.05) in hams from Duroc market hogs when compared to the hams from genetically undefined pigs. Subjective color, marbling and firmness scores were higher (P< 0.05) in hams from Duroc pigs. Objective color evaluation of cured, center-slices favored the hams from Duroc market hogs.     

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 and Texture Quality of Dry-Cured Ham as Affected by Endogenous Cathepsin B Activity and Muscle Composition

Hams were processed with standard cure adjuncts under two drying temperatures and analyzed after aging for 7 mo. Dried hams revealed that flavor and texture traits were affected by moisture and nonprotein nitrogen (NPN) content and that NPN was enhanced by greater cathepsin B activity, lower salt levels and higher temperature. Two major defects of dry-cured ham, mushy mouthfeel and surface white film, occurred in about 15% of samples. Most of these hams had abnormal NPN values and were shown to originate from meat with high enzyme activity and low protein content. We concluded that this type of meat is prone to uncontrolled proteolysis and related undesired traits, and to be a potential hazard in dry-cured hams cured with less salt.     

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.     

含KCl、氨基酸的低钠盐替代食盐对风干草鱼加工过程中理化特性的影响

本试验以新鲜草鱼为原料,食盐组为对照组,研究不同比例低钠盐替代食盐对风干草鱼加工过程中背侧肌和腹侧肌理化特性以及感官品质的影响。结果显示:干燥结束后,75%和100%低钠盐替代组的水分含量显著高于其他组(p<0.05),且背侧肌的水分含量和水分活度均显著高于腹侧肌(p<0.05)。低钠盐替代组的pH、色泽和质构与食盐组的变化趋势相似。75%低钠盐替代制备的产品咸味纯正,无异味,具有较高的接受度,且背侧肌和腹侧肌钠含量分别降低了31.88%和47.64%。低钠盐部分替代食盐制备的风干草鱼在保证理化和感官特性不受影响的基础上,极大地降低了钠含量,具有较好的应用前景。     

Salting, drying and sensory quality of dry-cured hams subjected to different pre-salting treatments: skin trimming and pressing

The effects of skinning in a V-shape and pressing of hams on salting, drying and sensory characteristics of dry-cured hams were assessed. Salt and water contents and a_w were determined in the central part of the ham during processing by computed tomography. Overall salt and water contents were also chemically analysed. Sensory analyses were performed on the final product. Partial skinning or pressing increased both salt uptake and final weight loss, but did not reduce the intra-batch variability in salt uptake. Moreover, trimmed hams exhibited a higher salt content in the inner areas of the hams after resting. Trimmed dry-cured hams showed less metallic flavour, higher saltiness and more mature flavour in the biceps femoris muscle, and lower pastiness and adhesiveness as well as higher crumbliness and aged flavour in both the biceps femoris and the semimembranosus muscles. Pressing treatment caused less metallic flavour only in biceps femoris muscle and higher saltiness.     

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.     

Physicochemical changes throughout the ripening of dry cured hams with different salt content and processing conditions

Physicochemical characteristics of Semimembranosus and Biceps femoris muscles from 24 dry cured Iberian hams were analysed. The hams were salted with different amounts of salt (60 g kg^–1, HS, and 30 g kg^–1, LS, w/w) and then ripened at different temperatures (traditional processing, T, versus modified processing, M). The processing conditions did not significantly affect the moisture content and the chloride molality of Semimembranosus and Biceps femoris muscles (p>0.05) throughout ripening, although daily weight losses were significantly affected (p<0.01). The effect of the processing conditions on water activity was also rather limited as it was only significant at the drying stage. Colour a* values and chroma were significantly higher in Semimembranosus muscles from T hams than from M ones (p<0.01). Muscles from hams elaborated in a traditional system showed a higher number of tyrosine crystals than muscles from hams processed in a modified one, though only to a significant extent in Semimembranosus muscle (p<0.05). The salt concentration was higher in HS than in LS hams. HS hams showed higher weight losses in the salting and postsalting stages, owing to a more intense osmotic dehydration.     

Time-related changes in intramuscular lipids of French dry-cured ham

The aim of this study was to investigate the changes in intramuscular lipids during the processing of French dry-cured hams. In the fresh biceps femoris muscle, the lipid content was on average, 105 mg/g DM with a large individual variation. Glycerides accounted for about 75% of total lipids. During processing for 273 days, phospholipid content decreased markedly whereas free fatty acid content rose from 1·9 mg/g DM to 9·4 mg/g DM. Little change affected the fatty acid composition of both glycerides and phospholipids during processing. After a decrease in the proportion of polyunsaturated fatty acids during the first 2 months, free fatty acid composition remained stable. The results suggest that lipid alteration during dry-curing of hams is due to lipolysis and that lipid oxidation is limited.     

Time-related changes in cathepsin B and L activities during processing of Jinhua ham as a function of pH, salt and temperature

Sixty experimental Jinhua hams were processed by traditional methods using green hams from local crossbred pigs of Lanxi, Zhejiang province, PR China. Biceps femoris was sampled from five hams randomly taken after each processing stage. Potential activities of cathepsin B and L were determined. The effects of temperature, salt content, pH value and nitrate content on the activities of cathepsin B and L were evaluated using response surface methodology (RSM) and the actual activities of cathepsin B and L during Jinhua ham processing were calculated. The results showed that potential activities of cathepsin B and L decreased gradually from 11332.05 to 9955.50 Ug(-1) prior salting to 1055.32-1359.90 Ug(-1) at the end of post-aging, respectively. After processing, about 9.31% original potential activity of cathepsin B and 13.66% original potential activity of cathepsin L were left. Temperature, pH value and salt content showed significant effects on cathepsin B and L activities. By stepwise regression analysis, two quadratic regression equation models were built individually for estimating cathepsin B and L activities. The models predicted that the actual activities of cathepsin B and L were less than 5% of their corresponding potential activities most of the time before half of loft-aging and about 15% and 20% during the rest processing periods. Nevertheless, cathepsin B and L retained actual activities throughout processing, especially during loft-aging and post-aging periods.