Dry-cured Processing Research Articles

Volatile compounds of Celta dry‐cured ‘lacón’ as affected by cross‐breeding with Duroc and Landrace genotypes

Dry-cured 'lacón' is a traditional cured meat product made in the north-west of Spain from the pigs' foreleg, with similar manufacturing process to that used in dry-cured ham. The aim of this study was to assess the influence of cross-breeding of Celta pig with Landrace or Duroc breeds on the formation of volatile compounds through the manufacture of 'lacón'. 'Lacón' from the crosses with Duroc presented lower final moisture (534 g kg(-1) ) and higher intra-muscular fat content [144 g kg(-1) dry matter (DM)] than 'lacón' from Celta pure breed (587 g kg(-1) and 36 g kg(-1) DM, respectively). Volatile compounds were extracted by solid-phase microextraction and analysed by gas chromatography-mass spectrometry. Volatile compounds from 'lacón' were affected by cross-breeding. The total amount of volatile compounds significantly (P < 0.001) increased during the manufacturing process, this increase being more marked in samples from the Landrace cross-breed. The most abundant group of flavour compounds at the end of the manufacturing process was esters in the three batches, followed by aldehydes, hydrocarbons and alcohols. The most abundant ester at the end of the process was hexanoic acid methyl ester, while the aldehyde found in a higher amount was hexanal. The profile of volatile compounds was affected by cross-breed, especially at the end of the 'lacón' dry-curing process.

Peptides naturally generated from ubiquitin-60S ribosomal protein as potential biomarkers of dry-cured ham processing time

Proteolysis is a complex and dynamic process which takes place throughout the whole dry-cured processing due to the action of endogenous muscle peptidases, and results in the generation of a high number of small peptides and free amino acids responsible for the final quality of dry-cured ham. In this study, a total of sixty-eight peptides derived from the ubiquitin-60S ribosomal protein have been identified in dry-cured ham at 2, 3.5, 5, 6.5, and 9 months of processing using various chromatographic separations and a quadrupole/time-of-flight mass spectrometer in tandem. Some of the identified peptides have been detected during the whole process, whereas a total of fourteen of them were exclusively identified at 9 months of curing. The presence of any of these peptides could be a good indicative that dry-cured ham pieces have reached a minimum curing process of 9 months. The study of the generated peptides has contributed both to a better knowledge of proteolysis evolution and the endogenous enzymes participating, and to determine their potential to be used as quality markers to monitor the processing time.

Chemical changes in volatile aldehydes and ketones from subcutaneous fat during ripening of Iberian dry-cured ham. Prediction of the curing time

Changes in volatile aldehyde and ketone amounts from subcutaneous fat have been evaluated during the dry-curing process (987days) of Iberian ham by purge & trap-gas chromatography–mass spectroscopy method, using the same hams for the first time. The subcutaneous adipose tissues of ten hams obtained from five Iberian pigs fed on acorns and pasture were sampled and analyzed periodically during whole processing time. Fifteen aldehydes and six ketones have been identified, all previously described except the 2,4-pentadienal that has been identified for the first time. A LDA was applied and the two discriminant functions were obtained using backward stepwise analysis retaining the variables: 4-octen-3-one, 2-methyl-butanal, butanal, 2-decenal, 2-heptanone, decanal, 2,4-pentadienal, pentanal, hexanal, 2-butanone, octanal and 2-octanone. A complete separation between the three periods was obtained, indicating that the retained variables are powerful descriptors to characterize samples from these three dry-curing periods. The ratio between total aldehydes and ketones was used to predict the curing time.

The changes in gliceridic fractions of sweaty fat and weight loss during ripening time of Iberian dry-cured ham

In this contribution, we studied the weight loss of Iberian hams during dry-curing process and determined the composition of fatty acids, triacylglycerols, diacylglycerols (DGs), monoacylglycerols and free fatty acids in their sweaty fat collected during processing. Ten Iberian hams were used in the study and kept throughout all processes. Humidity, temperature and weight were measured and the sweaty fat of each ham was collected. During dry-curing process, Iberian hams underwent a weight loss with a logarithmic trend and the coefficients depended on the characteristics of the initial raw material and processing conditions. The percentage of weight that hams lost in dry-curing process ranges between 28.83 and 35.91% (mean 33.06%), whereas they lost between the 0.29 and 1.28% (mean 0.79%) of sweaty fat. Concerning the composition of sweaty fat, this was influenced by the composition of ham fat and by the different melting points of compounds sweated. The monounsaturated fatty acids were the most abundant in sweaty fat, especially C18:1 ω9, followed by the saturated and polyunsaturated fatty acids. Triacylglycerols represented 13.4–24.6% of the sweaty fat, characterized by a high amount of species with doubled bound number 2, especially POO. The free fatty acid species found were C18:1 and C16:0 and their percentage ranged similar in all periods, being between 14.45 and 26.94%. The only specie of monoacylglycerol detected was 1-monoolein, being present between 1.24 and 10.65%. The diacylglycerols (DGs) most abundant were 1,2-OP and 1,2-OO (O=oleic acid, P=palmitic acid). In the first period of sweating, there was a higher amount of 1,2-DGs, whereas similar amounts of 1,2- and 1,3-DG species were found in the second and third periods of sweating. When there was a higher amount of diacylglycerols, there were higher quantities of monoacylglycerols and free fatty acids in this fat.

Synergistic Interaction of Polypropylene Fibres in Latex Modified High Strength Concrete

Abstract Synthetic polymer latexes, such as styrene-butadiene rubber (SBR) latex addition in Portland cement has gained wider acceptance in many applications in the construction industry. Polymer-modified cementitious systems seals the pores and micro cracks developed during hardening of the cement matrix, by dispersing a film of polymer phase throughout the concrete. A comprehensive set of experimental test were conducted for studying the compressive properties of SBR latex polymer with crimped polypropylene fibres at relative volume fractions of 0.1 and 0.3%. The results indicated that the addition of polypropylene fibre has little effect on the reduction in the workability of concrete composite containing fly ash and SBR Latex. Increase in polypropylene fibres upto 0.3% Vf showed increase in compressive strength upto 57.5MPa. The SBR concrete without fibre showed an increase in strength upto 20 % compared to plain concrete. Test results also indicated that the compressive strength was increased in SBR fibre concrete by means of an ordinary dry curing process than wet curing because of their excellent water retention due to polymer film formation around the cement grains. On the contrary the compressive strength reduces for SBR fibre concretes under wet curing compared to dry curing

Changes in polar and non-polar lipid fractions of subcutaneous fat from Iberian ham during dry-curing process. Prediction of the curing time

The aim of this study was to investigate the changes in polar and non-polar lipid fractions from subcutaneous adipose tissue during the ripening of Iberian dry-cured hams. Total fatty acid, triacylglycerol and phospholipid amounts decreased with processing whereas diacylglycerol, monoacylglycerol and free fatty acid amounts grew up. Phospholipids were only detected during postsalting period, decreasing markedly with an exponential trend. In this kind of fat, the free fatty acids do not come mostly from phospholipid hydrolysis as occurs in intramuscular fat. Drying period is characterized by an intense lipolysis of triacylglycerols and diacylglycerols. The hydrolysis would be more influenced by enzymes and microorganism action in the two first periods while cellar would be characterized by chemical hydrolysis of acylglycerols, oxidation of these and fatty acids and sweat of fat. Pattern recognition techniques combined with mathematical analysis of fatty acids and diacylglycerols have been used in order to predict the curing time.

Effect of tiger nut fibre addition on the quality and safety of a dry-cured pork sausage (“Chorizo”) during the dry-curing process

There is a growing interest in the revalorization of co-products from the food industry. Co-products from tiger nuts (Cyperus esculentus) milk production are a suitable fibre source. “Chorizo” is the most popular dry-cured meat product in Spain. The aim of this work was to study the effect of the tiger nut fibre addition (0, 5, and 7.5%) on the quality (composition, physicochemical, and sensorial properties) and safety (oxidation and microbial quality) of a Spanish dry-cured sausage, during the 28days of its dry-curing process. Tiger nut fibre (TNF) addition decreased fat and increased moisture content. The addition of TNF significantly increased (p<0.05) the total dietary fibre content of “Chorizo”. Lightness (L*), yellowness (b*) and redness index (a*/b*) were significantly (p<0.05) affected by the fibre content. The addition of 5% and 7.5% TNF to chorizo provided rich fibre and a healthier product. Although there were slight changes in the physicochemical properties, its quality (traditional characteristics) and its safety remained.

Lipolysis, proteolysis and physico-chemical modifications during ripening of dry-cured duck breast

Chemical traits related to dry-curing process (pH, moisture, water activity total and chlorides), color and textural properties and changes of free fatty acid and amino acid compositions during the processing of dry-cured duck breast were quantified. For this purpose, 25 male ducks from crossbred mule were used in this study and samples at 0 days (raw breast) and after 7, 14, 21 and 28 days of ripening were taken. The results showed that all physico-chemical parameters suffered significant differences during the manufacture of dry-cured duck breast. A decrease in all variables was observed with the exception of chlorides and textural properties due to dehydration process. Concerning free fatty acids, a significant increase (P < 0.05) from 299.57 mg/g of fat in the raw breast to 380.43 mg/g of fat at the end of the drying–ripening stage was recorded. Finally, a significant increase (P < 0.001) in the total free amino acids was observed from raw breast (1,059.17 mg/100 g of DM) to the end of dry-ripening (2,792.48 mg/100 g of DM).

Identification of novel antioxidant peptides generated in Spanish dry-cured ham

The objective of this study was to purify and identify antioxidant peptides present in a water soluble extract of Spanish dry-cured ham. The initial extract was loaded into a Sephadex G25 column and fractions showing antioxidant activity were collected, pooled together and subjected to reversed-phase chromatography for further purification. Using a nano-LC–MS/MS analysis, 27 peptides were identified in these fractions. Several key peptides were selected for synthesis and the determination of their antioxidant properties using the DPPH radical-scavenging assay and reducing power analysis. The strongest radical-scavenging activity was observed with peptide SAGNPN which showed 50% antioxidant activity at a concentration of 1.5mg/ml. On the other hand, the peptide GLAGA showed the higher reducing power with 0.5units of absorbance at 700nm at a concentration of 1mg/ml. Other synthesised sequences showed lower antioxidant activity. The results indicate the potential of Spanish dry-cured ham as a source of antioxidant peptides naturally generated during the dry-curing process.

Fat effect on physico-chemical, microbial and textural changes through the manufactured of dry-cured foal sausage Lipolysis, proteolysis and sensory properties

The effect of fat content on chemical traits related to dry-curing process (pH, moisture and water activity), color and textural properties and changes of free fatty acids and amino acids compositions during the processing of foal dry-cured sausages were studied. For this purpose, three batches (20 units per batch) of dry fermented sausages with different pork back fat content (5%, 10% and 20%) were manufactured; low fat (LF), medium fat (MF) and high fat (HF), respectively. Samples at 0days (mix before stuffing), and after 7, 14, 28, 42 and 49days of ripening were taken.The fat level affected color and textural parameters at the end of the process, showing dry-cured foal sausage with the higher level of fat, the highest values of luminosity and the least hardness. No significant differences (P>0.05) among batches were detected on total viable counts, lactic acid bacteria and Microccaceae during the process. Regarding lipolysis and lipid oxidation it can be deduced that the increase in the fat level encouraged the production of free fatty acids and 2-thiobarbituric acid reactive substances. At the end of the ripening individual free fatty acids followed this order: oleic, palmitic, linoleic and stearic acid, representing 82–95% of the total free fatty acids. Final level of TBARS index was in the worst case of 1.23mg MDA/kg of sausage. On the contrary, the batch with lesser fat content showed the highest levels of free amino acids at the beginning and at the end of the process, showing final values of 1.6%.

Combined use of a probiotic culture and citrus fiber in a traditional sausage ‘Longaniza de Pascua’

Combined use of Lactobacillus casei CECT 475 and orange fiber for the production of Spanish non-fermented dry-cured sausage (Longaniza de Pascua) was studied. Quality and safety characteristics of four “Longaniza de Pascua” types (control, 1% fiber, L. casei and 1% fiber + L. casei) were evaluated during 8 days of dry-curing. At the end of the dry-curing process pH of all types of sausages was higher than pH 5.3 and water activity was below Aw 0.91. The incorporation of 1% orange fiber favored the growth of lactic acid bacteria. The addition of orange fiber and L. casei CECT 475 accelerated the decline in pH and the release of organic acids and glycerol. Sausages containing both orange fiber and L. casei CECT 475 obtained the best sensory scores and provided the best guarantees of food safety, low pH and water activity, decreased counts of Enterobacteria and reduced residual nitrite compared to the other type of sausages.

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.

Biochemical and sensory changes in dry-cured ham salted with partial replacements of NaCl by other chloride salts

The reduction of the content of sodium chloride in dry-cured ham was studied in to prevent the problems related to high sodium intake (i.e. the hypertension). One of the possibilities to reduce the sodium content is the partial replacement of sodium chloride by mixtures of potassium, magnesium and calcium chloride salts. The effect of two salting formulations (formulation II: 50% NaCl–50% KCl and formulation III: 55% NaCl, 25% KCl, 15 CaCl 2 and 5 MgCl 2) on the protease activity through the dry-curing process and on the sensory characteristics of the final product was evaluated and compared to those of control hams (formulation I, 100% NaCl). Sensory attributes were all affected in the hams containing CaCl 2 and MgCl 2 while hams containing 50% KCl and NaCl (formulation II) were better valued, except for the attribute taste probably due to the potassium contribution to bitter taste.

Possible biological markers of the time of processing of dry-cured ham

Several muscle compounds (creatine, creatinine, hypoxanthine, inosine, inosine 5′ monophosphate, xanthine, adenosine monophosphate, guanosine, and uridine) were studied as possible biological markers of a minimum dry-cured ham processing time. A correlation between the concentration of the compounds and the time of processing was found. The ratios for some of them were calculated to study their behaviour during processing. The Hx/Ino ratio substantially increased up to 5months of curing and then remained constant (p<0.05). The Hx/Ino ratio might be considered as a potential biomarker of the minimum time of dry-cured processing (5months). The Cn/Cr ratio increased during drying up to 9months of ripening (p<0.05). However, although Cn/Cr ratios remained constant after 9months of processing, variations between hams were observed due to the differences existing in the raw meats and small differences in processing conditions, making it difficult to consider Cn/Cr ratios as biomarkers of ripening time.

Intense Degradation of Myosin Light Chain Isoforms in Spanish Dry-Cured Ham

One of the main biochemical changes that take place during the processing of dry-cured ham is the degradation of the muscle protein fraction, mainly due to the action of muscle enzymes. In the present study, the isolation and tentative identification of 137 fragments from myosin light chain 1 (MLC 1), together with 88 fragments originated from myosin light chain 2 (MLC 2), have been achieved for the first time in Spanish dry-cured ham, proving the intense proteolysis experienced by myofibrillar proteins after dry-cured processing. This study was carried out by use of proteomic technology for peptide identification, and the possible enzymes contributing to the degradation of these proteins were also further discussed.

Photocatalytic self-cleaning textiles based on nanocrystalline titanium dioxide

The anatase TiO2 in this study was prepared in an aqueous solution through a sol-gel process with a small amount of acid, which prevented the loss of the mechanical strength of the cotton fabrics when compared with previous methods. The application of the anatase TiO2 to textiles, which formed a transparent, thin film of nanocrystalline TiO2 on the fiber surface, was done via a simple dip-pad—dry-cure process. The adhesion between the TiO 2 thin film and the cotton substrates was high, indicated by good fastness at 20 home launderings. The bending rigidity was increased by 13% and the air permeability was reduced by 0.76% after TiO2 treatment, which indicated that the treatment did not significantly influence the fabric handling and the air permeability. The mechanical strengths of the treated cotton fabrics investigated indicated that the photocatalytic decomposition of the cellulosic chains of the cotton fibers is very limited after 20 h of irradiation.

Carboxymethyl chitosan coating to block photocatalytic activity of TiO2 nanoparticles

In order to lower photocatalytic degradation of TiO2 on skin and textiles, carboxymethyl chitosan (CMCH) was used to coat TiO2 nanoparticles. The polymer (CMCH) not only acted as the blocking agent of photocatalytic activity, but also dispersed TiO2 nanoparticles better to prohibit them from congregation by anchoring them. The structure of as-prepared nanocomposites was characterized by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The TiO2/CMCH nanocomposites were coated onto cotton fabrics by a dip-pad—drycure process. The treated cotton fabrics demonstrated lower photocatalytic activity in comparison to cotton fabrics treated by pure TiO2 in a typical photocatalytic test. The treated cotton showed a combination of bactericidal activity of TiO2 and CMCH, and excellent protection against UV radiation.

Identification of small troponin T peptides generated in dry-cured ham

Troponin T (TnT) is a myofibrillar protein present in striated muscle that develops important structural and regulatory functions. This protein is easily degraded during post-mortem ageing but details of the TnT hydrolysis occurring during much longer processes, e.g. the dry-cured processing, as well as the specific sequences of the generated fragments, still remain undetermined. In the present study, the isolation and identification of 27 peptides, generated from TnT during dry-cured processing, are reported for the first time. This study has been developed using matrix-assisted laser desorption/ionisation time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF) and it evidences the extensive degradation of TnT occurring during the processing of dry-cured ham. Some of the cleavage sites, corresponding to these sequenced fragments, confirm the sites reported by other authors both in vitro and during post-mortem ageing of meat.

A note on the relationships between cured-cooked and dry-cured ham processing yields

Right and left hams from 353 pigs slaughtered at around 100 kg body weight were processed into cured-cooked hams and dry-cured hams, respectively. Weights and yields at various stages of each process, carcass lean content and fresh meat quality traits were registered. Technological yield of cured-cooked processing (saleable cooked ham weight/defatted-deboned fresh ham weight) was more closely correlated to ultimate pH (r=0.51, p<0.001) than to carcass leanness (r=-0.13, p<0.05) whereas the reverse situation -r=0.15 (p<0.01) and r=-0.62 (p<0.001), respectively--was found for technological yield of dry-cured processing (saleable dry ham weight/trimmed fresh ham weight). The correlation between the two technological yields was significantly positive but of fairly moderate magnitude (r=0.36). The correlation between the overall yields (saleable processed ham weight/entire fresh ham weight) of the two processes revealed to be very close to zero (r=-0.01).

Creatine and creatinine evolution during the processing of dry-cured ham

Dry-curing of ham involves many biochemical reactions that depend on the processing conditions. The aim of this study was to evaluate the effect of the dry-cured processing on the concentration of creatine, creatinine and the creatinine/creatine ratio. Dry-cured hams under study were salted using three different salt mixtures (100% NaCl; NaCl and KCl at 50% each; and 55% NaCl, 25% KCl, 15% CaCl(2) and 5% MgCl(2)) in order to observe its influence on creatinine formation but no significant differences were found between them at any time of processing. However, significant differences between different post-salting times (20, 50 and 80 days) and the ripened hams (7, 9 and 11 months of ripening) were observed. Results showed that creatine and creatinine remain stable once the ripening period is reached. These results were confirmed when analysing dry-cured ham samples submitted to extreme conditions of temperature and time (20, 30, 40 and 70 degrees C during 0, 20, 40 and 60 min) as well as commercial dry-cured hams with more than 12 months of processing.