Juan J. Córdoba

Volatile components of dry cured Iberian ham

Abstract A study was conducted to identify the volatile compounds in aged Iberian hams, processed in the traditional way. The volatiles from aged hams were entrained in cold traps after distillation under high vacuum. The distillate was collected with dichloromethane and analysed by gas-chromatography-mass-spectrometry (GC-MS). Seventy-seven compounds were tentatively identified in the volatile fraction. Alkanes (12), branched alkanes (14), aldehydes (13), and aliphatic alcohols (9) dominated the volatiles. Small amounts of lactones (5), esters (9) and ketones (7) and other miscellaneous compounds were also present. The possible origins of these compounds and their relationship with the characteristic flavour of this product are discussed.

Lipid oxidative changes in the processing of Iberian pig hams

Attempts to identify the compounds responsible for the particular flavour of Iberian pig ham indicate that many derive from lipid oxidation. In the present work, the evolution of the degree of acidity, the peroxide value and the content of certain aldehydes was followed to assess the extent of the lipid oxidation in the Biceps femoris and Semimembranosus muscles of Iberian pig hams. Lipolysis occurs continuously throughout the process, being especially intense immediately after salting and during drying. The peroxide value was higher after salting and in the first stage in the cellar. Aldehyde content rose continuously in the first stages, but the sharpest rise took place before drying. Saturated aldehydes were more abundant than unsaturated. During the last stage, autoxidation seems to be considerably reduced.

Composition and toxigenic potential of the mould population on dry-cured Iberian ham

The fungal population on dry-cured Iberian ham can be essential to the development of the products unique characteristics, but health hazards due to mycotoxins may be significant. We examined the natural fungal population of Iberian hams during ripening at three different locations. Chloroform extracts from 59 selected isolates were tested for toxicity to brine shrimp larvae and VERO cells, for mutagenicity in the Ames test and for antimicrobial activity against Staphylococcus aureus. The diversity of moulds increased during ripening. Penicillium commune, Penicillium chrysogenum, Penicillium aurantiogriseum, Penicillium expansum and Penicillium echinulatum dominated most of the ripening time; however, the Eurotium species, particularly E. herbariorum and E. repens, increased in the final product. Using the above tests, most moulds were toxigenic. The toxigenic potential of the fungal population increased as the processing progressed. To minimize health hazards from uncontrolled fungal populations, we identified non toxigenic strains of Penicillium chrysogenum that could be used as starters in dry-cured hams.

Effects of salt and temperature on proteolysis during ripening of Iberian ham

Fifty-five hams from Iberian pigs were processed using two different dry-curing techniques, traditional and modern. Salt content, non-protein nitrogen and its fractions (peptide, amino acid and volatile basic nitrogen) from Biceps femoris muscles were quantified. The existence of an overlapping effect of both temperature and salt content on the general non-protein nitrogen production was observed. The most intense proteolytic breakdown took place when higher temperatures were reached during the drying stage. The difference in salt concentration seems to contribute to generating different quantities in the non-protein nitrogen fractions. The inclusion at the end of the cellar stage of a stuffing period would permit increasing the accumulation of free amino acid in high salted hams.

Evaluation of proteolytic activity of micro-organisms isolated from dry cured ham

In order to determine the possible contribution of micro‐organisms to the ripening of meat products, 48 cocci, 18 moulds and 20 yeasts isolated from dry‐cured Iberian ham were evaluated for proteolytic activity. Two specific methods were used: the ability to hydrolyse myosin in broth and, for those strains showing high activities, hydrolysis on both myofibrillar and sarcoplasmic proteins on pork slices. Moulds and cocci showed the highest proteolytic activity for myosin in broth. Both myofibrillar and sarcoplasmic proteins were recovered at lower rates from inoculated than from sterile incubated pork. The deepest changes in myofibrillar and sarcoplasmic proteins were originated by one strain each of Penicillium chrysogenum and Staphylococcus xylosus, respectively. Only small changes were observed in the concentrations of free amino acids from inoculated pork slices, except for the samples with P. chrysogenum, where there were increases in all free amino acids. Thus, P. chrysogenum makes a significant contribution to proteolysis during the ripening of dry‐cured meat products.

Characterization of Staphylococcus spp. and Micrococcus spp. isolated from Iberian ham throughout the ripening process

The Iberian dry cured ham is an uncooked meat product highly appreciated because of its characteristic flavour. This product is obtained from highly marbled Iberian pig hindlegs after 18-24 months of maturation under natural environmental conditions. The role of Micrococcaceae in the development of the aroma characteristics of this products remains unclear. Identification of Gram-positive, catalase-positive cocci isolated from Mannitol Salt Agar plates showed that Staphylococcus xylosus followed by Staphylococcus equorum are the predominant organisms, even after 16 months of maturing. A remarkable variety of types of both staphylococci and micrococci are detected at any sampling time. The metabolic activities of these organisms could contribute to the characteristics of the final product.

Changes in intramuscular lipids during ripening of Iberian dry-cured ham

Thirty-one thighs were obtained from Iberian pigs fattened with acorns and were processed during 22 months in the traditional dry-curing process. Lipolysis affecting intramuscular fat during the processing of Iberian dry-cured ham has been analyzed by studying the changes of glycerides, phospholipids and free fatty acids in lipids from Biceps femoris muscle. Little change affected the fatty acid composition of glycerides during processing. A double-phased increase in the acidity values and a decrease in the quantity of fatty acids of phospholipids during the processing were observed. There seems to be a relationship between the extension of the lipolysis taking place during the maturing and the processing conditions and raw material used.

Hydrolysis and loss of extractability of proteins during ripening of iberian ham.

To elucidate the extent of the hydrolysis and loss of extractability of protein during the traditional ripening of Iberian ham, the evolution during processing of non-protein nitrogen (NPN) and protein fractions soluble in 0·03 m pH 7·1 phosphate and 1·1 KI + 0·1 m phosphate pH 7·4 buffers and 6 m urea was followed from Semimembranosus and Biceps femoris muscles. The NPN steadily increased during processing, showing maximum intensity at salting and drying. Electrophoretic study of the proteins extracted, and microscopical examination of the pellet obtained after consecutive extractions with the above buffers, revealed that hydrolysis and insolubilization are more intense in myofibrillar than in sarcoplasmic proteins. Protein aggregation involves mainly the myofibrillar fraction, and occurs during the first stage of processing.

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.

Production of Cyclopiazonic Acid by Penicillium commune Isolated from Dry-Cured Ham on a Meat Extract–Based Substrate

Penicillium commune, a mold frequently found on dry-cured meat products, is able to synthesize the mycotoxin cyclopiazonic acid (CPA). To evaluate the hazard due to CPA on such foods, the ability of P. commune to grow and produce CPA at water activities (a(w)) in the range of 0.99 to 0.90 with a meat extract-based medium from 12 to 30 degrees C was determined. CPA was quantified by high-pressure liquid chromatography and mass spectrometry. P. commune was able to grow at every a(w) and temperature tested. The optimal environmental conditions for growth were 20 to 25 degrees C, at 0.97 to 0.96 a(w), but the highest amount of CPA was produced at 30 degrees C, 0.96 a(w). No direct correlation between growth rate and CPA production was assessed. Temperature seems to be the most important factor influencing CPA production. However, there was an interaction between temperature and a(w) that significantly (P < 0.001) affected growth and CPA production. An a(w) of 0.90 had a marked effect, depressing growth and CPA production. Meat extract-based medium proved to be an appropriate substrate for CPA biosynthesis by P. commune under a wide range of conditions.