Effects of Processing Temperature on Color Properties of Dry-Cured Hams Made without Nitrite.

Dry cured hams were investigated for their ability to develop red color even at low temperature (3-4 °C) and in the absence of added nitrites; results were compared with those obtained from nitrite-free hams made at conventional warm maturing temperatures. Colorimetric parameters (L*, a*, b*, and hue) and concentration of the main pigments Zn protoporphyrin IX (ZnPP) and heme were measured at three stages of preparation (six, nine, and 12 months), showing that red color was successfully formed at low temperatures, though at a slower rate and less intensively than under warm conditions. Major differences in the pattern of color development were found with the two processing temperatures. While the typical features of an enzyme-dependent mechanism, with a progressive drop in enzyme activity paralleling the synthesis of Zn protoporphyrin IX, were observed at warm temperatures, the same did not occur in cold-made hams, where the enzyme activity was almost unchanged throughout the process. These results, along with data from a descriptive sensory analysis, are supportive of a non-enzymatic mechanism leading to ZnPP (hence the red color) under cold conditions, with an estimated three-month delay compared with nitrite-free hams manufactured in a warm maturing regimen.

Effect of added autochthonous yeasts on the volatile compounds of dry-cured hams.

Three yeast strains belonging to Debaryomyces and Hyphopichia spp., isolated from dry-cured hams and previously tested for biocontrol activity against toxigenic Penicillium nordicum, were investigated for ability in colonising ham surface. Hams were twice yeast-inoculated onto the unskinned muscle surface during ripening and processed up to full maturation in two manufacturing plants. The yeast strains and the manufacturing plants differed (P < 0.05) in surface populations, volatile compounds and sensory descriptors of matured hams. Sensory scores for each of the yeast-inoculated groups were higher or similar to the non-inoculated ones (controls). Debaryomyces strains were regarded as those most fit to colonise the ham surface under the ecological conditions of dry-curing rooms, hence to qualify as biocontrol agents against the growth of undesired mould and preserve the typical sensory properties of dry-cured hams.

Biocontrol of Penicillium nordicum growth and ochratoxin A production by native yeasts of dry cured ham.

Twelve yeast strains isolated from the surface of Italian typical dry-cured hams, belonging to D. hansenii, D. maramus, C. famata, C. zeylanoides and H. burtonii species, and previously selected for their ability to grow in dry-cured ham-like substrates, were screened for antagonistic activity against a toxigenic strain of P. nordicum and inhibition of ochratoxin A (OTA) biosynthesis. On average, yeast inhibitory activity was lowered by increasing fungal inoculum and enhanced by NaCl presence. In the assay conditions, H. burtonii and C. zeylanoides were the most effective, both in inhibiting P. nordicum growth and OTA production. D. hansenii was the species with the lowest inhibitory activity, especially in the absence of salt. OTA production dropped from the range < LOD - 5000 ppb in P. nordicum control plates to the range < LOD - 200 ppb in yeast-added plates. OTA production increased in the presence of NaCl in P. nordicum control plates, while salt enhanced inhibition against OTA production in yeast-added plates.

Sensory and texture properties of Italian typical dry-cured hams as related to maturation time and salt content.

Maturing time and salt were fixed factors and fat was a covariate in a full factorial design study of sensory and texture properties of 36 dry cured hams. Samples were chosen to fit three ageing and salt classes. Differences (P < 0.05) in sensory scores were found between whole slices (with cover fat) and their biceps femoris (BF) counterparts, with sweet taste enhanced in whole samples and conversely unpleasant bitter taste more intense in BF portions. Increased ageing time resulted in better sensory profiles, as documented by greater scores (P < 0.05) for matured odour, matured taste and sweet taste, whereas salty taste was reduced. Decreased salt was associated with greater intensities (P < 0.05) of undesired green odour and taste. Based on chemical composition, the ham consistence appears improved by long-term dehydration, provided that protein breakdown is under control. It is concluded that for salt reduction of up to 25% to be achieved without negative side effects, extended ageing and restrained proteolysis are key factors.

Color formation in nitrite-free dried hams as related to Zn-protoporphyrin IX and Zn-chelatase activity.

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.

Determination of ochratoxin A in dry-cured meat products by a HPLC-FLD quantitative method.

A fast and sensitive method for the quantification of the mycotoxin ochratoxin A (OTA) in dry-cured meat products has been developed, which does not require a clean-up step, by HPLC with an alkaline mobile phase (pH 9.8). Validation procedures for specificity, trueness, ruggedness, stability, recovery and repeatability were performed. The decision limit (CC alpha) and the decision capability (CC beta) were calculated at 1.10 and 1.23 microg/kg, respectively. The procedure was applied to representative dehydration levels of dry-cured meat samples.

Penicillium populations in dry-cured ham manufacturing plants.

Seven ham manufacturing plants were sampled for 1 year to assess the mycoflora present in the air and on hams, with special attention given to potential mycotoxin producers. Temperature and relative humidity were recorded in the ripening rooms. Maturing rooms held hams from 2 to 3 through 6 to 7 ripening months, and aging rooms held hams for the following 6 to 7 months, until the 14-month ripening point, when they were ready for the market. Mean temperatures and relative humidities registered during the study were 14.9 degrees C and 62.4%, respectively, in maturing rooms and 16.3 degrees C and 57.6% in aging rooms. Aspergilli and penicillia, potential mycotoxin producers, were isolated in all the plants from the air and the ham. Aspergilli represented 5% of the isolates, while penicillia were largely dominant, with Penicillium nalgiovense being the most represented species (around 60% of the penicillia), followed by Penicillium nordicum, with 10 and 26% of the penicillia isolated, respectively, from the air or the ham. Ochratoxin A production ability, checked in vitro at 250C, was observed in 50% of the P. nordicum isolates obtained both from the air and the ham. Air and ham surface contamination by penicillia was greater in the ripening rooms, where higher temperatures were registered. A certain correlation was also observed between air and ham surface contamination. On the basis of this study, P. nordicum, the ochratoxin A producer that is notable on proteinaceous substrates, is normally present in ham manufacturing plants in Italy, even though not a dominant species. Further studies are necessary to clarify and ensure if dry-curing conditions minimize the potential risk of ochratoxin A formation in the product.