Enrico Novelli

Oxidation in traditional mediterranean meat products

Lipid oxidation in dry-fermented sausages and dry-salted-hams, representative items of traditional Mediterranean pork products, is responsible for the production of compounds which can affect their organoleptic qualities and wholesomeness. Lipid-derived compounds make up an important share of the volatiles extracted from matured products, once the contribution of spices is removed, and contribute significantly to the flavour of old style products. The few reports available on oxysterols depict a total cholesterol oxidation rate of about 0.1%, a threshold level for toxic effects to occurin vitro but about 100 times lower of thein vivo toxicity dose. The value could perhaps be reduced with the use of antioxidants. Phospholipids are the main class of fats interested by lipolysis and unsaturated fatty acids are those most interested by oxidation. On that basis, the case of special feeding regimes, such as that of Iberian pigs, and the possible relevance of muscle fibre type on flavour development are discussed.

Lipid and cholesterol oxidation in frozen stored pork, salame Milano and mortadella.

An investigation has been carried out on oxidative processes of fresh and stored frozen pork and of two pork products (salame Milano and mortadella). Wholesale pork cuts (shoulder, ham trimmings, belly and backfat) were checked fresh and after frozen storage (1, 3 and 6 months). The streaky bacon was studied fresh and after scalding at 80 °C. Salame Milano and mortadella were produced with fresh and frozen raw materials and a few commercial samples were also part of the study. No real differences have been observed between commercial and experimentally produced salame and mortadella. Peroxide and TBARS values were low in all cases. Among the cholesterol oxides determined (7β-hydroxycholesterol, 5,6α-epoxycholesterol, 7-ketocholesterol and 25-hydroxycholesterol) those dangerous for human health were either absent or their concentration was below toxic levels. The results are discussed on the light of literature reports and Italian pork products technologies.

Determination of Microbial Diversity of Aeromonas Strains on the Basis of Multilocus Sequence Typing, Phenotype, and Presence of Putative Virulence Genes

ABSTRACT The genus Aeromonas has been described as comprising several species associated with the aquatic environment, which represents their principal reservoir. Aeromonas spp. are commonly isolated from diseased and healthy fish, but the involvement of such bacteria in human infection and gastroenteritis has frequently been reported. The primary challenge in establishing an unequivocal link between the Aeromonas genus and pathogenesis in humans is the extremely complicated taxonomy. With the aim of clarifying taxonomic relationships among the strains and phenotypes, a multilocus sequencing approach was developed and applied to characterize 23 type and reference strains of Aeromonas spp. and a collection of 77 field strains isolated from fish, crustaceans, and mollusks. All strains were also screened for putative determinants of virulence by PCR (ast, ahh1, act, asa1, eno, ascV, and aexT) and the production of acylated homoserine lactones (AHLs). In addition, the phenotypic fingerprinting obtained from 29 biochemical tests was submitted to the nonparametric combination (NPC) test methodology to define the statistical differences among the identified genetic clusters. Multilocus sequence typing (MLST) achieved precise strain genotyping, and the phylogenetic analysis of concatenated sequences delineated the relationship among the taxa belonging to the genus Aeromonas, providing a powerful tool for outbreak traceability, host range diffusion, and ecological studies. The NPC test showed the feasibility of phenotypic differentiation among the majority of the MLST clusters by using a selection of tests or the entire biochemical fingerprinting. A Web-based MLST sequence database (http://pubmlst.org/aeromonas) specific for the Aeromonas genus was developed and implemented with all the results.

Comparison of culture-dependent and -independent methods for bacterial community monitoring during Montasio cheese manufacturing

The microbial community in milk is of great importance in the manufacture of traditional cheeses produced using raw milk and natural cultures. During milk curdling and cheese ripening, complex interactions occur in the microbial community, and accurate identification of the microorganisms involved provides essential information for understanding their role in these processes and in flavor production. Recent improvements in molecular biological methods have led to their application to food matrices, and thereby opened new perspectives for the study of microbial communities in fermented foods. In this study, a description of microbial community composition during the manufacture and ripening of Montasio cheese was provided. A combined approach using culture-dependent and -independent methods was applied. Culture-dependent identification was compared with 16S clone libraries sequencing data obtained from both DNA and reverse-transcribed RNA (cDNA) amplification and real-time quantitative PCR (qPCR) assays developed to detect and quantify specific bacterial species/genera (Streptococcus thermophilus, Lactobacillus casei, Pediococcus pentosaceus, Enterococcus spp., Pseudomonas spp.). S. thermophilus was the predominant LAB species throughout the entire ripening period of Montasio cheese. The culture-independent method demonstrates the relevant presence of Pseudomonas spp. and Lactococcus piscium at the beginning of ripening. The culture-dependent approach and the two culture-independent approaches produced complementary information, together generating a general view of cheese microbial ecology.

Oxidative stability of lipids and cholesterol in salame Milano, coppa and Parma ham: dietary supplementation with vitamin E and oleic acid

An investigation has been carried out on the effect of dietary supplementation with vitamin E and oleic acid on oxidative stability of Italian representative pork products. Fatty acid composition of deposited fat was modified in the oil supplemented groups with negative effects on fat firmness. Oil supplementation significantly increased vitamin E content of muscles, as well. Oxidative stability of fat, evaluated by TBARS and cholesterol oxides, has not shown significant differences between dietary treatments but, although the differences were not significant, the tendency was sufficiently clear, especially in salame Milano, towards a lower oxidation level in vitamin E enriched meat. Cholesterol oxidation was found to vary in general around 0.1% of total cholesterol and the only cholesterol oxides observed were 7β-hydroxycholesterol, 5,6α-epoxycholesterol and 7-ketocholesterol. Aldehydes content and distribution appeared to be linked, firstly, to the specific processing technology of the product and, secondly, to the changed fatty acid composition.

Comparative evaluation of some antioxidants in salame Milano and mortadella production.

Six formulations of salame Milano and mortadella were produced, one without antioxidants, two with sodium ascorbate (0.05-0.1 and O.2%), one with catechin, one with phytic acid, and one with sesamol. The products were studied for oxidation levels (peroxide value, TBARS, cholesterol oxides) and colour stability. The evaluation of the latter took place in conditions simulating commercial types of packaging (vacuum and modified atmosphere) and display. A significant difference emerged in colour stability. With the exception of salame Milano packed under modified atmosphere, in all cases salame and mortadella produced without Na ascorbate had significantly lower colour stability. Both in salame and mortadella, peroxide values and TBARS determination gave indications of a possible pro-oxidant effect of ascorbate 0.2% compared with an effective antioxidant activity of the other compounds tested. Cholesterol oxidation in salame appeared to be inhibited by sesamol and ascorbate while catechin was much less effective. In mortadella the prooxidant effect of Na ascorbate was confirmed. All lipid oxidation parameters, though, showed low oxidation values so that no quality nor health deficiencies could be envisaged with any of the formulations adopted. Lower colour stability scores, though, would create commercial problems.

Proteomic changes involved in tenderization of bovine Longissimus dorsi muscle during prolonged ageing

To study proteomic changes involved in tenderization of bovine Longissimus dorsi four Charolaise heifers and four Charolaise bulls muscles were sampled at slaughter after early and long ageing (2-4°C for 12 and 26days respectively). Descriptive sensory evaluation of samples were performed and their tenderness evaluated by Warner-Bratzler shear force test. Protein composition of fresh muscle and of meat aged was analysed by cartesian and polar 2-D electrophoresis. Students t-test and Ranking-PCA analyses were performed to detect proteomic modulation, and the selected protein spots were identified by nano-HPLC-Chip MS/MS. This research has demonstrated that there are no differences between proteomic patterns of male and females Longissimus dorsi muscle, and that the extension of ageing beyond 12days, did not brings any concrete advantage in terms of sensory quality. Furthermore, the data presented here demonstrated that meat maturation caused changes of the abundance of proteins involved in metabolic, structural, and stress related processes.

Colour stability and vitamin E content of fresh and processed pork

The effect of increasing muscular content of vitamin E on colour intensity and stability of pork (both fresh and processed) was studied by feeding manipulation. Fresh pork was represented by loin chops and processed pork was represented by a dry cured fermented sausage (salame Milano) and raw cured ham (Parma ham). Dietary vitamin E was increased by feeding the animals with sunflower oil and α-tocopheryl acetate at 100 and 200 ppm. Chops were packed in oxygen-permeable film and in a protective atmosphere (80% O2 and 20% CO2) whereas salame Milano and Parma ham were packed under vacuum and in a protective atmosphere (85% N2 and 15% CO2). No differences in colour intensity or type were observed in relation to vitamin E content. Colour stability tests suggested, on the other hand, that higher vitamin E contents could be associated with slower myoglobin oxidation rates in fresh chops packed in a protective atmosphere. No effect of vitamin E on colour stability was observed in salame, probably because of the soft fat induced by sunflower oil. Significant differences among dietary groups were also not observed in Parma ham.

Lean colour of green and matured Parma hams: Comparative evaluation and technological relevance of sensory and objective data

Research has been conducted on the relationship between sensory evaluation and objective measurement of pork colour. The study also investigated the relationship between the colour of fresh meat and the colour of matured hams. Sensory evaluation was carried out at 24 h post mortem on the freshly cut surfaces of green hams trimmed for Parma ham production. Objective measurements were performed at the same time on Semimembranosus and Biceps femoris muscles with a Minolta Chromameter Reflectance II CR200/08. Cold carcass weight, lean content, trimmed ham weight, 45 min and 24 h post mortem pH of Semimembranosus muscle were also recorded. The hams were processed according to Parma ham technology. Weight losses at standard processing times were collected. At the end of processing a sample of about one-third of the hams was evaluated for internal lean colour and lean firmness both by sensory panel and objective measurements. Proximate composition was also determined. The results showed highly significant relationships between colour sensory scores and the coordinates L (∗), b (∗) and hue of the C.I.E. L (∗)a (∗)b (∗) colour system. Among the other parameters measured on fresh meat only 24 h pH was related at a very significant level with sensory and objective colour values. Correlation coefficients were generally higher for Semimembranosus than Biceps femoris. Matured ham colour was linked with fresh meat sensory judgements, L (∗), hue and a (∗) values. The relationship, though, was not sufficiently strong for use in predicting the colour of matured hams from green ham characteristics. Processing appears to have a positive effect on the colour of pale meat. Weight losses were mainly linked with lean meat content; other quality attributes being less important. Lean firmness of matured hams was related to the colour and pH of the fresh meat.

Use of Near-Infrared Spectroscopy for Fast Fraud Detection in Seafood: Application to the Authentication of Wild European Sea Bass (Dicentrarchus labrax)

The possibility of using near-infrared spectroscopy (NIRS) for the authentication of wild European sea bass ( Dicentrarchus labrax ) was investigated in this study. Three different chemometric techniques to process the NIR spectra were developed, and their ability to discriminate between wild and farmed sea bass samples was evaluated. One approach used spectral information to directly build the discrimination model in a latent variable space; the second approach first used wavelets to transform the spectral information and subsequently derived the discrimination model using the transformed spectra; in the third approach a cascaded arrangement was proposed whereby very limited chemical information was first estimated from spectra using a regression model, and this estimated information was then used to build the discrimination model in a latent variable space. All techniques showed that NIRS can be used to reliably discriminate between wild and farmed sea bass, achieving the same classification performance as classification methods that use chemical properties and morphometric traits. However, compared to methods based on chemical analysis, NIRS-based classification methods do not require reagents and are simpler, faster, more economical, and environmentally safer. All proposed techniques indicated that the most predictive spectral regions were those related to the absorbance of groups CH, CH(2), CH(3), and H(2)O, which are related to fat, fatty acids, and water content.