Effects of Starter Cultures and Type of Casings on the Microbial Features and Volatile Profile of Fermented Sausages

In the literature, the effect of the type of casing on fermented sausages is quite unexplored, while several studies are focused on the impact of starter cultures. Therefore, this paper studied the effect of three commercial starter cultures and two casings (natural or collagen) on Italian fermented sausages. Physico-chemical parameters (aw, pH, weight loss), microbiota, aroma profile and sensory analysis were evaluated. Results showed that collagen casings promoted a higher reduction of pH and weight loss. Concerning the microbiota, samples with natural casing had higher counts of lactic acid bacteria, while yeast proliferation was promoted in those with collagen. Regardless of the starters and casings applied, levels of enterococci and Enterobacteriaceae were low (≤2 log CFU/g). The aroma profile was significantly affected by casing: despite the starter applied, the presence of collagen casing favoured acid accumulation (mainly acetate and butanoate) and reduction of ketones. Sensory analysis highlighted significant differences only for odour, colour intensity and sourness. The differences observed suggest that collagen casings may provide a greater availability of oxygen. Overall, casings rather than starter cultures impact the microbial and sensorial features of fermented sausages

Bacterial community of Industrial raw Sausage Packaged in Modified Atmosphere throughout the Shelf Life

Ten lots of industrial raw sausages in modified atmosphere (CO2 30%, O2 70%), produced in the same plant over 7\u202fmonths, were analyzed at the day after production (S samples) and at the end of shelf life (E samples), after 12\u202fdays storage at 7\u202f\ub0C to simulate thermal abuse. Quality of the products was generally compromised by storage at 7\u202f\ub0C, with only 3 E samples without alterations. During the shelf life, the pH decreased for the accumulation of acetic and lactic acids. A few biogenic amines accumulated, remaining below acceptable limits. The profile of volatile compounds got enriched with alcohols, ketones, and acids (e.g. ethanol, 2,3-butanediol, 2,3-butandione, butanoic acid) originated by bacterial metabolism. Throughout the shelf life, aerobic bacteria increased from 4.7 log to 6.6\u202flog\u202fcfu/g, and lactic acid bacteria (LAB) from 3.7 to 8.1\u202flog\u202fcfu/g. Staphylococci, enterobacteria, and pseudomonads passed from 3.7, 3.0, and 1.7 to 5.5, 4.8, and 3.0\u202flog\u202fcfu/g, respectively. Dominant cultivable LAB, genotyped by RAPD-PCR, belonged to the species Lactobacillus curvatus/graminis and Lactobacillus sakei, with lower amounts of Leuconostoc carnosum and Leuconostoc mesenteroides. Brochothrix thermosphacta was the prevailing species among aerobic bacteria. The same biotypes ascribed to several different species where often found in E samples of diverse batches, suggesting a recurrent contamination from the plant of production. Profiling of 16S rRNA gene evidenced that microbiota of S samples clustered in two main groups where either Firmicutes or Bacteroidetes prevailed, albeit with taxa generally associated to the gastro-intestinal tract of mammals. The microbial diversity was lower in E samples than in S ones. Even though a common profile could not be identified, most E samples clustered together and were dominated by Firmicutes, with Lactobacillaceae and Listeriaceae as the most abundant families (mostly ascribed to Lactobacillus and Brochothrix, respectively). In a sole E sample Proteobacteria (especially Serratia) was the major phylum

The Low Temperature Heat Capacity of LaPO4 and GdPO4, the Thermodynamic Functions of the Monazite-type LnPO4 Series

See abstract in the article attachedJRC.E.4-Nuclear fuel

The High-temperature Heat Capacity of ThPd3 and UPd3

The enthalpy increments of UPd3 and ThPd3 have been measured using the drop calorimetry for temperature range (480 to 1290) K. The heat capacity curves have been derived using the simultaneous linear regression of our data and the low temperature heat capacity data from previous studies. Furthermore the Schottky contributions for UPd3 were determined by comparing the ThPd3 and UPd3 heat capacity functions and correlated with the theoretical values calculated from the crystal field energy levels.JRC.E.3-Materials researc

Correlation between volatile profiles of Italian fermented sausages and their size and starter culture

Abstract The aroma profiles of 10 traditional Italian fermented sausages were evaluated. The volatile organic compounds (VOCs) obtained by solid-phase microextraction and gas chromatograph-mass spectrometry were analysed using principal component analysis (PCA) and linear discriminant analysis (LDA). PCA allowed an acceptable separation but some sausage typologies were not well separated. On the other hand, the supervised approach of LDA allowed a clear grouping of the samples in relation to sausage size and starter culture. In spite of the extreme variability of the volatile profiles of the sausage typologies, this work showed the influence of diameter on VOC profile. The differences observed can be related to the effects that some fundamental physicochemical characteristics (such as water loss kinetics and oxygen availability) have on the results of ripening processes. Differences in VOC profiles were also observed due to the lactic acid bacteria used as starter cultures, with differences mainly attributable to compounds deriving from pyruvate metabolism

Physico-chemical and microbiological characterisation of Italian fermented sausages in relation to their size

The aim of this work was to study the physico-chemical and microbiological parameters of 10 Italian fermented sausages, produced industrially, in order to highlight the differences in relation to their size. The sausages were classified as small, medium and large and the data concerning every feature considered were analysed with some statistical explorative tools: ANOVA, principal component analysis (PCA) and linear discriminant analysis (LDA)

Changes in Microbiota of Fresh Sausage Throughout Shelf Life

Introduction: Fresh sausage is a perishable product easily colonized by spoilage bacteria. Microbial diversity of fresh sausage has been generally investigated using traditional cultural methods. Purpose: The present study aimed to obtain an exhaustive description of the microbiota composition and diversity throughout the shelf life of fresh sausage. Methods: Cultivable bacteria from ten batches of sausage provided by the same factory were enumerated on PCA, MRS, Mac Conkey, ALOA, and PDA plates, at delivery and after 12 days at 7°C. The dominant strains were genotyped by RAPD-PCR fingerprinting, and taxonomic diversity was estimated by partial sequencing of 16S rRNA genes. A comprehensive picture of bacteria was obtained by metataxonomic analysis of Illumina 16S sequences. Results: The mean charge (log of CFU/g) of cultivable aerobic and aerotolerant bacteria started at 5.0 and reached 7.2 after 12 days at 7°C, with a concomitant drop of pH from 5.9 to 5.5. Lactic acid bacteria showed the highest increase starting from 4.1 and reaching 8.6 log, followed by Staphylococci (4.0 to 6.5 log) and by Enterobactericeae (3.2 to 6.2 log). The majority of MRS biotypes belonged to Lactobacillus curvatus, followed by Lactobacillus sakei, Leuconostoc carnosum, and Leuconostoc mesenteroides. The most represented species in PCA was Brochotrix thermosphacta. Metataxonomic analysis revealed that at packaging, fresh sausage was characterized by bacteria generally ascribable to two diverse microbiota associated with gut microbes. At the end of the shelf life, Firmicutes dominated the microbiota, in some cases with prevalence of Lactobacillales. In other samples, Listeriaceae took over, with Brochothrix being the most represented genus. Enterobacteriaceae, generally ascribed to Serratia, were abundant in a few samples at the end of the shelf life. Significance: This study provided a wide overview of microbiota evolution in fresh sausage, shedding light on meat hygiene and safety issues

Effects of the diameter on physico-chemical, microbiological and volatile profile in dry fermented sausages produced with two different starter cultures

Four batches of Milano-type dry fermented sausages were industrially produced to evaluate the effects of two different lactic acid bacteria starter cultures (Lactobacillus sakei and Pediococcus pentosaceus) and diameter on physico-chemical, microbiological and aroma characteristics during processing and in the final products. Values of aw and pH were similar in the final sausages. Lactic acid bacteria counts were high and slightly influenced by the diameter, while higher concentrations of staphylococci were found in small sausages. The diameter had a strong influence on the formation of volatile organic compounds, as revealed by PCA analysis. The main differences regarded ketones (acetone, 2-butanone, 3-hydroxy-2-butanone and 2,3-butandione) and aldehydes (mainly hexanal). The influence of starter cultures was less evident, also due to the presence of indigenous L. sakei in the sausages inoculated with pediococci. Nevertheless, the choice of L. sakei or P. pentosaceus as starter culture showed a direct effect on some of the main process parameters (fermentation and acidification rate) and generation of volatile compounds. The results evidenced the need to optimize the process to increase starter culture performances

X-ray Diffraction, Mössbauer Spectroscopy, Magnetic Susceptibility, and Specific Heat Investigations of Na4NpO5 and Na5NpO6

The hexavalent and heptavalent sodium neptunate compounds Na4NpO5 and Na5NpO6 have been investigated using X-ray powder diffraction, Mössbauer spectroscopy, magnetic susceptibility, and specific heat measurements. Na4NpO5 has tetragonal symmetry in the space group I4/m, while Na5NpO6 adopts a monoclinic unit cell in the space group C2/m. Both structures have been refined for the first time using the Rietveld method. The valence states of neptunium in these two compounds, i.e., Np(VI) and Np(VII), respectively, have been confirmed by the isomer shift values of their Mössbauer spectra. The local structural properties obtained from the X-ray refinements have also been related to the quadrupole coupling constants and asymmetry parameters determined from the Mössbauer studies. The absence of magnetic ordering has been confirmed for Na4NpO5. However, specific heat measurements at low temperatures have suggested the existence of a Schottky-type anomaly at around 7 K in this Np(VI) phase.JRC.E.3-Materials researc

Mössbauer spectroscopy, magnetization, magnetic susceptibility, and low temperature heat capacity of alpha-Na2NpO4

The physical and chemical properties at low temperatures of hexavalent disodium neptunate alpha-Na2NpO4 are investigated for the first time in this work using Mossbauer spectroscopy, magnetization, magnetic susceptibility, and heat capacity measurements. The Np(VI) valence state is confirmed by the isomer shift value of the Mössbauer spectra, and the local structural environment around the neptunium cation is related to the fitted quadrupole coupling constant and asymmetry parameters. Moreover, magnetic hyperfine splitting is reported below 12.5 K, which could indicate magnetic ordering at this temperature. This interpretation is further substantiated by the existence of a -peak at 12.5 K in the heat capacity curve, which is shifted to lower temperatures with the application of a magnetic field, suggesting antiferromagnetic ordering. However, the absence of any anomaly in the magnetization and magnetic susceptibility data shows that the observed transition is more intricate. In addition, the heat capacity measurements suggest the existence of a Schottky-type anomaly above 15 K associated with a low-lying electronic doublet found about 60 cm−1 above the ground state doublet. The possibility of a quadrupolar transition associated with a ground state pseudoquartet is thereafter discussed. The present results finally bring new insights into the complex magnetic and electronic peculiarities of alpha-Na2NpO4.JRC.G.I.3-Nuclear Fuel Safet