Maria Martuscelli

Effects of pH, temperature and NaCl concentration on the growth kinetics, proteolytic activity and biogenic amine production of Enterococcus faecalis.

In this work, the combined effects of temperature, pH and NaCl concentration on the growth dynamics of Enterococcus faecalis EF37, its proteolytic activity and its production of biogenic amines have been studied. The effects of the selected variables have been analysed using a Central Composite Design. The production of biogenic amines, under the adopted conditions, was found to be mainly dependent on the extent of growth of E. faecalis. Its proteolytic activity was not a limiting factor for the final amine production, because in the system studied (skim milk) an excess of precursors was guaranteed. Quantitatively, the most important biogenic amine produced was 2-phenylethylamine but substantial amounts of tyramine were detected in all the samples. This work confirms that the main biological feature influencing the biogenic amine formation is the extent of growth of microorganisms, like E. faecalis, characterised by decarboxylase activity. In the traditional and artisanal cheeses produced using raw milk, enterococci usually reach levels of 10(7) cells/g. With this perspective, it is important that the presence of biogenic amines due to the activities of these microorganisms is maintained within safe levels, without affecting the positive effects of enterococci on the final organoleptic characteristics of the cheese.

Evolution of microbial populations and biogenic amine production in dry sausages produced in Southern Italy

E. PARENTE, M. MARTUSCELLI, F. GARDINI, S. GRIECO, M.A. CRUDELE AND G. SUZZI. 2001.

Characterization of the Enterobacteriaceae isolated from an artisanal Italian ewe's cheese (Pecorino Abruzzese)

Aims:  To evaluate some physiological characteristics of the Enterobacteriaceae isolated from Pecorino cheese.

Use of Staphylococcus xylosus as a starter culture in dried sausages: effect on the biogenic amine content.

The main objective of this work was to investigate if the use of Staphylococcus xylosus S81 as a starter culture in sausage production can influence the amount of histamine during ripening, and the concentration of the other most important biogenic amines, by influencing the activity of the microbial amino oxidases as well as the aminoacid decarboxylases. The results confirm that the biogenic amines presence in foods is the consequence of a complex equilibrium between the composition of the medium and the enzymatic activities of the microbial population. In addition, the results suggest that the presence and relative activity of amino oxidases should be considered as an important characteristic in the selection of starter cultures used in the production of fermented foods.

Biogenic amines content as a measure of the quality of wines of Abruzzo (Italy)

Aim of this research was to study the effect of some agronomic and oenological factors on the content of biogenic amines as quality index of sixty-five Abruzzo wines. Sum of amines was found to be decreasing in the order: red (19.3±12.8mgL(-1)), rosé (9.20±6.34mgL(-1)), white (7.67±3.84mgL(-1)) wine. Significant differences in relationship among amines levels and chemical and chemico-physical characteristics of red, white and rosé wine are due to their different biotechnological process and winemaking. Besides the aging treatment, influential seems to be the effect of the winery, regardless of the area in which it is situated. The single amines significantly correlated with their sum were putrescine, histamine and tyramine, even if reached levels were below toxicity threshold, demonstrating a good quality of the wines of Abruzzo whose consumption is no risk to the health of the consumer following the rules of proper nutrition.

Yeasts associated with Manteca

Manteca is a traditional milk product of southern Italy produced from whey deriving from Caciocavallo Podolico cheese-making. This study was undertaken to obtain more information about the microbiological properties of this product and particularly about the presence, metabolic activities, and technological significance of the different yeast species naturally occurring in Manteca. High numbers of yeasts were counted after 7 days ripening (10(4)-10(5) cfu g(-1)) and then decreased to 10(2) at the end. A total of 179 isolates were identified and studied for their phenotypic and genotypic characteristics. The most frequently encountered species were Trichosporon asahii (45), Candida parapsilosis (33), Rhodotorula mucilaginosa (32), Candida inconspicua (29). Some of these yeasts showed lipolytic activity (32 strains) and proteolytic activity (29 strains), NaCl resistance up to 10% and growth up to 45 degrees C (42 strains). Biogenic amines were formed by proteolytic strains, in particular phenylethylamine, putrescine and spermidine. Spermidine was produced by all the yeasts tested in this work, but only Trichosporon produced a great quantity of this compound. Histamine was not detectable. Caseinolytic activity was common to almost all strains, corresponding to the ability to efficiently split off amino-terminal amino acids. The highest and most constant activity expressed by all species was X-prolyl-dipeptidyl aminopeptidase. The findings suggest that the presence of yeasts may play a significant role in justifying interactions with lactic acid bacteria, and consequently with their metabolic activity in the definition of the peculiar characteristics of Manteca cheese.

Effect of Fermentation and Drying on Procyanidins, Antiradical Activity and Reducing Properties of Cocoa Beans

This work was aimed to determine the effect of fermentation and drying on the content and profile of procyanidins (from monomers P1 to polymers P10) as well as on the antiradical and scavenging properties of cocoa beans. To this purpose, three experiments were carried out: a traditional fermentation process followed by air drying and two pilot-scale fermentation processes by either natural microbiota or starter followed by sun drying. Procyanidins were evaluated by HPLC analysis, while the total polyphenol index (TPI), the antiradical activity as well as the reducing power were determined by means of the reaction with the Folin–Ciocalteu reagent, the decolorization assays of the ABTS radical (TEAC) and the Ferric Reducing Antioxidant Power (FRAP) methods, respectively. Both the traditional and pilot-scale processes resulted to affect the profile and content of the procyanidins fractions as well as the antiradical and reducing power functionality. Drying caused a severe reduction of compounds and thus resulted to be the critical step for the loss of procyanidins and monomers in particular. The indices of functionality generally showed a decreasing trend as a consequence of processing, and their evolution was similar to that observed in procyanidins content. To study the relationship between the individual procyanidins and the antioxidant activity expressed as TEAC, FRAP and TPI, the data set were processed by modified partial least squares regression. The obtained models presented a good predictive ability. Normalised regression coefficients showed that the relative contribution of each single class of compounds to total antioxidant activity resulted as follows: P1 > P2 > P3 > P4 > P6 > P8 > P5 > P7 > P9 >> P10.

Microbiological characteristics of kumis, a traditional fermented Colombian milk, with particular emphasis on enterococci population

Kumis is a traditional fermented cow milk produced and consumed in South West Colombia. The main objective of this research was to studied the enterococcal population, present in 13 kumis samples traditionally manufactured, for their role as beneficial organisms or opportunistic pathogens. The molecular identification of 72 isolates evidenced that Enterococcus faecalis and E. faecium were the dominant species. The genes gelE, esp, asa1, cyl and hyl, all associated with virulence factors in enterococci, were detected in 30 isolates, while 42 were free of virulence determinants. Skim milk media were fermented by all the different isolates and further tested for proteolysis (free NH(3) groups), Angiotensin-I Converting Enzyme (ACE) inhibitory activity and biogenic amines production. Nine E. faecalis and two E. faecium strains produced fermented milk with ACE-inhibitory activity values ranging from 39.7% to 84.35% .The digestion of fermented milk samples by pepsin and pancreatin evidenced an increase in ACE inhibitory activity, with E. faecalis KE09 as the best producer (IC50 = 14.25 μg ml(-1)). Moreover, the strains showed a very low tyrosine decarboxylase activity and did not produce histamine during 48 h fermentation in milk. This study underlines the that Colombian kumis is a good source of not virulent enterococci able to produce fermented milks with ACE-inhibitory activity.

Control of household mycoflora in fermented sausages using phenolic fractions from olive mill wastewaters.

Biopreservation using polyphenols represents an alternative to chemical molecules for improving food safety. In this work, we evaluated the antifungal activity of polyphenols extracted from olive mill wastewater (OMWWP) to reduce or eliminate the growth of undesired fungi on the surface of dry fermented sausages. Antagonism against Penicillium expansum DSMZ 1282, Penicillium verrucosum DSMZ 12639, Penicillium nalgiovense MS01, Aspergillus ochraceus DSMZ 63304, Cladosporium cladosporioides MS12, and Eurotium amstelodami MS10 was evident at 1.25% OMWWP in vitro, whereas in situ application of 2.5% OMWWP strongly reduced undesired household fungal species such as C. cladosporioides, Penicillium aurantiogriseum, Penicillium commune, and Eurotium amstelodami, while a moderate antagonistic activity towards P. nalgiovense and Penicillium chrysogenum was observed at the same concentration. OMWWP at the concentrations used in this study demonstrated species-dependent antifungal activity by inhibiting both fungal growth and spore germination. Therefore, OMWWP can be regarded as a potential alternative to synthetic antifungal compounds to preserve the product from both oxidation and undesired fungi, without changing the sensory characteristics.

A survey of Saccharomyces populations associated with wine fermentations from the Apulia region (South Italy)

The aim of this paper was to investigate the genetic and phenotypic characteristics of yeasts isolated from samples of grape musts collected from four different areas of Apulia region. The 68 yeast isolates were identified asSaccharomyces cerevisiae by PCR-RFLP of 5.8S-ITS region of the rRNA gene. Individual isolates were differentiated by RAPD-PCR and AFLP. The following oenological traits were studied: fermentation power, resistance to cycloheximide, alcohol and SO2, formation of SO2 and H2S, β-glucosidase activity, and production of biogenic amines and secondary compounds. Many phenotypes were common to several yeasts isolated from the four different areas, such as high SO2 resistance and fermentation power. In addition, someS. cerevisiae isolates showed a β-glucosidase activity and others had a high resistance to cycloheximide. All the strains formed biogenic amines. Solid Phase Microextraction was used to determine secondary compounds produced in wine by the single yeast cultures.