Silvia Mangani

Biogenic amine production by Oenococcus oeni.

The biogenic amine-producing capability of several Oenococcus oeni strains, originally isolated from different Italian wines, was determined. The amine-producing capability was quali-quantitatively variable among the strains: out of the 44 strains investigated under optimal growth conditions, more than 60% were able to produce histamine, at concentrations ranging from 1.0 to 33 mg/L, and about 16% showed the additional capability to form both putrescine and cadaverine, to different extents and variable relative proportions. The amine-producing behavior of the strains was confirmed under stress culture conditions, while performing malolactic fermentation. In wine, one randomly chosen strain was very effective in forming putrescine from ornithine. The formation of putrescine from arginine by some strains has been also demonstrated. Consequently, O. oeni can really and significantly contribute to the overall biogenic amine content of wines. Practical consequences of these findings are discussed.

Putrescine Accumulation in Wine: Role of Oenococcus oeni

Putrescine, the most abundant biogenic amine in wine, was proved to be produced by Oenococcus oeni strains in wine not only from ornithine but also from arginine. In this case, putrescine may originate from strains possessing the complete enzyme system to convert arginine to putrescine or by a metabiotic association, with an exchange of ornithine, between strains capable of metabolizing arginine to ornithine but unable to produce putrescine and strains capable of producing putrescine from ornithine but unable to degrade arginine. Putrescine production by this metabiotic association occurred once the malolactic fermentation was completed, whereas conversion of ornithine to putrescine by a single culture of the ornithine decarboxylating strain concurred with the degradation of malic acid. Moreover, in the former case, putrescine formation proceeded more slowly than in the latter. Metabiosis may play an important role in the accumulation of putrescine in wine, arginine being one of the major amino acids found in wine.

Effects of Microbial Populations on Anthocyanin Profile of Sangiovese Wines Produced in Tuscany, Italy

The effects of wine yeasts and malolactic bacteria on the anthocyanin profile of Sangiovese wines produced by both commercial- and laboratory-scale winemaking processes were investigated. The mean anthocyanin profile of the wines obtained from commercial winemaking processes, carried out in several wineries in Tuscany, showed a distinctive anthocyanin pattern characterized by high percentages of malvidin-3-glucoside, without appreciable levels of acylated anthocyanins. This anthocyanin pattern, also shared by all wines produced in the laboratory, reproduces the peculiar profile of Sangiovese grapes and distinguishes Sangiovese wines from Merlot and Cabernet Sauvignon wines. Principal component analysis of all anthocyanin data showed that the Sangiovese wines did not group on the basis of wine-producing area, harvest year, or winery but were distributed along a longitudinal axis, owning to the variability of cyanidin-3-glucoside, peonidin-3-glucoside, and malvidin-3-glucoside percentages. This variability was independent of the yeast ecology during fermentation, at least if the yeast ecology was described at the level of yeast species. In both commercial and experimental wines, higher percentages of vitisin A, a malvidin-3-glucoside derivative, were dependent on the growth and dominance of Candida zemplinina in the early stages of vinification. The anthocyanin profile of the Sangiovese wines was also maintained after malolactic fermentation.

Amino Acid Metabolisms and Production of Biogenic Amines and Ethyl Carbamate

In winemaking process, a wide range of volatile and non-volatile compounds originate from microbial catabolism of amino acids. Among these catabolites, biogenic amines, low molecular weight organic bases produced by decarboxylation of their respective free precursor amino acids, are receiving much attention in wine science because of their potential implication for human health. This chapter, after a brief overview on the occurrence of biogenic amines in wines, deals with the role played by yeasts and lactic acid bacteria in the formation and accumulation of these molecules during winemaking, giving emphasis to the most frequently found amines (histamine, tyramine and putrescine) and their physiological significance in bacterial cells. Moreover, the most suitable methods to detect biogenic amine-producing lactic acid bacteria or to quantify biogenic amine in wine as well as strategies to reduce biogenic amine content in wine are reported. Finally, a note on the formation of ethyl carbamate, a carcinogen compound originating in wine through a non-enzymatic reaction between ethanol and microbial catabolites containing a carbamyl group, is furnished.

Diversity of Saccharomyces cerevisiae Strains Isolated from Two Italian Wine-Producing Regions

Numerous studies, based on different molecular techniques analyzing DNA polymorphism, have provided evidence that indigenous Saccharomyces cerevisiae populations display biogeographic patterns. Since the differentiated populations of S. cerevisiae seem to be responsible for the regional identity of wine, the aim of this work was to assess a possible relationship between the diversity and the geographical origin of indigenous S. cerevisiae isolates from two different Italian wine-producing regions (Tuscany and Basilicata). For this purpose, sixty-three isolates from Aglianico del Vulture grape must (main cultivar in the Basilicata region) and from Sangiovese grape must (main cultivar in the Tuscany region) were characterized genotypically, by mitochondrial DNA restriction analysis and MSP-PCR by using (GTG)5 primers, and phenotypically, by determining technological properties and metabolic compounds of oenological interest after alcoholic fermentation. All the S. cerevisiae isolates from each region were inoculated both in must obtained from Aglianico grape and in must obtained from Sangiovese grape to carry out fermentations at laboratory-scale. Numerical analysis of DNA patterns resulting from both molecular methods and principal component analysis of phenotypic data demonstrated a high diversity among the S. cerevisiae strains. Moreover, a correlation between genotypic and phenotypic groups and geographical origin of the strains was found, supporting the concept that there can be a microbial aspect to terroir. Therefore, exploring the diversity of indigenous S. cerevisiae strains can allow developing tailored strategies to select wine yeast strains better adapted to each viticultural area.

Effect of Saccharomyces cerevisiae and Candida zemplinina on quercetin, vitisin A and hydroxytyrosol contents in Sangiovese wines

Quercetins, vitisin A and hydroxytyrosol are phenolic compounds possessing several positive properties to human health. This paper refers on the possible effects of two wine yeast species, Saccharomyces cerevisiae and Starmerella bacillaris (synonym Candida zemplinina) on the accumulation of these compounds in experimental Sangiovese wines. A single lot of Sangiovese grapes was fermented by S. cerevisiae alone or by sequential inoculum of C. zemplinina and S. cerevisiae under two aeration conditions. The accumulation of quercetin and its glycosides resulted only influenced by must aeration. However, yeast species occurring in the fermentative process affected the relative abundances among the different forms of quercetin. Vitisin A contents were higher in wines produced in the presence of C. zemplinina. Finally, higher concentrations of hydroxytyrosol and tyrosol were found in wines produced by S. cerevisiae alone under non-aerated condition. The fermentation of different Sangiovese grape musts carried out by the assayed S. cerevisiae strain pointed out that slow fermentation kinetics lead to higher levels of hydroxytyrosol and tyrosol. The study underlines the role of yeast species in determining the accumulation of bioactive compounds in Sangiovese wine.

Biogenic amine producing capability of bacterial populations isolated during processing of different types of dry fermented sausages

Abstract In order to assess the distribution of the biogenic amine (BA) producing capability within the bacterial populations occurring during production of dry fermented sausages, four different types of sausage processing, three with the use of starter cultures and one without, were investigated. All the main bacterial populations involved in the sausage processing showed a diffuse and strain dependent capability to produce BAs. However, quantitative determination of individual BAs produced by the bacterial isolates suggests an important role of enterococci in the accumulation of tyramine, the most abundant biogenic amine found in all investigated sausages.

Quantifying the Effects of Ethanol and Temperature on the Fitness Advantage of Predominant Saccharomyces cerevisiae Strains Occurring in Spontaneous Wine Fermentations

Different Saccharomyces cerevisiae strains are simultaneously or in succession involved in spontaneous wine fermentations. In general, few strains occur at percentages higher than 50% of the total yeast isolates (predominant strains), while a variable number of other strains are present at percentages much lower (secondary strains). Since S. cerevisiae strains participating in alcoholic fermentations may differently affect the chemical and sensory qualities of resulting wines, it is of great importance to assess whether the predominant strains possess a “dominant character.” Therefore, the aim of this study was to investigate whether the predominance of some S. cerevisiae strains results from a better adaptation capability (fitness advantage) to the main stress factors of oenological interest: ethanol and temperature. Predominant and secondary S. cerevisiae strains from different wineries were used to evaluate the individual effect of increasing ethanol concentrations (0-3-5 and 7% v/v) as well as the combined effects of different ethanol concentrations (0-3-5 and 7% v/v) at different temperature (25–30 and 35°C) on yeast growth. For all the assays, the lag phase period, the maximum specific growth rate (μmax) and the maximum cell densities were estimated. In addition, the fitness advantage between the predominant and secondary strains was calculated. The findings pointed out that all the predominant strains showed significantly higher μmax and/or lower lag phase values at all tested conditions. Hence, S. cerevisiae strains that occur at higher percentages in spontaneous alcoholic fermentations are more competitive, possibly because of their higher capability to fit the progressively changing environmental conditions in terms of ethanol concentrations and temperature.

Selection of autochthonous bacterial starters to produce typical Italian dry-fermented sausages with low biogenic amine content

Biogenic amines (BA) are organic bases with aliphatic, aromatic or heterocyclic structures that can be found in several foods [1,2]. These low molecular weight compounds, mainly originating from microbial decarboxylation of precursor amino acids [2-4], possess bioactive properties potentially dangerous to human health [5]. Excessive ingestion of BA can determine action on nervous, gastric and intestinal systems and blood pressure [1]. The most notorious food borne intoxications caused by BA are related to histamine (dilatation of peripheral blood vessels, capillaries and arteries, hypotension, flushing, headache, abdominal cramps, diarrhoea and vomiting) and tyramine (peripheral vasoconstriction, cardiac output increasing, releasing of noradrenaline from the sympathetic nervous system) [2,3]. Nevertheless, it must be taken into account that BA such as putrescine and cadaverine increase the toxicity of histamine and tyramine and can react with nitrite to form heterocyclic carcinogenic nitrosamines, nitrosopyrrolidine and nitrosopiperidine [3]. In humans, under normal conditions, the histamine and tyramine originating from foods are rapidly detoxified by the action of amine oxidases, but in the case of allergic individuals, BA accumulate in the body because of the presence of monoamine oxidase inhibitors [3]. Therefore, the toxicological level of BA is very difficult to be established.