Discovering the Influence of Microorganisms on Wine Color

Flavor, composition and quality of wine are influenced by microorganisms present on the grapevine surface which are transferred to the must during vinification. The microbiota is highly variable with a prevalence of non-Saccharomyces yeasts, whereas Saccharomyces cerevisiae is present at low number. For wine production an essential step is the fermentation carried out by different starter cultures of S. cerevisiae alone or in mixed fermentation with non-Saccharomyces species that produce wines with significant differences in chemical composition. During vinification wine color can be influenced by yeasts interacting with anthocyanin. Yeasts can influence wine phenolic composition in different manners: direct interactions—cell wall adsorption or enzyme activities—and/or indirectly—production of primary and secondary metabolites and fermentation products. Some of these characteristics are heritable trait in yeast and/or can be strain dependent. For this reason, the stability, aroma, and color of wines depend on strain/strains used during must fermentation. Saccharomyces cerevisiae or non-Saccharomyces can produce metabolites reacting with anthocyanins and favor the formation of vitisin A and B type pyranoanthocyanins, contributing to color stability. In addition, yeasts affect the intensity and tonality of wine color by the action of β-glycosidase on anthocyanins or anthocyanidase enzymes or by the pigments adsorption on the yeast cell wall. These activities are strain dependent and are characterized by a great inter-species variability. Therefore, they should be considered a target for yeast strain selection and considered during the development of tailored mixed fermentations to improve wine production. In addition, some lactic acid bacteria seem to influence the color of red wines affecting anthocyanins’ profile. In fact, the increase of the pH or the ability to degrade pyruvic acid and acetaldehyde, as well as anthocyanin adsorption by bacterial cells are responsible for color loss during malolactic fermentation. Lactic acid bacteria show different adsorption capacity probably because of the variable composition of the cell walls. The aim of this review is to offer a critical overview of the roles played by wine microorganisms in the definition of intensity and tonality of wines’ color.

Correlation between IRC7 gene expression and 4-mercapto-4-methylpentan-2-one production in Saccharomyces cerevisiae strains

Volatile thiols are not present in must but are synthesized and released by wine yeasts during alcoholic fermentation. In this study, autochthonous and commercial Saccharomyces cerevisiae strains were characterized for the expression of the main genes involved in thiols metabolism and their production in wine. New primer sets were developed on the basis of the S288c genome to evaluate the expression of Cys3, Cys4, MET17 and IRC7 genes. Obtained data revealed the occurrence of some thiols, for example, 4-mercapto-4-methylpentan-2-one (4-MMP) and 3-mercaptohexan-1-ol (3-MH) in Pecorino white wine. All genes were upregulated, but only for IRC7 was found a correlation with 4-MMP release: strains with the highest production showed the highest transcription level. IRC7 gene could be proposed as target for the selection of S. cerevisiae strains to increase thiols content in wine.

Intraspecies polymorphisms of Kluyveromyces marxianus strains from Yaghnob valley

In this study, 29 strains of Kluyveromyces marxianus with peculiar genetic and phenotypic traits previously isolated from a fermented goat milk of Yaghnob valley were investigated for chromosome length polymorphism (CLP) by PFGE, adhesion properties and carbon usage by Biolog analysis. Obtained data showed that strains differed in terms of number and size of chromosome bands. The number of bands ranged from 5 to 7, suggesting a probable genome size from 1.4 to 2.6 Mb. Strains showed a certain level of cell surface hydrophobicity ranging from 32% to 77.7%. Strains were also tested for their ability to form a biofilm on polystyrene plates: planktonic cells ranged from 6.3 cfu/mL to 7.95 cfu/mL, while sessile from 7.11 cfu/mL to 8.6 cfu/mL. The strains able to adhere to polystyrene plates were also able to form a mature MAT. Biolog analysis revealed that almost all strains were able to use putrescine, malic acid, α-D lactose, phenylethylamine, β-methyl D-gucoside and xylose; 5 strains were able to grow on cellobiose and 3 were able to catabolise α-ketobutyric. The obtained data highlighted a number of interesting features underlying the peculiar capacities of these strains for industrial applications.

Accumulation γ-Aminobutyric Acid and Biogenic Amines in a Traditional Raw Milk Ewe's Cheese

The influence of calf (R1), kid (R2) and pig (R3) rennets on microbiota, biogenic amines (BAs) and γ-aminobutyric acid (GABA) accumulation in raw milk ewe's cheeses was evaluated. Cheeses were investigated at different ripening times for their microbial composition, free amino acids (FAAs), BAs and GABA content. Moreover, the expression of tyrosine (tdc) and histidine (hdc) decarboxylases genes was evaluated by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Microbial counts showed similar values in all samples. Pig rennet were cheeses were characterized by higher proteolysis and the highest values of BAs. The BAs detected were putrescine, cadaverine and tyramine, while histamine was absent. qRT-PCR confirmed this data, in fact hdc gene was not upregulated, while tdc gene expression increased over time in agreement with the increasing content of tyramine and the highest fold changes were detected in R3 cheeses. GABA showed the highest concentration in R2 cheeses reaching a value of 672 mg/kg. These results showed that the accumulation of BAs and GABA in Pecorino di Farindola is influenced by ripening time and type of coagulant. Further studies are required to develop starter cultures to reduce BAs content and improve health characteristics of raw milk ewe's cheeses.

Cell Wall Surface Properties of Kluyveromyces marxianus Strains From Dairy-Products

Thirty-three Kluyveromyces marxianus strains were tested for the ability to form biofilm and mat structures in YPD and whey and for cell surface hydrophobicity. To identify genes potentially involved in adhesion properties, a RT-qPCR analysis was performed. Eight strains were able to adhere on polystyrene plates in both media and formed a mature mat structure. These strains showed a different level of hydrophobicity ranging from 55 to 66% in YPD and from 69 to 81% in whey. Four K. marxianus orthologs genes (FLO11, STE12, TPK3, and WSC4), known from studies in other yeast to be involved in biofilm formation, have been studied. FLO11 and STE12 showed the highest fold changes in all conditions tested and especially in whey: 15.05 and 11.21, respectively. TPK3 was upregulated only in a strain, and WSC4 in 3 strains. In YPD, fold changes were lower than in whey with STE12 and FLO11 genes showing the highest fold changes. In mat structures FLO11 and STE12 fold changes ranged from 3.6-1.3 to 2-1.17, respectively. Further studies are necessary to better understand the role of these genes in K. marxianus adhesion ability.

Influence of Iodine Feeding on Microbiological and Physico-Chemical Characteristics and Biogenic Amines Content in a Raw Ewes' Milk Cheese

Iodine is an essential trace element involved in the regulation of thyroid metabolism and antioxidant status in humans and animals. The aim of this study was to evaluate the effect of ewes’ dietary iodine supplementation on biogenic amines content as well as microbiological and physico-chemical characteristics in a raw milk cheese at different ripening times (milk, curd, and 2, 7, 15, 30, 60, and 90 days). Two cheese-making trials were carried out using milk from ewes fed with unifeed (Cheese A) or with the same concentrate enriched with iodine (Cheese B). The results indicated that the counts of principal microbial groups and physico-chemical characteristics were quite similar in both cheeses at day 90. Cheese B was characterized by a higher content of biogenic amines and propionic acid. Propionic bacteria were found in both cheeses mainly in Trial B in agreement with the higher content of propionic acid detected.

Determination of Lipophilic Marine Biotoxins in Mussels Harvested from the Adriatic Sea by LC-MS/MS

Lipophilic marine biotoxins include okadaic acid, pectenotoxin, yessotoxin and azaspiracid groups. The consumption of contaminated molluscs can lead to acute food poisoning syndromes depending on the exposure level. Regulatory limits have been set by Regulation (European Community, 2004a) No 853/2004 and LC-MS/MS is used as the official analytical method according to Regulation (European Community, 2011) No 15/2011. In this study specimens of mussels (Mytilus galloprovincialis) were collected along the coasts of the central Adriatic Sea during the years 2015–2017 and analyzed by the European harmonized Standard Operating Procedure. The method was validated for linearity, specificity, repeatability and reproducibility and it revealed able to be used for the detection of the lipophilic marine biotoxins. Levels of okadaic acid, pectenotoxin, yessotoxin and its analogs were detected at different concentrations in 148 (37%) out of a total of 400 samples, always below the maximum limits, except for 11 (4.3%) of them that were non-compliant because they exceeded the regulatory limit. Moreover, some samples were exposed to a multi-toxin mixture with regards to okadaic acid, yessotoxin and 1-Homo yessotoxin. Following these results, the aquaculture farms from which the non-compliant samples derived were closed until the analytical data of two consecutive samplings returned favorable. Besides the potential risk of consumption of mussels contaminated by lipophilic marine biotoxins, these marine organisms can be considered as bio-indicators of the contamination status of the marine ecosystem.

Development and implementation of multilocus sequence typing to study the diversity of the yeast Kluyveromyces marxianus in Italian cheeses

The yeast Kluyveromyces marxianus possesses advantageous traits like rapid growth, GRAS (generally regarded as safe) status and thermotolerance that make it very suitable for diverse biotechnological applications. Although physiological studies demonstrate wide phenotypic variation within the species, there is only limited information available on the genetic diversity of K. marxianus. The aim of this work was to develop a multilocus sequence typing (MLST) method for K. marxianus to improve strain classification and selection. Analysis of housekeeping genes in a number of sequenced strains led to the selection of five genes, IPP1, TFC1, GPH1, GSY2 and SGA1, with sufficient polymorphic sites to allow MLST analysis. These loci were sequenced in an additional 76 strains and used to develop the MLST. This revealed wide diversity in the species and separation of the culture collection and wild strains into multiple distinct clades. Two subsets of strains that shared sources of origin were subjected to MLST and split decomposition analysis. The latter revealed evidence of recombination, indicating that this yeast undergoes mating in the wild. A public access web-based portal was established to allow expansion of the database and application of MLST to additional K. marxianus strains. This will aid understanding of the genetic diversity of the yeast and facilitate biotechnological exploitation.

Histamine Food Poisoning

The consumption of food containing high amounts of histamine and other biogenic amines can cause food poisoning with different symptoms linked to the individual sensitivity and the detoxification activity. Histamine is the only biogenic amine with regulatory limits set by the European Commission in fish and fishery products, because it can lead to a fatal outcome. However, also fermented foods can be involved in outbreaks and sporadic cases of intoxication. The factors affecting the presence of histamine in food are variable and product specific including the availability of the precursor amino acid, the presence of microorganisms producing decarboxylases, and the conditions allowing their growth and enzyme production. Generally, the good quality of raw material and hygienic practices during food processing as well as the use of histidine decarboxylase-negative starter cultures can minimize the occurrence of histamine. Further studies are necessary to estimate the human exposure and the relationship between the total amount of the biogenic amines ingested with food and health effects.

Technological Factors Affecting Biogenic Amine Content in Foods: A Review

Biogenic amines (BAs) are molecules, which can be present in foods and, due to their toxicity, can cause adverse effects on the consumers. BAs are generally produced by microbial decarboxylation of amino acids in food products. The most significant BAs occurring in foods are histamine, tyramine, putrescine, cadaverine, tryptamine, 2-phenylethylamine, spermine, spermidine, and agmatine. The importance of preventing the excessive accumulation of BAs in foods is related to their impact on human health and food quality. Quality criteria in connection with the presence of BAs in food and food products are necessary from a toxicological point of view. This is particularly important in fermented foods in which the massive microbial proliferation required for obtaining specific products is often relater with BAs accumulation. In this review, up-to-date information and recent discoveries about technological factors affecting BA content in foods are reviewed. Specifically, BA forming-microorganism and decarboxylation activity, genetic and metabolic organization of decarboxylases, risk associated to BAs (histamine, tyramine toxicity, and other BAs), environmental factors influencing BA formation (temperature, salt concentration, and pH). In addition, the technological factors for controlling BA production (use of starter culture, technological additives, effects of packaging, other non-thermal treatments, metabolizing BA by microorganisms, effects of pressure treatments on BA formation and antimicrobial substances) are addressed.

Marine Biotoxins: Occurrence, Toxicity, Regulatory Limits and Reference Methods

Harmful algal blooms are natural phenomena caused by the massive growth of phytoplankton that may contain highly toxic chemicals, the so-called marine biotoxins causing illness and even death to both aquatic organisms and humans. Their occurrence has been increased in frequency and severity, suggesting a worldwide public health risk. Marine biotoxins can accumulate in bivalve molluscs and regulatory limits have been set for some classes according to European Union legislation. These compounds can be distinguished in water- and fat-soluble molecules. The first group involves those of Paralytic Shellfish Poisoning and Amnesic Shellfish Poisoning, whereas the toxins soluble in fat can cause Diarrheic Shellfish Poisoning and Neurotoxic Shellfish Poisoning. Due to the lack of long-term toxicity studies, establishing tolerable daily intakes for any of these marine biotoxins was not possible, but an acute reference dose can be considered more appropriate, because these molecules show an acute toxicity. Dietary exposure assessment is linked both to the levels of marine biotoxins present in bivalve molluscs and the portion that could be eaten by consumers. Symptoms may vary from a severe gastrointestinal intoxication with diarrhea, nausea, vomiting, and abdominal cramps to neurological disorders such as ataxia, dizziness, partial paralysis, and respiratory distress. The official method for the detection of marine biotoxins is the mouse bioassay (MBA) showing some limits due to ethical restrictions and insufficient specificity. For this reason, the liquid chromatography-mass spectrometry method has replaced MBA as the reference technique. However, the monitoring of algal blooms producing marine biotoxins should be regularly assessed in order to obtain more reliable, accurate estimates of bloom toxicity and their potential impacts.

Food borne bacterial models for detection of benzo[a]pyrene-DNA adducts formation using RAPD-PCR

Random amplified polymorphic DNA (RAPD) PCR is a feasible method to evaluate genotoxin-induced DNA damage and mutations. In this study, Lactobacillus plantarum ATCC 14917T, Enterococcus faecium DSMZ 20477T, Escherichia coli PQ37 and Saccharomyces cerevisiae S441 were screened for DNA genetic alterations by DNA fingerprinting using M13 and LA1 primers after treatment with three compounds forming covalent adducts with DNA [benzo[a]pyrenediol epoxide (BPDE), methyl methanesulfonate and 1,2,3,4-diepoxybutane (DEB)]. M13 RAPD fingerprinting revealed that the total number of bands decreased in all treated DNA compared to control samples and generally the lost bands were characterized by high molecular weight. Some extra bands were detected for L. plantarum and E. faecium, while in E. coli and S. cerevisiae DNAs BPDE and DEB treatments did not result in new extra bands. Besides qualitatively analysis, cluster analysis based on Unweighted Pair-Group Method with Average algorithm was performed to compare DNA fingerprints before and after treatments. This analysis confirmed the absence of significant differences between negative controls and treated DNA in S. cerevisiae and E. coli however the disappearance of some bands can be detected. The data indicate that this approach can be used for DNA damage detection and mutations induced by genotoxic compounds and highlighted the possible use of L. plantarum and E. faecium M13 based fingerprinting as reference for hazard identification in risk assessment.

Aroma Profile of Montepulciano d'Abruzzo Wine Fermented by Single and Co-culture Starters of Autochthonous Saccharomyces and Non-saccharomyces Yeasts

Montepulciano d'Abruzzo is a native grape variety of Vitis vinifera L., grown in central Italy and used for production of high quality red wines. Limited studies have been carried out to improve its enological characteristics through the use of indigenous strains of Saccharomyces cerevisiae. The main objective of the present work was to test two indigenous strains of S. cerevisiae (SRS1, RT73), a strain of Starmerella bacillaris (STS12), one of Hanseniaspora uvarum (STS45) and a co-culture of S. cerevisiae (SRS1) and S. bacillaris (STS12), in an experimental cellar to evaluate their role in the sensory characteristic of Montepulciano d'Abruzzo wine. A S. cerevisiae commercial strain was used. Fermentations were conducted under routine Montepulciano d'Abruzzo wine production, in which the main variables were the yeast strains used for fermentation. Basic winemaking parameters, some key chemical analysis and aroma compounds were considered. S. cerevisiae strain dynamics during fermentation were determined by molecular methods. The musts inoculated with the co-culture were characterized by a faster fermentation start and a higher content of glycerol after 3 days of fermentation, as well as the musts added with strains S. bacillaris (STS12) and H. uvarum (STS45). At the end of fermentation the parameters studied were quite similar in all the wines. Total biogenic amines (BA) content of all the wines was low. Ethanolamine was the predominant BA, with a concentration ranging from 21 to 24 mg/l. Wines were characterized by esters and alcohols. In particular, 2-phenylethanol, 3-methylbut-1-yl methanoate, and ethyl ethanoate were the major aroma volatile compounds in all wines. Statistical analysis highlighted the different role played by aroma compounds in the differentiation of wines, even if it was impossible to select a single class of compounds as the most important for a specific yeast. The present study represents a further step toward the use of tailored autochthonous strains to impart the specific characteristics of a given wine which are an expression of a specific terroir.

Biodiversity of autolytic ability in flocculent Saccharomyces cerevisiae strains suitable for traditional sparkling wine fermentation

Yeasts involved in secondary fermentation of traditional sparkling wines should show specific characteristics, such as flocculation capacity and autolysis. Recently it has been postulated that autophagy may contribute to the outcome of autolysis. In this study, 28 flocculent wine Saccahromyces cerevisiae strains characterized by different flocculation degrees were studied for their autolytic and autophagic activities. Autolysis was monitored in synthetic medium through the determination of amino acid nitrogen and total proteins released. At the same time, novel primer sets were developed to determine the expression of the genes ATG1, ATG17 and ATG29. Twelve strains were selected on the basis of their autolytic rate and ATG gene expressions in synthetic medium and were inoculated in a base wine. After 30, 60 and 180 days the autolytic process and ATG gene expressions were evaluated. The obtained data showed that autolysis and ATG gene expressions differed among strains and were independent of the degree of flocculation. This biodiversity could be exploited to select new starter stains to improve sparkling wine production. Copyright © 2016 John Wiley & Sons, Ltd.

In Lactobacillus pentosus, the olive brine adaptation genes are required for biofilm formation

Lactobacillus pentosus is one of the few lactic acid bacteria (LAB) species capable of surviving in olive brine, and thus desirable during table olive fermentation. We have recently generated mutants of the efficient strain L. pentosus C11 by transposon mutagenesis and identified five mutants unable to survive and adapt to olive brine conditions. Since biofilm formation represents one of the main bacterial strategy to survive in stressful environments, in this study, the capacity of adhesion and formation of biofilm on olive skin was investigated for this strain and five derivative mutants which are interrupted in metabolic genes (enoA1 and gpi), and in genes of unknown function ("oba" genes). Confocal microscopy together with bacteria count revealed that the sessile state represented the prevailing L. pentosus C11 life-style during table olive fermentation. The characterization of cell surface properties showed that mutants present less hydrophobic and basic properties than the wild type (WT). In fact, their ability to adhere to both abiotic (polystyrene plates) and biotic (olive skin) surfaces was lower than that of the WT. Confocal microscopy revealed that mutants adhered sparsely to the olive skin instead of building a thin, multilayer biofilm. Moreover, RT-qPCR showed that the three genes enoA1, gpi and obaC were upregulated in the olive biofilm compared to the planktonic state. Thus enoA1, gpi and "oba" genes are necessary in L. pentosus to form an organized biofilm on the olive skin.

Concentrations of Contaminants with Regulatory Limits in Samples of Clam (Chamelea gallina) Collected along the Abruzzi Region Coast in Central Italy

Concentrations of pollutants with regulatory limits were determined in specimens of Chamelea gallina, a species of clam collected along the Abruzzi coastal region of the central Adriatic Sea. Nine sampling sites were selected to evaluate the distribution of contaminants in the environment and the health risk for consumers. The concentrations of all the examined compounds were lower than the maximums set by European legislation. Polycyclic aromatic hydrocarbons and total mercury were below the detection limit (0.18 μg/kg for benzo[a]anthracene, 0.30 μg/kg for chrysene, 0.12 μg/kg for benzo[b]fluoranthene, 0.08 μg/kg for benzo[a]pyrene, and 0.0050 mg/kg for total mercury) in all the analyzed samples. Mean concentrations of lead and cadmium were 0.104 and 0.110 mg/kg, respectively. Of the non-dioxin-like polychlorinated biphenyls, PCB-153, PCB-180, and PCB-138 were the most abundant at all sampling sites (1a to 9a) at 0.25 mi (ca. 0.4 km) and at some sampling sites (1b, 2b, 3b, 5b and 7b) at 0.35 mi (ca. 0.56 km). Principal component analysis revealed that the concentrations of dioxin-like polychlorinated biphenyls were similar at the majority of sampling sites, and O8CDD and 2,3,7,8-T4CDF were the predominant dioxin congeners.

Influence of pig rennet on fatty acid composition, volatile molecule profile, texture and sensory properties of Pecorino di Farindola cheese

BACKGROUND

Pig rennet is traditionally used in Pecorino di Farindola cheese. In this study, different Pecorino cheeses obtained using calf, kid and pig rennets were compared in terms of fatty acids, volatile molecule profile, texture and sensory properties during ripening.

RESULTS

The rennet type influenced the fatty acid composition of cheeses, though palmitic, myristic and oleic acids were always predominant. The analysis of volatiles by SPME-GC/MS showed that Pecorino from calf rennet, at the end of ripening, was the least 'evolved' in terms of volatile profile. SPME-GC/MS analysis revealed that cheeses from calf rennet showed the slowest accumulation of free fatty acids over ripening time. Volatile data permitted the differentiation of cheese samples ripened from 30 to 180 days according to the rennet used. Texture analysis differentiated cheeses made with pig and calf rennet from those made with kid rennet, which were less hard and more elastic than the former. Also sensory analysis differentiated cheese samples on the basis of rennet type, and cheeses made with pig rennet showed the lowest elasticity, bitter taste and fruity and hay flavour intensities.

CONCLUSION

Pig rennet is fundamental to determine the quality parameters of Pecorino di Farindola cheese and could be used to impart peculiar quality features to ewe's milk cheeses.

Long-term impact of farm management and crops on soil microorganisms assessed by combined DGGE and PLFA analyses

In the present study, long-term organic and conventional managements were compared at the experimental field of Monsampolo del Tronto (Marche region, Italy) with the aim of investigating soil chemical fertility and microbial community structure. A polyphasic approach, combining soil fertility indicators with microbiological analyses (plate counts, PCR-denaturing gradient gel electrophoresis [DGGE] and phospholipid fatty acid analysis [PLFA]) was applied. Organic matter, N as well as some important macro and micronutrients (K, P, Mg, Mn, Cu, and Zn) for crop growth, were more available under organic management. Bacterial counts were higher in organic management. A significant influence of management system and management x crop interaction was observed for total mesophilic bacteria, nitrogen fixing bacteria and actinobacteria. Interestingly, cultivable fungi were not detected in all analyzed samples. PLFA biomass was higher in the organic and Gram positive bacteria dominated the microbial community in both systems. Even if fungal biomass was higher in organic management, fungal PCR-DGGE fingerprinting revealed that the two systems were very similar in terms of fungal species suggesting that 10 years were not enough to establish a new dynamic equilibrium among ecosystem components. A better knowledge of soil biota and in particular of fungal community structure will be useful for the development of sustainable management strategies.

Histamine poisoning and control measures in fish and fishery products

Histamine poisoning is one of the most common form of intoxication caused by the ingestion of fish and fishery products. Cooking, canning, or freezing cannot reduce the levels of histamine because this compound is heat stable. All humans are susceptible to histamine and its effects can be described as intolerance or intoxication depending on the severity of the symptoms. The amount of histamine in food, the individual sensitivity, and the detoxification activity in human organism represent the main factors affecting the toxicological response in consumers. Histamine is the only biogenic amine with regulatory limits set by European Legislation, up to a maximum of 200 mg/kg in fresh fish and 400 mg/kg in fishery products treated by enzyme maturation in brine.

Genetic diversity of FLO1 and FLO5 genes in wine flocculent Saccharomyces cerevisiae strains

Twenty-eight flocculent wine strains were tested for adhesion and flocculation phenotypic variability. Moreover, the expression patterns of the main genes involved in flocculation (FLO1, FLO5 and FLO8) were studied both in synthetic medium and in presence of ethanol stress. Molecular identification and typing were achieved by PCR-RFLP of the 5.8S ITS rRNA region and microsatellite PCR fingerprinting, respectively. All isolates belong to Saccharomyces cerevisiae species. The analysis of microsatellites highlighted the intraspecific genetic diversity of flocculent wine S. cerevisiae strains allowing obtaining strain-specific profiles. Moreover, strains were characterized on the basis of adhesive properties. A wide biodiversity was observed even if none of the tested strains were able to form biofilms (or 'mats'), or to adhere to polystyrene. Moreover, genetic diversity of FLO1 and FLO5 flocculating genes was determined by PCR. Genetic diversity was detected for both genes, but a relationship with the flocculation degree was not found. So, the expression patterns of FLO1, FLO5 and FLO8 genes was investigated in a synthetic medium and a relationship between the expression of FLO5 gene and the flocculation capacity was established. To study the expression of FLO1, FLO5 and FLO8 genes in floc formation and ethanol stress resistance qRT-PCR was carried out and also in this case strains with flocculent capacity showed higher levels of FLO5 gene expression. This study confirmed the diversity of flocculation phenotype and genotype in wine yeasts. Moreover, the importance of FLO5 gene in development of high flocculent characteristic of wine yeasts was highlighted. The obtained collection of S. cerevisiae flocculent wine strains could be useful to study the relationship between the genetic variation and flocculation phenotype in wine yeasts.

Biogeographical characterization of Saccharomyces cerevisiae wine yeast by molecular methods

Biogeography is the descriptive and explanatory study of spatial patterns and processes involved in the distribution of biodiversity. Without biogeography, it would be difficult to study the diversity of microorganisms because there would be no way to visualize patterns in variation. Saccharomyces cerevisiae, "the wine yeast," is the most important species involved in alcoholic fermentation, and in vineyard ecosystems, it follows the principle of "everything is everywhere." Agricultural practices such as farming (organic versus conventional) and floor management systems have selected different populations within this species that are phylogenetically distinct. In fact, recent ecological and geographic studies highlighted that unique strains are associated with particular grape varieties in specific geographical locations. These studies also highlighted that significant diversity and regional character, or 'terroir,' have been introduced into the winemaking process via this association. This diversity of wild strains preserves typicity, the high quality, and the unique flavor of wines. Recently, different molecular methods were developed to study population dynamics of S. cerevisiae strains in both vineyards and wineries. In this review, we will provide an update on the current molecular methods used to reveal the geographical distribution of S. cerevisiae wine yeast.

Yessotoxin determination in Mytilus galloprovincialis revealed by an in vitro functional assay

Yessotoxins (YTXs) are polycyclic ether compounds produced by phytoplanktonic dinoflagellates and accumulated in filter-feeding shellfish. Mouse bioassay is still the official method to detect these toxins, even if it is lacking of specificity and sensitivity. Moreover, there is growing resistance against the use of animal experiments. Many efforts have been made to determine YTXs with other methods. The detection of YTX using a functional assay allows its quantification with an automated and repetitive technique at concentrations in the range of the 1 mg of YTX equivalent/kg European regulatory limit. In this study, an in vitro functional assay based on YTX treatment of MCF-7 cells and resulting in the accumulation of a 100-kDa fragment of E-cadherin was developed on samples of Mytilus galloprovincialis collected from the Adriatic Sea, Italy, along the coasts of Abruzzo, Molise, and Emilia Romagna regions. The YTX concentrations ranged from 0.2 to 1.8 mg of YTX equivalent/kg. The occurrence of levels exceeding the above mentioned limit was observed only in samples of Emilia Romagna region. This last result could represent a risk for human health, but these shellfish were not intended to consumers, because they belonged to a preventive monitoring program.

Detection of yessotoxin by three different methods in Mytilus galloprovincialis of Adriatic Sea, Italy

Samples of Mytilus galloprovincialis collected from shellfish aquaculture plans located in the Adriatic Sea were analysed for yessotoxin (YTX) by three methods, in vivo (Mouse Bioassay, MBA), in vitro (functional assay) and chemical test (Liquid Chromatography-Mass Spectrometry, LC-MS/MS). As YTX coexists with other phycotoxins in shellfish, namely the diarrhoetic shellfish poisoning, okadaic acid, dinophysistoxins, pectenotoxins, and azaspirazids, the MBA is not completely satisfactory because it is difficult to identify which toxin causes the death of the mice. So, the two other techniques were proposed to detect and quantify YTX and its analogues in order to avoid this problem. The global results showed no difference among the three methods and the correlation between the functional assay and LC-MS/MS was positive (Spearman r=0.72). Both analytical methods demonstrated advantages; the functional assay is specific, very sensitive and correlates well with real toxicity, whereas LC-MS/MS is convenient because it allows the detection of YTX and some analogues which are currently included in the EU regulation. For this reason LC-MS/MS will become the official method starting 1st January 2015 (Regulation 15/2011/EU). Only four samples exceeded the current EU regulation limit of 1mg of YTX equivalent kg(-1). However, all samples belonged to a monitoring program and they were not suitable for consumers.

High content of biogenic amines in Pecorino cheeses

Pecorino refers to Italian cheeses made exclusively from raw or pasteurized ewes' milk, characterized by a high content of fat matter and it is mainly produced in the Middle and South of Italy by traditional procedures. The autochthonous microbiota plays an important role in the organoleptic traits of Pecorino cheese and it can influence biogenic amines (BA) content. The aim of this study was to characterize from microbiological and chemical point of view 12 randomly purchased commercial cheeses produced in Abruzzo region. Moreover, the BA content and the bacteria showing a decarboxylating activity were detected. For this purpose, a real-time quantitative PCR (qPCR) was applied to evaluate histamine and tyramine-producers. The samples were well differentiated for microbial groups composition, such as aerobic mesophilic bacteria, Enterobacteriaceae, coagulase-negative staphylococci, yeasts, enterococci, mesophilic and thermophilic lactobacilli. Pathogens such as Salmonella spp., Listeria monocytogenes and Escherichia coli O157:H7 were absent in all samples. In most samples the content of BA resulted to be high, with prevalence of histamine and tyramine. In particular, total BA content reached 5861 mg/kg in Pecorino di Fossa cheese. The qPCR method resulted to be very useful to understand the role of autochthonous Pecorino cheese microbiota on BA accumulation in many different products. In fact, since the ability of microorganisms to decarboxylate aminoacids is highly variable being in most cases strain-specific, the detection of bacteria possessing this activity is important to estimate the risk of BA cheese content.

Application of starter cultures to table olive fermentation: an overview on the experimental studies

Table olives are one of the oldest fermented foods and are considered as an important component of the Mediterranean diet, since their richness in monounsaturated fats (primarily oleic acid) and phenolic compounds may function as antioxidants in the human body; in the Western world they represent one of the most popular fermented vegetables but, despite its economic significance, table olive fermentation is still craft-based and empirical. In particular, such a type of fermentation results from the competitive activities among indigenous, contaminating microorganisms, the microbial balance depending on several intrinsic (pH, water activity, diffusion of nutrients from the drupe, and level of anti-microbial compounds) and extrinsic (temperature, oxygen availability, and salt concentration) factors. At present, to reduce the risk of spoilage and to achieve a more predictable process there is an increasing interest in developing starter cultures for table olives fermentation. Anyway, the application of starter cultures in the field of table olives is quite far from reaching the diffusion as it has in other sectors of food industry (e.g., dairy products and alcoholic beverages). This review focuses on experimental researches devoted to studying starter cultures for possible application to table olive fermentation both at artisan and industrial level.

Biogenic amines in raw and processed seafood

The presence of biogenic amines (BAs) in raw and processed seafood, associated with either time/temperature conditions or food technologies is discussed in the present paper from a safety and prevention point of view. In particular, storage temperature, handling practices, presence of microbial populations with decarboxylase activity and availability of free amino acids are considered the most important factors affecting the production of BAs in raw seafood. On the other hand, some food technological treatments such as salting, ripening, fermentation, or marination can increase the levels of BAs in processed seafood. The consumption of high amount of BAs, above all histamine, can result in food borne poisoning which is a worldwide problem. The European Regulation established as maximum limits for histamine, in fishery products from fish species associated with high histidine amounts, values ranging from 100 to 200 mg/kg, while for products which have undergone enzyme maturation treatment in brine, the aforementioned limits rise to 200 and 400 mg/kg. Preventive measures and emerging methods aiming at controlling the production of BAs are also reported for potential application in seafood industries.

Biogenic amines in italian pecorino cheese

The quality of distinctive artisanal cheeses is closely associated with the territory of production and its traditions. Pedoclimatic characteristics, genetic autochthonous variations, and anthropic components create an environment so specific that it would be extremely difficult to reproduce elsewhere. Pecorino cheese is included in this sector of the market and is widely diffused in Italy (∼62.000t of production in 2010). Pecorino is a common name given to indicate Italian cheeses made exclusively from pure ewes' milk characterized by a high content of fat matter and it is mainly produced in the middle and south of Italy by traditional procedures from raw or pasteurized milk. The microbiota plays a major role in the development of the organoleptic characteristics of the cheese but it can also be responsible for the accumulation of undesirable substances, such as biogenic amines (BA). Bacterial amino acid decarboxylase activity and BA content have to be investigated within the complex microbial community of raw milk cheese for different cheese technologies. The results emphasize the necessity of controlling the indigenous bacterial population responsible for high production of BA and the use of competitive adjunct cultures could be suggested. Several factors can contribute to the qualitative and quantitative profiles of BA's in Pecorino cheese such as environmental hygienic conditions, pH, salt concentration, water activity, fat content, pasteurization of milk, decarboxylase microorganisms, starter cultures, temperature and time of ripening, storage, part of the cheese (core, edge), and the presence of cofactor (pyridoxal phosphate, availability of aminases and deaminases). In fact physico-chemical parameters seem to favor biogenic amine-positive microbiota; both of these environmental factors can easily be modulated, in order to control growth of undesirable microorganisms. Generally, the total content of BA's in Pecorino cheeses can range from about 100-2400 mg/kg, with a prevalence of toxicologically important BA's, tyramine and histamine. The presence of BA is becoming increasingly important to consumers and cheese-maker alike, due to the potential threats of toxicity to humans and consequent trade implications.

Multistarter from organic viticulture for red wine Montepulciano d'Abruzzo production

In the last years the use of a multistarter fermentation process has been proposed to improve the organoleptic characteristics of wines. In the present study the fermentation performances and the interactions of mixed and sequential cultures of Hanseniasporauvarum, Candida zemplinina, and a strain of Saccharomycescerevisiae isolated from organic musts were investigated. To evaluate the oenological performances of the tested strains microvinifications in pasteurized red grape juice from Montepulciano d’Abruzzo cultivar were compared. The course of fermentation has been controlled through classical determinations (CO₂ evolution, ethanol, glycerol, pH, total titratable acidity, sugar content, free sulfur dioxide (SO₂), dry extract, sugars, organic acids, and volatile compounds). Moreover, the yeast population was determined by both culture-dependent and independent approaches. In particular, the pure culture of H. uvarum and C. zemplinina did not end the fermentation. On the contrary, when S. cerevisiae was added, fermentations were faster confirming that yeast interactions influence the fermentation kinetics. Moreover, C. zemplinina showed a good interaction with S. cerevisiae by increasing the fermentation kinetic in high gravity Montepulciano must, with low ethyl acetate and acetic acid production. This study confirmed that non-Saccharomyces yeasts play a crucial role also in organic wines and their activity could be modulated through the selection of appropriate strains that correctly interact with S. cerevisiae.