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    ABSTRACT: In this study, the survival of the functional yeast Kluyveromyces marxianus B0399 in an industrially produced fermented milk was evaluated. In particular, the yeast viability was assessed throughout the entire shelf-life of the product (30 d) to ensure the presence of the effective yeast dose (20 million viable cells for each serving of 125 g) while avoiding, by sorbic acid addition, yeast growth, which could affect product quality and stability. To find the best combination of yeast and sorbic acid concentration, 13 different combinations were tested, and then 2 of them were chosen for industrial production. In production at lower concentrations (30 million viable cells, 150 mg/kg of sorbic acid) the effective dose was maintained only at 4 and 6°C, whereas at higher dosages (70 million viable cells, 250 mg/kg of sorbic acid) the effect of temperature was less evident. In all the trials, the concentration of sorbic acid was not affected by microbial metabolism and remained stable throughout the entire shelf-life.
    No preview · Article · Nov 2015 · Journal of Dairy Science
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    ABSTRACT: Aims: The aim of this work was to study the responses of Saccharomyces bayanus cells exposed to sub-lethal high-pressure homogenization (HPH) and determine whether the plasmatic membrane can sense HPH in the presence, or absence, of exogenous unsaturated fatty acids (UFAs) in the growth medium. Methods and results: High-pressure homogenization damaged and caused the collapse of cell walls and membranes of a portion of cells; however, HPH did not significantly affect S. bayanus cell viability (less than 0.3 Log CFU ml(-1)). HPH strongly affected the membrane fatty acid (FA) composition by increasing the percentage of total UFA when compared with saturated fatty acids. The gene expression showed that the transcription of OLE1, ERG3, and ERG11 increased after HPH. The presence of exogenous UFA abolished HPH-induced effects on the OLE1 and ERG3 genes, increased the percentage of membrane lipids and decreased the expression of OLE1 and ERG3 within 30 min of treatment. Conclusion: The results suggest a key role for UFA in the microbial cell response to sub-lethal stress. In addition, these data provide insight into the molecular basis of the response of S. bayanus to this innovative technology. Significance and impact of the study: Elucidation of the mechanism of action for sub-lethal HPH will enable the utilization of this technology to modulate the starter performance at the industrial scale.
    Full-text · Article · Oct 2015 · Frontiers in Microbiology
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    ABSTRACT: The purpose of this research was to evaluate the ability of four strains of Saccharomyces cerevisiae endowed with β-glucosidase activity to improve the Trebbiano wine aroma profiles and quality. In particular, the strain effects on fermentation kinetics, sugar and acid concentrations, volatile aroma compound profiles, colour, and catechins parameters were evaluated. The four strains of S. cerevisiae were tested in comparison with a commercial strain. The results showed that the four wild strains had high fermentation rates associated with an efficient conversion of grape sugars to alcohol. In addition, each strain imparted specific features to the wine. In fact, significant differences in relation to the inoculated strain were observed mainly in residual sugar content, succinic and tartaric acid concentrations, and volatile aroma compound profiles as esters, higher alcohols, and terpenes. In particular, the products obtained with S. cerevisiae BV12 and BV14 were characterized by lowest residual sugar contents. Moreover, BV14 and AS15 produced the wines with the highest concentrations of succinic and tartaric acids. Also, the wine obtained with the strains AS11 and AS15 showed high concentrations of monoterpenes and particularly linalool and geraniol having a strong sensorial impact. Furthermore, the wine obtained with the strain AS11 showed a minor decrease in colour intensity, probably due to the highest content of total SO2. These results outlined the importance of the strain selection, tailor made based on the wine feature and the wine making process adopted. © 2014, Springer-Verlag Berlin Heidelberg and the University of Milan.
    No preview · Article · Sep 2015 · Annals of Microbiology
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    ABSTRACT: BACKGROUND The aim of this work was to study the physico-chemical and microbiological parameters of 10 Italian fermented sausages industrially produced 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 analyzed with some statistical explorative tools: ANOVA, principal component analysis (PCA) and linear discriminant analysis (LDA).RESULTSSignificant differences in relation to the sausage size were found regarding microbial populations (regarding in particular enterobacteria and staphylococci). The pH was higher in the small sausages, and consequently the presence of lactate and acetate was higher in the bigger one. Also the biogenic amine content (particularly tyramine, cadaverine and putrescine) was influenced by the size.CONCLUSIONS In spite of the extreme variability of the sausage types at the end of ripening, this work evidenced that it was possible to find a strict relationship between sausages diameter and some essential physico-chemical parameters. Thus, the cross-sectional size of the product is an essential parameter, which can drive the biochemical processes during ripening, not only by affecting the kinetics of water losses, but also by influencing the microbiota enzymatic activity.
    Full-text · Article · Sep 2015 · Journal of the Science of Food and Agriculture
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    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.
    No preview · Article · Aug 2015 · Food Chemistry
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    ABSTRACT: Thirty-nine strains of Kluyveromyces marxianus from Pecorino di Farindola cheese in comparison with 3 strains from Parmigiano Reggiano cheese, 1 from fermented milk, 3 from cow whey and two type strains K. marxianus CBS 834(T) and Kluyveromyces lactis CBS 683(T) were tested for genetic and metabolic characteristics. Intraspecific diversity of chromosome arrangements was evaluated by pulsed field gel electrophoresis (PFGE) analysis. Among K. marxianus strains chromosome polymorphisms were evident with 11 patterns that differed in size and number of the chromosomal bands. The number of the bands varied from 4 to 7 with sizes ranging from about 1.0 to 2.7Mb. Twelve strains were selected for determining their growth capacity and volatile compound production in two wheys (raw cheese whey and ricotta cheese whey) under limited oxygen availability. The growth kinetics highlighted four different biotypes and the influence of whey composition on K. marxianus development. The main volatile compounds detected after the growth were alcohols, acids, esters, ketones and aldehydes. Ethanol was the most abundant in both wheys. Aldehydes and other minor compounds were produced only when the strains were inoculated in ricotta cheese whey, while esters, butanoic, decanoic and octanoic acids were qualitatively and quantitatively more present in raw cheese whey. This study highlights a great genetic and metabolic biodiversity within Pecorino di Farindola K. marxianus strains and it could be exploited to improve the knowledge of this yeast for biotechnological uses. Copyright © 2015 Elsevier B.V. All rights reserved.
    Full-text · Article · Aug 2015 · International journal of food microbiology
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    ABSTRACT: Outbreaks of food-borne disease associated with the consumption of fresh and minimally processed fruits and vegetables have increased dramatically over the last few years. Traditional chemical sanitizers are unable to completely eradicate or kill the microorganisms on fresh produce. These conditions have stimulated research to alternative methods for increasing food safety. The use of protective cultures, particularly lactic acid bacteria (LAB), has been proposed for minimally processed products. However, the application of bioprotective cultures has been limited at the industrial level. From this perspective, the main aims of this study were to select LAB from minimally processed fruits and vegetables to be used as biocontrol agents and then to evaluate the effects of the selected strains, alone or in combination with natural antimicrobials (2-(E)-hexenal/hexanal, 2-(E)-hexenal/citral for apples and thyme for lamb's lettuce), on the shelf-life and safety characteristics of minimally processed apples and lamb's lettuce. The results indicated that applying the Lactobacillus plantarum strains CIT3 and V7B3 to apples and lettuce, respectively, increased both the safety and shelf-life. Moreover, combining the selected strains with natural antimicrobials produced a further increase in the shelf-life of these products without detrimental effects on the organoleptic qualities.
    No preview · Article · May 2015 · Food Microbiology
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    ABSTRACT: The use of pig rennet is very ancient and in Italy is only applied in the manufacture of Pecorino di Farindola cheese. In order to evaluate the key role of this rennet in the establishment of peculiar features of Pecorino di Farindola, cheeses made from raw ewes' milk using calf (A) and kid (B) rennets were compared to those produced with pig (C) rennet. The use of pig rennet for Pecorino di Farindola cheese making confers physico-chemical and proteolytic characteristics that differentiate it from cheeses produced with other coagulants. However, no microbiological differences were observed. Chesses made with pig and kid rennets were characterised by higher proteolysis after 7days of ripening. The content of isovaleric and propionic acids at the end of ripening was correlated with the presence of propionibacteria. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Full-text · Article · May 2015 · Food Chemistry
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    ABSTRACT: In this study the thermal resistance of seven strains of staphylococci was studied. Three of them (two Staphylococcus epidermidis and one Staphylococcus lugdunensis) were isolated from pasteurized tofu, while one Staphylococcus aureus from fermented sausages. Also the corresponding type strains were tested. Their heat resistance was assessed at 80 °C also in relation to different growth conditions (high NaCl concentrations and low pH). Moreover, the effect of two terpenes (carvacrol and citral) on their survival during thermal treatment was assessed. All the strains were able to survive a 20 min thermal treatment and showed a similar behavior, i.e. an inactivation of about 6 log units in the first 2–4 min of treatment, followed by constant survivor counts (2–4 log CFU/ml). The pre-culture of staphylococci under stressing conditions (high NaCl concentration and low pH) increased the susceptibility to thermal treatment in three strains isolated from food matrices. The addition of carvacrol and citral during thermal treatment influenced the number of survived cells at the end of the treatment. This new insight in the thermal resistance of staphylococci needs to be better investigated, in order to study proper strategies to control their occurrence and behavior in real food systems.
    No preview · Article · Apr 2015 · Food Control
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    ABSTRACT: The probiotic Lactobacillus paracasei A13, treated at 50 MPa sub-lethal high pressure homogenisation (HPH), was used as adjunct for producing Caciotta cheese. The cell HPH treatment was used because it has been proven to increase the in vitro strain functionality. The starters and Lb. paracasei A13 viability, the cheese hydrolytic patterns and organoleptic profiles were monitored. After cheesemaking and during ripening, the Lb. paracasei A13 gastric acid resistance in cheese and the ability of the cheese, containing HPH-treated or untreated cells, to modulate the gut mucosal immune system in mice were evaluated. Traditional Caciotta was used as controls. The HPH-treated probiotic strain maintained high viability for 14 days whilst the physico-chemical analyses on Caciotta cheese containing HPH-treated cells showed a faster ripening, compared to other cheeses. For functional properties, the 50 MPa treatment increased the Lb. paracasei gastric resistance in Caciotta, maintaining high strain viability, but IL-10 producing capacity was lost by HPH-treatment whilst IgA production was not modified.
    No preview · Article · Mar 2015 · Journal of Functional Foods
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    ABSTRACT: BACKGROUND Salama da sugo is a fermented sausage from the Ferrara tradition (Italy, Emilia-Romagna region), subjected to a long ripening period (4-6 months) and characterised by a high content of wine and spices in the mixture. It can be consumed after cooking and it is served with its sugo, i.e. the liquid extracted by cooking process. The aim of this work was to set up a method for the sensory profile of Salama da sugo as a request for Protected Geographical Indication (PGI) has been made to the European Commission.RESULTSA system of sample preparation that provides for the precooking in an autoclave and cooking in boiling water was set up. A specific sheet for sensory evaluation of Salama da sugo has been created and reports 23 descriptors identified during the lexicon development. The differences in sensory profile of four samples were evaluated and principal component analysis highlighted the more discriminant parameters, i.e. odour intensity, wine odour, spicy aroma, fat/lean connection, sweet, bitter, juiciness, chewiness and pricking.CONCLUSIONS The proposed method allows the standardisation of sensory profiling of Salama da sugo, and is also to verify compliance with the specification PGI. © 2014 Society of Chemical Industry
    No preview · Article · Mar 2015 · Journal of the Science of Food and Agriculture
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    ABSTRACT: Minimally processed fruits and vegetables are one of the major growing sector in food industry. Although important for their nutritional values and convenience, their composition and physicochemical properties affect their microbiological shelf life and overall quality. On the other hand, processing steps as washing, if well performed, can partially reduce the occurring microflora and the use of sanitizers are perceived negatively by the consumers. For this reasons, researchers have proposed some alternatives to the use of traditional sanitizers, such as essential oils which are complex mixtures of volatile compounds, characterized by a strong sensorial impact and produced by many plants as secondary metabolites. In this perspective, this review discusses the growing importance of minimally processed fruits and vegetables and the potential application of essential oils and their components as natural antimicrobial. Finally, the mechanisms of action of these molecules have being reviewed taking into account their use in food systems.
    No preview · Article · Mar 2015 · Trends in Food Science & Technology
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    ABSTRACT: Plant essential oils (EOs) and their components, generally recognized as safe and endowed with a wide antimicrobial activity, have been investigated in this paper as natural sanitizer alternatives to chlorine to control spoilage bacteria and naturally occurring pathogens associated with minimally processed vegetables. From this perspective, the efficacy of oregano and thyme EOs and carvacrol was evaluated in comparison with chlorine for lamb’s lettuce decontamination. Their effects were evaluated on mesophilic aerobic bacteria, yeasts, LAB, color parameters and volatile molecule profiles demonstrating the same efficacy of chlorine. A further optimization of the process highlighted that thyme and oregano EOs controlled minimally processed lamb’s lettuce spoilage microflora without negatively affecting the quality and sensory properties of the products. These results demonstrate the potential of washing treatments based on natural antimicrobials, as alternatives to chlorine for the sanitization of minimally processed vegetables.
    No preview · Article · Feb 2015 · Postharvest Biology and Technology
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    ABSTRACT: The aim of this work was to investigate the modifications of cell membrane fatty acid composition and volatile molecule profiles of Listeria monocytogenes, Salmonella enteritidis, Escherichia coli, during growth in the presence of different sub-lethal concentrations of thyme and oregano essential oils as well as carvacrol, thymol, trans-2-hexenal and citral. The results evidenced that the tested molecules induced noticeable modifications of membrane fatty acid profiles and volatile compounds produced during the growth. Although specific differences in relation to the species considered were identified, the tested compounds induced a marked increase of some membrane associated fatty acids, particularly unsaturated fatty acids, trans-isomers, and specific released free fatty acids. These findings can contribute to the comprehension of the stress response mechanisms used by different pathogenic microorganisms often involved in food-borne diseases in relation to the exposure to sub-lethal concentrations of natural antimicrobials. Copyright © 2015 Elsevier Ltd. All rights reserved.
    No preview · Article · Feb 2015 · Food Chemistry
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    ABSTRACT: The antimicrobial activity of essential oils (EOs) from spices and medicinal plants or their constituents has gained increasing interest. However, studies on their use in combination with other antimicrobials or technologies are still scarce. In this paper, the survival of Salmonella enteritidis exposed to a combined effect of four EOs (from Xylopia aethiopica, Curcuma longa, Zanthoxylum leprieurii and Zanthoxylum xanthoxyloides) and mild heat treatments (55° and 60°C) were assessed. Salmonella enteritidis demonstrated a biphasic inactivation curve at 55°C in the absence of EOs, while in the presence of EOs the Weibull model was used. The combination of temperature and EOs reduced the treatment time needed to inactivate 7 log cfu/mL of S. enteritidis: this reduction ranged, with respect to the control, from 92.6% to 96.4% when the treatment was performed at 55°C, and from 20.5% to 27. 5% at 60°C. The efficiency of the interaction of the combination of EOs and mild thermal treatment is related to increased vapor pressure of EO constituents, which became more soluble in the membrane of stressed cells.
    No preview · Article · Jan 2015 · Journal of Essential Oil Research
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    ABSTRACT: Pandoro is a traditional Italian sweet-leavened baked product, usually consumed at Christmas. It is manufactured according to specific procedures and preparation starts from a sourdough called ‘‘madre’’ (mother sponge) continuously refreshed. This sourdough is the result of a complex microbial association including yeasts and lactic acid bacteria (LAB) and its use can improve sensory quality and shelf-life of the resulting products. The aim of this work was to evaluate the effect of the use of two different sourdoughs matured at different temperature (13 and 19 °C) on some metabolites, which can affect the organoleptic characteristics of Pandoro. Different samples, taken throughout the 19 h of process, were analysed for the determination of yeast and LAB counts, pH, aw, carbohydrates, organic acids content and volatile profile. The results showed that, at the end of fermentation process, the sourdough propagated at 19 °C reached lower pH values than that at 13 °C. This was probably due to higher LAB counts (1 log unit higher), resulting also in higher lactic acid concentration and faster sugars depletion. On the contrary, temperature of dough during maturation did not affected yeast concentrations. Different production processes strongly affected also the volatile profile, both of sourdough at the end of fermentation and of the final products.
    No preview · Article · Nov 2014 · Lebensmittel-Wissenschaft und-Technologie
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    ABSTRACT: The aim of this study was to evaluate the competitive effects of three bacteriocin producing strains of Lactococcus lactis subsp. lactis against two aminobiogenic lactic acid bacteria, i.e. the tyramine producing strain Enterococcus faecalis EF37 and the histamine producing strain Streptococcus thermophilus PRI60, inoculated at different initial concentrations (from 2 to 6logcfu/ml). The results showed that the three L. lactis subsp. lactis strains were able to produce bacteriocins: in particular, L. lactis subsp. lactis VR84 and EG46 produced, respectively, nisin Z and lacticin 481, while for the strains CG27 the bacteriocin has not been yet identified, even if its peptidic nature has been demonstrated. The co-culture of E. faecalis EF37 in combination with lactococci significantly reduced the growth potential of this aminobiogenic strain, both in terms of growth rate and maximum cell concentration, depending on the initial inoculum level of E. faecalis. Tyramine accumulation was strongly reduced when E. faecalis EF37 was inoculated at 2logcfu/ml and, to a lesser extent, at 3logcfu/ml, as a result of a lower cell load of the aminobiogenic strain. All the lactococci were more efficient in inhibiting streptococci in comparison with E. faecalis EF37; in particular, L. lactis subsp. lactis VR84 induced the death of S. thermophilus PRI60 and allowed the detection of histamine traces only at higher streptococci inoculum levels (5-6logcfu/ml). The other two lactococcal strains did not show a lethal action against S. thermophilus PRI60, but were able to reduce its growth extent and histamine accumulation, even if L. lactis subsp. lactis EG46 was less effective when the initial streptococci concentration was 5 and 6logcfu/ml. This preliminary study has clarified some aspects regarding the ratio between bacteriocinogenic strains and aminobiogenic strains with respect to the possibility to accumulate BA and has also showed that different bacteriocins can have different effects on BA production on the same strain. This knowledge is essentially aimed to use bacteriocinogenic lactococci as a predictable strategy against aminobiogenic bacteria present in cheese or other fermented foods.
    No preview · Article · Aug 2014 · International Journal of Food Microbiology
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    ABSTRACT: First aim of this research was to characterize oregano (Origanum vulgare) essential oil and the characterization of its minimum inhibitory concentration against the pathogenic species, Listeria monocytogenes and Escherichia coli. Moreover, the oregano essential oil antimicrobial activity was tested against these pathogenic species, inoculated onto wood and stainless steel surface. The GC/MS profile of oregano essential oil revealed the presence of 34 compounds, principally terpinolene, carvacrol and p-cymene accounting for about 70% of the total area of the identified molecules. Oregano essential oil showed higher antimicrobial activity against L. monocytogenes in comparison with E. coli. In fact, the L. monocytogenes minimum inhibitory concentration ranged between 125 and 200 mg/L while those for E. coli ranged between 250 and 350 mg/L. Regarding the decontamination efficacy, the washing of the two surfaces with oregano fastened the viability decrease of both the inoculated microorganisms over time. This phenomenon was more pronounced for wood as compared to steel. The data obtained suggests the great potential of this essential oil to be employed, as alternative to traditional chemicals, and as sanitizing strategy for surfaces.
    No preview · Article · Jul 2014 · African journal of microbiology research
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    ABSTRACT: Salami are typical European dry fermented sausages manufactured mainly with pork meats. Water loss is a crucial aspect of industrial ripening process because it is responsible for the lowering of water activity, which determines limitations to successive conservation. This paper describes two parametric numerical models developed to study the moisture diffusion physics, during ripening and storage in package. Mass transfer equations inside the sausage volume were numerically solved using a finite element technique. A first model describes diffusion phenomena occurring inside the salami and the exchange phenomena involving the surface of the product and the industrial environment, while a second one describes also the evaporation and condensation phenomena occurring between the salami surface and the atmosphere inside the packaging. The models were experimentally validated showing a good agreement with observed data. The numerical models allowed to study the water transfer inside of dry fermented sausages with a detail unreachable by any experimental technique. In addition the models could be used to find the best conditions for ripening, packaging and distribution.
    No preview · Article · Jul 2014 · Journal of Food Engineering
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    ABSTRACT: a b s t r a c t Minimally processed fruit are susceptible to microbial proliferation and to a fast loss of sensory quality. In this experimental work, in order to increase shelf-life and quality parameters (texture and colour) maintenance of sliced apples (Malus communis, var. Golden delicious), the use of natural antimicrobials was proposed as alternative to the traditional sanitization methods. Citron EO, hexanal, 2-(E)-hexenal, citral and carvacrol, alone or in combination, were employed. As control, apples washed only with 0.5% of ascorbic and 1% of citric acid were used. The apples were dipped with traditional or natural antimicrobial solutions according to a defined protocol. After the treatment, apples were packaged in active modified atmosphere (7% O 2 and 0% CO 2) , into medium permeability bags. The products were stored at 6 C and, immediately after washing and during storage, the yeast cell loads were monitored until the spoilage threshold (6 log CFU/g). In addition, the volatile profiles, electronic nose analyses, colour and texture analyses were monitored during the storage. In all the samples the spoilage yeast threshold was not attained within the 35 days of storage independently on the substance or mixture of substances sup-plemented. Samples treated with the combinations citral/2-(E)-hexenal and hexanal/2-(E)-hexenal showed a good retention of colour parameter during storage. Among investigated samples, hexanal/2-(E)-hexenal treatment promoted the best retention of firmness throughout 35 days of storage. These results evidence the potentiality of dipping treatment based on these natural antimicrobials to strongly prolong the shelf-life of fresh-cut apples.
    Full-text · Article · Jun 2014 · Food Control

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