Loading...
21 results
Search Results
Now showing 1 - 10 of 21
- Production of volatile phenols by wine PediococciPublication . Couto, José A.; Campos, Francisco M.; Figueiredo, Ana R.; Hogg, Tim
- Activity of wine against campylobacter jejuniPublication . Carneiro, Anabela; Couto, José António; Mena, Cristina; Queiroz, Jorge; Hogg, TimThis study focuses on the activity of wine against the important food-borne pathogen Campylobacter jejuni. The kinetics of inactivation of two strains of C. jejuni (one food-borne and one clinical) were characterised in various scenarios of exposure to wine and wine components. Undiluted wine was found to rapidly inactivate C. jejuni (>6D inactivation within 30 s); further inactivation data were obtained from experiments performed in wine diluted with water (1:2 and 1:4). Experiments with isolated antimicrobial fractions of wine (ethanol and certain organic acids) suggest that these two components act synergistically, demonstrating an inactivation capacity similar to wine itself. The results indicate that the exposure of contaminated food to wine, as in marinade conditions, Significantly reduces the number of viable cells of C. jejuni. A model stomach, containing a food matrix and a synthetic gastric fluid, was used to infer the effect of wine against C. jejuni in a consumption-like scenario. Wine was found to potentiate the anti-Campylobacter effect of gastric fluid. The results strongly suggest that the ingestion of wine during a meal may greatly diminish the quantity of C. jejuni persisting further in the alimentary tract, thus lowering the risk of infection
- The influence of wine phenolic acids on the production of volatile phenols by lactic acid bacteriaPublication . Silva, Isa; Campos, Francisco M.; Hogg, Tim; Couto, José A.
- Factors influencing the production of volatile phenols by wine lactic acid bacteriaPublication . Silva, Isa; Campos, Francisco; Hogg, Tim; Couto, José AntónioThis work aimed to evaluate the effect of certain factors on the production of volatile phenols from the metabolism of p-coumaric acid by lactic acid bacteria (LAB) (Lactobacillus plantarum, L. collinoides and Pediococcus pentosaceus). The studied factors were: pH, L-malic acid concentration, glucose and fructose concentrations and aerobic/anaerobic conditions. It was found that, in the pH range of 3.5 to 4.5, the higher the pH the greater the production of volatile phenols. This behaviour is correlated with the effect of pH on bacterial growth. Increasing levels of L-malic acid in the medium diminished the production of 4-vinylphenol (4VP) and stimulated the production of 4-ethylphenol (4EP) by L. plantarum NCFB 1752 and L. collinoides ESB 99. The conversion of 4VP into 4EP by the activity of the vinylphenol reductase may be advantageous to the cells in the presence of L-malic acid, presumably due to the generation of NAD(+), a cofactor required by the malolactic enzyme. Relatively high levels of glucose (20 g/L) led to an almost exclusive production of 4VP by L. plantarum NCFB 1752, while at low concentrations (<= 5 g/L), 4EP is mainly or solely produced. Part of the glucose may be diverted to the production of mannitol as an alternative pathway to regenerate NAD+. This is corroborated by the experiments done with fructose, a compound that can be used as an electron acceptor by some bacteria becoming reduced to mannitol. In anaerobiosis, the reduction of 4VP into 4EP is clearly favoured, which is consistent with the need to increase the availability of NAD(+) in these conditions. This study shows that the amount and the ratio 4VP/4EP produced by LAB are greatly affected by certain environmental and medium composition factors. The behaviour of the bacteria seems to be driven by the intracellular NAD(+)/NADH balance.
- Young adults and wine consumption a qualitative application of the theory of planned behaviorPublication . Silva, Ana Patrícia; Figueiredo, Isabel; Hogg, Tim; Sottomayor, MiguelPurpose – The aim of this study is to identify perceptions, attitudes and behavior of young adults concerning wine consumption, using the “theory of planned behavior” as a theoretical framework. Design/methodology/approach – The aim of this study is to identify perceptions, attitudes and behavior of young adults concerning wine consumption, using the “theory of planned behavior” as a theoretical framework. Findings – The major findings are that attitudes and subjective norms are, apparently, the components with most influence on behavior of young people in relation to wine consumption. For the consumers group, attitudes seem to be the most crucial component, especially the “interest in alcohol”. They drink it in special occasions for sociability and to disinhibit. Regarding the non-consumers group, the main attitude is “dislike taste”. Also the subjective norms, are very present, especially parents, society, friends and publicity, in consumers group. The non-consumers have the perception of greater parental induction to not consume wine. No significant differences were found between gender or educational system. Research limitations/implications – Concerning the results, a limited, convenience sample, was employed and this is assumedly an exploratory study. Therefore the results cannot be considered to represent a broad section of the groups studied. Still sample related, only Portuguese young adults students were studied. Social implications – This research can contribute not only for the knowledge relating to Portugal as a wine consuming environment but also to the general area of attitudes and perceptions of young people towards moderate wine consumption. As today young adults, novice or potential wine consumers will be the next generation of wine consumers, it can be beneficial for wine marketers to focus on this target population aiming at exploring further their engagement with wine. Originality/value – This research has an originally approach to wine consumption by young adults once it focus and explore the non-problematic behavior of young adults about wine consumption. The results of this study can contribute to the development of targeted advertising and publicity of the wine industry, in order to promote moderate wine consumption among young adults.
- Volatile compounds contribution of Hanseniaspora guilliermondii and Hanseniaspora uvarum during red wine vinificationsPublication . Moreira, N.; Pina, C.; Mendes, F.; Couto, J.A.; Hogg, T.; Vasconcelos, I.This work aims to investigate the contribution of a selected non-Saccharomyces yeast species, Hanseniaspora guilliermondii, to higher alcohols, esters, fatty acids and heavy sulphur compounds composition of red wine. Red grape must vinifications of 100 l were performed and an inoculated fermentation with H. guilliermondii was compared to a spontaneous fermentation. The presence of apiculate yeasts was observed in both fermentations; however, Hanseniaspora uvarum was the only apiculate yeast isolated from the spontaneous fermentation. Apiculate yeasts dominated the fermentation until an ethanol concentration of 6% (v/v) was attained and remained in considerable high levels for an ethanol concentration of 12.5% (v/v). The grape must inoculated with H. guilliermondii led to the production of wine with higher concentrations of 1-propanol, 2-phenylethyl acetate and 3-(methylthio)propionic acid, and lower amounts of ethyl hexanoate, pentanoic acid, free fatty acids, 2-methyltetrahydrothiophen-3- one and acetic acid-3-(methylthio)propyl ester, than wine resulting from the spontaneous fermentation. The present study shows that the use of specific apiculate yeasts in grape must fermentations may lead to the production of wines with different chemical profiles, emphasising the importance of Hanseniaspora yeasts as mixed starter cultures with Saccharomyces cerevisiae, in winemaking.
- Influence of phenolic acids on growth and inactivation of Oenococcus oeni and Lactobacillus hilgardiiPublication . Campos, F.M.; Couto, J.A.; Hogg, TimAims: To determine the effect of several wine-associated, phenolic acids on the growth and viability of strains of Oenococcus oeni and Lactobacillus hilgardii. Methods and Results: Growth was monitored in ethanol-containing medium supplemented with varying concentrations of hydroxybenzoic acids (p-hydroxybenzoic, protocatechuic, gallic, vanillic and syringic acids) and hydroxycinnamic acids (p-coumaric, caffeic and ferulic acids). Progressive inactivation was monitored in ethanolcontaining phosphate buffer supplemented in a similar manner to the growth experiments. Hydroxycinnamic acids proved to be more inhibitory to the growth of O. oeni than hydroxybenzoic acids. On the other hand, some acids showed a beneficial effect on growth of Lact. hilgardii. p-Coumaric acid showed the strongest inhibitory effect on growth and survival of both bacteria. Conclusions: Most phenolic acids had a negative effect on growth of O. oeni, for Lact. hilgardii this effect was only noted for p-coumaric acid. Generally, O. oeni was more sensitive to phenolic acid inactivation than Lact. hilgardii. Significance and Impact of the Study: Eight wine-derived, phenolic acids were compared for their effects on wine lactic acid bacteria. Results indicate that phenolic acids have the capacity to influence growth and survival parameters. The differences found between phenolic compounds could be related to their different chemical structures.
- The antimicrobial effect of wine on Bacillus cereus in simulated gastro-intestinal conditionsPublication . Vaz, Miguel; Hogg, Tim; Couto, José AntónioThis study aimed to evaluate the antimicrobial activity of wine against Bacillus cereus vegetative cells and spores. The results clearly show that wine exerts a strong inactivation effect against vegetative cells of B. cereus. The red wine tested inactivated stationary phase cultures to undetectable numbers in less than 10 s. Thus, further inactivation assays were carried out with wine diluted with water (1:4 and 1:8). Diluted wine 1:4 caused a reduction of approximately 5 log cycles on viable cell counts in 20 s. On the other hand, B. cereus spores were found to be highly resistant to wine exposure. The influence of wine components (organic acids, ethanol and phenolic compounds) was investigated on vegetative cells. The wine organic acids tested exhibited a strong inactivation effect, and, when combined with ethanol, a slight synergistic effect was observed. The wine phenolic compounds assayed displayed no activity against the vegetative cells at the concentrations tested. At the simulated gastric conditions studied (in the presence of food), wine diminished considerably the number of B. cereus viable cells in addition to the effect of the synthetic gastric fluid. The behaviour of B. cereus spores under gastro-intestinal conditions was also evaluated. In a consumption-like scenario, the addition of wine led to lower total counts (vegetative cells þ spores) of B. cereus in the simulated intestine conditions, showing that wine inhibits the proliferation of the vegetative cells obtained from the germination of spores. This work provides evidence that consumption of wine during a meal may diminish the number of viable cells of B. cereus and reduces the impact of the germination of spores that may occur in the small intestine, thus lowering the risk of toxi-infection that may be caused by this pathogen.
- Functional or emotional? How Dutch and Portuguese conceptualise beer, wine and non-alcoholic beer consumptionPublication . Silva, Ana Patricia; Jager, Gerry; Bommel, Roelien van; Zyl, Hannelize van; Voss, Hans-Peter; Hogg, Tim; Pintado, M. E.; Graaf, Cees deNon-alcoholic beer (NAB) may be a healthier alternative to wine and beer consumption, however has little appeal to consumers. Conceptualisations, i.e. functional and emotional associations that consumers have with foods/beverages, were explored to understand how NAB consumption is perceived, and compared to beer and wine conceptualisations in the Netherlands and Portugal. A qualitative study was performed using a focus group approach with moderate consumers of both countries (n = 56). Content analysis followed by correspondence analysis were used to explore conceptualisations. This study showed similar conceptualisations of the beverages in both countries. NAB has a limited conceptual content, which is mostly functional as a substitute. Beer and wine are rich in both functional and emotional content. Wine is associated with positive low arousal emotional responses, such as calm and loving. Beer is associated with positive high arousal emotional responses, such as adventurous and energetic. NAB evokes neutral and negative emotional responses, such as rational, conscious, and disappointed. The difference in conceptualisations of NAB versus beer/wine might be why NAB is not adopted more widely as a substitute as it does not deliver a comparable emotional response to consumers. NAB should be treated as a beverage in its own right and it might be wise to avoid direct conceptual comparisons with beer. Should the image of NAB be communicated and understood with positive and high arousal associations, such as energetic and convivial, in communication and advertisements, a higher level of congruency between expectation and experience could be achieved.
- Changes in the composition of the lactic acid bacteria behavior and the diversity of oenococcus oeni isolated from red wines supplemented with selected grape phenolic compoundsPublication . Collombel, Ingrid; Campos, Francisco M.; Hogg, TimPhenolic compounds are important components of wine and are known to have an impact on the physiology of wine microbes. The influence of specific sub-sets of phenolic compounds on the growth and metabolism of lactic acid bacteria (LAB) and on the diversity of Oenococcus oeni in inoculated and non-inoculated red wines was investigated during malolactic fermentation (MLF) and subsequent storage. Representative O. oeni strains from wines treated with flavonols and trans-resveratrol were isolated and analyzed by pulsed-field gel electrophoresis of rare restriction enzyme digests (REA-PFGE). 28 days after MLF initiation, strains from all samples had entered the death phase, except those supplemented with trans-resveratrol. In the non-inoculated samples, the onset of lactic acid production was apparently delayed by all compounds tested, except for the flavan-3-ols. Increased levels of phenolics also delayed citrate consumption in inoculated samples. PFGE analysis revealed 22 genetic profiles, and some profiles were characteristics of specific samples. The commercial starter used in the inoculated wines did not dominate during MLF. The effect of the phenolics studied was dependent on the origin and concentration of each as well, as the fermentation stage and whether the wines were inoculated. The effect of flavonols and trans-resveratrol seemed to be strain-dependent, which could have implications on the final quality of wines.
- «
- 1 (current)
- 2
- 3
- »