Comparative study of the inhibitory effects of wine polyphenols on the growth of enological lactic acid bacteria

This paper reports a comparative study of the inhibitory potential of 18 phenolic compounds, including hydroxybenzoic acids and their derivatives, hydroxycinnamic acids, phenolic alcohols and other related compounds, stilbenes, flavan-3-ols and flavonols, on different lactic acid bacteria (LAB) strains of the species Oenococcus oeni, Lactobacillus hilgardii and Pediococcus pentosaceus isolated from wine. In general, flavonols and stilbenes showed the greatest inhibitory effects (lowest IC?? values) on the growth of the strains tested (0.160-0.854 for flavonols and 0.307-0.855 g/L for stilbenes). Hydroxycinnamic acids (IC?? > 0.470 g/L) and hydroxybenzoic acids and esters (IC?? >1 g/L) exhibited medium inhibitory effect, and phenolic alcohols (IC?? > 2 g/L) and flavanol-3-ols (negligible effect) showed the lowest effect on the growth of the LAB strains studied. In comparison to the antimicrobial additives used in winemaking, IC?? values of most phenolic compounds were higher than those of potassium metabisulphite for O. oeni strains (e.g., around 4-fold higher for quercetin than for potassium metabisulphite), but lower for L. hilgardii and P. pentosaceus strains (e.g., around 2-fold lower for quercetin). Lysozyme IC?? values were negligible for L. hilgardii and P. pentosaceus, and were higher than those corresponding to most of the phenolic compounds tested for O. oeni strains, indicating that lysozyme was less toxic for LAB than the phenolic compounds in wine. Scanning electron microscopy confirmed damage of the cell membrane integrity as a consequence of the incubation with antimicrobial agents. These results contribute to the understanding of the inhibitory action of wine phenolics on the progress of malolactic fermentation, and also to the development of new alternatives to the use of sulphites in enology.     

Effect of combined treatments of high-pressure and natural additives on carotenoid extractability and antioxidant activity of tomato puree (<Emphasis Type="Italic">Lycopersicum esculentum</Emphasis> Mill.)

High-pressure is a new food processing technology aimed at achieving consumer demands for fresher products with reduced microbiological levels. The objective of this work was to evaluate the effect of combined treatments of high-pressure and natural additives (citric acid and sodium chloride) on lutein, lycopene, lycopene epoxide, - and -carotene content, and vitamin A value, and on the in vitro antioxidant activity of tomato puree. The methods used to evaluate the antioxidant activity were the measurement of the DPPH· radical scavenging and the inhibition of lipid oxidation (linoleic acid/CuSO₄ system). The experimental design comprised a response surface methodology according to a central composite face-centred design. The variable ranges were 50–400 MPa, sodium chloride 0–0.8%, and citric acid 0–2%. Total carotenoid content showed the best extraction when pressure was increased up to 400 MPa without sodium chloride and citric acid. The effect of the moderately high-pressure treatment (under 200 MPa) on the structure of the cellular tomato matrix may lead to the different release of various carotenes on the basis of their chemical features and chromoplast location. Radical scavenging activity was higher in the aqueous extract than the organic extract of tomato puree. Significant correlation (P<0.05) was found between the total carotenoid content and the radical scavenging activity and inhibition of lipid oxidation by the organic extract of tomato puree. In conclusion, applying the highest range of pressures (without additives) increased the carotenoid extractability. Further human studies are needed to clarify the effect of high-pressure treatment on the bioavailability of tomato puree constituents.     

Combined effect of thymol and cymene to control the growth of<Emphasis Type="Italic"> Bacillus cereus</Emphasis> vegetative cells

The antibacterial action of thymol and cymene on two Bacillus cereus strains (INRA-AVTZ415 and INRA-AVZ421) was studied. Thymol and cymene alone showed higher antibacterial effect on the growth of B. cereus in BHI at 30 °C, both in lag and in exponential growth phases, with increasing added concentrations. However, the two strains tested showed different sensitivity to these natural compounds. When thymol and cymene were applied simultaneously, it resulted in a greater antibacterial effect than when the compounds were applied separately. The synergistic behaviour of both compounds was also shown for lag phase B. cereus INRA-AVZ421 cells in food substrates (carrot juice, chicken soup and pumpkin cream) at 30 °C, though a clear food-related effect was observed. This study indicates the potential use of thymol and cymene applied simultaneously for preservation of minimally processed foods.     

Carotenoid content and antioxidant capacity of Mediterranean vegetable soup (gazpacho) treated by high-pressure/temperature during refrigerated storage

High-pressure (HP) technology is an alternative to heat preservation methods for foods; therefore, it is essential to assess the impact of this technology on bioactive compounds and their properties. Carotenoids and antioxidant activity were measured in Mediterranean vegetable soup, called gazpacho subjected to HP/temperature treatment. The stability of carotenoids and the effect on antioxidant activity was studied during 40 days of refrigerated storage at 4°C. Two treatments that combine HP with temperature were assayed: T0, freshly made vegetable soup (untreated), T1, 150 MPa/60°C/15 min, T2, 350 MPa/60°C/15 min. Fresh and treated samples were kept refrigerated (4°C) for 40 days. After application of HP and during the refrigeration period, the qualitative and quantitative determination of provitamin A carotenoids (β- and γ-carotene), lycopene and the xanthophyll lutein was achieved. In addition, the radical scavenging activity of vegetable soups was assessed. T1 HP treatment (T1, 150 MPa/60°C/15 min) preserved the carotenoid content in vegetable soups better than T2 HP treatment. Moreover, T1 HP treatment retained the antioxidant activity during storage better than T2 HP treatment.     

Insights into the metabolism and microbial biotransformation of dietary flavan-3-ols and the bioactivity of their metabolites

Flavan-3-ols, occurring in monomeric, as well as in oligomeric and polymeric forms (also known as condensed tannins or proanthocyanidins), are among the most abundant and bioactive dietary polyphenols, but their in vivo health effects in humans may be limited because of their recognition as xenobiotics. Bioavailability of flavan-3-ols is largely influenced by their degree of polymerization; while monomers are readily absorbed in the small intestine, oligomers and polymers need to be biotransformed by the colonic microbiota before absorption. Therefore, phenolic metabolites, rather than the original high molecular weight compounds found in foods, may be responsible for the health effects derived from flavan-3-ol consumption. Flavan-3-ol phenolic metabolites differ in structure, amount and excretion site. Phase II or tissular metabolites derived from the small intestine and hepatic metabolism are presented as conjugated derivatives (glucuronic acid or sulfate esters, methyl ether, or their combined forms) of monomeric flavan-3-ols and are preferentially eliminated in the bile, whereas microbial metabolites are rather simple conjugated lactones and phenolic acids that are largely excreted in urine. Although the colon is seen as an important organ for the metabolism of flavan-3-ols, the microbial catabolic pathways of these compounds are still under consideration, partly due to the lack of identification of bacteria with such capacity. Studies performed with synthesized or isolated phase II conjugated metabolites have revealed that they could have an effect beyond their antioxidant properties, by interacting with signalling pathways implicated in important processes involved in the development of diseases, among other bioactivities. However, the biological properties of microbe-derived metabolites in their actual conjugated forms remain largely unknown. Currently, there is an increasing interest in their effects on intestinal infections, inflammatory intestinal diseases and overall gut health. The present review will give an insight into the metabolism and microbial biotransformation of flavan-3-ols, including tentative catabolic pathways and aspects related to the identification of bacteria with the ability to catabolize these kinds of polyphenols. Also, the in vitro bioactivities of phase II and microbial phenolic metabolites will be covered in detail.     

Variability in the intercomparison of food carotenoid content data: A user's point of view

The availability of reliable information on food composition is essential both for the evaluation of diet and for nutritional research to relate diet to health or disease. In this article, we compare the total and individual carotenoid contents and the retinol equivalents in fruits and vegetables reported in several food composition tables and HPLC studies. The impact of the variability in carotenoid intake was evaluated on the basis of Spanish National Consumption Statistics and on the values for a standard diet. We identify, from a user's point of view, errors concerning identification of the items and the terms used to refer to the compounds. Food composition tables overestimate (by 2 to 48%) the retinol equivalent intake, whereas they underestimate (by 30 to 50%) the total carotenoid intake according to HPLC data. We study the effect of these main sources of error, their impact on dietary assessment and on the classification of relevant contributors, and the possible consequences with respect to proper diet in terms of nutritional assessment and epidemiological studies. Given the different dietary habits among populations and the fact that certain items may be over‐ or underestimated in databases, the use of a single database may be misleading as to the rate of carotenoid consumption and the “true” nutrient intake in a given population, thus weakening the reliability of the study and resulting in erroneous conclusions.     

Evolution of polyphenols in red wines from Vitis vinifera L. during aging in the bottle

The evolution of non-anthocyanin phenolic compounds (as measured by high-performance liquid chromatography) in young red wines from Vitis vinifera L. cv Tempranillo, Graciano and Cabernet Sauvignon (vintage 2000) from Navarra (Spain) was studied during 26 months of aging in the bottle. Hydroxybenzoic acids and derivatives (gallic, protocatechuic, vanillic and syringic acids, and methyl and ethyl gallates), hydroxycinnamic acids and derivatives (trans-caftaric, cutaric, caffeic and p-coumaric acids, and hexose esters of trans-p-coumaric acid), stilbenes (trans- and cis-resveratrol-3-O-glucosides, and trans- and cis-resveratrol), phenolic alcohols and other related compounds (tyrosol and tryptophol), flavanols [procyanidins B1 and B2, (+)-catechin and (–)-epicatechin] and flavonols (myricetin-3-O-glucoside, quercetin-3-O-galactoside and quercetin-3-O-glucuronide, kaempherol-3-O-glucoside, myricetin and quercetin) presented different evolution patterns during aging, in some cases also being different depending on the grape variety studied. The changes that occurred during aging in the bottle were the decrease of the concentration of trans-caftaric and cutaric acids accompanied by an increase of trans-caffeic acid and, especially of trans-p-coumaric acid. The greater increase of trans-p-coumaric acid was also associated with the disappearance of p-coumaroyl-acylated anthocyanins that occurs during aging in the bottle. Flavanols registered a major decrease, with the disappearance rate being greater for the dimeric procyanidins than for the monomeric flavanols, and the order of the disappearance rate by variety was as follows: Tempranillo相似文献   

Differentiation of raspberry varieties according to anthocyanin composition

 Four Spanish raspberry (Rubus idaeus L.) cultivars, Autumn Bliss, Heritage, Rubi, and Ceva, were studied in order to determine, qualitatively and quantitatively, both anthocyanins and vitamin C composition, owing to their significance as dietary compounds with antioxidant activity and also to the relation with color quality. Raspberry anthocyanin composition, determined by HPLC and GC-MS, was characteristic to each cultivar. The higher anthocyanin content expressed as cyanidin-3-glucoside was found in the late cultivars, Rubi (96.08 mg/100 g f.w.) and Ceva (122.88 mg/100 g f.w.). Three cultivars showed cyanidin-3-sophoroside (63.86–21.91 mg/100 g f.w.) and cyanidin-3-glucoside (25.12–14.00 mg/100 g f.w.) as the major pigments, while Autumn Bliss had a similar relative amount of cyanidin derivatives, cyanidin-3-rutinoside being the pigment in major concentration (10.53 mg/100 g f.w.). The vitamin C contents were determined by HPLC. The Rubi cultivar showed the highest amount of vitamin C (31.14 mg/100 g f.w.). The organic acids were determined by HPLC as fruit constituents related to color quality. Citric acid was the main non-volatile organic acid (90%) in all raspberry cultivars and the Rubi cultivar showed the highest total non-volatile organic acids content (2003 mg/100 g f.w.). Hunter color CIE values were also determined, showing that Rubi was the reddest raspberry cultivar. Received: 28 May 1998     

Recovery,fractionation and study of oils from a lignite

Oils from a lignite (Teruel, Spain) were studied. They were obtained by catalytic depolymerization, by reacting an aromatic substrate (tetralin), Lewis acid catalyst (BF₃) and the lignite (oil A) or asphaltenes (oil B) at atmospheric pressure and temperatures <220 °C. The A and B oils were fractionated on an alumina-silica gel dual column into their saturated, mono- and diaromatic, polyaromatic and polar components by elution with hexane, hexane-benzene, benzene and methanol-diethyl ether-benzene respectively. The elemental analysis, average molecular weight, i.r. and ¹H n.m.r. spectroscopy and aromaticity data of these subfractions were studied.     

Total Oxidation of Naphthalene Using Mesoporous CeO2 Catalysts Synthesized by Nanocasting from Two Dimensional SBA-15 and Three Dimensional KIT-6 and MCM-48 Silica Templates

Ceria catalysts have been prepared by a nanocasting procedure using SBA-15, MCM-48 and KIT-6 silica-based templates, and investigated for the total oxidation of naphthalene. In all cases cubic fluorite CeO₂ was prepared, and the structure of the template was replicated when SBA-15 and MCM-48 were used. The KIT-6 template was not replicated by the nanocasting synthesis, but in all cases mesoporous CeO2 was obtained with high surface areas (91–190 m² g^?1). All of the catalysts demonstrated high activity for naphthalene oxidation to CO₂, and the most active was the catalyst prepared from the KIT-6 template. The high activity was attributed to the small crystallite size of the CeO₂, combined with high surface area and the highly accessible catalyst surface.