Evolution of esters in aged Chardonnay wines obtained with different vinification methods

BACKGROUND: During wine ageing on lees yeast lysis takes place and some enzymes from the yeast cells, such as esterases, may be released. These enzymes might determine ester synthesis and could be also involved in their breakdown. In this study, the evolution of esters in Chardonnay wine fermented in stainless steel tanks and aged in bottles (conventional vinification) was compared with the evolution of esters in the same wine fermented and aged in barrel on lees. In this way, it was hoped to determine the influence of distinct methods of vinification on the evolution of esters in Chardonnay wine. RESULTS: The concentration of acetate esters of higher alcohols decreased in all the wines independently of the vinification method. However, the ethyl esters of fatty acids decreased in wine aged in barrel and increased in wine aged in bottle, so it would seem that these compounds interact with the lees present in the barrels and/or with the wood of the barrel. The ethyl esters of organic acids increased during ageing both in barrel and bottle. CONCLUSION: The ageing of Chardonnay wine in barrel on lees did not favour the formation of esters compared to the same wine aged in bottle. Copyright © 2009 Society of Chemical Industry     

Occurrence of polycyclic aromatic hydrocarbons and their hydroxylated metabolites in infant foods

Eleven polycyclic aromatic hydrocarbons (PAHs) have been analysed in commercial milk formulae and infant cereals. Two hydroxylated PAHs metabolites (1-OH-Pyr and 3-OH-B[a]P) and their conjugates were also analysed in milk samples. To determine the selected PAH metabolites, a simple, fast quantitative and economic method was developed. This method comprising ultrasound-assisted solvent extraction, enzymatic hydrolysis, solid-phase clean-up and detection by liquid chromatography with fluorescence detection (LC–FD) and liquid chromatography tandem mass spectrometry (LC–MS/MS) as confirmatory technique. The method was evaluated by constructing calibration curves, measurement of recovery, precision and the limits of detection. The purpose of this survey was to determine the selected analytes, to assess the exposure of babies and infants and to produce data for comparison with proposed limits that were being considered at the time of the survey. The results showed that not only no samples would have exceeded the limit for benzo[a]pyrene which is used as an indicator for the presence of PAHs, but also no hydroxy PAH metabolites have been detected.     

Structural and functional properties of soy protein isolate and cod gelatin blend films

The structure-function relationship of composite films obtained from soybean-protein isolate (SPI) and cod gelatin was studied. Films with different ratios of SPI:gelatin (0, 25, 50, 75, 100% [w/w]) and plasticized by a mixture of glycerol and sorbitol were prepared by casting. Regardless of the soybean-protein concentration, the thickness and water-vapor permeability of the composite films diminished significantly as compared to pure-gelatin films. The formulation containing 25% SPI: 75% cod-skin gelatin had the maximum force at the breaking point, which was 1.8-fold and 2.8-fold greater than those of 100% gelatin and 100% SPI films, respectively. Moreover, this formulation offered high percent-deformation values lower than those of gelatin but higher than all other films containing SPI-, and the same relatively low water-vapor permeability as the 100% SPI film. While all the films exhibited high water solubility, a slight reduction in film solubility and soluble protein was observed with increasing SPI concentration. Differential-scanning calorimetry analyses revealed that gelatin was completely denatured in all films, while soy proteins largely maintained their native conformation. Analysis by fourier-transform–infrared spectroscopy revealed that the presence of 25% SPI produced gelatin conformational changes, self-aggregation of gelatin chains, and intermolecular associations via CO bonds between gelatin and SPI proteins. All films were translucent in appearance, but the yellowish color increased with increasing proportions of the soybean proteins.     

Content and distribution of vicine,convicine and <Emphasis Type="SmallCaps">l</Emphasis>-DOPA during germination and seedling growth of two <Emphasis Type="Italic">Vicia faba</Emphasis> L. varieties

This work examined the content and distribution of the pyrimidine glucosides vicine and convicine, and the nonproteic amino acid l-DOPA in cotyledons and embryo axes along the germination and seedling growth of Vicia faba L. vars. Alameda and Brocal. The behaviour of these compounds was similar in both varieties. Vicine and convicine, implicated in favism disease, slowly declined in cotyledons. In embryo axis, vicine levels were sharply reduced and convicine amount was slightly increased as assay progressed. Total pyrimidine glucosides remained unchanged in the whole plant during the study. l-DOPA only appeared in the embryo axis of V. faba seeds and the highest content was observed in Brocal variety at 6 DAI (days after imbibition). The information provided in this study could be valuable for a possible role of embryo axis, rich in l-DOPA, for the treatment of Parkinson’s disease and also as a choice ingredient for functional foods or as nutraceutical.     

Influence of SO<Subscript>2</Subscript> on the evolution of volatile compounds through alcoholic fermentation of must stabilized by pulsed electric fields

The aim of this work was to study the influence of sulphur dioxide (SO₂) on the formation of volatile compounds by yeast through wine alcoholic fermentation. Thus Parellada must was microbiologically stabilized using a pulsed electric field (PEF) treatment and inoculated with Saccharomyces cerevisiae Na33 strain. Fermentation was carried out with or without SO₂ and the results showed that the evolution of the volatile compounds profile throughout the process was similar. The content of volatile acids in wine obtained by using sulphur dioxide was not significantly different from that fermented without adding the compound. However, the final content of total alcohols and esters was significantly different even thought the differences were small. Consequently, when grape must is treated by PEF the sulphur dioxide concentration usually used in winemaking could be reduced to safer levels or even eliminated without an important effect on the volatile compounds content of the final product. Therefore, the absence of sulphur dioxide should not have a negative impact on the sensory characteristics of wine.     

Tannin‐Tethered Gelatin Hydrogels with Considerable Self‐Healing and Adhesive Performances

Hydrogels, especially the ones with self‐recovery and adhesive performances, have attracted more and more attention owing to their wide practical potential in the biomedical field involving cell delivery, wound filling, and tissue engineering. Tannic acid (TA), a nature‐derived gallol‐rich polyphenol, exhibits not only unique chelating properties with transition metal cations but also desirable anti‐oxidation properties and strong bonding capability to proteins and gelatin. Thus, taking advantage of the versatility of TA, a one‐pot method is proposed herein to produce TA‐modified gelatin hydrogels with the aid of NaIO₄ under basic conditions. By changing the amount of NaIO₄ used, the obtained hydrogels are covalently cross‐linked to different degrees and consequently exhibit diversity in their self‐healing and adhesive properties. The gelling time, viscoelasticity, and morphology of hydrogels are investigated, and when the feed molar ratio of NaIO₄ to TA is adjusted to 15:1, the fabricated hydrogel shows optimum self‐healing efficiency of 73% and adhesive strength of 36 kPa. Additionally, considering the completely natural origin of TA and gelatin, this study offers an original way for the fabrication of biocompatible self‐healing and adhesive materials.     

Shelf life and quality of skim milk processed by cold microfiltration with a 1.4-μm pore size membrane,with or without heat treatment

The objective of this study was to evaluate the effectiveness of cold microfiltration (MF), alone or in combination with heat treatment, in extending the shelf life of skim milk. Raw skim milk underwent MF at 6 ± 1°C with a ceramic membrane of 1.4-μm pore size, at a transmembrane pressure of 75.8 kPa and a crossflow velocity of 7 m/s. Samples of raw skim milk; MF skim milk; high-temperature, short-time (HTST)-pasteurized milk; and MF+HTST-pasteurized skim milk were stored at 6°C for 92 d. During the shelf-life study, the total bacterial count and degree of proteolysis were evaluated weekly. The study was replicated 3 times. Cold MF was very effective in reducing the microbial load in skim milk, and an average of 3.4 log reduction in vegetative bacteria was obtained. Although HTST pasteurization reduced the bacterial load by ～2 log, the MF+HTST process resulted in near complete elimination of vegetative microflora, with a total of ～4 log reduction. A 9-member sensory panel found no significant differences between skim milk samples processed with or without MF. The MF+HTST skim milk had only minor microbial growth after 92 d at 6°C, but its proteolytic shelf life was limited by plasmin activity. A reduction of plasmin activity and a slower rate of proteolysis were obtained by increasing the heat treatment temperature to 85°C. The results of this study can be used to make decisions regarding processing strategies that lead to increased skim milk shelf life.     

Efficient removal of spores from skim milk using cold microfiltration: Spore size and surface property considerations

Bacterial spores present in milk can cause quality and shelf-life issues for dairy products. The objectives of this study were to evaluate the effectiveness of microfiltration (MF) in removing Bacillus licheniformis and Geobacillus sp. spores from skim milk using membranes with pore sizes of 1.4 and 1.2 µm, and to investigate the role of spore surface properties in MF removal. Cell sizes were determined by scanning electron microscopy, surface charge by zeta potential analysis, and surface hydrophobicity by contact angle measurements. Commercially pasteurized skim milk was inoculated with a spore suspension at about 10⁶ cfu/mL, and then processed by MF using ceramic membranes at 6°C, a cross-flow velocity of 4.1 m/s, and transmembrane pressure of 69 to 74 kPa. Total aerobic plate and spore counts in the milk were determined before and after MF. All processing runs and surface and product analyses were conducted in triplicate, and data were analyzed statistically. For the same strain, spores were shorter and wider than vegetative cells, averaging 1.37 to 1.59 µm in length and 0.64 to 0.81 µm in width. Reduction of B. licheniformis spores significantly increased with a reduction in MF pore size, from 2.17 log for 1.4-µm pore size, to 4.57 log for 1.2-µm pore size. Both pore sizes resulted in almost complete removal of Geobacillus sp. spores. All spores and the ceramic membrane had a negative surface charge at milk pH, indicating an electrostatic repulsion between them. Bacillus licheniformis spores were hydrophilic, whereas Geobacillus sp. spores were hydrophobic. Consequently, Geobacillus sp. spores had a tendency to cluster in skim milk, preventing their passage even through the 1.4-µm MF membrane, whereas some B. licheniformis spores could still pass through a 1.2-µm membrane. This study demonstrates that efficient removal of spores from skim milk by cold MF may require a smaller membrane pore size than required for removal of vegetative cells of the same species, and that cell surface properties may interfere with the outcome of filtration as would be anticipated based on size alone.