Pascale Chalier

Antimicrobial activity of carvacrol related to its chemical structure

Aims:  To investigate the relation between the chemical structure and the antimicrobial activity of carvacrol, eugenol, menthol and two synthesized carvacrol derivative compounds: carvacrol methyl ether and carvacryl acetate against bacteria, Escherichia coli, Pseudomonas fluorescens, Staphylococcus aureus, Lactobacillus plantarum, Bacillus subtilis, a yeast Saccharomyces cerevisiae and one fungi Botrytis cinerea.

Multiple Mass Transfers of Small Volatile Molecules Through Flexible Food Packaging

This article deals with evolution of packed foodstuff quality with time of storage. The transport of small volatile molecules (flavor compounds, water vapor, and gases) into and through flexible food packaging materials is reviewed, as well as their multiple transfers. Sorption, diffusion, and permeation phenomena are distinguished. Transport properties are largely determined by packaging characteristics, flavor molecules properties, food matrix composition, and environmental conditions. Transfer of small volatile molecules into and through food packaging materials can modify food quality and properties of the packaging materials, thus possibly altering packed foodstuff shelflife. More research is required on transport of flavor molecules through packaging materials by considering liquid and solid food matrices flavored with mixtures of aroma compounds at more realistic concentrations; interactions of aroma compounds with food matrices, and with packaging being followed during storage in given environmental conditions.

Retention and Release of Cinnamaldehyde from Wheat Protein Matrices

Cinnamaldehyde treatment of gliadin films provided a means of decreasing their solubility, increasing their molecular weight profile, and reducing their overall migration into food simulants as a consequence of the high degree of polymerization achieved. Despite losses incurred in the film manufacturing process, and the amount that remained covalently bonded with protein because of cross-linking, the addition of 1.5, 3, and 5% of cinnamaldehyde (g/100 g protein) to gliadins at pH 2 rendered 1.8, 4.8, and 11.0 mg cinnamaldehyde/g film, respectively, available to be released, and therefore to exert antimicrobial activity. Cinnamaldehyde diffusivity was largely dependent on environmental conditions, increasing from 0.49×10(-15) m2/s at 30% relative humidity (RH) to 13.1×10(-15) m2/s at 90% RH and 23 °C. This water sensitivity of films provides a mechanism with a noteworthy potential to retain the compound before its use, to trigger its release when needed, and to modulate the release rate according to the product humidity.

Aromatic evolution of wine packed in virgin and recycled PET bottles.

The evolution of the aromatic profile of a rosé wine packed in glass, virgin and recycled PET bottles was studied. Wine stored in PET and glass bottles was clearly differentiated after 5months of storage but only by a limited number of compounds. More pronounced decrease of oxygen sensitive compounds such as methionol was observed in PET bottles as well as the apparition of oxidative and ageing aroma compounds such as ethyl pyruvate, furfural or dioxanes in higher concentration. Compared to virgin PET bottles, recycled PET bottles induced slight changes favouring the presence of esters and alcohols. The chemical evolution of wine was the most important phenomenon that explains the loss of flavour rather than the sorption into PET. Because of their moderate oxygen permeability, the use of virgin PET and recycled PET bottles could be adapted for short conservation of wine but detrimental to aromatic quality if long conservation is intended.

Enantiodifferentiation of four γ-lactones produced by Penicillium Roqueforti

Identification and enantiodifferentiation of γ-lactones produced during the bioconversion of soy bean fatty acids by Penicillium roqueforti spores in the presence of an exogenous lipase was performed using gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode. It was shown that 4-dodecanolide and 4-hexanolide were first produced with an enantiomeric excess (99%) in favor of the (R) form, whereas an enantiomeric excess in favor of the (S) form (94%) is found for (6Z)-dodecen-4-olide, the major lactone produced by the fungus. If incubation was continued, mixtures of both enantiomers were found, more particularly for 4-decanolide (R/S:40/60), which was produced only after 120 hr of incubation. The results obtained can be explained by the stereoselective hydroxylation by a 10-hydratase and/or a 10-lipoxygenase of the unsaturated fatty acid precursors, oleic and linoleic acids, and by competition between different pathways. The results point out the limitations of chiral GC analysis as a criterion for the natural origin of relevant lactones, and the complexity of mechanisms involved in γ-lactone formation by microorganisms. Chirality 10:786–790, 1998.

Effect of ethanol on the sorption of four targeted wine volatile compounds in a polyethylene film.

The objectives of this study were to demonstrate that the presence of ethanol in a solution containing two esters and two aromatic alcohols has several consequences on the sorption of these compounds into polyethylene (PE) film. First, sorption of ethanol into the PE film occurred at the same time as water and reached 8 kg m(-3) using 12% v/v of ethanol. This sorption was associated with an increase in PE crystallinity, which may have prevented the sorption of volatile compounds despite their strong affinity with PE film, as evaluated by Hansen solubility parameters. Moreover, increasing the ethanol concentration increased the solubility of the four volatile compounds. In the case of aromatic alcohols, the sorption was decreased in the presence of ethanol as expected. In the case of esters, as their hydrolysis was substantial in the presence of water, the consequence was a higher sorption into the PE film in the presence of ethanol than in its absence. Nevertheless, the sorption also depended on the concentration of ethanol and the heterogeneity of the ethanol-water mixture as well as the presence of other volatile compounds, as in the case of 4-ethylphenol. In conditions simulating wine packaging, losses of volatile compound by sorption and by permeation estimated after only 5 days of contact varied between 0.08 and 25% for 2-phenylethanol and ethyl hexanoate, respectively.

Modified atmosphere packaging using environmentally compatible and active food packaging materials.

Publisher Summary In response to consumer demand and the market trend for more convenient, safer products that can be stored longer despite containing low quantities of preservatives, active packaging has become more of a factor in food packaging innovations. Packaging that was limited to protecting food products against external influences is no longer considered as an inert barrier and might be termed active when it interacts with food, or its surrounding environment, to delay degradation and extend shelf-life. Currently, there is an increasing interest in the possible use of natural solutions to delay and prevent microbial growth in food items, responding to consumer pressure to reduce chemical additives in foods and/or strong, detrimental thermal treatment. Antimicrobial packaging is expected to improve the shelf-life and microbial quality of packaged food. The antimicrobial effect of packaging materials could be achieved either by direct contact with food surfaces, using antimicrobial, non-migratory, or controlled diffusion systems, or by indirect contact, using volatile antimicrobial-releasing systems to create a modified antimicrobial atmosphere in the headspace of packaging. Many preservatives, such as bacteriocins, organic acids, various plant extracts, volatiles from essential oils, and silver-substituted zeolite, have been incorporated in packaging materials to provide antimicrobial activity.

Control of aroma transfer by biopolymer based materials

Abstract Biopolymers such as proteins offer unique functional properties that can be used in the field of edible or biodegradable active packagings. Among the barrier properties of biopolymer based packaging, the knowledge of the aroma compound transfer is required (i) to control losses and sorption of aroma compounds which are important contributors to the sensory product quality (ii) or to emit desirable flavour from active packaging in a controlled way. Permeability of 2-heptanone in protein coated papers was investigated. It was demonstrated that coating by gluten or casein decreased the permeability of 2-heptanone and that coated papers had promising aroma barrier compared to other packaging materials such as sulphuric or paraffin papers or LDPE. The ability of biopolymer films to control aroma release was also demonstrated. An aroma compound (carvacrol) was incorporated in a gluten protein matrix, which showed adequate ability to maintain aroma compounds during film processing. The release of the aroma compound into the headspace was followed under accelerated conditions of temperature and relative humidity (30°C and 60% RH). It was shown that the release rate was not dependent on carvacrol amount. The gluten film delayed aroma compound emission into the headspace for more than a month.

The use of active PET to package rosé wine: Changes of aromatic profile by chemical evolution and by transfers

Active Polyethylene Terephthalate (PET) bottles containing 1 or 3% of oxygen scavenger (named 1osPET and 3osPET) were used to pack rosé wine. Changes in the aromatic profiles were monitored during 12months and compared to those of a wine packed in glass bottles. Wine in 1osPET bottles was differentiated from wine in glass or 3osPET bottles by ten aging markers such as cis-dioxane, ethyl pyruvate or furfural. Only trans-1,3-dioxolane allowed to discriminate wine in glass and in 3osPET bottles. Methionol, an oxygen sensitive aroma compound, was preserved in glass and 3osPET bottles but was slightly degraded (15%) in 1osPET bottles. Chemical reactions were the main cause of the aroma compound degradation. Indeed, the total amount of compounds sorbed only reached 160μg considering the bottles and the joint of cap after 12months of storage. The use of PET with 3% of oxygen scavenger is adapted to pack wine for at least 12months.

Interfacial properties at oil/water interfaces and emulsifying properties of Acacia gum: Acacia senegal vs. Acacia seyal

T bacteria which produce lactic acid as their major fermented product belong to the group of Lactic acid bacteria (LAB). Generally, most of the LAB are an essential part of normal gut flora and number of studies have been performed to check the positive effects of LAB (Probiotics) on human health especially related to stomach. The focus of our study was to find the potential role of LAB isolated from local Dahi in various aspects. Dahi was collected from different areas of Lahore city under aseptic conditions. LAB was isolated on a selective media (MRS) and screened by using different parameters i.e. Gram staining, catalase test, acid tolerance, biochemical identification, antimicrobial and antifungal activity. Isolates of LAB were checked for their level of endurance to acidic environment, as human stomach has low pH. This was followed by testing both, antimicrobial and antifungal activity, carried out via agar well diffusion method. The results showed that the LAB which were isolated during our study are against bacterial pathogens, E. coli ranges from (13.66mm-17.00mm), Salmonella enterica (14.33mm-19.33mm) and Staphylococcus aureus (14.33mm-16.33mm). Along with that, all isolates showed very clear zones of inhibition against fungal pathogen Aspergillus niger (12.33mm-14.66mm). Hence, the local fermented milk product Dahi is a potential source for both maintaining the normal gut micro flora and can act defensive bacteria against the harmful and pathogenic bacteria.This report assessed and compared the antioxidant potentials, quantities of ascorbic acid and phenolic compounds in methanolic extract of varieties of onions and garlic cultivars in Nigeria. The pH and total acidity of the extracts were equally determined. Antioxidancy of the cultivars were analysed using the in vitro assay techniques with 2,2-diphenyl-1-picryl Hydrazyl (DPPH) free radical scavenging and ferric reducing capacity. Ascorbic acid phenolic content were determined by volumetric and Folin-Ciocalteus method respectively. The pH and total acidity were respectively 5.65 and 0.150mmol/L (red onion), 5.69 and 0.123mmol/L (white onion) and 6.94 and 0.105mmol/L (garlic). Red onion had the highest value of total phenols, ascorbic acid and free radical scavenging activity of 14.25±0.35mg GAE/ml, 229.098mg/100g, 66.44% respectively. In DPPH assay, red and white onion showed higher tendency to inhibit auto-oxidation when compared to garlic. The ferric reducing ability was greatest in garlic and least in white onions. These data indicate that with respect to antioxidant activity, red onion variety has highest health promoting potential among others.