Emulsifying properties of Acacia senegal gum: Impact of high molar mass protein-rich AGPs.

The impact of high molar mass protein-rich arabinogalactan-proteins (AGPs) on emulsifying properties of Acacia senegal gums were studied using reconstituted gums obtained with two distinct fractions: one containing these specific high molar mass AGPs and the other protein-poor low molar mass AGPs. To produce and stabilize limonene emulsions, the experimental design emphasized not only the role of high molar mass protein-rich AGPs, but also the importance of high total concentration. At low protein contents, reconstituted gums required a slightly higher content in high molar mass protein-rich AGPs than original A. senegal gum, that confirmed the role of low molar mass protein-rich AGPs in the adsorption at interfaces. The comparison of the creaming index between original and reconstituted gums as well as the monitoring of instability phenomena by turbiscan up to 30 days clearly demonstrated the prevalent impact of the bulk apparent viscosity in the long-term stability of emulsions.

Active Food Packaging Based on Biopolymers and Aroma Compounds: How to Design and Control the Release.

Aroma compounds are known to be efficient active agents for a broad range of applications (antimicrobial, anti-oxidant, insect repellent…) that are highly sought when aiming at extending shelf life of food or biological products. However, they are intrinsically odorant and volatile at ambient temperature, which restricts the processing routes used to introduce them in a polymeric matrix and can affect their mode of action and limit efficiency. Indeed, due to their high sensitivity toward temperature they can be lost or transformed during processing. Acting after being released in the headspace, their concentration has to be controlled to avoid any odorant contamination of the targeted products. Hence, the ability for an aroma compound to be retained in a polymeric matrix, and then released when submitted to a triggering effect, are the two main requirements that should be satisfied. The volatile nature of the aroma compound offer the possibility when introduce in the packaging to act by direct or indirect contact with the product and thus to be used in different ways; as a coating layer directly applied on the product surface, as a self-supported film or as coated paper when associated with a paper sheet, as well as an object that could be inserted in the package. As biopolymers such as proteins and polysaccharides are able to retain aroma compounds but also to favor their release by modification of their structure when the relative humidity (RH) and temperature change, they are relevant carriers of these specific aroma compounds. Examples of how active packaging systems with limonene, eugenol and carvacrol as active agents were designed and elaborated. These examples will be presented with a special focus on the processing conditions and the way to improve their aroma compound retention and the release control (biopolymer nature, cyclodextrin clay addition…). Avrami's equation has been used to model the transfer of aroma compound and to advantageously compare it taking into account the mechanism in relation to the biopolymer structural changes.

Rapid quantification of clove (Syzygium aromaticum) and spearmint (Mentha spicata) essential oils encapsulated in a complex organic matrix using an ATR-FTIR spectroscopic method.

Essential oils (EOs) are often encapsulated in various and complex matrices to protect them against potential degradation or to control their release. To achieve an optimum use in food products, their rapid and precise quantification after encapsulation and storage is required. Hence, a rapid ATR-FTIR method was developed and tested with two encapsulated essential oils (EOs): clove (Syzygium aromaticum) and spearmint (Mentha spicata);. Despite, the complexity of the matrix, this method coupled with univariate or multivariate regression models exhibited high potential for global quantification of the two encapsulated EOs. For clove EO, in relation to the major presence of eugenol and eugenol acetate, an analysis based on a unique band (1514 cm-1) was sufficient to obtain a good prediction with RMSEP value of 0.0173 g of EO per g of matrix. For spearmint oil which is characterized by numerous terpenoid compound, three bands (799, 885, and 1680-1676 cm-1) were suitable for a good prediction with RMSEP value of 0.0133. ATR-FTIR method was compared with a reference gas chromatography FID quantitative method in an EO release experiment and its efficiency was evaluated through modeling by the Avrami equation. Beside time saving, the ATR-FTIR method was also capable of monitoring the EO profile. This method could be easily adapted as a routine analysis in the EOs industry as quality control.

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.

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.

Changes in nutritional and sensory properties of orange juice packed in PET bottles: an experimental and modelling approach.

Sensitivity to oxidation of an orange juice was investigated through packaging in standard PET or active PET with oxygen scavenger bottles. The evolution of dissolved oxygen was found to be similar in all bottles, whereas ascorbic acid degradation was related to the oxygen transfer with higher losses in standard PET (53%) against active PET (31%). Moreover, when juice was exposed to high intensity light, a fold faster degradation of ascorbic acid was observed compared to total darkness. Depending also on the light intensity and regardless of the package permeability, changes in the aromatic profile of the juice were observed due to the degradation of limonene and the formation of α-terpineol, an off-flavour. A mechanistic model was developed to predict the shelf life of orange juice. This model, coupling O2 transfer and ascorbic acid oxidation reaction in the bottled juice, confirmed that oxygen permeation through packaging material could not be neglected.

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.

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.

Identification of Saccharomyces cerevisiae strains for alcoholic fermentation by discriminant factorial analysis on electronic nose signals

An electronic nose (E-nose) coupled to gas chromatography was tested to monitor alcoholic fermentation by Saccharomyces cerevisiae ICV-K1 and Saccharomyces cerevisiae T306, two strains well-known for their use in oenology. The biomass and ethanol concentrations and conductance changes were measured during cultivations and allowed to observe the standard growth phases for both yeast strains. The two strains were characterized by a very similar tendency in biomass or ethanol production during the fermentation. E-nose was able to establish a kinetic of the production of aroma compounds production and which was then easy to associate with the fermentation phases. Principal Component Analysis (PCA) showed that the data collected by E-nose during the fermentation mainly contained cultivation course information. Discriminant factorial analysis (DFA) was able to clearly identify differences between the two strains using the four main principal components of PCA as input data. Nevertheless, the electronic nose responses being mainly influenced by cultivation course, a specific data treatment limiting the time influence on data was carried out and permitted to achieve an overall performance of 83.5 percent.

Moisture and temperature triggered release of a volatile active agent from soy protein coated paper: effect of glass transition phenomena on carvacrol diffusion coefficient.

Carvacrol release from SPI-coated papers was evaluated at different relative humidities (RH; 60, 80, and 100%) and storage temperatures (5, 20, and 30 degrees C). Effective carvacrol diffusivities were determined from experimental release kinetics and by using a mathematical model based on Fick's second law. Increasing storage temperature and RH lead to an increase of carvacrol diffusivity. Depending on the relative humidity, the carvacrol effective diffusivity varied from 1.71 x 10(-16) to 138 x 10(-16) m(2)/s at 30 degrees C, from 0.85 x 10(-16) to 8.78 x 10(-16) m(2)/s at 20 degrees C, and from 0.11 x 10(-16) to 7.50 x 10(-16) m(2)/s at 5 degrees C. The combined effect of relative humidity and temperature on diffusivity was particularly marked at 30 degrees C and 100% RH. The temperature and relative humidity dependence of carvacrol release was related to the glass transition phenomenon and its effect on chain protein mobility and carvacrol diffusivity.

Antimicrobial paper based on a soy protein isolate or modified starch coating including carvacrol and cinnamaldehyde.

Soy protein isolates (SPI) and octenyl-succinate (OSA) modified starch were used as paper coating and inclusion matrices of two antimicrobial compounds: cinnamaldehyde and carvacrol. Antimicrobial compound losses from the coated papers were evaluated after the coating and drying process, and the two matrices demonstrated retention ability that depended on the compound nature and concentration. Whereas carvacrol losses ranged between 12 and 45%, cinnamaldehyde losses varied from 43 to 76%. The losses were always higher from OSA-starch-coated papers than from SPI-coated papers. During storage in accelerated conditions, at 30 degrees C and 60% relative humidity, carvacrol retention from coated papers was found to be similar whatever the coating matrices and the carvacrol rate. In contrast, the retention from SPI-coated papers was particularly high for the cinnamaldehyde concentration of 30% (w/w) compared to the lowest (10% w/w) or highest concentration (60% w/w). Compared to carvacrol, faster release was observed, particurlarly when OSA-starch was used. The antimicrobial properties of the coated papers were shown against Escherichia coli and Botrytis cinerea and explained by favorable conditions of total release of the antimicrobial agents.

Effect of concentration and relative humidity on the transfer of alkan-2-ones through paper coated with wheat gluten.

The transport properties of two methyl ketones, 2-heptanone and 2-nonanone, through a paper coated with a wheat gluten (WG) solution were studied as a function of aroma compound concentration differential and relative humidity. Whatever the conditions, coating improved the aroma barrier properties of the paper. Whereas permeability of 2-nonanone through WG coated paper was not affected by the concentration differential, a high concentration of 2-heptanone induced a permeability increase, which can be explained by a slight plasticization effect of this compound. The moisture content of the films markedly affected the barrier properties depending on the aroma compound. For 2-heptanone, the most polar compound, the increase of permeability with relative humidity was related to the increase of diffusivity and solubility coefficient of this compound. With 2-nonanone, permeability and diffusivity coefficients strongly decreased with the increase of moisture content. This decrease could be linked to the hindrance in diffusivity of the less polar compound induced by the presence of water molecules. The different behavior in permeation properties seems to be related to the hydrophobic nature of the aroma compound. At intermediate and high humidity levels, coated papers are found to have better aroma barrier properties than LDPE films.

Tracer aroma compound transfer from a solid and complex-flavored food matrix packed in treated papers or plastic packaging film.

The objective of this work was to study the transfer of four aroma compounds (ethyl butyrate, ethyl hexanoate, cis-3-hexenol, and benzaldehyde) from a solid and complex-flavored food matrix (sponge cake) toward and through packaging films placed in indirect contact during storage in accelerated aging conditions (38 degrees C and 86% relative humidity gradient). The efficiency of treated papers relative to that of standard paper and plastic as barrier was tested. Before storage, aroma compound volatility in the sponge cake was measured, and similar values were found between aroma compounds, due to the fat content of the sponge cake. Whatever the aroma compound, permeability values during storage were similar for the same packaging film. The plastic film was the highest barrier, whereas calendering and coating treatments applied to treated papers decreased effectively their permeability. An opposite trend was observed for aroma compound sorption into packaging films during storage.

Enzymatic synthesis of aroma compound xylosides using transfer reaction by Trichoderma longibrachiatum xylanase.

Enzymatic synthesis of aroma compound xylosides was performed by Trichoderma longibrachiatum xylanase. Information concerning the nature of xylosides present in the reaction medium was obtained by GC-EI-MS, by GC-NCI-MS of TFA derivatives, and by positive FAB-MS of the reaction mixtures. Moreover, the structures of isolated benzyl beta-D-xylopyranoside and 4-O-beta-xylopyranosyl-beta-D-xylopyranoside were established by (1)H and (13)C NMR and heteronuclear two-dimensional ((1)H-(13)C) chemical shift correlation. The results obtained for hexyl and benzyl alcohol xylosides indicated that a reaction implying a transfer of one to two or three xylose units from xylan was involved. The enzyme was able to recognize xylobiose, xylotriose, and xylan as xylose donors. Benzyl xyloside, produced independently of xylobioside and xylotrioside, was found as the major kinetic product of the reaction. Benzyl xyloside was produced in higher quantities and at a higher rate than that obtained for the di- and trixyloside derivatives. The maximum production for benzyl xyloside, 1.29 g/L, was obtained in the presence of hexane (50%) used as cosolvent. Xylosides and xylobiosides of several aroma compounds, (Z)-hex-3-en-1-ol, heptan-2-ol, geraniol, nerol, and citronellol, were synthesized in different amounts, from 850 mg/L for (Z)-hex-3-en-1-yl xylosides to 1.5 mg/L for citronellyl xylosides. No synthesis occurred when menthol, linalool, and eugenol were used as acceptors.