Retention Of Aroma Compounds Research Articles

Influence of physicochemical interactions between amylose and aroma compounds on the retention of aroma in food-like matrices.

In food matrices, where starch is often used as a gelling or texturing agent, the occurrence of amylose-aroma complexes and their effect on the release of aroma compounds are difficult to determine. Indeed, thick or gelled systems are known to reduce the diffusion rate of flavor molecules, resulting in an increase of retention. Moreover, interactions between aroma compounds and matrix components might increase the retention of aroma compounds. The complexing behavior of three aroma compounds with amylose was studied by DSC and X-ray diffraction to determine the relative importance of these two factors. Their interaction properties were different: two of them formed complexes, and the third did not. These aroma compounds were added in food matrices containing different starches that induced different textures. Their retention was studied by static headspace analysis. The retention of aroma compounds appeared to depend on the amylose/amylopectin ratio of starch, both from the formation of complexes and by a viscosity effect.

Influence of composition and structure of oil‐in‐water emulsions on retention of aroma compounds

AbstractThe influence of the composition and structure of oil‐in‐water emulsions on aroma retention was examined for 20 volatile compounds. Compositional and structural parameters included the fraction of emulsifier phase, the fraction of lipid phase and the particle size distribution of the dispersed lipid phase in the emulsion. Air/liquid partition coefficients of dimethyl sulphide, 1‐propanol, diacetyl, 2‐butanone, ethyl acetate, 1‐butanol, 2‐pentanol, propyl acetate, 3‐methyl‐1‐butanol, ethyl butyrate, hexanal, butyl acetate, 1‐hexanol, 2‐heptanone, heptanal, α‐pinene, 2‐octanone, octanal, 2‐nonanol and 2‐decanone were determined by static headspace gas chromatography. The hydrophobicity of the compounds determined the influence of the compositional and structural parameters of the emulsions on air/liquid partitioning. Increase of the emulsifier fraction increased the retention of mainly hydrophilic aroma compounds and decreased the retention of hydrophobic compounds. Higher lipid levels led to increased retention of hydrophobic compounds and release of hydrophilic compounds. Emulsions with larger particles showed increased aroma retention, which was independent of the lipid fraction and the polarity of the aroma compounds. The data demonstrated a profound effect of both composition and structure of oil‐in‐water emulsions on the air/liquid partitioning of the 20 aroma compounds under equilibrium conditions.© 2002 Society of Chemical Industry

Retention of aroma compounds by β-lactoglobulin in different conditions

This contribution to the study of the retention and the release of aroma compounds was conducted on model systems in the presence or absence of β-lactoglobulin. To know the interactions between the aroma compounds and this protein we studied the hydration of the protein and the effect of water activity on the sorption of the volatiles. It has been shown that water is necessary in the formation of aroma–protein interactions. The presence of β-lactoglobulin in aqueous solution increased the retention of the four aroma compounds considered. They modify the flux at the interface air–aqueous solution. These results could be applied in the technology of foods such as emulsions which could be stabilized with proteins, and particularly in dairy products which are generally flavored.

Influence of the nature and treatment of starch on aroma retention

The retention of aroma compounds ( d-limonene, ethyl hexanoate, octanal and 1-hexanol) on different starch matrices was measured using inverse gas chromatography. The starch materials were native, acetylated and pregelatinised corn starches, maltodextrin and extruded corn starches. The influence of the amylose content and of the physical characteristics of starch (specific area, particle shape and size) were studied. Whatever the type of starch, retention increased with the polarity of the flavour molecules in the sequence: d-limonene<ethyl hexanoate<octanal<1-hexanol. Maltodextrin appeared to be the most efficient matrix for flavour retention, followed by pregelatinised starches, extruded high-amylose starch and finally granular starches (native and acetylated starches). Retention on native starches did not follow the amylose content, unlike that on extruded starches. Specific area was the main factor, which could explain the different behaviour of samples.

Influence of the Food Matrix Structure on the Retention of Aroma Compounds

The retention of the aroma compounds in a multicomponent medium like the food matrix is influenced by their affinity with the protein when lipid is present at a low level (0.5%). The effect of the structure of the media is also studied by using two media with the same composition; one was emusified, and the other was not. Among the studied aroma compounds, 2-nonanone and isoamyl acetate present opposite behaviors: the volatility of isoamyl acetate is not affected by the change of the medium structure whereas that of 2-nonanone increases. The decrease of retention of 2-nonanone in an emulsified system would be due to a modification of the fixation site for this compound on the protein or to a competition between the lipid and the aroma compound while the protein is adsorbed at the lipid-water interface.

Study of interaction phenomena between aroma compounds and carbohydrate matrixes by inverse gas chromatography.

Besides the conventional techniques used for the investigation of food-flavor interactions, inverse gas chromatography (IGC) may provide a useful tool for the direct assessment of the retention of aroma compounds in a matrix. IGC consists of single reference compound injections at a fixed temperature onto a column which stationary phase is the material of interest. We have applied this technique to high amylose corn starch, wheat starch, and beta-cyclodextrin matrixes, using aroma compounds presenting various functional groups. Low energy interactions were measured which may result from polar or hydrophobic binding. Starch behaved under these conditions as a polar chromatographic phase. We also focused on the influence of a physical modification of the starch on its retention properties toward 3,7-dimethyl-2,6-octadien-1-al. Retention was found to be greater after a specific thermal treatment. As checked by DSC (differential scanning calorimetry) and DMTA (dynamic mechanical and thermal analysis), the observed changes are believed to be related to the glass transition of the starch. For the time being, the dehydration of the matrix associated with the lack of control of the relative humidity within the column is the main restriction to this technique.

Effect of pH on retention of aroma compounds by beta-lactoglobulin.

Interactions between volatile compounds and BLG in aqueous solution were studied using static and dynamic headspace techniques (exponential dilution). The intensity of interactions between methyl ketones (C7-C9), ethyl esters (C6-C9), limonene, myrcene, and beta-lactoglobulin (BLG) were estimated by determination of the relative infinite dilution activity coefficients (gamma(r)). For a constant pH value, the methyl ketones retention by BLG increased significantly with the hydrophobicity of the volatiles, whereas the retention reached a maximum for ethyl octanoate in the ester series, indicating a possible steric hindrance. For limonene and myrcene an unexpected increase in headspace concentration or "salting out" effect was noticed for acid pH. The variations of the retention according to the pH increase of the medium from pH 3 to pH 11 could be related to structural modifications of the BLG. The retention increase observed between pH 3 and pH 9 resulted from the flexibility modification of the protein, allowing better accessibility to the primary or the secondary hydrophobic sites, whereas the dramatic decrease observed at pH 11 was the consequence of the alkaline denaturation of BLG. Electrostatic interactions occurring at pH 7.5 could also explain the observed retention increase.

Investigation of Mechanisms Governing Membrane Fouling and Protein Rejection in the Sterile Microfiltration of Beer with an Organic Membrane

Since the early 1980s, cold sterile crossflow microfiltration has been evaluated as a potential alternative to conventional thermal processes in the brewing industry (flash-or tunnel pasteurization). Up to now, industrial membrane development for beer microfiltration was limited both by severe membrane fouling and by protein and aroma compound retention. In the present work, fouling mechanisms and protein rejection have been investigated experimentally at laboratory scale for the microfiltration of a clarified (kieselguhr filtered) beer through a 0.2 mm polycarbonate membrane. Fouling mechanisms were analysed by using the constant pressure blocking filtration laws for which interactions arise between high molecular weight beer components and the membrane matrix resulting in pore constrictions and progressive blockage. Protein content in beer was measured using two dye-binding methods (Bradford and Lowry). It was found that permeate flux decay was governed by two successive fouling mechanisms: an internal pore fouling at the initial stages of filtration that conforms to the standard blocking model, followed by an external surface fouling conforming to the cake filtration model. The variation with time of membrane selectivity was characterized by a high initial protein transmission rate followed by a sharp decrease that occurs in a range of filtered volumes which is independent of the applied transmembrane pressure. For all experiments, protein retention level throughout the filtration was found to be closely related to the nature of fouling. It remains constant and low (<20%) in the presence of a pore diameter decrease induced by lateral adsorption of macrosolutes, then increases abruptly (up to 60%) and stabilizes when a fouling layer (gel layer) forms over the membrane surface. The significant role played in the composition of this limiting surface fouling layer by proteins (associated with polyphenols and b-glucans to form proteinaceous haze material) has been highlighted. The understanding of membrane fouling phenomena (such as the nature and location of fouling materials) is liable to lead to the design of efficient cleaning procedures for the sterile microfiltration of beer.

Retention of Aroma Compounds by Carbohydrates: Influence of Their Physicochemical Characteristics and of Their Physical State. A Review

Many aroma compounds, used to flavor food products, are used in a solid state, after encapsulation. Carbohydrates are the most common matrices used to entrap these volatiles. It has been observed that depending on the aroma compound and the carrier, efficiency can vary. This article reviews the influence of physicochemical properties of both the volatiles and the carriers on retention. The latter depends on the functional groups of the aroma compound. Moreover, it increases with molecular weight and decreases with the polarity and relative volatility of the aroma compound. This behavior can be explained by the effect of these properties on the diffusion of the aroma compound through the matrix and on the ability of the volatile to form small drops. The physicochemical properties of the carrier are important too. Retention of the aroma compound increases with the molecular weight of the carrier until an optimum is reached and then decreases for very high polymerization degrees. Viscosity, solubility, and film forming properties improve the retention ability. The effect of these parameters is discussed according to their effect on the diffusion of the volatiles. The state of the carrier has to be taken into account too. The amorphous state provides the highest retention, collapse results in losses of aroma, and crystallization leads to the greatest losses of flavors.

Retention of aroma compounds by proteins in aqueous solution

Retention of aroma compounds in sodium caseinate aqueous phase was investigated by measurement of vapour-liquid partition equilibrium (headspace analysis or exponential dilution). This retention depended on the nature of the aroma compounds and sodium caseinate content. For a homologous series of ethyl esters (ethyl acetate, butanoate and hexanoate), it increased with the carbon chain length from 0 to 38% and from 0 to 61 % for caseinate contents of 5 and 50 g.litre −1, respectively. Retention of diacetyl increased from 0 to 23% for the same range of protein content. Thermodynamic models were applied to evaluate the binding parameters n (number of binding sites of protein), K a (affinity constant) and h (Hill coefficient) to both ethyl esters. These values were compared with those given in the literature: n and K a were of the same order; h indicated a weak cooperative effect between sodium caseinate binding sites.

Study of Aroma Compounds-Polysaccharides Interactions by Dynamic Exponential Dilution

The interactions between model wine aroma compounds—limonene, isoamyl acetate and ethyl hexanoate—and several polysaccharides—modified corn and waxy corn starches, dextrine, dextrans, hydroxypropyl celluloses and galactomannans—were studied using the exponential dilution technique. Information concerning the nature and the intensity of these interactions were obtained from the study of the variation in the reduced infinite dilution activity coefficient γi∞Gamma; as a function of the polysaccharide weight fraction. Retention of aroma compounds was detected for all the compounds studied except for dextrans, and in this case a salting-out effect was developed. The biphasic curve obtained for modified starch agrees with the presence of two binding modes corresponding to the formation of amylose and amylopectine inclusion complexes. A rapid decrease in the volatility of ethyl hexanoate and limonene (30 to 80%) was obtained at 0.01 weight fractions for galactomannans and hydroxypropyl cellulose; the study of interactions between volatile compounds and these polysaccharides were limited by the strong viscosity of their solutions. In the case of dextrin, the linear decrease in γi∞Γ agrees with the existence of hydrophobic interactions. A 50% decrease in γi∞Γ was obtained for a 0.04 weight fraction of this compound which was selected for the synthesis of a model glycopeptide.

Influence of Mannaproteins from Yeast on the Aroma Intensity of a Model Wine

The influence of mannaproteins released from yeast cell walls during alcoholic fermentation on the volatility of aroma substances was investigated in a model wine. After the characterization of macromolecules (substrates), two techniques have been used to study the interactions with aroma compounds: headspace analysis and an equilibrium dialysis method. The assumed effects of these macromolecules from yeasts on the fixation of volatile compounds were demonstrated. The physico-chemical interactions between aroma substances and mannaproteins depended on the nature of volatile compounds. Protein concentration in substrates was an important factor in their binding capacity. The retention of aroma compounds (β-ionone, ethyl hexanoate) was attributed to mannaproteins having a high proportion of proteins.