Aroma compounds, retention

Sadafian, A. and Crouzet, J., Aroma compounds retention during extrusion cooking, in Frontiers of Flavor, Charalambous, G., Ed., Elsevier Science Publishing, Amsterdam, 1987, p. 623. 

The surrounding medium of encapsulated aroma such as polysaccharides, proteins, lipids, and salts could play an important role in release in liquid media and then on aroma compound retention by the film matrix. Different behaviors have been observed in the presence of salt or sucrose molecules of aroma compound volatility in food products, observing that some of them presented a salting out effect (favored release by volatilization), others an opposite salting in effect, and for some others no modification (Lubbers et al., 1998 Van Ruth et al., 2002). Similar effects could be observed in the release of the aroma compounds encapsulated in films. While the salting out effect should accelerate the release, the salting in could decrease the rate of the release. 

Ultrafiltration of heterogenous colloidal suspensions such as citrus juice is complex and many factors other than molecular weight contribute to fouling and permeation. For example, low MW aroma compounds were unevenly distributed in the permeate and retentate in UF in 500 kd MWCO system (10). The authors observed that the 500 kd MWCO UF removed all suspended solids, including pectin and PE. If PE is complexed to pectate in an inactive complex, then it is conceivable that release of PE from pectin with cations will enhance permeation in UF. At optimum salt concentration, less PE activation was observed at lower pH values than at higher pH (15). In juice systems, it is difficult to separate the effect of juice particulates on PE activity. Model studies with PE extracts allows UF in the absence of large or insoluble particulates and control of composition of the ultrafilter. In... 

Activated charcoal High retention of nonpolar volatiles Water absorption. Artifact formation. Some difficulties with desorption Less used for aroma compounds... 

Determine the time and nitrogen flow rate so that breakthrough (no more retention for a given substance) of the trap does not occur. Do this by attaching a second trap in series and analyzing this trap. For aroma compounds, smell the end of the trap to detect odor-active compound leakage. Even if the vessel is heated, the trap should be kept at room temperature. 

Trap desorption. The choice of the thermal desorption apparatus is critical in order to avoid contamination and to be able to work with aroma compounds in a wide range of retention indices. In all systems, problems can be encountered due to reactive compounds or cold spots within the analyzer. It is recommended that all transfer lines, valves, or surfaces in contact with the volatile compounds be made of an inert material such as fused-silica or deactivated glass-lined stainless steel. Even more ideal are systems that do not have long... 

An aroma compound is unambiguously identified only when aroma quality, the GC retention indices, and the MS spectra are the same as for the reference compound. 

Even in this case, the use of a hybrid process combining NF, IE, and ED appears to improve the economics and performance of the tartaric stabilization of wines. For instance, Ferrarini (2001) proposed to split raw wine into a retentate and permeate by NF. The permeate, being richer in minerals, was processed by using in sequence cationic and anionic exchange resins and ED to reduce its potassium, calcium, and tartrate ion contents. By recombining the de-ashed permeate with the NF retentate, Ferrarini (2001) asserted to obtain a stabilized wine retaining almost all the flavor and aroma compounds originally present in raw wine. 

Many aroma compounds have been identified in crackers but which ones are the most important has still not been established. Further studies of these extracts should involve the use of odor assays to sort out to aroma important compounds in crackers from the unimportant aroma compounds present. For example, the method used by Shieberle Grosch (33) to describe the odor-active components in bread in terms of their flavor dilution values and the technique called charm analysis (43, 44) both concentrate chemical investigations at retention indices with odor activity. 

Jouenne, R., and Crouzet, J. (2000). Effect of pH on retention of aroma compounds by P-lactoglobulin. J. Agric. Food Chem. 48, 1273-1277. 

Ly, M.H., Covarrubias-Cervantes, M., Dury-Brun, C., Bordet S., Voilley, A., Le, T. M., Belin, J.M., Wache Y. (2008). Retention of aroma compounds by lactic acid bacteria in model food media. Food Hydrocoil., 22, 211-217. 

The alteration of flavors of wine observed when colloids were largely eliminated can be explained by the retention of aroma compounds on the macromolecules eliminated by fining processes. On the other hand, the absence of these macromolecules which increase the aroma intensity of some volatile compounds such as ethyl octanoate could incidence general modifications in the flavor equilibrium of wine. 

Bagger-Jorgensen et al. [17] found VMD to be a promising technique for retaining the aroma compounds in black currant juice. Their observations on the improved retention of aroma compound c/i-3-hexen-l-ol as a function of increased cross-flow was attributed to reduced temperature and concentration polarization, which in turn increases the aroma concentration at the vapor-liquid interface. The accumulation of aroma compounds at the boundary layer was eventually found to control flux in spite of increase in cross-flow rate. 

In two publications, Stoffelsma and Pypker (1968) and Stoffelsma et al. (1968) (Polak s Frutal Works, Amersfoort Douwe Egberts, Utrecht, Holland. See Table 4.4) give a list of 158 compounds, 30 being reported for the first time in coffee. Among them figure five esters, five lactones and five furans. The aroma compounds were isolated from a solvent extract of the steam condensate of roasted and ground coffee. They were identified by comparison of their 1R spectra, of their retention times on two GC columns and, in a number of cases of their mass spectra, with those of reference samples. 

Lubbers, S, P Landy and A Voilley (1998). Retention and release of aroma compounds in food containing proteins. Food Technology Chicago, 52,68-74. 

FIGU RE 38.3 Retention and controlled release of aroma compounds added at the food surface or entrapped in edible coatings/films. (a) Deposition of volatile-active compound on food surface and (b) food coated with an edible film encapsulating the volatile-active compounds. 

Tunc and Duman (2011) when the montmorillonite (nanoclays) content in chitosan films increased. Solid particles such as beeswax or montmorillonite probably reduce the diffusivity of the volatile compound because of increasing tortuosity and then delay of the aroma loss by the films. A significant increase of thymol release rate with the increase of the bran concentration was observed by Mastromatteo et al. (2009). So, in this case, incorporation of nanoparticles (spelt bran) had the opposite effect and was unfavorable for volatile compound retention. 

Ciobanu, A., Mallard, I., Landy, D., Brabie, G., Nistor, D., and Fourmentin, S. (2013). Retention of aroma compounds from Mentha piperita essential oil by cyclodextrins and crosslinked cyclodextrin polymers. Food Chemistry, 138, 291-297. 

Wine processing by a hybrid membrane process is shown in Figure 3.20. The first UF unit removes microorganisms, coUoids, and high molecular weight materials. The MF step removes yeast used for fermentation. The second UF unit is used for sterifising prior to botding. Membrane pore size plays a crucial part in the retention of colour and aroma compounds. UF membranes with MWCO of between 100,000 and 500,000 Da are best [23]. 

Goubet I, Le Quere JL, Voilley A (1998) Retention of aroma compounds by carbohydrates influence of their physicochemical characteristics and of their physical state. J Agric Food Chem 48 1981-1990... 

Other properties worth mentioning for PLA are further highlighted here. Microorganisms such as molds cannot grow easily on the surface of PLA, as shown in Figure 28.3. Colorants and aroma compounds do not diffuse easily from foods into the polymer (Table 28.5). Oriented PLA film shows better deadfold and twist retention properties than polyethylene (PE). 

The retention or loss of aroma compounds is also influenced by the structure (amorphous or crystallized) of the dried product Structural changes can be used for spray drying encapsulation processes (Bhandari et al., 1992 Re, 1998). Crystallization tends to increase the loss of aroma, because it rejects impurities, including volatiles. Senoussi et al. (1995) measured the loss of diacetyl as a function of the rate of crystallization of lactose during storage. They found that when the lactose was stored at 20 °C above the glass transition temperature Tg, the amorphous product immediately crystallized and practically all diacetyl was lost after 6 days. Levi and Karel (1995) also found increased rates of loss of volatile (1-n-propanol) as a result of crystallization in an initially amorphous sucrose system. 

The aroma barrier properties of protein-based materials seem especially interesting for blocking apolar compound permeation. However, it is hard to determine the relationship between the physicochemical properties of aroma compounds and their retention by protein films (41). 

Static headspace gas chromatography (SHGC) was used to study the effects of saliva volume on the retention of the five aroma compounds by the emulsion. Emulsion to saliva ratios included 100 0, 80 20, 60 40, and 40 60. The 2mL of the samples was transferred to 10-mL headspace vials, which were then incubated at 37°C and agitated at 750 rpm for 6 min, using an automated headspace unit (Combipal-CTC Analytics JVA Analytical Ltd., Dublin, Ireland). One milliliter of the headspace was injected and analyzed by using a gas chromatograph (GC Varian CP-3800 JVA Analytical Ltd.) equipped with a flame ionization detector (FID). The injector and detector... 

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