Likens-Nickerson

Bouseta, A. and Collin, S. (1995). Optimized Likens-Nickerson methodology for quantif3dng honey flavours. /. Agric. Food Chem. 43,1890-1897. 

McGill, A.S. and Hardy, R. 1977. Artefact production in the Likens-Nickerson apparatus when used to extract the volatile flavourous components of cod. J. Sci. Food Agric. 28 89-92. 

As was mentioned earlier, distillation and subsequent solvent extraction remains popular in the aroma research area Q). In this method for aroma analysis, the Likens-Nickerson apparatus has been a standard for over 20 years (17, 18). The primary limitation of the Likens-Nickerson distillation/ extraction procedure has been its operation at reduced pressure. It is desirable to operate the system under vacuum in order to reduce the sample boiling point to minimize the formation of thermally induced artifacts. The fact that the solvent side of the distillation-extraction apparatus is also under vacuum makes it difficult to retain the solvent in the apparatus. Even modifications of the apparatus to include a dry ice/acetone condenser followed by a liquid nitrogen trap do not permit easy operation under vacuum. Problems arise in that the solvent or aqueous vapors reach the cryogenic traps, thereby eventually blocking the exit of the condenser. The need to minimize exposure of the sample to heat has resulted in the more frequent use of two step procedures. Very often, the sample is simply placed in a flash evaporator, a certain volume of distillate collected and the distillate is solvent extracted via either separatory funnel or a continuous extractor. In this manner, the distillation process and solvent choice are not conflicting processes. 

Figure 2. Chromatograms for matrix isolation capillary GC/IR (top) and GC/MS (bottom) of charbroiled chicken obtained by Likens—Nickerson distillation/extraction. 

Isolation of Volatiles by Simultaneous Distillation/ Extraction. The dark brown reaction mixture was placed in a 4 1 round bottom flask and continuously extracted for seven hours with 200 ml pentane/diethy1 ether (1 1) at atmospheric pressure according to the procedure described by Likens/Nickerson. The pentane/ether extract... 

We are examining those commonly used baits, the protein hydrolysates. Initial studies have used the corn gluten hydrolysate commonly known as PIB-7 or, now, as Nu-Lure Insect Bait (NLIB). This material was used in the recent successful Medfly eradication program in California. Since the fruit flies are probably attracted to the volatile emanations from the bait, we have used equipment and techniques previously developed by members of our group for flavor research. For example, a modified Likens-Nickerson simultaneous steam distillation-extraction head was developed by Flath and Forrey (67.). Also, there is a 90 liter... 

In the laboratory, a multi-stage liquid-liquid extraction can be performed by a simultaneous distillation-extraction process according to Likens-Nickerson [29] (Fig. 2.10). Here, the liquid matrix with the solute in one flask is evaporated together with an immiscible solvent in a second flask. Extraction takes place in the vapour phase where an intensive distribution of both phases is ensured. The condensed vapours from the two phases are separated via a siphon using their different densities and their reintroduction into the original flasks. As the distillation process is continued, extraction is repeated until the solute is exhausted in the original matrix. This method is very useful when traces of non-volatile solutes are present, which are only partly miscible... 

Table 1. Likens-Nickerson extraction of mixtures of cysteine with carbonyl compounds under optimum conditions for Amadori compound formation ...

Figure 2. Simultaneous steam distillation-extraction (Likens-Nickerson)...

Methods using some type of atmospheric or reduced pressure steam distillation have been historically the most commonly used, and essential oils were (11) and are still frequently isolated this way on a commercial scale. The SDE or Likens Nickerson extraction method (12,13) was an extension of the Essential Oil industry s technique of cohobation where Ae condensed steam is separated fiom the volatile oil using a simple trap and returned to the still in order to minimize loss of water soluble volatiles. SDE had actually been described earlier in practical organic chemistry textbooks (14,15). The Likens Nickerson head though was simpler and easier to construct and control than the earlier organic chemist s version. Other versions of the head have been designed and used (2). 

Frequently, steam distillation is combined with solvent extraction to obtain a more complete oil balance. The technique uses a Likens-Nickerson-type apparatus to isolate the oil as it is removed from the substrate, minimizing contact of the oil with the hot water [29]. Thermal artifact formation, though significantly reduced, is not completely eliminated by this technique [27]. A modification of the technique uses vacuum conditions to isolate the volatiles, thereby reducing the operating temperature to between 20°C and 40°C. It appears that this procedure more effectively eliminates some of the more commonly observed artifacts [30]. 

Many of the medicinal properties, including antidermatophytic, of P. frutescens have been reported [164-167]. A steam distillate was obtained from partially dried P. frutescens leaves commercially cultivated in California using simultaneous steam distillation-extraction. Finely macerated leaves (39.2 grams) were combined with approximately 600 mL of distilled water in a round bottom flask. The flask was then connected to a Likens-Nickerson distillation-extraction head. Pentane was used as the extraction solvent and the distillation was allowed to proceed for approximately 90 minutes. This process yielded 0.3 grams (0.77%) of an aroma concentrate possessing a characteristic "shiso" aroma. The antimicrobial activity of shiso, in relation to its traditional use in sashimi dishes, has been studied [168],... 

In a typical experiment, 4 kg of fresh, locally grown pumpkins (variety Connecticut field) were homogenized with 2 L of water and this slurry was placed in a 12 L three-necked flask. The sample was heated at reflux for 3 hours using a modified Likens-Nickerson distillation head (IB). The distillation was performed at atmospheric pressure and diethyl ether was used as the extracting solvent. The ethereal concentrate was dried over anhydrous sodium sulfate, filtered and concentrated using a low hold-up distillation column by the usual procedure. 

The purified dihydroxy acid was a labile component and decomposed during heating into carbonyls and oxoacids. Figure 8 presents some results of the thermal fragmentation at pH 4 - 5 in a Likens-Nickerson distillation. It can be seen that we characterized constituents similar to those in the linoleate experiment of cucumber homogenates. 50 mg precursor (9,10-dihydroxy- ( Z) -1, 2-octadecenoic acid) were decomposed into 1.95 mg ( )-3-nonenal, 0.25 mg ( )-2-nonenal, 0.51 mg 2-pentylfuran, and C -oxo- and Cg-dicarboxylic acids. In our opinion this is the most important reaction in oxidized beer (producing cardboard flavor). In an analogous reaction linolenic acid was trans-... 

Figure 8. Results of the thermal fragmentation at pH 4-5 in a Likens-Nickerson...

Alliin and deoxyalliin, two important nonvolatile flavor precursors of garlic, were reacted separately with inosine-5 -monophosphate (IMP) in an aqueous solution at pH 7.5 in a closed sample cylinder at 180 °C for one hour. The volatile compounds generated were isolated by using a modified Likens-Nickerson (L-N) distillation-solvent extraction apparatus, and analyzed by GC and GC-MS. 

Isolation of the Volatile Compounds. The total reaction mass was simultaneously distilled and extracted into diethyl ether using a Likens-Nickerson (L-N) apparatus. After distillation, 5 ml of heptadecane stock solution (0.0770 g in 200 ml diethyl ether) was added to the isolate as the internal standard. After drying over anhydrous sodium sulfate and filtering, the distillate was concentrated to about 5 ml using a Kudema-Danish apparatus fitted with a Vigreaux distillation column. It was further concentrated under a stream of nitrogen in a small sample vial to a final volume of 0.2 ml. 

Volatile compounds of garlic were collected using a Liken-Nickerson steam distillation and solvent extraction apparatus (Romer and Renner, 1974). The volatile compounds were determined using gas chromatography and then further examined by GC-MS. The... 

The simultaneous combination of steam distillation and solvent extraction, usually implemented by a Likens-Nickerson apparatus or its analogues, has also been widely used for the isolation of essential oil. The chemical composition of such essential oils will be analysed by GC-MS [40]. 

Steam distillation may be accomplished in several ways. The product may simply be put in a rotary evaporator (if liquid, or initially slurried in water if solid) and a distillate collected. This distillate would be solvent extracted to yield an aroma isolate suitable for GC analysis. The most common steam distillation method employs Simultaneous Distillation/Extraction (SDE may be called a Likens-Nickerson method). This is one of the oldest and most popular methods for obtaining aroma isolates. Chaintreau [31] has provided a very good review of this method and its evolution. An atmospheric pressure system is shown in Figure 3.4 (bottom). Vacuum systems must have joints that are air-tight, and all parts of the apparatus must be under rigid temperature control. 

An extraction combined with distillation can be achieved using an apparatus designed by Likens-Nickerson (Fig. 5.6). 

The SDK procedure was performed using a micro-version of a Likens-Nickerson apparatus [33] in the configuration for heavier-than-water solvents. The aroma components were extracted by steam distillation and the aqueous distillate was simultaneously extracted with dichloromethane. The organic extracts were analyzed by GC-FID and GC-MS. The DHS technique was carried out with adsorption on Tenax traps and thermal desorption with ctyofocusing of the volatile substances into the GC capillary column. 

DS Mottram, DJ Puckey. Artefact formation during the extraction of bacon volatiles in a Likens-Nickerson apparatus. Chem Ind 1978 385-386, 1978. 

Typically the sample flask has a 500 ml to 5 liter capacity and contains the sample dissolved or dispersed in water so that the flask is less than half Ailed. Agitation is advisable if suspended materials are present to prevent bumping. As with all distillations, the pH of the sample should be recorded (and adjusted if necessary) prior to distillation. Heat may be supplied by a heating mantle or (better if solids are present) a heated oil bath with stirrer. The solvent is normally contained in a pear-shaped flask of 10-50 ml capacity. Many solvents have been employed. In one model system study, Schultz et al. (18) compared various solvents as the extractant. They reported that hexane was an excellent solvent except for lower-boiling water-soluble compounds, where diethyl ether was considerably better. Use of methylene chloride has been recommended in a modified Likens-Nickerson extractor (19). Currently, most researchers appear to be using pentane-diethyl ether mixtures. 

An impressive example of the use of a Likens-Nickerson extractor is shown in Fig. 8. This figure shows the gas chromatogram of a green and a roasted Kenyan coffee and shows how aromatic compounds are generated in the roasting process (W. Holscher, personal communication). 

The lipid material may be steam distilled at atmospheric pressure or under vacuum, as was described in Sec. IV, and subsequently subjected to solvent extraction. Alternatively, a modified Likens-Nickerson extractor has been described (19), which permits the introduction of steam into the system. Recoveries of model compounds from lipid systems were not as satisfactory as for aqueous samples. 

This chapter reviewed techniques that involve distillation and extraction procedures. These have the advantage of being simple and rapid, and they do not require a complex apparatus. For typical food products some version of the Likens-Nickerson distillation apparatus is probably the technique of choice for lipid materials, some high-vacuum distillation procedure is worth investigating initially. 

T. Misharina, R. Golovnya, and I. Beletsky, Comparison of the Efficiency of Isolation of Volatiles from Foodstuffs by Co-Distillation and Likens-Nickerson Methods, in Developments in Food Sci. V35. Trends in Flavor Research (H. Maarse and D. van der Heij, eds.), Elsevier, New York, 1994, p. 117. 

Likens-Nickerson simultaneous distillation/extraction (including in vacuum)... 

To isolate the flavor compounds, we used simultaneous distillation/extrac-tion by the Likens-Nickerson method, because ethyl-2-methylbutyrate is highly steam-volatile. To 750 g of comminuted apple we added 1.5 L of water containing 7.5 pg of pHs]-ethyl-2-methylbutyrate as the internal standard. Extractant Diethyl ether/pentane 1 1, extraction time 2.5 hours. The flnal volume of the flavor concentrate for GC/MS analysis was 1 ml. Figure 38 shows the El and Cl mass spectra of ethyl-2-methylbutyrate. Mass traces m/z 131 and m/z 136 were used for quantitative evaluation in the SIM mode. The analyzed apple contained 3.5 pg/kg of ethyl-2-methylbutyrate. 

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