Likens-Nickerson modified

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 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. 

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. 

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. 

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. 

Flavor Extraction and Concentration. The apparatus used for the steam vacuum stripping consisted of a Nickerson-Likens extractor as modified by Schultz et al. (2). The sample/water slurry was maintained at a boil of 57-60°C (600-610 itm gauge pressure) for one hour. During this time, approximately 200 mL of water vapor and flavor volatiles vaporized, condensed, and were collected in the 250 mL flask. A needle-valve was attached to a glass tube in the second neck of the sample flask to admit a controlled stream of charcoal filtered air through the sample for even boiling under vacuum. 

Concentrates Preparation. Volatiles concentrates were prepared from starting materials with a modified Likens and Nickerson steam distillation-extraction head (15) operated either at 1 atm. (ether solvent) or at reduced pressure (50-55mm heptane solvent). 

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