Aqueous Distillate Research Articles

Etrimfos residues in rapeseed oil during laboratory scale refining

Residues of etrimfos ( O-6-ethoxy-2-ethylpyrimidin-4-yl- O,O-dimethylphosphorothionate) in rapeseed oil were examined during a laboratory scale refining technique. Little loss of residue occurred during neutralisation; however, appreciable loss occurred during bleaching, and 94.3–99.5% loss occurred after steam distillation. The aqueous distillate contained 12% of the etrimfos present at the start of distillation. The extracted meal contained no detectable etrimfos residue.

Volatile N-Nitrosamines in Dried Foods

An investigation was carried out to determine the levels of volatile N-nitrosamines in several dried food commodities such as malt, instant skim milk powder, infant formula containing milk powder, instant coffee, soup and soup bases, and baby cereals. The method involves vacuum distillation of the sample from 3N KOH or 1% sulfamic acid, followed by extraction of the aqueous distillate with dichloromethane. The dichloromethane extract is then washed with an acidic buffer (to remove amines), dried over anhydrous sodium sulfate, concentrated in a Kuderna-Danish concentrator, and analyzed by gas-liquid chromatography, using a thermal energy analyzer. Detection limit is 0.1-0.5 ppb. Of the samples analyzed thus far, all malts (22 samples) and instant skim milk powders (11 samples ) were positive for N-nitrosodimethylamine (NDMA); average levels were 7.4 ppb (1.3-67.0 ppb) and 0.4 ppb (0.3-0.7 ppb), respectively. Traces of NDMA and/or N-nitrosopyrrolidine were also detected in 3 of 20 dried soups and 5 of 10 instant coffees analyzed. Traces of NDMA and/or N-nitrosopiperidine (NPIP) were detected in 3 of 8 powdered instant formulas. All for baby cereal samples were negative. The identity of NDMA in 14 samples of malt and that of NDMA and NPIP in a infant formula was confirmed by gas liquid chromatography-mass spectrometry; identity of N-nitrosamines in 3 instant coffees and 1 infant formula was independently verified by high pressure liquid chromatographic analysis.

Determination of TBA number by high performance liquid chromatography

AbstractA high performance liquid chromatographic (HPLC) method for the quantitation of malonaldehyde in aqueous distillates was developed. Compared with the standard TBA test, the HPLC method was faster, and less affected by side feactions. A total of 5 min was necessary to assay each distillate and only malonaldehyde was detected. The standard curves were reproducible and standards were stable for up to 6 days. The HPLC method could detect malonaldehyde levels ranging from 1×10−11 to 4×10−11 mol/10µL and either peak height or peak area could be used to quantitate the malonaldehyde concentration. The coefficient of determination between absorbance values determined by the TBA test and peak heights determined by HPLC was 0.946. Twenty‐one freeze‐dried chicken samples with TBA numbers ranging from 3.93 to 16.6 were used for this correlation.

Gas-Liquid Chromatographic-Thermal Energy Analyzer Determination of N-Nitrosodimethylamine in Beer at Low Parts per Billion Level

A gas-liquid chromatographic (GLC) procedure is described for the determination of low ppb levels of N-nitrosodimethylamine (NDMA) in beer. The sample is treated with sulfamic acid under acidic conditions followed by alkalinization with dilute KOH, distillation at atmospheric pressure, extraction of NDMA from alkaline aqueous distillate with dichloromethane, concentration of dichloromethane extract by Kuderna-Danish concentrator, and, finally determination by a GLC-thermal energy analyzer technique with N-nitrosodipropylamine (NDPA) as an internal standard. The method gave results comparable with 2 other well established methods. Recoveries of added NDMA, N-nitrosodiethylamine, and NDPA at levels ranging from 0.08 to 10 ppb were 75-112, 86-115, and 85-109%, respectively. Five replicate analyses of a beer sample gave a mean NDMA concentration (corrected for recovery) of 2.21 +/- 0.08 ppb (+/- SD). Minimum detection limit of the method is about 0.1 ppb.

水蒸気蒸留法による魚介類中のアルキル水銀定量

The steam distillation method for the determination of alkyl mercury in fish and shells is described: The wet samples (5-50g) are put into 500ml distilling flasks and are steam distilled after adding 40ml of 6N hydrochloric acid and 40g of sodium chloride. The aqueous distillate is put into 10ml of 3N hydrochloric acid, final volume being about 180ml. The aqueous distillate is transferred into a 200ml volumetric flask and diluted with distilled water. A 50ml portion of aqueous distillate is transferred into a separating funnel and the alkyl mercury in the aqueous distillate is extracted with a 30ml, then a 20ml portion of benzene, after which it is reextracted with 10ml of 1% cysteine acetate solution. A 5ml portion of the cysteine acetate layer is removed into a digestion flask. Alkyl mercury in cysteine acetate solution is wet-digested by the method previously reported, and is determined by flameless atomic absorption The study has shown that the alkyl mercury, that is, the methyl, ethyl or butyl compound, is entirely distilled by steam distillation, but phenyl of inorganic mercury is not. By the steam distillation method herein described, alkyl mercury in fish and shells can be completely extracted without emulsification. The data have shown quantitative recovery of methyl mercury added to a variety of samples. The coefficient of variation for repeated determinations on a tuna meat sample has been 2.0%.

CHANGES IN ESTIMATES OF SILAGE DRY MATTER INTAKE OR APPARENT DIGESTIBILITY AS AFFECTED BY METHODS OF DM DETERMINATION

Apparent digestibility coefficients and voluntary dry matter (DM) intakes by sheep fed 11 silages, comprising 3 corn, 4 legume-grass and 4 corn-hay crop silage mixtures, were estimated when silage DM content was determined by (1) toluene distillation (TD), corrected for volatiles lost into the aqueous distillate, (2) uncorrected TD, (3) freeze-drying (FD), (4) oven-drying (OD) at 40 C and (5) OD at 65 C. Highest nutrient digestibility and DM intake (P < 0.05) data were obtained by the method of corrected TD. DM intake and DM digestibility were underestimated by 7.4 and 12.0%, respectively, when oven-drying at 65 C was compared to corrected TD (P < 0.01). Digestibility coefficients and DM intakes were similar between FD and OD at 40 C. These results suggest that in vivo expressions of silage nutritive value should be based upon corrected TD for silage DM content and that biochemical determinations can be conducted on silage that has been oven-dried at 40 C.

EFFECTS OF DIFFERENT DRY MATTER DETERMINATION METHODS ON CHEMICAL COMPOSITION AND IN VITRO DIGESTIBILITY OF SILAGES

Dry matter (DM) contents of 13 silages, comprised of 5 corn, 4 legume–grass, and 4 corn–hay crop silage mixtures, were determined by (1) toluene distillation (TD), corrected for volatiles lost into the aqueous distillate; (2) TD, uncorrected; (3) freeze-drying (FD); (4) oven-drying (OD) at 40 C; (5) OD at 65 C; and (6) moisture-tester at 100 C. Corrected TD showed significantly higher (P < 0.01) DM levels compared with other methods. Up to 12.8% loss of DM resulted from heat-drying, depending on the method and the sample. Dried-ground silages were analyzed for nutrient composition. No significant changes in cell-wall constituents or organic matter contents were observed. Silages that were FD were highest in cellulose content (P < 0.05), whereas both FD and OD at 40 C resulted in significant increases in gross energy (P < 0.05) and crude protein (P < 0.01) content compared with other methods. FD or OD at 40 C resulted in the highest dry matter solubility and in vitro digestibility of cellulose, dry matter, and organic matter (P < 0.05). The lowest values for these analyses were obtained with silages heat-dried at 65 and 100 C. Results of these studies suggest that corrected TD should be used for determination of silage DM content and that in vitro analyses or other biochemical determinations should be conducted on silage samples that have been freeze-dried or oven-dried at 40 C.

The nature of volatile constituents of glues

AbstractThe volatile components of bone glues have been isolated by steam distillation. They were concentrated by ether extraction of either the neutralised aqueous distillate or of active charcoal, through which the aqueous distillate had been allowed to percolate, followed by drying and removal of the ether. Acidification of the neutralised aqueous distillate with phosphoric acid after the ether extraction, enabled the volatile acids of the glues to be concentrated by a further ether extraction, drying and removal of ether. The components of the concentrates were separated by gas chromatography and identified by mass spectrometry and/or infrared spectroscopy.Sixty‐eight compounds were positively identified and a further 19 tentatively. It has not proved possible to identify specific compounds responsible for specific off‐odours.

Identification of the predominant volatile compounds produced by Aspergillus flavus.

A culture of Aspergillus flavus grown on moistened wheat meal was homogenized with a blendor, and the resulting slurry was vacuum-distilled at 5 mm of Hg and 35 C. The aqueous distillate was collected in traps cooled to -10 to -80 C. The culture volatiles were extracted from the distillate with CH(2)Cl(2), and, after removal of the bulk of the solvent, the concentrated volatiles were examined by packed-column gas chromatography. Nineteen peaks were observed, and coupled gas chromatography-mass spectrometry was employed to identify the larger components. The compounds identified were: 3-methyl-butanol, 3-octanone, 3-octanol, 1-octen-3-ol, 1-octanol, and cis-2-octen-1-ol. The two octenols were the predominant compounds, and sufficient sample was trapped from the gas chromatograph for infrared analyses; this confirmed the mass spectral identifications and permitted the assignment of the cis designation to 2-octen-1-ol. Both oct-1-en-3-ol and cis-2-octen-1-ol are thought to be responsible for the characteristic musty-fungal odor of certain fungi; the latter compound may be a useful chemical index of fungal growth.

Identification of the Predominant Volatile Compounds Produced by Aspergillus flavus

A culture of Aspergillus flavus grown on moistened wheat meal was homogenized with a blendor, and the resulting slurry was vacuum-distilled at 5 mm of Hg and 35 C. The aqueous distillate was collected in traps cooled to -10 to -80 C. The culture volatiles were extracted from the distillate with CH(2)Cl(2), and, after removal of the bulk of the solvent, the concentrated volatiles were examined by packed-column gas chromatography. Nineteen peaks were observed, and coupled gas chromatography-mass spectrometry was employed to identify the larger components. The compounds identified were: 3-methyl-butanol, 3-octanone, 3-octanol, 1-octen-3-ol, 1-octanol, and cis-2-octen-1-ol. The two octenols were the predominant compounds, and sufficient sample was trapped from the gas chromatograph for infrared analyses; this confirmed the mass spectral identifications and permitted the assignment of the cis designation to 2-octen-1-ol. Both oct-1-en-3-ol and cis-2-octen-1-ol are thought to be responsible for the characteristic musty-fungal odor of certain fungi; the latter compound may be a useful chemical index of fungal growth.

THE MAJOR VOLATILE COMPONENTS OF CANE MOLASSES

SUMMARY —The characteristic aroma was found in the basic fraction of an aqueous distillate of cane molasses. Gas chromatographic analysis of this fraction indicated the presence of at least 35 compounds of which 29 were identified. Among these were aliphatic and aromatic esters, aldehydes, alcohols as well as several furan derivatives. The acidic fraction contained at least 11 compounds, five of which were identified as simple aliphatic acids.

A method for collection and concentration of fish volatiles

Summary. A method is described for the collection of volatiles from fish by high vacuum distillation and the subsequent concentration of the frozen aqueous distillates by zone refining. Concentrations of up to 35‐fold have been obtained. the enhanced GLC profiles thus derived greatly facilitate analysis of the mixtures. the method employs mild conditions which minimize loss or alteration and is particularly suited to the analysis of numbers of samples.

Heat-Induced Volatile Compounds in Milk

Milk, preheated at 82C for 30min, was heated to 146C for four seconds and cooled to 5C in a tubular heat exchanger. Immediately after heat treatment, the milk was vacuum distilled at 30C in a semicontinuous, reduced pressure, glass apparatus. Raw milk was distilled in a similar manner for a control. Continuous liquid-liquid ethyl ether extractions were employed to recover the compounds from the aqueous distillates. Gas chromatography, mass spectrometry, infrared spectrophotometry, and odor confirmation were used to characterize the compounds in the ethereal concentrates.The following compounds were found to be heat induced: The C3,4,5,7,8,9,10,11,13n-methyl ketones, the C8,10,12 delta-lactones, benzaldehyde, furfural, phenylacetaldehyde, vanillin, oct-1-en-3-ol, n-heptanol, 2-butoxyethanol, maltol, acetophenone, benzonitrile, benzothiazole, and diacetyl. Other food products could yield these heat-induced compounds provided the basic materials from which they originate were present during the heat treatment. The following novel compounds were found in both heated and raw milk: A dichlorobenzene, a trichlorobenzene, methyl iodide, and diacetyl.Benzonitrile, dichlorobenzene, trichlorobenzene, and methyl iodide were present in the ethereal concentrates in trace amounts.The concentration of diacetyl in heated and raw milk was determined by a modified gas entrainment, on-column trapping GLC technique. The amount of diacetyl in raw milk was 5 ppb, while the amount in the heated milk was 38 ppb, which is above the average flavor threshold for diacetyl in milk. It is suggested that diacetyl contributes to the rich or heated note in the flavor of heated milk.

Removal of volatile flavour constituents from foods prior to analysis by gas‐liquid chromatography

AbstractVolatile aroma constituents were removed from cooked chicken by vacuum distillation at 35°, followed by extraction of the aqueous distillate with ethyl chloride and concentration into a small volume of isooctane, to facilitate their analysis by gas‐liquid chromatography. In an alternative procedure the meat, powdered in liquid nitrogen, was extracted with ethyl chloride, and the volatiles were separated from the lipid extract by vacuum distillation and similarly concentrated for application to the column. The second method gave the better extraction, particularly for components of higher boiling point. Optimum sensitivity and reproducibility were achieved by transfer of the whole of a concentrated extract of the volatiles from e.g. 100 g meat in 1–3 ml of solvent on to a column previously cooled to ‐60° to ‐70°, followed by rapid heating to 31° and subsequent temperature programming to 200° in the usual way. Compounds of chain length C4 to C15 (at least) could be quantitatively transferred to the column and determined by this procedure.

Determination of phenols in oils and raffinates by ultraviolet spectrophotometry

1. The authors have developed spectrophotometric method for determining the phenol contents in aqueous distillates in the ultraviolet range for the purpose of analyzing distillates obtained by steam-distillation of phenols from MS-20 oil and the raffinate of the Groznyi refinery. It was found that at wavelength 270 mμ this method can be used for analyzing phenols in oils and raffinates. The spectrophotometric method gives results as accurate and reproducible as those obtained by the coulometric method. 2. The spectrophotometric method could be used in principle for designing an automatic ultraviolet analyzer for determining phenol contents in aqueous distillates of different degrees of purity (oils, raffinates, extracts) obtained in oil manufacture.

Volatile Carbonyl Constituents of Dairy Butter

SUMMARYVolatile constituents of fresh butter were separated from fat and other components of high molecular weight by vacuum steam distillation. The carbonyl compounds in the aqueous distillate were converted to their 2, 4‐dinitro‐phenylhydrazones. Separation of these by column and paper chromatography gave the derivatives of formaldehyde, acetaldehyde, isobutyraldehyde, isovaler‐aldehyde, n‐hexanal, n‐nonanal, phenylacetaldehyde, acetone, 2‐heptanone, 2‐nonanone, diacetyl and (‐)‐acetoin, all identified by comparison with authentic samples. Possible biosyntheses of these flavor constituents are discussed.

Determination of dry matter in silage by distillation with toluene

AbstractThe determination of dry matter in silages by distillation with toluene gives satisfactory results when an allowance is made for volatiles present in the aqueous distillate. A simple correction procedure, involving a single titration of the distillate, has been developed, and the method is considered suitable for routine purposes.

Chloramine and Crenothrix

By subjecting such a mixture to distillation in a vacuum at about 40°, after adding ZnCl2 solution to remove free ammonia and sodium hydroxide, there is obtained a concentrated solution whose analysis yields values agreeing with the formula NH2C1. From concentrated mixtures under greatly reduced pressure, chloramine is often obtained as pale yellow globules floating in the aqueous distillate. Because of instability in concentrated form, no attempt was made to obtain it pure. Chloramine escapes readily from its aqueous solution, has the odor of nitrogen trichloride and vigorously attacks the eyes. (C. A. 2, 1533.)

On Voges and Proskauer’s reaction for certain bacteria

In 1898 Voges and Proskauer described a new colour reaction which they had observed in the case of a bacillus, isolated by Voges and grown in a medium containing sugar. When potash was added and the tube allowed to stand for 24 hours or longer at room temperature, a beautiful fluorescent colour, somewhat similar to that of a dilute alcoholic solution of eosin, formed in the culture fluid, particularly at the open end of the tube exposed to the air. The reaction was found to be specific to the bacillus in question, and was not given by any of the other organisms isolated in the course of the investigation upon which they were engaged, nor by the B. colicommunis , so that it afforded a most valuable means of differentiation for the inhabitants of the intestine. Durham and How have also employed this reaction for the discrimination of intestinal bacteria, and MacConkey, in confirmation of Durham, has found that out of a large number of bacteria which were tested only three gave the reaction, these being B. lactis aerogenes (Escherich), B. capsulatus (Pfeiffer), and B. cloacæ (Jordan). The examination of the products formed by B. lactis aerogenes from glucose has shown that acetylmethylcarbinol, CH 3 .CO.CH(OH).CH 3 , and 2·3-butyleneglcol, CH 3 .CH(OH).CH(OH).CH 3 , are both present in the medium in which this has been cultivated in the presence of glucose. The acetylmethylcarbinol has not as yet been isolated in the pure state, but is present in the aqueous distillate obtained by distilling the culture medium. This disllate and the glycol were, therefore, treated with caustic potash in order to ascertain whether either of them was the cause of the reaction just described. Neither of there substances produces the characteristic fluorescent coloration with potash alone, but when peptone water is also added, acetylmethylcarbinol gives the reaction after standing for about 24 hours, whilst the glycol does not react in this way even on standing. The colaration was produced in the characteristic manner described by Voges and Proskauer, commencing at the open end of the tube exposed to the air. This suggests oxidation as a factor in the phenomenon, and as acetylmethylcarbinol is very readily converted by oxidation into diacetyl, CH 3 .CO.CO.CH 3 , this substance was tested. Diacetyl yields the fluorescent red coloration with peptone water and caustic potash in a few minutes, and by its aid a much greater depth of colour can be obtained than that observed with bacterial cultures.