摘要:

The JECFA Specification for gum arabic was revised in 1990 to reflect more closely the specification of the Test Article used in evaluations that led to its classification ‘ADI not specified’ in 1982/83. Some producers and traders have objected to the Revised Specification; in contrast, consumer‐protection groups consider that it remains too lax to provide the degree of safety assurance expected. This paper presents analytical data that confirm the mean values previously established for nitrogen and the specific rotation of bulk commercial gum arabic fromAcacia SenegalThe data also establish that natural gum arabic imported into the USA and Europe in 1989/91 met the Revised Specification, but that a disturbingly high proportion of spray‐dried, processed gums sold as ‘gum arabic’ did not. NMR spectroscopy has (a) indicated that some such samples are based on non‐permitted gums and (b) confirmed that the 1983 Test Article represents not only typical 1990/91 shipments but also a wide range of reference gum arabic samples from other reputable sources. Details of a representative13C‐NMR spectrum, derived by averaging the relative intensities for the characteristic resonances of 35 gum arabic samples, are given for future regulatory/legislative purposes. Some limitations of the Revised Specification and its susceptibility to commercial exploitation are discussed.

ISSN:0265-203X    

DOI:10.1080/02652039109373991

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Gum samples from six individualCombretum nigricanstrees and two additional reference samples have been characterized.13C Fourier‐transform NMR spectra show that all have the same structure and confirm that the variations observed in their analytical parameters reflect only small fine‐structural differences. NMR spectra also reveal that eight West African ‘gum combretum’ samples from reputable commercial sources originated fromCombretum nigricans.This identification is important because gum combretum, which is not permitted as a food additive, has been exploited as an adulterant and misrepresented as gum arabic, for which not even the 1990 Revised Specification is sufficiently rigorous to detect such commercial deceptions. NMR spectroscopy has also shown that the rhamnose and uronic acid contents of gum combretum are located within internal polysaccharide chains. This explains the well‐known difference in emulsification functionality between gum arabic, in which all rhamnose and uronic acid groups are chainterminal, and gum combretum which is, in addition, markedly hygroscopic and characterized commercially by its tendency to ‘block’ in transit and storage.

ISSN:0265-203X    

DOI:10.1080/02652039109373992

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We have found that many foods are contaminated with mineral oil products used as lubricating oils/greases or as release agents. The mineral oil base of such products usually consists of branched alkanes ranging between C17and C35. It forms a broad ‘hump’ of unresolved compounds in the gas chromatogram. Examples of such products are described; contamination is shown for a sample of bread, bonbon, and chocolate, respectively. The results suggest that contamination of foodstuffs with mineral oils does not always receive the required attention. However, there is also a lack of guidelines.

ISSN:0265-203X    

DOI:10.1080/02652039109373993

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Twenty eight samples of rice, barley, millet, corn and Indian millet harvested in Korea in 1989 were subjected to assay for contamination of nivalenol (NIV), deoxynivalenol (DON) and T‐2 toxin by using gas chromatography and gas chromatography‐mass spectrometry. Seven samples were found to be positive for NIV and DON in the ranges of 189–624μg/kg and 168–506μg/kg, respectively. Of the contaminated samples, three samples, one barley, one Indian millet and one corn sample were contaminated simultaneously with both NIV and DON. T‐2 toxin was not detected in any samples.

ISSN:0265-203X    

DOI:10.1080/02652039109373994

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The occurrence of aflatoxins in some common food commodities: wheat, gram and maize flours is reported. Of the total 416 collections during three years (1987–1989) 162 were recorded to be aflatoxin‐positive. The incidence of aflatoxins was maximum in the samples of 1987. Most of the contaminated samples contained aflatoxins at levels above 20μg/kg. The environmental conditions and traditional agronomic and storage practices relating to aflatoxin incidence are discussed.

ISSN:0265-203X    

DOI:10.1080/02652039109373995

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A method is reported for the determination of theFusariummycotoxin moniliformin in cereals. The samples after extraction with acetonitrile/water are cleaned‐up on a combination of reverse‐phase and strong‐anion exchange disposable cartridge columns. The extract is then analysed by ion‐pair HPLC with UV detection. The method gave recoveries from 81 to 96% and a limit of detection of 0.05 mg/kg. A UK survey of 36 samples of maize products (principally meal and flour) generally showed detectable but low levels of contamination ranging from 0.05 to 0.25 mg/kg (with the exception of three samples where moniliformin levels were < 0.05 mg/kg). Sixty‐four samples of maize from ten different countries showed generally higher levels of moniliformin contamination, with samples from Gambia and South Africa containing 3.16 and 2.73 mg/kg respectively. Field samples of maize, oats, wheat, rye and tricticale that were hand‐selected as showing signs of visible fungal damage were obtained from Poland. Moniliformin was consistently present at high levels with amounts ranging from 0.5 to 38.3 mg/kg being associated withF. avenaceumcontamination and amounts ranging from 4.2 to 399·3 mg/kg being associated with the presence ofF. subglutinans.

ISSN:0265-203X    

DOI:10.1080/02652039109373996

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

An unidentified metabolite of dimetridazole (DMZ), found in pig plasma, muscle and kidney, was shown by chromatography and spectroscopy to be 2‐methyl‐5‐nitroimidazole (2‐MNI), resulting from N‐demethylation of DMZ. This route of degradation competes with the oxidation pathway previously described. The concentration of 2‐MNI in the plasma of pig fed medicated diet (DMZ 0.0125%) ranged from 29 to 83 ppb, 2 hours after the morning meal, similar to DMZ, but lower than that of the major metabolite, 2‐hydroxymethyl‐l‐methyl‐5‐nitroimidazole (HMMNI). Its elimination profile in plasma was biphasic, similar to those of HMMNI and DMZ. Early and terminal half lives were 2.6 and 9.1 h respectively. None of the metabolites could be detected in any of the tissues studied 49 hours after withdrawal.

ISSN:0265-203X    

DOI:10.1080/02652039109373997

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Various fresh and canned seafood products were examined for ionic alkyl lead, tetraalkyl lead and total lead. Dimethyl lead, diethyl lead, trimethyl lead and triethyl lead were extracted with diphenylthiocarbazone (dithizone) at pH 8 and 9 from enzymically hydrolysed samples. Butyl derivatives were formed by Grignard reaction prior to analysis by gas chromatography‐atomic absorption spectrometry (GC‐AAS). Tetraalkyl lead was extracted from the hydrolysates with hexane. Total lead was determined by reductive coprecipitation with palladium in the presence of ascorbic acid after nitric‐perchloric digestion.

ISSN:0265-203X    

DOI:10.1080/02652039109373998

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Concentrations of tin and lead in canned foods have been monitored since 1983 to determine the effects of recent changes in can‐making technology. In the sample studied the proportion of foods contained in non‐soldered as opposed to soldered cans has risen consistently during the survey and now accounts for 83% of all samples (excluding sardines). Foods contained in non‐soldered cans have lower lead concentrations than those contained in soldered cans and this changeover is likely to result in a decrease in dietary lead intakes in the UK.

ISSN:0265-203X    

DOI:10.1080/02652039109373999

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The extraction rate of pesticide residues in water during the infusion process is dependent on the water solubility. The extraction of pesticide residues by boiling water can be regarded as a reversible equilibrium between adsorption and dissolution. The influence of chemical degradation is not important. When the water solubility is lower than 5 mg/kg, the extraction rate is 1–4%. Within the water solubility range of 10–150 mg/kg the extraction rate(Ri)is very sensitive to the water solubility (S); the relationship can be described asRi=59.81og S‐42.5. When water solubility is higher than 170 mg/kg, the extraction rate is 90–100%.

ISSN:0265-203X    

DOI:10.1080/02652039109374000

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor