Gwyn P. Jones

The synergistic preservative effects of the essential oils of sweet basil (Ocimum basilicum L.) against acid-tolerant food microflora

Essential oils extracted by hydrodistillation from five different varieties of Ocimum basilicum L. plants (Anise, Bush, Cinnamon, Dark Opal and a commercial sample of dried basil) were examined for antimicrobial activity against a wide range of foodborne Gram‐positive and ‐negative bacteria, yeasts and moulds by an agar well diffusion method. All five essential oils of basil showed antimicrobial activity against most of the organisms tested with the exception of Flavimonas oryzihabitans and Pseudomonas species. The inhibitory effect of Anise oil, in comparison with mixtures of the predominant components of pure linalool and methyl chavicol, against the acid‐tolerant organisms, Lactobacillus curvatus and Saccharomyces cerevisiae, was examined in broth by an indirect impedance method. Synergistic effects between Anise oil, low pH (pH 4·2) and salt (5% NaCl) were determined. The antimicrobial effect of Anise oil was also assessed in a tomato juice medium by direct viable count, showing that the growth of Lact. curvatus and S.cerevisiae was completely inhibited by 0·1% and 1% Anise oil, respectively. The results of the current study indicate the need for further investigations to understand the antimicrobial effects of basil oils in the presence of other food ingredients and preservation parameters.

Evaluation of extraction method for the analysis of carotenoids in fruits and vegetables

This study evaluated a suitable extraction method for a wide range of sample matrices in carotenoid analysis. Using canned tomato juice as a representative sample, it is shown that two solvents of low biological hazard, ethanol and hexane are the most suitable for extracting carotenoids from the matrix. The use of double extraction, each with 35ml of ethanol:hexane mixture (4:3, by volume), resulted in good recoveries of carotenoids (lycopene 96%, -carotene 102% and -carotene 93‐100%). CoeAcients of variation conducted on diAerent days were: lycopene 5% and -carotene 7%. An application of the established method to various kinds of fruit and vegetable matrices is also shown, using carrot and spinach as representative samples of root and leafy vegetables, for determining recoveries of added carotenoids. The average percent recoveries of added carotenoids from canned tomato juice, carrot and spinach were: 101, 99.8 and 101% for-carotene (12.4, 24.8, 49.6 and 99.2g/10ml of added-carotene); and 98.1, 99.7 and 96.1 percent for-carotene (25.5, 50.9, 101 and 201g/10ml of addedcarotene). These similar recoveries over the explored concentration ranges confirm that the application of established extraction method is unaAected by diAerences in matrix composition of the samples. # 1998 Elsevier Science Ltd. All rights reserved.

Simple high-performance liquid chromatographic analysis of phenol and p-cresol in urine and feces

Previous reports which present methods of analysis of phenol and p-cresol by HPLC are usually designed for the detection of these compounds in urine, can be complicated by the use of uncommon equipment or additional techniques such as steam distillation or derivatisation, or concentrate on the detection of phenol rather than p-cresol. In this paper we report a simple method suitable for the analysis of phenol and p-cresol in both urine and feces, based upon extraction into ether following acid hydrolysis and UV detection.

Comparison of a competitive binding assay with Lactobacillus leichmannii A.T.C.C. 7830 assay for the determination of vitamin B12 in foods

Abstract The results obtained by a competitive binding method for the determination of vitamin B 12 in food were compared with those obtained by a widely used microbiological assay with Lactobacillus leichmannii A.T.C.C. 7830. Both assays were performed on the same sample extract. The extraction was carried out at pH 4.5, 121°C for 10 min with 0.1 m sodium acetate-acetic acid buffer in the presence of potassium cyanide. A high correlation ( r 2 = 0.841) between the results from the two methods was found. In the case of pork and yoghurt, the large differences observed could be due to the presence of substances in their extracts which interfere with the assays. The competitive binding assay can therefore be applied to the determination of vitamin B 12 in some foods.

Cyclopropene fatty acids of six seed oils from malvaceae

Seeds ofHibiscus leptocladus, H. sturtii, Sida echinocarpa, Abutilon amplum, Gossypium robinsonii andLagunaria patersonii contained 11.2\s-26.8% oil and 11.6\s-18.2% protein. Spectral, chromatographic and chemical analyses of the seed oils revealed the presence of malvalic (0.5\s-3.2%), sterculic (0.1\s-1.7%) and dihydrosterculic (trace-0.7%) acids.

The appropriateness of using cyanocobalamin as calibration standards in competitive binding assays of vitamin B12

Abstract The forms of vitamin B12 that have been found in foods are cyanocobalamin, hydroxocobalamin, sulphitocobalamin, adenosylcobalamin and methylcobalamin. These cobalamins, with the exception of sulphitocobalamin, are also known to be present in serum and plasma. The addition of sodium cyanide, potassium cyanide, sodium metabisulphite or sodium nitrite in the extraction procedure employed for the determination of vitamin B12, however, can convert these cobalamins into derivatives which include dicyanocobalamin and nitritocobalamin. It was observed that cyanocobalamin has a binding affinity for hog intrinsic factor equal to that of methylcobalamin, dicyanocobalamin and nitritocobalamin, but not to that of hydroxocobalamin, sulphitocobalamin and adenosylcobalamin. Thus, these latter three cobalamins cannot be measured accurately using a competitive binding assay which employs hog intrinsic factor as its binding protein and cyanocobalamin as the calibration standards unless they are converted to cyanocobalamin, methylcobalamin, dicyanocobalamin or nitritocobalamin before the assay.

The appropriateness of using cyanocobalamin as calibration standards in Lactobacillus leichmannii A.T.C.C. 7830 assay of vitamin B12

Abstract The appropriateness of using solutions of cyanocobalamin as the calibration standards in Lactobacillus leichmannii A.T.C.C. 7830 assay of total vitamin B 12 in foods, plasma and serum was examined. This is because the forms of the vitamins that may be present after the addition of sodium cyanide, potassium cyanide, sodium metabisulphite or sodium nitrite in the sample extraction procedure are hydroxocobalamin, sulphitocobalamin, cyanocobalamin, adenosylcobalamin, methylcobalamin, dicyanocobalamin and nitritocobalamin, depending on the form of endogenous vitamin B 12 . Therefore, if Lactobacillus leichmannii A.T.C.C. 7830 has a higher or lower growth response to cyanocobalamin than to the other potential forms of cobalamin, the amount of vitamin B 12 determined by comparisons with calibration standards prepared from cyanocobalamin will be an under- or over-estimation. The results of this study showed that the growth response of Lactobacillus leichmannii A.T.C.C. 7830 to cyanocobalamin was similar to its growth responses to hydroxocobalamin, sulphitocobalamin, dicyanocobalamin and nitritocobalamin but lower than that to adenosylcobalamin and higher than that to methylcobalamin. Thus, total vitamin B 12 cannot be measured accurately using Lactobacillus leichmannii A.T.C.C. 7830 assay which employs cyanocobalamin as its calibration standards if adenosylcobalamin or methylcobalamin is present.