[Contamination of preserved foods by tin fragments during various methods of opening].
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Representative samples of preserved foods collected from high-risk areas for nasopharyngeal carcinoma were assayed for capacity to induce Epstein-Barr virus (EBV) by measuring induction of the DR promoter gene or of genes for early antigens in Raji cells. The two assays gave concordant results, but the DR induction assay detected EBV-inducing substances at lower concentrations and more reproducibly. Three of 17 preserved food items were active in both assays; they were also weakly mutagenic in the SOS chromotest and contained low or moderate levels of volatile N-nitrosamines. After in-vitro nitrosation, the levels of mutagens and nitrosamines increased, whereas EBV-inducing activity was unchanged or decreased. Thus, EBV inducers appear to be a different class of substances from mutagens and volatile N-nitrosamines but could act with them in the etiology of nasopharyngeal carcinoma.
Fructooligosaccharides (FOS) are short-chain sugars that occur naturally and have dietary benefits for humans. They are widely distributed in nature and are a natural part of the human diet. The objective of this study was to determine the concentrations of 1-kestose (GF(2)), nystose (GF(3)), and 1(F)-beta-fructofuranosylnystose (GF(4)) in a variety of common processed and prepared foods. An ion chromatographic method was developed for this purpose in which the sugar concentrations were measured using integrated amperometry. The samples were simply prepared by blending with water and filtering the suspensions through a 10000 Da cutoff centrifugal filter. These samples were then injected into the ion chromatograph, which had been programmed for gradient elution, and the areas of the sugar peaks obtained compared to those of standard sugars on a calibration curve. Selected samples were prepared both with and without standard spikes in order to assess the efficiency of the determination. Of the vegetables investigated, artichokes contained by far the most FOS, followed by onions; bananas contained more FOS than other fruits investigated. The method was shown to be simple, convenient, and relatively fast for the quantitation of FOS in processed and prepared food products.
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Nisin is a ribosomally synthesized peptide that has broad-spectrum antibacterial activity, including activity against many bacteria that are food-spoilage pathogens. Nisin is produced as a fermentation product of a food-grade bacterium, and the safety and efficacy of nisin as a food preservative have resulted in its widespread use throughout the world, including the U.S. Nisin is a member of the class of antimicrobial substances known as lantibiotics, so called because they contain the unusual amino acid lanthionine. Lantibiotics, in general, have considerable promise as food preservatives, although only nisin has been sufficiently well characterized to be used for this purpose. As the number of known natural lantibiotics has increased and their useful characteristics have been explored, it has become desirable to synthesize structural analogs of nisin and other lantibiotics that do not occur naturally. The fact that lantibiotics are gene-encoded peptides synthesized by transcription and translation allows structural variants to be generated by mutagenesis. This review focuses on the progress that has been made in the construction and biological expression of genetically engineered nisin structural analogs. For example, a host-vector pair has been engineered that permits the construction of mutants of the structural gene for subtilin, which is a naturally occurring structural analog of nisin. The vector is designed in such a way that the mutant gene can be substituted for the natural subtilin gene in the chromosome of Bacillus subtilis, which in turn directs the transcription, translation, posttranslational modifications, and secretion of the mature form of the structural analog. Several structural analogs have been constructed, and their properties have provided insight into some of the structure-function relationships in lantibiotics, as well as their mechanism of antimicrobial action. These advances are assessed together with potential problems in the future development of nisin analogs as valuable new food preservatives.
Ascopyrone P (APP), a novel antibacterial from fungi, was evaluated as a food preservative. Efficacy was generally assessed by comparing the time taken for test strains to grow to 10(6) CFU/g in food +/- APP. In chilled chicken soup, 2000 mg kg-1 APP prevented Bacillus cereus, Listeria monocytogenes, Pseudomonas fluorescens, Salmonella and Escherichia coli reaching this threshold for >60 days. Good activity was also observed at 500-1000 mg kg-1 but not against L. monocytogenes. No activity was observed against Saccharomyces cerevisiae. Activity was reduced at 20 degrees C, although 2000 mg kg-1 was still effective against B. cereus and P. fluorescens. APP was less effective in chilled cooked meat systems and ineffective in raw meat. In a cooked meat system at 8 degrees C, bacteriostatic effect was generally observed at 2000 mg kg-1 against Salmonella typhimurium, E. coli and P. fluorescens but not against L. monocytogenes or Lactobacillus sake. Activity against Gram-negative enteric bacteria was enhanced by low temperature. In milk, 2000 mg l-1 was effective against P. fluorescens at chilled but not ambient temperature. APP was ineffective against yeasts and the mould Byssochlamys in apple juice. A minimum of 2000 mg kg-1 APP would appear to be necessary for antibacterial efficacy in food, although low-temperature storage may help. Observed variations in sensitivity may be related to APP stability, which decreases >pH 5.5. Toxicology testing is needed before consideration of APP for food use.
The effects of the food preservatives sodium benzoate (SB), boric acid (BA), citric acid (CA), potassium citrate (PC) and sodium citrate (SC) have been studied on root tips of Allium cepa L. Roots of A. cepa were treated with a series of concentrations, ranging from 20 to 100 ppm for 5, 10 and 20 h. The results indicate that these food preservatives reduced mitotic division in A. cepa compared with the respective control. Mitotic index values were generally decreased with increasing concentrations and longer treatment times. Additionally, variations in the percentage of mitotic stages were observed. The total percentage of aberrations generally increased with increasing concentrations of these chemicals and the longer period of treatment. Different abnormal mitotic figures were observed in all mitotic phases. Among these abnormalities were anaphase bridges, C-mitosis, micronuclei, lagging, stickiness, breaks and unequal distribution.
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This is a study of 414 different foodstuff types for Cl. perfringens presence determination. Of the meat products are with the highest contamination - 32 per cent, next ranking seasoning spices ond condiments, and auxiliary materials - 10.9 per cent. In milk, dairy and confectionary products it is isolated in 3.8 per cent of samples, while in tinned foodstuffs - in 1.8 per cent. Lecithinase production of the isolated strains in Kitt-Tarozi bouillon, Following 18-20 hour-long cultivation at 37 degrees C is studied, and dosed within limits ranging from 5 to 100 DMO. In meat food - pork in its own sauce, the development and lecithinase activity of some strains with different doses lecithinase in the enriching bouillon is studied after cultivation of the same at room temperature for 18-20 hours. Under the conditions outlined it is established that the growth of the strains is analogical to that of the bouillon, whilst their lecithinase activity shows a several-fold increase, and is dependent on the individual characteristics of the strains, and on their adaptive properties. The produced quantity of lecithinase does not affect the toxicity of strains upon oral infection of the animals experimented.
One hundred twenty-eight mothers of nasopharyngeal carcinoma (NPC) cases under age 45 in Yulin Prefecture, China and 174 mothers of population controls were interviewed as part of an epidemiological study to examine childhood exposures in relation to the development of NPC. Exposure before age 2 years to a number of fermented foods was a risk factor for NPC. During weaning, intake of salted fish [relative risk (RR) = 2.6, one-sided P (P) = 0.01], salted duck eggs (RR = 5.0, P = 0.03), salted mustard green (RR = 5.4, P = 0.03), and chung choi (RR = 2.0), P = 0.003), a kind of salted root, was significantly related to an increased risk of NPC. Between ages 1 and 2 years, intake frequency of dried fish [P for linear trend test (linear trend P) = 0.002], fermented black bean paste (linear trend P = 0.0009), and fermented soy bean paste (linear trend P = 0.007) was also positively associated with NPC. A multivariate analysis of these different foods showed all except fermented black bean paste to be independently related to NPC.
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