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PubMed2005

Volatile and non-volatile radiolysis products in irradiated multilayer coextruded food-packaging films containing a buried layer of recycled low-density polyethylene.

The effects of gamma-irradiation (5-60 kGy) on radiolysis products and sensory changes of experimental five-layer food-packaging films were determined. Films contained a middle buried layer of recycled low-density polyethylene (LDPE) comprising 25-50% by weight (bw) of the multilayer structure. Respective films containing 100% virgin LDPE as the buried layer were used as controls. Under realistic polymer/food simulant contact conditions during irradiation, a large number of primary and secondary radiolysis products (hydrocarbons, aldehydes, ketones, alcohols, carboxylic acids) were produced. These compounds were detected in the food simulant after contact with all films tested, even at the lower absorbed doses of 5 and 10 kGy (approved doses for food preservation). The type and concentration of radiolysis products increased progressively with increasing dose. Generally, there were no significant differences in radiolysis products between samples containing a buried layer of recycled LDPE and those containing virgin LDPE (all absorbed doses), indicating the good barrier properties of external virgin polymer layers. Volatile and non-volatile compounds produced during irradiation affected the sensory properties of potable water after contact with packaging films. Taste transfer to water was observed mainly at higher doses and was more noticeable for multilayer structures containing recycled LDPE, even though differences were slight.

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PubMed1963

INACTIVATION OF THE RADIATION-RESISTANT SPOILAGE BACTERIUM MICROCOCCUS RADIODURANS. I. RADIATION INACTIVATION RATES IN THREE MEAT SUBSTRATES AND IN BUFFER.

A simplified technique permitting the pipetting of raw puréed meats for quantitative bacteriological study is described for use in determining survival of these non-sporing bacteria, which are exceptionally resistant to radiation. Survival curves, using gamma radiation as the sterilizing agent, were determined in raw beef with four strains of Micrococcus radiodurans. Survival curves of the R(1) strain in other meat substrates showed that survival was significantly greater in raw beef and raw chicken than in raw fish or in cooked beef. Resistance was lowest in the buffer. Cells grown in broth (an artificial growth medium) and resuspended in beef did not differ in resistance from cells that had been grown and irradiated in beef. Survival rate was statistically independent of the initial cell concentration, even though there appeared to be a correlation between lower death rate and lower initial cell concentrations. The initial viable count of this culture of the domesticated R(1) strain in beef was reduced by a factor of about 10(-5) by 3.0 megarad, and 4.0 megarad reduced the initial count by a factor of more than 10(-9). Data suggest that M. radiodurans R(1) is more resistant to radiation than spore-forming spoilage bacteria for which inactivation rates have been published.

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PubMed1963

Changes in the microflora of haddock fillets and shucked soft-shelled clams after irradiation with Co-60 gamma rays and storage at 0 C and 6 C.

Frequency distribution patterns of aerobic-facultative microflora, obtained by random selection of macrocolonies from samples of haddock fillets and shucked soft-shelled clams before and after treatment with doses of from 50,000 to 800,000 rad of Co(60) gamma rays, are presented, with analyses and interpretation. The data showed that a decided change occurred in the constitution of the microbial populations of both products: from a mixed gram-negative-gram-positive flora to a predominantly gram-positive flora immediately after irradiation. The great majority of these surviving microorganisms were micrococci, sporeforming bacilli, and certain yeasts, molds, and actinomyces. During storage at refrigeration temperatures above freezing, the microflora changed from the descendants of the more radioresistant gram-positive species to the more prolific gram-negative psychrophilic species that flourish at these low temperatures. Micrococci and gram-positive rods declined somewhat during the rise of the actively proteolytic-lipolytic pseudomonads and related species, but still remained at high enough levels to contribute significantly to the spoilage observed at different times in storage. The eventual spoilage of haddock fillets was characterized by discoloration of the cream-white tissue with water-soluble yellow, green, and red bacterial pigments; degradation of the tissue, by proteolytic and other microbial enzymes, to a watery, flaccid mass; and formation of volatile compounds that smelled putrid, rancid, and generally foul and pungent. Shucked soft-shelled clams displayed a different spoilage pattern, changing to a variegated brown-gray and forming a matted or loose gelatinous mass from which arose stale, acrid, putrid, sulfurous odors. These differences are believed to be attributable to the varied biochemical nature of the tissues involved, the Eh potential within the tissues, the time sequence of microfloral change, and the species and types of microorganisms associated with each product. Staphylococci were present in small numbers in some of the samples tested, but did not appear to be species of public health significance. Gram-negative enteric rods were also encountered, but were considered to be of doubtful public health importance. More detailed investigations, designed to study the effects of Co(60) gamma radiations on such microbes in sea foods, would be useful in assessing the problem further.

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PubMedDate not supplied

Migration from packaging materials into foodstuffs--a need for more fundamental information.

During recent years considerable legislative attention has been focused on food packaging materials, especially plastics, and in a number of countries extensive legislation has been formulated. Such legislation often takes the form of a positive list of permitted substances accompanied either by compositional limits or migration limits in foods or stimulant liquids. In the UK this approach has not been followed owing to the general lack of fundamental information on which to base such a system. Instead, the UK has opted for a basic legislative framework supported by informal controls which rely to a large extent on close co-operation between Industry and Government. It is recognized, however, that in future years there is likely to be a move towards more extensive legislation on packaging materials in the UK, particularly as a result of the EEC's harmonization programme. It is imperative that any future legislation is placed on a sound scientific footing and affords adequate protection for the consumer. The Government of the UK is, therefore, currently sponsoring a number of studies aimed at providing this necessary basic information.

Chemical Phenomena↗