Bacterial surface translocation: a survey and a classification.

Article de synthese sur le role antimicrobien du dioxyde de carbone au niveau des aliments (eau, lait, poisson, fruits, legumes), et sur la croissance microbienne au cours de divers procedes de fermentation

The inhibition by CO2 of the growth and metabolism of micro-organisms

Effect of carbon dioxide on yeast growth and fermentation

Modified atmosphere packaging is becoming increasingly common. It has been claimed that the technique enables significant shelf-life extension but in so doing presents an increased public health risk. This paper reviews the literature relating to the scientific basis of these claims. It demonstrates that shelf-life, sensory quality and safety of packaged products may be optimised only by harmonising a complex relationship between product and process.

Modified atmosphere packaging technology: a review.

The ability of CO2 to inhibit respiration and growth of representative strains of seven species of meat spoilage bacteria was examined. Enterobacter and Microbacterium thermosphactum were unaffected by CO2. Both respiration and growth of the other species were inhibited. With four of the species (fluorescent and nonfluorescent Pseudomonas, Alteromonas putrefaciens, and Yersinia enterocolitica), the inhibition pattern in a complex medium was similar, and inhibition was incomplete and reached a maximum level at comparatively low concentrations of CO2. With Acinetobacter, inhibition continued to increase with increasing CO2 concentration. The degree of inhibition with a constant concentration of CO2 in solution increased with decreasing temperature for all CO2-susceptible species except the nonfluorescent Pseudomonas. Anaerobic growth of CO2-susceptible facultative anaerobes was unaffected by CO2.

Effect of Carbon Dioxide on Growth of Meat Spoilage Bacteria

The development of the microbial flora on meat stored in vacuum-bags at 0–2° for up to 9 weeks was studied. Although the proportion of lactic acid bacteria increased relative to the aerobic spoilage organisms, the numbers of the latter continued to increase throughout storage. The initial contamination of the meat before vacuum-packaging was important; meat with a very low initial number had lower numbers of bacteria throughout storage for up to 9 weeks and steaks cut from such meat which had been stored always had 1–2 days’ additional aerobic shelf life at 4°. Spoilage of these steaks was due either to slime formation and off-odour associated with high counts of presumptive Pseudomonas spp., or by discoloration and souring (lactic acid bacteria). Extract release volume and pH measurements performed on the vacuum-packaged primal joints were only of value in determining the onset of aerobic spoilage when large numbers of Gram negative organisms were present, whereas the titrimetric method of spoilage evaluation of the vacuum-packaged meat showed a correlation with spoilage due to lactic organisms.

Changes in the microbiology of vacuum-packaged beef.

SUMMARY: The responses of various groups of Gram negative, yellow pigmented rods constructed on the basis of classical criteria to a wide range of cultural and biochemical features were examined. The occurrence of a wide area of slime surrounding true growth with isolates which may spread but did not glide is described. The correlation between the classical groups and divisions suggested on the basis of pigment absorption curves was examined.

An initial approach to the taxonomy of some gram negative yellow pigmented rods.

Summary

Cubes of sterile beef were inoculated with pure cultures of Gram positive and Gram negative organisms isolated from vacuum-packaged beef and were stored in gaseous atmospheres containing different proportions of air, CO2 and O2 at 0 and 5°C. Generally the rate of multiplication decreased and the lag phase increased in increasing levels of CO2, but Gram positive species were more resistant to the effect of CO2 than were Gram negative organisms.

The effect of several gaseous environments on the multiplication of organisms isolated from vacuum‐packaged beef

Summary

Lactic acid, total carbohydrate and alcohol-precipitable carbohydrate concentrations in vacuum packaged beef stored at 0–2° for nought to nine weeks were generally low, although the fluctuation in concentrations from week to week could be broadly correlated with changes in the proportions of certain groups of microorganisms in the microflora. the changes in the concentrations of these constituents were not considered useful criteria of the overall bacteriological condition of vacuum packaged beef. Certain ninhydrin-positive compounds in beef increased considerably during storage in vacuum packages, probably mainly peptides and amines. an acidic odour noticeable on opening vacuum packages of beef after storage for three to four weeks or longer was attributed in part to the presence of short chain volatile fatty acids, mainly acetic acid.

Biochemical changes in vacuum packaged beef occurring during storage at 0–2°C

Some of the metabolic and biochemical characteristics of 105 organisms isolated at 4° from meat matured in vacuo at 0–2° for 0–9 weeks were studied. Proteolysis was noted in Pseudomonas spp., Achromobacter spp. and Gram negative, fermentative organisms, mainly in aerobic and low oxygen environments. Fewer organisms hydrolysed beef fat than hydrolysed tributyrin. While representatives of most of the major groups of organisms dissimilated mono- and di-saccharides, more complex carbohydrates were less readily attacked. Only Gram negative, fermentative organisms showed decarboxylase activity on amino acids. There is evidence that Pseudomonas spp. can survive in an anaerobic environment, although their metabolism is less vigorous.

J. G. Murray

Papers

Changes in the microbiology of vacuum-packaged beef.

An initial approach to the taxonomy of some gram negative yellow pigmented rods.

The effect of several gaseous environments on the multiplication of organisms isolated from vacuum‐packaged beef

Biochemical changes in vacuum packaged beef occurring during storage at 0–2°C

Some metabolic and biochemical characteristics of representative microbial isolates from vacuum-packaged beef.