Growth Of Psychrophilic Bacteria Research Articles

The effects of ozonated slurry ice treatment on microbial, physicochemical, and quality of large yellow croaker (Pseudosciaena crocea) during cold-chain circulation

Cold chains are effective in maintaining the quality of aquatic products and reducing food losses, especially for dynamic transportation. The purpose of the research was to evaluate the effects of different ice treatments on the microbial, physicochemical, and quality characteristics of large yellow croaker (Pseudosciaena crocea) during cold-chain circulation. Different ice treatments (flake ice (FI), slurry ice (SI), and ozonated slurry ice (OSI)) were used during circulation, respectively. Changes in microbial (total viable count (TVC), psychrophilic bacteria count (PBC), H2S-producing bacteria count, pseudomonas bacteria count), physicochemical (pH, K-value, total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), biogenic amines (BAs) content, color difference, texture profile analysis (TPA)) was measured. Low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) were also measured to evaluate the feasibility of preservation methods. The results demonstrated that compared with SI treatment, the growth of psychrophilic bacteria, H2S-producing bacteria, and pseudomonas bacteria was inhibited by OSI treatment on the 21st day (0.55, 0.24, and 0.73 log CFU/g reduction, respectively). Besides, OSI treatment exhibited inhibitory activity toward K-value and BAs during storage, along with texture softening. Compared with FI treatment, OSI could retard the water migration and extend the shelf-life of large yellow croaker (Pseudosciaena crocea) for another 6 days. Therefore, ozonated slurry ice will be a promising long-term preservation method for maintaining the quality of large yellow croaker.

Changing the 30-min Rule in Canada: The Effect of Room Temperature on Bacterial Growth in Red Blood Cells

Background: To maintain product quality and safety, the ‘30-min rule' requires the discard of red blood cells (RBCs) that are exposed to uncontrolled temperatures for more than 30 min. Recent studies suggest this rule may safely be extended to a 60-min rule. Methods: A pool-and-split design study (N = 4) was run in parallel at Canadian Blood Services (SAGM RBCs) and Héma-Québec (AS-3 RBCs). RBCs were spiked with ∼1 colony-forming unit/ml of mesophilic and psychrophilic bacteria. Control units remained in storage at 1-6 °C for 42 days. Test 30 (T30) and T60 units were exposed to room temperature (RT) six times during storage, each time for 30 and 60 min, respectively. Bacterial proliferation was monitored. Results: Mesophilic bacteria do not proliferate in RBCs. The growth of psychrophilic bacteria is not significantly different in RBCs exposed for 30 or 60 min to RT (p < 0.05). Conclusion: The study findings were the final evidence to support extension from a 30-min rule to a 60-min rule in Canada.

Effects of temperature on the growth of psychrophilic bacteria from glaciers.

Growth of five strains of psychrophilic bacteria (four Arthrobacter and one Pseudomonas) isolated from glacial deposits was studied at different temperatures. Three strains were facultative psychrophiles, having an optimum temperature for growth at about 25-28 degrees C and a maximum at about 32-34 degrees C. The two Arthrobacter glacialis strains were found to be obligate psychrophiles with an optimum at 13-15 degrees C and a maximum at 18 degrees C. Arrhenius plots showed that A. glacialis could compete with the facultative psychrophilic bacteria only at 0 degrees C, that is, the temperature of its natural environment. The psychrophilic Arthrobacter species studied here are more resistant to thermal stress than are marine psychrophilic bacteria. For Arthrobacter, in contrast to Pseudomonas, temperatures above the optimum induced formation of filaments and abnormal cells. The culture turbidity increased 10 to 30 times, whereas viable count tended to decrease. The thermal block seems to prevent cell wall synthesis and septation, but at a different step for each species.

Influence of Sublethal Treatment with Heat or Chlorine on the Growth of Psychrophilic Bacteria

Influence of Sublethal Treatment with Heat or Chlorine on the Growth of Psychrophilic Bacteria

THE ROLE OF PSYCHROPHILIC BACTERIA IN THE KEEPING QUALITY OF COMMERCIALLY PASTEURIZED AND HOMOGENIZED MILK

Commercially pasteurized and homogenized milk, collected during the summer, fall, and winter months and stored at 40° F and 33° F, was studied for keeping quality.When the storage temperature was lowered from 40° to 33° F, the keeping quality was found to be extended 11 to 14 days. The keeping quality of the milk stored at 40° F, when based upon the development of psychrophilic bacteria up to the 50,000 per milliliter standard, was lower than when based on the deterioration of flavor to a score of 37. The keeping quality of the milk stored at 33° F was found to be approximately the same when judged by either criterion.The keeping quality of the milk samples collected in the fall and winter was poorer than those collected in the summer. This difference was greater when the samples were stored at 33° F than when stored at 40° F.No oxidized flavors were encountered in these milk samples. The deterioration of flavor was closely associated with the growth of psychrophilic bacteria in all samples.