Growth and survival of Staphylococcus Aureus in modified atmosphere packaged fresh/wet fettuccine noodles

Author

Roslyn Essie Rambo

Date of Award

5-1994

Degree Type

Thesis

Degree Name

Master of Science

Major

Food Science and Technology

Major Professor

John R. Mount

Committee Members

F. A. Draughon, David Golden

Abstract

Fresh, wet fettuccine pasta noodles were placed in plastic containers in barrier bags and the atmosphere was modified inside the bags to one of the following: air, or C02:N2 mixtures of 20:80, 30:70, 40:60 or 50:50. The pasta samples were then inoculated with Staphylococcus aureus (ATCC #13565) at 4.6 log CFU/g. The modified atmosphere packaged pasta was then stored at 4°C for 28 d and sampled every 7 d, or stored at 7.5°C for 16 d and sampled every 4 d, or stored at 21°C for 4 d and sampled every day. S. aureus growth was evaluated for all samples. Presence of staphylococcal enterotoxin was determined for selected samples of each treatment by SET-RPLA detection method. pH and moisture content of the pasta samples also were determined.

There was no growth of S. aureus observed in the pasta stored at 4°C during the 28 d storage period under any of the atmospheres and no toxin production was detected in samples stored 28 d. Growth of S. aureus did occur at 7.5°C with up to 1 log increase in pasta samples stored under 20 to 40% CO2 and 2 log increase in samples in air after 16 d. Toxin production was detected in samples stored 12 d in air or 20 or 40% CO2 and at 16 d in the pasta samples stored in 50% CO₂. Very rapid growth of S. aureus occurred in pasta stored at 21°C in all storage atmospheres. Counts were above 10⁸ in the samples stored in air and the samples stored in CO₂ ranged from 5.5 to 7.2 log S. aureus CFU/g after day 1. Enterotoxin was detected in each of these samples. The moisture content of the samples did not change significantly during storage. pH changes could not be correlated to microbial growth or CO₂ level during the storage periods.

Fresh pasta had to be stored at 4°C to prevent S. aureus growth and enterotoxin production. CO₂ may have a slight inhibitory effect at higher temperatures but would only be effective for short term temperature abuse rather than total control at elevated temperatures.

Recommended Citation

Rambo, Roslyn Essie, "Growth and survival of Staphylococcus Aureus in modified atmosphere packaged fresh/wet fettuccine noodles. " Master's Thesis, University of Tennessee, 1994.
https://trace.tennessee.edu/utk_gradthes/6957