Effect of Low‐Dose (100 krad) Gamma Radiation on the Microflora of Vacuum‐Packaged Ground Pork With and Without Added Sodium Phosphates

Abstract

Survival and growth of naturally occurring or inoculated bacteria were studied in refrigerated (5"C), vacuum-packaged ground pork irradiated at 100 krad (1kGy). Numbers of naturally occurring mesophiles, psycbrotrophs and anaerobes or facultative anaerobes were reduced (PCO.01) by irradiation, whereas lactic acid bacteria were least affected. Partial bacterial recovery during subsequent storage at 5°C suggested sublethal bacterial injury due to irradiation. Irradiation prolonged shelf-life 2.5-3.5 days (3@44%) in uninoculated and l&1.5 days in inoculated (lo5 CFU/g) meat. Added sodium acid pyrophosphate (SAPP) (0.4%) contributed two additional days to inoculated, irradiated pork shelf-life but had no effect on the naturally occurring micrbflora. Lipid oxidation did not increase (P>O.O5) due to irradiation and was unaffected by phosphates.

Changes in Microflora and Other Characteristics of Vacuum‐packaged Pork Loins irradiated at 3.0 kGy

“…Because numbers of all bacterial groups increased by varying degrees in irradiated loins by the second sampling period (day 7), we concluded the applied radiation dose (3 kGy) was not always lethal. Similar recovery in radiation-injured bacteria was reported by Ehioba et al (1987) in vacuum-packaged ground pork irradiated at 1 kGy. Also bacterial cells may have shown sensitivity to dilution shortly after exposure to gamma radiation, as reported by Chowdhury et al (1976) for Clostridium botulinurn 62A spores.…”

“…Ehioba et al (1988) agreed with this and reported a similar microfloral shift in irradiated (1.0 kGy), vacuum-packaged ground pork stored at 5°C. A parallel study by Ehioba et al (1987) also showed mesophilic, psychrotrophic, and anaerobic and facultative anaerobic bacteria were greatly reduced by irradiation at 1.0 kGy, so that shelf life in vacuum-packaged, irradiated ground pork stored at 5°C was extended by 40% to 70%.…”

Physical, Chemical and Sensory Changes in Irradiated Fresh Pork Packaged in Modified Atmosphere

“…For the remainder of storage TBA values remained approximately constant and there was no difference between all non-irradiated samples and N,-packaged samples irradiated at 1 kGy. These observations were in confirmation of those of Mattison et al (1986) and Ehioba et al (1987) who showed that the TBA values of vacuum-packaged pork loin and ground pork were not affected by irradiation at 1 kGy. Similarly, Lebepe et al (1990) reported that an irradiation dose of 3 kGy did not affect TBA values of vacuum-packaged pork loin.…”

Physical Methods for Cleaning and Disinfection of Surfaces

“…Shelf life of poultry was extended from 6-10 to 12-20 days after 2.5 kGy radiation by Molins [143], and a three orders of magnitude viable count reduction was achieved for frozen (3-5 kGy) and chilled (1.5-2.5 kGy) poultry without loss of sensory quality [144,145]. A dose of 1 kGy extended shelf life of vacuum-packed ground pork by 40-70% [146], and that of cooked shrimps by a factor of three [147].…”