Shelf life extension of liquid whole eggs by heat and bacteriocin treatment

Abstract

During a 15-month period, samples of commercially pasteurised liquid whole egg (LWE) were tested for the presence of spoilage microflora. The total bacterial counts were 2.2 ± 0.6 log CFU/g and total lactic acid bacteria (LAB) counts were 1.9 ± 0.6 log CFU/g. Enterobacteriaceae were detected in 2 samples. Out of the tested samples, 45 LAB were isolated and identified, with 30 strains identified as Enterococcus faecium, 12 as Enterococcus faecalis, and 3 as Lactobacillus paracasei subsp. paracasei. All strains, except 6 strains of E. faecium, possessed lipolytic activity. All the E. faecalis strains and one strain of E. faecium showed a high proteolytic activity, while moderate proteolytic activity was shown by 3 lactobacilli strains. Minimum inhibitory concentration (MIC) of nisin and Micocin X was measured against groups of isolated strains, and ranged from 10.4 µg/ml to 41.7 µg/ml for nisin and from 0.2 mg/ml to 1.6 mg/ml for Micocin X. The LWEs supplemented with 6.25 mg/l of nisin or with 500 mg/ml of Micocin X were pasteurised at 65°C for 2.5 minutes. The shelf life of LWE with the addition of nisin or Micocin X stored under refrigerator conditions was extended by a minimum of 5 weeks.