Inhibitory effect of enterocin with some food additives on Escherichia coli O18 in UHT milk

الملخص EN

Biopreservation is the oldest method for food preservation by addition of natural compounds to the food to increase its shelf-life and inhibit the growth of foodborne pathogens.

Enterocin is a protein produced by Enterococcus faecium which have a great effect on Gram-positive bacteria, but it has limited effect on Gram-negative bacteria.

The aim of this work is to study the addition of food additives as honey and EDTA to increase the inhibitory effect of enterocin against Escherichia coli O18 in UHT milk stored at ambient and refrigerator temperatures.

The UHT milk inoculated with E.

coli O18 was divided into 8 parts as the following, the first part without any additives as control, the second with 10% honey, the third and fourth parts contained 10% honey with different concentrations of enterocin (150 and 300 μg/ml), respectively.

Each part of these prepared four parts was divided into two groups; the first group was stored at ambient temperature (30±2 °C) while, the second group was stored at refrigerator temperature (4±2 °C) for 24 hours.

The obtained results showed that, the most effective treatment was the 10% honey and enterocin (300μg/ml) and stored in the refrigerator where the count of E.

coli O18 reduced from 6x106 cfu/ml to 7.1x104 cfu/ml at the end of 24 h.

Also, another trail was done as the previous experiment except the replacement of the honey with EDTA (20 mM).

The highest inhibitory effect of the treatments obtained by the addition of EDTA (20mM) with enterocin (300 μg/ml) which was stored at the refrigerator temperature.

The count of E.

coli O18 was reduced from 1.5x105 cfu/ml to 3.6x104 cfu/ml by the end of 24 h.

In conclusion, the addition of honey or EDTA with enterocin and preservation of milk in refrigerator temperature reduced E.

coli O18 count.

In addition, this method can be used as a safe method for preservation of milk which consumed directly or used in manufacture the milk products.