Pulsed light could inactivate Salmonella in liquid eggs

By Jane Byrne, 16-Jan-2009

Source of Article: http://www.foodproductiondaily.com/Quality-Safety/Pulsed-light-could-inactivate-Salmonella-in-liquid-eggs

A new study claims pulsed electric field (PEF) combined with heat treatment may have an advantage over high-temperature treatment for pasteurisation of liquid whole egg (LWE).

According to the authors of the study, which was published in the International Journal of Food Science and Technology, PEF exposes a fluid or semi-fluid product to short pulses of high-energy electricity, which can inactivate microorganisms.

PEF processing, the research team claims, causes minimal or no detrimental effect on food quality attributes.

The scientists said that occurrences of egg-related outbreaks of Salmonellosis have heightened the concern for the safety of egg-related products, with the food industry now exploring various methods of killing harmful pathogens while trying to maintain quality.

Quality impairment

According to the authors, heat sterilisation techniques, while common, can also lower quality.

At present, LWE is pasteurised in the US at a minimum of 60 C for 3.5 minutes to ensure microbiological safety, while, in the UK, the regulatory requirement for LWE is 64 C for 2.5 minutes, but according to the research team, previous studies have shown that egg white functionality is impaired when heated for several minutes above 57 C.

The scientists said that, therefore, it would be desirable to have a new and improved processing technique for improving the safety of liquid egg products.


In this study, effects of PEF, temperature, pH and PEF with mild heat on the inactivation of Salmonella typhimurium cells in liquid whole egg (LWE) were investigated, said the authors.

They explained that cells of Salmonella typhimurium DT104 were chosen because they were considered a dangerous phage type that was resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline.


The authors found that the effectiveness of PEF pasteurisation to inactivate pathogenic S. typhimurium DT104 in liquid egg relied on the pH of the liquid egg and the treatment temperature:

The PEF inactivation of S. typhimurium cells at 15 or 25 C was pH dependent. Heat treatment at 55 C for 3.5 minutes or PEF treatment at 20 C resulted in c. 1-log reduction of S. typhimurium cells.

The researchers said that increasing treatment temperature at neutral pH enhanced the effectiveness of PEF treatment, and the blend of PEF treatment with mild heat reduced liquid egg pasteurisation temperature while achieving similar reduction of the pathogen.

The combination of PEF + 55 C achieved 3-log reduction of S. typhimurium cells and was comparable to the inactivation by the heat treatment at 60 C for 3.5 min, said the authors.

The researchers concluded that their study demonstrated a possible approach to increase the efficiency of PEF in microbial reduction in liquid eggs, and that other studies have indicated that the addition of bactericides increased the efficiency of PEF processing.

They said, therefore, with further development or modification, PEF processing could have offer food manufacturers greater benefits over high-temperature pasteurisation in ensuring the microbial safety of liquid eggs with a minimal loss of quality attributes.

Source: International Journal of Food Science and Technology, Volume 44, Issue 2
Published online ahead of print
Title: Effects of pH and temperature on inactivation of Salmonella typhimurium DT104 in liquid whole egg by pulsed electric fields
Authors: T. Jin, H. Zhang, N. Hermawan, W. Dantzer



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