Main conclusions

Egg mass packaged using only CO2 and in combination with high-pressure processing resulted in long shelf life compared to an untreated control product.

Background

High-pressure processing (HPP) has many applications and can be used on a variety of products. In order to achieve pasteurisation conditions and extended shelf life, one often has to use pressure less than 400 MPa, as this ensures safe products with high inactivation of bacteria.

Processing at such high pressures can affect both colour and texture, making HPP less relevant regarding use on raw fish and raw meat. If one can combine the high-pressure treatment with other treatments, so that the product receives an extended shelf life at lower pressures, this will be positive for a number of food products, and could also result in higher product quality. In addition, the use of lower pressure will result in lower energy costs and significantly less wear and tear on the high-pressure equipment. Therefore, this could be profitable on several levels.   

In previous trials that focused on Listeria, we have shown good inactivation effects by combining high pressure (<400 MPa) and packaging with CO2 gas.

In these trials, we have packaged egg mass in CO2 and then processed it using different pressures (300, 350, 400 and 600 MPa, 2 min). We have also tested the effect of CO2 under supercritical conditions at high pressure. This is a field in which very little research has been conducted, and our results are promising.

Purpose of the trial

Investigate whether the effect of combining milder pressure (<400 MPa) and packaging in CO2 resulted in extended shelf life of an egg mixture compared to an untreated control sample.

Methodology

Chicken eggs were cracked, and egg white and egg yolk were lightly mixed. The egg mass was distributed in bags and subjected to various treatments:

1. Vacuum sealed
2. Packaged with CO2 gas and sealed
3. Vacuum sealed and high-pressure processed
4. Packaged with CO2 gas, sealed and high-pressure processed
5. Packaged with CO2 gas, sealed and high-pressure processed under supercritical conditions for CO2

Samples received different high-pressure treatments; 300, 350, 400 and 600 MPa, with a holding time of 2 min.

The following was investigated

Microbiology

• Packaging using only CO2 resulted in good shelf life
• Packaging in CO2 and high-pressure processing resulted in good shelf life
• Using only high-pressure processing at 600 MPa resulted insatisfactory shelf life
• High-pressure processing with high CO2 under supercritical conditions did not result in statistically significant differences compared to high-pressure processing with high CO2