Nisaplin® in pasteurised liquid egg

Abstract presented at the International Egg Forum 2007 (Belgium). Our gratitude to authors and organizers, especially Mr. Michael Grech and Agra Informa Ltd., for their kind collaboration.

Use of Nisaplin® as a preservative in pasteurised liquid egg products - Image 1

Use of Nisaplin® as a preservative in pasteurised liquid egg products - Image 1

It is a mandatory requirement that pasteurised liquid egg products are sufficiently heat processed to ensure the destruction of Salmonella.

However, some bacteria especially those that produce heat resistant spores will survive and grow at low temperatures.

The use of a safe natural preservative that will control the growth of heat resistant bacteria and allow increase in the shelf life of pasteurised liquid egg products would be of considerable interest to the egg industry.

Furthermore some heat resistant bacteria capable of growth at low temperature, notably Bacillus cereus, are food poisoning bacteria and their growth in liquid egg products could present a health hazard and compromise the reputation of the industry.

Nisaplin® is the commercial preparation of the bacteriocin nisin (E234) and is considered a safe and natural preservative.

The presentation will describe the unique properties of nisin and its use a preservative in pasteurised liquid egg.

Nisin use as a preservative in pasteurised liquid egg products has been improved in the USA, Australia, and New Zealand.

In late 2006 the European Food Standard Agency (EFSA) ruled “that the use of nisin in pasteurised liquid egg posed no health hazard”.

The EU will decide whether it can be used as a preservative can be extended for used in pasteurised liquid egg in 2008.

Nisin: history

1930s
Cheesemakers in the UK experienced problems due to an unknowninhibitory substance in milk preventing the growth of starter cultures

1940s
Inhibitory substance was found to be produced by certain strainsof Lactococcus lactis (Lancefield Group N).
Substance isolated & identified as a small antimicrobial polypeptide.
Given the name nisin, derived from “N Inhibitory Substance”

1950s
Lab studies and commercial trials with crude liquid preparations ofnisin.
Found to be unsuitable for medical & veterinary applications.
Some success in controlling growth of gas producing Clostridium incheese.

1960s
Starting point for commercial application & development asa food preservative

Bacteriocins: definition

Extracellularly released, ribosomally-synthesised, low molecular weight peptides or protein complexes that in low concentrations are able to kill ‘closelyrelated’ bacteria.
The producer bacteria are immune.
The most well known bacteriocin is nisin.
This has broad spectrum activity against Gram positive bacteria.

Nisaplin® Natural Antimicrobial

A commercial extract of the bacteriocin, nisin
Standardised potency (106 IU/g ) by addition of salt
Produced at Danisco’s Beaminster UK site, by a sugar - based fermentation using the dairy starter culture bacterium Lactococcus lactis
Authorised as a food additive in over 50 countries worldwide. FAO/WHO approval. E234. GRAS status
Can extend shelf life of food and protect against temperature abuse
Major applications in processed cheese and pasteurised dairy foods

The realisation of Nisin as a food preservative

Nisin was used as a food preservative because:

Nisin is non toxic
The producer strain L. lactis is regarded as safe (food-grade)
There is no apparent cross-resistance related to therapeutic antibiotics
It is degraded immediately during digestion
It is heat stable at low pH

The first commercial preparation of nisin (Nisaplin®) was made in 1953 by Aplin & Barrett Ltd. (now Danisco).

Originally intended only to control clostridial spoilage in processed cheese, the application was so successful it lead to worldwide interest
In 1969 a joint FAO/WHO expert committee on food additives recognised nisin as a safe and legalfood additive

Nisaplin® : composition

Appearance:

Average composition:
2.5%
90%
4%
1.5%
2%

Shelf life:

Free flowing white powder

nisin
sodium chloride
protein
carbohydrate
moisture

2 years at 4°C to 25°C

Nisin A: structure

Nisin Z contains asparagine instead of histidine at position 27
Use of Nisaplin® as a preservative in pasteurised liquid egg products - Image 2

Use of Nisaplin® as a preservative in pasteurised liquid egg products - Image 2

Nisin mechanism of activity

Vegetative cells
Nisin adsorbs to the cytoplasmic membrane where it forms transient pores
Low molecular weight compounds leak from the cell causing loss of energy
The pH gradient across the membrane becomes dissipated
Collapse of the proton motive force (which drives ATP synthesis- the cell’s energy)

Heat-resistant endospores

Nisin affects spores after germination, preventing their outgrowth
Does not normally kill bacterial spores

Nisin mode of action against the cytoplasmic membrane

Nisin (

) binds to the carbohydrate moiety of the cell wall precursor lipid II (

) , using it as a docking molecule prior to pore formation.
Diagram of cell membrane showing phospholipid bilayer (

)

Use of Nisaplin® as a preservative in pasteurised liquid egg products - Image 6

Nisin: mode of action against bacterial spores

Inhibition of pre-emergent swelling of spores

Use of Nisaplin® as a preservative in pasteurised liquid egg products - Image 7

Use of Nisaplin® as a preservative in pasteurised liquid egg products - Image 7

What does Nisaplin® do?

Controls heat-resistant bacteria in pasteurised, sterilised and UHT food products.
Controls the growth of lactic acid spoilage bacteria
Controls the growth of Listeria monocytogenes

What it doesn’t do……

It does NOT control yeast and moulds - Natamax™ can control these
It does NOT control Gram-negative bacteria
– Usually destroyed by the processes used in manufacture of heattreated foods
It does NOT cover up the use of poor quality raw materials, or poor hygiene

Important considerations to ensure good preservation

Nisin works in a concentration dependent fashion
- increasing bacterial cell or spore loads will require higher nisin concentrations to achieve effective inhibition
Nisin cannot be used to hide poor manufacturing practice
Nisin added to a food system will naturally and slowly degrade during shelf life depending on the storage conditions and food type
For a continued inhibitory or sporostatic effect, there must be sufficient nisin remaining within the food system at the end of the required shelf life

Pasteurised Liquid Egg Products

Large scale production of liquid whole egg, white and yolk for industrial manufacturers.
Trend toward whole egg in 1 kg or smaller containers for retail sale/catering supply.

Ingredients	Raw eggs in shell, egg cracked, white and yolk mixed together, typical pH 7.3 - 7.8.

Process	Liquid egg pasteurised, minimum 64.5°C for 2½ minutes (to kill Salmonella spp). "Clean" or aseptic filling into cartons (1kg / 500g / 250g).

Products	Retail cartons, chilled (2-4°C) shelf life of 3 weeks or more.

Problem	Heat resistant bacterial spores (including Bacillus cereus). Growth during shelf life causing spoilage especially under abuse storage.

Effectiveness of Nisaplin® in liquid egg

Use of Nisaplin® as a preservative in pasteurised liquid egg products - Image 8

A further trial

Use of Nisaplin® as a preservative in pasteurised liquid egg products - Image 9

EFSA rule on safety

Use of nisin in liquid eggs 'not a safety concern'
By Anthony Fletcher

06/12/2006 - Extending the use of the additive nisin to cover thepreservation of liquid eggs does not pose a safety concern, says EFSA.

Extracted from Food Navigator 2007