Raw Pork Snack Offers Food Preservation Lessons

A traditional Vietnamese meat snack could be the key to developing a safe and natural food preservative, tackling the global twin problems of food waste and foodborne illness.

The fermented pork snack, Nem Chua, is eaten raw but does not cause food poisoning when prepared properly.

This is because the good bacteria that thrive in fermented meat form a special compound that destroys the most dangerous bacteria.

Now researchers from RMIT University in Melbourne, Australia have shown how this natural bacteria-killing compound can be used to keep food fresh longer.

Food waste is a global problem that costs around $680 billion a year in industrialized countries, consumes almost a quarter of the water used in agriculture and produces 8% of global greenhouse gas emissions.

Foodborne illnesses such as Listeria or Salmonella affect millions of people every year and can put the lives of pregnant women, the elderly and immunocompromised people at risk.

Co-lead researcher Professor Oliver Jones said changes in consumer habits have led to greater demand for natural alternatives to artificial food preservatives.

“Scientists have known about these bacteria-killing compounds for many years, but the challenge is to produce them in sufficient quantities to be used by the food industry,” said Jones, associate dean of food biosciences and technology at RMIT.

“The Nem Chua compound is colorless, odorless, tasteless and very strong.

“Thanks to this new research, we have identified the right growing conditions that would allow us to produce it in large quantities, potentially on an industrial scale.

“With further development, we hope this could be an effective, safe and all-natural solution to food waste and foodborne illness.”

Bacteria killer weapon

A team of RMIT researchers were inspired to investigate Nem Chua for its potential antibacterial properties after traveling to Vietnam and observing people eating the raw meat snack without getting sick, despite the hot and humid climate.

The team, led by Professor Andrew Smith (now at Griffith University) and Dr Bee May, discovered a new type of bacterial compound in Nem Chua.

Plantacycline B21AG is one of a group of compounds known as bacteriocins, which are produced by bacteria to destroy rival bacterial strains.

Bacteriocins form holes in the membranes of target bacteria. This causes the contents of the cell to leak out, effectively killing the bacteria.

The problem is that most bacteriocins only work against one or two types of bacteria and they are not very stable under different environmental conditions.

Only one – nisin, which came to market in the 1960s – is currently licensed for use as a food preservative, with an estimated market of over $513 million in 2020, but this compound is temperature sensitive and to pH, which limits its use.

Robust and efficient

The Nem Chua-derived compound is more robust than nisin and is effective against a wide range of bacteria, even after exposure to a range of typical food processing environments.

It can survive being heated at 90°C for 20 minutes and remains stable at high and low pH levels.

The compound can also destroy a range of disease-causing organisms commonly found in foods, including potentially deadly Listeria, which can survive refrigeration and even freezing.

Co-principal investigator Dr Elvina Parlindungan, who completed the new study as part of her doctoral research at RMIT, is now a postdoctoral fellow at APC Microbiome, part of University College Cork in Ireland.

“The effective use of bacteriocins as food preservatives means we turn the toxic weapons of bacteria against them – harnessing nature’s smart solutions to our big challenges,” Parlindungan said.

“In the future, these compounds may also be useful as an antibiotic in human medicine.”

Researchers at RMIT’s School of Science have begun experimenting with methods to further purify the compound and plan to incorporate it into test food products.

Reference: Parlindungan E, Dekiwadia C, Jones OAH. Factors that influence growth and bacteriocin production in Lactiplantibacillus plantarum B21. Process biochemistry. 2021;107:18-26. doi:10.1016/j.procbio.2021.05.009

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