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Food scientists at RMIT have studied native plant ‘Old Man Saltbush’ (Atriplex nummularia), traditionally consumed by Indigenous Australians, and found it to be incredibly nutrient-dense, and high in protein and fibre. It can also act as a salt replacer, and is climate-resistant.
InSight+ spoke to the lead researcher about studying a new superfood.
Dr Mahsa Majzoobi is a Senior Lecturer in the Department of Food Technology and Nutrition at RMIT University, and the Vice Chancellor’s Senior Research Fellow at RMIT’s Food Research and Innovation Centre.
Dr Majzoobi and her team analyse the physical and chemical properties of plant-based ingredients, and their functional applications.
“We chose saltbush after visiting a plant farm in Albury, NSW. The owners explained that Old Man Saltbush has been used by Australian Indigenous people for thousands of years. But nowadays it’s mostly used as animal feed,” said Dr Majzoobi.
“I wondered, why are we not using it as human food [on a larger scale]? I found previous studies had been done, and the very interesting nutritional profile of this plant has been discussed and explained many years back. But it is still underutilised.”
“We did nutritional profiling and food applications. Saltbush is very interesting: it’s nutritious, environmentally friendly, available, and it can be used in our ordinary food. It ticks all the boxes. The direction now is, how can we use it in everyday foods?”
The study evaluated the incorporation of saltbush powder into wheat flour noodles (adding saltbush powder at rates of 0%, 2.5%, and 5%), and both with and without added sodium chloride (0% and 3%), assessing its potential as a functional ingredient and natural salt replacer.
The study was published in Food and Bioprocess Technology.
Impressive nutritional benefits
The researchers found that saltbush has an impressive nutritional profile.
“Our analysis showed saltbush powder contained more than double the protein content of wheat pasta, and was eight times higher in dietary fibre,” said Dr Majzoobi.
“In terms of protein, it’s interesting because nowadays there is a shift from animal-based proteins towards plant-based proteins. Saltbush has 20-25% protein.”
The study found that the protein quality of saltbush nearly matched the ideal amino acid requirements for human nutrition.
“We’re also lacking in fibre intake globally, and in Australia. The recommendation for fibre intake is about 25-30 grams per day. But we generally — especially as young adults — usually don’t get that amount.”
“That links with the development of cardiovascular diseases like obesity, and type 2 diabetes, and some cancers.”
“And if we think of this novel, available, cheap, environmentally-friendly plant, that justifies further investigating, and producing protein extracts from saltbush for the health food shelves in the supermarkets.”
The study found that, among other benefits, saltbush powder is rich in minerals such as calcium, iron, phosphorus, zinc, and sodium, whereas those minerals are either absent or negligible in wheat flour.
“Saltbush is a good source of minerals. And that’s really interesting in addressing malnutrition, which we have even in developed countries like Australia.”
“Our intake of calories is quite high, but mineral deficiency — especially in young females – calcium, iron, and zinc deficiency are major problems.”
“Another interesting point is saltbush is quite high in bioactive compounds, and antioxidants, which are needed for healthy cell function and growth.”
Salt: both friend and foe
Dr Majzoobi said that using saltbush protein could be used to reduce sodium intake in the average diet.
“We know the strong correlation between sodium intake and the high blood pressure that can result in different types of cardiovascular diseases. At the moment, salt intake is much higher than the recommended numbers.”
In the study, the researchers highlight that the World Health Organisation (WHO) recommends adults consume less than 2 000 mg of sodium per day, as higher intake is strongly associated with ill health, and that currently, the global average sodium intake is approximately 4,300 mg/ day.
“It’s a bit difficult, because salt contributes to food’s sensory properties. It contributes to the texture, and to many other functional properties of food. So its presence is important. Fortunately, there are salt replacers, similar to sugar replacers,” said Dr Majzoobi.
As a halophytic plant (a plant with high salt tolerance), saltbush has a chemical makeup that means it can act as a ‘salt replacer.’
“This salt replacer is commonly known as potassium chloride, which has saltiness, but also doesn’t have that adverse effect on blood pressure or some cardiovascular issues.”
“Saltbush is really interesting because when we looked at the chemical composition, we found that it has salt, because it is grown in saline areas, but also it has a good amount of potassium chloride. The saltiness coming from saltbush is not just because of the sodium chloride.”
“Salt replacers are not highly competitive with sodium itself. But it is really interesting if we can replace them and produce formulations with hybrid salt, so we can reduce the sodium chloride salt as the main salt, and also add a little bit of this salt replacer.”
“It performed very well in our studies.”
The team found that in the wheat noodles containing 5% saltbush powder, but containing no added NaCl (sodium chloride), the sodium content was approximately 140mg per 100 g.
The researchers highlight that the value slightly exceeded the Food Standards Australia New Zealand (FSANZ) threshold for “low-sodium” classification (≤ 120 mg/100 g), which meant the product could not be labelled as such, despite not containing added salt.
The noodles containing 3% NaCl (sodium chloride), however, were shown to have a sodium content of approximately 1320mg per 100g, which categorised the product as “high-sodium” under FSANZ guidelines (> 600 mg/100 g).
Sustainability as health
On top of its other benefits, the fact that saltbush is halophytic makes it incredibly sustainable.
“Globally we are moving towards more drought, more episodes of no rain in Australia. Thinking ahead and finding food that can still feed the country – or even for overseas export – can be a win,” said Dr Majzoobi.
“It is important, because there are many other mainstream grains such as wheat, rice, even corn, in Australia that need specific climate conditions for the best growth. We are looking for wheat varieties that are naturally resistant to climate shocks. But it’s very difficult to find them.”
“They need a lot of attention. At the same time rice, for example, needs a lot of water. ”
“But resilient crops such as saltbush can grow in unsuitable conditions very well.”
Dr Majzoobi said that her team is planning further explorations of saltbush and its potential.
“I’m very excited, because we’ve just started working on this. We’re trying to increase the intake through normal foods. We’re aiming, for example, to include it in breads, and different savoury products like snacks. Or even extracting different things from it, including protein, or bioactive compounds.”
“Ultimately, our goal is to support the development of Australian-grown, climate-resilient ingredients that contribute to healthier and more sustainable food systems.”
The team’s research was funded by RMIT Vice-Chancellor’s Senior Research Fellowship, and The Enabling Impact Platform for Sustainable Technologies and Systems.
Becca Whitehead is a freelance journalist and health writer. She lives in Naarm and is a regular contributor to the MJA’s InSight+.
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