RMIT Scientists Uncover Nutritional and Sustainable Benefits of Native 'Old Man Saltbush'

Food scientists at RMIT University have investigated 'Old Man Saltbush' (Atriplex nummularia), a native plant traditionally consumed by Indigenous Australians. The research indicates that saltbush is nutrient-dense, high in protein and fibre, can function as a salt replacer, and is resilient to various climate conditions.

Dr. Mahsa Majzoobi, a Senior Lecturer in Food Technology and Nutrition at RMIT, led the research team. The team's work focuses on the physical and chemical properties of plant-based ingredients and their applications. Dr. Majzoobi noted that despite its traditional use and interesting nutritional profile, Old Man Saltbush remains underutilized as a human food source.

The Research Study

The study examined the integration of saltbush powder into wheat flour noodles at concentrations of 0%, 2.5%, and 5%, both with and without added sodium chloride (0% and 3%). This assessment aimed to determine its potential as a functional ingredient and natural salt replacer. The findings were published in the journal Food and Bioprocess Technology.

A Nutritional Powerhouse

Analysis revealed that saltbush powder contains over twice the protein content and eight times more dietary fibre compared to wheat pasta. Saltbush features 20-25% protein, with a protein quality that closely aligns with the amino acid requirements for human nutrition.

Incorporating saltbush could assist in addressing global fibre intake deficiencies, which are associated with cardiovascular diseases, type 2 diabetes, and certain cancers.

The plant is also rich in essential minerals such as calcium, iron, phosphorus, zinc, and sodium, which are often absent or negligible in wheat flour. These minerals are important for addressing nutritional deficiencies, including those prevalent in developed countries like Australia, such as calcium, iron, and zinc deficiencies in young females. Furthermore, saltbush contains high levels of bioactive compounds and antioxidants, which support healthy cell function.

Role as a Salt Replacer

The research suggests that saltbush protein could help reduce dietary sodium intake. The World Health Organization (WHO) recommends less than 2,000 mg of sodium per day, while the global average intake is approximately 4,300 mg/day, a level strongly linked to adverse health outcomes like high blood pressure and cardiovascular diseases.

As a halophytic plant, saltbush naturally contains both sodium and potassium chloride. This composition allows it to contribute saltiness to food without solely relying on sodium chloride.

The study demonstrated that saltbush performed effectively as a salt replacer in food formulations.

For example, wheat noodles containing 5% saltbush powder but no added sodium chloride had approximately 140mg of sodium per 100g. This level slightly exceeded the Food Standards Australia New Zealand (FSANZ) "low-sodium" threshold (≤ 120 mg/100 g). In contrast, noodles with 3% added sodium chloride contained approximately 1320mg of sodium per 100g, classifying them as "high-sodium" (> 600 mg/100 g) under FSANZ guidelines.

Environmental Sustainability

Saltbush's halophytic properties contribute to its sustainability, making it resilient to climate challenges. It can thrive in unsuitable conditions, offering a potential food source in drought-prone regions and requiring less water compared to mainstream grains such as rice. This resilience is significant as global climates become more variable.

Future Directions

The research team plans further investigations into saltbush, including its incorporation into common foods like breads and savoury snacks, and the extraction of its proteins and bioactive compounds. The overarching goal is to support the development of Australian-grown, climate-resilient ingredients to foster healthier and more sustainable food systems.