Sukirtha Srivarathan

Increased salt (sodium chloride (NaCl)) consumption contributes to high blood pressure, increasing the risk of cardiovascular disease. Reducing the intake of NaCl could result in significant public health benefits. Australian grown halophytes are consumed traditionally by indigenous communities as food and medicine. The importance of halophytes has been recently “rediscovered” due to their salty taste and crunchy texture. This study aimed to assess the potential of Australian indigenous edible halophytes (AIEH) as salt substitutes. A benchtop test was carried out to establish a sensory lexicon of four important AIEH (samphire, seapurslane, seablite, and saltbush) and to select the most promising halophyte based on sensory attributes and nutritional composition. Samphire and saltbush, the most common and commercially important halophytes, were used as comparisons. Semolina was used to prepare the halophyte‐based test food for the benchtop sensory study. Results of the formal sensory study showed that the growing location of samphire and saltbush can significantly affect their sensory attributes. Samphire had the most favorable sensory attributes and nutritional quality, with dry herb and bran aroma and flavor, whereas the saltbush test food preparations had herbaceous , minty dry wood , and green fruit aroma and flavor. The “optimal” concentration of added freeze‐dried samphire/saltbush powder was determined based on the saltiness perception of the NaCl‐semolina formulation (0.3% table salt equivalent to 1% samphire freeze‐dried powder and 1.4%–2.0% saltbush freeze‐dried powder, respectively). This study provided novel and crucial information on the potential use of AIEH as natural salt substitutes. Practical Application: There is an increasing demand for natural salt substitutes. Halophytes are salt tolerant plants that sustain in arid or semiarid areas and have the potential to be used as natural salt substitutes. To the best of our knowledge, this is the first study reporting the sensory profiles of four important Australian indigenous edible halophytes (samphire, seapurslane, seablite, and saltbush). This study also demonstrated how different growing locations can affect the sensory attributes of halophytes and subsequently their potential food applications. Our findings provide critical information and data to further study halophytes in the context of novel food applications.

Halophytes are considered emerging functional foods as they are high in protein, minerals, and trace elements, although studies investigating halophyte digestibility, bioaccessibility, and intestinal absorption are limited. Therefore, this study investigated the in vitro protein digestibility, bioaccessibility and intestinal absorption of minerals and trace elements in saltbush and samphire, two important Australian indigenous halophytes. The total amino acid contents of samphire and saltbush were 42.5 and 87.3 mg/g DW, and even though saltbush had a higher total protein content overall, the in vitro digestibility of samphire protein was higher than the saltbush protein. The in vitro bioaccessibility of Mg, Fe, and Zn was higher in freeze-dried halophyte powder compared to the halophyte test food, suggesting that the food matrix has a significant impact on mineral and trace element bioaccessibility. However, the samphire test food digesta had the highest intestinal Fe absorption rate, whereas the saltbush digesta exhibited the lowest (37.7 vs. 8.9 ng/mL ferritin). The present study provides crucial data about the digestive “fate” of halophyte protein, minerals, and trace elements and increases the understanding of these underutilized indigenous edible plants as future functional foods.

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Salinization is gradually increasing over cropping soils and is challenging Governments in many countries, including Australia. There has been a high demand for utilizing arid and semi-arid land for sustainable food production. Currently, the main crops and forage plants are salt sensitive, while halophytes can tolerate a wide range of salinities. Samphire is an Australian indigenous edible halophyte and belongs to the genus Tecticornia. It is an underutilized, succulent plant growing on arid or semi-arid land. Most samphire species have a long history of use as food, but also as non-food (fodder and medicine), among indigenous communities in Australia, while scientific information is limited on their nutritional composition and potential bioactivity. The present study reports, for the first time, the nutritional composition, bioactive compounds (phytochemicals) and antioxidant capacity of six Australian grown samphire from different locations. The results showed that celosianin II and isocelosianin II could be identified as the predominant betalains (phytochemicals) in pigmented samphire species. Proximates and fiber varied significantly (p < 0.05) between the samphire species with a highest value of fiber of 46.8 g/100 g dry weight (DW). Furthermore, samphire could be identified as a valuable source of essential minerals and trace elements, such as iron (41.5 mg/100 g DW), magnesium (1.2 g/100 g DW) and sodium (16.7 g/100 g DW). The fatty acid profile, mainly palmitic, stearic, oleic, linoleic and α-linolenic acid, was similar among the studied species. Total phenolic content and DPPH-radical scavenging capacity were different (p < 0.05) between the six samphire samples. These initial results are very promising and indicate that Australian grown samphire may have the potential to be utilized as a functional food ingredient.

In recent years, edible halophytes have received more attention due to their ability to tolerate a wide range of salinities. In Australia, halophytes are used in a broad range of applications by Indigenous communities—in traditional cuisine, as livestock feed, and for soil bioremediation. However, very limited scientific information is available on the nutritional profiles and potential bioactivity of halophyte species. Therefore, the present study assessed the nutrient and phytochemical composition of Australian-grown Seapurslane (SP) (Sesuvium portulacastrum), Old Man Saltbush (SB) (Atriplex nummularia), and Seablite (SBL) (Suaeda arbusculoides) to better understand their nutritional value and potential bioactivity. SB and SP contained more (p < 0.05) fibre than commercial Australian baby spinach (same plant family) which was used as a reference (41.5 vs. 40.4 vs. 33.4 g/100 g dry weight (DW)). Furthermore, these plants can be considered as valuable sources of essential minerals (Ca, Fe, Mg and Na) and trace elements; specifically, SBL had the highest content of Ca and Fe. SB had the highest protein (20.1 g/100 g DW) and fat (2.7 g/100 g DW) content compared to the other studied halophytes. The fatty acid profile consisted mainly of palmitic, stearic, oleic, linoleic, and α-linolenic acids. A strong antioxidant capacity (total phenolic content and DPPH radical scavenging capacity) indicated that (poly) phenolic compounds are most likely the predominant phytochemicals in this species. These initial results are promising and suggest that Australian indigenous edible halophytes may have the potential to be utilized as functional food ingredients.

Plant foods play a vital role in human nutrition due to their diverse range of macro- and micro-nutrients, fibre and phytochemicals. However, more than 90% of the plant-food demand is satisfied by less than 0.1% of the edible plant species available. Moreover, none of the highly consumed ‘food-plants’ can survive without freshwater irrigation. As the world’s population rises and food sources become limited, alternative avenues for satisfying the world’s food demand are necessary. This persistent situation urges the domestication of wild terrestrial salt tolerant (halophytes) edible plants, of which saltbush (SB) was found to have a long history of use as animal feed and soil erosion control, while very little scientific information is available on its nutritional profile and dietary relevance. Therefore, the present study assessed the nutrient and phytochemical composition of Australian grown oldman SB (Atriplex nummularia) leaves to better understand its nutritional ‘value’ and potential bioactivity. The proximate results showed that SB leaves were rich in protein (20.1 ± 0.18 g/100 g DW), fibre (41.5 ± 0.20 g/100 g DW) and minerals (particularly Ca (1.44 ± 0.03 g/100 g DW), Na (4.13 ± 0.02 g/100 g DW), Mg (0.90 ± 0.01 g/100 g DW), and Fe (11.68 ± 0.35 mg/100 g DW). These initial findings provide important nutritional information to a very promising plant source that could be used alone or synergetic with other foods (e.g., alternative protein and/or fiber source, potential salt substitute). However, further studies need to be carried out to determine the complete nutritional profile of oldman SB leaves, the bioaccessibility/bioavailability of its main nutrients and phytochemicals as well as consumer acceptance in order to develop SB based food products.