What is moringa leaf powder?

Moringa oleifera is a fast-growing, tropical tree known for its nutritious leaves, eaten raw, cooked, or dried and ground into powder (Figure 1). Here we’ll focus on moringa leaf 1 powder, which is easy to store and add to foods. The ability to store moringa powder allows people to benefit from moringa during times such as the dry season when moringa trees are less productive. Added in modest amounts, moringa powder does not appreciably alter the taste of the food and is an excellent way to boost the nutrition of local dishes. Questions arise about how best to process the leaves for quality moringa powder. This article expands on an earlier ECHO publication (Doerr and Cameron, 2005), summarizing factors before and during drying that influence the quality of moringa leaf powder. It also discusses drying methods and practical ways to optimize post-harvest processing for improved nutritional quality.

How are moringa leaves prepared for drying?

Moringa leaves need to be dried before converting them into powder. Wearing gloves while handling leaves is good practice for producing clean moringa powder. Sanitation is especially important if you are producing moringa powder for others. If you are producing moringa powder for a business, be aware of required practices and standards for acceptable quality. Table 1 covers the basic steps to harvest, wash, and prepare moringa leaves for drying.

Table 1. Steps in gathering and preparing moringa leaves for drying. Photos by Tim Motis

1		Harvest the leaves using hygienic practices. Wash your hands before harvesting the leaves. Leaf handling during the next steps is easiest if you harvest them in bundles with stem ends all together on one end of each bundle. The stem ends then serve as a handle by which you can grasp each bundle.
2		Wash the leaves. Fill a clean bucket or trough with clean water. Submerge the leaves in the water, swishing them around in the water to wash off dust and debris. Empty the water and wash the leaves once or twice more. If your water is chlorinated, the chlorine will act as a disinfectant to reduce germs. An alternative to chlorine is a 3-to-5-minute dip of the leaves into a 1% salt solution (Sauveur and Broin, 2010).
3		Remove water droplets off the leaves. Grasp a bundle of leaves by the stem ends and shake the water off with a downward swooping motion. You could then spread the leaves out on a cloth or towel to absorb more water. Alternatively, place the leaves in a strainer and allow excess water to drain off the leaves.
4		Strip leaflets from the petiole. Nutrients tend to be more concentrated in the leaflets (Anjorin et al., 2010; Osumah, 2019) than in the leafstalk (petiole) tissues that leaflets are attached to. It may not be practical to remove individual leaflets but exclude as much leafstalk tissue as you can. Strip the leaves using a grasping and pulling motion. Exclude most of the fibrous leafstalk tissue by stripping leaves off individual “branches” of compound leaves. Leaflets will be easiest to remove if done right away after washing.

Here [http://edn.link/9eh4c4] is a brief video illustrating how to harvest a moringa leaf from a branch, remove leaflets, and place leaflets on a drying screen.

The rest of this article will focus on drying factors and methods. 

What factors should I be aware of in drying moringa leaves?

Air circulation

Air circulation facilitates drying and prevents moist conditions conducive to mold and rotting. Ensure adequate air circulation by spreading the leaves out thinly on your drying surface. Inner layers of thick piles of leaves will stay moist too long. Place leaves in mesh bags/cloth or on screened drying shelves/racks to allow air exposure on all sides. Fans increase air circulation and are often incorporated into cabinet dryers. Gentle air movement is best, to prevent leaves from blowing around in the dryer.

Temperature 

The higher the drying temperature, the faster your leaves will dry. Faster drying minimizes the likelihood of mold, but high temperatures reduce vitamin content (Alakali et al., 2015 ) and other health-promoting compounds like quercetin (Ademilui et al., 2018). ElGamal et al. (2023) stated that optimal drying temperatures for retaining vitamin C in vegetables range from 35 to 60°C. Minerals like calcium and iron were well retained at these temperatures in a study in Nigeria by Alakali et al. (2015).

Light

Working with cowpea leaves, researchers in Uganda found that drying in the sun reduced vitamins A and C by 58% and 84%, respectively (Ndawula et al., 2004). They attributed the losses to the effects of ultraviolet radiation.

Time

Dry leaves until they become crisp and brittle. Brittle leaflets should break apart easily. Soft leaflets that bend without easily breaking likely have too much moisture. Adjust air circulation and temperature to dry moringa leaves fast enough to prevent mold while retaining vitamins.

Humidity

High humidity increases the time to dry moringa leaves. The longer the leaves remain moist, the greater the risk of mold and rotting. Under high humidity, it is important to have good air circulation and sufficient heat. If you are drying moringa leaves during the rainy season without electricity you may want to:

• Dry the leaves on screens or in mesh bags. Doing so, and spreading the leaves thinly, exposes more leaf surfaces to the air. 
• Hang the leaves near the roof 2in a well-ventilated room (Figure 3).
• Mix/move the leaves around a few times during the drying process to make sure all the leaves are exposed to air.

Contaminants

Dry leaves in ways that minimize contamination of dust, animal droppings, and debris. This is most likely to be an issue with open-air drying in the sun or shade.

What are some methods of drying moringa leaves?

Options for drying moringa leaves include shade-drying, drying in direct sunlight, solar drying, and drying in an oven or cabinet equipped with a heat source and fan(s). An ideal drying method will optimize factors like air movement, temperature, and light to dry moringa leaves with minimal loss of vitamins. Your drying method also needs to be practical. A drying cabinet with a heat source and fan provides high-level control of temperature and air circulation; however, it requires electricity. Shade-drying probably retains more nutrients than sun-drying, but there is the risk of mold under high ambient humidity. Information for choosing and optimizing a drying method is summarized in table 2.

What if I cannot achieve ideal drying conditions?

Assess unacceptable versus tolerable losses in quality 

Rotting, moldy leaves pose an obvious health risk if consumed. This would be an example of unacceptable quality. Other examples would be leaves contaminated or burned (because of overheating) during the drying process. 

It would be reasonable, though, to accept the risk of some vitamin loss in using heat to dry the leaves before they become moldy. Even with some reductions in vitamins or antioxidants, moringa leaf powder will still have nutritional benefits. In promoting or marketing moringa leaf powder, avoid overstating its nutritional composition. Reports by those who have studied the effect of drying approaches on moringa powder (e.g., Ademiluyi et al., 2018 and Ahmed and Langthasa, 2022 ) are useful in gaining a sense of what nutritional values to expect for the method you use. Additionally, an ECHO Research Note by Witt (2020) presents nutritional values for a realistic serving size (5 g) of moringa powder.

Learn the nutritional tradeoffs of drying options

This is illustrated by a study in India by Joshi and Mehta (2010). The researchers compared established nutritional values of fresh moringa leaves with those of moringa leaves dried in the following ways:

• Shade drying, which they referred to as shadow drying. Leaves were placed indoors for 6 days on cotton sheets in a well-ventilated space, relying on natural air movement.
• Oven drying, with leaves on trays in a forced-air dehydrator at 60°C for 4 hours. 
• Sun drying of leaves placed on cotton sheets and protected from dust and insects by covering with cheesecloth. To avoid rehydration of leaves at night the leaves were brought indoors each night for 4 days.

In their experiment, leaves were dried until they became brittle. Hence, the differences in drying time between methods. Although temperatures were not given for the shade and oven drying treatments, their findings shown in figure 5 are still instructive. Vitamins A and C were best retained by shade drying. 

Minerals and protein varied little between methods. With respect to vitamins, the biggest losses compared to shade drying were those of vitamin A with sun drying (9% loss) and vitamin C with oven drying (60% loss). Even with a 60% loss of vitamin C with oven drying, a 5-g serving of the amount left would provide 19% of the 15-g recommended daily intake for a 1- to 3-year-old child.3

The nutrition of moringa leaves can also vary. Other researchers in India found that sun- and cabinet (shade)-dried moringa leaf powder contained 155 and 135 mg of vitamin C per 100 g of powder, respectively (Ahmed and Langthasa, 2022). In their study, cabinet-drying at 60°C reduced vitamin C by 25% compared to shade drying, quite a bit less than the 60% reduction found by Joshi and Mehta (2010). 

Note in figure 5 that drying increased vitamin A while reducing vitamin C. Drying typically concentrates nutrients because it removes moisture in plant material leaves. The fact that drying decreased vitamin C suggests it is more sensitive to heat than vitamin A. ElGamel et al. (2023) mention that vitamin C is more susceptible to heat loss than other vitamins, so if your drying procedure retains vitamin C, other vitamins are probably retained as well. Knowing that vitamin C may be reduced by drying, you could also plan for other sources of vitamins in addition to moringa powder (e.g., fresh moringa leaves and leaves from other leafy greens such as chaya (Cnidoscolus aconitifolius). 

Look for ways to work within limitations

Table 1 mentions examples such as coverings to protect the leaves from ultraviolet light for sun and solar drying. Nichols (2008) shared with ECHO a method they used in Burkina Faso, in which leaves are placed on woven plastic mats under pieces of corrugated metal roofing supported by boards (a link to their article is in the References section).

One approach for which there is little information available is the use of desiccant for drying moringa leaves. This concept was explored by Dodson (2012) as part of an undergraduate thesis project. Her work demonstrated the potential of desiccants (e.g., montmorillonite clay, silica gel, and zeolite) to reduce 90% of the moisture in moringa leaves in an enclosed space, without fans or a heat source. More experimentation could be done to find out how much desiccant is required to dry a given quantity of leaves. A desiccant approach could be practical for household use. Please let us know if you would like to experiment further with this or related adaptations and approaches (email publishing@echonet.org). 

A word about shelf life 

A general guideline for the storage life of moringa is 6 months, since nutrients in moringa powder decline over time (Adejumo and Dan, 2018). Maximize the storage life of your moringa powder by keeping it cool (room temperature or cooler), dry (in airtight containers that exclude humidity, and dark (light causes the powder to fade). Do not consume moringa powder that is molding or smells rotten. 

Final thoughts

A good overall indicator of the quality of moringa powder is its color. It should be bright green. Greenness indicates that the harvested moringa trees were healthy, without nutrient deficiencies that lead to yellowing and discoloration. Reduced greenness is also linked to the degradation of chlorophyll caused by high-temperature drying (Ali et al., 2014). Discoloration can also be caused by decomposition/rotting that happens when the leaves stay moist too long.

Aim for a drying method that farmers and gardeners can readily implement with available materials. Look for low-temperature approaches to dry the leaves. Though drying may reduce some nutritional attributes of moringa leaves, moringa leaf powder still offers significant nutritional benefits. Consuming a mix of fresh moringa leaves and moringa leaf powder helps ensure that you get the maximum nutritional value from moringa. Finally, make moringa powder in quantities that can be consumed before it expires.

References