It would be nice, especially if it’s raining outside, to be able to dry moringa leaves by simply placing them on a flat surface in your house. Will the leaves become moldy? Conditions that favor mold are high humidity and heat, combined with poor air circulation. I decided to try drying a handful of moringa leaves in my office since it is an air-conditioned space with relatively stable humidity that rarely goes over the 65% threshold conducive to mold.
The moringa leaves were placed on a paper towel on a table, with a datalogger next to the leaves. Below you can see what the leaves looked like at the beginning (just after harvest) and end of the drying period.
Ideally, your moringa leaves should dry to the point that they are crisp and brittle. It took two days for the leaves to become slightly crisp. During that time humidity ranged from 59% to 69%, with an average of 65%. Temperature ranged from 22.6 to 24.5°C with an average of 23.5°C.
Out of curiosity, I tested the moisture content of powder made from the leaves. The average of two readings, taken using the oven-dry method, was 10.5%. How dry does moringa powder need to be to prevent microbial growth/spoilage during storage? For dehydrated foods in general, a moisture content below 10% is desired (Vera Zambrano et al., 2019). This moringa powder, then, was slightly above the 10% threshold. Based on research with herbal teas, moringa researchers Wickramasinghe et al. (2020) recommended a moisture content of 7% for long-term storage. So, while I did not see any mold on the leaves dried in my office, the powder from them could potentially mold in storage.
What happens if you dry at a higher temperature? In Sri Lanka, moringa powder from leaves dried at 55°C had a moisture content of 6.64% (Wickramasinghe et al., 2020). I tested the moisture content of moringa powder with leaves dried here at ECHO in Florida. The leaves were crisp and brittle after a day in a heated, forced-air cabinet dryer, with temperatures reaching 45°C and humidity stabilizing at 15%. Below is a photo of the leaves in the cabinet dryer.
As with the leaves dried in the office, immediately after drying I converted the leaves to powder—using a coffee grinder—and tested the moisture content. The moisture content of the powder from leaves dried at 45°C in the cabinet drier was 6.18% (average of two readings).
A few take-a-ways
What I observed in this non-replicated test was in agreement with other research (Ahmed and Langthasa, 2022; Alakali et al., 2014) showing that drying at temperatures (e.g. shade drying) may result in moringa powder that is higher in moisture than what we would like to see (< 10%). That doesn’t necessarily mean that low-temperature moringa drying isn’t an option. It does mean we should be aware of the health risks related to microbial growth and spoilage.
Here is a link to a web page with some helpful tips about assessing the quality of your moringa powder and prolong storage: Unlocking the Secrets: Moringa Powder Shelf Life Revealed. Some of those are:
- Store it in cool and dry. They suggest the possibility of desiccants to absorb moisture and thereby extend the shelf life of moringa powder. It would be interesting to test the extent to which a desiccant like baked rice can reduce the moisture content of moringa powder.
- Look for signs of deterioration. Some of these are:
- Clumping of the powder—an indication of high moisture
- Change in color from bright green to brown—can be caused by exposure to light and can also be an effect of spoilage
- Unpleasant odors indicative of spoilage
Lastly, producing moringa powder with a moisture content below 10% seems quite doable, given that drying at 45°C (113°F) resulted in less than 7% moisture. Whether you use a solar drying approach, a household oven, or a homemade drying cabinet, avoid vitamin loss caused by overly high drying temperatures. Alakali et al. (2015) concluded that, for maximum retention of nutrients, the temperature for oven drying should not go over 50°C.
Let us know of your experience drying moringa and any lessons learned.
References
Ahmed, S. and S. Langthasa. 2022. Effect of dehydration methods on quality parameters of drumstick (Moringa oleifera Lam.) leaf powder. Journal of Horticultural Sciences 17(1):137-152
Alakali, J.S., C.T. Kucha, and I.A. Rabiu. 2015. Effect of drying temperature on the nutritional quality of Moringa oleifera leaves. African Journal of Food Science 9(7):395-399.
Vera Zambrano, M., B. Dutta, D.G. Mercer, H.L. MacLean, and M.F. Touchie. 2019. Assessment of moisture content measurement methods of dried food products in small-scale operations in developing countries: A review. Trends in Food Science & Technology 88:484-496
Wickramasinghe, Y.W.H. I. Wickramasinghe, and I. Wijesekara. 2020. Effect of steam blanching, dehydration temperature & time, on the sensory and nutritional properties of herbal tea developed from Moringa oleifera leaves. International Journal of Food Science 2020:5376280. doi: 10.1155/2020/5376280