Comparative assessment of dried Moringa leaves of Nigerian ecotype

Abstract

Moringa oleifera is an under-utilized vegetable plant known for its nutritional and medicinal properties. Current post-COVID-19 pandemic realities necessitate increased utilization of Moringa, with minimal postharvest losses. Thus, this study was conducted to compare the effect of different drying conditions on microbiological safety and assess shelf stability of dried Moringa leaves of Nigerian ecotype. Freshly harvested leaves were divided into four (4) parts and dried differently; sun-drying at day temperature of about 42 °C for 7 hours, oven-drying at 45 °C for 6 hours, shade-drying for 2 days while the last part was combined sun-shade drying. A second batch of fresh leaves was sun-dried and double-packaged in polythene pouches into rigid plastic plates that were subsequently stored in the dark at room temperature. Microbial enumerations of all freshly dried samples and the stored samples were conducted at monthly interval for five (5) months. Proximate composition, chlorophyll, iron and ascorbic acid contents were determined using standard methods. The results showed no growth on all freshly dried samples, irrespective of drying methods. Similarly, the result of shelf stability indicated acceptable levels of microbial growth throughout storage period. Proximate composition result indicated that storage length significantly (p < 0.05) affected the proximate composition of the samples. Moisture content increased with increasing storage time from 4.18±0.28 to 6.33±0.29 g/100 g; while protein, ash (total minerals), crude fibre, fat and carbohydrates contents all decreased to varying degrees with increasing storage time, from 36.10±0.51 to 35.40±0.50 g/100 g, 4.45±0.17 to 4.10±0.00 g/100 g, 6.55±0.40 to 6.13±0.05 g/100 g, 3.85±0.11 to 3.67±0.00 g/100 g and 44.87±0.44 to 44.37±0.44 g/100 g, respectively. This decrease is within acceptable standard that compares favourably with the levels that are found in other leafy vegetables. The chlorophyll content decreases with increasing storage length from 110.24±6.21 to 56.37±2.24 mg/100 g, with similar trend in iron and vitamin C contents. Hence, these results indicate that Moringa leaves can actually be dried using easily available methods of sun-drying, oven-drying and shade-drying for storage; while still maintaining acceptable standards of food safety and nutrient status. Therefore, dried Moringa leaves and powder can be exploited for commercial purposes in areas of abundant production for continuous distribution in Nigeria.