Moringa oleifera leaves have nutritional and medicinal values that helps to prevent disease. The objective of present research was to investigate the nutritional value and microbiological evaluation of Moringa oleifera leaves powder during storage periods. In these research leaves were collected from Dhaka, savar, dhamrai, nabinagar, kaliakoir respectively. Moringa oleifera leaves were processed by using 3 different methods like as solar dried, mechanical drier and oven drier. Nutritional values (proximate analysis) including moisture, protein, ash, fat, carbohydrates and energy were measured by utilizing distinct methods and devices. This study found highest moisture content in solar drier at 4th month of storage Moringa oleifera powder. Moisture content of raw Moringa oleifera is 81.4% where gradually increased the moisture content during the storage periods. Three different methods including solar drier, mechanical drier and oven drier were used for measuring nutritional values. The result showed that in solar drier, moisture content was measured increasing during 4 month storage 3.93%, 4.06%, 4.11% and 4.52% where mechanical drier were 7.75%, 7.80%, 7.86%, 7.96% and oven drier 6.15%, 6.28%, 6.75% and 6.82%. Other proximate analysis also measured both three methods. Beside proximate analysis microbiological analysis also conducted in the storage periods. Highest number of coliform bacteria and fungus were identified in the last month of storage periods. Among three methods oven drier gives best results during preservation periods. Moringa oleifera leave could be used as antimicrobial medicine against commercial antibiotics and also cure different diseases such as diarrhea, high blood pressure, food poisoning etc.

Moringa oleifera is a perennial tree that belongs to the Moringaceae family and is yet underused. Drumstick, sahjan, and sohanjana are all names for the same plant. All plant components have a wide spectrum of functional and nutraceutical qualities, making this plant a versatile biomaterial for food and other applications [1]. The leaves, blooms, and fruits of this plant are utilized as a major food source to battle protein energy deficiency, which affects the majority of the world's developing and underdeveloped countries. Because of the presence of several types of antioxidant chemicals, this plant's leaves are very good origin of nutraceuticals and functions [2]. Flavonoids from plants are significant in the diet, and a high flavonoid consumption has been associated to a lower risk of cardiovascular disease, osteoporosis, and are other age related degenerative complication [3-5]. The World Health Organization (WHO) has been studying M. oleifera's usage as a low-cost supplement enhancer in the world's poorest areas for decades (WHO Readers Forum, 1999). According to the United Nations Food and Agriculture Organization, one out of every twelve people in the world is malnourished, with 160 million children under the age of five falling into this category (United Nations Food and Agriculture Statistics, 2008). Herbal remedies are still widely utilized in many parts of the globe, particularly in places where modern treatments are unavailable [6]. Furthermore, scientific study to establish the biological activity of medicinal plants is needed in utmost African nations where verdant treatments are yet widely depended on due to the expense of chemotherapy treatments. The findings of this research might lead to the validation of historically used and medicinally important plants, allowing them to be fully utilized [7]. Moringa is a fast-growing plant that is commonly accessible in the tropics and subtropics and has a wide range of industrial and therapeutic applications. One of the most extensively farmed species is Moringa oleifera, an essential medical plant. Anti-tumour, antioxidant, anti-inflammatory/diuretic, antipathetic, hypertensive, hypocholesterolaemia, and hypoglycaemic properties have long been considered to exist in Moringa species [8].The roots, flowers, gum, and seeds are commonly used as anti-diabetics and to treat inflammation, heart disease, liver disease, and haematological, hepatic, and renal function. Moringa leaves, fruits, and seeds have been shown to be high in protein, important minerals (calcium, magnesium, potassium, and iron), and vitamins (vitamin A, C and E) [9]. Plants have recently acquired popularity as a source of new chemicals for treating microbial diseases. Because of the high cost, low effectiveness, and developing resistance to conventional treatment, the need for plant-based antimicrobial is becoming more urgent. Herbal medications are significant in primary health care in developing countries, particularly where access to health care is restricted. The moringa plant's natural medicine components have been shown to decrease tumor incidence in experimental mice [10]. This research helps to evaluate the nutritional value of Moringa oleifera during storage periods and microbiological analysis also were determined. In light of these considerations, the goal of this study was to evaluate the characteristics of Moringa oleifera leaf powder in order to expand its use as a functional food ingredient in food and pharmaceutical products of interest, as well as to promote this important but underutilized plant that is readily available in certain parts of the country in a shelf-stable, easily usable form to the general public.

This research work was completed at vegetable technology and Food microbiology, Institute of Food Science and Technology, Bangladesh Council of Scientific and Industrial Research, Dhaka- 1205.

Sample collection area and processing

Fresh Moringa oleifera (sajna leaves) leaves were collected from the BCSIR campus, Savar, Dhamri and Fulbaria. The sajna leaves were then weighed and properly washed in clean water to remove any clinging soil or dead leaves, as well as to minimize the amount of infected microorganisms. Then, for up to 10 minutes, boil with 800°F water to destroy the enzymes in the food and to prevent unwanted texture changes. Then cooed and 0.1% sodium metabisulphite and were Kept into room temperature for 1 hours. Keep in polybag for further use (Figure 1).

Figure 1:  Raw Moringa oleifera leaves.

Nutritional composition of powdered product (Based on Different drying methods)

All data were analyzed four times for four month to know the time of retention of nutrient of the powder form of Moringa oleifera leaves. The data for nutritional composition of solar drying, mechanical drying and oven drying product were mentioned in table 2, 3 and 4. The observation of powdered product in different month influenced some of the characteristics of nutritional composition. It was the effect of dehydration which can vary in month to month observation (Table 2).

Above table (2) shown that the gradual increase of moisture ,with the decrease of protein, fat, fiber, ash, carbohydrate, energy content of leaves powder. When it was freshly prepared the moisture content was (81.65%). After month to month observation, the moisture contents were decreased and nutrient contents were increased from the observation of raw material. For the solar dried Moringa oleifera leaves powder, the moisture contents were increased and the other nutrient contents were slightly decreased from the month to month observation (Table 3,4).

From the four month observation, we can see that some of the nutritional composition were increased in month to month duration and some of the composition were decreased in month to month duration and some of them were fluctuated in month to month duration. This result can variate by the effect of dehydration on the nutritional composition.

Result of the total bacterial count

In these research plate count agar (PCA) media were used to calculate the bacterial count from dried moringa leaves powder. This study represent different bacterial load in preserved moringa leaves powder. Bacterial count of this study was done by two categorized like as direct counting from dried sample and count from 10-3 dilution. In the first month, absence of growth in 10-3 dilution of all sample and presence of growth in others plates where the sample was directly taken from the dried leaves. In solar dried gradually increased the bacterial counts and after 4 month TNTC found in 10-3 dilution. In mechanical drier bacterial count found TNTC after 4th month where oven dried moringa leaves powder found no growth up to 3rd month of preservation. The total viable bacterial count of samples are shown in below (Table 5).

Result of the total fungal count

PDA agar media was used for the fungal count of this study by the spread plate methods. In the first and second month absence of growth of fungus in most of the sample and presence of growth of all sample in third and fourth month. Among 3 method oven dried method gives good result.The results are presented in the below Table 6 and Figure 2 (Table 6).

Figure 2: PCA plate with bacterial growth.

Figure 3: PDA plate with fungal growth.

Figure 4:  LST media with coliform growth.

Result of the enumeration of total coliform

LST (Laurly Tryptose Sulfate Broth) media by MPN (Most probable Number) three tube method was used for total coliform count and EMB (Eiosin methylene blue) was used to see the fecal contamination. The total coliform count of the samples are shown in Table 7,  Figure 3 and 4 .This total coliform counting sample was directly taken from the dried leaves. In the first month observation, absence of coliform and in the second, third and fourth month observation, presence of coliform in all sampling plate (Table 7) (Figure 2-5).

Figure 5: Growth of coliform bacteria on EMB plate.

Moringa olifera dried powder is very much important now a days in heath sectors. There are so many medicinal value and nutritional value present in dried powder which is helpful for public health. Moringa leaves powder uses as natural products treatment against more than 300 diseases in recent time over the world. In this present study processed powder products were stored in room temperature (25-30?C). The nutritional and microbiological quality of the dried leaves powder were assessed after 6 months of storage. The quality of the processed product was found to be different from that of newly processed products even after one month of storage. The quality of the first month's product was superior to the previous items. It began to degrade after four months of storage and rapidly worsened after five months. The major cause of product degradation was excessive moisture and ascorbic acid levels. As a result, chemical preservatives that are not hazardous to human health should be applied at the required amount allowed by Bangladesh Standard and Testing Institute to extend the shelf-life of processed items. Leaves (84–86%), stems (14–15.5%), and miscellaneous materials were consistently present in Moringa samples (0.25% to 0.40 %).  

Table 5: Bacterial count observation of moringa leaves powder on PCA plate.