Moringa oleifera is often recognized as the “tree of life” because of its crucial importance (Sekhar et al., 2018). M. oleifera is a significant food crop that is gaining popularity as a source of “tropical natural nutrition.” M. oleifera is usually thought to be a cure-all for all ailments and disorders (Panacea). (Stadtlander and Becker, 2017). M. oleifera has long been used in herbal therapy by Indians and Africans, as it has a strong potential for treating deficiency illnesses. (Lakshmipriya et al., 2016).
       
Drumsticks are essential for human health due to their medicinal and therapeutic properties. At present, the demand for moringa has increased annually due to off-season availability, increased utilization by people and improper postharvest practices. To prevent postharvest losses in the moringa, there is a need for processing and it will meet the demand of the market throughout the year (Nithyapriya et al., 2013).
       
Dehydration is a method of preservation; hot air is used to dry food and plant materials. The weight and volume of the product are minimized during drying, resulting in lower packaging, storage and transportation costs (Kinki et al., 2020). The conventional drying process takes more time and energy than advanced techniques and it also results in microbial contamination of food products due to prolonged processing time and improper handling, which will also affect the organoleptic properties and product quality in terms of mould growth during storage. Alternatives to conventional drying advanced dryers, viz., freeze- or vacuum-drying and heat pump-assisted dehumidified air drying (HPD), are used for dry heat-sensitive materials. Klungboonkrong et al.(2018) designed an HPD dryer, which resulted in the retention of bioactive compounds in dried products. The HPD dryer saves time and energy (15-20%) along with low temperatures. HPD dried products have higher retention of sensory and nutritional properties (Yohana et al., 2018). Using the HPD drying process, the study was designed with the aim of enhancing drying properties and phytochemicals retention in drumsticks.
 

Processing for the preparation of dried drumstick powder
 
Fresh and mature PKM-2 drumsticks were procured from Horticultural college and Research Institute, Periyakulam and then drumstick pieces were steam blanched for 2-5 min until tender and sulphated at 0.1% for 10 min to preserve the Colour  and to improve storage durability. After that, a dehydration process was performed with heat-pump dehumidified-air drying by Klungboonkrong et al. (2018). The HPD drying unit heat pump system consists of a compressor, evaporator, condenser and expansion valve. The dimensions of the drying chamber were 0.90 x 1.80 x 1.70 m. When air flowed over an electric heating coil with a maximum capacity of 1800 W, the compressor moved back and forth in a straight line with a capacity of 300 W. The air was passed into the drying chamber to dry the materials were placed in inner trays (each tray 50 kg) and drying temperature was regulated by a thermostat. The drumstick pieces were dried at 45(A), 55(B) and 65(C) °C with a 0.5 m/s air speed.
       
GC-MS analysis of fresh and dried drumsticks was performed by Kumaravel et al. (2010) and Vijayakumari et al. (2015). The dehydration characteristics of drumstick powder were analysed, viz., powder recovery, water solubility index (Grabowski et al., 2006), flowability (Seerangurayar et al, 2017), bulk and tap density (Chegini and Ghobadian 2005), Hausner ratio, Carr index (Seerangurayar et al., 2017), hygroscopicity (Cai and Corke 2000), water and oil absorption capacity (Rosario and Flores 1981), rehydration ratio and dehydration ratio (Ranganna, 1986).
 
Statistical analysis
 
Data analysis was performed in a completely randomized design (CRD) using SPSS 14.0 for Windows (Peugh and Enders, 2005). According to the varied drying temperatures, Principal Component Analysis (PCA) was performed on the significant variables.
 
 

Identification of bioactive components in drumsticks by GC-MS
 
Fresh and HPD-dried drumstick powder extracts contained 50 major bioactive compounds, with the maximum quantum found in 15 compounds (Table 1), including 2,6-dihydroxybenzoic acid 3TMS derivative (29.90%), butanal 2-ethyl-3-methyl (23.56%), 3,4-dihydroxymandelic acid 4TMS derivative (8.45%), hexasiloxane and 1,1,3,3,5,5,5, 7,7,7,7 (8.02%). These bioactive chemicals have therapeutic significance as hair growth promoters, hydroxylation of liver enzymes during phase I metabolism and inhibiting the formation of uric acid and arachidonic acid inhibitors in the human system, among other things (Bernhard et al., 2014).


       
Antibacterial and antioxidant capabilities, as well as hypocholesterolemic and alpha-reductase inhibitor properties, are found in hexadecanoic acid-methyl ester (6.03%) (Mazumder et al., 2020). Ethanone 1-(3-ethyloxiranyl) - (5.10%) possesses powerful antibacterial and antioxidant capabilities that aid in the destruction of food-borne pathogens and disease prevention (Jusuf et al., 2020). The chemical cyclohexasiloxane dodecamethyl (4.86%) is used in skincare, cosmetics, breast implantation and as an antibacterial agent (Pinto et al., 2017). The bioactive component squalene (4.58%) has antimicrobial, hypoglycemic, hypolipidemic, cancer-preventive and immunostimulant activities (Chandrasekaran et al., 2011). In humans, tetratetracontane (4.02%) demonstrated antioxidant and anti-inflammatory characteristics as well as therapeutic efficacy (Melappa et al., 2014). Because it contains antibacterial and antifungal properties, bis (2-ethylhexyl) phthalate (3.63%) aids in the prevention of foodborne illness (Abubakar et al., 2018). Cancer-preventive, anti-inflammatory, antihistaminic and antieczemic activities are found in heneicosane (3.54%) and (E)-9-octadecenoic acid ethyl ester (2.95%). (Sivakumar et al., 2011; Bukhari et al., 2017). 1-Dodecanol (2.56%) and eicosane (2.18%) are anticancer chemicals in the human gastric SGC-7901 cell line (Munoz et al. (2021); Adnan et al., 2019) and butanoic acid, 3-hydroxy-3-methyl-, methyl (2.04%) is a flavouring ingredient in moringa fruit Munoz et al. (2021).  
       
The results demonstrated that the above-mentioned bioactive compounds were not significantly affected by drying temperature due to HPD drying techniques that used a low temperature for a short time.
 
Optimization of HPD drying for the production of drumstick powder by PCA
 
The principal component analysis (PCA) results are shown in Fig 1. Optimization drying temperatures (45°C (A), 55°C (B) and 65°C (C) were used to explain the relationship between the different dehydration factors and to determine the most relevant causes of variability (Table 2). PCA condenses eight variables into two principal components (PC), which explains 83.96 percent of the total variance. PC1 accounted for 64.36% of the variance in the model and PC2 accounts for 19.60% of the total variance. The Kaiser-Meyer-Olkin (KMO) measure of sampling adequacy for the PCA is 0.530. To further investigate the contributors to the principal components, the factor loadings in PC1 and PC2 were compared (Table 3 and 4). The eigen values for the F1, F2 and F3 (Factor) were 4.337, 2.034 and 0.797.  In factor loading F1, water solubility (0.983), rehydration ration (0.903) and water absorption capacity (0.865) were positively correlated and bulk density (-0.870), carr index (-0.688) and hygroscopicity (-0.729)  were negatively correlated. Similarly in F2 and F3, oil absorption capacity (0.919) and tap density (0.695) had positive correlation whereas other variances had negative correlation.  These results suggested that the reasonable score range of the principal components could be used for excellent sample selection according to the correlations between the original three variables and these two principal components.








       
The moringa pod HPD dried at 55°C (B) had 97.22% powder recovery, where increasing the temperature (65°C) led to a lower process yield. The water solubility index of the drumstick powder increased (67.18 to 71.18%) with increasing drying temperature. The bulk density and tap density of the HPD-dried moringa powder varied from 0.437-0.465 and 0.518-0.539 g cm^-3 respectively. During the drying process, a higher drying temperature (55°C (B) and 65°C (C) will reduce the density of the powder to rapidly remove moisture.
       
The effects of functional characteristics such as water absorption capacity (WAC) and oil absorption capacity (OAC) in dried drumstick powder were analysed. The WAC was 1.988 g at 45°C (A), 2.053 g at 55°C (B) and 2.196 g at 65°C(C). The oil absorption capacity ranged between 5.49 g and 5.712 g at different temperatures. The water absorption was higher at 65°C and the oil absorption was higher at 55°C, which may be due to the protein concentration. The values of WAC (23.2%) and OAC (18.5%) compared favourably with the results of spinach (Amaranthushybridus) by Adeyeye and Omolayo (2011). Water absorption capacity is an important dehydration characteristic that correlates the function of hydrophilic molecules such as proteins, carbohydrates and dietary fibre. However, the oil absorption capacity of flours facilitates the improvement of flavour and mouth feel during food preparation Abe-Inge et al. (2018).  
       
Hauser’s ratio of HPD dried powder was found in the range of 1.193-1.409 and the carr index was in the range of 19.41-19.51%. Hauser’s ratio and carr index measure the flow properties of dried powders. From the above, it is clearly found that the drumstick powder dried between 55°C (B) and 65°C (C) has excellent flowability characteristics and good flowability at 45°C. The hygroscopicity of HPD-dried moringa powder was 1.389 (45°C), 1.41 (55°C) and 1.502 (65°C). The lowest hygroscopicity values were recorded at low temperatures.
       
The dehydration ratio of drumstick powder dried by an HPD dryer ranged between 20.28 and 22.66 ml/g at different drying temperatures. The dehydration ratio was observed to be higher at 55°C (B) because of the incomplete removal of moisture and lower at 65°C due to the complete removal of moisture (heat air treatment). Similarly, the rehydration ratio ranged between 3.48 and 3.78 ml/g. The rehydration ratio was observed to be lower at 45°C (A) due to incomplete reabsorption.
       
The similar trends were reported by Potisate et al., 2015 in HPD dried moringa and express the excellent flowability, hygroscopicity (1.25-2.30) and rehydration ratio (3.821- 4.220). Tummanichanont et al., (2017) also opined that the HPD dried Andrographis paniculata spinach shows the results of hygroscopicity (1.42-1.95), dehydration ratio (18.5 -24.01) and rehydration ratio (3.12-3.69). So, the loss of water and heat leads to tension in the product’s cell structure, leading to hygroscopicity of the powder and dehydration will decrease the dimensions of HPD dried moringa powder.
 
 

The effects of drying temperature were studied for both fresh and dried drumstick powder. The optimized drying temperature of 55°C shows better dehydration properties such high powder recovery (97.22%), excellent flowability and functional characteristics. The drumstick extract contains 50 major bioactive compounds and found that 15 numbers of compounds retained in both fresh and dried drumstick powder. These bioactive compounds have various nutraceutical and therapeutic properties. From this research finding, HPD drying was considered as one of the best drying technique to conserve nutritional quality attributes with higher efficiency and economically feasible for all the food processing sector. HPD dried drumstick powder can be used to develop novel functional food products such as vegetable soup, energy bars, energy drinks, extruded products and incorporated food products may be utilized in nutritional intervention programmes.
 

None.