13.4.2 Flour and Starch
The commonly-used method for making flour and starch involves dry processing. It involves milling of dried EFY chips into crude flour, which is subsequently purified via wind-sifting. EFY flour produced using such methods is of low purity and sold as a food commodity at a low price (Parry, 2010; Ye et al., 2014).
Flour The preparation of crude EFY flour from fresh corm requires the following procedure. The corm is weighed, washed, with its epidermis removed and sliced into pieces, 2–3 mm in thickness. The corm slices are then immersed in 1 % (w/v) sodium bisulphite, for 1 min, followed by oven-drying at 120 °C for 40 min. The drying process is continued at 60 °C until a constant weight is obtained. The dried corm slices are subsequently ground and the resultant flour is sieved (425 pm aperture) to produce flour (Li and Xie, 2002, 2004; Liu et al., 2005; Xu et al., 2014). The flow-chart for producing konjac flour is given in Figure 13.2 (Chua et al., 2012). Crude flour is used to make low-grade noodles. Glucomanan, the hydrocolloidal dietary fibre which is an important biomaterial as food supplement is extracted from the flour, especially from the A. konjac species.
Figure 13.2 Preparation of crude EFY flour (CEF) from fresh corm material (adapted from Chua et al. (2012).
Starch The procedure for starch extraction from EFY is described by Amani et al. (2004). The tuber was peeled, cut into small pieces and immediately suspended in 0.1 % (w/v) sodium metabisulphite solution. Then the samples were homogenized in a Warring Blender and the homogenate was suspended in a bulk amount of water containing 4 % NaCl. The supernatant water was discarded and the wet starch oven-dried for 48 h at 45 °C. The average yield of EFY (A. Paeoniifolius) starch has been found to be 9-10 % of the matrix on fresh weight basis (Lenka and Nedunchezhiyan, 2014).
Babu and Parimalavalli (2012) have studied the functional and chemical properties of EFY starch. Three different methods were used to isolate starch from Amor-phophallus paeoniifolius (EFY). Functional properties such as water absorption capacity, oil absorption capacity, swelling capacity and chemical properties such as moisture content and dry matter, were analyzed. A significant difference in swelling capacity (0.62-1.25 g/g) and water absorption capacity (0.22-0.64 ml/g) was seen among the EFY starches. EFY starches exhibited no significant difference in moisture content (9.99–12.13 %) and dry matter (88.46–89.99 %).
13.4.3 Indigenous Medicines
The EFY has many medicinal properties. In India, it is used in Ayurvedic drugs in the treatment of inflammatory conditions, hemorrhoids, rheumatism and gastrointestinal disorders (Raghu et al., 1999; Ray, 2015). This herb is also used for earache, pain, intercostal neuralgia, puerperal fever and swelling of the throat (Joshi, 2000). The paste of tubers is applied externally to reduce pain arthritis. In China, the A. konjac has been used in Traditional Chinese Medicines as an immune-regulation and health food for a long time (Huang et al., 1998; Vuksan et al., 2001).
Studies have shown that the chloroform-acetone-ethanol extracts of the wild EFY tubers exhibited significant antibacterial and anti-inflammatory properties (Shilpi et al., 2005). Ethanol extracts of the tubers of A. campanulatus have also been reported to possess antibacterial, antifungal and cytotoxic activities (Khan et al., 2007).
Several indigenous technologies have also reported on the biomedical applications of EFY. In Tripura (India), the tribal people consume the banana flesh coated EFY balls for controlling stomach disorders and piles (Sankaran et al., 2008b). The high acrid wild EFY corms are used for the treatment of mouth ulceration and tympanitis in cattle in India. The farmers provide 100 g of ground EFY as a drench in the affected cattle. The EFY creates a stinging effect on the lips and the tongue of the cattle, causing an increase in salivary secretions, thereby helping the animals to get temporary relief from typany (Deo Shankar et al., 2008).
13.5 EFY Processing with Technological Interventions
The value addition of EFY has taken a flip recently because of the re-discovery of the crop’s many functional properties applicable to food and pharma sectors.
13.5.1 Resistant Starch
In order to meet the growing demands of the consumers for functional foods, carbohydrates of natural origin, such as resistant starch (RS) can act as functional ingredients and have a beneficial effect to human health, and are favoured over carbohydrates of high glycemic index (Reddy et al., 2014). RS is the one of non-digestible naturally occurring carbohydrates in the small intestine of humans and when reaching the large intestine, it undergoes biochemical reactions, by the commensal intestinal microflora to produce short chain fatty acids (Annison and Topping, 1994). These short chain fatty acids can be partially absorbed in the small intestine and become a source of energy to the microflora. whereas undigested biomass is excreted in the stool. Though several researchers have investigated the flour and starch obtained from EFY tubers in order to find new applications in food, a limited number of studies on resistant starch RS are available (Reddy et al., 2014).
Enzymatic hydrolysis and preparation of resistant starch (RS) Reddy et al. (2014) studied the enzymatic hydrolysis of EFY (A. paeoniifolius) starch. The EFY starch (10 % w/w db) was suspended in sodium acetate buffer (0.1 M and pH 5.3) and mixed with pullulanase enzyme (40 U/g dry starch), and the mixture was incubated in a shaking water bath at 60 °C for 10 h. The sample was heated in a boiling water bath for 10 min to inactivate the enzyme. Starch gelatinization, prior to adding the enzyme, was performed by boiling the sample in a water bath for 10 min. The starch samples were autoclaved at 121 °C for 30 min, cooled and kept at 37 °C for 24 h. The samples were then lyophilized to obtain RS (Figure 13.3). After preparation of resistant starch, the morphological, physical, chemical and functional properties were assessed. The enzymatic and retrogradation process increased the yield of resistant starch from starch with a concomitant increase in its water absorption capacity and water solubility index. A decrease in swelling power was observed, due to the hydrolysis and thermal processes. The reduced pasting properties and hardness of RS were associated with the disintegration of starch granules due to the thermal process. The viscosity was found to be inversely proportional to the RS content in the sample. The thermal properties of RS increased due to retrogradation and recrystallization.