Influence of convective hot air drying on physico-functional, thermo-pasting and antioxidant properties of elephant foot yam powder (Amorphophallus paeoniifolius)

The present study focused on the effect of different drying temperatures (40, 50, 60 and 70 °C) and combination of pre-treatments: potassium metabisulphite (KMS), potassium metabisulphite + Citric acid + blanching (KCB)] on functional, thermo-pasting and antioxidant properties of elephant foot yam (EFY) powder. Drying temperature and pretreatment reduces the water and oil absorption capacity, and the highest values were 2.34 g/g and 1.19 g/g for drying at 40 °C for the untreated sample, respectively. KMS pretreatment enhanced the bulk density, foaming capacity, emulsion capacity, and emulsion stability with an increase in drying temperature. Pasting temperature and viscosity decreased with an increase in drying temperature, and the maximum was observed at 40 °C for KMS pretreatment. Blanching increases the gelatinization temperature resulting in higher mid-and end-temperatures for KCB pretreatment. The antioxidant properties decreased with an increase in the drying temperature and were found to be minimal in the case of KCB treated samples.

Optimization of parameters to improve transformation efficiency of elephant foot yam (Amorphophallus paeoniifolius (Dennst.) Nicolson

Elephant foot yam (Amorphophallus paeoniifolius (Dennst.) Nicolson), is an important edible tropical tuber crop, belonging to the family Araceae. Corms produced by this plant is very big and they are rich in starch, protein, mineral, vitamins, and dietary fiber but has acridity problem. This crop is susceptible to virus and phytoplasma diseases which affects crop growth and corm yield. Even though this crop has high commercial value, the problems like susceptibility to viral diseases, acridity problems, and lack of genetic diversity made hindrance in their exploitation. These issues can be resolved only by improving the characters through genetic transformation. To achieve genetic transformation in this important crop, a study was conducted to optimize various parameters for efficient Agrobacterium-mediated genetic transformation using embryogenic calli with vectors having gus reporter gene. Calli were developed using petiole and leaves of in vitro plantlets of elephant foot yam cultivar Gajendra and experiments were conducted to evaluate the sensitivity of calli to different doses of antibiotics viz. geneticin, hygromycin, ticarcillin. It was observed that complete death and discoloration of the calli were obtained with 25 mgl^-1 geneticin and 10 mgl^-1 hygromycin. The lowest lethal concentration of ticarcillin against Agrobacterium growth was found to be 500 mgl^-1 which did not affect calli growth. Optimized parameters for efficient transformation in elephant foot yam include 100 μM acetosyringone concentration with 2 days of co-cultivation at temperature 22 °C using LBA4404 strain. The putative transformants were characterized for the integration of the gus gene using PCR and nucleic acid spot hybridization. The optimized protocol is simple and reproducible and may be adapted for other cultivars also.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02824-6.

Nutritional composition and antidiabetic effect of germinated endosperm (Borassus flabellifer), tuber (Amorphophallus paeoniifolius) and their combined impact on rats

Diabetic patients usually avoid germinated endosperm of sugar palm (GESP) and elephant foot yam tuber (EFYT), fearing that these may further deteriorate existing hyperglycemia. In the present study, this suspicion was investigated by analyzing the nutrients and following the animal experiments by supplementary feeding powder of GESP, EFYT, and their mixture in addition to the regular diet for the six consecutive weeks. Next three weeks, the powder was withdrawn, and fasting blood glucose (FBG) levels were recorded from the beginning. The results clearly showed that these foodstuffs significantly (P < 0.001) reduced FBG levels of alloxan-induced diabetic rats. The mixture of GESP & EFYT showed the maximum antidiabetic effects followed by GESP and EFYT, respectively. GESP, as well as the mixture, returned the FBG levels of diabetic rats within the normal range by the end of the 6th week, even after withdrawing the powder, but not by the EFYT. These results suggested that the foodstuffs may restore the damaged pancreatic β-cell functions by the end of the 6th week. Nutrient contents like fiber, zinc, as well as antidiabetogenic phytochemicals present in these foodstuffs, could perform these functions.

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The germinated endosperm of sugar palm (Borassus flabellifer) has the highest antidiabetogenic phytochemicals.

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The combined impact of germinated endosperm and tuber had a significant level of antidiabetic action.

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Both foodstuffs were rich with a complex carbohydrate, fiber, zinc, minerals, as well as phytochemicals.

Is elephant foot yam (Amorphophallus paeoniifolius) tuber detrimental to patients with diabetes? (Or a myth?)

Elephant foot yam is widely consumed as a vegetable and locally known as 'Ol' in Bangladesh. However, taboos regarding elephant foot yam are the prominent barrier for diabetic patients to consume this tuber. The study aims to judge the concept scientifically. The literature review showed that elephant foot yam tuber is a good source of carbohydrates, protein, fiber, and minerals but low in fat. Secondary metabolites viz. phytochemicals of this tuber had a significant anti-hyperglycemic effect. In conclusion, elephant foot yam tuber is safe and beneficial for patients with diabetes.

Interactions between beef salt-soluble proteins and elephant foot yam (Amorphophallus campanulatus) flour in heat-induced gel matrix development

The objective of this study was to observe the interactions between salt-soluble proteins extracted from beef and elephant foot yam (Amorphophallus campanulatus) flour in heat-induced gel matrix development. The effect of salt concentration; 0.5%, 1.0%, 1.5%, and 2.0% in weight/weight basis (w/w), during protein extraction on pH, salt-soluble protein concentration and myofibril fractions of beef extract was determined firstly, and no significant effect was found. The beef salt-soluble proteins extracted using salt solution at different concentrations were then added with elephant foot yam flour at 5%, 10%, and 15% w/w, gelatinized at 90°C for 20 min, and cooled down at 4°C for 12 h. The interactions between beef salt-soluble proteins and elephant foot yam flour resulted in an improved gel strength (p < 0.01) and the addition level of elephant foot yam flour affected the pH, instrumental color, moisture, crude protein, and ash content significantly. The addition of elephant foot yam flour also reduced the size of the pores in the gel matrix as shown by scanning electron microscope (SEM) photographs. These suggest that elephant foot yam flour well interacts with beef salt-soluble proteins to form gel matrix.

Rock inhabiting potassium solubilizing bacteria from Kerala, India: characterization and possibility in chemical K fertilizer substitution

The role of rock inhabiting bacteria in potassium (K) solubilization from feldspar and their application in crop nutrition through substitution of fertilizer K was explored through the isolation of 36 different bacteria from rocks of a major hill station at Ponmudi in Thiruvananthapuram, Kerala, India. A comprehensive characterization of K solubilization from feldspar was achieved with these isolates which indicated that the K solubilizing efficiency increases with decrease in pH and increase in viscosity and viable cell count. Based on the level of K solubilization, two potent isolates were selected and identified as Bacillus subtilis ANctcri3 and Bacillus megaterium ANctcri7. Exopolysaccharide production, scanning electron microscopic and fourier transform infrared spectroscopic studies with these efficient strains conclusively depicted the role of low pH, increase in viscosity, and bacterial attachment in K solubilization. They were also found to be efficient in phosphorus (P) solubilization, indole acetic acid production as well as tolerant to wide range of physiological conditions. Moreover, the applicability of K containing rock powder as a carrier for K solubilizing bacteria was demonstrated. A field level evaluation on the yield of a high K demanding tuberous vegetable crop, elephant foot yam (Amorphophallus paeoniifolius (dennst.) nicolson) established the possibility of substituting chemical K fertilizer with these biofertilizer candidates successfully.

Rapid and sensitive detection of Dasheen mosaic virus infecting elephant foot yam by reverse transcription loop mediated isothermal amplification of coat protein gene

Dasheen mosaic virus (DsMV), the pathogen causing mosaic disease of elephant foot yam (Amorphophallus paeoniifoilius) is disseminated mainly through vegetative propagation of the tubers. For the rapid and sensitive detection of the virus, a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay based on the coat protein gene has been developed. A final concentration of 5.4 mM magnesium sulphate and 0.7 M betaine in the reaction mixture was found to be optimum for getting characteristic ladder like bands of the amplified product after gel electrophoresis. The reaction was set at 65°C for 50 min followed by reaction termination at 86°C for 5 min in a water bath. The sensitivity of the assay was found to be 100 times higher than that of RT-PCR. The virus was indexed successfully from tubers of elephant foot yam. In tube detection of the DsMV was carried out using fluorescence detection reagents. The assay was validated with field samples from various regions of Kerala state, India.