Comparative assessment of different processing methods used for minimization of bitterness in Bitter gourd

Abstract

The present study was carried out to evaluate the comparative effect of different processing methods used for minimization of bitterness in Bitter gourd. For each treatment 1 kg raw fruit was taken, prior to processing samples were washed thoroughly;
followed by peel removal, seed removal and slicing into equal pieces (4 cm). Sample thus obtained were subjected five treatments viz; (i) Soaking in salt water followed by heat treatment, (ii) Microwave heating, (iii) Shallow-frying, (iv) Soaking in buttermilk and (v) Roasting. Bitter gourd (4 cm) slices (500g) were dipped in 1000 mL brine solution (35% wt. by volume) for 60 min at room temperature using a stainless-steel bowl. In second stage these samples were heat treated by transferring in boiled distilled water 1000 mL for 5 min up to 96 °C. Microwave heating of slices (460g) was carried out at grill mode of
Microwave oven at 110 °C for 10 min. Shallow frying of slices (482g) was done using 4-5 mL mustard oil at 100-110 °C for 10-12 min. For Buttermilk treatment the slices (437g) were dipped in 1000 mL buttermilk for 1 hr at room temperature. Roasting treatment for Bitter gourd slices (446g) was given by using a stainless-steel pan 70-90 °C for 15-16 min, till attainment of golden-brown colour from dark green. After processing sensory analysis and colour analysis (colourimeter) was done and remaining samples of each treatment was converted into powder by preparing the paste in kitchen grinders and later on its drying. The stored powders of processed samples were used for estimation of different phytochemicals responsible for bitterness in Bitter gourd. Saponin content (mg DE/g), Cucurbitacins (mg GAE/mL), Total phenolic content (mg GAE/g), alkaloid
content (g/100g) and flavonoids content (mg QE/mL) were estimated. Both Saponins and cucurbitacins were found decreased, in all treated samples. Samples treated with salt solutions followed by heat treatment had shown minimum level of saponin and
cucurbitacins that is (0.18mg DE/g and 206 µg Cu/mL), respectively. The Total phenolic content of all treated samples was found increased (180-249 mg GAE/g) in comparison to fresh Bitter gourd (62 mf GAE/g). Alkaloid and flavonoids content of processed Bitter gourd samples were found both decreasing and increasing in different treatments. Colour degradation of Bitter gourd was recorded in term of L, a and b values. The negative values of a ranging from -2 to -485 with a positive score of b value 20 to 35.9 indicated the transformation of green colour into greenish-yellow colour. Soaking in salt water followed by heat treatment was considered appropriate processing treatment for minimizations of bitterness and retainment of organoleptic characteristics.