Development and evaluation of process protocol for vacuum fried bitter gourd chips (Momordica charantia)

Abstract

Bitter gourd (Momordica charantia) is commonly known as bitter melon or Karela in India. The estimated post harvest loss of bitter gourd was 25%. A realistic solution to reduce the post harvest loss in bitter gourd is the adoption of the appropriate processing technologies. The vacuum frying is an excellent promising technology, in which food is fried under low pressure and temperature. Vacuum frying reduces the oil absorption, less formation of acrylamide content, and retains the colour and nutrients present in fried products. The vacuum frying system consists of two main chambers namely, frying chamber and oil storage chamber. A de-oiling system is attached to frying chamber to remove the oil content in the final vacuum fried product. This vacuum frying system used for the study was batch type and had a capacity of 3 kg/ batch with oil tank storage of 30 l. After every batch of vacuum frying, chips and oil were collected for analysing the quality. The blended oil (rice bran and palm oil at 80:20) was used as frying oil and de-oiling was done at a speed of 1000 rpm for 5 min. Different pre- treatments were done for vacuum fried bitter gourd chips. Control (Un-treated) sample had the best qualities with less oil content (4.43 %), moisture content (0.264 %), hardness (1.422 N), water activity (0.250) and green colour retention (a*(-4.13)). Quality parameters like moisture content, water activity, oil content, bulk density, true density, hardness, energy content, acrylamide content, thickness expansion, colour values and sensory evaluation of vacuum fried bitter gourd chips were analysed at different frying conditions. The treatment condition at 100oC, and 9 kPa vacuum for a duration of 10 min produced good quality parameters with less oil content (4.011%), acrylamide content (56.52 ppb), hardness value (1.411 N), high retention of green colour (a*(-5.3)) and good organoleptic properties (Hedonic score of 8.7). The laminated aluminium flexible pouches with nitrogen flushing retained the quality of bitter gourd chips during the storage period. The TPC value of blended oil increased from an initial value of 9.4 to 24.21%, due to continuous usage of oil (70 times) under the vacuum frying process, and was within the safe limit. The FFA value of blended oil was within the acceptable limit upto 50 cycles of vacuum frying process.