Development and evaluation of a vacuum frying system for banana chips (Musa spp.)

Abstract

Frying is an indigenous cooking method. The deep fat frying produces crispy textured and tasty fruits and vegetable products with increased fat content. The property of oil and fried product gets degraded during deep fat frying. The vacuum frying could be an alternative technology that involves low frying temperature and pressure aids in reduced oil absorption in fried product and preserves the quality of frying oil. Accordingly an advanced vacuum frying system with dual chambers, oil storage and a frying chamber with de-oiling system was developed to produce vacuum fried raw and ripened banana chips. The developed vacuum frying system was batch type with product capacity of 12 kgh -1 and frying oil tank capacity of 30 l. The properties of the product and oil were evaluated and standardisation of process parameters was done with the developed vacuum frying system. The oil blend (Rice bran and Palm oil) at 80:20 was identified as suitable frying oil with high oxidation and thermal stability among coconut, rice bran, palm, corn and blended oils. Effective de-oiling was attained with removal of 74.1 and 71.4% oil, respectively, in VF-raw and VF-ripe centrifuged at 1000 rpm for 5 min. The vacuum frying with de-oiling nullified the effect of pre-treatments like blanching cum drying, freezing and gum coating for the production of VF-raw and VF-ripe. The quality parameters like oil content, moisture content, energy, texture, bulk density, true density, colour values, thickness expansion and sensory acceptability of vacuum fried raw and ripened banana chips were evaluated at different processing conditions. The processing conditions of vacuum frying at 105°C and 18 kPa for 13 min produced improved quality of VF-ripe with low oil content (13.35%), acrylamide content (122.8 μgkg -1 ), moisture content (0.869%), water activity (0.21), L * (57.28) a * (12.23), b * (56.4), yellowness index (131.3) bulk density (0.453 gcm -3 ), true density (1.38 gcm -3 ), thickness expansion (-74%) and good organoleptic properties with high sensory score of 8.6. The process protocol for the production of VF-raw has to be improved to attain consumer acceptability. The vacuum fried ripened banana chips processed at 105°C for 13 min, packed in 400 gauge LDPE with nitrogen flushed packaging showed good consumer acceptability upto 90 days of storage. After 90 days of storage, the products exhibited poor consumer acceptability due to reduced degree of crispness. The FFA value of the blended oil was within the acceptable limit upto 52 batches of frying at 105°C and 18 kPa for 13 min. The total polar compound of the blended oil increased from 9.5 to 15.7% after sixty batches which was within the safe level. The production cost formulated based on fixed and variable cost for per kg of vacuum fried raw and ripened banana chips was Rs.342/- and Rs.363/- respectively.