Bananas were washed, peeled, cut into slices (0.3–0.4 cm thickness) and immersed in a dilute sucrose solution (0.5% w/w) for 15 min according to the commercial process. Banana slices were washed, drained and weighed before the frying and coating application.Before frying, banana slices were coated by dipping them into the hydrocolloid coating solution for 10 min at a ratio of banana slices to coating solution of 15:1. A colander was used to pick up the coated slices and they were allowed to drip for 30 s. The weight of coating solution before and after dipping the slices was recorded to determine the weight gain. Both coated and uncoated banana slices were used to test the frying conditions. A vacuum fryer
equipped with a centrifuge that had all been made at the Department of Food Engineering was used in this experiment and is shown in Fig. 1. A batch of 10 kg of banana slices was placed in the vessel and fried in 60 L of palm oil under vacuum (2.66 kPa) at 89 C for 90 min. The vacuum fry temperature was controlled during the process and was constant, to remove any effect of frying temperature on oil absorption. After vacuum frying, the fried banana chips were centrifuged at two different speeds—either 140 rpm (normal speed used in vacuum frying) or 280 rpm (speed adjusted from 140 rpm to 280 rpm using an inverter) for 5 min to remove the frying oil. This post-frying centrifuge step was tested to study
its efficiency in the vacuum-frying process. Then, the excess frying oil on the samples was removed under atmospheric pressure at 800 rpm for 4 min. Finally, a sample of 250 g of fried banana chips was packed in each aluminum foil bag and flushed with nitrogen gas to prolong the shelf life of the product, sealed and kept at room temperature (27 C) prior to assessment.The treatments studied in this work were: (1) frying conditions at a normal centrifugation speed (140 rpm) as the control; (2) samples coated with xanthan gum; (3) samples coated with guar gum;(4) frying conditions at a higher centrifugation speed (280 rpm) as a high speed test without any coating treatment; and (5) samples coated with guar gum and a high centrifugation speed (280 rpm).