外文文献.pdf

ELSEVIER Journal of Food Engineering 26 1995 431 442 Copyright 0 1995 Elsevier Science Limited Printed in Great Britain All rights reserved 0260 8774 95 9 50 0260 8774 94 00065 4 Abrasive Peeling of Potatoes K K Singh revised version received 13 June 1994 accepted 3 October 1994 ABSTRACT For the processing of potatoes in any form removal of peel is an important unit operation Hence a power operated batch type potato peeler was developed and its pegormance was evaluated The main parts of the machine are a peeling drum and a water spraying unit The peeling drum with protrusions on the inside surface rotates and detaches peel from potatoes by abrasion The water spraying unit washes the potatoes and simultaneously peel is removed from the drum through the perforation along with the flow of water The capacity of the machine is 100 kglh with a peeling ejjiciency and peel losses of 78 and 6 respectively The machine costs around Rs 6500 00 250 along with an electric motor and is suitable for a small scale processor of potato chips and other products The estimated cost of peeling of 1 ton potatoes is only Rs 100 00 3 85 NOTATION 4 Equivalent diameter mm L B T Length breadth and thickness respectively of the tuber mm Peeling efficiency Power requirement W Q Batch load of potatoes kg r Correlation coefficient t Peeling time min Present address PHTC Agricultural and Food Engineering Department India Institute of Technology Kharagpur 721302 India 431 432 K K Singh B D Shukla Peel losses Spheric INTRODUCTION The total annual production of potatoes in India is about 15 million tons and a substantial amount of it is lost at various stages of post harvest operations mainly due to inadequate storage facilities Subrahmanyam 1986 Hence appropriate processing technology and equipment are essential to produce potato food products on a small scale It will help to reduce the losses and generate income and employment in the rural or semi urban areas Removal of peel is one of the important unit operations for the further processing of potatoes in any form The potato chip is a very popular snack food in India For making chips the important preparatory operations are washing and peeling Hand peeling is traditional in India and is tedious and time consuming Moreover the loss of flesh is very high However the potato processing industry uses lye peeling Since in lye peeling process the heat ring is formed below the surface of the potato due to tissue damage and polyphenol enzyme activity it is not recommended for making the chips Huxsoll 2 driven shaft 3 V belt 4 waste water and peel collection tray 5 bolts and nuts 6 washing system assembly 7 peeling drum shaft assembly 8 V pulleys 9 bearing block All dimensions in mm from the drum and simultaneously wash the peeled potatoes A water collection trough to drain out the water and peels has also been provided beneath the drum EXPERIMENTAL PROCEDURE The Kufri Jyoti variety of potatoes Solanum tuberosum L about 4 months old were used for the experiment The experiment was conducted during the 434 K K Singh B D Shuklu Fig 2 Side view of potato peeler 1 frame assembly 2 foundation of motor 3 inlet and outlet cover 4 on off valve 5 water supply connection pipe All dimensions in mm year 1991 2 The length breadth and thickness of potatoes were measured using a Vernier calliper The following formulae were used to calculate the equivalent diameter D and sphericity C J of the potatoes Mohsenin 1970 D LBT 3 where L is the length B is the breadth and T is the thickness and Abrasive peeling of potatoes 435 Details of Abrasion Fig 3 Details of abrasive drum used in potato peeler all dimensions in mm For determination of the peel content five samples of 200 g each were weighed separately and recorded The potato samples were boiled in water for 05 h to loosen the peels After cooling the boiled potatoes at room temperature 30 32 C for about 05 h the peels were separated from the flesh manually The peels and potatoes were then dried in an air oven at 80 C for about 6 h The peel percentage was then calculated by using following formulae Peel content db Dried wt of peel x 100 Dried wt of potato sample The machine was set for the experiment A sample of five potatoes was weighed individually and marked for identification For marking the potatoes were punched with a pin and different colour dyes were poured on each sample These marked potatoes were then mixed with the experimental batch load in the drum For experimental purposes a known quantity 5 10 15 and 20 kg of potatoes was fed into the drum The inlet pipe of the water spraying unit was connected to a water tap The drum was then rotated at speeds of 30 and 40 rev min The speed was varied by changing the pulley of the drum shaft The marked samples were taken out for analysis after 4 6 8 and 10 min The samples were gently wiped with blotting paper to remove the surface moisture and weighed immediately The peel content of these potatoes was determined with the help of the above mentioned formula The water drained was collected and weighed to determine the quantity of water required to perform the operation 436 K K Singh B D Shukla Each experiment was carried out in triplicate and average values are reported Peeling efficiency s Fraction of remaining on peeled potato 1 x 100 Fraction of peel on raw material The percentage peel losses were determined by using the following formula Willard 1971 Peel losses a Weight of raw potatoes Weight of peeled potatoes x 100 Weight of raw potatoes RESULTS AND DISCUSSION The mean equivalent diameter of the potatoes used for the experiments was found to be 62 mm with a standard deviation of k4 mm The mean sphericity and peel content were determined as 0 65 and 1 38 respectively Figures 4 and 5 show the relationship between time and peeling efficiency at different batch loads from 5 to 20 kg for drum speeds of 30 and 40 rev min respectively Drum speed 30rpm 6 Time t h Fig 4 Relationship between time and peeling efficiency at different batch loads 5 kg A 10 kg II 1 5 kg o 20 kg Abrasive peeling of potatoes 437 Drum speed COr pm 20 1 I I I I I 2 L 6 8 10 12 Time t h Fig 5 Relationship between time and peeling efficiency at different batch loads 5 kg A 10 kg 15 kg o 20 kg Regression on the data leads to the following equations for batch loads of 5 10 15 and 20 kg and speeds of 30 and 40 rev min respectively At 30 rev min drum speed v 35 28 20 48t 0 72t2 r 0 98 1 v 12 32 16 61t 0 59t r 0 99 2 j 11 78 10 32t O 21t r2 0 99 3 rj 18 72 8 65t 0 19t2 r2 0 98 4 At 40 rev min drum speed Y 29 77 20 93t 0 81t2 r 0 99 5 ij 26 66 22 15t 0 95t2 r 0 99 6 r 31 95 1 56t 0 53t r2 0 89 7 13 36 10 11t 0 23t2 r 0 98 8 It is clear from Figs 4 and 5 that peeling efficiency increases with time At higher times potatoes get more chances to remain in contact with the abrasive surface and thereby more peel is removed from its outer surface thus the peeling efficiency increases It is also observed that initially the peeling efficiency increases with increasing batch load but this trend is not continued beyond 6 min Table 1 This may be due to the fact that at the initial stage of peeling only the outer surface of the potatoes is removed but if the peeling continues beyond 6 min at the higher batch load some potatoes are overpeeled whereas some are underpeeled which affected the trend of the result 438 K K Singh B D Shukla The peeling efficiency increases with an increase in drum speed 30 40 rpm At higher speeds potatoes come more frequently in contact with the abrasive surface of the drum and hence more peel is removed increasing the peeling efficiency Figures 6 and 7 show the effect of peeling time on peel losses at different batch loads from 5 to 20 kg for drum speeds of 30 and 40 rev min respectively Regression analysis on the data leads to the following equations for batch loads of 5 10 15 and 20 kg and speeds of 30 and 40 rev min respectively At 30 rev min drum speed A 10 kg 15 kg o 20 kg 2 Drum speed 4Orpm P 0 6 8 10 12 Time t h Fig 7 Relationship between time and peel losses at different batch loads x 5 kg A 10 kg 15 kg o 20 kg Abrasive peeling of potatoes 441 sod I 1 I 5 10 15 20 Batch load Q kg Fig 8 Relationship between batch load and power requirement of the peeler 0 30 rev min A 40 rev min TABLE 2 Cost Economics of the Peeler for Peeling Potatoes 1991 92 Economic parameters Value Working capital Rs US Annual fixed cost Rs US Capital investment Rs US Hourly variable cost Rs US Annual variable cost Rs US Total annual cost Rs US Cost of operation Rsih US h Cost of processing R on US ton Custom hiring charges Rsiton US ton Annual sales revenue Rs US Annual net profits Rs US Break even point in terms of number of operations h quantity handled tons Pay back period years Return on investment Employment generation per machine man days year 169 6 50 2202 84 70 6551 252 00 5 0 19 8000 307 69 10202 392 38 6 37 0 245 100 3 85 200 7 69 20480 787 69 10278 395 30 282 22 60 0 603 156 89 305 1 US 26 Indian rupees Rs A speed of 30 rev min batch load of 20 kg and time of 8 min were found to be the best combination because of higher peeling efficiency and lower peel losses With this combination of parameters the peeling efficiency and peel losses were 78 and 6 respectively If the time of loading and unloading the potatoes manually was 4 min and the actual peeling time was 8 min the capacity of the machine was found to be 100 kg h The total 442 K K Singh B D Shukla quantity of water required to drain the peels and wash the potatoes was found to be 1 25 litres kg of potatoes The cost of fabrication of the peeler was estimated at Rs 6500 00 US 250 An economic analysis was calculated for peeling potatoes by comparing the machine costs to that of traditional hand peeling Working capital investment cost of operation per hour and cost of peeling per kg of potatoes break even point pay back period return on investment and employment generation were estimated using standard procedures in order to determine the economic viability of the equipme