Indian J. Plant Physiol., 2003 (Specia l Issue) pp. 489-494
PROCESSING QUALITY AND CIPC RESIDUES IN POTATOES STORED AT lO-12°C IN
COMMERCIAL COLD STORES APPLYING CIPC
R. EZEKIEL 1' , BRAJESH SINGW, DINESH KUMAR2AND VIjAY PAUV " 'Cen tral Potato Research Institute, Shimla- 17100 I, H.P.
2Central Potato Research Institute Camp us, Modipuraf!l-250 110, V.P.
SUMMARY Potatoes stored at 10-12°C and 85-95 % llH in commercial cold stores at five cities in northern and central India were analysed periodically for processing quality and Isopropyl N-(3-chlorophenyl) carbamate (CIPC) residue levels. Tubers stored at 10-12°C produced chips of acceptable colour as compared to dark coloured, unacceptable chips produced by tubers stored at 2-4°C. The lighter chip colour could be related to lower level of reducing sugars . Cultivar Kufri Bahar accumulated excessive reducing sugars resulting in dark colour chips. Tubers of cultivars Kufri Jyoti and Kufri Lauvkar, produced and stored at Indore and Ujj ain respectively were found to be suit a ble for processing. CI PC re sidue levels va rl- d con siderably and th e maximum CIPC residue level observed in peel ranged from 0.2 to 16.1 mg/kg fw and in unpeeled tubers, it ranged from 0.03 to 2.7 mg/kg fw. Thi s is within the acceptable limit of 30 mg/k g tuber. Key words: CIPC residue, potato, processing quality, storage
INTRODUCTION CIPC (Isopropyl N-(3-chloroph enyl) carbamate) also known as chlorpropham is used for sprout inhibition in stored potatoes meant for processing and table purposes in many countries (Kleinkopf et al. 1997). The advantage of this sprout suppressa nt on potatoes is that it is cost effec tive and can be used as post-h arvest application unlike sprout suppress ants like Maleic Hydrazide which is used as a pre-harvest spray . CIPC was registered for use in India as a sprout suppressan t on pota toes only in 1998 and therefore, its effect on the storage behaviour of Indi an potato varieties is not well docum ented. Small sca le studies have been done und er non- refri gerated storage using dust formul ation of CIPC (Singh and Kaul 1999) but large sca le storage studies using aerosol formul ation for fogging potatoes in large commercia l cold stores have not been carried out in India so far. CIPC residue analysis is necessary to make sure that the residue *Corresponding author; e-mail:
[email protected] **Present address: Division of Plant Physiology, IARI, New Delhi 110012
Indian J. Plant Physiol. , 2003 (Special Issue) pp. 489-494
level does not excee d the recommended maximum limit. The'aim of this study was to determine the effect of CIPC on th e processin g qu ali ty of potat oes and res id ue concentrations of CIPC in potatoes, stored in com mercial cold stores at 10- 12°C .
MATERIALS AND METHODS Processing quality of potatoes and CIPC residue levels were monitored in commercial cold stores located at five cities in three states in northern and central India, during 200 1. The details of the cold stores are given in Table 1. In these cold stores, well-cured potatoes were stored at 1O- 12°C and 85-95% RH. CIPC was applied twice on the dates given above . CIPC was applied as a thermal aeroso l (fog) through an inlet fixed at about 3 feet above the ground level. A fogger (Dyna fog, USA) was used for CIPC application and the dose applied was 35 ml (50% a.i.) of a commercial preparation of CIPC called "Oorja" manu factured by United Ph osphorus Ltd., Mumbai. After application, the stores were closed for 48 hours to allow CIPC aeroso l to sett le on the potatoes and
489
R. EZEKIEL et al.
Table 1. Details of cold stores covered in the study Name of cold storage
Narang Ice & Cold Storage , Indore (M.P.) Indore Ice & Cold Storage , Indore (M.P.) Chatrakaran Cold Storage, Indore (M.P.) Ujjain Ice & Cold Storage , Ujjain (M.P.) U.S. Katiyar Industries, Ujjain (M.P.) Bhairav Cold Storage , Deesa (Gujarat) Bhawani Cold Storage, Deesa (Gujarat ) Tyagi Sheet Grah, Balna (U.P.) Bhagat Ji Cold Storage, Meerut (U.P.) Ganesh Cold Storage , Meerut (U.P .)
Variety
Kufri Jyoti Kufri Jyoti Kufri Jyoti Kufri Lauvkar Kufri Lauvkar Kufri Chandramukhi Kufri Chandramukhi Kufri Bahar Kufri Jyoti Kufri Jyoti
then ventilated, to flush out the accumulated CO . For control, tubers were stored at 2-4°C and 90-95 % RH , which is the normal storage temperature in cold stores. Samples were collected randomly from each cold store periodically and were analysed for chip colour, reducing sugar and dry matter content. CIPC residue was analysed in peel and unpeeled tubers. Chip colour was scored on a scale of 1-10 of increasing dark colour and a chip colour score up to 5 is considered acceptable. Reducing sugars content was determined by Arsenomolybdate method (Nelson 1944). Dry matter content was determined by drying finely chopped tubers in an hot air oven at 80°e. CIPC residue was analysed in peel and unpeeled tubers using HPLC (Lachrom, Germany). For the analysis of CIPC residues , tuber samples were collected randoml y from bags placed in ground floor. For the site effect, tuber samples were collected from bags placed at 1 meter from the fogging point and from bags placed at 7 to 20 meters away from the fogging point depending upon the width of the chamber. For height effect, tuber samples were collected from bags placed at the ground and first floors. For extraction of CIP C from potato, the method earlier standardized in the laboratory was used (Singh and Kaul 1999). The concentrated extract obtained after extraction was dissolved in 200 /11 of HPLC grade Hexane. A modified procedure developed by Wilson et al. (1981) was used for HPL C analys is. A sample of 20 /11 was injected into the HPLC sy ste m ha ving fo llowing conditions : a Rheodyne inj ector ; a Lachrom L-7100 iso crati c pump (having n ow rate of 1.0 ml/min); a
490
Quantity stored (tonnes) 900 250 2300 840 2160 160 400 2700 600 200
Date of storage
05.2.2001 12.2.2001 22.1.2001 07.2.2001 16.2.2001 20.3.200 1 20.3.2001 01.3.2001 15.2.2001 13.3.2001
Date ofCIPC application l SI
2 nd
16.3.2001 16.3.2001 17.3.2001 20.3.2001 18.3.200 1 20.4.2001 20.4.2001 31.3.2001 22.3.2001 12.4.200 1
26.4 .2001 07.4 .2001 08.5 .2001 06 .5.2001 17.4.2001 31.5 .2001 31.5 .2001 11.6.2001 20.5 .2001 10.6.2001
Puro spher RP-18e column 250 x 4 mm (maintained at 25°C temperature) with a solvent system of methanol acetonitrile-water (35:35:30); a Lachrom L-7420 UV visible detector set at 236 nm and 0.04 absorbance units full scale. Peak area was used for quantification of CIPC in the sample with the help of CIPC standard solution. Statistical analysis was done using MSTAT C 4.0 version softw are for computers.
RESULTS AND DISCUSSION Chip colour varied significantly amongst locations. The chip colour at Indore and ~Ujj ain was better than that at Meerut but there was no significant difference between Indore and Ujjain (Table 2). Although the reducing sugar content was higher at these two locations compared to Meerut, it was well below the acceptable level of 250 mg per 100 g tuber fw. The difference between the two cold stores at Indore and Meerut in chip colour was significant but at Ujjain there was no difference. The reducing sugar content showed significant difference between cold stores at Ujjain and Meerut but not at Indore . Dry matter content was significantly higher at Indore and Ujjain as compared to Meerut. There was no significant change in chip colour with increase in storage duration . Reducing sugar and dry matter content increased with increase in storage duration (Table 2). Chip colour was very dark in tubers stored at 2-4°C whereas in those stored at I0- 12°C, it was acceptable in three cultivars. Only Kufri Bahar showe d unaccept ably high chip colour score of 8 (Fig. 1). The reducing sugar Indian J. Plant Physiol .. 2003 (Special Issue) pp. 489-494
EFFECT OF CIPC ON QUALITY OF POTATOES
Table 2. Processing quality of potatoes stored at lO-12°C and 85-95 % RH at three locations Location
Cold store
Days of storage
D,
Indore (MP)
°2 0) II
Ujjain (MP)
II
Meerut (UP)
D, D2 D) D, D2 D) D, D2 D) OJ
°2 0) II
DJ D2 D)
LSD (0.05) Location (L) Cold store (C) Days of storage (D) LxC LxD CxD LxCxD
Chip colour score* (mg/IOO g fw) 35 83 157 42 90 164 39 88 162 36 84 133 88 118 150 63 93 125
Reducing sugars 79.0 61.5 102.5 88.0 60.0 112.0 69.5
Dry matter (%)
2.0 1.5 3.0 4.0 2.5 3.0 2.0 2.0 3.0 2.0 2.0 3.0 3.0 3.5 2.0 3.5 6.0 5.0
213.5 43.5 43.0 171.5 22.0 40.0 37.5 49.0 148.0 139.0
22.6 23.1 26.3 21.3 24.5 24.9 23.7 25.1 25.1 24.7 24.0 25.7 20.6 23.0 22.9 21.8 21.9 22.1
0.70 0.57 N.S. 0.99 1.21 N.S. N.S.
16.1 13.2 16.1 22.8 27.9 N.S. N.S.
1.3 N.S. 1.3 N.S N.S. N.S. N.S.
no
* Scored on a scale of 1-10 of increasing dark colour.
content was more than 1000 mg per 100 g tuber fw in three cultivars and in Kufri Bahar it was more than 3000 mg at 2-4°C. Whereas, at lO-12°C, the reducing sugar content varied from 103 to 305 mg (Fig. 1). There was not much difference in the dry matter content of tubers stored at 2-4°C and 1O-12°C. Maximum CIPC residue levels in peel and unpeeled tubers collected from Meerut were significantly lower than that at Indore and Ujjain (Fig . 2A). There was no significant difference in CIPC residues in tubers from Indore and Ujjain. The differences in minimum CIPC residues in peel and unpeeled tubers were non-significant (Fig. 2B) . The CIPC residues in peel and unpeeled tubers were higher in tubers collected from bags placed near the fogging point as compared to those away from the fogging point (Fig . 2e). The CIPC residue levels in peels and unpeeled tubers were higher in tubers collected from
Indian J. Plant Physiol., 2003 (Special Issue) pp. 489-494
bags and crate s placed in the ground floor as compared to those from the first floor (Fig. 2D). Potatoes grown and stored at Indore and Ujjain produced lighter colour chips compared to those stored at Meerut. Tubers of variety Kufri Lauvkar grown in Ujjain district are reported to produce good quality chips with a colour score of 3 (Ezekiel et al. 2002) . Chips produced from potatoes stored at 2-4°C were much darker than those stored at 10-12°C. Chips made from tubers stored at lower temperatures are reported to be darker than those stored at higher temperatures and the darker chip colour was attributed to higher reducing sugars content in tubers stored at 3.30C than in those stored at 7.2 or 11.1°C (Smith 1987). In our experiment also the reducing sugars concentration in tubers stored at 2-4°C were 6-10 time s higher than those at 1O-12°C. Since reducing sugars accumulate in exce ssive quantities at 491
R. EZEKIEL et al. 12
C32-4C c:::I10- 12C
10
3500 3000
m Cl
::l
co
I a a
::l
'a,
OJ
5
·u "0
a:
2500
Cl
c
Cl
2000 1500 1000 500 0 30
25
20
Q;
'"E'" ~
0
~
IS
10
Cultivar
Fig. 1. Chip colour, reducing sugar and dry matter content in tubers of four cultivars after storage (120 days in case of Kufri Chandramukhi and 150 days in case of other three cuItivars) at two temperatures
temperatures below 4.4 °C, storage at lOoC or above is recommended for storing potatoes meant for processing (Smith 1987). There was not much change in the reducing sugars content up to about 3 months of storage at 10 12°C with CIPC treatment and it increased to more than 100 mg after about 5 months of storage at Indore and Ujjain. However at Meerut, the reducing sugar content remained less than 100 mg even after 5 months of storage in one cold store and was more than 100 mg after 3 months of storage in another cold store. Linneman et al.
492
(1985) have reported that the reducing sugar content was around 150 mg/lOO g fw in tubers stored for 12 weeks at 7 and 16°C with CIPC treatment. Although the reducing sugar content increased towards the end of the storage period, it was within the acceptable limit of 250 mg/lOO g fw for chips (Van Es and Hartmans 1981). Dry matter content generally was higher by 1-3.6% after about 5 months of storage at Indore and Ujjain. At Meerut, it was higher by 2.3 % in one cold store and there was little difference in the other cold store. In general, dry matter
Indian J. Plant Physiol.. 2003 (Special Issue ) pp. 489-494
EFFECT OF CIPC ON QUALITY OF POTATOES
content of potatoes increases with storage time indicating an increase in percentage of solids in the tubers as a result of greater loss of water by evaporation than loss of solids by respiration (Smith 1987). Cultivars differed in their storage behaviour. Reducing sugar accumulation was much higher in Kufri Bahar at both the storage temperatures when compared to Kufri Jyoti, Kufri Lau vkar and Kufri Chandramukhi . The reducing sugar content in Kufri Bahar was 172% higher than that in Kufri Jyoti at 2-4°C and even at 1O-12°C, it was 196% higher than that in Kufri Jyoti . The se results indicate that cultivar Kufri Bahar is not suitable for processing. The other three cultivars are reported to be suitable for processing (Ezekiel et al. 1999). While the efficacy of CIPC in suppress ing sprout growth has been observed consistently in all the earlier studies , there has been a considerable variation in the
CIPC re sidue lev el s reported . Thi s could be due to variations in the formulati on used, storage temperature and storage management practic es, Ma ximum CIPC residue level was observed after second application and the maximum value s in peel ranged from 0.2 to 16.1 mg/ kg fw and in unpeeled whol e tuber from 0.03 to 2.7 mg/ kg fw . Corsini et al. (1979) have reported a residue level of IS to 85 ppm in peels and less than 1 ppm in peeled tuber s. Kleinkopf et al. ( 1997) have reported a residue level of 7 mg/kg fw in unpeeled, unwa shed tubers four day s after the first application and 12 mglkg fw after second application and 240 day s of storage. Minimum residue levels observed ranged from 0.06 to 1.2 mglkg fw in peel and from 0.07 to 0.3 mglkg fw in unpeeled tubers. Thu s, there was considerable variation in the CIPC residue level within a chamber. This is because not all sites within storage recei ve the same dosage of CIPC at
15 . - - - - - - - - - - - - - - - - - , BJ Peel, cold store -1 A 14
F ~
E
on, 13 E ::> E
.~
::;;
B
13 12 -
DPeel, cold store -2 W Unpeeled tuber, cold store-1
F
11 10
.Unpeeled tuber, cold store-2
.:
4
'c
3 2
~
0.2
1
o
0 Indore
Ujjain
Meerut
Indore
Location of cold store
Ujjain
Meerut
Location of cold store
2.5 Il!lBags-Peel
mPeel DUnpeeled tuber
C 2
LSD, .o5 Peel: NS Unpeeled tuber: 0.43
Frn .:
'0
:g
'iii
~
0.4
0 o,
0 o,
U
U
0.2
0.5
0
0 Awey
Near Site from fogging point
First floor
Ground floor Floor level
Fig. 2. Maximum and minimum CIPC residues in tubers collected from cold stores located in three cities (A and B); CIPC residue in tubers collected from bags placed near and away from the fogging point (C) and in tubers collected from bags and crates placed in groun d and first floor (D)
Indian J. Plant Physiol., 2003 (Special Issue) pp. 489-494
493
R. EZEKIE L et at.
the time of treatment (Corsini et al. 1979). The residue levels were higher at Indore and Ujjain compared to Meerut and this was due to the relatively higher dose of Clf'C applied at these two places . Clf'C residue was relatively higher in tubers stored near the fogging point compared to those stored away from the fogging point. Cll'C residue levels have been found to be higher at the bottom of potato piles when the applica tion was made through the ventilation system, as the Cll'C fog enters the store at the bottom and rises through the pile (Corsini et al. 1979). There was no significant difference in the Clf'C residue levels in tubers stored in crates and bags, indi cating that the entry of Clf'C into the bag was satisfactory. The residue levels were relatively higher in the ground floor as compared to the first floor. The reason could be that as the Clf'C fog applied in the ground floor rises through the bags of potatoes, relatively more of it might settle on the potatoes and bags in the ground floor. Kleinkopf et al. (1997) has also reported higher Clf'C residue levels in potatoes stored near the bottom of the pile than those stored near the top. A tolerance limit of 30 ppm has been given by EPA (EPA 1996). The Cll'C residue levels reported here were well within this limit and therefore it may be concluded that Clf'C treated potatoes are safe for human consumption one month after treatment.
ACKNOWLEDGEMENTS The financial support provided by Agricultural and Processed Food Products Export Development Authority (APEDA), New Delhi and National Horticulture Board (NHB) , Gurgaon for this projec t is gratefully acknowledged. The authors are thankful to the Director, ePRI, Shimla for his encouragement and facilities, and to Shri Suresh Kumar for technical assistance. The
494
authors also thank all the cold store owners and United Phosphorus Ltd., Mumbai for their cooperation.
REFERENCES Corsini, D ., Stallkne cht , G. and Sp arks, W. (19 79). Chang es in chloropropham residues in stored potatoes. Am. Potato J. 56: 43 50. Environmental Protection Agenc y (1996) . Registration Eligibility Decision . EPA 738-R-96 -023. Ezekiel, R., Verma , S .C., Sukumaran , N.P. and Shekhawat, G.S. ( 1999). A Guide to Potato Processors in India. CPRI, Shimla. Ezekiel, R., Dahiya , P.S. and Shekhawat, G.S. (2002). Traditional Methods of Potato Storage in the Malwa Region of Madhya Pradesh. CPRI, Shimla . Kleinkopf, G.E., Brandt, T.L. , Frazier, M.J. and Moller , G. ( 1997). CIPC residues on stored Russet Burbank Potatoes: I. Maximum label application. Am . Potato J. 74: 107-117. Linneman, A.R., Van Es, A. and Hartmans, K.J. (1985). Changes in the cont ent of L-ascorbic acid , glucos e, fructose , sucrose and total glycoalkaloids in potatoes (cv. Bintje) stored at 7, 16 and 28°C. Potato Res. 28: 271-278. Nelso n, N.A. (1944 ). A photometric ada ptation of the Somogyi method for the determin ation of glucose. J. Bioi. Chern. 153 : 375-380. Singh, B. and Kaul, H.N. (1999). Analysis of chloropropham (CIPe) residues in stored potato tubers by gas chrom atography. Indian J. Plant Physiol. 4: 121-124. ,.. Smith, O. (1987). Transport and storage of potatoes. In: W.F. Talburt and O. Smith (eds.) , Potato Pro cessing, pp . 203-285 . Van Nostrand Reinhold, New York. Van Es, A. and Hartrnans, K.J. (1981) . Sugars and star ch durin g tuberization, storage and sprouting. In: A. Rastovski and Van Es (eds.), Storage of Potato, pp. 92-98 . Pudoc . Wageningen . Wilson, A.M ., Bushway, A.A. and Bushway , R.I . (1981). Residue analysis of Isopropyl N-(3-chlorophenyl) carbamate in fruits and vegetables using high-performance liquid chromatography . J. Agric . Food Chern. 29: 746-749 .
Indian J. Plant Physiol., 2003 (Special Issue) pp. 489-494
