Vol. 5 (4) : 285 - 288 (2003)

SUGARCANE

Post-harvest Quality Loss of Sugarcane Genotypes under Sub-tropical Climate : Deterioration of Whole Stalk and Billets Ishwar Singh and S. Solomon Indian Institute of Sugarcane Research, P.O. Dilkusha, Lucknow - 226 002, U.P., India

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Post-harvest quality of five mid-late maturing sugarcane genotypes (CoLk 9606, CoLk 8102, CoLk 9617, CoS 767, CoPt 84212) was evaluated during late -crushing season. Sugarcane variety CoPt 84212 showed tolerance to post-harvest sugar losses as evident from lesser reduction in CCS percent, purity coefficient and increase in reducing sugars and dextran after 7 days of staling. On the other hand variety CoS 767 recorded high contents of dextran and reducing sugars with more purity drop and less recoverable sugar in stale canes alongwith higher acid invertase activity in this variety during post-harvest storage. Our study suggests that cane logistics especial ly during late-mil l ing phase should be organized on the basis of sugar loss profile of cane varieties.

KEYWORDS : Sugarcane, genotypes, quality, post-harvest losses, dextran, reducing sugars, titable acidity index

The ex i s t i ng cane h a r v e s t i n g and supp ly management system operat ing in India, especial ly in s u b - t r o p i c a l cane g r o w i n g bel t is a se r ious impediment in attaining higher sugar recovery. In m a j o r i t y of sugar f a c t o r i e s , t ime lag be tween harvest ing to mill ing of cane ranges between 3 to 10 days, which entails huge losses in recoverable sugar ( sucrose) . Suga rcane va r ie t i e s there fore , play a crucial role in sustaining the recoverable sugar due to their difference in susceptibi l i ty to post-harvest deterioration (Balusamy et a l . , 1990; Chiranjivi Rao, 1989; Solomon et al . , 1997, 1999, 2001, 2003; Uppal and Sharma, 1999; Uppal et a l . , 2000). A large number of fac tors such as ambient t empera ture , humid i ty , na ture of va r ie ty , pe r iod of s to rage , activities of soluble invertases in cane, maturity status etc. are responsible for this difference (Solomon, 2000, 2002). During harvest ing to mill ing period biological losses (viz. inversion, acid, ethanol and microbial po lysacchar ides and dextran format ion) play a crucial role in loss of recoverable sugars in cane and milled juice, which determines the loss of sttcrose during staling (Solomon et al . , 2001, 2003).

Studies have indicated a decline in sucrose percent cane to the extent of 2.0 units within a period of 72

Author for Correspondence : S. Solomon e?-mail : drsolomonsushil@rediffmail.com

hours of harvest , depending upon the sugarcane genotype and mil l ing season (Solomon et a l . , 1999). Despite huge moni tory losses to sugar industry, the management approach to curb pos t -harves t sucrose losses is almost non-existent . This is mainly due to lack of informat ion regarding magni tude of post- harvest sugar loss in commercial cane varieties grown under different agro-cl imat ic condit ions. There is an ardent need to develop post-harvest quality profile o f c o m m e r c i a l cane v a r i e t i e s / n e w l y r e l ea sed genotypes in order to organize Cane logistics on sc ien t i f i c l ines and take a p p r o p r i a t e r emed ia l measures to reduce biological losses in field and milling tandem. In the present study ,five promising mid - l a t e m a t u r i n g s u g a r c a n e g e n o t y p e s were evaluated for their pos t -harves t qual i ty re tent ion capacity under sub-tropical condit ions, during late- crushing period. The quality loss in whole stalk and billets harvested cane has also been reported in this paper.

M A T E R I A L S AND M E T H O D S

A field exper iment was conducted at the research farm of the Indian Institute of Sugarcane Research, Lucknow to assess the post -harves t quali ty losses in five mid-late (CoLk 9606, CoLk 8102, CoLk 9617, CoS 767, CoPt 84212) maturing sugarcane genotypes during the crop season 2002-03. The crop was planted

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in 5-row plots (5.0 • 4.5 M 2 size) in randomized block design (RBD) with three replications. The sugarcane va r i e t i e s were ra ised acco rd ing to recommended practices followed in north India. The crop was harvested on April 01, 2003 and kept in heaps under natural field conditions for 7 days to assess the post-harvest quality losses. The average maximum and minimum atmospheric temperatures were 35.8 and 17.9 ~ C respectively, during the post- harvest storage period. The mean relative humidity was 58/19 % (M/E) with 2.0 mm rainfall on April 05 (Fig. 1).

Fig. 2 : Loss in cane weight during Post-harvest storage

Fig. 1 : Temperature and Relative Humidity during post-harvest

The composite sample of randomly selected canes from three replicates were used in this study for weight loss and evaluation of quality parameters. The TSS% ( B r i x ) in juice was recorded with Erma hand refractometer. The clarified juice was analysed for sucrose content with High Sensitive Polarimeter (Model SEPA 300, Horiba, Japan).

The purity co-efficent , titrable acidity, reducing sugars, dextran and invertase activity were assayed in juice "by the methods reported earlier (Solomon et al . , 1990, 2003).

RESULTS AND DISCUSION

As r epo r t ed ear l i e r by many sugarcane researchers, cane starts to lose weight by drying out as soon as it is harvested and moisture losses are relatively much higher during late-crushing period (Solomon et a l . , 1997). In our present study , variety CoS 767 showed highest loss in cane weight, while var ie t ies CoLk 8102 and CoPt 84212 r eco rded relatively less decline in cane weight after 7 days of staling (Fig. 2). Highest increase in TSS% was observed in genotype CoLk 9617 (20.96%), while variety CoLk 8102 showed significantly less increase in TSS (9.94%) during cane staling. The variety CoPt 84212 showed significantly less decline in CCS%, sucrose% juice and purity coefficient, with lesser

Fig..3 : Drop in CCS % and Purity during cane staling

formation of reducing sugars and dextran (Fig. 3-6). This situation was contrary in variety CoS 767 which recorded higher contents of dextran and reducing sugars with more puri ty drop and less recoverable sugar in stale canes. The post-harvest deterioration was found to be related to drop in juice pH and increase in t i t rable acidity index (TAI). Higher is the quality loss during post-harvest more is the drop in juice pH and increase in TAI. We observed comparatively less drop in ju ice pH and marginal increase in TAI in variety CoPt 84212 (Fig. 6). This variety also showed less acid invertase activity in juice extracted from stale cane (Fig. 7). Based on our study it could be surmised that variety CoPt 84212 was less prone to post-harvest sucrose loss as compared to other variet ies, during late milling period (climatic condit ions specified).

The post-harvest quality of sugarcane varieties the re fo re play a crucial role in sugar recovery , depend ing upon the c l ima te and m a n a g e m e n t p rac t ices . Fur ther , p r imary sucrose losses in sugarcane varieties are responsible for secondary losses in milling tandem due to inversion and dextran

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Fig. 4 : Change in dextran content during staling of cane

Fig. 6 : Titrable Acidity Index of five cane genotypes before and after staling

Fig. 5 : Increase in invert sugars during staling Fig. 7 : Change in acid invertase activity after cane staling

Table - 1 : Quali ty changes in whole cane and billets during post-harvest staling in sugarcane genotype CoLk 9617

Parameter Fresh (Whole cane) Stale (Whole cane) Bil lets (cut cane pieces) After 7 days After 7 days

Cane weight (g/ cane) 845 730 (-13.60) 645 (-18.93)

TSS% 19.84 24.00 (+20.96) 24.00 (+20.96)

Sucrose % juice 17.83 15.06 (-15.53) 13.92 (-21.93)

Purity Coefficient 89.86 62.75 (-30.16) 58.00 (-35.46)

CCS% 12.43 8.38 (-32.58) 7.22 (-41.91)

Reducing sugars (per 100 brix) 2.80 35.28 39.67

Dextran (ppm) 56 1725 2096

TAI (per 100 brix) 19.83 25.45 (-28.34) 25.67 (+29.45)

Juice pH 5.27 5.06 (-3.98) 4.82 (-4.36)

Fibre % cane 13.48 15.23 (12.98) 15.67 (+16.24)

Values given in parentheses are increase (+) or decrease (-) over control (~esh cane)

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f o r m a t i o n ( S o l o m o n et al., 2003) . This no t only l eads to loss in r e c o v e r y but a lso h a m p e r s no rma l p r o c e s s i n g o p e r a t i o n s and e x t r a i n v e s t m e n t on

san i t a t ion c h e m i c a l s .

The i n t r o d u c t i o n o f m e c h a n i z e d h a r v e s t i n g and

s u b s e q u e n t c h o p p i n g (b i l l e t s ) of canes r e s u l t e d in

fas te r qua l i t y loss , i f the t ime lag be tween h a r v e s t to

c rush is d e l a y e d b e y o n d 24 hours . The m e c h a n i z e d

ha rve s t i ng is b e i n g p a t r o n i z e d by some s u g a r mi l l s

l o c a t e d in sou th Ind i a . This m e c h a n i c a l h a r v e s t i n g

with c o n s e q u e n t d e l a y in p r o c e s s i n g o f b i l l e t s cou ld

affect fac tory e f f i c i ency and sugar qua l i ty in addi t ion

to pu l l i ng down r e c o v e r y . Ea r l i e r s tud ies by Egan

(1968) in A u s t r a l i a have p o i n t e d out s i g n i f i c a n t

a m o u n t o f p o s t - h a r v e s t s u g a r l o s s e s in c r o p

h a r v e s t e d by c h o p p e r harves te r . In th is s tudy we

o b s e r v e d 5 .33% m o r e loss in cane we igh t in b i l l e t s

as c o m p a r e d to the w h o l e cane , s u b j e c t e d to s ta l ing

under na tu ra l f i e ld c o n d i t i o n s for a p e r i o d o f one

w e e k ( T a b l e 1). B i l l e t s a lso r e c o r d e d s i g n i f i c a n t l y

h ighe r d e c l i n e in r e c o v e r a b l e sugar , pu r i t y and j u i c e

pH. Dex t r an and r e d u c i n g sugars con ten t s were also

s i gn i f i c an t l y h i g h e r in b i l l e t s as c o m p a r e d to whole

cane af te r 7 days o f s t a l ing (Table 1).

Our s tud ies have c l ea r ly e s t a b l i s h e d tha t pos t harves t qua l i ty o f each cane g e n o t y p e is an impor tan t p a r a m e t e r f rom f ac to ry ope ra t i ona l and p ro f i t ab i l i t y poin t of view. The re is an a rdent necess i ty to deve lop p o s t - h a r v e s t qua l i ty p ro f i l e o f suga rcane geno types , u n d e r c o m m e r c i a l c u l t i v a t i o n to m a x i m i z e suga r p r o d u c t i v i t y per se. The excess loss o f suc rose and as soc ia t ed pro~cessing p rob l ems in bi l le ts due to post- harves t de lay have been h igh l igh ted by many workers . H o w e v e r , i f m e c h a n i z e d h a r v e s t i n g ( c h o p p e r ha rves t e r s ) s y s t e m is i n t r o d u c e d in Ind ia , e s p e c i a l l y

in s u b - t r o p i c a l be l t , b i l l e t s s h o u l d be p r o c e s s e d wi th in 12 hours .

R E F E R E N C E S

Balusamy, M., Enyatullah, Shah, S. and Choklingam, S. (1990). Post-harvest deterioration in some promising varieties. Bharatiya Sugar. July 1990. pp. 35-38.

Chiranjivi Rao, K. (1989). Recent advances in pre and post- harvest technology of sugarcane. Bhartiya Sugar, Aug., 9-12.

Egan, B.T. (1968). Post-harvest deterioration losses in sugarcane in Queensland, Proc. Int. Soc. Sugarcane Technol.. 13 : 32.

Solomon, S. (2000). Post-harvest cane deterioration and its milling consequences. Sugar Tech, 2 : 1-18.

Solomon, S. (2002). Post-harvest losses and their management. Indian Farming, 51(11) : 52-56.

Solomon, S., Shahi, It.N., Singh, I. and Madan, V.K. (1999). Dynamics of post-harvest sucrose losses in sugarcane during late-crushing period. Proc. Annu. Cony. STAI, 61 : 157-165.

Solomon, S., Shahi, H.N., Suman, A., Gaur, A., Deb, S. and Singh, I. (2001). A survey of post-harvest biological losses in Indian sugar factories: An emerging challenge. Proc. Int. Soc. Sugar Cane Technol., 24 : 380-381.

Solomon, S., Shrivastava, A.K., Srivastava, B.L. and Madan V.K. (1997). Pre-milling sugar losses and their management in sugarcane. Technical Bull. No. 37, IISR, LUCKNOW. Pp 1-217.

Solomon, S., Srivastava, K.K., Bhatnagar, S. and Madan, V.K. ~1990). Post harvest changes in invertase activity and juice quality in sugarcane~ Indian Sugar, 39(12) : 895-899.

Solomon, S., Ramaduri, R., Shanmugnathan, S., Shrivastava, A.K., Deb, S. and Singh, I. (2003). Management of biological losses in milling tandem to improve sugar recovery. Sugar Tech., 5(3) : 137-142.

Uppal, S.K. and Sharma, S. (1999). Relative performance of sugarcane genotypes to post harvest inversions in subtropical region. Indian Sugar, 49(5) : 345-348.

Uppal, S.K., Sharma, S. and Sidhu, G.S. (2000). Response of sugarcane genotypes to post-harvest deterioration under natural field conditions exposed to sun vs. shade. Crop Research, 19(1) : 13-16.

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