SOME FACTORS AFFECTING JUICE QUALITY COMPONENTS OF SUGARCANE IN COLOMBIA ABSTRACT INTRODUCTION MATERIALS AND METHODS

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1 Plant Physiology SOME FACTORS AFFECTNG JUCE QUALTY COMPONENTS OF SUGARCANE N COLOMBA J. E. Larrahondo, S. J. Yang and F. Villegas The Sugarcane Research Centre of Colombia (Cenicana) Cali, Colombia Key words: Maturity, rainfall, starch, polysaccharides, colour ABSTRACT The effect of age, rainfall, water deficit and varietal differences on some chemical characteristics of sugarcane were studied in the Cauca Valley (Colombia). Differences in the maturity pattern, starch, soluble polysaccharides, colour impurities or colour precursors, ( particularly amino nitrogen and phenols, were found among varieties. High rainfall prior to harvest lowered sucrose concentration in cane and both natural and artificial water deficits resulted in significant increases in colour components and starch. NTRODUCTON The milling process and sugar recovery are affected by the qual~ty of the cane provided from the field. The variety, season, type of soil, cultural practices and ripening control are factors which may affect the quality of the cane. Differences in sugar recovery have been observed through the years in the Cauca Valley, Colombia, with low sucrose contents during the rainy seasons (usually March to May and October to December). Similar results have been reported by Shoji and Samuels9 in Puerto Rico, where apparently yield decline depended on temperature and rainfall dur~ng the harvest season. Starch from cane juice is known to reduce the filterability of the raw sugar. The roles of starch and soluble polysaccharides during the growth of sugarcane have been dis-- cussed by chen4 and lmrice and ~ ilbur~~. They state that starch content is mainly a varietal characteristic, but that irrigation and potash fertilization tend to reduce the starch content of some varieties. The h~ghest starch content occurs when cane matures, a time at which phosphate levels in the juice are also high. Colour is another determinant of the quality of raw sugar. The colourants are generally grouped in two categories: cane plant pigments and factory produced colourants. Colour precursors such as amino-nitrogen and phenols are important substances present in cane juice because they react during processing to form coloured compounds (Meade and Chen7). Aberneth~ and Aitken' reported that colour precursor levels were related to the variety tested and, therefore, that juice colourant contents could be modified by varietal selection and breeding. Water stress S also known to increase the content of colour bodies, as reported by Lionnet6. He noted that the increase in amino-nitrogen is particularly pronounced and could result in serious problems during processing, since aminonitrogen is linked to Maillard type reactions. This information suggests that it would be important to study the effects of rainfall, cane variety and age-of harvest on cane quality in Colombia. MATERALS AND METHODS The present study was conducted in two stages. n the first, four promising varieties, CP72-370, CP72-356, PR and PR 1141 and two commercial varieties, MZC 74275

2 PLANT PHYSOLOGY and Mex 5229, were planted in small plots (6m X 10m) on a clay-loam soil of the Manuelita series (Mollisol) at the Cenicana Experiment Station. Each variety was planted every two months from March 1985 until January The cane quality of the plant-and first ratoon crops was evaluated at ages of 10, 12, 14, 16, 18 and 20 months. The sampling of the plant crop started in January 1986 and concluded in November The first ratoon sampling took place between October 1987 and Novemb.er Three samples of five stalks per variety at each age of harvest were taken at random from the' field and analyzed in the laboratory, following standard methods (SASTA8). Colour, turbidity and reducing sugar, starch, phosphorus and potassium contents of the juice were determinated. Determinations of amino-nitrogen, total phenols and total soluble polysaccharides in the juice were included for the first ratoon. The Folin-Ciocalteu method for phenols, the ninhydrin method for amino-nitrogen and the SPRl test for estimation of total soluble polysaccharides were used following proceduresdescribed by Clarke et ap and Clarke et UP. All varieties were fertilized after planting, using the equivalent of 100 kg N/ha. Rainfall was recorded on a daily basis. Additional information was collected for variety PR plan'ted in lysimeters under the following moisture regimes: loo%, 80%, 50% and 20% Gf total a;istilable soil moisture. The soil used for the trial was a clay-loam of the Palmeras series,,jlnpeptisol). RESULTS AND DSCUSSON The relationships between age and the apparent purity and estimated recoverable sugar for the six varieties CP72-370, CP72-356, MZC74275, Mex 5529, PR dnd PR 1141 are presented in Fig 1. The results demonstrate that CP72-370, CP and MZC mature in months. These varieties exhibited juice purity above 84% and estimated recoverable sugar (ers) % cane above 10.5%. n the.cauca Valley the variety Mex 5229 has been considered an early maturity variety. However, Mex 5229, PR and PR 1141 all matured late (16-20 months) in this trial. The ers % cane values for Mex 5229, PR and PR 1141 were 8.2, 6.4 and 8.2 respectively at 10 months of age. The maximum ers and purity observed for these varieties occurred at 18 months of age. Significant differences in starch content were observed at different crop ages (Fig 2) and different months of cutting for first ratoon crops of the varieties tested (Table 1). The highest starch content was found in the plant crop when the cane was mature, and a positive relation was observed between starch and phosphate contents, similar to the observations of Chen4 in Taiwan. The two CP varieties had the highest starch content. According to lmrice and Tilbury5 such high levels could be difficult to process in factories. Total phenols and amino-nitrogen compounds tended to increase as the cane age increased up to months in all varieties (Fig 3). CP exhibited the highest contents of phenols and amino-nitrogen, which could produce high levels of colour compounds during the processing of this variety. A high coefficient of determination (r2 = 0.86) between iuice colour and phenol concentration was observed in this trial The influence of rainfall on the quality. of. plant and first ratoon crops of the varieties tested is shown in Tables 1 and 2. The highest sucrose content was associpted with months of low rainfall prior to harvest. For the plant crop, the ers % cane was low during the period from May to July (1986) as a possible consequence of the high rainfall in April. Low rainfall between March and April (1988) was associated with better yields of sucrose from the first ratoon crops. Rainfall had a definite influence on the incidence of starch, soluble polysaccharides,

3 J.E. LARRAHONDO, S.J. YANG AND F. VLLEGAS *-. CP72370 x----x CP72356, MZC mlta. a. 1aoL Figure 1. Changes with age in estimated recoverable sugar (ers) and juice apparent purity for six sugarcane varieties phenols and amino-nitrogens (Table 1). These compounds increased after a dry period. Considering March-April (1988) as a dry period (15.2 mm) and November-December (1988) as a wet period (140 mm), high rainfall was associated with a large (almost 50%) reduction in the contents of starch and amino-nitrogen compounds in these varieties. The average decline in phenol and polysaccharide levels associated with high rainfal was 10% and 2496, respectively. These results suggest that, when the crops were suffering from water stress, the carbohydrates and amino acids produced by the plant were translocated to the storage tissues in the stalk because they were not required for stalk elongation and growth. The phosp.horus and potassium concentrations in juice increased after a wet month (Table 1). This may have been due to the release of potassium and phosphorus to the soil solution when the soil was wet, making the elements easy to remove by the plant. n view of the marked influence of rainfall on the amounts of colour bodies in cane, some observations were made on the variety PR planted under four soil mpisture regimes in large percolation type lysimeters. The cane was harvested at 14 mo@$;of, age and the results are shown in Table 3. These results partially confirm the data ;'h$"i$ ously presented. The increase in amino-nitrogen was pronounced in the stressed ca& (20% available soil moisturefreatment), the concentration being 4.8 times higher than that observed in the cane growing in the 100% available soil moisture treatment. The. coefficients of determination (r2) between the available soil moisture, and amino-

4 Table 1 - Changes in the chemical composition of the juice of the first ratoon crops of six varieties at different times of the year Amino- Starch Polysaccharides Phenols2/ K P nitrogen3/ (mg/l) (mdml) (md) (% brix) (mg/l) (mg/l) Variety1/ Apr Oct Dec Apr Oct Dec Apr Oct Dec Apr Oct Dec Apr Oct Dec Apr Oct Dec CP CP MZC Mex PR PR Average Rainfall (mm) / Harvested during 1988 from 10 to 20 months of age 2/ Mean caffeic acid equivalent 3/ Mean glutamic acid equivalent

5 J.E. LARRAHONDO, S.J. YANG AND F. VlLLEGAS., Age (months ) Figure 2. Starch and phosphate contents of cane juice of six varieties when 10 to 20 months old Table 2 - Average estimated recoverable sugar (ers) of the plant and ratoon crops of six varieties harvested at ages ranging from 10 to 20 months at different times of the year Variety CP CP MZC Mex 5229 PR PR 1141 Ers % cane First Ratoon2/ Average Rainfall3/ / Harvested during / Harvested during / Accumulated monthly rainfall prior to harvest in mm

6 PLANT PHYSOLOGY - 9 g eoo- - - V) n A-.-A MZC x-.-. Mex 5229 X---x PR A-.-A PR 1141 A ' Figure 3. Total phenols and amino-nitrogen contents of cane iuice of six varieties when 10 to 20 months old Table 3 - Effects of soil moisture availability on the juice quality of PR harvested at 14 months of age Available soil moisture (% Colour (CUMSA 420 nm) Turbidity (Abs)'/ P (mg/l) Amino nitrogen2/ (ms/l) Total phenols3/ (ms/l) l/ Optical absorbance at 720 nm 2/ Equivalent in glutamic acid 3/ Equivalent in caffeic acid

7 CONCLUSONS J.E. LARRAHONDO, S.J. YANG AND F VLLEGAS nitrogens and phenols, were 0.74 and 0.96 respectively. The colour and turbidity of the clarified juice also decreased as soil moisture increased. This result was associated with a greater concentration of phosphorus in the juice, probably due to a higher availability of phosphorus in the wet soil. These data suggest that water stress may increase the level of colour impurities and colour precursors and reduce the concentration of phosphorus, an important factor for good juice clarification. The present study shows that under the climatic conditions of the Cauca Valley the sugarcane varieties CP72-370, CP and MZC are early maturing varieties, and PR and PR 1141 are late maturing. The juices of CP and CP were high in starch and soluble polysaccharides in plant and first ratoon crops. The juice of the CP had the highest quantity of colour impurities, particularly amino-nitrogen and phenols. The concentration of colour precursors and plant pigments (phenols) varied with the age of the cane in all varieties. Accumulated rainfall from 1 or 2 months prior to harvest was associated with lower sucrose contents in cane of all varieties. PR 1141 and CP appeared more sensitive to rainfall than the other varieties. The concentration of total phenols and amino-nitrogen compounds in the juice increased during the warm season and decreased during the rainy season. Water stress resulted in significant increases in the content of colour bodies. The increase in amino-nitrogen was particularly pronounced and could result in serious sugar colour problems during processing. REFERENCES Abernethy, PE and Aitken, AT (1986). Factors affecting the levels of colour entering a sugar mill. Proc Aust Soc Sug Cane Technol 1986: Clarke, MA, Blanco, RS and Godshall, MA (1986). Colorants in raw sugars. Proc int Soc Sug Cane Technol 2: Clarke, MA, Roberts, EJ and Godshall, MA (1986). Non-starch, soluble polysaccharides of sugarcane. Proc S Afr Sug Technol Ass 60: Chen, W (1968). A study of the role of starch in the growth of sugarcane and the manufacturing of cane sugar. Proc int Soc Sug Cane Technol 13: mrice, FKE and Tilbury, RH (1972). Polysaccharides in sugar cane and its products. Sug Technol Rev 1: Lionnet, GRE (1986). An le analytical approach for the determination of colour and other impurities in cane. Proc S Afr Sug Technol Ass 60: Meade, GP and Chen, JCP (1977). Cane Sugar Handbook (10ed) Wiley-lnterscience Publication, John Wiley and Sons, New York. 947 p. 8. South African Sugar Technologists' Association (1977). Laboratory Manual for South African Sugar Factories (2ed). S Afr Sug Technol Ass. Durban, South Africa. 9. Shoji, K and Samuels, G (1967). A study of declining sucrose yields in Puerfo Rico. Proc, int Soc Sug Cane Technol 12:

8 LES CARACT$RES CHlMlQUES ET DE MATURATON DE LA CANNE A SUCRE EN COLQMBE J.E. Larrahondo, S.J. Yang et F. Villegas The Sugar Cane Research Centre of Colombia (Cenicatia) Cali, Colombia EXTRAT PLANT PHYSOLOGY L'effet de 1'6ge, de la pluviosite, du deficit hydrique et des differences varietales sur les caracteres ch~rniques de la canne a sucre furent etudies dans la vallee de "Cauca" (Colornbre). Des differences furent trouvees entre les varietes par rapport a leur rnaturrte durant 'annee, la teneur en arnidon, en polysaccharides solubles, en irnpuretes ou pre-, curseurs de couleur speclalernent 'azote arnine, et en phenols. La pluviositi. abondante avant la recolte entraina une faible teneur en saccharose dans la canne tandis qu'un deficlt hydrique causa des augmentations irnportantes de rnatieres colorantes et d'amidon. Mots cles: Analyse de canne, Amidon, polysaccharides, precurseur, de couleur; azote amine, produits phenoliques. CARACTERSTCAS QUlMlCAS Y DE MADURACON DE VARJEDADES BE CANA BE AZUCAR EN COLOMBA 1 J.E. Larrahondo, S. J. Yang y F. Villegas Centro de lnvestigacion de la catia de azircar (Cenicatia) Cali, Colombia RESUMEN Se estudiaron en el Valle del Cauca (Colombia) 10s efectos de la edad, precipitacibn, deficiencia de agua y diferencias varietales en la composici6n y caracteristicas quimicas de la catia de azocar. Se encontraron en este estudio deferencias en la maduraci6n y en 10s contenidos de almidones, polisclcaridos solubles y de precursores de color, especialmente de fenoles y cornpuestos amino-nitrogenados. La precipitacibn mensual acurnulada antes del corte caus6 descensos en la concentraci6n de sacarosa y el deficit de h~~medad produio incrementos significativos en 10s contenidos de alrnido-