Assessment of Variables Effects on Sugar Cane Juice Clarification

Original article

Assessment of variables effects on sugar cane juice clarification

by carbonation process

Fabiane Hamerski,* Vıtor R. da Silva, Marcos L. Corazza, Papa M. Ndiaye & Arislete D. de Aquino

Graduate Program in Food Engineering, Department of Chemical Engineering, Federal University of Parana, PO Box 19011, 81531980 Curitiba,

Parana, Brazil

(Received 21 May 2011; Accepted in revised form 24 September 2011)

Summary This paper reports a study of sugar cane juice carbonation and the evaluation of variables effects such as

pH, carbonation time and temperature on industrially relevant parameters for the quality of sugar cane

juice. Three different batches of sugar cane juice were evaluated using a complete two-level factorial

design with central point performed in triplicate. From results in this work, it can be seen that the higher

sucrose concentrations and lower percentage of total soluble solids and reducing sugars were obtained in

clarified juices with the maximum values for pH, time and reaction temperature (9.5, 60 min and 80 �C).The temperature favoured the removal of starch, phosphate and turbidity. Colour removal reached a

maximum of 88–93% among the batches. The optimum clarification condition using carbonation

procedure can be achieved between 20 and 40 min, at pH values between 8.0 and 9.5 and temperature

condition at 80 �C.

Keywords Carbonation, clarification, sugar cane juice.

Introduction

The clarification of sugar cane juice is an important processin the sugar production because the success of the clarifi-cation is directly related to the performance of subsequentproduction processes and the quality of the sugar. In theclarification process, nonsugar components (proteins, poly-saccharides, gums, minerals and dyes) should be totallyremovedwithout sucrose degradation or colour production(Al-Farsi, 2003; Bourzutschky, 2005a).In the sugar industry, the clarification of sugar cane

juice is traditionally performed by the sulphitationmethod. This process consists of the addition of gaseoussulphur dioxide (SO2) into the juice until the pHcondition 3.8–4.2 is reached. Subsequently, neutralisa-tion (pH 7.0–7.2) is achieved by the addition of hydratedlime (Ca(OH)2). The alkalinisation of the sulphite juiceleads to the formation of calcium sulphite, whichprecipitates and adsorbs undesirable compounds fromthe juice. Then, the juice is heated to 100–105 �C andsent through sedimenters to remove the precipitates(Honig, 1953; Chen & Chou, 1993).Some problems have been restricted the use of the

sulphitation method, particularly those regarding foodsafety standards, which generally require lower residuallevels of sulphur-based compounds in food (Bour-zutschky, 2005b; Steindl & Doherty, 2005). Addition-

ally, sucrose is lost in the process by inversion, owing tothe low pH and low solubility of SO2 in sugar cane juice(Chou et al., 2006). Moreover, the industrial use of SO2

leads to environmental problems, such as acid rain, anuncomfortable workplace environment in factories andmetal corrosion in industrial installations.Thus, carbonation can be a viable option because it

replaces the use of sulphur and can be used for thesequestration of CO2 excess, which is freely available inthe sugar and alcohol industries (Saska et al., 2010). Thecarbonation process is commonly used in the refinementof raw sugar and the purification of beet juice; it is rarelyused in the clarification of sugar cane juice. This processconsists from hydrated lime and carbon dioxide (CO2)addition into sugar cane juice under controlled condi-tions, which form a crystalline calcium carbonateprecipitate. This precipitate adsorbs and incorporatesthe colloidal and insoluble matter, inorganic compoundsand dye substances. Subsequently, the precipitates canbe removed from the clarified juice by filtration (Honig,1953; Chen & Chou, 1993; Moodley et al., 2003).The main subject of this work was to assess the

clarification of sugar cane juice by carbonation andevaluate the effect of pH, time and temperaturecarbonation on concentrations of total soluble solids,reducing sugars (RS), sucrose, total hardness, conduc-tivity ashes and starch, colour, inorganic phosphate andturbidity removal, which can be considered mostimportant parameters in the clarified sugar cane juice.*Correspondent: E-mail: [email protected]

International Journal of Food Science and Technology 2012, 47, 422–428422

doi:10.1111/j.1365-2621.2011.02857.x

� 2011 The Authors. International Journal of Food Science and Technology � 2011 Institute of Food Science and Technology

Materials and methods

Materials

In this study, three batches of sugar cane juice extractedin small mills from dirty sugar cane of different originswere used. The juices were characterised and stored inplastic containers at )10 �C prior to the beginning of theexperiment.Carbon dioxide of 99.995% purity was used (WHITE

MARTINS). Hydrated lime (calcium hydroxide,Ca(OH)2) was prepared from the solubilisation of4.43% (w ⁄v) calcium oxide (CaO; 95% purity; VETEC,Rio de Janeiro, Brazil) in distilled water, resulting in asolution with an apparent density of 1.036. An anionicpolymer, MAGNAFLOC LT27, was used to aidprecipitation.

Methods

Carbonation testsThe experiments were carried out in the apparatusschematically as shown in Fig. 1. Initially, 500 g ofsugar cane juice was heated at different temperatureslisted in Table 1. The temperature was kept constantthroughout the process using a thermostatic bath(TECNAL TE-184, Sao Paulo, Brazil). Ca(OH)2 wasadded to the juice making the pH constant, in accor-dance with the desirable experiment condition. Then,gaseous CO2 was bubbled into the juice, through a gasdisperser in the reactor bottom, at a constant flow rateof 2 L min)1 and an average pressure of 850 psi. Thehydrated lime was added to the juice to keep the pHconstant throughout the process. A digital pHmeter(MICRONAL, B-474, Sao Paulo, Brazil) coupled to thesystem was used to monitor the pH during the exper-iment. After the reaction, 1 mL of polyelectrolyte wasadded to the carbonated juice. The mixture wasallocated at room temperature for 60 min for sedimen-tation of the precipitates formed. Then, the physico-chemical analyses, RS, sucrose, starch, conductivity

ashes, International Commission for Uniform Methodsof Sugar Analysis (ICUMSA) colour, total hardness,inorganic phosphate and total soluble solids wereperformed in the clarified juice.

Experimental designA complete factorial (23) experimental design withtriplicate central point was used to study the effects ofpH, time and temperature on the carbonation of threebatches of sugar cane juice. Table 1 shows the associa-tion between the levels ()1 and +1) of the variables thatdefined the experiments (Calado & Montgomery, 2003).Variables levels pH, time and temperature were definedin the preliminary tests. The lower level ()1) of thevariable pH was fixed 6.5, because with pH lower than 6,little precipitate was formed and sugar cane juiceclarification was insufficient (Hamerski et al., 2011).However, the maximum level (+1) was pH 9.5, at pH>9.5 an excessive amount of lime was necessary tomaintain pH constant. Reaction times studied, corre-spond to a minimum of 20 min and maximum of 60 min.The effect of temperature in the carbonation reactionwas evaluated at 40 �C and 80 �C, minimum ()1) andmaximum (+1), respectively. A triplicate central pointdefined by intermediate conditions of each variable wasconducted to evaluate the repeatability of experiments.

Statistical analysisThe experimental data obtained were statistically anal-ysed (anova) by the F test, and the averages werecompared by Tukey’s test using a 5% significance level(P < 0.05). The software statistica 7.0 (Stat-Soft,Tulsa, OK, USA) was used.

Analytical determinationsPhysical and chemical analyses were performed intriplicate and the results are expressed on total solublesolids percentage. The methods used for the analyses ofacidity, starch, conductivity ashes, ICUMSA colour,total hardness, inorganic phosphate, total soluble solids

V-1V-2

1 2 7

45

36

Figure 1 Scheme of the carbonation laboratory system: 1-CO2;

2-Thermostatic bath; 3-Reactor; 4-Gas disperser; 5-Combined electrode

for pH measure; 6-Temperature probe (PT 100); 7-pH meter; V-1-

Valve with flow and pressure indicator (SR 312); V-2-Needle valve.

Table 1 Experimental conditions of the complete factorial design (23)

Treatments pH Time (min) Temperature (�C)

1 6.5 20 40

2 9.5 20 40

3 6.5 60 40

4 9.5 60 40

5 6.5 20 80

6 9.5 20 80

7 6.5 60 80

8 9.5 60 80

9a 8.0 40 60

10a 8.0 40 60

11a 8.0 40 60

aCentral point.

Sugar cane juice clarification by carbonation F. Hamerski et al. 423

� 2011 The Authors International Journal of Food Science and Technology 2012

International Journal of Food Science and Technology � 2011 Institute of Food Science and Technology

and pH in the sugar cane juice are described in Copersu-car (2001) and are based on the methods recommendedby the ICUMSA. The levels of RS and sucrose weredetermined by the colorimetric method described byMiller (1959). To determine the sucrose concentration,we quantified the concentration of total reducing sugars(TRS) from the acid hydrolysis of sugar cane juice. Thesucrose concentration was obtained by the differencebetween the TRS and RS values multiplied by 0.95(conversion factor of glucose to sucrose) (Instituto

Adolfo Lutz, 2008). The turbidity was determined in abench turbidimeter microprocessor (DEL LAB DLM-2000B, Sao Paulo, Brazil).

Results and discussion

Raw juice characteristics

The three batches of sugar cane juice showed significantdifferences in the physical and chemical characteristicsof the raw juices according to anova analysis (Table 2).As pointed out in the literature this result was expectedbecause the juice composition is influenced by severalfactors, including the sugar cane variety, geographicallocation, climatic conditions and juice extractionmethod (Kampen, 1997; Marques et al., 2001; Doherty& Rackemann, 2009).

Total soluble solids, reducing sugars and sucrose

Table 3 presents the mean values and standard devi-ations for total soluble solids (TSS) concentration, RSand sucrose of clarified juices under different carbon-ation conditions.From results presented in Table 3 it can be seen that

the total soluble solids concentration presented lowervalues in clarified juices than in the respective rawjuices. This is owing to the removal of solublecomponents and the dilution of the juice usinghydrated lime. However, in Treatments 5 and 7, whichwere performed at higher temperature (80 �C) andlower pH (6.5), the effect of the juice concentration wasmore observed in comparison with the effects of TSSremoval and dilution. This suggests that there was lessTSS removal and dilution of the juice due to the lowCO2 adsorption at pH 6.5 and a lower consumption of

Table 2 Characteristics of the raw sugar cane juices

Parameters Batch 1 Batch 2 Batch 3

pH 5.52 ± 0.02b 5.56 ± 0.02b 5.69 ± 0.02a

Acetic acid

(% mg g)1)

122.91 ± 3.61a 79.16 ± 3.61b 66.66 ± 3.61c

Total soluble

solids (�Brix)

17.20 ± 0.02c 19.20 ± 0.02b 21.00 ± 0.02a

Reducing sugars

(g (100 g TSS))1)

5.54 ± 0.21a 2.53 ± 0.06c 3.18 ± 0.03b

Sucrose

(g (100 g TSS))1)

83.04 ± 0.74a 83.87 ± 0.64a 79.20 ± 0.19b

Starch

(mg (100 g TSS))1)

162.92 ± 0.41c 279.57 ± 0.03b 355.66 ± 0.83a

Phosphate

(mg (100 g TSS))1)

430.94 ± 3.47a 257.43 ± 1.54b 110.31 ± 0.01c

Ash (g

(100 g TSS))1)

2.14 ± 0.01a 0.75 ± 0.00b 0.75 ± 0.00b

Colour (IU) 31.367 ± 0.01b 47.233 ± 0.02a 48.333 ± 0.01a

Hardness (mg CaO

(100 g TSS))1)

197.15 ± 0.04c 235.72 ± 0.24b 242.60 ± 0.38a

Turbidity (NTU) 86.00 ± 0.50c 92.40 ± 0.53b 330.00 ± 2.00a

IU, ICUMSA units; NTU, nephelometric turbidimeter units; TSS, total

soluble solids.

Different letters in the same row represent statistically different means

according to the Tukey’s test (P < 0.05).

Table 3 TSS, RS and sucrose concentrations in clarified sugar cane juices

Treatments†

Batch 1 Batch 2 Batch 3

TSS RS Sucrose TSS RS Sucrose TSS RS Sucrose

1 (6.5-20-40) 17.00 ± 0.02b 4.92 ± 0.07c 86.19 ± 0.57a 18.80 ± 0.02c 2.09 ± 0.01a 84.04 ± 0.13c 20.40 ± 0.02c 2.61 ± 0.01ab 79.50 ± 0.66de

2 (9.5-20-40) 14.40 ± 0.02d 4.64 ± 0.03d 85.65 ± 0.81ab 16.60 ± 0.02e 1.63 ± 0.01d 84.69 ± 0.29bc 18.60 ± 0.02e 2.36 ± 0.01c 79.35 ± 0.20e

3 (6.5-60-40) 16.60 ± 0.02c 5.20 ± 0.01b 86.36 ± 0.49a 19.00 ± 0.02c 1.91 ± 0.02b 84.72 ± 0.32bc 20.60 ± 0.02c 2.38 ± 0.00c 82.06 ± 0.02ab

4 (9.5-60-40) 10.60 ± 0.02h 4.79 ± 0.06cd 85.73 ± 0.62ab 14.00 ± 0.02g 1.43 ± 0.01e 84.36 ± 0.63bc 16.00 ± 0.02h 2.33 ± 0.03c 80.77 ± 0.87bcde

5 (6.5-20-80) 18.50 ± 0.02a 4.91 ± 0.01c 83.46 ± 0.93b 21.20 ± 0.02b 2.04 ± 0.02a 85.82 ± 0.06b 23.60 ± 0.02b 2.63 ± 0.02a 80.30 ± 0.21cde

6 (9.5-20-80) 13.60 ± 0.02e 3.50 ± 0.06e 85.45 ± 0.29ab 18.00 ± 0.02d 1.76 ± 0.03c 81.99 ± 0.21d 19.80 ± 0.02d 2.05 ± 0.01e 81.13 ± 0.08abc

7 (6.5-60-80) 18.60 ± 0.02a 5.57 ± 0.07a 85.61 ± 0.08ab 23.20 ± 0.02a 1.93 ± 0.03b 84.95 ± 1.58bc 24.30 ± 0.02a 2.53 ± 0.04b 80.92 ± 0.11bcd

8 (9.5-60-80) 10.80 ± 0.02h 3.11 ± 0.09f 85.72 ± 1.13ab 12.40 ± 0.02h 1.04 ± 0.02f 88.87 ± 0.07a 17.60 ± 0.02f 1.47 ± 0.01f 82.44 ± 0.92a

9 (8.0-40-60) 12.60 ± 0.02g 4.62 ± 0.07d 83.62 ± 1.43b 16.20 ± 0.02f 1.62 ± 0.03d 84.80 ± 0.42bc 17.00 ± 0.02g 2.20 ± 0.05d 80.29 ± 0.45cde

10 (8.0-40-60) 13.00 ± 0.02f 4.67 ± 0.06d 84.61 ± 0.94ab 16.00 ± 0.02f 1.48 ± 0.02e 84.37 ± 0.27bc 17.00 ± 0.02g 2.38 ± 0.04c 80.02 ± 0.64cde

11 (8.0-40-60) 13.00 ± 0.02f 4.69 ± 0.07d 83.82 ± 0.19b 16.40 ± 0.02ef 1.46 ± 0.02e 84.82 ± 0.57bc 17.20 ± 0.02g 2.33 ± 0.05c 80.35 ± 0.39cde

TSS, total soluble solids.

Different letters in the same column represent statistically different means according to the Tukey’s test (P < 0.05).†Experimental conditions: pH, time (min) and temperature (�C). TSS (�Brix); RS and Sucrose (g (100 g TSS))1).

Sugar cane juice clarification by carbonation F. Hamerski et al.424

International Journal of Food Science and Technology 2012 � 2011 The Authors


hydrated lime, this can also be seen in Table 4 from dequantity of lime used in the treatments. The reactions atmaximum pH, temperature and time consumed greateramount of lime in all batches studied. It can beexplained because the CO2 addition into a highlyalkaline medium demanding greater amount of lime tomaintain the pH reaction at a constant value.The results of this study revealed that the RS concen-

tration decreased in the clarified juices, which is similar tothe results obtained by Aoki (1987) and Moodley et al.(2003) in their study of sugar cane juice carbonation.These components need attention because they can beconverted into colourless compounds (organic acids) orgenerate products that can polymerise (Maillard reac-tion) and form coloured compounds of high molecularmass, which are detrimental to the quality of sugar(Eggleston & Vercellotti, 2000; Bourzutschky, 2005b).We found that higher pH values, longer reaction times

and higher temperatures of carbonation (Treatment 8) ledto lower percentages of RS in clarified juices for the threebatches evaluated in this work (Table 3). Although thehighest level of RS was observed in different treatmentconditions among the batches, all of the treatments were atpH 6.5. This trend is owing to the degradation of mono-saccharides, which is favoured under high temperature andalkaline conditions (Eggleston & Vercellotti, 2000; Farineet al., 2000). Moreover, Coca et al. (2004) have reportedthat the presence of divalent cations, such as calcium andmagnesium, accelerate the decomposition of monosaccha-rides, which emphasises the importance of the carbonationpH for this variable; these results indicate that higher pHvalues require greater additions of lime to the medium.It is noteworthy that sucrose losses were not detected,

because the sucrose concentrations in the clarified juiceswere higher than those in the raw juices. This is owing tothe removal of impurities from the juice and reduction inthe RS percentage. Higher percentages of sucroseindicate that the clarified juice had higher purity. Inbatches 2 and 3, the highest pH, longest reaction time

and highest temperature conditions produced the high-est levels of sucrose; however, in batch 1, the percentagesof sucrose were very similar among all treatments.

Starch and phosphate removal

Figure 2 shows the percentage of the starch removed.The minimum values varied among the batches fromapproximately 66% to 72% and corresponded totreatments with the lowest temperature in this study(40 �C). On the other hand, the maximum percentagesof removal of approximately 99% were reached indifferent treatments of each batch with higher temper-atures (60 or 80 �C).It was observed that temperature had a significant

effect on the removal of starch, where higher tempera-tures lead to higher percentages of starch removal,which were almost independent of the pH and time ofcarbonation. According to Eggleston et al. (2002),heating of the juice allows the starch to gelatinise, andthe gelatinised starch is incorporated into the flakes ofcalcium carbonate along with denatured proteins. Thesecompounds should preferentially be precipitated andtotally removed from the juice because the presence ofstarch in the clarified juice slows crystallisation incookers and decreases the filtration rates at refineries.The maximum percentages of phosphate removal,

shown in Fig. 3, corresponded to the highest tempera-ture treatments (80 �C) and varied from 80% to 93%among the batches. On the other hand, the lowestpercentages of phosphate (63 at 74%) were removed inthe treatments with the lowest temperature (40 �C) andpH (6.5). Among all of the batches, the lowest percent-ages of phosphate removal were obtained in batch 3because the concentration of phosphate in the raw juicewas also the lowest among the batches. According toJourani et al. (1995), the precipitation of phosphate

Table 4 Quantity of lime used in the treatments (L (100 kg juice))1)

Treatments† Batch 1 Batch 2 Batch 3

1 (6.5-20-40) 3.80 2.80 2.40

2 (9.5-20-40) 19.60 11.80 12.80

3 (6.5-60-40) 4.60 2.80 2.40

4 (9.5-60-40) 43.40 33.40 29.80

5 (6.5-20-80) 2.20 2.00 1.40

6 (9.5-20-80) 35.60 20.00 19.80

7 (6.5-60-80) 4.20 2.00 1.80

8 (9.5-60-80) 80.20 76.00 62.20

9 (8.0-40-60) 36.20 23.00 26.60

10 (8.0-40-60) 39.00 21.20 28.00

11 (8.0-40-60) 38.20 21.40 24.20

†Experimental conditions: pH, time (min) and temperature (�C).

100

90

Batches:1 2 3

80

70

60

500 1 2 3 4 5 6 7

Treatments

Star

ch (

% r

emov

ed)

8 9 10 11 12

Figure 2 Starch removal.




depends on its initial concentration, and low initialpercentages lead to less precipitation.We observed that temperature had a greater effect on

the removal of phosphate and may be related to itsprecipitation mechanism. According to Grenwood et al.(2007), the removal of phosphate occurs by precipitationin the form of hydroxyapatite, Ca5(PO4)3OH. However,during spontaneous precipitation, an amorphous calciumphosphate is formed first, which turns into hydroxyapatitethrough an autocatalytic mechanism. Higher tempera-tures favour this conversion by increasing the solubility ofamorphous calcium phosphate, which accelerates theconversion into hydroxyapatite and phosphate removal.

Colour removal

The colour removal is one of the most importantparameters in the clarification of sugar cane juice andaffects both the process control and the quality and priceof sugar. According to the data presented in Fig. 4, inbatches 2 and 3, the highest percentages of colourremoval (91–93%) were obtained in treatments withhigher pH and temperature levels and shorter reactiontimes. The treatments with the lowest levels of thesevariables removed the lowest percentages of colour.However, in the juice of batch 1, carbonation removedthe maximum andminimum percentages (88% and 63%,respectively) of colour with the intermediate and max-imum levels, respectively, of carbonation conditions.Higher alkaline conditions (pH 9.5) associated with the

highest temperature (80 �C) favoured the removal ofcolour and depended on the reaction time and theconcentration of RS in the raw juice. When the juice wasreacted in these conditions for a long period, thedegradation of RS was favoured, which creates colouredcompounds. Consequently, a lower percentage ofcoloured compounds was removed. Treatment 8 in thefirst batch, which had the worst performance for the

removal of colour, exemplifies this phenomenon. Becausethis batch of raw sugar cane juice had a higherconcentration of RS, carbonation induced greater degra-dation and formation of coloured compounds and,consequently, removed a lower percentage of colourcompared with the different batches. However, in batches2 and 3, which had lower concentrations of RS in the rawjuice, this treatment had the two highest percentages ofcolour removal, which highlights the importance of thecharacteristics of the raw juice for process performance.

Turbidity removal

Turbidity is one of the main parameters used to assessthe performance of the clarification process because it isrelated to the presence of nonsugars and suspendedmaterials (gums, starch and proteins) in the juice. Theremoval of turbidity is indicative of the removal of thesecomponents (Eggleston, 2000).The data on the turbidity removal, presented in

Fig. 5, indicated that carbonation is effective for theremoval of suspended materials, given that the mini-mum reduction in the turbidity indices varied among thebatches from 90% to 95%. Among the three batches,the maximum turbidity removal was 99%. Moodleyet al. (2003) also obtained excellent turbidity removalpercentages (95%), confirming that the clarificationprocess of sugar cane juice by carbonation has greatpotential. We observed that treatments with the maxi-mum temperature (80 �C) removed the highest percent-ages of turbidity and that the pH and reaction time hadlittle effect on this variable.

Hardness and ashes

The data on total hardness, expressed in terms of thecalcium oxide (CaO) concentration (Table 5), revealed

100

90

Batches:1 2 3

80

70

60

500 1 2 3 4 5 6 7

Treatments

Phos

phat

e (%

rem

oved

)

8 9 10 11 12

Figure 3 Phosphate removal.

100

90

Batches:1 2 3

80

70

60

500 1 2 3 4 5 6 7

Treatments

Col

our

(% r

emov

ed)

8 9 10 11 12

Figure 4 Colour removal.




that the association between the pH and temperaturealso influenced the level of hardness. Among the threebatches, the lowest total hardness levels were observedin clarified juices at pH 9.5 and a temperature of80 �C. The highest values were obtained at pH 6.5,with a temperature of 40 �C and a reaction time of60 min.The hardness of the clarified juice is owing to the

presence of calcium ions, which mainly originate fromthe addition of lime. At basic pH values, the solubility ofCO2 is favoured, which releases carbonic acid to reactwith calcium hydroxide. A precipitate of calciumcarbonate is formed, which removes the hardness ofthe juice. At lower pH values, calcium ions becomeavailable in the juice owing to the low solubility of CO2

and contribute to higher levels of hardness.Low levels of hardness are preferred in the clarified

juice because high levels of hardness in the juice can lead

to build-up in the evaporators, which consequentlydecreases the capacity of heat transfer, increases thewear of the equipments and increases the requirementfor maintenance.In relation to the ash concentration (Table 5), treat-

ments with the intermediate levels of pH, time andtemperature (8.0, 40 min and 60 �C, respectively) led tothe lowest percentages of ash in the clarified juices, whilethe highest values among all batches were obtained inTreatment 3.We observed that clarification at pH 6.5 is not

recommended because the sugar cane juices producedat low pH contained the highest concentrations of ash,indicating that there was a low efficiency of salt removal.Eggleston (2000) stated that the presence of highconcentrations of ash in clarified juices has a negativeimpact on the quality and price of sugar because it is acharacteristic of lower purity and consequently a lowermarket value.The effects of the pH, time and temperature of

carbonation on the quality parameters of clarifiedsugar cane juice indicated that this clarification pro-cess could be effective between pH 8.0 and 9.5, areaction time of 20–40 min and at a minimumtemperature of 80 �C. Honig (1953) describes thatfor better performance of carbonation, the processshould be conducted at pH above 8 and highertemperature. At this pH levels, carbonation resulted inclarified juices with higher percentages of sucrose,lower concentrations of RS, lower values of hardnessand lower amounts of ashes. Moreover, the highesttemperature resulted in greater removal of starch,phosphate and turbidity without requiring the maxi-mum reaction time used in the study. The associationbetween these variables and these conditions alsofavoured the removal of colour and limited the

100

98

Batches:1 2 3

96

94

90

92

88

0 1 2 3 4 5 6 7Treatments

Tur

bidi

ty (

% r

emov

ed)

8 9 10 11 12

Figure 5 Turbidity removal.

Table 5 Hardness and ash in clarified sugar cane juice

Treatments†

Batch 1 Batch 2 Batch 3

Hardness Ash Hardness Ash Hardness Ash

1 (6.5-20-40) 532.71 ± 0.76b 2.55 ± 0.01b 572.14 ± 1.35b 1.33 ± 0.01b 609.60 ± 0.51b 1.40 ± 0.01b

2 (9.5-20-40) 117.80 ± 0.17g 2.17 ± 0.01e 238.63 ± 0.36e 0.79 ± 0.01f 182.34 ± 0.33e 0.80 ± 0.01g

3 (6.5-60-40) 681.21 ± 0.94a 2.59 ± 0.01a 685.26 ± 1.25a 1.51 ± 0.01a 631.96 ± 0.83a 1.60 ± 0.01a

4 (9.5-60-40) 106.70 ± 0.20h 2.12 ± 0.01f 121.13 ± 0.18f 0.66 ± 0.01h 35.43 ± 0.10i 0.67 ± 0.01i

5 (6.5-20-80) 399.99 ± 0.86d 2.53 ± 0.01c 347.19 ± 0.26d 1.13 ± 0.01c 431.97 ± 0.58d 1.12 ± 0.01d

6 (9.5-20-80) 83.24 ± 0.14i 2.31 ± 0.01d 31.41 ± 0.05j 0.75 ± 0.01g 57.23 ± 0.02h 0.94 ± 0.01e

7 (6.5-60-80) 487.05 ± 0.57c 2.53 ± 0.01c 366.12 ± 0.33c 1.00 ± 0.01d 468.01 ± 0.27c 1.16 ± 0.01c

8 (9.5-60-80) 52.43 ± 0.11j 2.02 ± 0.01h 45.70 ± 0.14i 0.88 ± 0.01e 32.23 ± 0.08j 0.86 ± 0.01f

9 (8.0-40-60) 134.71 ± 0.07e 2.09 ± 0.01g 69.90 ± 0.08hg 0.63 ± 0.01j 133.04 ± 0.24f 0.67 ± 0.01i

10 (8.0-40-60) 130.64 ± 0.24f 1.99 ± 0.01i 70.78 ± 0.16g 0.65 ± 0.01i 132.88 ± 0.06f 0.70 ± 0.01h

11 (8.0-40-60) 130.55 ± 0.27f 2.09 ± 0.00g 68.99 ± 0.15h 0.66 ± 0.01h 131.69 ± 0.12g 0.67 ± 0.01i

TSS, total soluble solids.

Different letters in the same column represent statistically different means according to the Tukey’s test (P < 0.05).†Experimental conditions: pH, time (min) and temperature (�C). Hardness (mg CaO (100 g TSS))1); Ash (g (100 g TSS))1).




formation of coloured compounds, owing to theshorter reaction time between the RS of the juiceand the alkaline medium. These effects depended onthe characteristics of the raw juice and were enhancedin juice with higher concentrations of RS. Thus, ourresults highlight the importance of the control ofprocess variables and evaluation of the raw materialand reveal the complexity of the control and stan-dardisation of sugar cane juice clarification.

Conclusions

From experimental results obtained in this work, it canbe seen that the clarification of sugar cane juice bycarbonation removed starch, phosphate, colour, turbid-ity and degraded RS. The maximum levels of pH (9.5),time (60 min) and temperature (80 �C) of carbonationresulted in clarified juices with higher percentages ofsucrose and lower concentrations of total soluble solids,RS, hardness and ashes. Higher temperatures increasedthe percentage of starch and turbidity removal. Car-bonation at 60 and 80 �C removed 99% of the starchand turbidity, regardless of the pH and reaction time.The maximum percentages of phosphate (80-93%) wereremoved in the carbonation experiments with theminimum pH (6.5) and maximum temperature (80 �C).Carbonation removed the maximum colour percentagesof 88–93%. The carbonation reaction at pH 9.5 with atemperature of 80 �C and for 20 min favoured theremoval of colour from raw juices with lower concen-trations of RS.The best results for the evaluated quality parameters

for the clarification of sugar cane juice by carbonationvaried in relation to the pH, time and temperature. Wefound that clarification by the carbonation reaction hadsome tendency to the best performance, highlighting thepH values between 8.0 and 9.5, reaction durationsbetween 20 and 40 min and a minimum temperature of80 �C.

Acknowledgments

We are thankful for financial support provided byFINEP ⁄SEBRAE and for a scholarship provided byCAPES and CNPQ.

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Documents

Assessment of Variables Effects on Sugar Cane Juice Clarification