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food and bioproducts processing 9 4 ( 2 0 1 5 ) 565–571

Contents lists available at ScienceDirect

Food and Bioproducts Processing

j ourna l ho me page: www.elsev ier .com/ locate / fbp

roduction and spouted bed drying of acerola juiceontaining oligosaccharides

ntônia Daiana A. Araújo, Raquel M.D. Coelho,láudia Patrícia M.L. Fontes, Ana Raquel A. Silva,

osé Maria Correia da Costa, Sueli Rodrigues ∗

niversidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Tecnologia de Alimentos,EP 60021970 Fortaleza, CE, Brazil

a b s t r a c t

In the present study, acerola (Malpighiae marginata) juice was used as substrate for oligosaccharides synthesis by

the dextransucrase acceptor reaction. Due to the low sugar content of acerola, external sugars (sucrose, glucose

and fructose) were added to the juice and the oligosaccharides synthesis was carried out using a central composite

rotated design. High oligosaccharide and low dextran yields were obtained indicating that the acceptor reaction had

occurred. The sugar conversion into oligosaccharides was also high (>60%) and oligosaccharides with a degree of

polymerization up to 12 were obtained. The prebiotic juice was dried in a spouted bed using maltodextrin as carrier.

The powder dried at 60 ◦C showed low hygroscopicity (7.90%), low moisture (1.91%) and low water activity (0.18).

© 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Keywords: Dextransucrase acceptor reaction; Prebiotic oligosaccharides; Acerola juice; Spouted bed; Fruit juices;

isomalto-oligosaccharides with a degree of polymerization

Functional foods

. Introduction

he human intestine is a complex ecosystem colonized byore than 500 hundred strains, which makes the human

ut the most active metabolic organ in the human body. Theut function might affect the body health in several ways.ecause of that, an intense attempt to control and under-tand the intestinal microorganisms has been undertakenately (García-Peris et al., 2012). Prebiotic oligosaccharidesre non-digestible food ingredients that positively affect theealthy due to the selective stimulation of beneficial bacteriarowth in the colon, contributing to the functional equilib-ium (Calderón et al., 2012; Fernando et al., 2011). The selectiverowth of lactobacillus and bifidobacterium promoted by therebiotic oligosaccharides results in intestinal acidificationue to the production of short chain fatty acids, which con-ributes to the calcium absorption. The intestinal transit islso improved and a decrease of pathogen counts has been

eported in response to the increased beneficial strain countsRoberfroid et al., 2010).

∗ Corresponding author. Tel.: +55 85 3366 9656; fax: +55 85 3366 9751.E-mail address: sueli@ufc.br (S. Rodrigues).

Available online 15 August 2014ttp://dx.doi.org/10.1016/j.fbp.2014.08.005960-3085/© 2014 The Institution of Chemical Engineers. Published by

Nowadays, dairy products are the main source of prebi-otic oligosaccharides in the food industry. However, someconsumers avoid dairy products due to milk allergy, lac-tose intolerance or vegetarianism. On the other hand, theconsumption of fruit juices has increasing due to their nutri-tional value and exotic taste (Silva et al., 2012). Prebioticoligosaccharides might be extracted from vegetables such aschicory but the industrial production is carried out usingmicrobial enzymes such as hydrolases and glucosyltrans-ferases (Boler and Fahey, 2012). The enzyme dextransucrasefrom Leuconostoc mesenteroides B-512 is a glucosyltransferasetraditionally applied to produce dextran in a medium con-taining only sucrose as the carbon source. When, besidessucrose, another carbohydrate is also present in the reactionmedium, the glucose units deviate from the dextran chain.This reaction is called an acceptor reaction and the mainacceptor studied for dextransucrase is maltose, which forms

from 1 to 10 (Rabelo et al., 2006; Rodrigues et al., 2005; Heinckeet al., 1999). The use of fruit juices as a vehicle for prebiotic

Elsevier B.V. All rights reserved.

cessi

566 food and bioproducts pro

oligosaccharides is an interesting alternative to dairy prod-ucts.

The recent studies on vegetable food matrices as a vehi-cle for prebiotic oligosaccharides target the incorporation ofthe oligosaccharides in the food matrix. In the present study,acerola juice was chosen as food matrix to develop a prebioticjuice due to its exotic taste and high vitamin C content. Insteadof adding oligosaccharides to the juice, they were synthesizeddirectly in the juice by the dextransucrase acceptor reaction,where glucose and fructose were the acceptors.

Despite the increasing interest in fruit juice consumption,their storage and transportation is a concern. Dried foods arean interesting alternative because drying is a process able toincrease the shelf life and decrease the transport and storagecosts of foodstuffs. Powdered juices present several advancesover the ready to drink product such as low weight and vol-ume, easy preparation, longer shelf life and storage at roomtemperature. The dehydration of fruit juices is not an easy taskdue to their high content of sugars and low weight organicacids, which results in powders with a low glass transitiontemperature. The use of proper carriers is an alternative toimprove the drying process (Goula and Adamopoulos, 2010).The most studied equipment for drying liquids is the spraydryer.

The spouted bed dryer is a useful alternative. It featuresexcellent heat transfer coefficients and a uniform drying tem-perature distribution, which might result in better qualitypowders compared to other dryers (Bacelos et al., 2008). Thisequipment has been used for the drying of pastes and sus-pensions, producing a powder of high quality and low cost(Bezerra et al., 2013). Drying of pastes in a spouted bed occursin the presence of inert particles, which act as a support forthe paste and as a heat source for drying. The paste mightbe atomized through a nozzle atomizer or dripped onto themoving bed of particles. During the process, the bed becomeswet and a thin layer of material is gradually formed aroundthe inert particles. The film on the particle surface is driedand the liquid bridges disappear gradually, resulting in a frag-ile, crumbly coating layer. Due to friction between individualparticles and the particles and the column wall, the film isremoved as a powder (Braga and Rocha, 2013). Spouted beddrying is often considered to be a good option for the dryingof granular products that are too coarse to be readily fluidized(Chua and Chou, 2003), which makes this equipment suitablefor drying fruit pieces (Cardoso and Pena, 2014; Contreras et al.,2012; Huang et al., 2009).

Few works have been published on the spouted bed dry-ing of fruit pastes and liquids (Medeiros et al., 2002; Cabralet al., 2007; Rocha et al., 2011; Fujita et al., 2013). Thus, theprebiotic acerola juice was dehydrated in a spouted bed anda preliminary characterization of the powder produced wasundertaken.

2. Materials and methods

2.1. Acerola juice preparation

The juice was prepared by diluting the commercial acerolapulps stored frozen (−20 ◦C) before the use. The dilution wascarried out using potable water at 1:2 (100 g of acerola pulp

to 200 mL of water) according to the manufacturer’s instruc-tions. The sugar content (glucose, fructose and sucrose) wasdetermined by HPLC as described further, and the juice pH

ng 9 4 ( 2 0 1 5 ) 565–571

was determined by direct measurement with a Marconi PA200 potentiometer (Marconi, Piracicaba—SP, Brazil).

2.2. Oligosaccharides synthesis

A 22 central composite rotated design (CCRD) with 3 centralpoints was carried out to evaluate the effect of the initialsugar concentration on the oligosaccharides production bythe dextransucrase acceptor reaction (Table 1). Due to thelow sugar content, sucrose and reducing sugars (fructose andglucose) were added to the juice to reach the desired concen-tration. The acceptors (glucose and fructose) were adjusted toreach equimolar proportions (1:1); the independent variableswere sucrose and reducing sugar concentrations. The pH ofthe juice was adjusted to 5.2 (optimum for enzyme synthe-sis) with NaOH. The syntheses were carried out batchwise in250 mL Erlenmeyer flasks containing 25 mL of juice at 30 ◦C for24 h. The enzyme activity was 1 IU/mL. The enzyme was syn-thesized in-house as described by Rabelo et al. (2006). Afterthe synthesis, the dextran was precipitated by adding threevolumes of ethanol 96% (v/v). The desired responses wereoligosaccharides formation, dextran and residual sugars (sug-ars not consumed during the synthesis).

2.3. Analytical determinations

2.3.1. Sugar quantification by HPLCSugars were quantified by HPLC in a Varian Pro Star system(Varian Inc, Palo Alto, California, USA) composed of two high-pressure pumps, Pro-Star model 210, a refractive index (RI)detector, Pro Star model 355, an auto sampler, Pro Star model410, and a Timberline column oven. Separation was achievedin an Aminex 87C (7.8 mm × 30 cm) column at 85 ◦C. Ultrapurewater (Milli-Q) at 0.6 mL/min was used as eluent. The sam-ples were filtered with a 0.45 �m cellulose acetate membrane;the injection volume was 20 �L. The detector temperature was35 ◦C and the software Star Chromatography WS 6.0 was usedto acquire and handle the data. Quantification was undertakenagainst a calibration curve built with external standards. Allsamples were analyzed in triplicate.

2.3.2. Dextran determinationThe dextran precipitated with ethanol was re-suspended indistilled water and quantified by phenol–sulfuric miniaturizedmethod as described by Fox and Robyt (1991).

2.3.3. Oligosaccharide determinationThe oligosaccharides and dextran formed during the synthe-sis, as well as the residual sugar (non-consumed sugars) weredetermined by mass balances according to the following equa-tions:

Oligosaccharides (g/L) = TScons − DXT (1)

YOLIGO(%) = Oligosaccharides (g/L)TSconsumed (g/L)

× 100 (2)

YDXT(%) = DXT (g/L)TSconsumed (g/L)

× 100 (3)

YRS(%) = Non consumed sugars (g/L)Total sugar (g/L)

× 100 (4)

where TScons total sugar consumed in the enzyme reaction(g/L), DXT dextran formed during the enzyme synthesis (g/L),

food and bioproducts processing 9 4 ( 2 0 1 5 ) 565–571 567

Table 1 – Experimental planning and responses for the oligosaccharide enzyme synthesis in acerola juice.

Run Sucrose (g/L) RS (g/L) Olig yield (%) Dextran (%) Residual sugar (%)

1 25.00 25.00 65.53 0.53 33.932 25.00 75.00 70.78 0.37 28.843 75.00 25.00 81.58 0.37 18.054 75.00 75.00 87.18 0.26 12.555 14.64 50.00 66.53 0.47 33.006 85.35 50.00 81.82 0.39 17.757 50.00 14.64 77.41 0.48 22.098 50.00 85.35 74.52 0.14 25.309 50.00 50.00 79.00 0 .41 20.58

10 50.00 50.00 79.34 0.47 20.1811 50.00 50.00 78.18 0.33 21.49

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RS—reducing sugar.

OLIGO (%) oligosaccharides yield (%), YDXT (%) dextran yield%), YRS (%) residual sugar yield (%).

.3.4. Oligosaccharide characterizationhe degree of polymerization of the oligosaccharides wasetermined by thin layer chromatography (TLC) in 20 × 20 cmhatman K6 plates (silica gel 60A). The solvent systemas acetonitrile/ethyl acetate/1-propanol/water (85:20:50:90

/v/v/v). The samples (10 �L) were applied at 1.5 cm from thelate border and the separation was achieved with two ascentsf the above solvent system. The plate was dried with aairdryer after each ascent. The oligosaccharide spots wereevealed by spraying a solution composed of 0.3% (w/v) of-naphthyletilnediamine in methanol containing 5% (v/v) ofoncentrated H2SO4. After drying naturally in a hood, the plateas heated in an oven at 120 ◦C to make the oligosaccharides

isible.

.4. Prebiotic juice drying in spouted bed

s shown in Table 2, a 22 central composite rotated designCCRD) with 3 central points, where the maltodextrin con-entration and the drying temperature were the independentariables, was carried out to evaluate the process viabil-ty. The response evaluated was the powder hygroscopicity.he prebiotic acerola juice was dried in a LabMaq spouteded model FBD 3.0 (Labmaq do Brasil, Ribeirão Preto SP,razil), equipped with a conical stainless steel drying chamber

h = 881 mm, D1 = 350 mm; D2 = 102 mm). The inert was 400 gf polystyrene spheres (3 mm) and the operating conditionsere: air pressure in the atomizer nozzle 80 bar; juice feedow rate 4.0 mL/min; atomizer nozzle air inlet rate 20 L/m2;ir inlet in the bottom nozzle 1.7 m3/s. The powder was sub-itted to the following analysis: moisture according to AOAC

1995), water activity (Jaya and Das, 2004) and re-dissolutionime (Goula and Adamopoulos, 2010).

The powder hygroscopicity was determined by weightingamples of 1 g in Petri dishes and exposing them to a controlledtmosphere cell with an air humidity of 79.5%. The samplesere weighted at 10 min intervals up to 40 min. The weight-

ng interval then increased to 20 min and the measurementsontinued until constant weight (equilibrium). The powderygroscopicity was calculated according to Eq. (5).

ygroscopicity (%) = [moisture (%) + ((c − b) / (b − a) × 100)]100 + moisture (%)

× 100 (5)

where a is the empty Petri dish weight (g); b is the Petridish + sample weight (g); c is the Petri dish + sample weight atthe equilibrium (g).

2.5. Quality analysis

The quality analysis was carried out for the control (non-prebiotic juice obtained from acerola pulp dissolution); thereconstituted non-prebiotic powder (non-prebiotic dried juice)and the reconstituted prebiotic powder (prebiotic dried juice).The powder reconstitution was achieved by dissolution indistilled water reaching the Brix obtained after maltodex-trin addition prior to drying. Carotenoids, flavonoids andanthocyanins were determined according to the methodol-ogy described by Francis (1982). Vitamin C was determined byHPLC as described by Pereira et al. (2013a,b).

2.6. Statistical analysis

The results were analyzed by ANOVA and the F test using thesoftware Statistica 10.0 (Statsoft Inc., Tulsa, Oklahoma, USA).The Tukey test was used for mean comparison when a surfaceresponse could not be applied.

3. Results and discussion

3.1. Oligosaccharides synthesis

The acerola juice pH was 3.18 and the total reducing sugar (glu-cose and fructose) content was 3.63 (g/L). The juice brix at 20 ◦Cwas 2.9 ◦Brix. Sucrose was not found in the juice. Due to thelow pH and the low sugar content, the in natura acerola juicedoes not allow the oligosaccharide synthesis through the dex-transucrase acceptor reaction. The juice pH was adjusted to5.2 with NaOH and the juice was enriched with external sugars(sucrose, glucose and fructose) to reach the desired concentra-tion in the experimental plan. The results presented in Table 1show that the applied strategy was efficient since the oligosac-charides yields were high and the dextran formation was verylow, indicating that the acceptor reaction took place in theacerola juice. The low residual sugars (non-consumed sugars)also demonstrated that about 60 to 90% of the available sugar,depending on the experimental condition, was incorporatedinto the oligosaccharide chain. Rabelo et al. (2009) synthesizedoligosaccharides by L. mesenteroides NRRL-B512F fermentation

in cashew apple juice and reported dextran yields in the rangeof 28 to 56%. The amount of dextran obtained herein was lowerthan 1% in all experimental runs, which indicates that almost

568 food and bioproducts processing 9 4 ( 2 0 1 5 ) 565–571

Table 2 – Experimental planning and hygroscopicity of acerola juice dried in spouted bed.

Run Drying temperature (◦C) Maltodextrin (%) Hydroscopicity (%)

1 50.00 10.00 10.41a ± 0.412 50.00 30.00 9.29b ± 0.183 70.00 10.00 11.91c ± 0.164 70.00 30.00 10.06ab ± 0.435 45.85 20.00 9.26b ± 0.226 74.14 20.00 9.66ab ± 0.597 60.00 5.85 9.68ab ± 0.278 60.00 34.14 7.32d ± 0.109 60.00 20.00 7.91d ± 0.18

10 60.00 20.00 7.96d ± 0.1411 60.00 20.00 7.68d ± 1.02

test (p < 0.05).

Fig. 1 – Surface response for oligosaccharides yield asfunction of sucrose and reducing sugar.

Different letters means significant differences according to the Tukey

all the acceptors molecules (glucose and fructose) consumedin the enzyme syntheses were incorporated into the oligosac-charides chain.

Table 3 shows the effects of the independent variable onthe target responses. The sucrose linear effect was positive onoligosaccharides yield and negative on residual sugars. Theincrease in sucrose concentration improved the oligosaccha-ride formation. The interaction effect was not significant onthe evaluated responses. Equations 6 to 8 present the fittedregression models for the responses presented in Table 1.

YOlig(%) = 51.30 + 0.59S + 0.20RS − 0.003S2

− 0.001RS2 + 0.0001S × RS (6)

YDXT(%) = 0.64 − 0.005S + 0.001RS + 0.0000S2

− 0.00006RS2 + 0.002S × RS (7)

YRS(%) = 48.02 − 0.005S + 0.001RS + 0.00002S2

+ 0.00006RS2 + 0.00002S × RS (8)

where YOlig (%) is the oligosaccharides yield (%); YDXT is the(%) dextran yield (%); YRS (%) is the residual sugar (%); S is thesucrose (g/L); RS is the reducing sugar (g/L).

The fitted models were evaluated by ANOVA and the F-testat 95% confidence interval. The calculated F-values for thefitted equations were 8.59, 7.33, and 8.41 for equations 6 to8, respectively. All the fitted models were statistically signif-icant since the calculated F-value was higher than the listedone (F5,5 = 5.05) at the given confidence interval (95%). The cor-relation coefficients were also adequate (0.89, 0.84 and 0.89for Eqs. (6) to (8), respectively). The fitted models were usedto build the response surface graphs presented in Figs. 1–3.Fig. 1 shows that sucrose was the main factor responsible forthe oligosaccharides formation in acerola juice. The higherthe initial sucrose the higher the oligosaccharides formedreaching concentrations higher than 80% of sugar conversioninto oligosaccharides. Above 60 g/L of sucrose, the oligosac-charides formation did not increase significantly, probablydue to substrate inhibition, which might occur at high sub-strate concentrations in enzyme reactions. In the acceptorreaction, dextran synthesis is inhibited when the amount ofacceptors in the reaction medium increases. This behavior isclearly seen in Fig. 2, where dextran formation decreases due

to the increase in reducing sugar concentration. The resid-ual sugars (sugars not consumed in the enzyme synthesis)decreased along with sucrose concentration indicating that

Fig. 2 – Surface response for dextran yield as function ofsucrose and reducing sugar.

food and bioproducts processing 9 4 ( 2 0 1 5 ) 565–571 569

Table 3 – Estimated effects.

YOlig (%) DXT (%) Residual sugars

Effect Error Effect Error Effect Error

Mean 78.84 1.75 0.40* 0.03* 20.75* 1.75*

Suc(L) 13.51* 2.14 −0.09* 0.04 −13.43* 2.15*

Suc(Q) −4.06 2.55 0.03 0.05 4.02 2.56RS(L) 1.69 2.14 −0.18* 0.04* −1.51 2.15RS(Q) −2.27 2.55 −0.08 0.05 2.34 2.56Suc × RS 0.17 3.03 0.03 0.06 −0.20 3.04

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∗ Significant at 95% of confidence interval; Suc—sucrose, RS—reducin

igh conversions were obtained when applying high initialugar concentrations (Fig. 3). According to the acceptor reac-ion mechanism, higher sucrose concentrations would leado higher dextran formation. This behavior was not seenor oligosaccharides synthesis in acerola juice. Thus, acerolauice might contain some component able to inhibit dextranynthesis even at high sucrose concentration. The sugar con-ersion into dextran was low compared to other publishedesults using maltose as the acceptor. The best operating con-ition for oligosaccharides synthesis in acerola juice must giveise to high oligosaccharides yield, low residual sugars and lowextran formation. This condition was found at high sucrosend high reducing sugar concentrations (above 75 g/L each).nder these conditions, the prebiotic acerola juice contained2.55% residual sugar, which means that of the 150 g/L of sug-rs available for enzyme synthesis only about 19 g/L was notransformed into enzyme products. The sugar content of therebiotic acerola juice is lower than that found in several nat-ral juices. Fresh squeezed orange juice contains up to 120 g/Lf total sugar (Rodoni et al., 2010). Natural cashew apple juiceontains up to 100 g/L of reducing sugar (Guilherme et al., 2012;ereira et al., 2013a,b). Grapefruit sugar ranges from 50 to 83 g/LLlamas et al., 2011). The sugar content of grape juice is above

20 g/L (Lieu and Le, 2010) and pineapple juice contains about0 g/L of sugar (Costa et al., 2013).

ig. 3 – Surface response for residual sugar yield asunction of sucrose and reducing sugar.

gar.

Fig. 4 shows the TLC analysis of the produced oligosac-charides. The degree of polymerization varied from 3 to 12.The results obtained were superior to those reported in pre-vious studies using maltose as acceptor (Heincke et al., 1999;Rodrigues et al., 2005; Rabelo et al., 2006) where the isomalto-oligosaccharides formed presented a degree of polymerizationup to 6. These results indicated that the prebiotic acerolajuice produced might be a good functional juice due to thehigher degree of polymerization obtained. According to pre-vious studies, the acceptor reaction would be favored by anexcess of acceptor over sucrose with acceptor:sucrose ratioshigher than 1.0 (Heincke et al., 1999; Lee et al., 2008). In thisstudy, the higher degree of polymerization was obtained inexperimental runs 3, 4 and 6 at low acceptor:substrate ratios(maximum 1.0).

3.2. Juice dehydration in spouted bed

The acerola juice (in natura) dehydration in the spouted bedwas done carrying out the experimental plan presented inTable 2. The effect of the independent variables on the pow-der hygroscopicity was not significant. Thus, response surfacemethodology was not applied and the results were statisticallyanalyzed by mean comparison with the Tukey test at 95% con-

fidence interval. The highest hygroscopicity was obtained inrun 3 (11.91%) and the lowest (∼7.9%) at the central point (60 ◦C

Fig. 4 – Degree of polymerization of the oligosaccharidesformed in the synthesis presented in Table 1. Lanes: 1–11experimental runs carried out according to Table 1;P—sucrose, glucose and fructose pattern.

570 food and bioproducts processi

Table 4 – Characterization of acerola powder obtained inspouted bed.

Parameter Powder acerola juice

Non prebiotic Prebiotic

Powder yield (%) 18.55a 12.48b

Moisture (%) 1.95a ± 0.09 1.91a ± 0.26Aw at 25 ◦C 0.17a ± 0.05 0.18a ± 0.00Hygroscopicity (%) 7.90a ± 0.03 9.89b ± 0.46Reconstitution time (s) 80.0a ± 14.9 51.0b ± 4.1

Different letters in the same line means significant difference

according to Tukey test (p < 0.05).

and 20% maltodextrin). The increase of maltodextrin did notaffect the powder hygroscopicity at 60 ◦C because no signifi-cant differences were observed using 34.14% maltodextrin. Onthe other hand, a significant increase in the hygroscopicitywas observed when low maltodextrin (5.85%) was employed.At high drying temperatures (70 ◦C), the increased maltodex-trin resulted in a significant decrease in the hygroscopicity.As the increase in maltodextrin increases the glass transitiontemperature, run number 8 (60 ◦C and 34.14% maltodextrin)was chosen for dehydration of prebiotic acerola juice.

The prebiotic juice was prepared as described above withthe acerola juice containing 75 g/L of sucrose and 75 g/L ofreducing sugar (run 4 in Table 1). This juice could not bedried in the spouted bed at the chosen drying condition (run8, Table 2) because the juice clogged the nozzle. This mighthave occurred due to due to the high viscosity of the productobtained when maltodextrin (34%) was added to the juice con-taining the prebiotic oligosaccharides. Thus, as the differencebetween the hygroscopicity obtained at the central point (runs9 to 11) was not statistically different from that obtained inrun 8 (Table 2), the prebiotic acerola juice containing 20% mal-todextrin was dried at 60 ◦C. The results obtained are shownin Table 3.

The non-prebiotic acerola powder yield was higher thanthat obtained for the prebiotic juice (Table 4). This differenceis due to the higher carbohydrate content of the prebioticjuice, which affects the glass transition temperature, yieldand hygroscopicity. The moisture and water activity (Aw)were not statistically different, indicating that the carbohy-drate content (including oligosaccharides) did not affect theseparameters. The reconstitution time was much higher for thenon-prebiotic juice.

The powder yields obtained for the acerola powders from

the spouted bed were low compared to the results obtainedin spray-dried fruit juices. Fazaeli et al. (2012) reported yieldsfrom 45 to 82% for spray dried plumb and Tonon et al. (2008)

Table 5 – Acerola juice quality parameters.

Quality parameter Control

pH 3.26a ± 0.03

◦Brix 2.9a ± 0.05

Sugars (g/L) 3.86a ± 0.29

Vitamin C (mg/100 g) 440.82a ± 0.05

Flavonoids (mg/100 g) 3.25a ± 0.08

Anthocyanins (mg/100 g) 3.21a ± 0.24

Carotenoids (mg/100 g) 0.39a ± 0.01

Different letters in the same line means significant difference according to(non dehydrated); non prebiotic—dehydrated and reconstituted acerola juioligosaccharides dehydrated and reconstituted.

ng 9 4 ( 2 0 1 5 ) 565–571

reported yields from 34 to 56% for acaí. However, this com-parison is not ideal because the hydrodynamics and dryingtemperatures in a spouted bed are completely different fromthose in a spray dryer. As noted above, little published data onfruit juice drying in spouted beds has been found elsewhereand, as a first attempt, the results obtained herein can be con-sidered satisfactory and can be improved in further studiesapplying a proper optimization protocol. Dehydration of fruitjuices is still a challenge because of the high sugar and organicacids content that contribute to the low glass transition tem-perature. These products tend to adhere to the bed walls andon the inert particles.

Table 5 presents the quality parameters of the acerola juiceobtained by pulp dilution, the reconstituted non-prebioticacerola juice powder, and the reconstituted prebiotic acerolajuice powder. The solid content (◦Brix) is higher in the recon-stituted juices due to the maltodextrin addition as dryingadjuvant. Some vitamin C loss was observed in the reconsti-tuted juices due to the heat treatment (drying) and the juiceexposition at room temperature for the enzyme synthesis.However, the vitamin C content in the prebiotic reconstitutedjuice is still high allowing the prebiotic acerola juice to beclassified as a vitamin C source. On the other hand, no signif-icant loss of the acerola bioactive compounds (anthocyanins,flavonoids and carotenoids) was observed.

The quality preservation is the main advantage of thespouted bed drying. The low drying temperature (60 ◦C) pre-served the quality parameters of the juice. The reconstitutedprebiotic juice presented vitamin C contents higher than thedietary recommended intake: 90 mg/day for adult men and75 mg/day for adult women (DRI, 2006). According to the datapresented in Table 5, the developed prebiotic acerola juice is alow sugar product with 21 g/L of total sugar.

4. Conclusion

The use of acerola juice as substrate for oligosaccharidessynthesis through the dextransucrase acceptor reaction is agood alternative because high concentration and high conver-sion of sugar into oligosaccharides were found. The degree ofpolymerization obtained was higher than that obtained in pre-viously published studies using maltose (a stronger acceptorfor dextransucrase). The prebiotic acerola juice can be dried ina spouted bed using maltodextrin as carrier at 60 ◦C. The lowtemperature employed in a spouted bed dryer is an advan-tage for the dehydration of fruit juices as it avoids nutritional

losses caused by the high temperature used in spray dryers.However, the drying processing still needs improvements toincrease the powder yield. This is the subject of future work.

Non prebiotic Prebiotic

3.3a ± 0.07 3.15a ± 0.1215.6b ± 0.05 28.5c ± 0.004.21a ± 0.18 21.12b ± 0.04

356.73b ± 4.12 256.64c ± 1.533.02a ± 0.20 2.95a ± 0.133.02a ± 0.83 2.30a ± 0.120.36a ± 0.00 0.36a ± 0.05

Tukey test (p < 0.05). Control—acerola juice obtained by pulp dilutionce; prebiotic–acerola juice submitted to enzyme synthesis containing

ssing

A

AIC

R

A

B

B

B

B

C

C

C

C

C

C

L

D

F

F

F

F

F

food and bioproducts proce

cknowledgments

uthors thank to CNPq (573781/2008-7) thought the Nationalnstitute of Science and Technology of Tropical Fruits, FUNCAP,APES and BNB for the financial support and scholarships.

eferences

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