Journal of Food Engineering 151 (2015) 60–68

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Journal of Food Engineering

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Microencapsulation of freeze concentrated Ilex paraguariensis extractby spray drying

http://dx.doi.org/10.1016/j.jfoodeng.2014.10.0310260-8774/� 2014 Elsevier Ltd. All rights reserved.

⇑ Corresponding author. Tel.: +55 48 37215384; fax: +55 48 37219943.E-mail address: renata.amboni@ufsc.br (R.D. de Mello Castanho Amboni).

Graciele Lorenzoni Nunes a, Brunna Cristina Bremer Boaventura a, Stephanie Silva Pinto a, Silvani Verruck a,Fábio Seigi Murakami b, Elane Schwinden Prudêncio a, Renata Dias de Mello Castanho Amboni a,⇑a Universidade Federal de Santa Catarina, Departamento de Ciência e Tecnologia de Alimentos, Rod. Admar Gonzaga, 1346, Itacorubi, 88034-001 Florianópolis, SC, Brazilb Universidade Federal do Paraná, Departamento de Farmácia, Av. Pref. Lothário Meissner, 632, Jardim Botânico, 80210-170 Curitiba, PR, Brazil

a r t i c l e i n f o

Article history:Received 14 August 2014Received in revised form 1 October 2014Accepted 31 October 2014Available online 3 December 2014

Keywords:Ilex paraguariensisFreeze concentrationMicroencapsulationTotal phenolic compoundsAntioxidant activityMaltodextrin

a b s t r a c t

Concentrated extract of mate leaves obtained from the third stage of the freeze concentration processwas microencapsulated with maltodextrin by spray drying. The effect of maltodextrin concentration(20%, 30%, and 40%) on the phenolic compounds, antioxidant activity, microencapsulation yield, morphol-ogy, particle size, moisture content, water activity, dissolution, hygroscopicity, color and thermal proper-ties were investigated. The retention of phenolic compounds after microencapsulation by spray dryingand the stability of the microcapsules at 4 �C for 45 days were also determined. It was possible to notean enhancement of the total phenolic content and antioxidant activity of mate leaves aqueous extractobtained through freeze concentration. The high concentrations of maltodextrin in the microcapsulespromoted higher phenolic compounds microencapsulation yield, higher particle size and longer timerequired for the powders to dissolve in water, while moisture content, water activity and hygroscopicitydecreased. The color parameters indicated that maltodextrin protected the microcapsules against heatduring spray drying. The results of the thermoanalyses suggested an increase in the stability of the micro-capsules. Besides, the microcapsules produced with maltodextrin showed better retention and enhancedstability at 4 �C for 45 days.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction

Yerba mate (Ilex paraguariensis) is a native plant of South Amer-ican countries (Argentina, Uruguay, Paraguay and Brazil) and itsprocessed leaves are consumed as infusion by the local population(Heck and de Mejía, 2007; Bracesco et al., 2011). Several scientificstudies have shown the beneficial effects of yerba mate, mostlyrelated to its antioxidant properties because of the high contentof phenolic compounds in the aqueous extract (Bastos et al.,2007; Heck and de Mejía, 2007; Bracesco et al., 2011; Anesiniet al., 2012). Some studies have been conducted aiming to improvethe composition of mate aqueous extract obtained through con-centration technologies, such as nanofiltration (Murakami et al.,2011; Prudêncio et al., 2012) and freeze concentration(Boaventura et al., 2013). Freeze concentration technologyenhances the concentration of liquid food products by freezingand subsequent separation of part of the frozen water from theliquid product (Belén et al., 2012). From the food industry’s pointof view, freeze concentration is a very suitable technology because

it retains the nutritional quality of liquid foods and minimizes theloss of thermolabile components, such as phenolic compounds(Aider et al., 2009; Sánchez et al., 2010). However, the mate leavesaqueous extract concentrated by freeze concentration technologycould be relatively unstable due to the presence of large amountsof phenolic compounds (Nicoli et al., 1999; Rosa et al., 2014). Infact, these compounds are highly susceptible to degradation byseveral factors, such as oxygen, light, pH and heat (Bakowskaet al., 2003). On the other hand, the stability of polyphenols maybe improved by using microencapsulation technology, such asspray drying (Ersus and Yurdagel, 2007).

The microencapsulation process consists of the packing of par-ticles by using a wall material (encapsulating agent) to protect andextend its functionality. This process can be an option to modifysome characteristics of a product, such as improving its appearanceand preventing undesirable interactions with the carrier foodmatrix (Gouin, 2004; Kuang et al., 2010). Numerous wall materialsare available for food application, such as arabic gums, proteinsand maltodextrins (Shahidi and Han, 1993). However, the use ofdifferent encapsulating agents for production of microcapsulescan result in different physical properties, depending on the struc-ture and the characteristics of each agent (Tonon et al., 2009), and

G.L. Nunes et al. / Journal of Food Engineering 151 (2015) 60–68 61

it can also change functional properties of the microcapsules (Chenet al., 2005).

Maltodextrins, obtained through acid hydrolysis of somestarches (corn, potato and others) generally have high water solu-bility and hence, can contribute to the significant reduction of theapparent viscosity of feed favouring the atomization and drying ofthe liquid feeds (Gharsallaoui et al., 2007). Therefore, the objectiveof this study was to microencapsulate the freeze concentrated I.paraguariensis extract by spray drying using maltodextrin asencapsulating agent.

2. Materials and methods

2.1. Chemicals

Folin–Ciocalteu phenol reagent, 1,1-diphenyl-2-picrylhydrazyl(DPPH), 2,4,6-tris(2-pyridyl)-s-triazine (TPTZ), 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), chlorogenic acid,3,4-dihydroxybenzoic acid, gallic acid, caffeic acid, p-coumaricacid, 3,5-dicaffeoylquinic acid, and maltodextrin (DE 16.5–19.5)were purchased from Sigma Chemical Co. (St. Louis MO USA).Methanol, acetic acid and n-butanol were obtained from Vetec(Duque de Caxias, RJ, Brazil). All reagents were either of analyticalor of chromatographic grade.

2.2. Plant material and preparation of aqueous extract

Leaves of I. paraguariensis A. St. Hill were harvested in Cat-anduvas-SC, southern of Brazil, in January 2013. The leaves wereoven-dried in a forced-air oven (FABBE, 171, São Paulo, Brazil) for24 h at 45 ± 2 �C and ground in a knife mill (Marconi, MA-580,Piracicaba, Brazil) until achieving a particle size smaller than3.5 mm. The samples were packed in airtight plastic bags andthen in aluminum packs at �18 ± 1 �C until the preparation ofthe aqueous extract.

The mate leaves aqueous extract was prepared using 30 g ofground leaves suspended in 1 L of distilled water, as described byMurakami et al. (2011). After 3 min at 90 �C, the mate leaves extractwas filtered twice with filter paper (12.5 cm diameter and 25 lmpore size) using a vacuum pump (Prismatec, 131, Itu, Brazil). Theextract volume was finally completed to 1 L with distilled water.

2.3. Protocol of freeze concentration procedure

The diagram of freeze concentration procedure is shown inFig. 1. Two fractions were obtained one denoted concentrated fluid(CF) and other denoted ice (I). The freeze concentration techniqueconsisted of block freeze concentration, following the methodologydescribed by Boaventura et al. (2013). Briefly, an initial volume of 3L of mate leaves aqueous extract was divided into three batches of1 L and then frozen at �20 ± 2 �C. The freezing process was con-ducted in a freezer unit (Electrolux, FE 18, São Carlos, Brazil) byindirect cooling. Once the feed solution was frozen, 50% of the ini-tial volume was defrosted at room temperature (20 ± 2 �C). Thedefrosted liquid constituted the concentrated fluid of the firstfreeze concentration stage. This procedure was repeated until thethird stage. The ice remaining from each freeze concentration stageand an aliquot of each concentrated fluid were stored at �20 ± 2 �Cfor posterior chemical analysis.

The efficiency of the freeze concentration process (PE), accord-ing to Belén et al. (2012), was determined based on the total phe-nolic content (TPC). The efficiency of the process is referred to asthe increase of the TPC in the concentrated fluid in relation tothe TPC remaining in the ice and it was calculated through the fol-lowing equation:

PE ¼ PCCn � PCIn

PCCn� 100 ð1Þ

where PCCn is the TPC in the concentrated fluid (mg) in a givenfreeze concentration stage and PCIn is the TPC in the ice (mg) in agiven freeze concentration stage.

The concentrated fluid obtained from the freeze concentrationstage that showed the best process efficiency, with the highestTPC in the concentrated fluid in relation to the TPC in the ice,was chosen to be used in the microencapsulation by spray drying.

2.4. Microencapsulation by spray drying

Three feed mixtures were prepared by mixing the freeze con-centrated fluid with 20% (w/v), 30% (w/v) and 40% (w/v) of malto-dextrin, denoted as M20, M30 and M40, respectively. The freezeconcentrated fluid without addition of maltodextrin was also spraydried and denoted as control (Fig. 1). Each feed mixture washomogenised with Ultraturrac T25 (IKA�, Staufenim Breisgau, Ger-many) at 14,000g for 2 min. The resultant mixtures were fed to aBuchi B-290 mini spray dryer (Buchi, Flawil, Switzerland). Thespray dryer was operated at inlet temperature ranging 150 ± 5 �Cand outlet temperature of 50 ± 5 �C. The air flow, rate of feedingand atomization pressure were 35 m3/h, 6 mL/min, and 0.7 MPa,respectively. The operational spray dryer parameters were basedon previous studies (data not shown).

The microcapsules were evaluated in relation to their total phe-nolic content, antioxidant activity, microencapsulation efficiency,morphology, particle size, moisture content, water activity, disso-lution, hygroscopicity, color and thermal properties on the day oftheir manufacture. The retention of phenolic compounds afterthe process of spray drying was also determined and the stabilityof the microcapsules during storage for 45 days at 4 �C wasobserved. All the experiments were performed in triplicate, exceptthose for morphology and particle size.

2.5. Determination of phenolic compounds and antioxidant activity

The spray dried powders (control, M20, M30 and M40) weresubmitted to phenolic compounds and antioxidant activity analy-sis. Firstly, the coating material structure of the microcapsuleswere completely removed by the method proposed by Robertet al. (2010), with modifications, as following: 200 mg of microcap-sules were accurately weighed and 1 mL of ethanol:acetic acid:-water (50:8:42 v/v/v) was added. This dispersion was agitatedusing a Vortex (VTX-F Biomixer, Brazil) (1 min) and then an ultr-asonicator (Maxi Clean 1650A, Indaiatuba, SP, Brazil) twice for20 min. The supernatant was centrifuged at 112,000g for 5 minand then filtered (0.45 lm Millipore filter).

The total phenolic content (TPC) was analysed according toFolin–Ciocalteau method described by Singleton et al. (1965). Theappropriate dilutions of samples were oxidised with Folin–Ciocal-teu reagent and its reaction was neutralised with sodium carbon-ate. The absorbance of the resulting blue color was measured at765 nm, after 60 min, with a UV–VIS spectrophotometer (ModelU-1800, Hitachi, Tokyo, Japan). Results were expressed in mg ofchlorogenic acid equivalent (CAE) per mL.

Ferric reducing antioxidant power (FRAP) was determinedaccording to Benzie and Strain (1996). In this procedure, the anti-oxidants present in the samples are evaluated as reducers of Fe3+ toFe2+, which is chelated by 2,4,6-tris(2-pyridyl)-S-triazine (TPTZ) toform a complex (Fe2+–TPTZ) with maximum absorbance at 593 nm.The results were calculated using Trolox as a standard and wereexpressed as Trolox equivalents in lmol/mL.

The antioxidant activity was also determined using 2,2-diphe-nyl-1-picrylhydrazyl radical (DPPH) as a free radical, according

STAGE 1

Ice (I 2) Concentratedfluid (CF 2)

1.5 L of CF 1

Feed extract(3L)

Ice (I 1) Concentratedfluid (CF 1)

Ice (I 3) Concentratedfluid (CF 3)

750 mL of CF 2

STAGE 2

STAGE 3

Microencapsulation by spray drying

20 %maltodextrin

30 %maltodextrin

40 %maltodextrin

Without maltodextrin

Control M20 M30 M40

Fig. 1. Diagram of freeze concentration procedure in mate leaves aqueous extract and microencapsulation process of concentrated fluid from the third stage of freezeconcentration.

62 G.L. Nunes et al. / Journal of Food Engineering 151 (2015) 60–68

methodology proposed by Brand-Williams et al. (1995). Briefly,an aliquot of 0.1 mL of each extract was mixed with 3.9 mL DPPHin methanol (60 lM). The mixture was vigorously shaken andthen the absorbance rate was measured at 515 nm every 10 minuntil it stabilized (Model U-1800, Hitachi, Tokyo, Japan). Metha-nol was used as a blank instead of DPPH solution. The assaywas determined in order to express the effective concentrationof sample in which DPPH radicals were 50% scavenged. Resultswere expressed as the half maximal effective concentration(EC50). EC50 results were obtained by interpolation from linearregression analysis.

Phenolic compounds were also isolated and analysed using anHPLC system (Shimadzu LC-20AT, Kyoto, Japan) equipped with areversed-phase C18 column with 150 � 4.6 mm i.d. with 5 lm par-ticle size (Supelco, Nucleosil, Bellefonte, USA) (Pagliosa et al., 2010;Schuldt et al., 2005). The identification of the phenolic compoundswas carried out by comparing retention times and absorption spec-tra of the peaks with those of standard compounds. Quantitativeanalysis was performed using standard calibration curves of chlor-ogenic acid (5-caffeoylquinic acid), 3,5-dicaffeoylquinic acid (iso-chlorogenic acid), caffeic acid, p-coumaric acid, 3,4-dihydroxybenzoic acid and gallic acid. Final concentration of com-pounds in the samples was determined as an average content afterthree consecutive injections.

2.6. Phenolic compounds microencapsulation yield

For determination of surface phenolic compounds, 200 mg ofmicrocapsules were treated with 2 mL of a mixture of ethanoland methanol (1:1), respectively. These dispersions were agitatedin a Vortex (VTX-F Biomixer, Brazil) for 1 min at room temperatureand then filtered (0.45 lm Millipore filter) (Robert et al., 2010). Thetotal phenolic content was determined by Folin–Ciocalteaumethod (Singleton et al., 1965), as previously described. Thesurface phenolic compounds (SPC) percentage and the phenoliccompounds microencapsulated yield (PCMY) were calculated asdescribed by Robert et al. (2010), with modifications, accordingto Eqs. (2) and (3), respectively.

SPC ð%Þ ¼ Surface phenolic compoundsTheoretical total phenolic compounds

� 100 ð2Þ

PCMY ð%Þ ¼ 100� SPC ð%Þ ð3Þ

2.7. Morphology and particle size

The morphology and particle size of the microcapsules wereobserved with a Jeol scanning electron microscope model JSM6390 LV (Jeol, Tokyo, Japan) at an accelerating voltage of 10 kV.

Table 1Total phenolic content (TPC) of the feed extract (mate leaves aqueous extract),concentrated fluid (CF) and ice (I) at each freeze concentration stage and the processefficiency (PE) in relation to TPC.

TPC (mg CAE/mL) PE (%)

Feed extract 4.13 ± 0.19dA

Stage1 CF 1 7.29 ± 0.02c 83.21 ± 0.65�

I 1 1.20 ± 0.05C

Stage2 CF 2 11.61 ± 0.02b 89.74 ± 0.32⁄

I 2 1.21 ± 0.04C

Stage3 CF 3 15.60 ± 0.06a 90.75 ± 0.21⁄

I 3 1.45 ± 0.03B

Data are expressed as mean ± DP (n = 3). Different superscript lowercase lettersindicate significant difference (P < 0.05) between the feed extract and the concen-trated fluid at each freeze concentration stage. Different superscript uppercaseletters indicate significant difference (P < 0.05) between the feed extract and the iceat each freeze concentration stage. Different symbols indicate significant difference(P < 0.05) in the PE of each freeze concentration stage. CAE, chlorogenic acidequivalent.

G.L. Nunes et al. / Journal of Food Engineering 151 (2015) 60–68 63

Prior using the scanning electron microscope (SEM), the sampleswere placed on a stub and coated with gold with a vacuum-sput-tering coater (Leica, EM SCD 500, Wetzlar, Germany), as describedby Lian et al. (2002). At least 120 particles from each of the differ-ent microcapsules produced were measured to calculate theiraverage diameter (Krasaekoopt et al., 2004).

2.8. Moisture

The moisture content of the spray dried powders was deter-mined by oven drying at 105 �C until reaching constant weight,according to AOAC method (2005).

2.9. Water activity

Water activity was measured with an Aqualab 4 TE analyzer(Decagon Devices, USA) after samples were stabilized at 25 �C for15 min.

2.10. Dissolution

The dissolution was carried out by adding 2 g of powders into50 mL of distilled water (El-Tinay and Ismail, 1985). The mixturewas stirred in a 100 mL low form glass beaker with a magnetic stir-rer (Dist, model DI 03, Florianópolis, Brazil) at 892 rpm and a stir-ring bar measuring 2 mm � 7 mm. The time required for thecomplete dissolution of material was evaluated.

2.11. Hygroscopicity

The hygroscopicity of the spray dried powders was determinedaccording to the method proposed by Cai and Corke (2000) andFritzen-Freire et al. (2012). Samples of each powder (approxi-mately 1 g) were placed at 25 �C in an airtight glass container withNaCl saturated solution (75.3% RH). After 1 week, the samples wereweighed and their hygroscopicity was expressed as g of adsorbedmoisture per 100 g of dry solids (g/100 g).

2.12. Color analysis

The color analysis was performed with a Minolta Chroma MeterCR-400 colorimeter (Konica Minolta, Osaka, Japan), adjusted tooperate with D65 lightning and 10� observation angle. The CIELabcolor scale was used to measure the L⁄, a⁄ and b⁄ parameters. In theCIELab color scale, the L⁄ parameter ranges from 0 to 100, indicat-ing the color variation from black to white; the a⁄ axis shows thevariation from red (+a⁄) to green (�a⁄); while the b⁄ axis showsthe variation from yellow (+b⁄) to blue (�b⁄).

2.13. Differential scanning calorimetry analysis (DSC)

The DSC analysis was carried out in order to evaluate the phase-change behaviors and physical interactions of the microcapsules.The DSC curves were obtained using a Shimadzu DSC-60 cell (Shi-madzu, Kyoto, Japan). Samples of approximately 2 mg of powderwere placed in aluminum sealed pans, under a dynamic syntheticair atmosphere (100 mL/min) and heated from 30 �C to 300 �C ata heating rate of 10 �C/min. The DSC equipment was preliminarilycalibrated with a standard reference of indium.

2.14. Thermogravimetric analysis/derivative thermogravimetry (TGA/DrTGA)

The thermal stability and degradation behaviors of the controlsample and microcapsules were evaluated using thermogravime-try/derivative thermogravimetry analysis. The curves were

obtained using a DTG-60 thermobalance (Shimadzu DTG-60,Kyoto, Japan). Approximately 7 mg of samples were placed in alu-minum pans and heated from 30 �C to 300 �C at a rate of 10 �C/minunder dynamic synthetic air atmosphere (100 mL/min). The equip-ment was preliminarily calibrated with a standard reference of cal-cium oxalate.

2.15. Storage stability test

The microcapsules M20, M30, M40 and the control were evalu-ated with regard to phenolic compounds stability during storage at4 ± 1 �C. Samples were placed in amber vials and stored in the darkfor 45 days. To determine the total phenolic content (TPC) dupli-cate vials were removed every 15 days until assay was completed.

2.16. Statistical analysis

The data analysis was carried out using STATISTICA 7.0 software(StatSoft Inc., Tulsa, USA). Analysis of variance (ANOVA) was usedto determine significant differences (P < 0.05) among the micro-capsules. Differences between means were detected using Tukey’stest.

3. Results and discussion

3.1. Efficiency in the concentration of total phenolic content

Table 1 shows the total phenolic content (TPC) of concentratedfluid (CF) and ice (I), and also freeze concentration process effi-ciency (PE). The effect of freeze concentration was highly signifi-cant (P < 0.05) on TPC in all the three CFs when compared to theinitial extract, increasing their values with the progress of thefreeze concentration. In the ice fractions, it was observed that TPCsin the first and second stages (I1 and I2) were significantly lower(P < 0.05) than in the third stage (I3). Aider et al. (2007) reportedthat phenolics are able to bind a great number of water moleculesbecause of hydrogen bonds. Thus, during the concentration ofphenolics in the solution, the interstitial water becomes less avail-able for freezing.

The highest result for process efficiency (PE) was noted in thethird freeze concentration stage (Table 1). These results differedfrom those noted by Belén et al. (2012) and Boaventura et al.(2013), who reported that the efficiency of the freeze concentrationprocess decreased as a function of the procedure stages resultingfrom an increase in the retention of solutes in the ice. However,the TPC in the residual ice was lower than that reported by Belénet al. (2012) and Boaventura et al. (2013) for waste water from tofu

64 G.L. Nunes et al. / Journal of Food Engineering 151 (2015) 60–68

production and from mate leaves aqueous extract, respectively.This fact suggests that the lower retention of solute in the residualice found in the present study promoted increased efficiency of theprocess. Based on these results, the concentrated fluid from thethird freeze concentration stage (CF3) was used in the microencap-sulation by spray drying.

3.2. Powder analysis

The microcapsules produced with 30% and 40% of maltodextrinshowed higher (P < 0.05) phenolic compounds microencapsulatedyield (PCMY) values than those produced with 20% of maltodextrin(Table 2). Similar results were observed by Cilek et al. (2012), Panget al. (2014) and Saénz et al. (2009) for microencapsulation of phe-nolic compounds from sour cherry pomace, Orthosiphon stamineusextract and cactus pear pulp using maltodextrin, respectively.

The TPC content of the powders was significantly lower whenthe concentration of maltodextrin was increased from 20% to 40%(Table 2). This can be due to maltodextrin’s concentration effect.A similar trend was noted by Mishra et al. (2014) and Çam et al.(2014).

Increase in the concentration of maltodextrin, which itself hasneither free radical scavenging activity nor ferric reducing antiox-idant power, resulted in lower DPPH and FRAP activities. This maybe due to the dilution effect of maltodextrin when its concentra-tion was raised. These results are in agreement with those reported

Table 2Effect of maltodextrin on total phenolic content, activity antioxidant and phenolic compo

Samples PCMY (%) Total phenolic content (mg/mL chlo

M20 95.97 ± 0.29b 12.60 ± 0.03d

M30 96.72 ± 0.05a 13.45 ± 0.25c

M40 96.60 ± 0.06a 9.21 ± 0.03b

Control – 21.62 ± 0.04a

Data are expressed as mean ± DP (n = 3). Different superscript letters in the same line incompounds microencapsulated yield; Control (spray dried CF3 without addition of maltM30 (CF3 microencapsulated by spray drying with 30% of maltodextrin), and M40 (CF3

Fig. 2. Retention of polyphenol compounds of control (spray dried CF3 without addimaltodextrin), M30 (CF3 microencapsulated by spray drying with 30% of maltodextricompared to CF3. Data are expressed as mean ± standard deviation (). Different lowemicrocapsules produced with maltodextrin and control.

by Mishra et al. (2014) in amla juice powder. However, Kha et al.(2010) observed that on varying the maltodextrin level from 10%to 20% there was no significant effect on total antioxidant activityof gac (Momordica cochinchinensis) juice powder.

The polyphenols retention of the control (spray dried CF3 with-out addition of maltodextrin), and maltodextrin spray dried pow-ders M20, M30 and M40 were compared to the concentratedfluid from the third freeze concentration stage (CF3) (Fig. 2) toevaluate the level of polyphenols preservation. All the maltodex-trin spray dried powders showed a good retention (ranging from43.14% to 87.53%) of phenolic compounds. The control showedsevere decrease of polyphenol content, especially for caffeic acid(77.01%) and 3,5-dicaffeoylquinic acid (71.56%) when comparedto CF3. The retentions of individual polyphenol without microen-capsulation were equal to 45.20%, 50.25%, 34.54%, 73.42%, 22.99%and 28.44% for gallic acid, p-coumaric, chlorogenic acid, 3,4-dihy-droxybenzoic acid, caffeic acid and 3,5-dicaffeoylquinic acid,respectively. These results suggest that maltodextrin had a protec-tive effect on the microencapsulation of phenolic compounds.Buchner et al. (2006) reported that a higher presence of hydroxylgroups in the molecular structure of polyphenols made them moresusceptible to thermal degradation.

Fig. 3 shows SEM micrographs of the control, M20, M30 andM40 samples. It was noted that the concentration of maltodextrinhas a significant influence on the morphology of the microcapsules.After spray drying, the control sample showed a more deformed

unds microencapsulation yield of control and microcapsules samples.

rogenic acid) DPPH (EC50) (lg/mL) FRAP (lmol/mL)

19.98 ± 0.26b 19.48 ± 0.05d

19.63 ± 0.10b 21.16 ± 0.64c

29.52 ± 0.32c 15.76 ± 0.31b

12.29 ± 0.08a 24.97 ± 0.07a

dicate significant differences (P < 0.05) between the microcapsules. PCMY: phenolicodextrin), M20 (CF3 microencapsulated by spray drying with 20% of maltodextrin),microencapsulated by spray drying with 40% of maltodextrin).

tion of maltodextrin), M20 (CF3 microencapsulated by spray drying with 20% ofn), and M40 (CF3 microencapsulated by spray drying with 40% of maltodextrin)rcase letters indicate significant differences (P < 0.05) between the CF3 and the

Fig. 3. Micrographs of microcapsules produced with: (a) Control (spray dried CF3 without addition of maltodextrin), (b) M20 (CF3 microencapsulated by spray drying with20% of maltodextrin), (c) M30 (CF3 microencapsulated by spray drying with 30% of maltodextrin) and (d) M40 (CF3 microencapsulated by spray drying with 40% ofmaltodextrin).

G.L. Nunes et al. / Journal of Food Engineering 151 (2015) 60–68 65

shape, with extensive wrinkles, and a more dented surface thanthose microencapsulated with maltodextrin. Rosenberg et al.(1985) stated that the formation of dented surfaces of spray driedparticles is attributed to the shrinkage of the particles during thedrying process. According to Ré (1998), surface imperfections, suchas wrinkles or cracks, occur when there is slow film formation dur-ing the drying of the atomized droplets. However, Lian et al. (2002)reported that cracks may facilitate the escape of heat from insidethe particle after drying. Similar morphology has been reportedby Robert et al. (2010) and Saénz et al. (2009) for microcapsulesproduced with maltodextrin.

The microcapsules showed assorted sizes, between 10.69 and13.95 lm (Table 3), where higher maltodextrin concentrationsled to the production of larger particles. Fang and Bhandari(2010) reported that these size values, which could vary from 10to 100 lm, are expected for microcapsules obtained by spray dry-ing. According to Pang et al. (2014), this fact could be related tofeed viscosity, which exponentially increased with the increase ofmaltodextrin concentration. This is in agreement with the resultsnoted by Tonon et al. (2008) and Pang et al. (2014).

Table 3Physico-chemical properties of control and microcapsules.

Properties Spray dried powders

Control M20

Particles size (lm) 10.69 ± 2.12a 12.9Moisture (g/100 g) 3.82 ± 0.06a 3.6Water activity 0.279 ± 0.005a 0.25Solubility in water (s) 292.01 ± 7.09c 336.3Hygroscopicity (g/100 g) 25.91 ± 0.83a 20.4

Data are expressed as mean ± DP (n = 3). Different superscript letters in the same line indried CF3 without addition of maltodextrin), M20 (CF3 microencapsulated by spray dryinof maltodextrin), and M40 (CF3 microencapsulated by spray drying with 40% of maltod

The moisture content of spray dried powder M40 was lower(P < 0.05) than that of the control (Table 3). However, Abadioet al. (2004) reported that an increase in the concentration of mal-todextrin from 10% to 15% resulted in a decrease in the final mois-ture content of pineapple juice powder.

High water activity indicates more free water available for bio-chemical reactions and hence shorter shelf life. The water activity(aw) for the microcapsules obtained (Table 3) is within the normalrange for atomized products, and also within the recommendedlimit to ensure powder stability (<0.3) (Tonon et al., 2009). It wasobserved that an increase in the concentration of maltodextrincauses a decrease in the water activity of the microcapsules. Theseresults were consistent with those obtained by other researchers(Tonon et al., 2009; Vardin and Yasar, 2012; Caliskan and Dirim,2013).

Due to its high solubility in water, maltodextrin is one of themost frequently used ingredients as wall material for spray dryingof plant extracts (Cano-Chauca et al., 2005). The time required forthe powders to dissolve in water was higher (P < 0.05) for micro-capsules M40, followed by M30, and M20 (Table 3). Therefore, this

M30 M40

0 ± 2.11b 13.08 ± 2.73c 13.95 ± 2.94d

5 ± 0.34a 3.14 ± 0.70ab 2.22 ± 0.56b

2 ± 0.035b 0.211 ± 0.001b 0.205 ± 0.004c

3 ± 12.22c 421.66 ± 21.54b 588.66 ± 55.96a

7 ± 1.82b 18.75 ± 0.31b 17.83 ± 0.08b

dicate significant differences (P < 0.05) between the microcapsules. Control (sprayg with 20% of maltodextrin), M30 (CF3 microencapsulated by spray drying with 30%extrin).

Table 4Results of color analysis of control and microcapsules.

Spray dried powders L⁄ a⁄ b⁄

Control 62.33 ± 0.18d 2.09 ± 0.01a 25.52 ± 0.29a

M20 73.30 ± 1.13c 0.66 ± 0.17b 21.31 ± 1.23b

M30 75.75 ± 0.16b 0.14 ± 0.01c 20.65 ± 0.64bc

M40 79.41 ± 0.33a �0.38 ± 0.06d 18.84 ± 0.73c

Data are expressed as mean ± DP (n = 3). Different superscript letters in the sameline indicate significant differences (P < 0.05) between the microcapsules. Control(spray dried CF3 without addition of maltodextrin), M20 (CF3 microencapsulatedby spray drying with 20% of maltodextrin), M30 (CF3 microencapsulated by spraydrying with 30% of maltodextrin), and M40 (CF3 microencapsulated by spray dryingwith 40% of maltodextrin).

ig. 4. DSC (a) TGA and DrTGA (inserted figure) and (b) curves of control andicrocapsules. Control (spray dried CF3 without addition of maltodextrin), M20F3 microencapsulated by spray drying with 20% of maltodextrin), M30 (CF3icroencapsulated by spray drying with 30% of maltodextrin), and M40 (CF3icroencapsulated by spray drying with 40% of maltodextrin).

66 G.L. Nunes et al. / Journal of Food Engineering 151 (2015) 60–68

current assay reveals that the increase of maltodextrin concentra-tion caused a decrease in the solubility of spray dried powders. Thesame behavior was noted by Abadio et al. (2004), who reportedthat a decrease in maltodextrin concentration improved solubilityof the powders. According to Chen and Patel (2008) and Fang et al.(2008), solubility is an important criterion to evaluate the prod-uct’s behavior in the aqueous phase since food powders requiregood solubility to be useful and functional.

The values of hygroscopicity can be seen in Table 3. Addition ofmaltodextrin affected (P < 0.05) the hygroscopicity of the micro-capsules. On the other hand, Rodríguez-Hernández et al. (2005),Mishra et al. (2014) and Vidovic et al. (2014) reported a decreasefor spray dried powder of cactus pear juice, amla juice, and Saturejamontana extract, respectively.

The results of the color analysis for powders are shown inTable 4. The color parameters of spray dried powders were signif-icantly affected by the concentration of maltodextrin. It was notedthat when the concentration of maltodextrin increased, lightnessincreased (P < 0.05), while the a⁄ values decreased (P < 0.05) indi-cating a tendency of the samples toward a green color. The b⁄ val-ues (P < 0.05) also decreased; however, they showed positivevalues, indicating a tendency toward a yellow color. Thus, it waspossible to note a strong protective effect of microencapsulationwith maltodextrin against heat during the spray drying process.Jafari et al. (2008) reported that wall materials are physical obsta-cles which can decrease the effects of oxygen, light, heat and mois-ture on microencapsulated ingredients.

The thermal behavior of the microcapsules can be noted in theDSC and TGA/DrTGA data shown in Fig. 4a and b, respectively. Thephase-change behaviors of samples were determined by DSC anal-ysis. The freeze concentrated fluid without maltodextrin curve(control) showed a sharp endothermic peak which is related tosolid–liquid melting peak (Tpeak = 175 �C and DHfusion = �93.77 J/g). For all microcapsules (M20, M30 and M40), the DSC curves alsoshowed a well-defined thermal event (an endothermic peak) corre-sponding to the melting point of microcapsules, which was notedat temperatures between 196 and 205 �C. This indicates that theencapsulated system showed that the melting point was shiftedto higher temperatures. Therefore, the melting point was increasedby the addition of maltodextrin to improve the thermal stability ofthe microcapsules. Sansone et al. (2011) related a similar behaviorin samples of fadogia microencapsulated with maltodextrin andmaltodextrin/pectin.

The thermal degradation behaviors of the microcapsules weredetected by TGA. Two representative stages were differentiatedby using the analysis of the thermogravimetric curves (Fig. 4b).The first significant weight loss is observed for moister lossbetween 30 and 105 �C. Above this temperature range a pro-nounced mass loss that corresponds to the decomposition processof samples was observed in TGA/DrTGA curves after 200 �C forM20, M30 and M40 and after 130 �C for the control samples. Thus,the inserted figure in Fig. 4b (DrTGA) curves indicate that micro-

Fm(Cmm

capsules has a higher thermogravimetric stability than the controlsample, which shows a higher temperature to initiate the thermaldecomposition step. Therefore, TGA analysis indicate that the addi-tion of maltodextrin has higher thermogravimetric stability thanthe control sample. According to Pereira et al. (2009), the loss ofmass in these materials among this temperature range can beunderstood as a possible degradation or thermal decompositionof one or more components (polysaccharides) and their subse-quent volatilization.

3.3. Storage stability

The protective effect of maltodextrin on the phenolic com-pounds of the microcapsules is shown in Fig. 5, where it is possibleto note that the M20, M30 and M40 samples were more stable thanthe control. Çam et al. (2014) reported that microcapsules pro-duced with maltodextrin were more stable than non-encapsulatedphenolic powder obtained by spray drying without coating mate-rial and stored at 4 �C. The increase in the total phenolic contentin all microcapsules may be a result of the polyphenols formationduring storage. The same behavior was observed by Saénz et al.(2009) and Bakowska-Barczk and Kolodziejczyk (2011), who foundrecoveries and formation of polyphenols as a consequence of the

Fig. 5. Storage stability of control and microcapsules at 4 �C during 45 days. Valuesrepresent the mean ± standard deviation (). Total phenolic content was based onFolin–Ciocalteu assay. Different letters after mean values indicate significantdifferences among the storage periods of samples (P < 0.05). Control (spray driedCF3 without addition of maltodextrin), M20 (CF3 microencapsulated by spraydrying with 20% of maltodextrin), M30 (CF3 microencapsulated by spray dryingwith 30% of maltodextrin), and M40 (CF3 microencapsulated by spray drying with40% of maltodextrin).

G.L. Nunes et al. / Journal of Food Engineering 151 (2015) 60–68 67

hydrolysis of cactus pear and black currant polyphenol conjugates,respectively.

4. Conclusions

It was possible to verify an enhancement of the total phenoliccontent and antioxidant activity of mate leaves aqueous extractthrough freeze concentration. The highest result for process effi-ciency was noted in the third freeze concentration stage, whoseconcentrated fluid (CF3) was used in the microencapsulation byspray drying. The microcapsules produced with 30% and 40% ofmaltodextrin showed the highest phenolic compounds microen-capsulated yield. Microencapsulation of polyphenols from CF3with maltodextrin successfully reduced polyphenol degradationduring spray drying. After spray drying, the control sample showedmore deformed shape than the microcapsules. However, themicrocapsules showed a higher particle size. The addition of mal-todextrin decreased the moisture content, water activity andhygroscopicity, while it increased the time required for the pow-ders to dissolve the microcapsules in water. The color parametersof spray dried powders were affected by maltodextrin concentra-tion, resulting in a protective effect of the microcapsules againstheat during spray drying. The results of the thermoanalyses sug-gest an increase in the stability of the microcapsules. Finally, find-ings from this present study indicate that microencapsulationusing maltodextrin better preserved polyphenol compounds ofmate extract during the spray drying process and increased theirstability during storage.

Acknowledgments

The authors thank the CNPq/Brazil - 471491/2012-8 (ConselhoNacional de Desenvolvimento Científico e Tecnológico) for thefinancial support, the CAPES/Brazil (Coordenação de Aperfeiçoa-mento de Pessoal de Nível Superior) for the scholarship, and alsoto the Universidade Federal de Santa Catarina (UFSC), especiallyto research supported by LCME-UFSC, such as scanning electronmicroscopy (SEM).

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