Effect of microencapsulation by spray drying on cocoa aroma compounds and physicochemical characterisation of microencapsulates

Effect of microencapsulation by spray drying on cocoa aroma compounds and physicochemical characterisation of microencapsulates

    Effect of microencapsulation by spray drying on cocoa aroma compounds and physicochemical characterisation of microencapsulates Zain ...

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    Effect of microencapsulation by spray drying on cocoa aroma compounds and physicochemical characterisation of microencapsulates Zain Sanchez-Reinoso, Coralia Osorio, Anibal Herrera PII: DOI: Reference:

S0032-5910(17)30440-0 doi:10.1016/j.powtec.2017.05.040 PTEC 12566

To appear in:

Powder Technology

Received date: Revised date: Accepted date:

23 February 2017 27 April 2017 21 May 2017

Please cite this article as: Zain Sanchez-Reinoso, Coralia Osorio, Anibal Herrera, Effect of microencapsulation by spray drying on cocoa aroma compounds and physicochemical characterisation of microencapsulates, Powder Technology (2017), doi:10.1016/j.powtec.2017.05.040

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ACCEPTED MANUSCRIPT Effect of microencapsulation by spray drying on cocoa aroma compounds and

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physicochemical characterisation of microencapsulates

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Zain Sanchez-Reinosoa, Coralia Osoriob, Anibal Herrerac

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a. Masters in Food Science and Technology, Agronomy Department, National University of

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Colombia, Universidad Nacional de Colombia, Bogotá, Colombia b. Departamento de Química, Universidad Nacional de Colombia, AA 14490 Bogotá, Colombia

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c. Post Harvest Laboratory, Agronomy Department, National University of Colombia,

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Universidad Nacional de Colombia, Bogotá, Colombia



Corresponding author at: Cra 30 Calle 45 Ciudad Universitaria, Agronomy. Department, National University of Colombia, Bogota, Colombia. Tel.: +57 3165100x19205; fax: +57 19206. E-mail address: [email protected] (A. Herrera).

ACCEPTED MANUSCRIPT ABSTRACT In this study the effect of microencapsulation parameters by spray drying on protecting volatiles

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of cocoa liquor, by employing Maltodextrin (MD) and Hi-Cap 100 (HC) as encapsulating

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materials, was evaluated. The feed solution were prepared in proportions of 3:1 and 2:1 w/w (wall:core) and drying at 150, 180 and 210 °C. The microencapsulates were evaluated in terms of

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yield, moisture, water activity, tapped density, rehydration properties and color. The morphology

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and size of the microcapsules were determined by SEM and aroma retention was evaluated by using HS-SPME and subsequent GC-MS analyses. The yield values were between 32.65 and 58.77

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%, being higher for encapsulated with HC. The microencapsulated powders showed moisture values between 1.05 – 4.00 % dry basis and low water activity values, among 0.052 and 0.269,

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what make them appropriate for their use in the food industry. The microencapsulated powders

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with HC showed semispherical particles, smooth surfaces, and few deformations. In contrast, those

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obtained with MD showed a high number of surface irregularities (folds, shrinkage, or dents). Microencapsulted powders obtained with HC allowed a higher retention of cocoa aroma (22.6 – 32.5 %), while MD solids showed lower values, between 12.1 – 19.2 %. The major aroma retention was obtained with HC in 2:1 ratio and drying temperature of 210 °C. However, sensory analyses results showed preference by the microencapsulated with MD, 2:1 ratio and 210 °C, which exhibited similar characteristics to chocolaty drink when it was applied to 20 % (w/w) in whole milk as a milk modifier.

Keywords: Cocoa liquor, volatile retention, SEM, encapsulant, FTIR analysis, particle size.

ACCEPTED MANUSCRIPT 1. Introduction The cocoa fruits (Theobroma cacao L.) are known for their variety of products exhibiting

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pleasant and desirable sensory properties (aroma and flavor). This is the main ingredient for the

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manufacture of chocolate and it is an important commodity in the world whose demand has significantly increased [1]. The cocoa tree is native to the upper Amazon basin, specifically Peru,

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Ecuador, Brazil, and Colombia headwaters [2]. Colombia cocoa is considered a great commercial

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interest product because it has been recognized by the International Cocoa Organization as fine flavor cocoa [3]. The specific characteristics of cocoa aroma and flavor are dependent of many

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factors such as, the bean genotype, environmental conditions, farming practices, postharvest processing, and the manufacturing stages [1, 4]. The cocoa aroma is a complex mixture of volatile

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compounds, from which have been identified more than 100 different odor-active volatiles; mainly,

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alcohols, carboxylic acids, aldehydes, ketones, esters, and pyrazines [1, 5]. The pyrazines are the

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main class of heterocyclic volatiles and the key odor components of cocoa aroma [1]. However, the different stages of processing can further loss of the cocoa aroma compounds due to its chemical nature, which exhibits relatively low boiling points and hence a fast evaporation [6]. To this regard, the aroma can be encapsulated to improve its stability in the final product and during the processing, as well as improve its handling and controlled release of aroma [7]. Therefore, the preservation of aroma compounds has attracted great attention in the recent decades, particularly by using microencapsulation technologies [6]. The microencapsulation process by spray drying is the most often used for the production of aromas and flavors [6-8]. This technique is used to trap labile compounds in a support material, which protects them from evaporation, degradation and production of off-flavors during storage [9]. However, the microencapsulation by spray drying of volatile compounds has a difficult

ACCEPTED MANUSCRIPT challenge since it is necessary to remove water without loss of aroma components during the processing [10].

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Thus, the objective of the present work was evaluated the effect of microencapsulation by spray

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drying of cocoa liquor with two different encapsulants (MD and HC), with the aim of preserving

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volatile aroma compounds.

Materials

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2.1.

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2. Material and methods

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Cocoa liquor (Theobroma cacao L.) supplied by Casa Luker S.A. (Bogota, Colombia) was used

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as core material. This consisted of a cocoa beans mixture of two different Colombian's regions (80

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% beans from Santander and 20 % beans from Huila), which was roasted at 160 °C. It presented a moisture content of 0.31±0.09 % in dry basis and 53.07±0.38 % of fat. The wall materials used were Maltodextrin 10DE and the modified starch Hi-Cap 100, supplied by Ingredion Colombia S.A. (Cali, Colombia). Sodium caseinate was used as emulsifier (Tecnas S.A., Bogota Colombia).

2.2.

Experimental design

A completely randomized designs for each encapsulant (MD and HC) were used to evaluate the effect of two ratios of wall:core materials (2:1 and 3:1) and three drying temperatures (150, 180 and 210 °C). Each treatment was carried out by triplicate and the results were analysed by using ANOVA and Tukey’s test (P<0.05) with the statistical software STATGRAPHICS Centurion XVI (16.1.03).

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Preparation of emulsions and spray drying process

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2.3.

The emulsions were prepared in ratios of 2:1 and 3:1 wall material:cocoa liquor, as follows: the

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wall material was dissolved in distilled water at a ratio of 20 % (w/w), followed to adding sodium

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caseinate in a constant ratio of 1 % (w/w) of the total emulsion. This concentration of emulsifier

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was determined by preliminary assays. The cocoa liquor was melted at 50 °C and mixed with the aqueous solution of wall material. The mixture was homogenised at 11200 rpm for 5min by using

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an ULTRA-TURRAX T18 basic (IKA WERKE, Staufen, Germany). The spray drying was performed on a Mini Spray Dryer Büchi B-290 (Büchi Labortechnik AG,

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Flawil, Switzerland). Compressed air at 6 bar and a spray nozzle 0.7 mm internal diameter were

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employed. The volumetric feed flow, volumetric air flow for atomization and the volumetric flow

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of air for drying, were programmed to 4.5 mL/min, 357 L/h and 32 m3/h, respectively. These conditions were determined by preliminary experiments and they were constant for all the analysis, varying only the drying temperature according to the experimental design.

2.4.

Powder characterisation

2.4.1. Process yield The process yield of spray drying in each case was determined according to Sun-Waterhouse et al. [11]. This parameter was calculated as the ratio between the weight of powder obtained and the weight of feeding mixture (dry basis), as follows: 𝑊

𝑌𝑖𝑒𝑙𝑑 (%) = ( 𝑊𝑀𝐸 ) ∙ 100 𝐹

(1)

ACCEPTED MANUSCRIPT Where WME is the weight of the microencapsulated in dry basis and WF is the weight of the

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feeding mixture in dry basis.

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2.4.2. Moisture and water activity

The moisture content was determined gravimetrically by drying the powder at 105 °C to

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constant weight, and reported as the percentage of weight loss before and after drying [12]. The

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water activity of the samples was measured with a HygroLab C1 (Rotronic AG, Bassersdorf,

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Switzerland).

2.4.3. Tapped density

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Tapped density was determined according to Fernandes et al. [13]. Approximately 5 g of each

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powder were placed in a 25 mL graduated cylinder. Then the cylinder was tapped repeatedly on a

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hard surface, lifted and dropped the cylinder under its own weight until the powder did not present a difference in the occupied volume. The bulk density was calculated by dividing the weight of powder on the final volume occupied by that of the powder in the cylinder (g/cm3).

2.4.4. Hygroscopicity

The hygroscopicity was determined according to the methodology used by Fernandes et al. [13], with some modifications. Approximately 1 g of each microencapsulated were placed in plastic Petri dishes of 55 mm on diameter and these were kept for a week in a chamber with controlled atmosphere MLR-351H (Sanyo, Bensenville, Illinois, EE.UU.) at 75 % RH and 25 °C. Finally, the samples were weighed and the hygroscopicity was determined as the weight in grams of absorbed moisture per 100g dry solids (g/100g).

ACCEPTED MANUSCRIPT 2.4.5. Water solubility index (WSI) and water absorption index (WAI) The WSI and WAI were determined by adapting the method described by Paini et al. [14]. An

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amount of ~1 g microencapsulated were dissolved in 12 mL of distilled water. Then, the samples

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were incubated in a Lab-line Imperial III water bath (Lab-Line Instruments, Inc., Melrose Park, III, USA) at 30 °C for 30 min and finally centrifuged at 2090 g for 15 min. The supernatant was dried

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in petri dishes at 105 °C to constant weight. WSI and WAI were calculated according to Eq. (2)

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and Eq. (3).

(2)

𝑊𝐴𝐼 = 𝑃𝑊 ⁄𝐷𝑊𝑝𝑎𝑟𝑡

(3)

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𝑊𝑆𝐼 = 𝐷𝑊𝑠𝑢𝑝 ⁄𝐷𝑊𝑝𝑎𝑟𝑡 × 100

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Where DWsup is the dry weight of the supernatant, DWpart is the initial weight of the

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microencapsulated dry basis and PW is the weight of sediment after centrifugation.

2.4.6. Color parameters

The color of microencapsulated cocoa powders was measured with a spectrophotometer ColorQuest XE (Hunter Associates Laboratory Inc., Reston, VA, USA). The color measurements were performed in triplicate with five readings for each sample. Additionally to the CIE L*a*b* coordinates (D65, 10°), the parameters of chroma (C*ab ) and hue (hab) were calculated according to Eq. (4) and Eq. (5): ∗ 𝐶𝑎𝑏 = [(𝑎∗ )2 + (𝑏 ∗ )2 ]1⁄2 ∗

ℎ𝑎𝑏 = 𝑡𝑎𝑛−1 (𝑏 ⁄𝑎∗ )

(4) (5)

ACCEPTED MANUSCRIPT 2.5.

Morphology and size particle

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The morphology of the microcapsules was observed in a scanning electron microscope Quanta 200 (FEI, Hillsboro, OR, USA) operated at low vacuum of 2×10-2 torr, 25 Kv and using secondary

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electrons. The dry powders were set on carbon tape and a metallic gold-palladium coating was

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applied prior to the observation. On the other hand, the particle size was determined by measuring

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the diameter of 300 particles of images obtained by SEM at a magnitude of 1000×, using the image

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analysis software ImageJ (1.49v).

Analysis of aroma compounds by gas chromatography-olfactometry (GC-O) and gas

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chromatography–mass spectrometry (GC-MS)

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The estimation of the effect of spray drying on protection aroma volatile compounds was determined according to Her et al. [15], which was calculated as the amount of each compound determined from the area under the GC chromatogram before and after to spray drying process. The identification of odour-active compounds was carried out only on those that were detected by gas chromatography coupled to olfactometry (GC-O). The volatiles were extracted by headspace–solid phase microextraction (HS-SPME), using a divinylbenzene/carboxen/polydimethylsiloxane

(DVB/CAR/PDMS,

50/30

µm,

Supelco,

Bellefonte, PA, USA) fiber. The conditions were: 15 min equilibrium at 60 °C, with a 30 min of fiber exposure at the same temperature and under magnetic stirring; the desorption time was 5 min in the injection port at 250 °C [16]. Reconstituted solutions of 1 g of microencapsulated were prepared in 2 mL of distilled water [17].

ACCEPTED MANUSCRIPT The GC-O analysis was performed on a gas chromatograph HP 5890 serie II (Hewlett-Packard, Wilmington, DE, USA), by using a TR-FFAP capillary column (Thermo, 30 m × 0.32 mm di, 0.25

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µm film thickness), equipped with FID and operated in splitless mode. The injection port was set

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at 250 °C and Helium was used as carrier gas with a flow of 1.2 mL/min. The column oven was programmed from 40 °C by 1 min, increasing to 180 °C at 6 °C/min, then 12 °C/min to 230 °C and

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held it for 5 min. The end of the capillaries were connected to a deactivated Y-shaped glass splitter

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(Chromatographie Handel Mueller, Fridolfing, Germany), which divides the effluent into two equal parts, one for FID and the other for heated sniffing port through deactivated fused silica

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capillaries.

The samples were also analysed by GC-MS in a gas chromatograph Agilent 7890B (Agilent

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Technologies, Palo Alto, CA, USA) equipped 5977A mass spectrometer (30–350 m/z, with

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electron energy of 70 eV) and operated under the same conditions used for the GC-O analysis.

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Odour-active volatiles were identified by comparing the mass spectra as well as the linear retention index (Kovats) with those in the database NIST/EPA/NIH Mass Spectral Library 2014 (2.2).

2.7.

Sensory evaluation

Sensory analysis was performed on the premises of Casa Luker S.A. (Bogota, Colombia), with a trained panel in sensory evaluation of cocoa products, consisting of seven judges of both sexes (25–30 years). The microencapsulated cocoa powders dissolved in water to 1% were evaluated by ranking test according to literature (NTC 3930) [18]. These analyses were performed during three sessions: the first and second sessions evaluated six samples each and the third evaluated four samples exhibiting the highest aroma intensity, which were selected according the results obtained during the previous sessions. Additionally, a quantitative descriptive analysis was performed to

ACCEPTED MANUSCRIPT evaluate its potential use as milk modifier. The microencapsulate selected was dissolved in whole milk purchased commercially at three different concentrations (10, 15 and 20 % w/v) and those

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were placed in porcelain vessels just before to being the evaluation. The assessors were asked to

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evaluate the intensity of seven descriptive sensory attributes (cocoa aroma, cocoa flavor, dairy flavor, bitter, creaminess, color, and overall impression) using a linear scale ranging from 0 (not

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FTIR analysis

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2.8.

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intense) to 10 (very intense).

The analysis of Fourier Transform Infrared Spectroscopy (FTIR) was used to confirm the

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presence of the cocoa liquor in the microencapsulate selected through sensory evaluation. The

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spectra of cocoa liquor, the pure wall material and the microencapsulated powder were recorded

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on a FT/IR-4100 spectrometer (JASCO Corporation, Tokyo, Japan). The spectra were obtained using the potassium bromide disc method with KBr at 99 %. The measurements were performed at 18 °C, with a resolution of 4 cm-1 and a scanning speed of 2 mm sec-1. The results were expressed as absorbance in a range of 4000-400 cm-1.

3. Results and discussion

3.1.

Process yield

The yield of microencapsulation process was mainly affected by the wall material (Tables 1 and 2), being higher when Hi-Cap was used. The process yield varied in a range from 32.65 to 58.77 %, obtaining the highest value in the treatment HC-3:1-210°C and lowest with MD-2:1-150°C.

ACCEPTED MANUSCRIPT This is because non-sticky food materials can be easily spray dried and the final powder remains free flowing, while sticky foods generally may be transformed into agglomerates in the dryer

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chamber, which leads to operating problems and low product yield [19]. On the other hand, the

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wall material:core ratio and drying temperature also affected the process yield. A higher content of wall material can enhance the suitable entrapment of the core material, reducing its amount onto

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the microcapsule surface and in consequence the stickiness of the particles in the drying chamber.

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Moreover, a lower value of process yield has been related to a greater amount of powder stuck to drying chamber [7]. This behavior has been reported by Janiszewska et al. [20], who found that as

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far as the lemon aroma (oily phase) increased, the particle sticking also increased and hence the process yield decreased. On the other hand, drying temperature had a positive effect on the process

Physical powder characterisation

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3.2.

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yield, which increased as far as the drying temperature increased, in all of the treatments.

Moisture and water activity are important parameters in the organoleptic quality and shelf life of the powders, because high humidity can cause problems during storage by the adhesion between the particles, clumping, and possible oxidation of the encapsulated material [13]. The microencapsulated cocoa powders had a moisture content between 1.05 – 4.00 % dry basis (Table 1). The moisture values was below the minimum specifications (3 – 4 %) to avoid microbial spoilage in dried powders used in food industry [21]. These values are similar to those found in rosemary essential oil (0.17 – 3.87 %) [13], for lemon aroma encapsulated (2.5 – 5.2 %) [20], coffee essential oil microencapsulated (0.76 – 3.23 %) [8], and tangerine essential oil microencapsulated (1.96 – 2.54 %) [22]. In general, the moisture content and water activity were closely related with the cocoa liquor content and the drying temperature. Previous studies have reported a linear

ACCEPTED MANUSCRIPT relationship between the inclusion of aroma and moisture content, which suggested that the increase of liposoluble aroma concentrations causes a decrease in the water content of

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microcapsules [23, 24]. In the same way, as the cocoa liquor increased in the feeding solution,

decreased in all the microencapsulated cocoa powders.

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hence higher lipid fraction due to high content of cocoa butter in cocoa liquor, the moisture content

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The bulk tapped density is an important parameter for handling powders during storage since

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low values can involve large air inclusion which could result in oxidation processes [25]. The tapped density of microencapsulates varied in a range from 0.514 to 0.694 g/cm3. These values

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were higher than encapsulated fish oil (0.248 – 0.374 g/cm3) [26] and microencapsulates of flaxseed oil (0.332 – 0.387 g/cm3) [27], but lower than the microencapsulates of olive oil which

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varied from 0.403 to 0.761 g/cm3 [28].

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The microencapsulated cocoa powders obtained with Hi-Cap showed higher tapped density than

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those obtained with maltodextrin. This behavior can be attributed to a higher molecular weight of the Hi-Cap in comparison to maltodextrins, which can make a better ordering of the particles, thus occupying less space [29]. Additionally, higher drying temperatures generated lower tapped density. Similar results have been reported by Aghbashlo et al. [26] who evaluated the microencapsulation of fish oil with dairy wall materials, finding that a variation of the drying temperature from 140 to 180 °C caused a decreasing of bulk tapped density. This behavior is related to the particle size, since a greater amount of smaller particles can reduce the spaces between the particles. Therefore, low values of tapped density are associated with higher drying temperature due to increased particle size [30-32]. Color is an important sensorial attribute of food materials since it influences the consumer choice and product acceptance. This property can be affected by different factors during the microencapsulation process. Tristimulus colorimetry evaluation of microencapsulated cocoa

ACCEPTED MANUSCRIPT powders showed that the brightness parameter decreased while the concentration of cocoa liquor increased (Table 1). It has been reported that the use of white wall materials in a greater ratio than

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the core, makes higher L* values [20]. Also, the cocoa liquor presents a brown color which can

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causes the decreasing of the brightness as their content increasing. The results obtained of color parameters were located in the first quadrant (+a*, +b*) for all the powders, such indicating a trend

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towards red and yellow colours, respectively. The coordinate a* was affected by the type of wall

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material and the cocoa liquor content. This was redder for powders obtained with MD and increased as the cocoa liquor increased. Similar behavior was observed by b* parameter and HC samples.

Rehydration properties

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The samples showed higher yellow colour when the core material content increased.

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The rehydration properties of microencapsulated cocoa powders were evaluated in terms of water solubility index (WSI), water absorption index (WAI) and hygroscopicity. The powders obtained with maltodextrin exhibited higher solubility than those obtained with HC, and consequently a lower WAI. The increased of cocoa liquor reduced the WSI, which can be attributed to the increasing of liposoluble fraction (hydrophobic), leading a greater level of insoluble components [14]. The results presented high WSI values and low IAA values for all microencapsulated cocoa powders, which are desirable characteristics for powders to be wetted quickly and completely without forming lumps during its dissolution [33]. As far as the hygroscopicity results are concerned, the microencapsulates obtained with Hi-Cap showed higher values than those obtained with MD. Moreover, a lower content of cocoa liquor, and hence lower fat content, made the water absorption increases in the powders. This behavior was similar to that reported by Frascareli et al. [8] for coffee oil microencapsulated. The

ACCEPTED MANUSCRIPT hygroscopicity results varied in a range from 7.33 to 12.58 g/100g, being low in comparison to that reported for microencapsulated pigments of amaranthus (44.6 – 49.5 g/100g) [32], but higher than

Morphology of powders

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3.4.

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the rapeseed extract microencapsulated (4.0 and 6.7 g/100g) [34].

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The changes in shape and size of the microparticles vary along the spray drying process and these mainly depend on the moisture content of the fed material and the drying temperature during

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the operation [35]. Fig. 1 shows the SEM images and particle size distribution behavior of the microencapsulated cocoa powders obtained with MD and HC at the lowest (150 °C) and at the

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highest (210 °C) drying temperature evaluated.

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The level of inclusion of core material did not present a noticeable difference in the surface

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characteristics of the microcapsules. Microparticles made with the modified starch had a higher number of semispherical morphology, smooth, and light surface deformations (Figs. 1c and 1d). This is a desirable characteristic of the microcapsules because the integrality of the microparticle surface is important to ensure a good core retention and lower permeability of water vapor and oxygen [21, 36, 37]. In contrast, those obtained with MD (Figs. 1a, b) presented more frequency of particles with greater deformations and irregular surfaces (folds), similar to those reported by Tonon et al. [27]. The presence of depressions on the surface of the microparticles have been associated to the shrinkage during drying and cooling [21, 36, 38]. These irregularities are closely related to the water evaporation rate during the spray drying process [39]. Pronounced deformations appear more frequently when the drying temperature is low, because the water diffusion is slower and a long time of drying produce further deformations, roughness (shrunken particles) and, the

ACCEPTED MANUSCRIPT collapse of the capsules (breaking) [35]. In contrast, high drying temperatures produce faster evaporation, which the subsequent formation of smoother surfaces [39, 40].

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The particle size distribution of powders are depicted in Fig. 1, showing the presence of different

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size particles that varied from 0 to 50 µm. It has reported that powders obtained by spray drying presents polydispersity of particle size in powders due to the lack of uniformity of the droplet size

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formed in the spray phase [21]. Nonetheless, all the treatments presented higher number of particles

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in the ranges of 5 – 10 µm and 10 – 15 µm, respectively. The particle size varied slightly between wall materials used and the increasing of drying temperature, finding particles with higher size in

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powders obtained with HC and the higher drying temperature (210 °C). However, these changes were not significant. Some studies have reported that high drying temperatures produce faster

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drying rates, which sets up an early surface structure that does not allow the particles to shrink [35,

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3.5.

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39, 41].

Aroma compounds retention

The GC-O analysis allowed to detect thirteen odour-active volatile compounds (Fig. 2) in the cocoa liquor employed as core material. These were mainly pyrazines, carboxylic acids, esters, among others, which exhibited the characteristic cocoa attributes such as, cocoa, chocolate, and sweet. The most abundant group of compounds were the pyrazines: 2-methylpyrazine, 2,5dimethyl

pyrazine,

2,3,5-trimethylpyrazine,

3-ethyl-2,5-dimethylpirazine,

2,3,5,6-

tetramethylpyrazine, and 3,5-diethyl-2-methyl pyrazine. Four of these pyrazines has been considered extremely important in the aroma cocoa [42]. The retention of odour-active volatile compounds of cocoa aroma in powders are presented in Table 3. As it can be seen, the recovery percentages were low for most compounds, with exception

ACCEPTED MANUSCRIPT of 2,5-dimethylpyrazine and linalool. The other compounds did not present recoveries higher to fifty percent. It was expectable that during the microencapsulation process, the loss of some volatile

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compounds occurs. Previous studies have reported that volatile retention with carbohydrate is

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independent of the relative volatility of aroma compounds, but it may increase with high volatile molecular weight of them [43].

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The 3-methylbutyl acetate, 3-methyl butanoic, acetophenon, and 2-phenylethyl acetate, were

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found only in some of the microencapsulated obtained at higher temperatures. Chin et al. [44] evaluated the behavior of volatile compounds of durian pulp prior and post to the drying. In their

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study, they reported that spray drying generated a loss of volatiles between 97.7 and 99.1 %. On the other hand, the total aroma retained in the microencapsulates was determined as the sum

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of area under the peaks of the thirteen aroma compounds identified by GC-O (Fig. 2b) [45]. The

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results varied between 12.1 – 32.5 %, presenting a slight increasing in aroma retention as far the

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drying temperature increased (Table 3). Some authors mentioned that aroma retention during spray drying is dependent on the phenomenon of selective dissemination [21]. This phenomenon can only occur during spray drying when a selective layer is generated, which allows water diffusion but avoids the diffusion of aroma molecules [44]. In this study, the highest retention of volatile compounds (32.5 %) was obtained with Hi-Cap as wall material, at wall material:core ratio of 2:1 and the highest drying temperature (210 °C). Janiszewska et al. [45] reported a similar aroma retention with a formulation of maltodextrin:arabic gum(3:1) to microencapsulate rosemary aroma (about 30 %). However, they achieved a 60% aroma retention using only arabic gum.

ACCEPTED MANUSCRIPT 3.6.

Sensory evaluation

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The results showed significant differences between samples. The highest scores were exhibited by microencapsulated cocoa powders obtained at high drying temperature (210°C) and low content

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of wall material (Table 4). The MD-2:1-180 and MD-2:1-210 samples did not significant difference

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in the first session. In the same way, the HC-2:1-180 and HC-2:1-210 samples did not significant

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difference in the second session. These four samples were selected preliminarily, because they presented the highest punctuation. They were evaluated in a final session and Friedman's test

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indicated that there was a significant difference between the microencapsulated cocoa powders (Table 4). In spite of the three samples with the highest values of intensity did not present

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significant difference between them, the treatment with the highest punctuation (intensity) was

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210.

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selected as the treatment with the best sensorial characteristics, which corresponded to MD-2:1-

The selected microencapsulate was applied as milk modifier at three concentrations (10, 15 and 20 %). Fig. 3 shows the sensory profiles for each microencapsulate inclusions. The samples only presented significant difference for the color attribute (p<0.05). However, despite the samples did not show significant differences for most of the attributes evaluated, the increase of microencapsulated concentration produced an increase of the color, overall aroma and impression, and the specific notes to cocoa flavor and bitterness. In contrast, a microencapsulated concentration increase produced a lower perception of dairy flavor. According to these results, the sample with the highest concentration (20 %) presented the highest intensity of the attributes, followed by 15 % and 10 % concentrations, respectively. Despite panelists selected 20% ME sample for exhibiting the best cocoa flavor, they also mentioned that the bitter taste was more intense than in the chocolaty drinks commercially found. This fact suggests that high concentrations of

ACCEPTED MANUSCRIPT microencapsulates are not suitable for the food product development since it can be produce undesirable sensory properties as well as generate higher production cost. According to this fact, it

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can be concluded that concentrations between 15 and 20 % of the ME-2:1-210 could generate

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FTIR analysis

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3.7.

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similar sensory characteristics for the chocolaty drink.

The microencapsulated powder selected according to the best sensory characteristics was

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analysed by FTIR spectroscopy in order to verify the presence of the cocoa liquor in the microparticles. Fig. 4 depicts the spectra corresponding to cocoa liquor, wall material (MD) and

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the microencapsulate selected (MD-2:1-210). The spectrum obtained for the cocoa liquor (Fig. 4a),

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presented signals at 3003, 2921, 2852 and 1737, 1656 cm-1. The signal at 3003 cm-1 can be

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associated to the stretching vibration of the cis olefinic double bond [46]. In a similar way, bands at 2921 and 2852 cm-1 resulting from the methylene asymmetrical and symmetrical vibrations, respectively [46, 47]. The band at 1737 cm-1 corresponds to a stretching vibration of C=O group of triglycerides, and the C=C stretching of unconjugated olefins usually is detected as a small band at 1656 cm-1 [46].

On the other hand, the spectrum of pure maltodextrin presented peaks at 3425, 2920, 1640, 1457, 1371, 1159, 1083 and 1026 cm-1 (Fig. 4b). The absorption band observed at a wavelength of 3425 cm-1 is characteristic for hydroxyl (–OH) groups [39]. Other characteristic vibrations of a carbohydrate moiety were found at 1457 and 1371 cm-1, which are related to the C–H and CH3 bendings [48]. The bands at 1159 and 1083 cm-1 are caused by the stretching of C–O bond, whereas 1026 cm-1 signal corresponds to the angular deformation of the =CH and CH2 bands. These three bands are characteristic of groups found commonly in carbohydrates and before reported in

ACCEPTED MANUSCRIPT maltodextrin [49]. As it was observed in Fig. 4c, the spectra of the microencapsulated cocoa powder also showed peaks characteristic of cocoa liquor, thus confirming the presence of cocoa liquor into

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the polymeric matrix.

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4. Conclusion

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The microencapsulation parameters for production of cocoa flavoring by spray-drying were evaluated. The process yield varied between 32.65–58.77 %, which was higher for encapsulated

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with Hi-Cap as wall material. The obtained powders showed adequate moisture good rehydration properties for their use in food industry. The microencapsulated cocoa powders with Hi-Cap as

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wall material showed semispherical particles, smoother surfaces and fewer deformations. In

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contrast, those obtained with maltodextrin that presented surface irregularities (creases, or dents

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contractions) more often at low drying temperatures. The microencapsulated cocoa powders obtained with Hi-Cap as wall material exhibited higher cocoa aroma retention (22.6–32.5 %) in comparison to those prepared with maltodextrin, which was directly proportional to cocoa liquor content and drying temperature. However, the sensory analysis indicated a preference for the samples obtained with maltodextrin. According to the sensory analysis, the MD-2:1-210 treatment presented the best organoleptic characteristics according to the flavor intensity, which could be as used as milk modifier in a proportion between 15–20 %.

Acknowledgments

The authors thank the support of Ingredion Colombia S.A. and Casa Luker S.A. for the supply of raw materials and support in sensory analysis. Z. Sanchez-Reinoso thanks to Jardín Botánico José

ACCEPTED MANUSCRIPT Celestino Mutis and its programme "Estímulos a la Investigación Thomas van der Hammen" for its financial support, as well as the Instituto de Ciencia y Tecnología de Alimentos (ICTA) of the

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Universidad Nacional de Colombia.

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physicochemical properties of açai (Euterpe oleraceae Mart.) powder produced by spray drying,

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byproducts of the Bordo grape (Vitis labrusca), Food Bioprod. Process. 93 (2015) 39-50.

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[50] A.M. El-Sayed, The pherobase: database of pheromones and semiochemicals, http://www.pherobase.com/, 2016, (accessed 09.10.2016). [51] G. Budryn, E. Nebesny, J. Kula, T. Majda, W. Krysiak, HS-SPME/GC/MS profiles of convectively and microwave roasted Ivory Coast Robusta coffee brews, Czech J. Food Sci. 29 (2011) 151-160.

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ACCEPTED MANUSCRIPT [55] P. Wanakhachornkrai, S. Lertsiri, Comparison of determination method for volatile

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compounds in Thai soy sauce, Food Chem. 83 (2003) 619-629.

ACCEPTED MANUSCRIPT Fig. 1. Morphology (left) and particle size (right) of cocoa microencapsulates: wall materialtemperature, MD-150 (a), MD-210 (b), HC-150 (c), and HC-210 (d).

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Fig. 2. Chromatograms for odor active volatile of cocoa liquor (a) and HC-210 microencapsulate

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(b). Numbers on the chromatograms correspond to those in the Table 3. The chromatograms for all microencapsulates were qualitative and quantitative similar to figure b.

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Fig. 3. Sensory profiles of milk beverages enriched with MD-2:1-210 microencapsulate in

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different concentrations.

Fig. 4. FTIR spectra of cocoa liquor (a), maltodextrin (b) and microencapsulate MD-2:1-210

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(Maltodextrin-wall material:core material relation-drying temperature).

ACCEPTED MANUSCRIPT

(a)

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20 µm

20 µm

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20 µm

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(b)

(c)

20 µm

(d)

Figure 1

ACCEPTED MANUSCRIPT

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(a)

Figure 2

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(b)

Figure 3

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ACCEPTED MANUSCRIPT

Figure 4

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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT Table 1. Physicochemical characterisation of cocoa microencapsulates obtained by spray-drying with maltodextrin. 3:1z 180 °C

74.0 ± 2.0

88.3 ± 2.1

0.162 ±

0.108 ±

0.052 ±

0.027a

0.023ab

Moisture (%,dry

2.20 ±

1.99 ±

basis)

0.32a

0.32ab

36.28 ±

41.49 ±

1.31cd

210 °C

87.0 ± 2.0 106.5 ± 1.6 0.073 ±

0.067 ±

0.007b

0.040a

0.017b

0.018b

1.47 ±

1.58 ±

1.08 ±

1.05 ±

0.15bc

0.35abc

0.15c

0.09c

51.19 ±

32.65 ±

35.79 ±

42.97 ±

2.60bc

2.98a

1.48d

2.59cd

2.06b

0.604 ±

0.591 ±

0.580 ±

0.623 ±

0.621 ±

0.609 ±

0.010ab

0.010ab

0.007b

0.007a

0.021a

0.015ab

82.69 ±

81.14 ±

75.81 ±

75.00 ±

73.85 ±

2.45a

2.47ab

1.30bc

2.57bc

2.75c

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1.46a

SC

0.156 ±

82.24 ±

WSI (%)

74.7 ± 2.1

180 °C

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ρT (g/cm3)

1.8

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Yield (%)

105.2 ±

150 °C

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Water activity

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Tout (°C)

210 °C

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150 °C

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Variable

2:1z

WAI (g/g dried

0.54 ±

0.54 ±

0.62 ±

0.68 ±

0.72 ±

0.90 ±

powder)

0.04b

0.08b

0.11ab

0.08ab

0.09ab

0.18a

Hygroscopicity

7.59 ±

8.43 ±

9.90 ±

7.33 ±

9.05 ±

9.42 ±

(%)

1.02b

1.05ab

0.15a

1.06b

0.35ab

0.45ab

75.54 ±

76.44 ±

77.01 ±

73.21 ±

72.56 ±

69.14 ±

1.05a

2.36a

0.62a

1.93ab

2.27ab

1.11b

5.66 ±

5.14 ±

5.00 ±

6.15 ±

6.09 ±

7.08 ±

0.36b

0.72b

0.16b

0.47ab

0.46ab

0.31a

14.01 ±

13.21 ±

12.89 ±

14.86 ±

14.51 ±

15.46 ±

0.27abc

1.24bc

0.26c

0.82ab

0.56abc

0.32a

15.11 ±

14.18 ±

13.83 ±

16.09 ±

15.74 ±

17.01 ±

0.38abc

1.42bc

0.29c

0.93ab

0.69abc

0.38a

1.19 ±

1.20 ±

1.20 ±

1.18 ±

1.17 ±

1.14 ±

0.02a

0.02a

0.01a

0.01ab

0.02ab

0.02b

L*

a*

b*

C*ab

h*ab

ACCEPTED MANUSCRIPT Means with different letters in the same row represent statistically significant differences according to Tukey’s test (p ≤ 0.05). z = wall material:core ratio. T out =

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outlet temperature. WSI = water solubility index. WAI = water absorption index.

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Table 2. Physicochemical characterisation of cocoa microencapsulates obtained by spray-drying with Hi-Cap. 3:1z 150 °C

180 °C

210 °C

105.5 ± 1.8

0.269 ± 0.025a 0.179 ± 0.031bc 0.130 ± 0.019c 0.212 ± 0.025ab 0.179 ± 0.179bc 0.118 ± 0.010c 1.98 ± 0.28c

1.20 ± 0.14e

2.81 ± 0.25b

1.79 ± 0.28cd

1.32 ± 0.07de

Yield (%)

41.67 ± 1.80c

47.64 ± 2.20bc

58.77 ± 2.06a

39.99 ± 1.22c

44.03 ± 1.09cd

48.94 ± 1.53b

ρT (g/cm3)

0.694 ± 0.008a 0.681 ± 0.036a

0.526 ± 0.027b 0.672 ± 0.022a

0.646 ± 0.054a

0.514 ± 0.008b

WSI (%)

79.20 ± 1.86a

79.63 ± 1.24a

75.82 ± 2.77ab

72.24 ± 1.07bc

74.02 ± 0.67b

68.18 ± 2.34c

0.77 ± 0.10c

0.79 ± 0.10bc

0.92 ± 0.04abc

0.95 ± 0.03ab

0.91 ± 0.01abc

1.08 ± 0.05a

Hygroscopicity (%)

9.89 ± 1.04bc

11.72 ± 0.84ab

12.58 ± 1.35a

9.32 ± 0.52c

9.65 ± 0.39bc

9.82 ± 0.28bc

L*

76.59 ± 0.23a

74.38 ± 0.72ab

72.77 ± 1.57bc

71.50 ± 0.91c

71.60 ± 0.75c

70.51 ± 0.45c

a*

5.76 ± 0.34b

6.44 ± 0.21ab

6.77 ± 0.37a

7.05 ± 0.17a

7.02 ± 0.15a

7.12 ± 0.21a

b*

13.66 ± 0.55b

14.54 ± 0.31ab

14.73 ± 0.46a

15.50 ± 0.28a

15.30 ± 0.33a

15.29 ± 0.28a

C*ab

14.82 ± 0.63a

15.90 ± 0.37ab

16.22 ± 0.58a

17.02 ± 0.32a

16.83 ± 0.36a

16.87 ± 0.34a

h*ab

1.17 ± 0.01a

1.15 ± 0.01b

1.14 ± 0.01b

1.14 ± 0.01b

1.14 ± 0.00b

1.14 ± 0.01b

powder)

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WAI (g/g dried

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basis)

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4.00 ± 0.15a

CE

87.6 ± 1.2

210 °C

Water activity

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75.3 ± 0.3

180 °C

74.3 ± 1.1

SC

106.5 ± 0.7

150 °C

Tout (°C)

Moisture (%, dry

88.8 ± 1.3

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Variable

2:1z

Means with different letters in the same row represent statistically significant differences according to Tukey’s test (p ≤ 0.05). z = wall material:core ratio. Tout = outlet temperature. WSI = water solubility index. WAI = water absorption index.

ACCEPTED MANUSCRIPT

Table 3. Odour-active volatile compounds identified by HS-SPME/GC-MS from microencapsulates of cocoa liquor. Percent of recoverya (%)

1129

2

2-methylpyrazine

1282

3

2,5-dimethylpyrazine

1340

4

2,3,5-trimethylpyrazine

1423

5

Acetic acid

1451

6

3-ethyl-2,5-dimethylpyrazine 1464

7

2,3,5,6-tetrametilpyrazine

8

3,5-diethyl-2-methylpyrazine 1530

9

Linalool

1557

10

3-methylbutanoic acid

1678

11

Acetophenon

1687

12

2-phenylethyl acetate

1848

13

2-acetylpyrrole

2006

1492

3:1

2:1

150 180 210

150 180 210

150 180 210

150 180 210

––– ––– –––

––– ––– 15.2

––– ––– 24.7

––– 13.3 26.0

14.8 15.1 21.3

17.1 20.2 18.2

25.0 38.6 23.7

43.3 26.8 23.6

50.3 83.6 82.5

44.0 71.8 79.4

75.8 52.5 81.9

61.3 84.4 89.8

Bitter chocolate

4.7

5.0

7.2

7.9 10.1 9.8

10.6 8.3

8.7

10.7 11.0 12.4

Acid

0.5

0.6

0.9

0.5

0.7

0.5

0.9

1.0

0.9

1.0

1.1

1.2

Chocolate

2.0

2.9

3.5

1.6

2.9

2.0

3.2

3.6

3.4

3.9

9.1

6.6

6.9

7.6

7.6

7.6

7.1

8.1

10.6 10.8 8.8

12.8 14.4 15.6

RI

2:1

SC

3-methylbutyl acetate

Hi-Cap 100

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1

Theo 1117 [50] 1285 [51] 1330 [51] 1406 [50] 1447 [50] 1477 [52] 1484 [53] 1521 [53] 1558 [50] 1661 [50] 1680 [54] 1821 [50] 2003 [55]

3:1

Rancid, fruity Corn Cocoa

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Exp

MD 10DE

Odor description

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Column FFAP

CE

Compound

Earthy

AC

No. Pico

PT

IK

Sweet

10.0 11.1 12.3

10.1 9.6

8.8

18.3 17.1 16.5

18.8 8.7 13.4

Floral

19.5 15.5 28.9

43.7 34.6 25.6

57.6 58.8 71.5

58.5 49.8 63.0

Paper

––– ––– –––

––– 2.3

3.8

––– ––– –––

––– 5.9

Rancid, bananalike

––– ––– –––

––– ––– 39.7

––– ––– –––

––– ––– –––

Floral

4.7

6.5

5.3

7.8

Woody

––– ––– –––

4.7

7.8

5.9

7.1

––– ––– –––

6.1

4.4

––– ––– –––

4.8

6.5

9.7

7.1 ––– 7.8

ACCEPTED MANUSCRIPT

12.1 13.2 17.6

16.4 18.0 19.2

22.6 23.3 23.7

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Total aroma retention (%)

27.1 27.3 32.5

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IK = Kovats retention index, Exp = Experimental retention index, Theo = theoretical retention index reported in literature and databases

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online. a Preservation effects (%) = (peak area before spray drying/peak area after spray drying) x 100 [15]. ––– Non-detected.

ACCEPTED MANUSCRIPT Table 4. Rank of odour and taste attributes obtained by Friedman test of cocoa microencapsulates (1% in water). Selected samplesz

Hi-Cap 100 samples

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Maltodextrin samples Friedman test

Sample*

Friedman test

Sample*

Friedman test

MD-3:1-150

6c

HC-3:1-150

12c

HC-2:1-180

6b

MD-3:1-180

17bc

HC-3:1-180

8c

HC-2:1-210

14ab

MD-3:1-210

22b

HC-3:1-210

19bc

MD-2:1-150

20b

HC-2:1-150

26ab

MD-2:1-180

26ab

HC-2:1-180

MD-2:1-210

35ª

HC-2:1-210

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Sample*

MD-2:1-180

19ª

MD-2:1-210

21ª

26ab

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35ª

*Sample description for MD (maltodextrin) and HC (Hi-Cap), wall material:core relation-drying Z

Selected samples during the previous sessions: two of maltodextrin samples and

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temperature.

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two of Hi-Cap 100 samples. Equal letters in a column means that there are no significant

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differences according to Friedman test (α = 0.05).

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ACCEPTED MANUSCRIPT

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Graphical abstract

ACCEPTED MANUSCRIPT Highlights Cocoa liquor was microencapsulated using maltodextrin and Hi-Cap 100.



Powders presented with good physical characteristics for handling and storage.



Microencapsulates with Hi-Cap showed the best cocoa aroma profile than those with

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Sensory evaluation showed a preference for microencapsulates obtained with maltodextrin.

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maltodextrin