Drying Technology: An International Journal BIXIN ...

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BIXIN POWDER PRODUCTION IN CONICAL SPOUTED BED UNITS a

a

a

M. L. Passos , L. S. Oliveira , A. S. Franca & G. Massarani

b

a

Department of Chemical Engineering , Universidade Federal de Minas Gerais , Belo Horizonte, MG, 30.160-030, Brazil b

Chemical Engineering Program/COPPE , Universidade Federal do Rio de Janeiro , Rio de Janeiro, RJ, 21.945-970, Brazil Published online: 27 Apr 1998.

To cite this article: M. L. Passos , L. S. Oliveira , A. S. Franca & G. Massarani (1998) BIXIN POWDER PRODUCTION IN CONICAL SPOUTED BED UNITS, Drying Technology: An International Journal, 16:9-10, 1855-1879, DOI: 10.1080/07373939808917500 To link to this article: http://dx.doi.org/10.1080/07373939808917500

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DRYING TECHNOLOGY. 16(9&10). 1855-1879 (1998)

BlXIN POWDER PRODUCTION IN CONICAL SPOUTED BED UNlTS

Downloaded by [Adriana S. Franca] at 07:43 30 July 2014

M. L. ~assosl,L. S. Oliveira', A. S. ~ r a n c aand ' G. Massarani

'

I . Depamnent of Chemical Engineering, Universidade Federal de Minas Gerais 30.160-030 - Belo Horizonte - MG. Brazil 2. Chemical Engineering ProgramICOPPE, Universidade Federal do Rio de Janeiro 2 1.945-970 - Rio de Janeiro RJ. Brazil

-

Keywords: annatto; color E160B; drying seeds; draft tube: particle attrition

ABSTRACT Recent work has demonstrated that the red carotenoid bixin is easily extracted from Hlxa orellana seeds by panicle attrition and impact rather than by solvent extraction. This technique may require a previous step for drying seeds at a safe temperature to preserve pigment quality. A spouted bed (SB) with a draft tube is the most appropriate equipment to process both seed drying and bixin extraction at low operational costs. Operational parameters of the SB unit are optimized as a function of the powder production rate. The maximum air inlet temperature for drying the seeds is also specified. A high performance liquid chromatography method has been developed for the semi-quantitative determination of bixin content in the powder produced. Results show that this SB unit can be more competitive than ball mill equipment.

1855 CapyrighlO 1998 by Marcel Dekkcr. Inc.

PASSOS ET AL. INTRODUCTION Different and varied hues of color are present in nature. These attract attention and identify products, which is the main reason why coloring is also used in industry. Interest and demand for natural colors have increased significantly in recent years due to consumer demands for natural products. Although natural colors have some limitations in comparison to synthetic ones Downloaded by [Adriana S. Franca] at 07:43 30 July 2014

(sensitivity to light, pH and heat: susceptibility to oxidation and lower pigment strength),they are preferred because of their lack of toxicity. The classic example is the coloring of cheddar cheese with annano (Freund et al., 1988). Annano is a natural reddish-yellow extract obtained from Bixa orellana seeds. The primary pigment is oil-soluble carotenoid bixin. This extract has been satisfactorily and safely used in the food, cosmetic and pharmaceutical industries. Product applications include cheese, ice cream, cereals, salad dressings, butter, snack foods, powder make-up and lipsticks, among others. Hixa orellana is a tropical shrub which grows quickly in Brazil, Peru, the Caribbean, India and other tropical countries. As shown in Figure I, its seeds are comprised of an "inner s e e d with a shelled kernel containing oils, waxy substances, mineral ash and some unknown compounds; a peel consisting of cellulose and tannins; and an outer cover containing pigments, moisture, cellulose, sugar and a small amount of oils. About 90% of the total pigments in this outer cover are red carotenoid bixin. The production of Hixa orellana seeds in Brazil has been increasing during the last ten years, partly because of interest on the international market (EMATER, 1994). This production is mostly from harvesting native groves, in which the majority of seed species present a low bixin content (about 2 to 3 %). Modem techniques for seed cultivation and harvesting have been introduced in some regions of Brazil in order to increase bixin content (up to 5 %).


BlXlN POWDER PRODUCTION

1857

FIGURE 1 - Photograph of B u a orellom seed. (Electronic Microscope, Cambridge - 250MK3)

Organic solvent extraction is traditionally used to remove bixin from the seed surface (Dendy, 1966). This process is quite expensive and requires several extraction steps to achieve the desired pigment content. In addition, other disadvantages such as low recovery of solvents, occurrence of thermal and oxidative degradation and limited use of extracted residues (Chao et al., 1991) have been pointed out in the literature. Since this process requires large investments for installation near plantations or in small cooperatives. seeds are usually transported long distances to industrial zones. The high transportation cost of these untreated seeds and the low percentage (2 to 3 %) of useful pigment extracted reduce the applicability of the organic solvent extraction process in Brazil. This is one reason why B. orellam seeds are normally exported or are

used to produce a condiment of lesser commercial value (colorau). Even with the

PASSOS ET AL.

1858

increase in seed production, Bmilian indusbies have to buy annano at a high price from other countries. Massarani et al. (1992) have proposed a new process to extract this pigment from seeds based on particle attrition and impact. This involves the use of simple equipment, such as a ball mill or a spouted bed, suitable for installation at plantations. This reduces operational costs for annano production. To apply this


mechanical extraction technique, seed moisture content must be low enough to assure detachment of the outer seed covering as powder. In most cases, seeds need to be dried at low temperatures (< 60 ' C ) to preserve pigment quality. As pointed out by McKeown and Mark (1962). bixin undergoes a series of isomerization and degradation reactions at high temperatures, resulting in a yellow product with little pigmentary value. High paicle attrition rates and safe seed drying temperatures can be simultaneously achieved in a conical spouted bed with a draft tube, as demonstrated by Massarani ct al. (1992). The bixin concentrate was obtained by sieving the powder produced and taking the fraction lower than 60 mesh (Tyler standard

sieve).

This

extract

presents

the

basic

requirements

for

commercialization as annano powder. A sample of the bixin extract obtained in the SB unit was used by a Brazilian buner and cheese producer to color cheeses. The results obtained were excellent, surpassing the wlor quality of the annano powder used in that industry. This confirms that mechanical extmction in a SB produces powder with high pigment contents at lower costs compared to that produced by the tmditional process. Moreover, the risk of product photochemical and oxidative degradation is eliminated in this mechanical extraction. since it is carried out in the absence of light and it is fast enough to prevent oxidative reactions. The issue of thermal degradation during processing is addressed in this work.

BIXIN POWDER PRODUCTION

1859

The objectives of this work are (i) to design the dimensions of the draft tube in the conical SB unit to maximize powder production; (ii) to estimate the inlet air temperature for drying seeds during the first operating hour; (iii) to describe the amount and characteristics of powder produced as a function of inlet airflow rate and operating time and (iv) to evaluate the degree of bixin thermal


degradation during processing of the seeds.

Figure 2 shows a schematic view of the experimental conical SB unit. The column was built of galvanized iron and had a conical base 0.474 m high with a 60" angle. An acrylic window in the cylindrical section permitted feeding of and observation of the operation of the spouting regime. This cylindrical section had a height of 1.OO m and an internal diameter of 0.60 m. A conical cover with an intemal angle of 130" was placed at the top of the column. A pipe with an internal diameter of 0.0524 m was used as the inlet air n o d e . Two cenmfugal blowers (Ayes Ltda.. LA-5031530 5HP Model), assembled in series, supplied air to the SB colwnn Draft tube insertion in the seed bed is illusbated in Figure 3. A Lapple cyclone was attached at the exit of the SB unit. This cyclone

(cylindrical section diameter of 0.15 m) was specially designed to collect the powder produced. The prediction of cut-size particle diameter (collection efficiency of 50 % ) was 3 pm for the range of airflow rates used in this work. The experimental program was divided into three main steps addressing the following objectives: ( I ) experimental optimization of draft tube dimensions as a function of powder production rate; (2) prediction of a safe inlet air temperature for drying seeds, and (3) characterization of the quality of the powder produced as a function of operational parameters in the optimized draft-tube SB unit. These three experimental steps were developed by Ezequias et al. (1994). Menezes et

PASSOS ET AL

air


spouted bed cohunn

FIGURE 2 - Schematic view of experimental spouted bed unit.

-

FIGURE 3 Draft tube insertion.

BlXIN POWDER PRODUCTION

1861

al. (1995) and Vilela et al. (1996). respectively. Furthermore, to complement the second step, Freitas (1996) developed a model to predict batch drying rate in conical spouted beds of grains. This model combines air-particle flow with the liquid diffusion theory to describe the increase in seed temperature with drying operating time for any inlet air condition above the minimum spouting. In addition to the third step, a high performance liquid chromatography (HPLC)


methodology has been developed to semiquantitatively determine the bixin content in the powder produced. Characterization of Hixa orcllana Seeds Properties of H. orellanu seeds used in this work are presented in Table 1 These seeds were from several plantations in the state of Minas Gerais (Southeast region of Brazil). Physical properties were measured using procedures described by Freitas (1996). The initial moisture content, mo,was determined by weighing samples dried over 24 h in an oven at 105 "C. The heat of desorption, L,,, was calculated from the H. urclluno seed sorption curves using the procedure developed by Freitas (1996). The heat capacity of the seeds, c, (=2147 Jlkg K), was estimated from data in the literature (see Freitas, 1996). These two parameters were necessary for the drying calculations. Pressure Drop and Airtlow Rate Measurements Airflow rates were controlled by a by-pass gate valve (Figure 2) and measured by an orifice plate system (Transcontrol Ltda.). Two static taps, located at the inlet nozzle pipe and at the top of the conical column, were connected to water manometers. This system registered the total pressure drop across the bed of seeds and the gauge pressure at the inlet nozzle. The spout pressure drop, AP, was obtained using the procedure proposed by Mathur and Epstein (1974). The minimum spouting condition was determined by plotting spout pressure drop as a

1862

PASSOS ET AL.

TABLE 1 - Properties of Hixu Orellona Seeds. 1 Measured Values 1 Standard Deviation

Propertie

1

( S D )

P

0.0034 0.00015 0.8~1~21 0.10 @ (-) I 0.93 "' 1426 "I 100 P. (kglmJ)at mo 127?~'" 35 0.415 0.009 Smf(-) 0.103":~' 0.004 mo (dry basis) 0.128 "' 0.005 2.07~10' 2.2x106 4 (Jk) (I); (2); (3) seeds used in the 1st. 2nd and 3rd experimental steps, respectively.


d,(m)

function of inlet airflow rate. The point at which the spout collapses defines the minimum spouting airflow rate, . ,V

The minimum spouting pressure drop, AP,,,

is the constant value obtained during the spout regime. Optimization of Draft Tube Dimensions Massarani et al. (1992) have shown that a smaller draft tube entrainment length (h,) leads to higher annatto powder production rates. In addition, production rate rose as the amount of seeds was reduced, because average particle cycle time was increasing. This means that more particles can pass through the drafttube inlet, promoting the impact and attrition between seeds and the draft tube wall. Both results suggest that the mechanism of powder production is strongly influenced by seed impact and attrition on the draft tube wall near the column inlet. Based on these preliminary results, Ezequias et al. (1994) have used a two-level factorial design to program the experiments for optimizing draft tube dimensions in the conical SB unit as a function of powder production rates. The highest level of h,, d, and L, was the most appropriate draft tube configuration, as reported by Massarani et al. (1992). The lowest level of h, was determined experimentally as the minimum value to maintain stable solids


1863

circulation, below which solids circulation rates were drastically reduced (seeds clog the annulus-spout cross-section area). The amount of powder produced was chosen as the main response variable for analyzing and optimizing draft tube dimensions. Table 2 shows the experimental conditions used in this step. To prevent seeds from being carried to the cyclone, V N , had to be limited to 1.1. Because of this, DT#7 and DT#8 experiments could not be performed. With an increase in VN,,,, to 1.2, a large amount of seeds was carried to the Downloaded by [Adriana S. Franca] at 07:43 30 July 2014

cyclone. The other six experiments ran properly at VIV,,

=

1.1 and were

reproducible. Prediction of Drying Air Temperature A heater with two electrical resistances (3000 W each) was used in batch

seed drying experiments. The air temperature was controlled by an in line odoff system (IBRACON, 5 step control Model). Type K thermocouples connected to a digital thermometer (IOPE Ltda) were located: (i) at the inlet nozzle pipe, recording inlet air temperature (T,); (ii) at the column exit, recording outlet air temperature (T,);

(iii) inside the sampling locations #I and #2 (Figure 2).

recording seed temperatures just above the bed and at a height halfway up the annulus region. When averaged, these temperatures represented well the mean seed temperature in the SB column (T,) as a function of time; (iv) at the conical column wall, recording wall temperature (T,); (v) near the SB column wall. registering air ambient temperature (Tamb).The measured values of T, and Tb, were used to estimate heat loss during the experiment. A portable psychrometer measured ambient air relative humidity. Inlet air humidity, y,, was calculated based on vapor-air equilibrium equations (Mujumdar, 1987).

Seeds were

humidified using the methodology developed by Menezes at al. (1995). Table 3 presents the inlet air and initial seed conditions used in these experiments. During one hour of drying, T,., T,, T,, and Tambwere recorded as a function of time. Seed samples were taken from the bed every 5 minutes to evaluate

PASSOS ET AL

.

.

TABLE 2 -Conditions Used in the First Steo Exoeriments. (Fixed variables: M = 6 kg; VIV,, = I . I and t, = 3 h.) ~est

dt (m)

1

L, (m)

1

ht (m)

I

T~IM (o C)

I ~$1-

(O

C)


0 DT# I 0.05 0.50 39 45

DT#7

0.03

0.50

0.04

DT#8

0.03

0.50

0.06

(*) unstable spouting regime at VN, = I . 1

(*)

(*)


1865

moisture content. Mass and energy balances as well as the liquid diffusion theory were used to describe and simulate this drying process (Freitas, 1996). Powder Production and Characterization In the third step of the experimental program, a nylon screen was placed at the top of the cylindrical section of the conical SB unit. This prevented seeds


from being carried to the cyclone and improved powder production by producing the impact between the seeds and the nylon screen. Draft tube dimensions were specified using the results obtained in the first step. Experiments were carried out under the conditions presented in Table 4. The mass of powder produced was measured (Menler Analytical Scale, AB204 Model) every 15 minutes during the first 5 hours and every 30 minutes

after this initial period. Due to electrostatic charges, it was necessary to hit the cyclone wall with a hammer to detach the powder before collecting it. The quality of powder produced was evaluated by sampling the amount of powder collected and measuring moisture content, size distribution and bixin concentration during the experiment. Powder moisture content measurements followed the same methodology described earlier for seeds. Sieve analysis was carried out to determine powder size distribution. A Tyler screen series (48 to 400 mesh) mounted in the laboratory scale rotap sieve shaker was employed. The

powder bixin concentration was semi-quantitatively evaluated by HPLC analysis. High Performance Liquid Chromatography Analysis An analytical methodology was developed which permitted the separation and funher quantification of the major pigments in powder extracts. The main issue considered in selecting the analytical technique was how to overcome the photochemical, oxidative and thermal decomposition problems to which the pigments are subjected.

1866

PASSOS ET AL. TABLE 4 - Conditions Used in the Third Step Experiments.


(a) Experiment with replication.

High Performance Liquid Chromatography (HPLC) was the technique selected since it presents solutions to all decomposition problems (Rouseff, 1988). Photochemical decomposition is virtually eliminated because separation occurs within an opaque system. Oxidative decomposition is greatly reduced because most of the oxygen is removed from the mobile phase in solvent degassing. In addition, separation occurs very fast, precluding any oxidative reactions, which are generally slow. Thermal decomposition is completely avoided since separation can be carried out at relatively low temperatures. HPLC analyses of powder samples were performed on a Pharmacia chromatograph (Uppsala, Sweden). Annatto components were separated at ambient temperature (20

- 22 'C) using a MinoRPC S5120 (C2/C18)column (5

pm; 200 x 4.6 mm i.d.). Detection was carried out by a UV-Vis detector at wavelength of 405 nm. An isocratic system with a mobile phase consisting of a methanol-water-acetic acid (87:13:1) solution at 1 mumin was employed. A mass of 0.025 g of powder extract was accurately weighed and dissolved in 10 ml of methanol HPLC grade (for each of the analyses). Approximately 3 to 4 ml of this solution was filtered through a 0.45 pm filter, and 20 p1 of the clarified sample was promptly injected into the HPLC system. Bixin concentrations were semi-

BIXlN POWDER PRODUCTION

1867

quantitatively determined from their integrated peak areas. Calibration was not possible because pure bixin and related compunds were not available.

EXPERIMENTAL RESULTS AND DISCUSSION Results obtained in the first step of the experimental proyam are presented


in Table 5. The moisture content of the powder was approximately the same for all these experiments ( ml,*

= 0.059

d.b. ; SD=0.005).

It can be clearly seen in Table 5 that L,, d, and h, affect powder production and W,, rises with an increase in L, or in d, and with a decrease in h,. It is common knowledge in the SB literature that solids circulation rates are reduced with a decrease in h,. Hence, attrition between seeds (due to solids circulation) is also expected to be reduced (Massarani et al., 1992). The results presented here corroborate the fact that W, increases as h, decreases; therefore, the mechanism of powder production must be governed by the impact and attrition between seeds and draft tube wall, rather than by attrition between seeds. The intensive solids motion at the draft tube inlet is the major factor contributing to powder production. A reduction of h, causes the draft tube inlet to be closer to the inlet solids entrainment region and the amount of air to be larger in this drafi tube entrance, enhancing particle-wall impact and attrition. This also explains the decrease in powder size as h, is reduced for the same L, and d, SB configuration. Data reported by Muir et al. (1990) have indicated that the solids motion at the draft tube entrance is enhanced when d,

=

d,. This supports the results

presented here. An increase in L, implies in a larger wall-particle contact area at each seed cycle in the column. This intensifies seed-wall attrition, improving powder production as shown in Table 5. A comparison of powder size distribution for tests DT#I and DT#3 suggests that wall-seed attrition and impact at the drafi tube entrance contribute to reduce the powder ganulometry. Due to

PASSOS

1868

ET AL.

TABLE 5 - Results from First Step Experiments. Test WD( g k ) % Mass % Mass (SD =0.03 g/kg) < 210 pm < 149 pm


1

I

DT# I

8.89

94

90

DT#2

8.11

93

87

the increase in L,, the average particle cycle time is lower in test DT#I; thus, fewer particles pass through the draft tube inlet and powder size is slightly higher. Although these differences seem negligible here, further increases in L, (> 0.50m) may interfere with powder quality In addition, as L, becomes larger,

seeds tend to be carried easily to the cyclone and the pressure drop increases

(AP,

in test DT#I is about 1.4 times that in DT#3, but it is still 0.76 times lower

than that in the SB unit without dral? tube). This justifies the use of L,= 0.50 m. The combination of variables that leads to the highest powder production rate and to an appropriate powder size distribution is: L, = 0.50 m; d, = di = 0.05 m and h, = 0.04 m. Results obtained in the second step of the experimental program are summarized in Figure 4, where the measured and simulated outlet air and seed temperatures are plotted as a function of drying time for tests U#6 and U#8. As can be seen, T, approaches 60 "C after one hour of drying for T, z 70 OC (test

U#6). Under these conditions, the seed moisture content drops from 0.25 to 0.10. Operating the SB unit with T, z 90 "C, as proposed previously (Massarani et al., 1992). can result in bixin thermal degradation since T, rises to 75 OC after 50 minutes of drying (Figure 4.b). Although these experiments were performed in


I

Tpexp. o

I

-T p s i m

Tgoexp. ....-..T g o s i m


65 s

-T p s i m

0

Tpexp.

o

Tgo exp. . - . . - -Tgo - sim

I

85 s

-

FIGURE 4 Outlet air and x e d temperatures as a tunction of the drying time: (a) Test U#6 ;(b) Test U#8. (See Table 3 for the drying conditions.)

PASSOS ET A L .

the unit without draft tube, it is recommended that 70 OC be the maximum value of T, for drying seeds in safe conditions. In the third step of the experimental program, experiments were performed in the SB unit using the best combination of drat? tube dimensions (L, = 0.50 m; d, = 0.05 m e h, = 0.04 m). The minimum spouting conditions for processing 5 kg of seeds (H = 0.225 m) in this unit were determined experimentally to be: V, 0.027 m3/s (SD = 0.002 m3/s) and AP,

= 699 Pa

=

(SD = 27 Pa).


Figure 5 presents powder production as a function of processing time for the five fixed values of airflow rate specitied in Table 4. From a statistical analysis of the data, the best fining for representing these curves has the following form:

where X is the mass of powder produced per total mass of powder that can be extracted from the seeds; t' is a function of VN,,

and a measure of the

processing time range for each curve; and n is a constant and a function of the powder production mechanism. The maximum amount of powder that can be extracted from the seeds depends on their origin. For the seeds used here, this amount was estimated to be 16% of total seed mass, corresponding to an outer seed cover layer 0.1 mm thick. Massarani et al. (1992) measured the thickness of this outer layer and found values ranging from 0.07 to 0.1 mm. The X vs. t curves tined by Equation I are also displayed in Figure 5; their correlation coefficients varied from 0.96 to 0.99 and standard deviations (based on X values) varied from 0 008 to 0.034. From the replication of test E#4, the experimental SD is 0.018 (X data) or 15 g (mass of powder produced). The F-test statistical analysis confirmed that Equation 1 is adequate to represent these experimental data. The analysis of residuals has shown that they are normally distributed without any visual trend. Thus, Equation ( I ) is appropriate to fit the data. The values obtained for n and t' were correlated with VIV,,, as shown in Figure 6. For the draft tube configuration used here, n decreases as VN,


BIXIN POWDER PRODUCTION

FIGURE 5 - Powder produced as function o f processing time for (a) 1.2 5 VN, 5 I .6 (E# I ; E#2 and E#3) and (b) 1.8 5 VN, 5 1.9 (E#4 and E#5).


PASSOS ET AL.

FIGURE 6 - Prediction o f the (a) n and (b) t' parameters as a function of VN,,,,.


1873

increases, reaching a constant value at VIV,, t 1.6; t' decreases sharply with an increase in VIV,, and tends towards zero as VN,, becomes larger. Equation I was also applied to fit mass powder production data from Massarani et al. (1992). The same trends reported here for the n and t ' parameters were observed. Studies are in progress to correlate these two parameters with the drafi tube dimensions and particle-wall attrition mechanism.


The moisture content of the powder was in the same range as that of the powder in the draft tube optimization experiments (m,= 0.05 1 d.b.; SD = 0.004). As shown in Figure 7, the powder produced became coarser as processing time increased (> 5 h). Powder granulometry for all tests followed the log-normal curve. Table 6 exhibits the relation between airflow rates, average production

-

rate, and mass percentage of fine particles lower than 65 and 100 mesh (Tyler screen series). According to these data, the best set of parameters to produce powder in the SB unit was VN,, limiting value of VN,

1.9 and a processing time of 5 h. This

(up to 2.0) is imposed by the blower and cyclone

systems. Powder samples collected during the processing of the 8. orellunu seeds were analyzed by HPLC. The stand-out peak at a retention time of approximately 14 minutes was partially identified as the bixin pigment by mass spectroscopy and comparison with a sample where the same peak was previously identified. A complete identification would require NMR and 1R spectra, but the necessary equipments were not available at the time. Figure 8 presents the variation of bixin concentration (integmted peak area partially identified as the bixin pigment in the chromatogram of powder produced) with processing time. Pigment concentration was higher at the beginning of the process, and after a significant reduction, remained practically constant until the end of the extraction process. This behavior is due to the fact that the outer seed cover is layered and the highest pigment concentration is at the outside layer, which is removed first.

PASSOS ET AL.


o tp = 1 hour @I= 26 hours

FIGURE 7 - Powder size distribution at one and 26 h. of processing, for test E#I

TABLE 6

- Rate of powder production and size mass fractions lower than 65 mesh (2 10 pm) and I00 mesh (149 pm).

Test E#l E#2

t,

(h) 26.0 , 25.0

VN,,

1.2 1.4

Powder produced rate (g/kg seed h) 1.65 2.10

% Mass c 210 p m

72 69

% Mass

< 149 pm 64 35

An HPLC analysis of the mechanically extracted samples, collected at a processing time of 15 minutes (VN,

=

1.2 and 1.4 and T, n 50

OC),

was

performed and the chromatograms are displayed in Figure 9. The stand-out peak corresponds to the bixin pigment. Notice the presence of a small peak immediately before the bixin peak which is attributed to the occurrence of isomerization reactions. In order to determine the degree of pigment degradation,


0

100

200

300


pmceuinp time (min)

FIGURE 8

- Variation of bixin concentration (integrated peak area) with processing time.

the processed samples were subjected to intensive dqing in an oven at 105•‹Cfor a period of 24 hours. In both cases (samples for VN,

=

1.2 and 1.4). the major

peak (bixin) presented an integrated area reduction of about 70 to 75%, representing the amount of pigment that underwent isomerization and degradation. The small peak close to the bixin peak presented an increase in area that ranged from 80 to 130%, and it possibly represents the major pigment isomerization product. Some of the annano components were volatilized by oven dlying. This improved resolution of peaks at low retention times where a large peak appeared, which is anributed to degradation products.

CONCLUSION Experimental optimization of a conical spouted bed unit with a draft tube was performed for mechanical extraction of annano powder from Rixu orcllunu seeds. A comparison between the powder production rate in this optimized unit and that obtained in a ball mill (maximum of 9.7 &.h;

see Massarani et al.,

1992) indicates that this unit is the best equipment to process the bixin


PASSOS ET AL

FIGURE 9 - Chromatogram o f mechanically extracted annano at 15 min for (a) VIV, = 1.2 and (b) VIV, = 1.4.


1877

extraction. Moreover, powder produced presents 60 % (in mass) of fine particles lower than 100 mesh and a moisture content in the range of 0.05 d.b. This powder is suitable for commercialization as annano (Meer Corporation, 1980). An HPLC methodology was developed to semiquantitatively determine the major pigment contents in mechanically extracted powder. Based on the preliminary results presented here, it can be stated that the thermal degradation of


annano pigments in SB extraction and drying is not significant at a temperature of 50 "C, when compared to intensive drying at a temperature of 105 OC.

NOMENCLATURE di - inlet noule diameter (m) d,, - volume-equivalent particle diameter (m or mm) d, - draft tube internal diameter (m) h, - draft tube entrainment length (m) H - bed height (m) L, - draft tube length (m) mo - initial seed moisture content, dry basis (kgkg) mr- tinal seed moisture content, dry basis (kgkg) m, - powder moisture content, dry basis (kgkg) M - mass of seed processed (kg) t, - processing time (h or min.) Tamb- ambient air temperature ( "C) Tb - bed temperature ( "C) T, - inlet air temperature ( OC) T, - outlet air temperature ( "C) T, - seed temperature ( "C) T, - column wall temperature ( "C) V - inlet airflow rate (m'ls) V, - minimum spouting airflow rate (m3/s) X - mass of powder produced per total mass of powder that can be extracted from the seeds (gkg)

PASSOS El' AL.

1878

W, - mass of powder produced/mass of seed processed (&) yi inlet air absolute humidity (kg vapor1 kg dried air) a - column angle (degree) AF' spout pressure drop (Pa) AP, minimum spouting pressure drop (Pa) Q -void fraction at minimum fluidization or minimum spouting (-) 4 -sphericity (-) Ib heat of desorption (Jikg) p, - solid density (kg/m3) SD standard deviation

-

-

-


-

-

ACKNOWLEDGMENT The authors would like to acknowledge financial support from Brazilian Government Agencies CNPq and FAPEMIG, and from Universidade Federal de Minas Gerais (PRPqRTFMG) to carry out this study.

REFERENCES 1.

Vilela, A,, Baroncelli, F., Mendes, A,, Queiroz, F. M., Mendon~a,J. C. F., Capanema, L., Resende M. S., Oliveira, L. S., Franca, A. S. and Passos, M. L., 1996, Bixin Extraction in Conical Spouted Beds, Internal Report, Federal University of Minas Gerais, Brazil, 80 p (in Portuguese).

2.

Chao, R. R., Mulvaney, S. J., Sanson, D. R., Hsieh, F. and Tempests, M., 1991, Supercritical C 0 2 Extraction of A M ~ (Bixa O Orellano) Pigments and Some Characteristics of the Color Extracts, Journal of Food Science, 56 (1) pp. 80-83.

3.

Dendy, D. A. V., 1966, Annatto, the Pigment of Hirrr orellanu, East Ah. For. J. (Oct.), pp. 126-132.

4.

EMATER, 1994. ~ ~ r i c u l t u r aProduction l in Minas Gerais State, Report, Empresa de Assistencia Tknica e Exte&o Rural do Estado de Minas Gerais (EMATER-MG), Brazil, p. 295.



1879

5.

Ezequias Filho, P. S., Souza, G. M., Pereira, G. G., Souza, J. 0 . and Passos, M. L., 1994, Mechanical Extraction of Bixin in a Conical Spouted Bed, Internal Report, UFMG, Brazil, 56 p. (in Portuguese).

6.

Freitas, M. E. A,, 1996, Modeling Batch Grain Drying in Conical Spouted Beds, M.Sc. Thesis, Federal University of Minas Gerais, Brazil, 168 p.

7.

Freund, P. R., Washam, C. J., Maggion, M., 1988, Natural Color for Use in Foods, Cereal Foods World, 33 (7) pp. 553-559.

8.

Mathur, K. B. and Epstein, N., 1974, Spouted Beds. Academic Press, NY, 304 p.

9.

Massarani, G., Passos, M. L. and Barreto, D. W., 1992, Production of Annano Concentrates in Spouted Beds, Can. J. Chem. Eng., 70 pp. 954-959.

10. McKeown, G. G. and Mark, E., 1962, The Composition of Oil-Soluble Annano Food Colon, J. Assoc. Off Agric. Chem., 45 pp. 761-766.

I I : Meer Corporation, 1980, Annano Technical Information Catalog North Bergen. United States.

.

12. Menezes, J. F., Moura, L. F., Leite, L. F., Ladeira, P. L. G. and Passos, M. L., 1995, Experimental Simulation of Bixa orellana Seed Drylng in a Conical Spouted Bed, Proc. I Brazilian Congress Chem. Eng. Undergraduate Scientific Initiation, SXo Carlos, Brazil, pp. 109-112. (in Portuguese) 13. Muir, J. R., Bemti, F. and Behle, A,, 1990, Solids Circulation in Spouted and Spout-Fluid Beds of Particles, Chem. Eng. Commun., 88 pp. 153-171. 14. Mujumdar, A. S. (ed.), 1987, Handbook of Industrial Drying, Marcel Dekker Inc., New York and Basel, 948 p. 15. Rouseff, R. L., 1988, High Performance Liquid Chromatography Separation and Spectral Characterization of the Pigments in Turmeric and Annano, J. Food Sci., 53 (6) pp. 1823-1826.