Bioactive Compounds and Physicochemical Parameters of Grugru Palm (Acrocomia aculeata) from Brazil: Pulp and Powder

Dalany Menezes Oliveira; Edmar Clemente; José Maria Correia da Costa

doi:10.3136/fstr.20.7

Abstract

As there is little study on grugru palm, the knowledge of the properties of the fruit pulp and powder is important in the fruit production recovering and in the enhancement of the processes of dehydration for better conservation, development and preparation of diverse foods. The objective of this study was to characterize the bioactive compounds and the physicochemical features of grugru palm pulp and powder. Grugru palm fruits were harvested in the Araripe Plateau, Ceará State, Brazil, and dehydrated by two drying methods (in oven with air circulation and lyophilization) with and without addition of drying adjuvant (maltodextrin). After analysis, results revealed that pulp and powder of grugru palm are products with high content of soluble solids and low acidity, highlighting the high levels of β-carotene and vitamin A. The lyophilized powder T3 have showed the best results in relation to the physicochemical and bioactive parameters.

Introduction

Grugru palm (Acrocomia aculeata (Jacq.) Lodd. Ex Mart.) is native to the grasslands and savannas of Tropical America (Clement et al., 2005). This palm tree is of great regional importance due to the wide diversity of products, especially those related to its fruits and seeds (Lorenzi, 2006).

The pulp is eaten fresh or used in the production of powders that can be used in drinks, candies, ice creams, custards, cakes, jellies and juices (Brasil, 2002). The grugru palm fruits show great potential in the enrichment of the regional diet and in supplemental feeding programs, being a natural source of β-carotene and vitamin A, as well as the minerals copper, potassium and zinc (Ramos et al., 2008).

Dehydration of fruits and vegetables is utilized in food preservation, which maintains their nutritional and commercial values and also provides a new product in the market, encouraging investments in agricultural production and processing (Soares et al., 2001).

Many types of dryers utilized in dehydrating food are found in literature and in the drying process of thermo-sensitive foods, additives are required and have to be added in the appropriate level in order to maintain the product acceptability and to follow the limits set by legislation (Oliveira et al., 2007). One of the most common additive applied in drying fruits is maltodextrin, which has low cost and low hygroscopicity thereby preventing agglomeration and retaining the volatile substances in the range of 65 - 80% (Oliveira et al., 2006).

In the literature, the drying processes applied to grugru palm, namely conventional forced air dryers at temperatures ranging from 45 to 65°C and/or drying by direct sunlight can be found. However, other drying methods such as lyophilization have not been studied, as well as a comparison of the processes of dehydration on the quality of grugru palm powder. Therefore, the objective of this study was to characterize the bioactive compounds and the physicochemical features of grugru palm pulp and powder.

Material and Methods

Raw material Grugru palm fruits were harvested in the Araripe Plateau, Cariri region, Ceará State, Brazil, and taken to the Laboratory of Food Quality Control and Drying for selection and sanitization; subsequently they were peeled and the pulp stored in a freezer at −20°C until drying and analyses.

The pulps were analyzed in the following forms: integral pulp (IP) and with 8% maltodextrin (MP).

Grugru palm pulps were dried by two processes:

T1: oven drying without maltodextrin.

T2: oven drying with 8% maltodextrin.

T3: lyophilized without maltodextrin.

T4: lyophilized with 8% maltodextrin.

Chemical All chemicals and solvents used for determination β-carotene and Vitamin A were of reagent or HPLC grade. The standard of β-carotene was obtained from Sigma Chemical Co. (St. Louis, MO).

Oven drying The pulps (T1 and T2) were unfrozen, smashed and distributed in stainless steel trays with 25 cm diameter; then the trays were taken to a forced air oven (TECNAL, model TE-394/l) at 65°C for 25 h (Oliveira et al., 2012). Immediately after drying, the product was taken to a rotatory blade mill (MA 048, Marconi) in order to obtain a homogeneous powder.

Lyophilization The pulps (T3 and T4) were unfrozen, smashed and distributed in stainless steel trays with 15 cm diameter; then the trays were taken to a ultra-freezer (LC 90 _ 40 V, Terroni) at _ 40°C for 24 h; after this period the pulps were dehydrated in a benchtop lyophilizer (LS 3000, Terroni) for 25 h (Oliveira et al., 2013). Immediately after lyophilization, the product was taken to a rotatory blade mill (MA 048, Marconi) in order to obtain a homogeneous powder.

Bioactive compounds The total phenolics were extracted and determined according to the method described by Buci-Kojic et al. (2007). The yellow flavonoids were extracted in accordance to Francis (1982), through a solution of ethanol:HCl 1.5 mol L⁻¹ (85:15).

The ascorbic acid (vitamin C) was titrated by a solution of 2,6-dichloro-phenol-indophenol as described by Strohecker and Henning (1967).

The extraction of β-carotene was carried out as described by Rodriguez-Amaya (1999) with a little modification. Samples (5 g) sample were extracted with cold acetone until the residue becomes colorless; then it was filtered under vacuum using a Büchner funnel. The pigments extracted were then transferred to petroleum ether and washed in distilled water until complete removal of the acetone. The extract concentration was made in a rotatory evaporator at 35°C. The pigments were dissolved in acetone, filtered in a PTFE with 0.22 µm membrane and then analyzed. The β-carotene content was analyzed by HPLC chromatographic conditions developed by Sant'Ana et al. (1998) with modifications. The devices utilized are: a liquid chromatograph (model Gilson 321 pump) with automatic injector (model Gilson 234) and handle of 20 µL (loop), column ACE 5 C18 (5 µm, 150x4.6 mm), visible-UV detector at 450 nm (model Gilson 152). The mobile phase was composed of methanol/acetonitrile/ethyl-acetate (80:10:10) at a rate of 1.5 ml.min⁻¹ with running time of 60 minutes.

The quantification of β-carotene was attained by external standard curves. The vitamin A activity of β-carotene was obtained according to Bauernfeind (1972) and the conversion factor; the calculation of vitamin A was provided by the National Research Council (NAS, 1980) in which 6 µg of β-carotene correspond to 1 Retinol Equivalent (RE).

Physicochemical determinations The moisture content was determined gravimetrically at 105°C in an oven until constant weight according to the technique described by Instituto Adolfo Lutz (2005). The water activity (a_w) was determined by a portable measurer (AquaLab®). The pH level was performed by a potentiometer, following the method described by AOAC (1998), number 31.1.07. The titratable acidity was determined through NaOH (1 mol L⁻¹) until pH 8.1 was reached. The soluble solids were measured by a digital refractometer (Atago, Pocket-pal model) with scale from 0 to 35° Brix (Carvalho et al., 1990).

The pulp and powder colors were determined by a colorimeter (Minolta, model CR410, Konica Minolta Sensing, Inc., Japan) in the mode CIE L*a*b* and parameters D65 (Y = 93.9; x = 0.3167; y = 0.3336).

Statistical analysis All analyses were performed in triplicate (n = 3). Data were statistically analysed using the analysis of variance (ANOVA) and the differences between the averages were determined by the Tukey test at 5% probability using the software Statistic, version 7.0 (Statsoft, 2007).

Results and Discussion

Bioactive compounds of pulp and powder of grugru palm Table 1 shows the bioactive compounds of IP (integral pulp) and MP (with 8% maltodextrin). The loss of vitamin C in MP was 37.2% and this is linked to the drying additive which could have encapsulated the ascorbic acid molecule, turning it difficult to be extracted. The total phenolics is higher than that found by Kuskoski et al. (2005) in cupuassu pulp (20.5 mg GAE 100 g⁻¹) and lower than those found in fruits such as grapes (117 mg GAE 100 g⁻¹) and hog plum (136 mg GAE 100 g⁻¹). The MP flavonoids were 32.1% lower than that of IP, even with no statistical difference at 5% of probability. The pulp flavonoids range similar to those found in kale 266 - 399 µg g⁻¹ (Huber and Rodriguez-Amaya, 2008), and in pulps of orange var. ‘Pera’ 348 µg g⁻¹ and apple var. ‘Gala’ 277 µg g⁻¹ (Arabbi et al., 2004). The pulps of grugru palm fruits presented high levels of β-carotene and vitamin A, and these levels were higher than those found by Charoensiri et al. (2009) in orange 1.7 µg g⁻¹, watermelon 6.2 µg g⁻¹ and papaya 4.7 µg g⁻¹. Ramos et al. (2008) reported a content of 49 µg g⁻¹β-carotene in grugru palm pulp. The high content of β-carotene in the pulp of grugru palm is related to the color of fruits and vegetables, which ranges from yellow to red and refers to high levels of carotenoids, according to Uenojo et al. (2007).

Table 1. Bioactive compounds of grugru palm pulp, integral and with addition of 8% maltodextrin.

Analyses	IP^a ± δ	MP^b ± δ^c
Total phenolics, (mg GAE^d 100 g⁻¹)	51.3^a ± 10.7 *	49.8^a ± 2.03
Yellow flavonoids, (µg g⁻¹)	372.1^a ± 76.0	247.8^a ± 46.3
Vitamin C, (mg 100 g⁻¹)	118.2^a ± 6.01	72.8^b ± 8.70
β-carotene, (µg g⁻¹)	35.9^a ± 1.09	34.7^a ± 2.03
Vitamin A, (RE^e 100 g⁻¹)	599.7^a ± 18.1	579.2^a ± 33.8

^aIP: integral pulp; ^bMP: pulp with 8% maltodextrin; ^cδ: standard deviation; ^dGAE: gallic acid equivalent; ^eRE: retinol equivalent. *Equal lowercase letters in the same line do not differ statistically by Tukey test at 5% probability.

Table 2 presents the bioactive compounds of grugru palm powder in T1 and T2 (oven drying) and in T3 and T4 (lyophilized). The contents of bioactive compounds (phenolics, vitamin C and vitamin A) in T3 and T4 were the highest, showing lyophilization a better process for retention of these compounds. However, the flavonoids in T1 and T2 were higher than those of T3 and T4; these lower levels in T3 and T4 were probably caused by the freezing period before the lyophilization. Huber and Rodriguez-Amaya (2008) stated that processed products have flavonoids contents substantially lower than those found in fresh fruits.

Table 2. Bioactive compounds of grugru palm pulp obtained by different processes of drying, integral and with 8% maltodextrin.

Analyses	T1^a ± δ	T2^{b ± δ}	T3^c ± δ	T4^d ± δ^e
Total phenolics	82.7^ab*	65.1^b	89.4^a	86.9^a
(mg GAE^f 100 g⁻¹)	± 7.98	± 6.7	± 5.7	± 8.5
Yellow flavonoids	135.7^a	121.1^ab	115.6^b	93.6^c
(µg g⁻¹)	± 12.6	± 4.47	± 3.46	± 3.51
Vitamin C	52.1^b	51.7^b	103.3^a	100.7^a
(mg 100 g⁻¹)	± 5.6	± 3.09	± 5.6	± 5.63
β-carotene	51.5^bc	36.1^c	80.1^a	57.6^b
(µg g⁻¹)	± 0.66	± 0.50	± 7.3	± 3.99
Vitamin A	859.4^bc	601.3^c	1334.8^a	961.4^b
(RE^g 100 g⁻¹)	± 10.9	± 8.3	± 122.0	± 66.41

^aT1: oven drying without maltodextrin; ^bT2: oven drying with 8% maltodextrin; ^cT3: lyophilized without maltodextrin; ^dT4: lyophilized with 8% maltodextrin; ^e±δ: standard deviation; ^fGAE: gallic acid equivalent; ^gRE: retinol equivalent; *Equal lowercase letters in the same line do not differ statistically by Tukey test at 5% probability.

Physicochemical evaluation of pulp and powder of grugru palm Table 3 presents the physicochemical parameters related to moisture, water activity, acidity, pH, soluble solids and pulp color. In general, the maltodextrin did not change these parameters, except for a_w, and color L*a*. The pulps have showed low moisture and acidity and high soluble solids and a_w, which makes them sweet and susceptible to microbial growth. Different levels of moisture and acidity were found in the literature: Ramos et al. (2008) observed a high moisture content (52.99 g 100 g⁻¹) and Hiane et al. (2005) reported values of acidity lower than 0.83 g 100 g⁻¹. These variations could have been caused by different factors, e.g., fruit origin, climatic conditions, harvest time, type of pulping, etc. The pulps in this study have showed an overall orange color, but the IP presented a more intense orange color than the MP.

Table 3. Physicochemical features of grugru palm pulp, integral and with 8% maltodextrin.

Analyses		IP^a ± δ	MP^b ± δ^c
Moisture, (g 100 g⁻¹)		40.2^a* ± 0.72	41.3^a ± 0.31
a_w^d		0.92^b ± 0.01	0.94^a ± 0.002
Titratable acidity, (g 100 g⁻¹)		1.43^a ± 0.07	1.64^a ± 0.27
pH		5.50^a ± 0.02	5.68^a ± 0.14
Soluble solids, (°Brix)		29.7^a ± 0.58	27.6^a ± 2.81
Color	L*	42.4^a ± 0.43	41^b ± 0.69
	a*	5.08^a ± 0.31	1.46^b ± 0.17
	b*	17.3^a ± 1.80	19.4^a ± 0.36

^aIP: integral pulp; ^bMP: pulp with 8% maltodextrin; ^cδ: standard deviation; ^da_w: water activity; L* (lightness-darkness), a* (redness-greenness) and b* (blueness-yellowness). * Equal lowercase letters in the same line do not differ statistically by Tukey test at 5% probability.

Table 4 presents the physicochemical parameters of grugru palm powder of T1 and T2 (oven drying), T3 and T4 (lyophilized). The treatment T3 has showed the lowest moisture and a_w; however, all drying processes have decreased moisture and a_w, which provide the inhibition of microbial growth. According to Ordóñez (2005), foods with a_w below 0.60 are labeled as microbiologically stable without microbial growth, which confirms our results. There was no difference amongst treatments in relation to acidity and pH, which shows that the drying methods did not affect these factors. The T4 has had the highest content of soluble solids followed by the T2, and the explanation for such high levels is the addition of maltodextrin. The grugru palm with the darkest L* parameter was the T2; in relation to the chromaticity a* and b*, the T3 presented the most bright yellow color followed by the T4, thus showing a more attractive color. The other treatments (T1 and T2) presented a paler chromaticity.

Table 4. Characterization of grugru palm powders according to different drying processes and with addition of 8% maltodextrin.

Analyses		T1^a ± δ	T2^b ± δ	T3^c ± δ	T4^d ± δ^e
Moisture, (g 100 g⁻¹)		3.28^ab* ± 0.08	3.41^a ± 0.11	3.12^b ± 0.09	3.49^a ± 0.12
a_w^f		0.21^a ± 0.01	0.22^a ± 0.01	0.12^b ± 0.01	0.22^a ± 0.01
Titratable acidity, (g 100 g⁻¹)		2.10^a ± 0.01	2.47^a ± 0.55	2.06^a ± 0.05	2.50^a ± 0.32
pH		5.57^a ± 0.02	5.62^a ± 0.10	5.71^a ± 0.01	5.60^a ± 0.02
Soluble solids, (°Brix)		40.3^c ± 0.89	45.7^ab ± 2.63	45.1^bc ± 1.28	50.3^a ± 2.32
Color	L*	49.7^a ± 0.09	48.8^b ± 0.23	49.7^a ± 0.26	49.8^a ± 0.14
	a*	−1.38^c ± 0.04	−1.03^ab ± 0.14	−1.24^bc ± 0.10	−0.94^a ± 0.09
	b*	24.6^c ± 0.16	22.6^d ± 0.14	27.2^a ± 0.28	26.3^b ± 0.35

^aT1: oven drying without maltodextrin; ^bT2: oven drying with 8% maltodextrin; ^cT3: lyophilized without maltodextrin; ^dT4: lyophilized with 8% maltodextrin; ^e±δ: standard deviation; ^fa_w: water activity; L* (lightness-darkness), a* (redness-greenness) and b* (blueness-yellowness). *Equal lowercase letters in the same line do not differ statistically by Tukey test at 5% probability.

Effect of drying on bioactive compounds The technological processing and the types of nutrients in the foods are directly related to losses of bioactive compounds. In this study, there were different levels of loss of bioactive compounds in the two processes of pulp dehydration, i.e., forced air oven drying (T1 and T2) and lyophilization (T3 and T4).

The powders T1 and T2 suffered a reduction in phenolics of 0.32 and 21.4%, respectively. This greater loss of phenolics in T2 is probably associated to the difficulties in extraction and quantification of phenolics due to the addition of the maltodextrin. The powders T3 and T4 did not suffer losses of this constituent.

The levels of flavonoids were the most affected by the treatments, and their losses have ranged from 77.4 to 80.8%. Ewald et al. (1999) demonstrated that the great loss of flavonoids in vegetables takes place during peeling, cutting, pre-processing and bleaching, which explains the losses found in this study.

The vitamin C contents have reduced during the drying processes, as expected, because the stability of this vitamin is affected by several factors, such as oxygen, pH, light, enzymes and catalysts (Ordóñez, 2005). The largest losses have occurred in the powders T1 and T2, 72.7 and 72.9%, respectively; the lyophilized products, T3 and T4, have showed the lowest losses: 46.0 and 47.1%, respectively. The lyophilized products have presented the lowest losses because the stability of vitamin C increases along with decreasing temperature (Ordóñez, 2005).

The treatments T1 and T2 have showed the largest losses of β-carotene and vitamin A. The T1 and T2 have lost 11.4 and 37.9% of these constituents, respectively. The levels of β-carotene and vitamin A in the T3 did not change, and in the T4 the loss of these bioactive compounds was 0.67%.

The grugru palm fruits have an interesting nutritive potential. The mesocarp of grugru palm fruit provides significant concentrations of β-carotene, a natural antioxidant and pro-vitamin A; so the pulp can be included in feeding programs of the poor and contribute to the food enrichment as a source of vitamin A. This work contributes to the study of the stability of bioactive compounds and quality parameters of dehydrated grugru palm pulp, aiming to define the best processing and conservation conditions for applying to this raw material as a new ingredient in different formulations of food products.

Conclusion

The grugru palm pulp is a product of low acidity, presents an orange color and has excellent levels of bioactive compounds, especially of β-carotene and vitamin A. The addition of 8% maltodextrin did not affect the concentration of vitamin C.

The lyophilized powders T3 and T4 have showed the best results in relation to the physicochemical and bioactive parameters, highlighting the T3 in relation to moisture content, water activity, and levels of β-carotene and vitamin A.

Acknowledgement To Laboratory of Food Quality Control and Drying for supporting the research; to CNPq through INCT and Araucaria Foundation for the scholarship.

References

Arabbi, P.R., Genovese, M.I., and Lajolo, F.M. (2004). Flavonoids in vegetable foods commonly consumed in Brazil and estimated ingestion by the brazilian population. J. Agric. Food Chem., 52, 1124-1131.
AOAC (1998) Official method of analysis of AOAC international, (16th Ed.). Arlington. Association of Official Analytical Chemists.
Bauernfeind, J.C. (1972). Carotenoid Vitamin A Precursors and Analogs in Foods and Feeds. J. Agric. Food Chem., 20, 456-473.
Brasil. Ministério da Saúde. (2002). “Alimentos regionais brasileiros”. Ministério da Saúde, Secretaria de Políticas de Saúde, Coordenação-Geral da Política de Alimentação e Nutrição. Ministério da Saúde, Brasília.
Bucic´-Kojic´, A., Planinic´, M., Tomas, S., Bilic´, M., and Velic, D. (2007). Study of solid-liquid extraction kinetics of total polyphenols from grape seeds. J. Food Eng., 81, 236-242.
Carvalho, C.R.L., Mantovan, D.M.B., Carvalho, P.R.N., and Moraes, R.M. (1990) “Análises químicas de alimentos”. Instituto de Tecnologia de Alimentos, Campinas.
Charoensiri, R., Kongkachuichai, R., Suknicom, S., and Sungpuag, P. (2009). Beta-carotene, lycopene, and alpha-tocopherol contents of selected Thai fruits. Food Chem., 113, 202-207.
Clement, C.R., Lleras Pérez, E., and Van Leeuwen, J. (2005). O potencial das palmeiras tropicais no Brasil: acertos e fracassos das últimas décadas. Agrociencias, 9(1-2), 67-71.
Ewald, C., Fjelkner-Modig, St., Johansson, K., Sjöholm, I., and Akesson, B. (1999). Effect of processing on major flavonoids in processed onions, green beans, and peas. Food Chem., 64, 231-235.
Francis, F.J. (1982). Analysis of anthocyanins. In: Markakis, P., (ed.). “Anthocyanins as food colors”. Academic Press, New York, pp. 181-207.
Hiane, P.A., Ramos Filho, M.M., Ramos, M.I.L., and Macedo, M.L.R. Bocaiúva. (2005). Acrocomia Aculeata (Jacq.) Lodd., Pulp and Kernel Oils: Characterization and Fatty Acid Composition. Brazilian J. Food Technol., 8(3), 256-259.
Huber, L.S. and Rodriguez-Amaya, D.B. (2008). Flavonóis e flavonas: fontes brasileiras e fatores que influenciam a composição em alimentos. Alim. Nutr., 19(1), 97-108.
IAL. Instituto Adolfo Lutz. Ministério da Saúde. Agência Nacional de Vigilância Sanitária. (2005). “Métodos Físico-Químicos para Análise de Alimentos/Ministério da Saúde, Agência Nacional de Vigilência Sanitária”. Ministério da Saúde, Brasília.
Kukoski, E.M., Asuero, G.A., Troncoso, A.M., Mancini-Filho, J., and Fett, R. (2005). Aplicación de diversos métodos químicos para determinar actividad antioxidante em pulpa de frutos. Ciênc. Tecnol. Alimentos. 25(4), 726-732.
Lorenzi, G.M.A.C. (2006). Acrocomia aculeata (Lodd.) ex Mart. - Arecaceae: bases para o extrativismo sustentável. PhD. Thesis, Universidade Federal do Paraná, Curitiba.
National Academy of Sciences/ National Research Council. (1980). “Recomended dietary allowance”. (9th Ed). Washington, pp. 55-60.
Oliveira, A.R.G., Borges, S.V., Faria, R.K., Endo E., and Gregório, S.R. (2007). Influência das condições de secagem por atomização sobre as características sensoriais de sucos maracujá, (passiflora edullis) e abacaxi, (ananas comosus) desidratados. Rev. Ci”nc. Agronômica, 38(3), 251-256.
Oliveira, D.A., Moreira, P.A., Melo-Júnior, A.F., and Pimenta, M.A.S. (2006). Potencial da biodiversidade vegetal da região norte do estado de Minas Gerais. Unimontes Científica, 8, 23-33.
Oliveira, D.M., Clemente, E., and Costa, J.M.C. (2012). Hygroscopic behavior and degree of caking of grugru palm, (Acrocomia aculeata) powder. J. Food Sci. Technol. DOI 10.1007/s13197-012-0814-9
Oliveira, D.M., Clemente, E., Afonso, M. R. A., and Costa, J.M.C. (2013). Hygroscopic Behavior of Lyophilized Powder of Grugru Palm, (Acrocomia aculeata). American Journal of Analytical Chemistry. 4(10A), 1-7.
Ordoñez, J.A. (2005). “Tecnologia de alimentos: Componentes dos alimentos e processos”. Artmed editora, São Paulo.
Ramos, M.I.L., Ramos Filho, M.M., Hiane, P.A., Braga-Neto, J.A., and Siqueira, E.M.A. (2008). Qualidade nutricional da polpa de bocaiúva Acrocomia aculeata (Jacq.) Lodd. Ciên. Tecnol. Alimentos, 28, 90-94.
Rodriguez-Amaya, D.B. (1999). “A guide to carotenoid alanysis in food”. ILSI Press, Washington.
Sant'Ana, H.M.P., Stringheta, P.C., Brandão, S.C.C., and Azeredo, R.M.C. (1998). Carotenoid retention and vitamin A value in carrot (Daucus carota L.) prepared by food service. Food Chem., 61(1-2), 145-151.
Soares, E.C., Oliveira, G.S.F., Maia, G.A., Monteiro, J.C.S., Silva Junior., A., and S. Filho, M.S. (2001). Desidratação da polpa de acerola (Malpighia emarginata D.C.) pelo processo foam -mat. Ciênc. Tecnol. Alimentos, 21(2), 164-170.
Statsoft. (2007). Statistica for Window - Computer programa manual. Versão 7.0 Tulsa, Statsoft Inc.
Strohecker, R. and Henning, H.M. (1952). Analisis de vitaminas: métodos comprobados. Madrid: Paz Montalvo, 1967. McCready, R. M.; McComb, E. A. Extraction and determination of total pectic material in fruits. Analytical Chem., 24(12), 1586-1588.
Uenojo, M., Maróstica-Junior, M. R., and Pastore, G.M. (2007). Carotenóides: propriedades, aplicações e biotransformação para formação de compostos de aroma. Quim. Nova, 30(3), 616-622.

責任著者(Corresponding author)

J-STAGEへの登録はこちら（無料）