Abstracts

Strawberry harvest begins at approximately 60/80 days after transplanting plantlets to the field (Cantillano, 2005CANTILLANO RFF. 2005. Colheita e pós-colheita. In: ANTUNES LEC; DURATE FILHO J. (eds) Sistema de produção do morango. Sistemas de Produção. Embrapa Clima Temperado.). One of the recent techniques used by strawberry growers is the biennial crop replanting, in which plants are maintained in the field for two consecutive cycles, allowing two crops with the same plants at Season 1 (January, February and March) and Season 2 (August, September and October), which reduces cost, because plantlets are one of the main costs of strawberry production (Oliveira & Scivittaro, 2009OLIVEIRA RP; SCIVITTARO WB; WREGE MS; UENO B; CASTRO LAS. 2006. Otimização da produção nacional de mudas de morangueiro. EMBRAPA (Boletim Técnico 162), 28p.).

One of the obstacles for the strawberry production is the low number of cultivars available (Oliveira et al., 2008OLIVEIRA RP; SCIVITTARO WB. 2009. Produção de frutos de morango em função de diferentes períodos de vernalização das mudas. Horticultura Brasileira 27: 91-95.). 'Camino Real' (short-day cultivar) and 'Albion' (day-neutral cultivar), from the University of California Breeding Program, are important cultivars in Southern Brazil. However, other cultivars from the same origin are also occasionally planted, but with very little information about their field performance (Oliveira et al., 2006OLIVEIRA RP ; SCIVITTARO WB. 2008. Produção de morangueiro da cv. Camino Real em sistema de túnel. Revista Brasileira de Fruticultura 30: 681-684.; Antunes et al., 2010ANTUNES LEC; RISTOW NC; KROLOW ACR; CARPENEDO S; REISSER JÚNIOR C. 2010. Produtividade e qualidade de cultivares de morangueiro. Horticultura Brasileira 28: 222-226.), what is even more relevant when considering the biennial crop replanting.

Attributes such as fruit size, texture, presence of functional compounds and C-vitamin content depend on genetic and environmental factors and should be considered in the selection of new cultivars (Camargo et al., 2011CAMARGO LKP; RESENDE JTAV; TOMINAGA TT; KURCHAIDT SM; CAMARGO CK; FIGUEIREDO AST. 2011. Postharvest quality of strawberry fruits produced in organic and conventional systems. Horticultura Brasileira 29: 577-583.; Silva et al., 2013SILVA TP. 2011. Características produtivas e físico-químicas de frutos de morangueiro orgânico cultivado com o uso de extrato de algas. Curitiba: UFPR. 123p. (Dissertação mestrado).; Basu et al., 2014BASU A; NGUYEN A; BETTS NM; LYONS TJ. 2014. Strawberry as a functional food: an evidence-based review. Critical Reviews in Food Science and Nutrition 54: 790-806.). The food composition has been a frequent focus of researches seeking to identify nutritional differences among cultivars (Tulipani et al., 2008TULIPANI S; MEZZETTI B; CAPOCASA F; BOMPADRE S; BEEKWILDER J; VOS CH; CAPANOGLU E; BOVY A; BATTINO M. 2008. Antioxidants, phenolic compounds, and nutritional quality of different strawberry genotypes. Journal of Agricultural and Food Chemistry 56: 696-704.; Cantillano et al., 2012CANTILLANO RFF. 2005. Colheita e pós-colheita. In: ANTUNES LEC; DURATE FILHO J. (eds) Sistema de produção do morango. Sistemas de Produção. Embrapa Clima Temperado.), and also among cultivation techniques (Darolt, 2003DAROLT MR. 2003. Comparação da qualidade do alimento orgânico com o convencional. In: STRIGHETA PC; MUNIZ JN (eds). Alimentos orgânicos: produção, tecnologia e certificação, 1 ed. Viçosa: UFV.; Cantillano et al., 2012).

Also, strawberry fruits must present good acceptance by the consumer market, because choosing, at the purchase act, is generally based on fruit appearance, but the decision towards buying the same product again depends mainly on the flavor (Kader, 1999KADER AA. 1999. Fruit maturity, ripening, and quality relationships. Acta Horticulturae 485: 203-208.). Sensory analysis appears to be an important tool in evaluating the quality of food products (Ferreira et al., 2000FERREIRA VLP; ALMEIDA TCA; PETTINELLI MLCV; SILVA MAAP; CHAVES JBP; BARBOSA EMM. 2000. Análise sensorial: testes discriminativos e afetivos. Manual: série qualidade. Campinas: SBCTA, 127.). Simple instrumental measurements are not able to predict the sensory characteristics of strawberry cultivars (Vicente et al., 2014SILVA PA; ABREU CMP; ASMAR SA; CORREA AD. 2013. Quality evaluation of strawberries grown in the region of Lavras, Minas Gerais State. Acta Scientiarum 35: 777-782.). However, few scientific articles studying fruit quality have included sensory evaluations, due to difficulties concerning the judges selection and training, as well as the ethical issues related to researches involving human beings.

Among the sensory analysis methods available to measure the preference of consumers, the Quantitative Descriptive Analysis (QDA) is probably the most widely used method due to the reliability and validity of its results, in addition to its simplicity of execution. The result of evaluating QDA is converted into numerical scores, which are statistically analyzed to determine the preference for a specific sample from the evaluated set (Dutcoski, 2007DUTCOSKY SD. 2007. Análise Sensorial de Alimentos. Curitiba: Coleção Exatas, 4p.).

The goal of this research was to evaluate the postharvest fruit quality of six strawberry cultivars (Albion, Camino Real, Palomar, Portola, Monterrey and San Andreas) produced for two consecutive seasons with the same runners.

MATERIAL AND METHODS

This study was carried out in a commercial strawberry farm operating in an Integrated Production Management, under low tunnel structure, in 2010/11, located in São José dos Pinhais, Metropolitan Region of Curitiba (CMR), Paraná state, Brazil (25º36'48"S, 49º04'55"W, 932 m altitude).

Strawberry seedlings of 'Camino Real' and 'Palomar' (short-day cultivars) were transplanted in May 2010 and 'Albion', 'Portola', 'Monterey' and 'San Andreas' (day-neutral cultivars) were transplanted in July 2010. These seedlings were transplanted to 33 beds measuring 6 m long, 1 m wide and 0.5 m high, and they were set out 0.3 m apart. Twenty days before transplanting, soil was fertilized with 60 g m² of NPK formula 4-12-8. After that, fertilization was applied weekly, beginning 15 days after transplanting, by fertigation with 12 kg ha^-1 of NPK 15-30-15.

Physico-chemical, C vitamin content, and sensory analyses were carried out with fruits harvested in 2011 during two growing seasons (season 1= in January, February and March and season 2= in August, September and October), in a total of three samples of each cultivar from each season. Fruits were harvest at 75% of the external surface with red color. The harvest was carried out from 8 to 10 AM; fruits were picked randomly among 500 plants of each cultivar. The physico-chemical analyses were made with 25 fruits of each cultivar. Fruits were organized into five replications of five fruits and kept for three days before analysis under refrigeration (average temperature of 4°C).

Physico-chemical characteristics evaluated were titratable acidity (TA), soluble solids (SS), both according to the methodology described by Horwitz & Latimer (2005)HORWITZ W; LATIMER GW. 2005. Official methods of analysis of the Association of Official Analytical Chemistry.18th ed. Washington, 1015p.. These analyses provided the values for calculating the SS/TA ratio. Fruit firmness was measured using Brookfield CT3 Texture Analyzer with a probe of 2 mm of diameter, 5 mm of penetration at speed of 5 mm s^-1.

C vitamin content was evaluated as recommend by Horwitz & Latimer (2005)HORWITZ W; LATIMER GW. 2005. Official methods of analysis of the Association of Official Analytical Chemistry.18th ed. Washington, 1015p.. Twenty fruit samples of each cultivar were randomly taken from the studied area on January, February and March and on August, September and October. Fifty grams of 2% oxalic acid was added to 25 g of each sample. After that, 20 grams of this solution were taken out and transferred to a 50 mL volumetric flask and filled with oxalic acid. The titration was done with DCFI (2.6, dichlorophenol-indophenol) and with the solution described above, which was filtered in paper, an aliquot of 10 mL being withdrawn for analyzes. Results were expressed in milligrams of ascorbic acid per 100 g of sample.

Sensory analysis was undertaken with 55 people, who were strawberry consumers and interested in participating on a regular basis of this strawberry sensory analysis. The project aim was explained to the participants when they were first contacted, as well as the importance of their participation, the meanings of sensory analysis terminology, and how the evaluations would be made by QDA methodology, as recommended by Dutcoski (2007)DUTCOSKY SD. 2007. Análise Sensorial de Alimentos. Curitiba: Coleção Exatas, 4p..

QDA form containing an unstructured scale of 10 cm for each of the attributes to be evaluated: sweetness, flavor, acidity, aroma, shape, and flesh firmness was presented to each participant. They were trained to register their strawberry opinions on the QDA form from bad to good. These fruits were previously cleaned under running tap water. After training, 22 judges were selected, those that had a higher sensibility and perception for judging each attribute, as recommended by Dutcoski (2007)DUTCOSKY SD. 2007. Análise Sensorial de Alimentos. Curitiba: Coleção Exatas, 4p..

During sensory analysis each strawberry cultivar was analyzed three times in each year season. Judges received three samples of five fruits of each cultivar, which were identified by code. Scores given on the QDA scale were converted into numerical scores and analyzed statistically to determine the samples preferences (Dutcoski, 2007DUTCOSKY SD. 2007. Análise Sensorial de Alimentos. Curitiba: Coleção Exatas, 4p.). This research in accordance to the ethical research on human beings was approved by the Ethics Committee of the Federal University of Paraná under the number 0950.075.10.06.

For mineral analysis, twenty fruits of each cultivar were randomly harvested in August 2011 and submitted to the analysis of calcium, potassium, manganese, magnesium, iron, copper and zinc, according to Martins & Reissman (2007)MARTINS APL; REISSMANN CB. 2007. Material vegetal e as rotinas laboratoriais nos procedimentos químico analíticos. Scientia Agraria 8: 1-17.. For these analyses, fruits were dehydrated in oven at 60°C during approximately five days and grounded in coffee grinder MDR301-Cadence, then a sub-sample of 1 g was extracted for calcination at 550°C and solubilization in 3 M HCl. Elements were determined with conventional atomic absorption spectrophotometer with air/acetylene flame.

Results were submitted to variance analysis and cultivars were compared to each other and within each season by Tukey 1%.

RESULTS AND DISCUSSION

All cultivars produced fruits during season 1 with higher soluble solids contents than those produced during season 2 (Table 1). This may be explained because plants kept in the field during more than 12 months (season 2) are less vigorous than those harvested sooner (Oliveira et al., 2006OLIVEIRA RP ; SCIVITTARO WB. 2008. Produção de morangueiro da cv. Camino Real em sistema de túnel. Revista Brasileira de Fruticultura 30: 681-684.). During season 1 'Albion' fruits showed the highest soluble solids content, followed by 'Monterrey'. During season 2 'Palomar' fruits kept this feature, followed by 'Albion' fruits (Table 1).

All strawberry cultivars, in both seasons, showed lower soluble solids content (Table 1) than those levels observed in other strawberry cultivars (Conti et al.,2002CONTI JH; MINAMI K; TAVARES FCA. 2002. Produção e qualidade de frutos de diferentes cultivares de morangueiro em ensaios conduzidos em Atibaia e Piracicaba. Horticultura Brasileira 20: 10-17.; Resende et al., 2008RESENDE JTV; CAMARGO LKP; ARGANDOÑA EJS; MARCHESE A; CAMARGO CK. 2008. Sensory analysis and chemical characterization of strawberry fruits. Horticultura Brasileira 26: 371-374.), and also none of them showed at least 7% soluble solids content, the minimum amount recommended for strawberry flavor acceptance (Kader, 1999KADER AA. 1999. Fruit maturity, ripening, and quality relationships. Acta Horticulturae 485: 203-208.).

All cultivars acidity, in both seasons, was higher than 0.8%, the maximum recommended for strawberry flavor acceptance (Kader, 1999KADER AA. 1999. Fruit maturity, ripening, and quality relationships. Acta Horticulturae 485: 203-208.). The high fruit acidity in season 1 can be attributed to the high summer temperatures and to the long days, condition under which plants emit stolon that, every two nodes (in general), emits new leaves and roots (Filgueira, 2008FILGUEIRA FAR. 2008. Novo Manual de olericultura. 3ª. ed., Viçosa: UFV. 421p.). The high acidity in season 2 can also be related to decreasing plant vigor (Oliveira et al., 2006OLIVEIRA RP; SCIVITTARO WB. 2006. Desempenho produtivo de mudas nacionais e importadas de morangueiro. Revista Brasileira de Fruticultura 28: 520-522.). 'Camino Real' and 'Palomar' showed during the season 1 the lowest levels of titratable acidity, and during the season 2 it was observed for 'Palomar' and 'Portola' fruits.

Due to the low sugar level and to the high acidity, no cultivar in any season (Table 1) reached the SS/AT of at least 8.75, value recommended for strawberry flavor acceptance (Kader, 1999KADER AA. 1999. Fruit maturity, ripening, and quality relationships. Acta Horticulturae 485: 203-208.). The high fruit acidity was probably the main factor compromising SS/AT, mainly in season 2 (Table 1), although the soluble solids content was also lower than recommended. Nevertheless, scientific studies show that 'Camino Real' and 'Albion' fruits can reach higher SS/AT [8.47 in 'Camino Real' (Camargo et al., 2011CAMARGO LKP; RESENDE JTAV; TOMINAGA TT; KURCHAIDT SM; CAMARGO CK; FIGUEIREDO AST. 2011. Postharvest quality of strawberry fruits produced in organic and conventional systems. Horticultura Brasileira 29: 577-583.); 9.13 in 'Camino Real' (Silva, 2011SILVA TP. 2011. Características produtivas e físico-químicas de frutos de morangueiro orgânico cultivado com o uso de extrato de algas. Curitiba: UFPR. 123p. (Dissertação mestrado).) and 16.26 in 'Albion' (Silva, 2011SILVA PA; ABREU CMP; ASMAR SA; CORREA AD. 2013. Quality evaluation of strawberries grown in the region of Lavras, Minas Gerais State. Acta Scientiarum 35: 777-782.)]. So, it is possible to assume that it is not recommended to keep strawberry plants in the field for more than 12 months, a usual technology applied in CMR. This statement is in agreement with the annual replanting recommendations, although this represents 24% of the production costs (Oliveira & Scivittaro, 2006OLIVEIRA RP ; SCIVITTARO WB. 2008. Produção de morangueiro da cv. Camino Real em sistema de túnel. Revista Brasileira de Fruticultura 30: 681-684.). The annual replanting recommendation prevents the accumulation of pests and diseases from one year to another (Oliveira et al., 2006OLIVEIRA RP; SCIVITTARO WB. 2006. Desempenho produtivo de mudas nacionais e importadas de morangueiro. Revista Brasileira de Fruticultura 28: 520-522.), and also certainly maintains plants vigorous. However, even with the low ratio (SS/AT), the local consumers buy these products routinely, clearly demonstrating the need for implementation of more sensory analysis to improve fruit quality.

Strawberry fruits with flesh firmness lower than 83.55 N are considered too soft, and when it is higher than 135.16 N are considered too firm (Conti et al., 2002CONTI JH; MINAMI K; TAVARES FCA. 2002. Produção e qualidade de frutos de diferentes cultivares de morangueiro em ensaios conduzidos em Atibaia e Piracicaba. Horticultura Brasileira 20: 10-17.). In this way, at season 1 all cultivars produced fruits considered too soft (Table 1). This parameter is very important because it affects the post-harvest shelf life and transport damage occurrence (Bieniasz et al., 2012BIENIASZ M, MAŁODOBRY M; DZIEDZIC E. 2012. The effect of foliar fertilization with calcium on quality of strawberry cultivars 'Luna' and 'Zanta'. Acta Horticulturae 926: 457-461.). These results may be due to high temperatures and high relative humidity in summer time (data not presented), which give fruits a less firm texture (Filgueira, 2008FILGUEIRA FAR. 2008. Novo Manual de olericultura. 3ª. ed., Viçosa: UFV. 421p.). Among all fruits harvested during season 1 'Albion' was that with softest firmness, and should be chosen with a lot of care, mainly when the product final destination is to distant markets.

All fruits showed lower C vitamin content during season 1 than during the season 2 (Table 1). This result can be explained because C vitamin is heat-labile, and easily oxidized if exposed to high temperature (Calegaro et al., 2002CALEGARO JM; PEZZI E; BENDER RJ. 2002. Utilização de atmosfera modificada na conservação de morangos em pós-colheita. Pesquisa Agropecuária Brasileira 37: 1049-1055.). Higher C vitamin content during the coldest season was also found in strawberry fruits by Pineli et al. (2012)PINELI LLO; MORETTI CL; RODRIGUES JSQ; FERREIRA DB; CHIARELLO MD. 2012. Variations in antioxidant properties of strawberries grown in Brazilian Savannah and harvested in different seasons. Journal of the Science of Food and Agriculture 92: 831-838.. 'Palomar' and 'Portola' fruits showed higher C vitamin content in both growing seasons (Table 1). This suggests that these cultivars can be promising when the cultivation purpose is focused on fruits antioxidant potential, such as verified in strawberry juices (Wan & Lin, 2003). C vitamin content was similar to the content found by Malgarim et al. (2006)MALGARIM MB; CANTILLANO RFF; COUTINHO EF. 2006. Sistemas e condições de colheita e armazenamento na qualidade de morangos cv. Camarosa. Revista Brasileira de Fruticultura 28: 185-189., and below to the values found by Rocha et al. (2008)ROCHA DA; ABREU CMP; CORRÊA AD; SANTOS CD; FONSECA EWN. 2008. Análise comparativa de nutrientes funcionais em morangos de diferentes cultivares da região de Lavras-MG. Revista Brasileira de Fruticultura 30: 1124-1128..

The physiological behavior of short-day strawberry cultivars is correlated with temperature and photoperiod, and as the photoperiod decreases, flowering and fruiting are stimulated (Filgueira, 2008FILGUEIRA FAR. 2008. Novo Manual de olericultura. 3ª. ed., Viçosa: UFV. 421p.). However, 'Camino Real' and 'Palomar' (both short-day cultivars) were not better than the day-neutral cultivars, grown during the season 2. This demonstrates the high day-neutral cultivars adaptation. Day-neutral cultivars grown during season 1 were expected to be better than short-day cultivars, but this did not occur (Table 1). Different cultivars performances within the same planting season can be explained by the genotypic components and its environment interaction. Local weather conditions, such as rain, light intensity, and temperature, probably affected the strawberry cultivar performance, as well as found by Pineli et al. (2012)PINELI LLO; MORETTI CL; RODRIGUES JSQ; FERREIRA DB; CHIARELLO MD. 2012. Variations in antioxidant properties of strawberries grown in Brazilian Savannah and harvested in different seasons. Journal of the Science of Food and Agriculture 92: 831-838..

Sweetness sensory scores were smaller than those assigned in other sensory attributes analyzed, and they were similar during the two growing seasons, from 5.50 to 6.48 (Table 2). Similar behavior was observed on fruit flavor, with scores ranging from 5.87 to 6.72. These results for sweetness and taste reflect the low soluble solids content (Table 1). It agrees with Resende et al. (2008)RESENDE JTV; CAMARGO LKP; ARGANDOÑA EJS; MARCHESE A; CAMARGO CK. 2008. Sensory analysis and chemical characterization of strawberry fruits. Horticultura Brasileira 26: 371-374. who evaluated strawberry cultivars ratios (SS/TA) and fruits consumer's acceptability. They observed that higher ratios (SS/TA) were associated with better fruit flavor perception.

Sensory analysis did not verify acidity differences between the two growing seasons (Table 2), such as was verified by chemical analysis (Table 1). As could be expected, scores assigned for this parameter (Table 2) were almost as low as those assigned to sweetness and flavor. This demonstrates that even though the local market consumes the product, it does not present a good acceptability.

Minimum differences were verified on the fruits aroma in both seasons (Table 2), but apparently there was a trend showing that this parameter was not so good evaluated in season 1 as it was in season 2. This may have occurred because fruit aroma comes from volatile compounds, which do not manifest themselves under low temperatures with such intensity, due to the lower plants metabolic activity during the cold season. This agrees with observations of Jouquand et al. (2008)JOUQUAND CE; CHANDLER C; PLOTTO A; GOODNER K. 2008. A sensory and chemical analysis of fresh strawberries over harvest dates and seasons reveals factors that affect eating quality. Journal of American Society of Horticultural Science 133: 859-867. that one of the factors affecting strawberry fruits aroma is the harvest season.

Cultivars showed similar fruit shape during the two growing seasons, except for 'Camino Real', harvested during season 2, which corresponds to the winter period (Table 2). Strawberry fruits shape depends on ovules fertilization, and their distribution around the receptacle. In order to obtain fruits without deformations, a uniform pollen distribution on stigmas is needed (Malagodi-Braga, 2002MALAGODI BRAGA KS. 2002. Estudo de agentes polinizadores em cultura de morango (Fragaria x ananassa). São Paulo: USP. 104p. (Tese doutorado).). This distribution can be made by pollinators. Insects absence during flowering period, associated with insufficient pollen amount, can result in fruit deformation (Chang et al., 2001CHANG YD; LEE MY; MAH Y. 2001. Pollination on strawberry in the vinyl house by Apis mellifera and A. cerana. Acta Horticulturae 561: 257-262.). Presumably the short amount of pollinator insects occurring during the winter season, combined with morphological 'Camino Real' features decreased the flower fertilization, causing fruits malformation and the worst sensory analysis.

Fruits produced during season 1 showed similar flesh firmness (Table 2). However, during season 2 'Palomar' fruits were worse than the others (Table 2). By comparing the analysis, carried out with the texture analyzer (Table 1) and the sensory analysis, a greater accuracy of the mechanical method comparing with sensory ability was identified. These results clearly demonstrate the importance of implementation of the sensory analysis along with the physico-chemical analysis, which in this situation did not reflect the consumer preference.

Mineral composition depends on the evaluated cultivar (Table 3), such as was observed by Tulipani et al. (2008)TULIPANI S; MEZZETTI B; CAPOCASA F; BOMPADRE S; BEEKWILDER J; VOS CH; CAPANOGLU E; BOVY A; BATTINO M. 2008. Antioxidants, phenolic compounds, and nutritional quality of different strawberry genotypes. Journal of Agricultural and Food Chemistry 56: 696-704. and Pineli et al. (2012)PINELI LLO; MORETTI CL; RODRIGUES JSQ; FERREIRA DB; CHIARELLO MD. 2012. Variations in antioxidant properties of strawberries grown in Brazilian Savannah and harvested in different seasons. Journal of the Science of Food and Agriculture 92: 831-838.. Under these conditions most nutrients were higher on 'Palomar' fruits except for iron (Fe) level, whose superiority was of 'Portola' fruits. Copper (Cu) was the only mineral that did not present significant differences among cultivars (Table 3). This information is very important when the purpose of strawberry production is its nutritional property (Rocha et al., 2008ROCHA DA; ABREU CMP; CORRÊA AD; SANTOS CD; FONSECA EWN. 2008. Análise comparativa de nutrientes funcionais em morangos de diferentes cultivares da região de Lavras-MG. Revista Brasileira de Fruticultura 30: 1124-1128.).

Potassium (K), calcium (Ca), iron (Fe), and manganese (Mn) levels (Table 3) were similar to those found in strawberry fruits by Wang & Lin (2003)WANG SW; LIN HS. 2003. Compost as a soil supplement increases the level of antioxidant compounds and oxygen radical absorbance capacity in strawberries. Journal of Agricultural and Food Chemistry 51: 6844-6850., and smaller than the values found in strawberry fruits by Rocha et al. (2008)ROCHA DA; ABREU CMP; CORRÊA AD; SANTOS CD; FONSECA EWN. 2008. Análise comparativa de nutrientes funcionais em morangos de diferentes cultivares da região de Lavras-MG. Revista Brasileira de Fruticultura 30: 1124-1128.. Zinc (Zn) level (Table 3) was lower than that found in strawberry fruits by Wang & Lin (2003)WANG SW; LIN HS. 2003. Compost as a soil supplement increases the level of antioxidant compounds and oxygen radical absorbance capacity in strawberries. Journal of Agricultural and Food Chemistry 51: 6844-6850. and Rocha et al. (2008)ROCHA DA; ABREU CMP; CORRÊA AD; SANTOS CD; FONSECA EWN. 2008. Análise comparativa de nutrientes funcionais em morangos de diferentes cultivares da região de Lavras-MG. Revista Brasileira de Fruticultura 30: 1124-1128.. This can be explained because the nutritional composition is multifactorial, i.e., it is affected by soil, weather, and/or genetic composition (Darolt, 2003DAROLT MR. 2003. Comparação da qualidade do alimento orgânico com o convencional. In: STRIGHETA PC; MUNIZ JN (eds). Alimentos orgânicos: produção, tecnologia e certificação, 1 ed. Viçosa: UFV.).

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