Fertilization in citrus is a cultural practice with great importance as it affects significantly  the  quality  of  fruit.  In  this  work  we  evaluated  the  effects  of  organic versus  conventional  farming  systems  on  internal  and  external  characteristics  of citrus, with particular emphasis on vitamin C content. The study was carried out in different orchards of the Algarve region, in the south of Portugal. Fruits of different orchards  were  harvested  at  physiological  maturity  and  submitted  to  physical  and chemical  analyses.  The  results  showed  that  mineral  fertilization  led  to  fruits  with greater  weight  and  diameter,  a  thicker  peel  and  a  more  intense  colour.  Compared with conventional production, fruits from organic farming had more soluble solids and  a  lower  maturation  index.  The  highest  concentrations  of  vitamin  C  were recorded in fruits from organic farming, but the response depended on species and cultivar

Caixeirinho, Dalila da Cruz

Duarte, Amílcar

Marreiros, António

Mendes, Maria

Miguel, Maria Graça

Nunes, Carla

Sustelo, V.

English

Universidade do Algarve

Vitamin C Content of Citrus from Conventional versus Organic 
Farming Systems 
 
A. Duarte,  D. Caixeirinho, M.G. Miguel, V. 
Sustelo and C. Nunes 
Universidade do Algarve, CDCTPV/FCT 
Edifício 8, Campus de Gambelas 
8005-139 Faro 
Portugal 
M. Mendes and A. Marreiros 
Direcção Regional de Agricultura e Pescas 
do Algarve 
Patacão, 8000 Faro 
Portugal 
 
Keywords: antioxidant activity, clementine, fruit quality, orange, organic farming, 
mandarin, lemon 
 
Abstract 
Fertilization in citrus is a cultural practice with great importance as it affects 
significantly the quality of fruit. In this work we evaluated the effects of organic 
versus conventional farming systems on internal and external characteristics of 
citrus, with particular emphasis on vitamin C content. The study was carried out in 
different orchards of the Algarve region, in the south of Portugal. Fruits of different 
orchards were harvested at physiological maturity and submitted to physical and 
chemical analyses. The results showed that mineral fertilization led to fruits with 
greater weight and diameter, a thicker peel and a more intense colour. Compared 
with conventional production, fruits from organic farming had more soluble solids 
and a lower maturation index. The highest concentrations of vitamin C were 
recorded in fruits from organic farming, but the response depended on species and 
cultivar. 
 
INTRODUCTION 
During the last century, trends in food production changed from local and small-
scale farms to large enterprises. Favoured by technological advances and economies of 
scale, large production systems turned to chemical solutions to control pests and diseases 
and increase soil productivity. These changes led to increased yield and external quality 
of horticultural products. However, pollution problems and food contamination by 
chemical substances became more frequent. Another consequence of this process was a 
greater dependence of farmers on prices of fuel, fertilizers and pesticides. 
Organic farming practices offered an alternative to industrial farming. Consumers, 
driven by environmental and health concerns encouraged this movement (Davies et al., 
1995) and caused an increased demand of organically-produced food. Surveys indicate 
that consumers consider organic food to be more positive for the environment and human 
health and more flavourful than their conventionally-grown counterparts (Bourn and 
Prescott, 2002). 
One of the reasons why consumers prefer organic products is their supposed 
greater nutritional quality. However, this is not a unanimous opinion. Taking into 
consideration the importance gained by organic farming, surprisingly little information is 
available about differences in quality between fruits and vegetables produced by these 
two management systems. Although several reviews are available on this topic (Woese et 
al., 1997; Brandt and Mølgaard, 2001; Worthington, 2001; Bourn and Prescott, 2002; 
Bordeleau et al., 2002; Raigon, 2007), the conclusions are far from coincident. Some of 
the authors did not find significant differences between conventional and organic products 
(Bourn and Prescott, 2002); while others concluded that food produced by organic 
farming had a greater quality, compared to that from conventional farming systems 
(Woese et al., 1997; Brandt and Mølgaard, 2001; Worthington, 2001; Bordeleau et al., 
2002; Raigon, 2007).  
The effect of the production system on fruit quality was already studied  in some 
citrus (Tarozzi et al., 2006; Lester et al., 2007; Pérez-López et al., 2007; Raigon, 2007; 
  389
Proc. VIth IS on Mineral Nutrition of Fruit Crops 
Eds.: M. Pestana and P.J. Correia 
Acta Hort. 868, ISHS 2010 
Beltrán-González et al., 2008). In general, citrus fruits produced in organic farms had 
greater juice percentage (Lester et al., 2007), and mineral (Ca, Mg, K, Na, Fe, Cu, Mn and 
Zn) concentration in the juice (Pérez-López et al., 2007) than those produced by 
conventional farming systems.  
If organic citrus were to have a greater vitamin C concentration, it might be an 
important factor to increase demand of fruits from this management system. Vitamin C 
may act as antioxidant or as agent that contributes to anticarcinogenic or cardioprotective 
properties (Rice-Evans et al., 1996; Rapisarda et al., 1999). Considering the relatively 
large consumption, citrus may be highlighted as an important source of vitamin C. This 
vitamin is also considered as a very important water-soluble antioxidant as it protects 
compounds in extracellular and intracellular spaces in most biological systems, and 
reduces tocopherol radicals back to their active form at the cellular membranes. It can 
also directly scavenge superoxide radicals, singlet oxygen, hydrogen peroxide and 
hydroxyl radicals (Kaur and Kapoor, 2001; Klimczak et al., 2007). 
A greater vitamin C content in citrus from organic compared with conventional 
farming systems was reported by Tarozzi et al. (2006) for the red orange cultivar 
‘Tarocco’, by Lester et al. (2007) for the grapefruit cultivar ‘Rio Red’ and by Raigón 
(2007) for the mandarin cultivars ‘Nules’ and ‘Okitsu’ and orange cultivars ‘Newhall’ 
and ‘Navelina’. In the present work, we compared 18 different citrus types grown either 
in organic or conventional (integrated) farming, under similar environmental conditions, 
to investigate the influence of species or cultivar on the response to these two 
management systems. 
 
MATERIALS AND METHODS 
Citrus analyzed were: ‘Valencia late’, ‘Baía’, ‘Dalmau’, ‘Newhall’, ‘Lanelate’ and 
‘Rohde’ oranges; ‘Fina’, ‘Hernandina’, ‘Fortune’, ‘Fremont’, Ortanique’, ‘Tangera’ 
‘Setubalense’, ‘Nules’ and ‘Nova’ mandarin or mandarin type cultivars; two hybrids 
between Citrus deliciosa and Citrus nobilis (‘Encore’ and ‘Wilking’) and the ‘Lisboa’ 
lemon.  Each cultivar was sampled in triplicate (at least 20 fruits per replicate), at 
commercial maturity, from an organic orchard and in a conventional orchard with 
integrated productions practices. Paired orchards were located close to each other, with 
trees grafted on the same rootstock and of about the same age to allow a valid comparison 
of organic versus conventional fruits. 
All orchards considered as organic farming were managed according to statutory 
European Union regulations regarding organic farming. In some organic orchards there 
was no application of fertilizers in the last five years, while in others fertilization was 
carried out with authorized fertilizers. In conventionally managed orchards, mineral 
fertilizers were applied all throughout the vegetative cycle of the trees. 
Fruit samples were submitted to physical and chemical analyses within 24 hours 
after harvest. Fruits were weighed and measured individually. Juice extraction was done 
by using a hand operated juice extractor. After extraction, juice was filtered and the sugar 
content and acidity were determined by refractometry and titration, respectively. Part of 
the filtered juice was immediately cooled and stored at -20ºC until ascorbic acid analyses 
were made. Ascorbic acid (vitamin C) was measured as described previously (Miguel et 
al., 2006), by HPLC (Beckman) equipped with a System Gold Programmable Detector 
Module 166-UV-Vis (Beckman Coulter, USA), using a Purospher RP-18 column (25 cm 
x 0.4 cm; 5 µm particle size). The mobile phase was 20 mM NaH2PO4 (pH 2.7 with orto-
phosphoric acid), with a flow rate of 1 ml/min. The volume of each injection was 20 µl. 
Detection was performed at 210 nm.   
The data were subjected to analysis of variance (ANOVA) and means were 
compared by using a t-test. 
 
RESULTS AND DISCUSSION 
The overall average of all cultivars showed that in general mineral fertilization 
provided a greater weight and diameter of the fruits, which had a thicker peel and a more 
 390 
intense colour (Table 1). Compared with conventional farming, fruits from organic 
farming were more acid and had a greater °Brix (Table 1). This may be explained, at least 
in part, by the fact that in some organic orchards there was no application of fertilizers for 
the last five years. However there are other factors  that may also affect the plant 
composition and consequently its nutritional value, such as genetic factors (plant crop and 
cultivar), environmental conditions (climate, soil type, structure and microbial 
populations), other management practices, postharvest methodologies, etc  (Woese et al., 
1997; Lee and Kader, 2000; Bourn and Prescott, 2002).  
Vitamin C (ascorbic acid) concentration in the juice was generally higher in fruits 
produced in the organic orchards (Table 1).  However, this difference was not detected in 
all citrus cultivars included in this study. In ‘Valencia late’ and ‘Baía’ oranges the 
concentration of ascorbic acid was higher in the juice of the fruits from organic farming, 
but in other orange cultivars (‘Dalmau’, ‘Newhall’, ‘Lanelate’ and ‘Rohde’) no 
differences were detected between the fruits from different production systems (Fig. 1). 
Some of the mandarin or mandarin type cultivars (‘Fina’, ‘Hernandina’, ‘Fortune’, 
‘Fremont’, Ortanique’ and ‘Tangera’) had higher ascorbic acid concentration in the 
organic farming fruits, but in the two hybrids between Citrus deliciosa and Citrus nobilis 
(‘Encore’ and ‘Wilking’) the opposite was true. No statistically significant differences 
were detected in ‘Setubalense’, ‘Nules’ and ‘Nova’ mandarins, as well as in ‘Lisboa’ 
lemon. Our results do not contradict those obtained previously with ‘Rio Red’ grapefruit 
and ‘Tarocco’ red oranges, but show that enhanced vitamin C content is not always 
associated with organic farming, but depends strongly on citrus species and cultivar.  
Carbonaro et al. (2002) found an increase in ascorbic acid content in peaches from 
organic farming but no differences were found in pear, showing that this observation may 
be valid for other types of fruit.  
Under soil, climate and agronomic conditions of the Algarve, our results show the 
citrus cultivars which are better producers of vitamin C when grown in organic farming. 
 
CONCLUSIONS 
Compared with conventional production, fruits from organic farming had more 
soluble solids and a lower maturation index. The highest concentrations of vitamin C 
were recorded in fruits from organic farming, but the response depended on species and 
cultivar. 
 
ACKNOWLEDGEMENTS 
Thanks to Qta da Figueirinha, Qta da Barragoa, FRUTALGARVE and CITRIPOR 
for providing the fruits. We thank also Dr. Denise Martins for technical support. This 
work was supported by two research projects: Agro nº282 – Horticulture in Organic 
farming; Interreg III – CITRISAUDE SP5, P120/03 - Cooperação Transfronteiriça 
"Citrisaude – New post-harvest technologies to improve quality and safety in citrus". 
 
Literature Cited 
Beltrán-González, F., Pérez-López, A.J., López-Nicolás, J.M. and Carbonell-Barrachina, 
A.A. 2008. Effects of Agricultural Practices on Instrumental Colour, Mineral Content, 
Carotenoid Composition, and Sensory Quality of Mandarin Orange Juice, cv. 
Hernandina. J. Sci. Food Agric. 88:1731-1738. 
Bordeleau, G., Myers-Smith, I., Midak, M. and Szeremeta, A. 2002. Food Quality: A 
Comparison of Organic and Conventional Fruits and Vegetables. Ecological 
Agriculture - Den Kongelige Veterinoer- og Landbohøjskole, Dinamarca.  
Bourn, D. and Prescott, J. 2002. A Comparison of the Nutritional Value, Sensory 
Qualities, and Food Safety of Organically and Conventionally Produced Foods. Crit. 
Rev. Food Sci. 42:1-34. 
Brandt, K. and Mølgaard, J.P. 2001. Organic Agriculture: Does it Enhance or Reduce the 
Nutritional Value of Plant Foods?. J. Sci. Food Agric. 81:924-931. 
Carbonaro, M., Mattera, M., Nicoli, S., Bergamo, P. and Cappelloni, M. 2002. 
  391
Modulation of antioxidant compounds in organic vs conventional fruit peach (Prunus 
persica L.), and pear (Pyrus communis L.). J. Agric. Food Chem. 50:5458-5462. 
Davies, A., Titterington, A.J. and Cochrane, C. 1995. Who buys organic food? A Profile 
of the Purchasers of Organic food in Northern Ireland. Brit. Food J. 97:17-23. 
Kaur, C.H. and Kapoor, H.C. 2001. Antioxidants in fruits and vegetables-the 
millennium’s health. Int. J. Food Sci. Technol. 36:703-725. 
Klimczak, I., Małecka, M., Szlachta, M. and Gliszczyńska-Świgło, A. 2007. Effect of 
storage on the content of polyphenols, vitamin C and the antioxidant activity of orange 
juices. J. Food Compos. Anal. 20:313-322. 
Lee, S.K. and Kader, A.A. 2000. Preharvest and postharvest factors influencing vitamin C 
content of horticultural crops. Postharvest Biol. Tec. 20:207-220. 
Lester, G.E., Manthley, J.A. and Buslig, B.S. 2007. Organic vs Conventionally Grown 
Rio Red Whole Grapefruit and Juice: Comparison of Production Inputs, Market 
Quality, Consumer Acceptance, and Human Health-Bioactive Compounds. J. Agric. 
Food Res. 55:4474-4480. 
Miguel, G., Fontes, C., Martins, D., Neves, A. and Antunes, D. 2006. Effects of post-
harvest treatment and storage time on the organic acid content in Assaria and Mollar 
pomegranate (Punica granatum L.) fruit. Ital. J. Food Sci. 18:317-322. 
Pérez-López, A.J., López-Nicolás, J.M. and Carbonell-Barrachina, A.A. 2007. Effects of 
Organic Farming on Minerals Contents and Aroma Composition of Clemenules 
Mandarin Juice, European Food Res. Technol. 225:255-260. 
Raigón, M.D. 2007. Alimentos ecológicos, calidad y salud. Junta de Andalucía: 
Consejería de Agricultura y Pesca, Sociedad Española de Agricultura Ecológica 
(SEAE), Sevilla. 
Rapisarda, P., Tomaino, A., Lo Cascio, R., Bonina, F., de Pasquale, A. and Saija, A. 
1999. Antioxidant effectiveness as influenced by phenolic content of fresh orange 
juices. J. Agric. Food Chem. 47:4718-4723. 
Rice-Evans, C., Miller, N.J. and Paganga, G. 1996. Structure-antioxidant activity 
relationships of flavonoids and phenolic acids. Free Rad. Biol. Med. 20:933-956. 
Tarrozi, A., Hrelia, S., Angeloni, C., Morroni, F., Biaggi, P., Guardigli, M., Cantelli-Forti, 
G. and Hrelia, P. 2006. Antioxidant effectiveness of organically and non-organically 
grown red oranges in cell culture systems. Eur. J. of Nutr. 45:152-158. 
Woese, K., Lange, D., Boess, C. and Boegl, K.W. 1997. A comparison of organically and 
conventionally grown foods – results of a review of the relevant literature, J. Sci. Food 
Agric. 74:281-293. 
Worthignton, V. 2001. Nutritional quality of organic versus conventional fruits, 
vegetables and grains. J. Altern. Complem. Med. 7:161-173. 
 
 392 
 
Tables 
 
 
 
 
 
 
 
 
 
Table 1. Effect of organic versus conventional farming on the quality of citrus fruit. 
 
 Organic Conventional Level of 
Significance 
Fruit weight (g) 123.2 146.7 P≤0.01 
Fruit equatorial diameter (mm) 60.1 64.4 P≤0.01 
Fruit longitudinal diameter (mm) 56.9 60.9 P≤0.01 
Peel thickness (mm) 2.9 3.5 P≤0.01 
Juice percentage 41.2 41.6 NS 
Fruit colour:    
L 61.5 58.9 P≤0.01 
a 23.8 26.6 P≤0.01 
b 33.8 32.4 P≤0.01 
Citrus colour index (CCI) 12.1 14.8 P≤0.01 
SSC (ºBrix) 10.3 8.9 P≤0.01 
Juice titratable acidity (ml of citric acid/100 
ml) 0.82 0.70 P≤0.01 
Juice pH 3.70 3.79 P≤0.01 
Maturity index 16.7 19.1 P≤0.01 
Juice ascorbic acid (mg/100 ml) 40.6 32.4 P≤0.01 
NS- not significant. 
 
  393
 
Figures 
 
 
0 10 20 30 40 50 60 70 80 90
All cultivars
Lisboa
Tangera
Ortanique
Nova
Fremont
Fortune
Encore
Wilking
Hernandina
Nules
Fina
Tang. Setubalense
Rohde
Lanelate
Newhall
Baía 
Dalmau 
Valencia late
**
NS
**
*
NS
**
**
*
**
*
NS
*
NS
NS
NS
NS
*
NS
**
Ascorbic acid (mg/100 ml)
Organic management
Conventional management
 
 
Fig. 1. Effect of organic versus conventional farming on the ascorbic acid concentration 
in juices of different citrus cultivars. NS - not significant; * and ** - significantly 
different at P ≤ 0.05 and P ≤ 0.01, respectively. 
 
 394 


Vitamin C content of citrus from conventional versus organic farming systems

Fertilization in citrus is a cultural practice with great importance as it affects significantly  the  quality  of  fruit.  In  this  work  we  evaluated  the  effects  of  organic versus  conventional  farming  systems  on  internal  and  external  characteristics  of citrus, with particular emphasis on vitamin C content. The study was carried out in different orchards of the Algarve region, in the south of Portugal. Fruits of different orchards  were  harvested  at  physiological  maturity  and  submitted  to  physical  and chemical  analyses.  The  results  showed  that  mineral  fertilization  led  to  fruits  with greater  weight  and  diameter,  a  thicker  peel  and  a  more  intense  colour.  Compared with conventional production, fruits from organic farming had more soluble solids and  a  lower  maturation  index.  The  highest  concentrations  of  vitamin  C  were recorded in fruits from organic farming, but the response depended on species and cultivar.Interreg  III  –  CITRISAUDE  SP5,  P120/03  -  Cooperação  Transfronteiriça  "Citrisaude – New post-harvest technologies to improve quality and safety in citrus"; Agro nº282 – Horticulture in Organic farmin

Sapientia

Vitamin C Content of Citrus from Conventional versus Organic Farming Systems  A. Duarte,  D. Caixeirinho, M.G. Miguel, V. Sustelo and C. Nunes Universidade do Algarve, CDCTPV/FCT Edifício 8, Campus de Gambelas 8005-139 Faro Portugal M. Mendes and A. Marreiros Direcção Regional de Agricultura e Pescas do Algarve Patacão, 8000 Faro Portugal  Keywords: antioxidant activity, clementine, fruit quality, orange, organic farming, mandarin, lemon  Abstract Fertilization in citrus is a cultural practice with great importance as it affects significantly the quality of fruit. In this work we evaluated the effects of organic versus conventional farming systems on internal and external characteristics of citrus, with particular emphasis on vitamin C content. The study was carried out in different orchards of the Algarve region, in the south of Portugal. Fruits of different orchards were harvested at physiological maturity and submitted to physical and chemical analyses. The results showed that mineral fertilization led to fruits with greater weight and diameter, a thicker peel and a more intense colour. Compared with conventional production, fruits from organic farming had more soluble solids and a lower maturation index. The highest concentrations of vitamin C were recorded in fruits from organic farming, but the response depended on species and cultivar.  INTRODUCTION During the last century, trends in food production changed from local and small-scale farms to large enterprises. Favoured by technological advances and economies of scale, large production systems turned to chemical solutions to control pests and diseases and increase soil productivity. These changes led to increased yield and external quality of horticultural products. However, pollution problems and food contamination by chemical substances became more frequent. Another consequence of this process was a greater dependence of farmers on prices of fuel, fertilizers and pesticides. Organic farming practices offered an alternative to industrial farming. Consumers, driven by environmental and health concerns encouraged this movement (Davies et al., 1995) and caused an increased demand of organically-produced food. Surveys indicate that consumers consider organic food to be more positive for the environment and human health and more flavourful than their conventionally-grown counterparts (Bourn and Prescott, 2002). One of the reasons why consumers prefer organic products is their supposed greater nutritional quality. However, this is not a unanimous opinion. Taking into consideration the importance gained by organic farming, surprisingly little information is available about differences in quality between fruits and vegetables produced by these two management systems. Although several reviews are available on this topic (Woese et al., 1997; Brandt and Mølgaard, 2001; Worthington, 2001; Bourn and Prescott, 2002; Bordeleau et al., 2002; Raigon, 2007), the conclusions are far from coincident. Some of the authors did not find significant differences between conventional and organic products (Bourn and Prescott, 2002); while others concluded that food produced by organic farming had a greater quality, compared to that from conventional farming systems (Woese et al., 1997; Brandt and Mølgaard, 2001; Worthington, 2001; Bordeleau et al., 2002; Raigon, 2007).  The effect of the production system on fruit quality was already studied  in some citrus (Tarozzi et al., 2006; Lester et al., 2007; Pérez-López et al., 2007; Raigon, 2007;   389Proc. VIth IS on Mineral Nutrition of Fruit Crops Eds.: M. Pestana and P.J. Correia Acta Hort. 868, ISHS 2010 Beltrán-González et al., 2008). In general, citrus fruits produced in organic farms had greater juice percentage (Lester et al., 2007), and mineral (Ca, Mg, K, Na, Fe, Cu, Mn and Zn) concentration in the juice (Pérez-López et al., 2007) than those produced by conventional farming systems.  If organic citrus were to have a greater vitamin C concentration, it might be an important factor to increase demand of fruits from this management system. Vitamin C may act as antioxidant or as agent that contributes to anticarcinogenic or cardioprotective properties (Rice-Evans et al., 1996; Rapisarda et al., 1999). Considering the relatively large consumption, citrus may be highlighted as an important source of vitamin C. This vitamin is also considered as a very important water-soluble antioxidant as it protects compounds in extracellular and intracellular spaces in most biological systems, and reduces tocopherol radicals back to their active form at the cellular membranes. It can also directly scavenge superoxide radicals, singlet oxygen, hydrogen peroxide and hydroxyl radicals (Kaur and Kapoor, 2001; Klimczak et al., 2007). A greater vitamin C content in citrus from organic compared with conventional farming systems was reported by Tarozzi et al. (2006) for the red orange cultivar ‘Tarocco’, by Lester et al. (2007) for the grapefruit cultivar ‘Rio Red’ and by Raigón (2007) for the mandarin cultivars ‘Nules’ and ‘Okitsu’ and orange cultivars ‘Newhall’ and ‘Navelina’. In the present work, we compared 18 different citrus types grown either in organic or conventional (integrated) farming, under similar environmental conditions, to investigate the influence of species or cultivar on the response to these two management systems.  MATERIALS AND METHODS Citrus analyzed were: ‘Valencia late’, ‘Baía’, ‘Dalmau’, ‘Newhall’, ‘Lanelate’ and ‘Rohde’ oranges; ‘Fina’, ‘Hernandina’, ‘Fortune’, ‘Fremont’, Ortanique’, ‘Tangera’ ‘Setubalense’, ‘Nules’ and ‘Nova’ mandarin or mandarin type cultivars; two hybrids between Citrus deliciosa and Citrus nobilis (‘Encore’ and ‘Wilking’) and the ‘Lisboa’ lemon.  Each cultivar was sampled in triplicate (at least 20 fruits per replicate), at commercial maturity, from an organic orchard and in a conventional orchard with integrated productions practices. Paired orchards were located close to each other, with trees grafted on the same rootstock and of about the same age to allow a valid comparison of organic versus conventional fruits. All orchards considered as organic farming were managed according to statutory European Union regulations regarding organic farming. In some organic orchards there was no application of fertilizers in the last five years, while in others fertilization was carried out with authorized fertilizers. In conventionally managed orchards, mineral fertilizers were applied all throughout the vegetative cycle of the trees. Fruit samples were submitted to physical and chemical analyses within 24 hours after harvest. Fruits were weighed and measured individually. Juice extraction was done by using a hand operated juice extractor. After extraction, juice was filtered and the sugar content and acidity were determined by refractometry and titration, respectively. Part of the filtered juice was immediately cooled and stored at -20ºC until ascorbic acid analyses were made. Ascorbic acid (vitamin C) was measured as described previously (Miguel et al., 2006), by HPLC (Beckman) equipped with a System Gold Programmable Detector Module 166-UV-Vis (Beckman Coulter, USA), using a Purospher RP-18 column (25 cm x 0.4 cm; 5 µm particle size). The mobile phase was 20 mM NaH2PO4 (pH 2.7 with orto-phosphoric acid), with a flow rate of 1 ml/min. The volume of each injection was 20 µl. Detection was performed at 210 nm.   The data were subjected to analysis of variance (ANOVA) and means were compared by using a t-test.  RESULTS AND DISCUSSION The overall average of all cultivars showed that in general mineral fertilization provided a greater weight and diameter of the fruits, which had a thicker peel and a more  390 intense colour (Table 1). Compared with conventional farming, fruits from organic farming were more acid and had a greater °Brix (Table 1). This may be explained, at least in part, by the fact that in some organic orchards there was no application of fertilizers for the last five years. However there are other factors  that may also affect the plant composition and consequently its nutritional value, such as genetic factors (plant crop and cultivar), environmental conditions (climate, soil type, structure and microbial populations), other management practices, postharvest methodologies, etc  (Woese et al., 1997; Lee and Kader, 2000; Bourn and Prescott, 2002).  Vitamin C (ascorbic acid) concentration in the juice was generally higher in fruits produced in the organic orchards (Table 1).  However, this difference was not detected in all citrus cultivars included in this study. In ‘Valencia late’ and ‘Baía’ oranges the concentration of ascorbic acid was higher in the juice of the fruits from organic farming, but in other orange cultivars (‘Dalmau’, ‘Newhall’, ‘Lanelate’ and ‘Rohde’) no differences were detected between the fruits from different production systems (Fig. 1). Some of the mandarin or mandarin type cultivars (‘Fina’, ‘Hernandina’, ‘Fortune’, ‘Fremont’, Ortanique’ and ‘Tangera’) had higher ascorbic acid concentration in the organic farming fruits, but in the two hybrids between Citrus deliciosa and Citrus nobilis (‘Encore’ and ‘Wilking’) the opposite was true. No statistically significant differences were detected in ‘Setubalense’, ‘Nules’ and ‘Nova’ mandarins, as well as in ‘Lisboa’ lemon. Our results do not contradict those obtained previously with ‘Rio Red’ grapefruit and ‘Tarocco’ red oranges, but show that enhanced vitamin C content is not always associated with organic farming, but depends strongly on citrus species and cultivar.  Carbonaro et al. (2002) found an increase in ascorbic acid content in peaches from organic farming but no differences were found in pear, showing that this observation may be valid for other types of fruit.  Under soil, climate and agronomic conditions of the Algarve, our results show the citrus cultivars which are better producers of vitamin C when grown in organic farming.  CONCLUSIONS Compared with conventional production, fruits from organic farming had more soluble solids and a lower maturation index. The highest concentrations of vitamin C were recorded in fruits from organic farming, but the response depended on species and cultivar.  ACKNOWLEDGEMENTS Thanks to Qta da Figueirinha, Qta da Barragoa, FRUTALGARVE and CITRIPOR for providing the fruits. We thank also Dr. Denise Martins for technical support. This work was supported by two research projects: Agro nº282 – Horticulture in Organic farming; Interreg III – CITRISAUDE SP5, P120/03 - Cooperação Transfronteiriça "Citrisaude – New post-harvest technologies to improve quality and safety in citrus".  Literature Cited Beltrán-González, F., Pérez-López, A.J., López-Nicolás, J.M. and Carbonell-Barrachina, A.A. 2008. Effects of Agricultural Practices on Instrumental Colour, Mineral Content, Carotenoid Composition, and Sensory Quality of Mandarin Orange Juice, cv. Hernandina. J. Sci. Food Agric. 88:1731-1738. Bordeleau, G., Myers-Smith, I., Midak, M. and Szeremeta, A. 2002. Food Quality: A Comparison of Organic and Conventional Fruits and Vegetables. Ecological Agriculture - Den Kongelige Veterinoer- og Landbohøjskole, Dinamarca.  Bourn, D. and Prescott, J. 2002. A Comparison of the Nutritional Value, Sensory Qualities, and Food Safety of Organically and Conventionally Produced Foods. Crit. Rev. Food Sci. 42:1-34. Brandt, K. and Mølgaard, J.P. 2001. Organic Agriculture: Does it Enhance or Reduce the Nutritional Value of Plant Foods?. J. Sci. Food Agric. 81:924-931. Carbonaro, M., Mattera, M., Nicoli, S., Bergamo, P. and Cappelloni, M. 2002.   391Modulation of antioxidant compounds in organic vs conventional fruit peach (Prunus persica L.), and pear (Pyrus communis L.). J. Agric. Food Chem. 50:5458-5462. Davies, A., Titterington, A.J. and Cochrane, C. 1995. Who buys organic food? A Profile of the Purchasers of Organic food in Northern Ireland. Brit. Food J. 97:17-23. Kaur, C.H. and Kapoor, H.C. 2001. Antioxidants in fruits and vegetables-the millennium’s health. Int. J. Food Sci. Technol. 36:703-725. Klimczak, I., Małecka, M., Szlachta, M. and Gliszczyńska-Świgło, A. 2007. Effect of storage on the content of polyphenols, vitamin C and the antioxidant activity of orange juices. J. Food Compos. Anal. 20:313-322. Lee, S.K. and Kader, A.A. 2000. Preharvest and postharvest factors influencing vitamin C content of horticultural crops. Postharvest Biol. Tec. 20:207-220. Lester, G.E., Manthley, J.A. and Buslig, B.S. 2007. Organic vs Conventionally Grown Rio Red Whole Grapefruit and Juice: Comparison of Production Inputs, Market Quality, Consumer Acceptance, and Human Health-Bioactive Compounds. J. Agric. Food Res. 55:4474-4480. Miguel, G., Fontes, C., Martins, D., Neves, A. and Antunes, D. 2006. Effects of post-harvest treatment and storage time on the organic acid content in Assaria and Mollar pomegranate (Punica granatum L.) fruit. Ital. J. Food Sci. 18:317-322. Pérez-López, A.J., López-Nicolás, J.M. and Carbonell-Barrachina, A.A. 2007. Effects of Organic Farming on Minerals Contents and Aroma Composition of Clemenules Mandarin Juice, European Food Res. Technol. 225:255-260. Raigón, M.D. 2007. Alimentos ecológicos, calidad y salud. Junta de Andalucía: Consejería de Agricultura y Pesca, Sociedad Española de Agricultura Ecológica (SEAE), Sevilla. Rapisarda, P., Tomaino, A., Lo Cascio, R., Bonina, F., de Pasquale, A. and Saija, A. 1999. Antioxidant effectiveness as influenced by phenolic content of fresh orange juices. J. Agric. Food Chem. 47:4718-4723. Rice-Evans, C., Miller, N.J. and Paganga, G. 1996. Structure-antioxidant activity relationships of flavonoids and phenolic acids. Free Rad. Biol. Med. 20:933-956. Tarrozi, A., Hrelia, S., Angeloni, C., Morroni, F., Biaggi, P., Guardigli, M., Cantelli-Forti, G. and Hrelia, P. 2006. Antioxidant effectiveness of organically and non-organically grown red oranges in cell culture systems. Eur. J. of Nutr. 45:152-158. Woese, K., Lange, D., Boess, C. and Boegl, K.W. 1997. A comparison of organically and conventionally grown foods – results of a review of the relevant literature, J. Sci. Food Agric. 74:281-293. Worthignton, V. 2001. Nutritional quality of organic versus conventional fruits, vegetables and grains. J. Altern. Complem. Med. 7:161-173.   392  Tables          Table 1. Effect of organic versus conventional farming on the quality of citrus fruit.   Organic Conventional Level of Significance Fruit weight (g) 123.2 146.7 P≤0.01 Fruit equatorial diameter (mm) 60.1 64.4 P≤0.01 Fruit longitudinal diameter (mm) 56.9 60.9 P≤0.01 Peel thickness (mm) 2.9 3.5 P≤0.01 Juice percentage 41.2 41.6 NS Fruit colour:    L 61.5 58.9 P≤0.01 a 23.8 26.6 P≤0.01 b 33.8 32.4 P≤0.01 Citrus colour index (CCI) 12.1 14.8 P≤0.01 SSC (ºBrix) 10.3 8.9 P≤0.01 Juice titratable acidity (ml of citric acid/100 ml) 0.82 0.70 P≤0.01 Juice pH 3.70 3.79 P≤0.01 Maturity index 16.7 19.1 P≤0.01 Juice ascorbic acid (mg/100 ml) 40.6 32.4 P≤0.01 NS- not significant.    393 Figures   0 10 20 30 40 50 60 70 80 90All cultivarsLisboaTangeraOrtaniqueNovaFremontFortuneEncoreWilkingHernandinaNulesFinaTang. SetubalenseRohdeLanelateNewhallBaía Dalmau Valencia late**NS***NS********NS*NSNSNSNS*NS**Ascorbic acid (mg/100 ml)Organic managementConventional management  Fig. 1. Effect of organic versus conventional farming on the ascorbic acid concentration in juices of different citrus cultivars. NS - not significant; * and ** - significantly different at P ≤ 0.05 and P ≤ 0.01, respectively.   394 

https://sapientia.ualg.pt/bitstream/10400.1/1158/1/2010-ISHS-VitaminC%20Content%20of%20Citrus%20from%20Conventional%20versus%20Organic%20Farming.pdf

Vitamin C content of citrus from conventional versus organic farming systems

Abstract

Similar works

Full text

Available Versions

Universidade do Algarve

Sapientia