Elsevier

Food and Chemical Toxicology

Volume 67, May 2014, Pages 139-144
Food and Chemical Toxicology

Organic versus conventional tomatoes: Influence on physicochemical parameters, bioactive compounds and sensorial attributes

https://doi.org/10.1016/j.fct.2014.02.018Get rights and content

Highlights

  • Organic and conventional redondo tomatoes were compared.

  • Extracts prepared from organic fruits exhibited higher antioxidant activity.

  • In conventionally produced tomatoes, lycopene was mainly concentrated in the pulp.

  • Peel and seeds of organic tomatoes contained high levels of bioactive compounds.

  • Organic farming improved the gustative properties of this tomato cultivar.

Abstract

The effect of organic and conventional agricultural systems on the physicochemical parameters, bioactive compounds content, and sensorial attributes of tomatoes (“Redondo” cultivar) was studied. The influence on phytochemicals distribution among peel, pulp and seeds was also accessed. Organic tomatoes were richer in lycopene (+20%), vitamin C (+30%), total phenolics (+24%) and flavonoids (+21%) and had higher (+6%) in vitro antioxidant activity. In the conventional fruits, lycopene was mainly concentrated in the pulp, whereas in the organic ones, the peel and seeds contained high levels of bioactive compounds. Only the phenolic compounds had a similar distribution among the different fractions of both types of tomatoes. Furthermore, a sensorial analysis indicated that organic farming improved the gustative properties of this tomato cultivar.

Introduction

In the last century, new agricultural technologies and the massive use of chemical fertilizers, pesticides and herbicides provided an increased productivity at lower prices. The abuse of such substances resulted in pollution and ecosystems imbalance, and several studies reported a causal relationship between their use and the increase of cancers and congenital disorders in humans (Gold et al., 2001, Sanborn et al., 2007).

In the last two decades, organic agriculture has been increasing in order to meet the demand of a growing number of consumers who are willing to pay more for food produced by environmentally friendly practices and without pesticide residues (Didier and Lucie, 2008). One question remains without a clear answer, however, and that is whether the organic management system really improves or not the nutritional and organoleptic characteristics of the products.

Several studies have pointed out a better quality of organic foods compared to those from conventional production. For example, in a meta-analysis that included 41 studies, Worthington (2001) concluded that organic products have higher vitamin C, iron, magnesium, and phosphorus contents and lower nitrate values. Magkos et al. (2001) reviewed that organically grown leafy vegetables and potatoes have higher levels of vitamin C. In addition, higher phytochemical content and total antioxidant activity was observed in organic oranges (Tarozzi et al., 2006) and higher levels of phenolic compounds were found in organic apples (Petkovsek et al., 2010) compared to the counterparts produced in integrated systems. In a comparative study carried out with two types of tomato (standard and cherry), Hallmann (2012) also found that organic fruits contained higher contents of total sugars, vitamin C and total flavonoids. In turn, Cwalina-Ambroziak and Amarowicz (2012) stated that the use of biological and fungicidal control agents was negatively correlated with the levels of carotenoids and phenolic compounds in tomato fruits.

Nevertheless, the scientific opinion is far from being consensual, since several studies claim that there is no differences between the nutritional quality of organically and conventionally produced foodstuffs. For instance, Cardoso et al. (2011) concluded that there was no evidence of nutritional superiority of organically grown fruits (acerola, strawberries and persimmon) regarding vitamin C and carotenoids contents. Also, Gravel et al. (2010) found little differences in what concerns to taste and nutritional value of organic and conventionally grown tomatoes in greenhouses.

There is no question that the consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria (Smith-Spangler et al., 2012), but given the number of contradictory results about the possible nutritional benefits, new data from controlled paired studies is essential to reach more conclusive results.

In this work, we sought to evaluate the effect of the cropping system (organic and conventional) on quality parameters (physicochemical properties, contents of bioactive compounds, antioxidant activity and organoleptic properties) of a Portuguese tomato cultivar (“Redondo”), which at present is produced almost exclusively by conventional means. As this tomato variety is widely appreciated by both home kitchen and industry of tomato-based products, the distribution of the nutrients among peel, pulp and seeds was also accessed.

Section snippets

Chemicals and reagents

2,6-Dichloroindophenol sodium salt hydrate, meta-phosphoric acid, gallic acid, catechin, Folin–Ciocalteu’s phenol reagent, DPPHradical dot (2,2-diphenyl-1-picrylhydrazyl radical), sodium nitrite, aluminium chloride, n-hexane, methanol, and acetone were all obtained from Sigma–Aldrich (St. Louis, USA). Anhydrous sodium carbonate, sodium hydroxide and absolute ethanol were purchased from Merck (Darmstadt, Germany). Ultrapure water was treated in a Milli-Q water purification system (Millipore, Bedford, MA,

Physicochemical parameters

The physicochemical parameters of organically and conventionally produced tomatoes are presented in Table 1: moisture (which influences texture, taste and appearance), water activity (a “free water” measure, and an important variable in assessing the propensity for spoilage due to bacterial, mold or yeast contamination), pH (that influences the fruit flavor, shelf life, and is used as a reliable indicator of its overall quality), total soluble solids (that are related to total sugars and,

Conclusions

The results of this study showed that, in a nutritional perspective, the organic tomatoes analyzed were healthier than those produced by conventional practices, presenting higher phytochemical contents and antioxidant activity. The agricultural system also influenced the nutrients distribution by the different parts of the fruits. The results of the sensory panel evaluation indicated that the highest pigmentation of the organic tomatoes does not guarantee the consumers’ preference. The

Conflict of Interest

The authors declare that there are no conflicts of interest.

Transparency Document

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Acknowledgments

R.C. Alves is grateful to FCT for a post-doctoral Grant (SFRH/BPD/68883/2010) financed by POPH-QREN-Tipologia 4.1-Formação Avançada, subsidized by FSE and MCTES. This work has been supported by FCT through Grant no. PEst-C/EQB/LA0006/2013 and QREN (NORTE-07-0124-FEDER-000069-CIÊNCIA DO ALIMENTO).

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