Phenolics and Antioxidant Activity of Green and Red Sweet Peppers from Organic and Conventional Agriculture: A Comparative Study

Nuno Rodrigues,José Alberto Pereira,António M Peres,Rosa Guilherme,Alfredo Aires

doi:10.3390/agriculture10120652

Abstract

Today, consumers are very concerned regarding food quality, nutritional composition and positive health effects of consumed foods. In this context, the preference and consumption of organic products has been increasing worldwide. In the present work, sweet peppers in two maturation stages (i.e., green and red peppers) from organic and conventional production systems were evaluated in regards to phenolic composition and antioxidant activity. Nine phenolic compounds were identified and quantified by a high-performance liquid chromatography-diode-array detector (HPLC-DAD), namely resveratrol, meta-coumaric acid, ortho-coumaric acid, clorogenic acid, caffeic acid, myricetin, rutin, luteolin-7-O-glucoside and quercitin-3-O-rhamnoside. In contrast to the production system, the maturation stage showed a pronounced significant effect on the phenolic composition of the studied sweet peppers; in general, green peppers possessed higher contents than red ones. Meta-coumaric acid, ortho-coumaric acid and quercitin-3-O-rhamnoside were more abundant in green conventional peppers and chlorogenic acid, caffeic acid and rutin were found in higher levels in red organic peppers. Regarding the antioxidant activity, green conventional peppers showed the highest DPPH, ABTS•+ and total reducing capacities, while red conventional peppers had higher TEAC values. Finally, principal component analysis showed that the phenolic composition together with the antioxidant capacities could be used to differentiate the production system and the maturation stage of sweet peppers. This finding confirmed that both factors influenced the peppers’ phenolic composition and antioxidant capacity, allowing their possible use as maturation–production biomarkers.

Highlights

Sweet pepper (Capsicum annuum L.), is one of the most popular and consumed vegetables around the world
Production system, fruits’ maturation stage, environmental-climatic conditions and post-harvest treatments significantly influence the peppers’ phenolic composition and contents, in general, the identified phenolics and respective levels found for the Entinas peppers were in-line with the wide range of values previously reported for other sweet pepper cultivars [16,19,20,21,23,25,26,27,37]
The opposite findings reported in the literature, together with those of the present study clearly show the difficulty in attempting to establish a priori the effects of the agronomic production system and/or maturation stage on the phenolic composition of sweet peppers, pointing out the relevance of factors such as cultivar, environmental-climatic conditions and post-harvest treatments

Summary

Introduction

Sweet pepper (Capsicum annuum L.), is one of the most popular and consumed vegetables around the world. There has been an increasing concern by consumers for healthier, safer and high-quality foods produced under environmentally friendly practices and economically fair modes. Consumers believe that organic products are of better quality, tastier, with high amounts of vitamins and other healthy compounds and are more nutritious, and these perceptions are the main driver of the observed increase in preference for organic products [5] This perception is usually related to the fact that the use of chemical fertilizers or synthetic plant protection products are not permitted in organic farming [6,7,8], being in-line with the reported higher levels of bioactive compounds reported for organic compared to conventional sweet peppers [8,9]

Methods

Results

Conclusion