Effect of crop management practices (organic, “low input” and conventional) on the nutritional quality of foods
This workpackage address deficiencies in knowledge in several areas
Nutritional composition (beneficial components)
There is extensive consensus that whole grain cereals and in particular fresh vegetables and fruit are important for human health, and that their dietary intake should be increased. However, there is less knowledge about the relative nutritional importance of particular plant-compounds, in the context of typical European diets.
Cereal and vegetables contribute substantially to satisfying the recommended dietary intake of some essential minerals (Ca, Mg, Fe, Se, Cu, Zn, etc.) and vitamins (notably vitamin C, beta-carotene, folate). It has also been shown that supplementation with the same compounds in form of pills does not provide the same benefits to health as increasing the intake of the plant foods.
It is known that vegetable crops contain particular secondary metabolites (e.g. phenolics, glucosinolates, other organic sulphur compounds, sesquiterpene lactones, fructans), which have shown beneficial pharmacological properties such as anti-neoplasia, antioxidant, anti-allergic effects, platelet aggregation inhibition, interference with cancer promotion mechanisms and probiotic activity. These compounds are therefore thought to be involved in the well-documented beneficial effects of vegetable consumption on health. However, there is little knowledge about the relative nutritional value of individual compounds in plant foods, when they are eaten as part of a typical European diet. Many of these compounds are also important for the sensory quality of fruit and vegetables, in particular the secondary metabolites, which define characteristic flavours, aromas and colours of each product.
Nutritional composition (deletrious components)
Cereals and vegetables also contribute significantly to the intake of a range of undesired compounds, which are considered hazardous if consumed in too high quantities. This includes nitrate (> 60% of which are taken up with cereals and vegetables), heavy metals (e.g. lead and cadmium), pesticide residues and mycotoxins. Some secondary metabolites are also known to function as toxicants when they occur in too high concentrations, e.g. glycoalkaloids, glucosinolates and polyacetylenes.
Effects of organic vs conventional farming on nutritional and sensory aspects
There is considerable sample-to-sample variation in the content of many of the compounds mentioned above. Several hypotheses have been published on how the production system, in particular organic farming as compared with conventional farming, could affect nutritional value and/or other qualities.
Several studies and reviews indicate systematic differences in sensory and technical quality, and in concentrations of minerals, essential amino acids, vitamins, secondary metabolites and mycotoxins in crops produced from different production systems (conventional, “low input” and/or organic) or specific components (e.g. fertility practices) of such systems.
Other studies report no significant differences or inconsistent results. However, many of these studies did not use organic and conventional samples matched for potentially confounding factors such as variety, area of origin, agronomic practices, soil and climatic conditions during production and/or length of storage. These factors are known to affect the chemical composition of crops.
From the currently available information, it is therefore not possible to conclude to what extent variation in production system or in specific components of production systems may affect the content of nutritionally relevant compounds in crops.
We will address the deficiencies in knowledge (described above) by carrying out the following studies (sub-workpackages) using a unique long-term, replicated, multi-factorial field experiment:
WP 2.1.1 to WP2.1.6: Effect of management practices (conventional, “low input” and organic) on the composition of nutritionally relevant compounds and sensory quality of crops
This experiment will involve growing wheat (WP2.1.1), potato (WP2.1.2), cabbage (WP2.1.3), onion (WP2.1.4) and iceberg lettuce (WP2.1.5) under 4 different production systems (organic, 2x low input, and conventional) in an experimental design which allows estimation of the interactions between rotational positioning, crop protection and fertility management protocols used in such systems.
All crops will be analysed for contents of relevant minerals, vitamins and pesticide residues. In addition, each crop will be analysed for characteristic secondary metabolites and/or mycotoxins with known or suspected relevance for health and/or sensory quality (WP2.1.6).
Based on the results from the chemical analysis, relevant treatments will be selected for evaluation of sensory/technical quality, consisting of a sensory evaluation of fresh (where appropriate) and/or one or two processed typical foods made from the crop (WP2.1.6). Additionally, for wheat and potato, material from the selected treatments will be compared in a rat preference test (WP2.1.6).
One field experiment will be performed. It was not possible to run a series of such field experiments in different European regions and climatic zones. However, information confirming the principal conclusions from WP2.1 in different European regions is expected to come from analysing selected crop samples from subproject 3 investigations into “alternative fertility management and crop protection strategies” for nutritional and sensory quality under workpackage 2.1.6 (see Fig. 2.3 for the integration of WP2.1 with SPs3,4,5&6).
Under Subproject 3 data on fertility management, yields and soil chemistry from WPs 2.1.1 to 2.1.5 will be used to validate and improve existing decision support systems for fertility management (e.g. Natural Farming Software, Durham; systems developed in the EUROTATE_N project QLRT-2001-01100) focused on predicting nitrate leaching and/or fertility input needs for organic and “low input” farming systems (see also WP3.1 and WP3.3).