Facts and Myths of Feeding the World with Organic Farming Methods - Principles of Sustainable Soil Management in Agroecosystems - page 95

basis to support their views. Studies about organic food nutrition started soon after
organic farming came into being. Woese et al. (1997) reviewed numerous studies
that had been published dating back to 1924. More recently, several reviews of com-
parative studies have been published (Worthington 2001; Williams 2002; Magkos et
al. 2003). Since then, more studies on organic food quality had been published, and
meta-analysis provided better comparisons. Meta-analysis is a statistical technique
for combining the findings from independent studies, the validity of which is highly
dependent on the quality systematic review. As more studies on organic food qual-
ity had become available in the past decade, meta-analysis was used more often in
organic food quality reviews to give complete coverage of available studies.
Numerous research studies have been conducted on organic food quality. However,
there is a major challenge on how to define food quality concepts and methods for
determination (Kahl et al. 2012). The concepts of food quality and evaluation meth-
ods developed as the knowledge of food science expanded and new measuring tech-
nology became available. Now, sensitivity of analytical methods to measure nutrients
has been increased. Taking plant-based organic food as an example, most of the early
studies only evaluated dry matter, total sugars, and mineral contents. Secondary
metabolites, with the exception of vitamin C and polyphenolic substances, were sel-
dom included in these studies (Worthington 2001; Williams 2002; Magkos et al.
2003), but have received more attention in recent studies (Brandt et al. 2011).
Whether organic food has higher quality than conventionally produced food is
highly dependent on how organic food quality is defined and determined. Food qual-
ity can be classified into the following fields: sensory properties, nutrition and health,
authenticity and traceability, and specific organic properties (Willer and Kilcher
2012). The last two fields, however, are specific to organic food quality, so only
sensory properties and nutrition and health can be used to compare the quality of
organic foods and conventional foods. For both fresh and processed food, studies
carried out on the sensory difference in terms of taste, smell, texture, and appear-
ance showed a wide variety of results. In some studies, significant differences were
found while other studies did not detect any differences (Willer and Kilcher 2012).
Even though information on sensory differences is limited and inconclusive, more
research is needed because taste and other sensory factors play an important role in
purchasing decisions of consumers (Hughner et al. 2007).
Most of the data reported has been from plant products because information on
organic animal products is vague and less sufficient. Early research was limited to
dry matter; crude protein content; vitamins A, B 1 , B 2 , and C; minerals; and trace ele-
ments. Results indicated that organic plant products including leafy, root, and tuber
vegetables contain more dry matter, but there was no significant difference between
organically and conventionally produced fruits and fruit vegetables (Magkos et al.
2003). Due to lower nitrogen availability, organic fruits and vegetables generally
have lower crude protein content but higher quality protein in some vegetables.
Although the majority of comparisons on vitamins and mineral elements revealed
no significant difference, Worthington (2001) reported that organic fruits and veg-
etables contained significantly more iron, magnesium, phosphorus, and vitamin C
than conventionally produced ones. However, no general statement could be drawn
because there was insufficient data for carbohydrate, protein, and other vitamins.