Finding the difference between conventional and organic

Consumers in several regions of the world show a rising interest in organic food, including organic chicken meat. Despite this rising demand production of organic chicken meat increased only slightly. Although supporters of organic production claim better quality, the knowledge on the main factors contributing to the observed differences in quality is still limited.

Consumers who prefer meat of slow-growing birds raised with access to free-range believe that the meat has an improved texture and flavour. This is supported by some studies which revealed that in comparison to conventionally reared birds, meat obtained from an organic production system is more yellow, has a lower ultimate pH, a better water holding capacity, less cooking losses and higher shear values.

It is a common belief that texture, appearance and flavour are mainly influenced by genotype, diet and age. To better understand these relations the University of Hohenheim in Germany conducted a study to analyse the effects of genotype, feed composition and access to free range on quality and sensory attributes of meat from broilers with different genotypes. The achieved information is expected to help optimise production conditions in organic broiler production (choice of breed, importance of feeding stuffs and pasture) and to more clearly define the differences between organic and conventional broiler meat.

Comparing genotypes
The Hohenheim study, presented at WPSA’s XX European Symposium on the Quality of Poultry Meat in Leipzig, compared three different genotypes: fast growth (Ross 708; FG), medium growth (ISA 657; MG) and slow growth (ISA 757; SG). Each genotype was represented by groups of 20 birds each. These birds were kept without (OA) or with access to free range (MA) and were fed on conventional (KF) or organic diets (OF) resulting in a total number of 3 x 20 x 4 = 240 broilers per trial. The study included three trials with a total number of 720 broilers, which were fed ad libitum.

Birds which had no access to free range were kept at a stocking density of six birds per m². The free range groups were housed in similar indoor pens, but at the age of six weeks the birds had free access to a grass paddock (5m²/bird). At night these birds were confined to indoor pens.

The broilers were slaughtered at ages of 6, 9 and 12 weeks. For example, 50% of the FG broilers (Ross 708) were slaughtered at the age of six weeks and the remaining at 12 weeks to compare meat quality with market weight on the one hand and age-effects in comparison with SG broilers (ISA 757) on the other hand.

Cooking loss differs
In a first step, all birds were reared to a slaughter age of 12 weeks showing an average life weight was 4.9 kg for FG broilers, 3.7 kg for MG broilers and 2.1 kg for SG broilers. After slaughtering and maturation of the meat it was concluded that at 12 weeks of age cooking loss was significantly (P<0.05) higher for FG broilers than for MG and SG broilers. Which means that SG birds have a better water holding capacity (WHC) than FG broilers, and the meat is significantly darker (Table 1). Interestingly genotype did not significantly influence texture measurements, although there was a tendency for more tender meat in MG broilers than in other breeds.

The effect of diets is presented in Table 2. It shows that birds fed with a conventional diet had significantly higher cooking losses, whereas, organic feed resulted in better water holding capacity. Meat of broilers fed with a conventional diet was significantly paler and less red than from broilers fed with an organic diet, whereas, meat from birds fed with an organic diet was slightly more yellow. Interestingly, access to free-range however did not influence carcass and meat quality significantly.

Members of a taste panel noted differences between FG broilers fed with conventional diet and broilers fed an organic diet. They assessed FG broilers to be more tasty.

Age effect
As expected, FG broilers slaughtered at 12 weeks of age showed significantly higher cooking losses and texture values (Table 3) than when slaughtered at six weeks of age. But WHC values were almost identical for both ages and no clear effects were observed for pH-values. Differences were found in meat colour: meat of younger FG broilers was significantly darker. Similar age effects were seen in meat of MG broilers (slaughter age nine and 12 weeks).

The comparison of meat of FG broilers slaughtered at 6 weeks of age with SG broilers at 12 weeks of age revealed significantly lower cooking losses and better WHC for the older broilers. Meat of six week old FG broilers was significantly more tender, but there was no significant difference in meat colour.

In conclusion, the results of this German study clearly show that meat quality characteristics are mainly influenced by genotype and diets, while husbandry systems only have a minor effect. The opposite is true for sensory attributes of meat. Although sensory tests demonstrated that untrained panelists barely detect differences in meat flavour. Nevertheless genotype and diet have only a little impact on the sensory attributes, and impact is greater when the birds have access to free-range.

Italian experiences
A similar comparison was done by the University of Bologna, Italy. It presented in Leipzig a study which characterised carcass traits and meat chemico-physical properties of chickens labelled free-range (according to the EC Directive 1538/91) and conventional broilers as they are presented to consumers at Italian retail markets. The researchers separately raised free range (FR) female and male chickens for 56 and 70 d, respectively, in order to obtain current market product categories (rotisserie and cut-up carcasses). These medium growing ISA birds had continuous daytime access to an open-air area from 28 d to slaughter age. Their indoor stocking density did not exceed 27.5 kg/m². The conventional (C) female and male chickens (Ross 708) were separately raised indoor for 39 and 50 d, respectively, under controlled environmental conditions at a stocking density of 30-32 kg/m².

The female and male birds were slaughtered in two separate sessions. Of each group 20 carcasses were randomly selected to evaluate carcass cut-up yields and fifteen of them were used to assess quality properties of both breast and leg meat (skin and meat colour, ultimate pH, drip and cooking losses, AK-shear force).

Results show that, as could be expected, conventional birds had a dramatic higher carcass and breast meat yield (Table 4), whereas free range birds had higher wing and leg yields (Figure 1). Both meat and skin of breast and leg coming from free range birds were lighter and less red and more yellow. FR birds exhibited higher water-holding capacity (lower drip and cooking losses) in both breast and leg meat. Finally, although shear force did not differ in breast meat, leg meat from FR birds were tougher. Overall the data show that noticeable quality trait differences exist between free range and conventional labelled poultry products and validates the existence of different market segments.