Improving the quality of British pork and bacon
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Research partner: University of Bristol
Sponsor: BPEX
Duration: 2006 – 2009
Young entire male pigs have a better commercial performance than castrates in terms of more efficient food conversion and higher lean meat percentage of the carcase. However entire males often have a higher incidence of odours and flavours, known as boar taint, which are found unpleasant by some consumers. Boar taint results from an excessive accumulation of two major compounds, skatole and androstenone, in adipose tissue. This PhD-study examined different aspects of the occurrence of boar taint, with emphasis on management procedures, diets and online detection of boar taint, through three projects.
The first two projects studied the effect of pig growth rate and health status on boar taint, under experimental conditions and in commercial practice. There is a perception that boar taint will be higher in slow growing, older pigs, due to them being more sexually mature at slaughter. However, in both projects, boar taint compounds were measured at higher concentrations in faster growing male pigs which was associated with reduced pork odour. Therefore boar taint was not higher in older, slower growing pigs (results in last year’s technical report, page 107).
Different studies have shown that the concentration of skatole in pork can be reduced by feeding compounds in the diet which change the pattern of microbial fermentation.
In the second project a total of 360 entire male pigs were used to evaluate the effects of a short feeding period with inclusion of chicory (Cichorium intybus L.), a source of inulin, before slaughter on skatole and androstenone levels in backfat. The pigs had been divided into four groups and fed different levels of chicory: 0, 30, 60 and 90 g/kg diet. For each group 30 entire pigs were sampled at three different times: a first time (called week 0) to measure the base level of skatole and androstenone in each group, before the supplement of chicory was introduced; and after one and two weeks on the test diet. All 360 backfat samples from the neck region were assessed for skatole concentration; androstenone was measured in 110 pigs (all 90 g/kg pigs). Samples of backfat were presented to a 10 member taste panel after cooking for “sniff” tests to determine if reducing skatole had also reduced boar taint. Chicory fed at the level of 90 g/kg for two weeks was successful in reducing skatole to a level well below the ‘threshold’ for this compound (0.2 µg/g). The concentration of androstenone increased slightly in the pigs fed 90 g/kg chicory after two weeks.
There were no differences between the groups in the abnormal odour scores after two weeks (Table 1). The results show that the inclusion of dried chicory in the diet for two weeks was effective in reducing skatole concentrations. However no improvement in abnormal odour scores occurred, probably because androstenone remained high.
Table 1: Affect of including chicory in the diet at difference concentrations for a period of two weeks
| Level of chicory inclusion (g/kg diet) |
Affect on skatole level (µg/g fat) |
Affect on abnormal odours (On a scale of 1-8*) |
| 0 (control) |
0.237 |
4.30 |
30 |
0.129 |
3.90 |
60 |
0.124 |
4.22 |
90 |
0.047 |
4.04 |
* Where 1 is extremely weak and 8 is extremely strong
The third project compares different heating methods used in abattoirs for the sensory assessment of abnormal odours in pig meat. The aim is to compare the effectiveness of these tests and to evaluate the contributions of androstenone and skatole to any abnormal odours generated. At present there is no recognised test method to detect carcases with pronounced boar taint and the third project could help to understand the best method for “on line” detection. Further details and results will be presented in next year’s annual report.
Page last updated 08 June 2010