Successful marketing of pork enriched with omega-3 fatty acids requires that other pork attributes are not reduced. A series of experiments at the Prairie Swine Centre, Saskatoon, Saskatchewan, have shown that the inclusion of 5% extruded flaxseed in the diet of finishing pigs for 11 weeks prior to marketing enriched some cuts of pork sufficiently to allow a claim of “omega-3 enriched” (300 mg omega-3/100 grams). However, at the high levels of enrichment, there was some indication of “off-flavors” noted by taste panels.
Vitamin E (DL-a-tocopherol acetate) is a natural, fat-soluble vitamin that has been used in high-fat diets to prevent the oxidation of unsaturated fatty acids that can cause rancidity.
The objective of this experiment was to determine if added vitamin E could mitigate problems of rancidity or off-flavors associated with high levels of omega-3 when flaxseed is used in pig finishing diets.
Ninety-six growing pigs were fed one of three different diets for 11 weeks prior to slaughter. The diets contained no flaxseed (Diet A; control), 5% flaxseed (Diet B), or 5% flaxseed plus 200 mg/kg vitamin E (Diet C) and were fed to two weight groups — 66 and 96.8 lb.
Diets were based on wheat, barley and soybean meal and fed for three phases of growth. Flaxseed was added as LinPro (O&T Farms), an extruded 50:50 pea/flaxseed blend using extrusion conditions optimized in a previous experiment. Field peas were added to the diets to compensate for the added peas in the LinPro, thus equalizing pea content in all diets.
Diets A and B contained 11 mg (IU)/kg of vitamin E, meeting the National Research Council (NRC) requirement for pigs of this age, but providing no safety margin.
Pigs were slaughtered in a simulated commercial manner. Sensory analysis of fresh, cooked pork and pork burgers was conducted by a trained taste panel.
As expected, a diet containing 5% flaxseed increased the omega-3 content of pork fat, especially high-fat pork products (Table 1). Omega-3 fatty acids are highly unsaturated, which results in decreased fat firmness.
Feeding 5% flaxseed in the diet had minimal or no effect on flavor, including rancidity, in low-fat cuts of pork. Ground pork containing 20% fat, from pigs fed 5% flaxseed, had slightly but significantly decreased pork flavor, desirability and palatability (Table 2). A greater proportion of panelists reported that pigs fed flaxseed had a rancid or “other flavor.” The added vitamin E lessened these negative side effects, although this pork still did not score as high as pork from pigs fed no flaxseed.
Although 5% flaxseed diets had minimal or no effects on off-flavors in low-fat cuts of pork, cuts containing a higher fat content, such as ground pork, were negatively affected. Supplementing the diet with 200 IU/kg vitamin E mitigated these negative effects. Further research is required to determine if there are other, more efficient methods (i.e., post-harvesting technologies) to alleviate this problem.
Strategic funding for this project was provided by Sask Pork, Alberta Pork, Manitoba Pork Council and the Saskatchewan Agriculture and Food Development Fund. Project funding was provided by Flax Canada and the Saskatchewan Agriculture Development Fund. We gratefully acknowledge the donation of the LinPro from O & T Farms, SK.
Researchers: A.D. Beaulieu, Prairie Swine Centre; and M.E.R. Dugan and M. Juarez, Agriculture and Agri-Food Canada, Lacombe Research Centre, AB. For more information contact Katie Carr at katie.carr@usask.ca.
