Enrichment of Pork with Omega-3 Fatty Acids by Tuna Oil Supplements: Effects on Performance as well as Sensory, Nutritional and Processing Properties of Pork

The effects of tuna oil supplementation (0, 1, 2 and 3%) to pig diets on growth and carcass yield as well as meat quality were determined in 40 crossbred pigs. Animals were fattened from 30 to 90 kg of live-weight. Twenty-four hours after slaughter, following various early- and late-post mortem measurements, loin, backfat and belly were prepared from the carcasses. Bacon was produced from the belly part by curing and smoking. Neither performance (feed intake, daily gains, feed conversion efficiency) nor carcass quality (slaughter weight, dressing percentage, lean percentage, nutrient composition of the loin) were significantly affected by tuna oil supplementation. Tuna oil also had no clear effects on early- and late-post mortem meat quality traits, water-holding capacity and tenderness of the M. longissiumus dorsi (LD). Colour traits of LD and backfat, and backfat firmness were not significantly affected by tuna oil, either. However, there was a certain trend to elevated fat contents of LD (and bacon), but not of backfat, with increasing levels of tuna oil in feed. Pigs receiving elevated proportions of tuna oil expressed lower VLDL cholesterol and triglyceride concentrations in blood plasma, whereas the cholesterol content of LD, backfat and bacon did not reflect this trend. Effects of tuna oil on fatty acids in LD, backfat and bacon were often small in extent, except those concerning the long-chain polyunsaturated fatty acids. With 3% tuna oil in the diet, the contents of the particularly desired omega-3 fatty acids, C20:5 and C22:6, were 0.1 and 0.2 g/kg in LD. The corresponding values for backfat and bacon were 2.6 and 12.6 g/kg, and 1.3 and 9.2 g/kg, respectively. Tuna oil supplementation was associated with significant adverse effects on flavour and overall acceptance of bacon (not significant in LD although numerically the same trend was noted), but these effects on sensory ratings were limited in extent. Also shelf life of the products, determined as TBA value after different storage periods at $4^{\circ}C$ in LD, backfat and bacon, was significantly reduced. Overall, the present study suggests that omega-3 fatty acids may be enriched in pork by feeding tuna oil with few undesired side-effects, particularly those on sensory perception and shelf life, suggesting immediate consumption of the products is advisable. Most economically important traits (performance, slaughter and physical meat quality) remained unaffected.