Graduate Thesis Or Dissertation
 

The effects of differing hazelnut concentrations in hog finishing rations with respect to pork shelf-life and fatty acid composition

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  • Commercial hog diets in the United States commonly contain lipid sources high in polyunsaturated fatty acids, most notably linoleic acid (18:2). This may result in greater deposits of linoleic acid in pork adipose tissue, contributing to an increased potential for lipid oxidation, high n-6/n-3 fatty acid ratio and increased fat softness. These factors lead to detrimental effects on shelf-life, potential negative nutritional impacts on humans and yield loss, respectively. The hazelnut is a crop abundant in nutritionally beneficial oleic acid (18:1) and the antioxidant α-tocopherol. Due to aesthetic or conformational characteristics, a cull portion of this crop is thought to be undesirable for human consumption, and offers a relatively low-cost potential feedstuff for livestock. Altering the fatty acid profile of pork to reduce proportions of linoleic acid and increase oleic acid presents the potential to improve shelf-life and impart a favorable nutritional profile in pork tissues. With this in mind, the objective of our study was to explore the effects of differing concentrations of cull hazelnuts as a lipid source in hog finishing rations, and their influence on pork shelf-life and fatty acid composition. Cull hazelnuts (95% kernel, 5% shell) were obtained and ground for replacement use in a commercially-sourced hog finishing ration. Berkshire-cross hogs (n=15, avg 97 Kg) were randomly assigned to one of three treatment groups (5/treatment): basal diet fed commercial pelleted finishing ration with 0% hazelnut composition (H0), 15% by overall weight hazelnut composition (H15), and 30% by overall weight hazelnut composition (H30), respectively. Hogs were fed ad libitum for 42d and then slaughtered. The Longissimus from one side of each hog was extracted 72 hr postmortem, vacuum-packaged, held at 3 ºC for 4 d to simulate transportation, and then sliced into 2.54 cm thick chops. Chops were packaged in polystyrene trays and overwrapped with O₂ permeable film, placed into a simulated retail display with continuous fluorescent lighting (3500K CCT, 1600-2200 lux) and held at 3 °C. Instrumental color was evaluated daily with a portable spectrophotometer. Samples were removed from display at days 0, 2, 4 and 6 for determination of lipid oxidation by thiobarbituric acid reactive substances (TBARS). Additional samples were excised to measure fatty acid composition, α-tocopherol content and total phenols. Data were analyzed as a completely randomized design, and each hog served as the experimental unit. Diet treatment was denoted as the main effect, with analysis day serving as a repeated effect in the case of shelf-life analyses. Redness (CIE a*) values in chops declined during retail display for all treatments, however rate of decline based on treatment did not differ. Lipid oxidation (TBARS) was suppressed (P<0.05) at d 6 in both H15 and H30 chops compared to H0. Total phenols were not different (P>0.05) between diet treatments, however α-tocopherol levels were 82 and 130% higher (P<0.05) in H15 and H30, respectively, than H0. Palmitic acid (16:0) levels diminished (P<0.05) in H30 pork, while oleic acid (18:1) increased (P<0.05) from 43.7% in H0 to 48.2% in H15, and 50.4% in H30 in subcutaneous fat. No significant changes (P>0.05) in linoleic acid (18:2) or n-6/n-3 ratio were identified. Through the inclusion of hazelnut feed supplementation, the fatty acid composition of pork improved nutritionally via increases in oleic acid (18:1) and decreases in palmitic acid (16:0); however, no other definite benefits were identified in this study. The suppression of TBARS can likely be attributed to an increase in α-tocopherol content in muscle, yet suppression was not significant enough to produce discernable effects on shelf-life when evaluated for instrumental color and purge loss.
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