The effects of dietary soy isoflavone supplementation on carcass cutability and meat quality of pigs infected with porcine reproductive and respiratory syndrome virus

PRRSV;pork;cutability;meat quality;aging;tenderness;sous-vide

Bryan, Erin E. ; Boler, Dustin, ; ,Dilger, Ryan N., ; ,Harsh, Bailey N. ; Dilger ; Anna C.

关键词: PRRSV;    pork;    cutability;    meat quality;    aging;    tenderness;    sous-vide;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/106262/BRYAN-THESIS-2019.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Porcine reproductive and respiratory virus is (PRRSV) is endemic in the U.S. swine industry. Understanding the viral effects on pig growth and meat quality is essential to characterizing the true impact of infection. Interventions to mitigate the detrimental effects of infection are necessary to successfully overcome these consequences. The objective of this research was to evaluate the effects of porcine respiratory and reproductive syndrome virus (PRRSV) infection and dietary soy isoflavone (ISF) supplementation on carcass cutability and meat quality of commercial pigs. Barrows were randomly allotted to experimental treatments that were maintained throughout the study: non-infected pigs received an isoflavone-devoid control diet (CON, n = 22), and infected pigs received either the control diet (PRRSV-CON, n =20) or a control diet supplemented with total ISF in excess of 1,600 mg/kg (PRRSV-ISF, n = 25). Following a 7-day adaptation, weanling pigs were inoculated intranasally with either a shamcontrol (PBS) or live PRRSV (1×105 TCID50/mL, strain NADC20). Pigs were then raised until 166 days post-inoculation and slaughtered humanely at the University of Illinois Meat Science Laboratory. At 1 d postmortem (192-194 days of age; approximately 120 kg BW), left sides were separated between the 10th and 11th rib for determination of loin eye area (LEA), backfat thickness (BF), and loin quality (ultimate pH, instrumental color, drip loss, visual color, marbling, and firmness). Loin chops were aged 14 d postmortem prior to Warner-Bratzler shear force (WBSF) determination. Belly width, length, thickness, and flop distance were determined. Data were analyzed as a one-way ANOVA in the MIXED procedure of SAS 9.4. Pig was the experimental unit. Least squared means were separated using the probability of difference (PDIFF) option and means were considered significantly different at P ≤ 0.05. Carcass yield, LEA, BF, and estimated lean percentage did not differ (P > 0.26) among treatments. Loins from CON pigs had increased ultimate pH (P = 0.01), reduced L* scores (P = 0.005) coupled with darker visual color scores (P = 0.004), were firmer (P < 0.0001), and had reduced drip loss (P =0.01) compared with PRRSV-CON and PRRSV-ISF pigs. However, WBSF of chops cooked to 71°C did not differ (P = 0.51) among treatments after 14 d of aging. Bellies from CON pigs were more firm (P < 0.01) compared with bellies from PRRSV-CON and ISF pigs. These data suggest PRRSV infection and soy isoflavone supplementation do not alter carcass characteristics but infection may marginally reduce loin and belly quality. Using the chops mentioned above, a separate cooking methods validation study was completed. The pursuit of novel, more repeatable, and more accurate methods to measure research outcomes is fundamental to the furthering of meat science. The objective of the second study was to determine the ability to detect differences in cook loss and WBSF values between chops aged for differing time periods and cooked to varying degrees of doneness within a sous-vide style cooker. The posterior section of a pork loin was cut into 6 separate 2.54 cm thick chops. The middle four chops were randomly designated for aging of 3 d and cooked to 63°C, aged 7 d and cooked to 63°C, aged 14 d and cooked to 63°C, or aged 14 d and cooked to 71°C. Chops were cooked by placing them in a water bath with an immersion circulator set to the desired end-point temperature for 90 min. Cook loss was calculated and WBSF values were measured. Data were analyzed using a 1-way ANOVA. Least squares means were separated using the probability of difference (PDIFF) option in the MIXED procedure of SAS. Chop served as experimental unit, with loin serving as a block and day as a random effect. Differences in cook loss and tenderness were detected between aging periods. Overall, these data indicate sous-vide is an acceptable cooking method for use in experiments as expected differences in cook loss and WBSF were detected in chops aged to differing time points or cooked to differed degrees of doneness. This, combined with greater cooking temperature control, convenience, and potentially less degree of doneness variation indicate sous-vide may be more useful in meat science research than grilling.