Purdue University Graduate School
2021.12.8 Yufei Guo.pdf (1.09 MB)


Download (1.09 MB)
posted on 2021-12-20, 14:04 authored by Yufei GuoYufei Guo

The United States is ranked third for global pork production as well as first in pork exports according to the USDA Economic Research Service in 2019. The majority of the commercial pork production in the United States applies some form of confinement system with environmentally adapted facilities. However, with information and easy media access to the US consumers, news and reports on different farming practices and potential issues in the animal industry have come under the spotlight. Consumers are becoming more interested in knowing what goes on behind the scenes of the commercial animal industry and where and how their food is produced. Whether it is due to personal beliefs, ethical concerns, novelty-seeking, eating experience, or choice of lifestyle, consumers are demanding diversity in their meat purchasing options. Although the commercial pork industry has shifted to fewer and larger farms in the last 40 years, small specialty farms such as heritage breed pork are on the rise to form a niche market. Large Black pig is a pasture-raised heritage breed originating in England, and it remains one of the rarest British pig breeds. Due to differences in husbandry, pasture-raised Large Black pigs consume a relatively high forage diet compared to corn-based diet used in commercial swine production. Although heritage pork has been lauded to have unique and superior quality, enhanced eating experience, and is often sold at a premium price, there are very little data on pork quality of Large Black pig compared to Duroc-sired breeds which are commonly used in commercial pork production. The purpose of this study is to fill the dearth and investigate differences in pork processing characteristics between commercial Duroc-sired and Large Black genetic lines fed high forage or commercial diets.

The study contained a total of 50 pigs: 25 Duroc-sired (DS) and 25 Large Black sired (LB) pigs. After all the pigs were weighed, the pigs were randomly assigned with heavy and light weights as blocks to two dietary treatments: Fiber (FIB) and Control (CON); and the feeding trial lasted a total of 126 days. There were 14 Large Black pigs fed fiber diet (LB FIB); 11 Large Black pigs fed control diet (LB CON); 14 Duroc-sired pigs fed fiber diet (DS FIB) and 11 Duroc-sired pigs fed control diet (DS CON). Pigs were fed either a control Corn-Soybean Meal-DDGS based diet or a high fiber diet with wheat middlings and dehydrated alfalfa meal replacing corn and soybean meal in the control diet. Diets were fed over six 21 days phases with fibrous ingredient levels increasing from 8.5 to 30 percent of the diet with sequential dietary phase from 1 to 6. Pigs were harvested at a common age with some variations in body weight between genetics (DS 125 ± 2.23 kg, LB 99 ± 2.28 kg; P < 0.001). Individual batches of 80% lean : 20% fat sausage patties with seasoning (136g per patty) were made from the shoulder of each pork carcass. PVC packaging was applied to each batch of sausage patties. Fat smear was noted on day 0 with a fat smear scale of 1 (excessive far smearing) to 8 (clear fat particle definition). Color parameters that include lightness (L*), redness (a*), yellowness (b*), and lipid oxidation (2-Thiobarbituric acid reactive substances, TBARS) due to retail display effect were measured at days 0, 3, and 7 by placing packaged sausage patties under the retail display lighting. Boneless bellies were removed and weighed (fresh weight) from each pig and measurements for belly thickness, length, and firmness were recorded. Fresh bellies were injected to 110% fresh weight, thermally processed (62°C), and cooled (1°C internal temperature). Cooked weight was obtained before slicing. Belly processing yield was calculated as a percentage using (cooked weight / fresh weight) x 100. Adobe Photoshop was used to perform visual image analysis for bacon slice length (SL; cm), slice area (SA; cm2), and slice lean area (LA; %), one 0.64 cm bacon slice was obtained from 25, 50, and 75% distance respectively from the blade end of each cooked bellies for the analysis. RStudio (1.2.1335) was used to analyze data with breed and diet as fixed effects and least square means separated at (P < 0.05).

Results showed that only diet was significant for patty fat smear (P = 0.0104), CON patties had better particle definition than FIB patties. Difference for patty color L* (P = 0.0051), a* (P < 0.0001) and b* (P < 0.0001) were found for days of retail display. Breed was significant in L* (P < 0.0001) and a* (P < 0.0001) with DS patties being lighter and less red than LB patties. Days under retail display (P < 0.0001) and breed x diet interaction (P = 0.0014) were found in lipid oxidation. DS CON had the least amount of lipid oxidation throughout retail display time. Breed and diet were significant for both belly thickness and length. LB (P = 0.0263) and CON (P < 0.0001) bellies were thicker than DS and FIB bellies respectively. DS (P < 0.0001) and CON (P = 0.0045) bellies were longer than LB and FIB bellies respectively. A breed x diet interaction (P = 0.0527) was observed in belly firmness and LB CON had the firmest bellies. Processing yield was found to be greater in DS bellies (P = 0.0014) than LB bellies. Breed effect had a tendency (P = 0.065) on SL, DS slices were longer. CON had greater SA (P < 0.0048) than FIB slices. DS slices had significantly higher LA (P < 0.0001) than LB slices.

The study provided novel insights into the differences in processing characteristics between the DS and LB genetic lines as well as the effect of diet on each breed. Results such as thicker and firmer belly, lower LA in LB were expected since LB is a minor swine breed that has not undergone intense genetic selection for percent lean meat. Overall, each breed had a better product when fed their accustomed diet (FIB for LB, CON for DS) such as less lipid oxidation in sausage patties for DS CON compared to LB CON. Although LB fits into the niche market of heritage breed pork, future studies in management systems, processing methods, and genetic improvement should be considered to improve product quality to better meet modern consumer demands.


Degree Type

  • Master of Science


  • Animal Sciences

Campus location

  • West Lafayette

Advisor/Supervisor/Committee Chair

Stacy Zuelly

Additional Committee Member 2

Yuan H. Kim

Additional Committee Member 3

Bailey N. Harsh