Characterizing pork quality
More fresh pork offerings could have big potential by enhancing eating experience, improving consumer demand
By Yifei Wang and Ben Bohrer
Fresh meat quality is largely influenced by composition, muscle function in the living animal and postmortem metabolic activity. The biological and biochemical differences between muscles throughout the carcass result in significant variation in quality attributes and eating experience. A muscle-specific approach to evaluating meat quality is necessary to more accurately understand and improve consumer eating experience of meat products.
In the U.S. market, further processed pork products, such as bacon, sausage and ham, comprise of 74% of total pork consumption, while fresh pork accounts for 26% of total pork consumption. Within the fresh pork category, loin chops — consisting primarily of the longissimus muscle — represent the majority of sales at 49.7%, followed by ribs, shoulders and ground pork. This reveals a significant opportunity for the pork industry to diversify fresh pork offerings and provide more options for consumers.
Pork quality is typically evaluated using parameters such as color, marbling, firmness, pH, composition, tenderness, water-holding capacity and extent of protein degradation. These assessments are most often applied to the longissimus muscle and are then used to make decisions regarding genetic selection, nutrition, animal handling and post-harvest handling of carcasses and meat products. However, muscles differ in their inherent biological and biochemical properties, which influence their quality attributes and eating experience.
To address the opportunity of providing more fresh pork offerings for consumers, this research investigated pH and temperature decline, instrumental quality traits, proteolytic activity and descriptive sensory attributes for the longissimus thoracis (i.e., the major muscle in the loin primal), psoas major (i.e., the tenderloin muscle), semitendinosus (i.e., the eye muscle from the ham), triceps brachii (i.e., the center muscle from the shoulder) and gluteus medius (i.e., the major muscle from the sirloin) (Figure 1).
Is pork quality muscle-specific?Favorable pork quality is often characterized by greater ultimate pH, slower pH decline, darker color, reduced drip loss and lower Warner-Bratzler shear force, which is associated with improved water-holding capacity and greater levels of sensory tenderness and juiciness. To explore these differences, five pork muscles from fifteen pigs were evaluated for postmortem pH and temperature decline, instrumental color, drip loss, proximate composition and Warner-Bratzler shear force.
Muscle pH is one of the most critical indicators of pork quality. It influences protein denaturation, water-holding capacity and meat texture. The rate of pH decline is influenced by temperature, while the extent of decline is largely determined by glycogen availability in the muscle. A rapid pH drop prior to sufficient carcass chilling can result in protein denaturation, lighter color, poor water retention and reduced levels of sensory tenderness and juiciness.
Among the muscles evaluated, the longissimus exhibited the most rapid pH decline between 1- and 3-hours postmortem and reached the lowest ultimate pH (~5.47) at 24-hours postmortem (Figure 2). In contrast, the psoas major, triceps brachii, and semitendinosus had the greatest ultimate pH (~5.68), indicating a slower rate of acidification and potentially improved protein functionality.
Instrumental color analysis revealed that the longissimus was the lightest and least red among the muscle cuts, while the psoas major appeared darkest with the greatest redness values. These differences reflect the variations in pigment concentration and stability, which could be influenced by muscle fiber composition, rate and extent of pH decline and postmortem metabolism.
Drip loss, an indicator of water-holding capacity, was greatest in the longissimus and lowest in the psoas major. Lower drip loss is desirable, as it reduces moisture loss during storage and improves yield and palatability in addition to making the product more visually appealing in the retail setting.
Proximate composition analyses showed notable variation in intramuscular fat (IMF) content. The longissimus (1.75%) and psoas major (1.65%) had the lowest IMF levels, followed by the triceps brachii (3.17%) and gluteus medius (3.14%). The semitendinosus exhibited the greatest IMF content at 10.29%, which may contribute positively to flavor and juiciness.
Instrumental tenderness, evaluated by Warner-Bratzler shear force, further highlighted muscle-specific differences. The gluteus medius had the greatest WBSF values, indicating greater toughness, while the psoas major recorded the lowest shear force, confirming its reputation as the most tender cut.
How does proteolysis vary across muscles?Postmortem aging is a widely adopted strategy to improve meat tenderness. During aging, meat cuts are held under refrigerated conditions, allowing natural enzymatic activity to break down myofibrillar proteins in muscle. This process, known as postmortem proteolysis, targets specific myofibrillar proteins, weakening the muscle structure and ultimately improving tenderness.
Calpain-1, a naturally occurring enzyme, plays a primary role in degrading muscle proteins. Desmin, the largest intermediate filament protein, and troponin-T, which regulates muscle contraction, are commonly used as biomarkers for proteolytic activity and tenderness development (Figure 3). To better understand muscle-specific differences in aging potential, we measured calpain-1 activity and the degradation of desmin and troponin-T in five pork muscles.
The longissimus and gluteus medius muscles demonstrated the greatest calpain-1 activity at 1 day postmortem, indicating these cuts may benefit the most from extended aging —potentially up to 10 to 14 days. This finding was supported by the greatest desmin degradation in the gluteus medius and greatest troponin-T degradation in the longissimus at both 1- and 10-days postmortem. These results indicate a greater level of proteolysis in these muscles, likely driven by their greater proportion of fast-twitch (Type IIB) muscle fibers, which are more susceptible to breakdown.
In contrast, the semitendinosus, triceps brachii and psoas major exhibited lower proteolytic activity, implying shorter or minimal aging periods may be sufficient for these cuts. Since longissimus and gluteus medius muscles also tend to be tougher initially (as shown by greater Warner-Bratzler shear force values), aging these muscle cuts may deliver the most noticeable improvements in tenderness.
Which pork cut, cooking temperature deliver the best eating experience?In 2011, USDA revised its recommended safe cooking temperature for whole muscle cuts of pork from 160°F (71°C) to 145°F (63°C) with a three-minute rest time. This adjustment was based on evidence from a large consumer sensory study and aimed at enhancing eating quality — specifically tenderness and juiciness — without compromising food safety.
To evaluate the impact of endpoint cooking temperature on sensory traits, we evaluated five pork muscles using sous-vide cooking at either 63°C or 71°C. Trained sensory panelists scored tenderness, juiciness, pork flavor and overall acceptance using a 15 cm line scale, where greater values indicate more favorable eating quality.
Cooking to 63°C consistently resulted in greater scores for all sensory traits compared to 71°C (Figure 4). However, the extent of improvement varied by muscle, indicating muscle-specific responses to endpoint temperature.
Figure 4. This figure shows how two different cooking temperatures—63 °C (145 °F, red bars) and 71 °C (160 °F, gray bars)—affected tenderness, juiciness, pork flavor, and acceptance across five pork muscle cuts: longissimus thoracis (LT; loin), psoas major (PM; tenderloin), semitendinosus (ST; eye muscle of the ham), triceps brachii (TB; center muscle in the shoulder), and gluteus medius (GM; sirloin). Lower cooking temperatures led to more favorable eating quality, with all muscles scoring above the 7.5 cm midpoint (green line) on a 15 cm sensory scale for all attributes. In contrast, all muscles cooked to 71 °C scored at or below 7.5 for juiciness and acceptance, indicating drier and less acceptable pork. The LT lost the most juiciness when overcooked, while PM and ST were more forgiving. Bars with different superscript letters (a–e) are significantly different (P < 0.05). Δ values represent the difference in sensory scores between the two cooking temperatures for each muscle cut.
The longissimus muscle cut was the least forgiving at higher temperatures, exhibiting the greatest reduction of juiciness, pork flavor and acceptance. In contrast, psoas major and semitendinosus muscle cuts were more resilient at higher endpoint cooking temperature, demonstrating the least reduction in tenderness and juiciness, respectively. Regardless of cooking temperature, psoas major and semitendinosus muscle cuts had the most favorable sensory tenderness, juiciness, pork flavor and acceptance scores.
When scores were compared to the midpoint (7.5 cm) of the sensory scale—represented by the green line in Figure 4 — all muscles cooked to 63°C scored above 7.5, reflecting more tender, juicier and more acceptable eating experiences. Conversely, all muscles cooked to 71°C scored at or below 7.5, indicating a drier and less acceptable eating quality.
ConclusionCollectively, findings from this study demonstrated significant muscle-specific variation in pork quality and eating experience. These results emphasize the need to consider individual muscle characteristics when assessing pork quality and developing strategies to optimize the eating experience of fresh pork. The influence of cooking temperature further reinforces the importance of closely monitoring endpoint cooking temperature, as it directly affects tenderness, juiciness, flavor and acceptance of fresh pork.
Future research is needed to better understand the unique traits of each muscle cut and the best practices for use in retail and food-service settings. Developing unique quality specifications and preparation guidelines for each muscle cut could help ensure favorable eating experience and increase demand for a broader range of fresh pork cuts.
Wang is a Ph.D. student and Bohrer is an assistant professor in meat science and muscle biology, both at The Ohio State University
