Chroma meter

All animal procedures were performed in accordance with the Guidelines for Care and Use of Laboratory Animals of Nanjing Agriculture University and approved by the Animal Ethics Committee of Nanjing Agriculture University. A total of 300 healthy Suhuai pigs (i.e., 194 castrated barrows and 106 sows) with the same market weight (80–90 kg) and approximately 7–8 months old were reared at the Huaiyin Breeding Farm (Huaian, China) under the same feeding conditions and slaughtered at Sushi Meat Products Co., Ltd. (Huaian, China).
Ear tissues from the end of the right ear were collected and stored in 75% alcohol for DNA extraction. Samples of the LD, SOL, psoas major (PM), masseter (MA), and biceps femoris (BF) muscles were collected for RNA extraction from four randomly selected healthy Suhuai pigs with similar body weight and age. LD muscle samples from the last rib of the carcass were collected and used to determine meat color. In China, traditional hot fresh meat is usually marketed immediately after slaughter, whereas chilled fresh meat is often cooled quickly to a stable 0–4°C within 24 h postmortem and maintained at this temperature until sold to the consumer (21 (link)). Therefore, meat color (L^*a^*and b^*) was measured on the last rib at 2 (room temperature) and 24 h (4°C) postmortem using a chromameter (Minolta Camera Co., Osaka, Japan).

The color values of CIELAB Color System (1976), L^* (lightness) a^* (redness), and b^* (yellowness), were determined on the breast muscles 15 min after slaughter using a Chroma meter (Konica Minolta, CR-400-Japan). As described by Valizadeh et al. (33 (link)) and Qaid et al. (34 (link)), values for L^*, a^*, and b^* were converted to estimate the saturation index, total color change (ΔE), hue angle, browning index (BI), and whiteness index (WI). These parameters could provide more accurate assessment of how consumers perceive meat color.