Sous-vide is a cooking method used to improve the tenderness and juiciness of chicken breast. However, the comparative changes in meat quality attributes of sous-vide cooked chicken breast and thigh muscles are not fully understood. The objective of this study was to investigate the effects of sous-vide cooking conditions, based on collagen denaturation temperature of intramuscular connective tissue, on the physicochemical properties of chicken breasts and thighs. Chicken breast and thigh were cooked at four sous-vide cooking conditions (55 °C for 3/6 h and 65 °C for 3/6 h) and conventional cooking at 75 °C (core temperature of 71 °C) as control. No significant differences in pH and lightness were found between the sous-vide cooking conditions. Moisture content, cooking loss, protein solubility, shear force, myofibrillar fragmentation index, and lipid oxidation were affected by sous-vide cooking conditions (p < 0.05). The decreased shear force and total collagen content of 65 °C sous-vide cooking treatment might be associated with collagen denaturation (p < 0.05). Sous-vide cooking at 55 °C could decrease cooking loss, with higher moisture than sous-vide cooking at 65 °C (p < 0.05). These tendencies on water-holding capacity and shear force at the two different temperatures were similarly observed for both chicken breast and thigh. Therefore, this study indicates that chicken breast and thigh are similarly affected by the sous-vide cooking conditions and suggests that a novel strategy to apply together two temperature ranges based on the thermal denaturation of intramuscular connective tissue would be required.

The objective of this study is to evaluate the effects of NaCl and KCl salting on technological properties of pre- and post-rigor chicken breasts at various ionic strengths. The following factorial arrangement was used: 2 salt types (NaCl and KCl) × 2 rigor statuses (pre- and post-rigor) × 4 ionic strengths (0.086, 0.171, 0.257, and 0.342). Hot-boned and ground chicken breasts were salted within 30 min postmortem after slaughter (pre-rigor salting) or 24 h postmortem (post-rigor salting) with varying concentrations of NaCl (0.50%, 1.00%, 1.50%, and 2.00%) or KCl (0.64%, 1.28%, 1.91%, and 2.55%) corresponding to the four ionic strengths. KCl caused higher pH value in salted chicken breasts than NaCl (p < 0.05). However, KCl decreased total and myofibrillar protein solubilities in post-rigor salted chicken breasts compared to NaCl (p < 0.05), but those were similar to pre-rigor chicken breasts, regardless of the salt type (p > 0.05). Different salt types had no significant impact on cooking loss and textural properties. This study shows that NaCl and KCl had similar effects on technological properties at the same ionic strength (within 0.342), but the use of KCl may have the possibility to decrease protein solubility, depending on rigor status of raw meat at the different salting time.

The physicochemical properties of the mixed gelatin gels with soy and whey proteins were investigated to develop the gel base with a soft texture and abundant essential amino acids for the elderly. Gelatin-only gel (control) was prepared at 6% (w/v), and mixed gelatin gels were formulated by replacing gelatin with soy protein isolate and whey protein concentrate at different mixing ratios [gelatin (G):soy protein isolate (S):whey protein concentrate (W)]. Results showed that replacing gelatin with the globular proteins in gelatin gels increased the pH value and processing yield (p < 0.05). Moreover, the mixed gelatin gels, particularly the G2:S1:W3 treatment, showed significantly higher essential amino acids than the gelatin-only control. The partial replacement of gelatin with the globular proteins could decrease the hardness of gelatin gel (p < 0.05), but there was no difference in hardness between the G2:G3:W1, G2:S2:W2, and G2:S1:W3 treatments (p > 0.05). The results of protein pattern, x-ray diffraction, and microstructure had no clear evidence for specific protein–protein interaction in the mixed gelatin gels. Therefore, this study indicates that mixed gelatin gels with the globular proteins at specific mixing ratios could be a practical approach to providing a soft texture and high-level essential amino acids to the elderly.

Porcine by-products have garnered attention as an excellent material for producing antioxidant peptides; however, understanding the antioxidant characteristics of protein hydrolyzates derived from specific parts remains limited. In this study, we compared the antioxidant properties of protein hydrolyzates derived from major porcine organs (heart, kidney, spleen, liver, and lung) and performed classification based on their antioxidative potential. Their chemical composition exhibited significant variations, with a high protein content ranging from 15.90 to 20.30 g/100 g. Alcalase achieved higher hydrolysis efficiency than trypsin, which induced limited degradation of some proteins, such as porcine serum albumin. The hydrolyzates exhibited superior radical scavenging activities compared to the raw materials, although their reducing power remained unaffected or, in some instances, decreased. Hierarchical and k-mean cluster analyses revealed distinct antioxidant profiles and Alcalase-hydrolyzed kidney and trypsin-hydrolyzed lung hydrolyzates were deemed the most promising candidates, with strong radical scavenging activities and reducing power. Our findings indicate that, even when processed in bulk rather than being obtained from specific parts, porcine by-products can produce hydrolyzates rich in antioxidant peptides through enzymatic hydrolysis. However, selectively processing porcine kidneys with Alcalase and lungs with trypsin is recommended to produce premium products with enhanced and balanced antioxidant properties.

The objectives of this study were to evaluate antioxidant capacity of hot water extract from red maple leaf with different extraction times (experiment I) and to determine their impacts on color, free anthocyanin content, and hardness of gelatin gels (experiment II). In experiment I, hot water extraction time (30, 60, 120, 180, and 360 min at 60 °C) was fixed as a main effect. The different extraction times had no impacts on total polyphenol content and DPPH radical scavenging activity (p > 0.05). However, extraction time for 360 min could decrease anthocyanin content as well as ferric reducing antioxidant power (p < 0.05). In experiment II, 6%, 18%, and 30% gelatin gels were prepared without/with red maple leaf extract (1000 mg/L). The red maple leaf extract significantly increased redness, yellowness, and hardness, but decreased free anthocyanin content. Such impacts were obviously observed at high gelatin concentration. Thus, red maple leaf extract could be a novel anthocyanin source for improving antioxidant capacity and reddish color of gelatin gels. However, the addition amount of red maple leaf extract may be limited in the development of senior-friendly jelly food for soft texture in that it could increase the hardness of the gelatin gel.

The objectives of this study were to elucidate the effect of different high-concentration levels of inert gases (Ar and N₂) on heme-pigment solutions and on the color of the blood, meat, and small intestine of rabbits; and to figure out the proper concentration level of inert gas (Ar or N₂) for the complete stunning of the rabbit. To observe the changing of color attributes, a research study was conducted in the abattoir of the National Institute of Animal Science (NIAS), RDA, Republic of Korea. This experiment had 2 parts, (i) A trial on heme-pigment solutions (hemoglobin and myoglobin solution) was conducted in a gas chamber with different high-concentration levels of carbon dioxide, argon, nitrogen, and normal air; and (ii) a rabbit experiment was conducted—stunning with different high-concentration levels of carbon dioxide, argon, nitrogen, and the Halal method (non-stunning). A small-size digital gas chamber was used for this experiment (size: width 850 mm × depth 1350 mm). Artificial hemoglobin (Hb) and myoglobin (Mb) solutions were created from “porcine hemoglobin lyophilized powder” and “equine skeletal muscle myoglobin lyophilized powder”, respectively. In the heme-pigment solutions trial, 10 treatments were used: (i) 80% carbon dioxide (T1), (ii) 85% carbon dioxide (T2), (iii) 90% carbon dioxide (T3), (iv) 80% argon (T4), (v) 85% argon (T5), (vi) 90% argon (T6), (vii) 80% nitogen (T7), (viii) 85% nitogen (T8), (ix) 90% nitogen (T9), and (x) normal air (T10). Heme-pigment solutions (both Hb and Mb) were exposed with each treatment for four separate durations of time (30 s, 1 min, 2 min, and 4 min); and every sample (Hb and Mb) was exposed during each duration of time for 10 times (n = 10). In the rabbit experiment, seven treatments were used (i) 85% carbon dioxide (T1), (ii) 90% carbon dioxide (T2), (iii) 85% argon (T3), (iv) 90% argon (T4), (v) 96% nitrogen (T5), (vi) 98% nitogen (T6), and (vii) the Halal method (non-stunning) (T7). Forty-two rabbits (mixed-breed) were collected from the nearest commercial farm and randomly selected for a treatment group (n = 6). The average body weight was 2.3 kg. For stunning, each individual rabbit was separately kept in a gas chamber, after which each specific gas was used to fulfill the desired level in the pit. After reaching the desired level of concentration, rabbits were stunned within a very short time. It was observed that the time required for stunning in the T1, T2, T3, T4, T5 and T6 treatment was 79–82, 68–73, 97–103, 88–91, 164–173, and 108–115 s, respectively. In the case of the Halal method (non-stunning), as per the rules of Islam, rabbits were slaughtered without stunning. After slaughtering, in all treatments, the blood, meat, and small intestine of each animal were collected carefully and kept in a cool room in which the temperature was −2 °C, and after 24 h, the color attributes—lightness (L*), redness (a*), and yellowness (b*)—were measured via a Chroma Meter. It was found that in both experiments (trial on heme-pigment solutions and rabbit stunning), the color values (L*, a* and b*) showed a significant difference (p < 0.05) among the treatment groups. The CO₂-treated groups showed high redness (a*) and low lightness (L*) and yellowness (b*), which indicated a dark-red color, and N₂-treated groups showed high lightness (L*) and yellowness (b*) and low redness (a*), which implied a bright-red color. The effect of the Ar was in between the CO₂- and N₂-treated groups. These phenomena were observed both in the heme-pigment solutions (Hb and Mb) and in the blood, meat, and small intestine of the rabbits. N₂-stunned animals fulfill the fundamental desire of consumers to purchase bright red-colored fresh meat. Therefore, in view of color attributes, consumer satisfaction, and animal welfare, N₂ gas can be thought of as a valuable alternative to stunning. Considering the time required for complete stunning and desirable color attributes, a 98% concentration of N₂ is best for rabbit stunning. As such, it could be used as a better option for the gas stunning of animals.