The Protection of Quinoa Protein on the Quality of Pork Patties during Freeze-Thaw Cycles: Physicochemical Properties, Sensory Quality and Protein Oxidative

The present study investigated the impact of quinoa protein (QP) on the physicochemical properties, sensory quality, and oxidative stability of myofibrillar protein (MP) in pork patties during five freeze-thaw (F-T) cycles. It was observed that repeated F-T cycles resulted in a deterioration of pork patty quality; however, the incorporation of QP effectively mitigated these changes. Throughout the F-T cycles, the sensory quality of the QP-treated group consistently surpassed that of the control group. After five F-T cycles, the thiobarbituric acid reactive substance (TBARS) content in the control group was measured at 0.423 mg/kg, whereas it significantly decreased to 0.347 mg/kg in the QP-treated group (p < 0.05). Furthermore, QP inclusion led to a decrease in pH and an increase in water-holding capacity (WHC) within pork patties. Following five F-T cycles, Ca2+-ATPase activity exhibited a significant increase of 11.10% in the QP-treated group compared to controls (p < 0.05). Additionally, supplementation with QP resulted in elevated total sulfhydryl content and reduced carbonyl content, Schiff base content, and dityrosine content within myofibrillar proteins (MPs), indicating its inhibitory effect on MP oxidation. In particular, after five F-T cycles, total sulfhydryl content reached 58.66 nmol/mL for the QP-treated group significantly higher than that observed for controls at 43.65 nmol/mL (p < 0.05). While carbonyl content increased from 2.37 nmol/mL to 4.63 nmol/mL between the first and fifth F-T cycle for controls; it only rose from 2.15 nmol/mL to 3.47 nmol/mL in the QP-treated group. The endogenous fluorescence levels were significantly higher (p < 0.05) in the QP-treated group compared to controls. In conclusion, the addition of QP enhanced the quality of pork patties and effectively inhibited the oxidative denaturation of MP during F-T cycles.

Effects of repeated freezing and thawing on myofibrillar protein and quality characteristics of marinated Enshi black pork

Repeated freeze-thaw is one of the main reasons for quality deterioration of frozen meat products. The study focused on the changes of endogenous fluorescence, secondary structure, microstructure, and water retention and distribution in marinated and unmarinated Enshi black pork after 10 freeze-thaw cycles. The results revealed that marinated treatment significantly reduced the thaw and centrifugal loss (P < 0.05), and increased endogenous fluorescence intensity of samples. During the entire freeze-thaw process, free water was undetectable in marinated group. After the first 4 cycles, α-helix percentage in marinated group was higher than that in control group. Scanning electron microscopy results suggested that there was no obvious increase in muscle fiber gap until 8 cycles in marinated group. Conclusively, moderate marination could slow down the deterioration of myofibrillar protein and pork quality, but it would be better to limit freeze-thaw cycles within 4 to maintain the quality of marinated Enshi black pork.

Identification of Microorganisms in Duck Meat Products Available in Korea and the Effect of High Hydrostatic Pressure

The objective of this study was to investigate the microbial count of duck meat and duck meat products commercially available in Korea. High hydrostatic pressure (HHP) treatment was applied at 0.1, 300, 400, and 500 MPa for 5 min to enhance the microbiological safety of duck meats. The levels of total aerobic bacteria were in the ranges of 3.53-6.19 and 3.62-6.85 Log CFU/g in raw and smoked duck products, respectively. By DNA sequence analysis, we identified microorganisms responsible for spoilage, with the most common species in the raw and smoked duck products being Aeromonas spp. or Pseudomonas spp. and Leuconostoc mesenteroides, respectively. HHP treatment significantly reduced the levels of total aerobic bacteria in raw and smoked duck products. This study demonstrates that HHP treatment may be used to effectively improve the safety of raw and smoked duck meat products.

Differentiation of Deboned Fresh Chicken Thigh Meat from the Frozen-Thawed One Processed with Different Deboning Conditions

This study was performed to evaluate the quality characteristics of three deboned categories of chicken thigh meat: one which was slaughtered and deboned in the same plant (fresh); one which was slaughtered, deboned, frozen, and thawed in the same plant (frozen-thawed); and the last which was slaughtered in a plant, deboned in a different plant, but then transferred to the original plant (fresh-outside). Surface color, drip loss, 2-thiobarbituric acid reactive substances (TBARS) value, sensory evaluation, and total aerobic bacterial counts of the chicken samples were determined. Moreover, the torrymeter was used to measure the differences in freshness of the chicken meat. The surface color and the TBARS values did not show significant differences among the three categories. However, the total aerobic bacterial counts of fresh-outside and frozen-thawed chicken meat were significantly higher than the fresh chicken meat on the first storage day, and the drip loss of frozen-thawed chicken meat was significantly higher than the fresh-outside and fresh chicken meat. In addition, the sensory evaluation of frozen-thawed chicken meat was significantly lower than the fresh-outside and fresh chicken meat. Torrymeter values were higher in fresh chicken meat than fresh-outside and frozen-thawed chicken meat during the storage period. These results indicate that the quality of frozen-thawed chicken meat is comparatively lower than the fresh chicken meat, and the torrymeter values can accurately differentiate the fresh-outside and frozen-thawed chicken meat from the fresh ones.