Effect of LTLT heat treatment on cathepsin B and L activities and denaturation of myofibrillar proteins of pork

Perspective of sodium reduction based on endogenous proteases via the strategy of sodium replacement in conjunction with mediated-curing

NaCl is the main curing agent in dry-cured meat products, and a large amount of NaCl addition leads to high salt content of final products. Salt content and composition are important factors affecting the activity of endogenous proteases, which in turn could affect proteolysis as well as the quality of dry-cured meat products. With the increasing emphasis on the relationship between diet and health, reducing sodium content without sacrificing quality and safety of products is a great challenge for dry-cured meat industry. In this review, the change of endogenous proteases activity during processing, the potential relationship between sodium reduction strategy, endogenous proteases activity, and quality were summarized and discussed. The results showed that sodium replacement strategy and mediated-curing had a complementary advantage in influencing endogenous proteases activity. In addition, mediated-curing had the potential to salvage the negative effects of sodium substitution by affecting endogenous proteases. Based on the results, a sodium reduction strategy that sodium replacement in conjunction with mediated-curing based on endogenous proteases was proposed for the future perspective.

Effect of accelerated aging on shelf-stability, product loss, sensory and biochemical characteristics in 2 lower quality beef cuts

The aim of this study was to determine the impact of accelerated aging (AA) on shelf stability, product loss, sensory and biochemical characteristics of 2 lower quality beef cuts. Triceps brachii (TB) and semimembranosus (SM) were collected and fabricated from 10 USDA Choice beef carcasses and assigned to 1 of 6 treatments: 3 d cooler aged (control), 21 d cooler aged, AA 49 °C for 2 h, AA 49 °C for 3 h, AA 54 °C for 2 h, and AA 54 °C for 3 h. The results showed that AA can decrease APC counts on steak surface and in purge and redness, but increase lightness and product loss of the steaks (P < 0.01). Lower shear force was also found for AA steaks compared to those from the control (P < 0.01), with the AA 54 °C treatments being comparable to 21 d cooler aging. However, the trained sensory panel determined AA steaks were less juicy and flavorful than those from the control and 21 d cooler aged samples (P < 0.05). There was no off-flavor detected in AA steaks though lipid oxidation was higher in AA samples than those in the control steaks (P < 0.01). The AA treatments stimulated cathepsin activity (P < 0.05), which may have enhanced the solubilization of stromal proteins and led to a different troponin-T degradation pattern compared to those from the 21 d aged samples (P < 0.01). Although AA is an economical and time-efficient method to increase tenderness of lower-quality beef cuts, further research is needed to determine strategies to mitigate the decrease in juiciness from AA treatments.

Impact of L-arginine on the quality of heat-treated Antarctic krill: Influence of pH and the guanidinium group

Antarctic krill suffers from severe water loss after heating, and its quality deteriorates, so it is in urgent need of a green and healthy improver. In this paper, the effects of L-arginine (L-Arg) soaking on the modification of the quality of heat-treated Antarctic krill and the structure of myofibrillar proteins (MPs) in Antarctic krill were investigated. The results showed that L-Arg had an ameliorating effect on heat-treated krill in a concentration-dependent relationship. The water-holding capacity of L-Arg-soaked krill was 1.41 times higher than that of sodium tripolyphosphate (STPP) at an equivalent concentration (80 mM). At 120 mM L-Arg soaked, L* and hardness of krill decreased to 58.31 and 334.81 g, while resilience and moisture content increased to 0.47 and 85.29 % after heating, respectively. The scanning electron microscopy (SEM) results revealed that the tissue state of the pH-corrected groups was better than the control, but not as well as that of the pH-uncorrected groups. pH and the guanidinium group in L-Arg both played roles in promoting the transition of MPs from disordered to ordered secondary structures. This transition reduced the exposure of hydrophobic and sulfhydryl groups in MPs, inhibited the protein aggregation and increased the solubility of MPs to 71.61 %, which ultimately improved the quality of heat-treated krill. It is worth noting that the pH effect had a primary influence on the observed effects, while the guanidinium group made a secondary contribution. These results could broaden the potential application of L-Arg as an improver of the quality of heat-treated krill.

High-intensity ultrasound combined with glycation enhances the thermal stability and in vitro digestion behaviors of myofibrillar protein aqueous solution

The low thermal stability of myofibrillar proteins (MPs) is a technological barrier to them being applied in beverage formulas. In this study, we investigated the effect of high-intensity ultrasound (HIU) pretreatment combined with glycation on the thermal stability, structural characteristics, and in vitro digestion behavior of MPs in water. The results indicated that HIU pretreatment combined with glycation significantly inhibited thermal aggregation and reduced the particle size of MPs compared to using either HIU or glycation treatments individually. The grafting of dextran (DX) shielded the sulfhydryl (-SH) and hydrophobic groups and inhibited disulfide bond cross-linking and hydrophobic association. Moreover, HIU pretreatment facilitated the shielding effect of glycation by destroying the filamentous myosin structure and exposing the internal -SH and hydrophobic groups as well as the grafting sites, maximally inhibiting thermal aggregation. In addition, the smaller protein particles and more flexible structure caused by HIU pretreatment combined with glycation increased their binding affinity toward protease. Overall, these findings can promote the technological development of modulating the MP structure-digestion for formulating novel meat protein-based products.

Improved tenderness and water retention of pork pieces and its underlying molecular mechanism through the combination of low-temperature preheating and traditional cooking

The effects of two-stage heating with different preheating combinations on the shear force and water status of pork-pieces were explored. The results showed that the combined preheating at 50 ℃ for 35 min or at 60 ℃ for 5 or 20 min with traditional high temperature heating reduced the shear force and improved the water retention of meat, which was attributed to uniformly separation of myofibers and smaller myofiber space. Visible dissociation of actomyosin in heating groups of 50 ℃-35 min, and 60 ℃-5, 20 min was related to the tenderization of meat. The higher surface hydrophobicity, tryptophan fluorescence intensity, and lower α-helices of actomyosin at 60 ℃ contributed to the liberation of actin. However, severe oxidation of sulfhydryl groups at 70 ℃ and 80 ℃ promoted the aggregation of actomyosin. This study presents the advantage of two-stage heating in improving meat tenderness and juiciness and its underlying mechanisms.

Synergistic effect of preheating and different power output high-intensity ultrasound on the physicochemical, structural, and gelling properties of myofibrillar protein from chicken wooden breast

The effects of preheating to 50 ℃ and the subsequent application of high-intensity ultrasound (HIU, 20 kHz) at 200, 400, 600, and 800 W on the physicochemical, structural, and gelling properties of wooden breast myofibrillar protein (WBMP) were studied. Results suggested that the WBMP structure expanded to the balanced state at 600 W, and rheological properties exhibit that 600 W HIU (P < 0.05) significantly improved the storage modulus (G') of WBMP. Notably, the WBMP gel (600 W) had the best hardness (65.428 ± 0.33 g), springiness (0.582 ± 0.01), and water-holding capacity (86.11 ± 0.83%). Raman spectra and low-field NMR indicated that 600 W HIU increased the β-fold content (37.94 ± 0.04%) and enlarged the immobilized-water proportion (93.87 ± 0.46%). Scanning electron micrographs confirmed that the gel was uniform and dense at 600 W. Therefore, preheating to 50 ℃ followed by HIU (600 W) helped form a superior WBMP gel.

Sous Vide Cooking Effects on Physicochemical, Microbiological and Sensory Characteristics of Pork Loin

Pork loin slices were sous vide cooked at 60 °C and 65 °C for 2 h, 3 h and 4 h, and at 70 °C and 75 °C for 1 h, 1.5 h and 2 h. The cooking loss of the meat samples significantly increased with the temperature and time of heat treatment, but no correlation between cooking loss and moisture content in the samples was noted. All samples showed similar pH and water activity values. Regarding colour parameters, only yellowness showed significant differences between the samples and was affected by the temperature and time of cooking. Texture profile analysis revealed the lowest hardness of the samples cooked at 60 °C. Sensory analysis showed that cooking at 60 or 65 °C for 4 h ensured the most acceptable sensory features of the investigated samples, and tenderness and juiciness influenced the overall acceptability in the highest degree. All samples were microbiologically safe for consumption.