Based on proteomics probing into the deterioration mechanism of pork batter gel caused by different cooking temperatures.

The purpose of this experiment was to explore the influence of different cooking temperatures on the deterioration characteristics of pork batter gel by using proteomics, gel electrophoresis, size and chemical bond of aggregates. The results showed that the protein molecules of the pork batter gel was degraded during heating cooking and the protein aggregates were composed of many degraded protein fragments; compared with the control group 75 °C (0 min), the significant degradation of cytoskeleton showed at 110 °C (30 min) and 121 °C (30 min) and the significant degradation of myosin complexonly appeared at 121 °C (30 min). As the heating temperature points increased, compared with the control group 75 °C (0 min), the different temperatures could promote the separation of metal ions with proteins especially at 110 °C (30 min) and 121 °C (30 min), which could ultimately influence quality of pork batter gel by the size of particle. As the increase of heating temperature points, the recombination of aggregates composed of different proteins was not conducive to the retention of capillary water, which reduced the texture of pork batter gel. This research provided theoretical support for improving the process property of the meat products.

Influence of beeswax-based fish oil oleogels on the mechanism of water and oil retention in Pacific white shrimp (Litopenaeus vannamei) meat emulsion gels: Filling, emulsification and phase transition.

Oleogels have been used in the gelled surimi products to replace animal fats due to its structure characteristics. The effect of structure characteristics in fish oil oleogels on the mechanism of oil/water retention was investigated in meat emulsions. Beeswax assembly improved the oil and water retention. The unsaturation degree of fatty acids lowered the mobility of bound water, immobilized water as well as bound fat in the fish oil oleogel, but enhanced the mobility of free water and protons of unsaturated fatty acids. Beeswax addition and oil phase characteristics could enhance ß-sheets, disulfide bonds and hydrophobic force to improve the viscoelasticity, gel strength and oil/water retention. Beeswax assembly facilitated the tight micro-sol network and filling effect, and high unsaturation degree promoted the emulsification effect, thus reducing phase transition temperature and juice loss. The study could lay the foundation for development of gelled shrimp meat products with EPA and DHA.

Effects of protein aggregation induced by NaCl and temperature on gelation of silkworm (Antheraea pernyi) pupa raw powder.

Edible insects have great potential for producing protein-rich ingredients. This study aimed to investigate the effects of protein aggregation induced by NaCl (0-1 M) and temperature (65-95 °C) on gelation of Antheraea pernyi (A. pernyi) pupa raw powder. No thermal aggregates were observed at low temperature (65 °C), on the basis of there being no significant enhancement in turbidity and particle size (P > 0.05), regardless of NaCl concentrations. At elevated temperatures (75-95 °C), protein solutions exhibited significantly higher turbidity and particle size (P < 0.05), accompanied by an initial rise in surface hydrophobicity followed by a decline, alongside declining sulfhydryl. This marks the beginning of massive thermal aggregation driven by molecular forces. In addition, covalent (disulfide bonds) and non-covalent (hydrogen bonding, electrostatic interactions, and hydrophobicity) forces were influenced by NaCl, leading to variability in the protein aggregation and gelation. Correlation analysis indicates that the higher protein aggregation induced by ions was beneficial to the construction of more compact three-dimensional structures, as well as to the rheology, texture, and water-holding capacity of A. pernyi pupa gels. However, excessive salt ions destroyed the gel structure. Our findings will aid the use of A. pernyi pupae as textural ingredients in formula foods.

Regulation mechanism of curcumin-loaded oil on the emulsification and gelation properties of myofibrillar protein: Emphasizing the dose-response of curcumin.

The regulation mechanism of curcumin (CUR) in the oil phase on the emulsification and gelation properties of myofibrillar protein (MP) was investigated. CUR enhanced the emulsifying activity index (EAI) of MP but decreased its turbiscan stability index (TSI) and surface hydrophobicity, which exacerbated oil droplet aggregation. Medium amounts (200 mg/L) of CUR changed the 3D network architectures of emulsion gels from lamellar to reticular, improving the gels' water-holding capacity (WHC), storage modulus, springiness, and cohesiveness. Besides, the LF-NMR revealed that CUR had limited effects on the mobility of immobilized and free water. The α-helix of MP in gels with medium amounts of CUR decreased from 51% to 45%, but the ß-sheet increased from 23% to 27% compared to those without CUR. Overall, CUR has the potential to become a novel structural modifier in emulsified meat products due to its dose-response.

A review of oil and water retention in emulsified meat products: The mechanisms of gelation and emulsification, the application of multi-layer hydrogels.

Emulsified meat products are key deep-processing products due to unique flavor and high nutritional value. Myosin dissolves, and protein aggregation and heat-induced gelation occur after myosin unfolds and hydrophobic groups are exposed. Myosin could form interfacial protein membranes and wrap fat globules. Emulsified fat globules may be filled in heat-induced gel networks. Therefore, this review intends to discuss the influences of heat-induced gelation and interfacial adsorption behavior on oil and water retention. Firstly, the mechanism of heat-induced gelation was clarified from the perspective of protein conformation and micro-structure. Secondly, the mechanism of emulsification stability and its factors affecting interfacial adsorption were demonstrated as well as limitations and challenges. Finally, the structure characteristics and application of multi-layer hydrogels in the gelation and emulsification were clarified. It could conclude that the characteristic morphology, spatial conformation and structure adjustment affected heat-induced gelation and interfacial adsorption behavior. Spatial conformation and microstructure were adjusted to improve the oil and water retention by pH, ionic strength, amino acid, oil phase characteristic and protein interaction. Multi-layer hydrogels facilitated oil and water retention. The comprehensive review of gelation and emulsification mechanisms could promote the development of meat products and improvement of meat processing technology.

Pickering emulsion stabilized by modified pea protein-chitosan composite particles as a new fat substitute improves the quality of pork sausages.

Pickering emulsion is a potential substitute for animal fat due to high stability and solid-like properties. Therefore, the effect of replacing 25%-100% pork backfat with Pickering emulsion (75% corn oil volume fraction) stabilized by modified pea protein-chitosan composite particles on the quality of sausages was studied. All meat pastes exhibited a strong gel-like rheological character (G' > G"). The incorporation of Pickering emulsion in sausages enhanced the textural properties (hardness, springiness, chewiness, cohesiveness and resilience) and the uniformity and compactness of micromorphology, as well as suppressed the cooking loss and TBARS content. In particular, the sausages with a backfat substitution ratio of 100%, showing a similar overall sensory acceptability to the backfat sausage, revealed the best rheological properties, texture properties and micromorphology and the lowest cooking loss and fat oxidation (P < 0.05). The results showed that Pickering emulsion stabilized by modified pea protein-chitosan composite particles is a potential fat substitute for meat products with the desirable characteristics.

Effects of tetrasodium pyrophosphate coupled with soy protein isolate on the emulsion gel properties of oxidative myofibrillar protein.

The effects of protein oxidation on the emulsion gel properties of myofibrillar protein (MP) in the presence of tetrasodium pyrophosphate (TSPP) and soybean protein isolate (SPI) were investigated from the perspective of interfacial protein interactions. The results showed that the emulsifying activity and emulsion stability of MP increased by 35.2 %-181.6 % with elevated H2O2 concentrations (1-20 mM), while the gel strength and water holding capacity of MP emulsions first increased to a maximum at 5 mM H2O2 and then decreased. TSPP and SPI further reinforced the effects caused by oxidation. The emulsifying properties of MP and its emulsion gel properties were closely related to surface hydrophobicity/hydrogen bonds/hydrophobic interactions and disulfide bonds among interfacial proteins, respectively. However, these correlations became difficult to define when TSPP and SPI were introduced. The study provides a theoretical basis for the strategy development to reduce protein oxidation damage on meat product quality.

Effect of fatty acid saturation on gel properties of salt-soluble protein in pork.

The objective of this study was to evaluate the effect of fatty acid saturation (oleic acid, linoleic acid, and linolenic acid) on water distribution, migration, and gel properties of pork salt-soluble protein, by detected indicators that are Low field nuclear magnetic resonance (LF-NMR), magnetic resonance imaging (MRI), water-holding capacity (WHC), and gel strength. These results suggested that the WHC and gel strength decreased with the decrease of fatty acid saturation (p < 0.05). LF-NMR analysis revealed that the relaxation time T21 and T22 decrease (p < 0.05) with the decrease of fatty acid saturation. Results also showed that the T21 increased and T23 decreased in linolenic acid group compared with oleic acid group. Meanwhile, the peak area ratio of P21 and P22 decreased (p < 0.05), while P23 increased (p < 0.05). Therefore, the saturation of fatty acids had a great influence on the gel properties of protein. PRACTICAL APPLICATION: It provides a theoretical basis for the production of polyunsaturated fatty acids emulsified gel meat products and promotes the development of meat processing industry.

UV dose effects on the revival characteristics of microorganisms in darkness after UV disinfection: Evidence from a pilot study.

Ultraviolet (UV) disinfection during water supply treatment aims to reduce the number of bacteria. Although UV disinfection is effective at inactivating most microorganisms, some microbe species may be entirely impervious. A pilot study was conducted to compare the quantity and community component of bacteria in surface water collected from filtration effluent before UV disinfection with different doses of UV, and those 1 and 2 days afterwards, in darkness. The aim was to elucidate the relationship between the UV dose and the total revived microorganisms in darkness after UV disinfection. In the filtration effluent samples, Gammaproteobacteria, Bacilli, Actinobacteria, and Alphaproteobacteria were the predominant classes. After storage in the dark at a constant temperature of 19 °C, the UV-disinfected samples showed a considerable increase in Bacilli, while Gammaproteobacteria remained the predominant population. Genera such as Exiguobacterium, Citrobacter, Acinetobacter, and Pseudomonas presented a selective advantage in terms of revival in darkness after UV disinfection, irrespective of the UV dose and storage time. The lowest rate of microbial revival (5% day-1) was noted at a UV dose of 266.10 mJ m-2 (with an average UV illumination time of 124.4 s and an average intensity of 86.61 W m-2). Our results suggest that higher UV intensity and lower illumination time are key factors in minimizing the revival of microorganisms in darkness.

Effect of secondary heat-induced aggregation on pork meat batter protein conformation, hydration characteristics, textural quality and in vitro digestibility.

Secondary heating (SH, 30 min at 100 °C), which has a great influence on elastic gels, has been widely applied to emulsified meat products to extend their shelf life. The effects of SH on the textural and nutritional qualities, water migration of meat batter and on the conformations, aggregation and in vitro digestibility of the meat proteins were investigated. Various heat treatments were tested, and the results revealed that an initial heating at 75 °C yielded the highest low-field NMR relaxation time T22 and peak area P22 and the highest in vitro digestibility. As this initial heating time was increased, the α-helix content, water-holding capacity (WHC) and protein digestibility all decreased. Furthermore, SH yielded a much more obvious decrease in the pepsin activity on the protein digestibility than just the initial heating, and also yielded increases in ß-sheet content, hardness, gumminess, and chewiness. This result implied that gel shrinkage and protein aggregation occurred, causing decreased WHC and protein digestibility. Also, SH resulted in significantly decreased (P < 0.05) intensities of myosin light chain gel electrophoresis bands. Therefore, SH was concluded to have reduced the textural quality and nutritional value of the meat.

The study of protein conformation and hydration characteristics of meat batters at various phase transition temperatures combined with Low-field nuclear magnetic resonance and Fourier transform infrared spectroscopy.

To get a thorough understanding of evolution of heat-induced gel in meat batters, water distribution, protein conformation and their chemical bonds at phase transition temperatures (20-74 °C) were investigated by Low-field NMR and FT-IR. Firstly, G' increased and tanδ decreased beyond 55 °C, when sol was completely changed into an elastic gel. Then water holding capacity (WHC) decreased along with decreasing relaxation time T22 and a new relaxation time T23 appeared at 50 °C, which indicated that partially immobilised water was converted into free water outside. Meanwhile, surface hydrophobicity increased significantly and free sulfhydryl contents decreased, which contributed to the formation of disulfide bonds, especially beyond 55 °C. Finally, the transformation of α-helix into ß-sheets occurred, and increasing ß-sheets are necessary for the formation of elastic gels. Moreover, there was a significant correlation between α-helical contents and water loss, surface hydrophobicity, sulfhydryl contents.

Effect of chopping time and heating on 1 H nuclear magnetic resonance and rheological behavior of meat batter matrix.

The effect of chopping time and heating on physicochemical properties of meat batters was investigated by low-field nuclear magnetic resonance and rheology technology. Cooking loss and L* increased while texture profile analysis index decreased between chopping 5 and 6 min. The relaxation time T21 (bound water) and its peak area ratio decreased, while the ratio of T22 peak area (immobilized water) in raw meat batters gradually increased with the extension of chopping time. However, T22 was opposite after being heated and a new component T23 (free water) appeared (T2i is the spin - spin relaxation time for the ith component.). The initial damping factor (Tan δ) gradually decreased and there were significant difference between 4 and 5 min of chopping time. There were significantly positive correlations between the ratio of peak area of T22 and chopping time, the storage modulus (G'), cooking loss, and L*, respectively. Continued chopping time could improve the peak area proportion of T22 in raw meat batters. Further, the higher the peak area proportion of T22 in raw meat batters, the cooking loss of heated meat gel was higher. Also, the stronger the mobility of immobilized water in meat batter, the higher the L* of the fresh meat batters. Thus, it is revealed that the physicochemical properties of meat batter are significantly influenced by chopping time which further affects the water holding capacity and the texture of emulsification gel.

Low-field NMR determination of water distribution in meat batters with NaCl and polyphosphate addition.

The objective was to elucidate the influence of NaCl and polyphosphates in the stage of protein swelling on the water-holding capacity (WHC) of meat batter. The meat batters were formulated with salt in different ways by adding established amounts of only NaCl, only polyphosphates, jointly adding NaCl and polyphosphates, and a control without any salt. An increase (p<0.05) in water retention was found when a combination of NaCl and polyphosphates was used. A high textural parameter was observed in the two treatments with NaCl, but not in the group with only polyphosphate. For the polyphosphate group, T22 was lower (p<0.05) than in the other three before heating; however, after heating, T21 and T22 were both significantly decreased, and a new component emerged, T23, which was significantly lower than the others. For the NaCl treatment, heated or not, T22 was always the highest. It was revealed that NaCl had affected the WHC by increasing the mobility and distribution of water, particularly with polyphosphate, but polyphosphate could not be an equal substitute for NaCl given its resulting lowest textural properties and poor microstructure. By presenting different hydration states in the protein swelling stage, the meat batter qualities were differentiated.