Pediococcus pentosaceus, Lactobacillus curvatus, Lactobacillus sakei and Staphylococcus xylosus were evaluated to determine their roles in the lipolysis and lipid oxidation in Harbin dry sausages and ...their relation to flavour development. The free fatty acid (FFA) contents of both muscle and fat tissues were higher in the inoculated sausages than those of the non-inoculated control, especially with mixed strains (P < 0.05). The predominant FFAs in both tissues at the end of the fermentation were palmitic acid, stearic acid and oleic acid. The inoculation of dry sausages with bacterial strains, especially mixed strains, significantly decreased the peroxide value and thiobarbituric acid reactive substances (P < 0.05). Furthermore, a lower level of volatile compounds related to lipid-oxidation, such as aldehydes, ketones and hydrocarbons, was observed in the inoculated sausage (P < 0.05). The results demonstrate that Harbin dry sausage can be inoculated with a starter culture mixture of P. pentosaceus, L. curvatus and S. xylosus to promote lipid hydrolysis, inhibit lipid autoxidation and improve fermented flavour development.
•Bacterial fermentation promoted lipid hydrolysis and inhibited lipid autoxidation.•The predominant free fatty acids were palmitic acid, stearic acid and oleic acid.•Bacterial fermentation decreased PV and TBARS in Harbin dry sausages.•Fermentation with multiple strains reduced undesirable flavour development.
This study investigated the effects of multiple freeze-thaw (F-T) cycles on water mobility, microstructure damage and protein structure changes in porcine longissimus muscle. The transverse ...relaxation time T2 increased significantly when muscles were subjected to multiple F-T cycles (P<0.05), which means that immobile water shifted to free water and the free water mobility increased. Multiple F-T cycles caused sarcomere shortening, Z line fractures, and I band weakening and also led to microstructural destruction of muscle tissue. The decreased free amino group content and increased dityrosine in myofibrillar protein (MP) revealed that multiple F-T cycles caused protein cross-linking and oxidation. In addition, the results of size exclusion chromatography, circular dichroism spectra, UV absorption spectra, and intrinsic fluorescence spectroscopy indirectly proved that multiple F-T cycles could cause protein aggregation and degradation, α-helix structure disruption, hydrophobic domain exposure, and conformational changes of MP. Overall, repeated F-T cycles changed the protein structure and water distribution within meat.
•An increased T2 means the F-T cycles caused immobile water to shift to free water.•Multiple F-T cycles caused protein cross-linking, degradation and oxidation.•The microstructure of muscle tissue was disrupted by multiple F-T cycles.•Repeated F-T cycles had a detrimental effect on the protein structure and WHC.
•Addition of PPPH led to inadequate gelatinization of corn starch.•PPPH facilitated water mobility in the crystalline structure of starch.•Addition of PPPH facilitated the reorganization of ...crystalline regions.•PPPH interfered with the nucleation of amylopectin and inhibited CS retrogradation.
The potential effect of porcine plasma protein hydrolysates (PPPH) on the long-term retrogradation of corn starch (CS) was investigated. The differential scanning calorimetry results showed that PPPH significantly reduced the retrogradation enthalpies (ΔHr) of CS (P<0.05), obviously decreased the crystallization rate constant (k), and enhanced the Avrami exponent (n) (P<0.05). Low-field nuclear magnetic resonance analysis demonstrated that the spin–spin relaxation time (T2) remarkably increased with increasing PPPH concentration during storage at 4°C for 28days (P<0.05). The X-ray diffraction results revealed that the relative crystallinity of retrograded CS decreased from 13.04% to 8.73% with the addition of PPPH. Fourier transform infrared spectroscopy analysis demonstrated that the addition of PPPH led to a decrease in hydrogen bonds within starch. The results demonstrated that the addition of PPPH apparently played a crucial role in retarding the long-term retrogradation of CS.
The effect of ultrasound-assisted immersion freezing at 180 W (UIF-180) on the microstructure, quality and water distribution of porcine longissimus muscles during frozen storage was evaluated. The ...size of the ice crystals increased with extended storage time, and UIF-180 samples had a smaller size and uniform distribution of ice crystals. The thawing and cooking losses in the UIF-180 sample were significantly lower than that in air freezing (AF) and immersion freezing (IF) samples (P < 0.05). AF samples had a higher cutting force at 0 days. During the 60–180 days of the storage period, the cutting force of UIF-180 samples was significantly higher than that of AF and IF samples (P < 0.05). Low field-nuclear magnetic resonance results showed that UIF-180 decreased water migration during frozen storage. UIF-180 samples had significantly lower lipid oxidation and higher redness than that of the AF and IF samples (P > 0.05). Overall, UIF at particular powers is an efficient method in reducing quality deterioration of muscles during long-term frozen storage.
•UIF-180 sample had small and uniform distribution of ice crystals during storage.•UIF treatment reduced the thawing and cooking losses and lipid oxidation of samples.•UIF-180 samples had a shorter T2 relaxation time during frozen storage.•UIF at certain powers is as an efficient method in reducing quality deterioration.
Tea polyphenol (TP), apple polyphenol (AP), and cinnamon polyphenol (CP) are all enriched with antioxidant components, present enormous potential as natural antioxidants in meat products. The ...objective of this study was to evaluate the physicochemical properties, residual nitrites, and formation of N-nitrosamine (NA) in dry-fried bacons with three aforementioned plant polyphenols and ascorbic acid (AA). The results show that both plant polyphenols and AA significantly reduced pH, lipid oxidation and residual nitrite content when compared to the control (P < 0.05). Only AP exhibited a protective effect against protein oxidation-induced damage in bacon, and N-nitroso-methyl phenylamine (NMPhA) contents were significantly affected by plant polyphenols (P < 0.05). Bacon containing 300 mg/kg AP produced less thiobarbituric acid reactive substance (TBARS) (0.59 MDA/kg), carbonyl contents (2.30 nmol/mg protein) and NMPhA formation (1.211 ng/kg). In conclusion, plant polyphenols, particularly AP, have the potential to be used as natural antioxidants for reducing oxidation and nitrite application level while also improving the safety of bacon.
•Apple polyphenol (AP) was more effective in reducing nitrite and N-nitrosamine (NA) contents.•AP increased the bio-safety of smoked bacon in this study.•The optimal and recommended addition of AP in smoked bacon is 300 mg/kg.
The inhibitory effect of ice structuring protein (ISP) on the quality deterioration of quick-frozen pork patties subjected to multiple freeze-thaw (F-T) cycles was investigated. The inhibitory effect ...of ISP on patty quality deterioration was obvious after five F-T cycles (P < 0.05). The hardness and springiness of patties with 0.20% ISP were 3.84% and 10.61% higher than those of patties without ISP, and the thawing loss of patties with 0.20% ISP was 43.64% lower than that of patties without ISP (P < 0.05). In addition, ISP effectively restrained moisture migration and destruction of pork patty microstructure during F-T cycles. More importantly, thiobarbituric acid reactive substance levels and carbonyl contents in the patties with 0.20% ISP were 25% and 32% lower than those in the control group (no significant difference with patties with 0.30% ISP) after five F-T cycles. Therefore, these results illustrated the potential benefits of ISP in meat products.
•Freeze-thaw (F-T) cycles accelerated quality deterioration of pork patties.•Ice structuring protein (ISP) inhibited patty deterioration induced by F-T cycles.•The inhibitory effect of 0.20% ISP on patty quality decline was obvious.•ISP retarded protein and lipid oxidation of patties during F-T cycles.
This study investigated the impact of air thawing (AT), water thawing (WT) and ultrasound-assisted immersion thawing (UT) at different power levels (200, 300, 400, and 500 W) on the emulsifying and ...gelling properties of the myofibrillar protein (MP). UT at 300 W (UT-300) significantly improved the solubility and the absolute ζ-potential value of MP, reduced the turbidity and the particle size of MP, lowered the loss of gel strength and water holding capacity, and promoted the formation of a stable emulsion (P < 0.05). Compared to the AT and WT samples, the UT-300 MP gels had shorter T21 and T22, which revealed that UT-300 had reduced mobility and losses of the immobilized and free water. The observation of the gel microstructure indicated that the UT-300 samples had compact and homogeneous MP gel network. As a result, appropriate ultrasonic power reduced the losses of the emulsifying properties (emulsifying activity index and the emulsion stability index) and gelling properties (gel water-holding capacity and gel strength) of MP.
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•Ultrasound-assisted immersion thawing (UT) reduced loss of gel strength and WHC.•UT at 300 W (UT-300) decreased the turbidity and particle size of MP samples.•An appropriate ultrasound power promoted the formation of stable emulsion.•UT-300 samples had less mobility and losses of immobilized and free water.•The samples treated with 300 W had compact and homogeneous MP gel network.
•Soy protein isolates were modified by an acidic pH treatment with mild heating.•Modified soy protein isolates were added to myofibrillar protein solutions.•Thermal stability and gel molecular forces ...of myofibrillar protein were improved.•Mixed gels displayed a more continuous and homogeneous gel network.
Thermal stability and gel quality of myofibrillar protein were evaluated with regard to the addition of native soy protein isolates (SPI) and SPI subjected to acidic pH and mild heating (modified SPI). Compared with the control, the addition of modified SPI increased the compression force of the protein gel and decreased water loss (P<0.05). Differential scanning calorimetry results showed that an addition of 0.75% native SPI decreased the first transition temperature (P<0.05), and addition of 0.5% and 0.75% modified SPI exhibited no appreciable changes on it (P>0.05), indicating that a higher concentration of modified SPI would not damage the protein thermal stability. Moreover, the addition of modified SPI enhanced hydrogen bonding and disulphide linkages. Atomic force microscopy analysis revealed that the addition of modified SPI decreased the roughness of the mixed myofibrillar protein gels. Overall, modified SPI has the potential to improve myofibrillar protein gel texture and water holding capacity.
•Aggregation behavior of myofibrillar protein (MP) was affected by pH and temperature.•Heating could promote the structural unfolding of MP.•Aggregation and unfolding of MP at pH 6.0 was balanced ...during heating process.•MP gel network structure was uniform and dense at pH 6.0 above 70 °C.
The synergistic effect of pH and heating on the structure, aggregation behaviour and gel properties of myofibrillar protein (MP) in mirror carp (Cyprinus carpio) was evaluated. The surface hydrophobicity of the control at pH 5.0 (143.6 ± 0.3 μg) was significantly higher than that of other samples (P < 0.05). Under the same pH conditions, the decrease in total sulfhydryl content of all samples during the heating process demonstrated that covalent/non-covalent cross-linking occurred between proteins due to heat input. Moreover, the decrease in solubility and the increase in turbidity of all samples verified the fact of MP aggregation, and the changes in the elasticity index (EI) and macroscopic viscosity index (MVI) also indicated a decrease in MP fluidity upon heating treatment. Therefore, the aggregation of MP was affected by pH and heating, and the optimal three-dimensional network structure and gel properties could be formed at pH 6.0 and above 70 °C.
•Effect of thawing method on thermal stability and structure of protein was analyzed.•Change in thermal stability of MP induced by thawing method was significant.•Change in structure of protein ...induced by different thawing methods was demonstrated.•Compared to FM, change in thermal stability and structure from VT was insignificant.
This study investigated the effects of thawing methods on the thermal stability and structure of myofibrillar protein (MP) from porcine longissimus dorsi. DSC was used to evaluate the thermal stability (Tmax, △H) of MP. FT-IR, Raman, UV absorption, and fluorescence spectra were utilized to assess the secondary and tertiary structures of MP. Changes in the thermal stability and structure of MP after thawing were significant (P < 0.05), except for the vacuum thawing (VT) samples. The lowest Tmax and △H were obtained through microwave thawing (MT). The decreases in α-helices, β-sheets, fluorescence intensity, and total sulfhydryl content, and increases in the intensity of the SS stretching band and Ca2+-ATPase activity illustrated that secondary structure destruction, tertiary structure unfolding, and disulphide bond cross-linking occurred during thawing. The thawing process caused thermal stability degradation and structure destruction; the largest changes in all indexes of MP were obtained through MT.
