The effects of thawing methods (refrigeration thawing (RT, 4 °C), water immersion thawing (WT, 18 °C), vacuum thawing (VT, 25 °C), ultrasonic thawing (UT, 20 °C) and microwave thawing (MT)) on the ...conformation and gel qualities of myofibrillar protein (MP) obtained from porcine longissimus muscle were investigated. The results showed that MP conformation and gel qualities of porcine longissimus muscles by VT and UT were insignificantly changed compared to fresh meat (FM). A significant decrease in free amino groups of MP from MT illustrated that MT induced protein aggregation and oxidation (P < 0.05). The results of circular dichroism (CD) spectra analysis and fluorescence spectroscopy indirectly proved that thawing can cause protein cross-linking and degradation, secondary structure destruction, non-hydrophilic domain exposed and conformational change of samples. The largest changes in solubility, surface hydrophobicity and particle size were obtained with MT. The effects on the conformation and gel quality of MP were verified during thawing process.
•The effect of five thawing methods on gel quality of protein was compared.•Gel forming ability of protein has no obvious changes during novel thawing process.•The change of gel quality is induced by protein structural modification.
Display omitted
•Quality of patty during frozen storage was verified by WHC, a*, hardness.•Oxidation in patty during frozen storage was confirmed by TBARS and carbonyl content.•Changes in protein ...structure were measured by the fluorescence intensity.•Correlations among quality, protein oxidation and structure were analyzed by PCA.
Changes in quality, protein structure and oxidative reactions of quick-frozen pork patties (after −30 °C, 30 min), which were frozen at −8 °C, −18 °C, −25 °C, −8/−18 °C (stored at −8 °C for 5 days, then stored at −18 °C for 5 days, storage cycle continue until the end of storage period), −18/−25 °C (the same process as −8/−18 °C, temperature is −18 °C and −25 °C) for 0, 1, 2, 3, and 6 months were investigated. The a*-value, pH, water holding capacity and texture properties of pork patties were significantly changed (P < 0.05) at −8 °C, −8/−18 °C, −18/−25 °C after 1 month of frozen storage. The water redistribution within the patties was detected by LF-NMR analyses. After 6 months of frozen storage, the TBARS and carbonyl content of samples frozen at −8/−18 °C increased by 444% and 239%, respectively. Meanwhile, a decrease in fluorescence intensity reflected a decline in protein structure integrity. The association among quality, oxidative reactions and protein structure were elucidated by principal component analysis. The quality deterioration of the pork patties may be induced by the oxidative reaction and destruction of protein structural integrity during frozen storage.
Effects of different freeze–thaw cycles (0, 1, 3 and 5) on physicochemical change and protein oxidation in porcine longissimus dorsi were investigated. When the number of freeze–thaw cycles ...increased, the thawing losses, cooking loss and
b*-value increased (
P
<
0.05),
a*-value decreased (
P
<
0.05). The cutting forces of pork increased after one cycle of freeze–thaw (from 28.3
N to 40.4
N) (
P
<
0.05), but the further increase of freeze–thaw cycles would lead to decrease of cutting force. The decreases in Ca
2+- and K
+-ATPase activity and sulfhydryl group (
P
<
0.05) content with concomitant increases in carbonyl content and thiobarbituric acid-reactive substances (TBARS) value (
P
<
0.05) showed that multiple freeze–thaw could cause the porcine protein and fat oxidation, especially for the pork subjected to five freeze–thaw cycles. Gel electrophoresis patterns of porcine muscle showed that multiple freeze–thaw cycles could cause cross-linking of protein in myofibril. Overall, the freeze–thaw process has a detrimental effect on the quality of pork.
The inhibiting effect of ice structuring protein (ISP) with different additions on the quality deterioration and oxidation of mirror carp induced by freeze-thaw (F-T) cycles was investigated. It can ...be concluded that the whiteness, water holding capacity, cutting force and thermal stability of the sample without ISP were significantly decreased, and oxidation reactions were aggravated with the increasing in F-T cycles (P < 0.05). The centrifugal loss, thawing loss and cooking loss of 2.0 (g/L) ISP samples were decreased by 43.3%, 57.3% and 27.6% than the sample without ISP. In addition, ISP could effectively restrain moisture migration and destruction of microstructure of mirror carp during F-T cycles. More importantly, inhibitory effect of 2.0 ISP on oxidation was verified from the decrease in carbonyl contents (16.7%) and TBARS value (21.5%) of mirror carp compared with control.
•F-T cycles accelerated quality deterioration and oxidation of mirror carp.•ISP (ice structuring protein) inhibited the F-T damage of mirror carp quality.•Inhibiting effect of 2.0 (g/kg) ISP on quality decline of mirror carp was obvious.•ISP retarded the losses on microstructure of mirror carp during F-T cycles.
Display omitted
•Zein hydrolysates improve the emulsifying and oxidative stability of MP emulsions.•Emulsions with 5mg/mL ZH had a good ESI and low creaming index.•The interfacial membrane in ...emulsions with ZH was more compact and more massive.•The addition of ZH reduced the POV and TBARS of emulsions during storage.
This study investigated the effects of zein hydrolysate (ZH) on the improvement of the emulsifying and oxidative stability of oil-in-water (O/W) emulsions prepared by myofibrillar protein (MP). The emulsifying activity index (EAI) and emulsion stability index (ESI) increased with the increase of ZH concentrations. Emulsions with 5mg/mL ZH had the highest ESI and ζ-potential, the smallest mean particle size, and the lowest creaming index (p<0.05). Confocal laser scanning microscopy (CLSM) observation proved that emulsions with ZH possessed relatively small oil droplets, especially emulsions with 5mg/mL ZH, which were coincident with the results of droplet diameters and particle size distributions. The micrographs demonstrating the adsorption of ZH on the interfacial membrane of oil droplets in emulsions by CLSM also revealed that the interfacial membrane in emulsions with 5mg/mL ZH were more compact and more massive than that those without ZH. The addition of ZH significantly reduced the peroxide values and thiobarbituric acid-reactive substances values (p<0.05) of emulsions during 10days of storage. In general, our results revealed that the ZH promoted the adsorption of protein on the O/W interface and improved the emulsifying and oxidative stability of the MP O/W emulsion.
•Ultrasound-assisted saline thawing (UST) inhibited water mobility and redistribution of mirror carp.•The degree of lipid and protein oxidation of the samples was reduced by UST.•The mirror carp ...sample thawed with UST retained a relatively intact microstructure.•UST with 1% salt was the appropriate condition for thawing mirror carp.
The aim of the study was to evaluate the positive effect of ultrasound-assisted saline thawing (UST) on the technological properties (water mobility, water holding capacity, colour, pH, shear force, TVB-N, oxidation reaction and microstructure) of mirror carp (Cyprinus carpio L.). The results present in the study showed that different thawing methods had negative impacts on the quality of mirror carp to varying degrees. Among them, UST samples had significant lower thawing loss, centrifugal loss and cooking loss than ultrasound thawing (UT) and air thawing (AT) samples (P < 0.05). The analysis result of low-field nuclear magnetic resonance illustrated that UST inhibited the mobility and distribution of water effectively. Decrease in shear force and TVBN values were observed in all thawing samples, and the UST samples maintained the significant better texture property and freshness than UT and AT samples did (P < 0.05). In addition, the treatment of UST obtained 1% salt concentration inhibited the oxidation reactions effectively. Investigation of the microstructure of samples demonstrated that the treatment of UST kept the relatively complete structure of tissue than other thawing methods. Therefore, UST can be an alternative strategy to the traditional thawing of meat.
The effects of freeze–thaw cycles (FT, 0, 1, 3 and 5 times) on protein functional properties of porcine longissimus muscle were investigated. FT increased gapping between muscle fibres and tore ...muscle fiber bundles. Myofibrillar protein (MP) isolated from FT muscle showed an increased hydrophobicity (
P
<
0.05), reduced thermal transition temperatures (
T
max) and enthalpy of denaturation (Δ
H) (
P
<
0.05), and enhanced susceptibility to thermal aggregation. These structural changes resulted in major losses in protein functionalities, e.g., 41–43% reductions (
P
<
0.05) in MP emulsifying capacity and emulsion stability after five FT cycles. The ability of MP to form a viscoelastic gel network, as analyzed by small-strain oscillatory rheological testing, also attenuated with FT cycles. The FT process lowered (
P
<
0.05) water-holding capacity (WHC), whiteness, and texture (hardness, springiness, chewiness and cohesiveness) of MP gels. Overall, repeated FT had a detrimental effect on the general functionality of porcine MP, and protein denaturation and aggregation were implicated in the functionality losses.
Antioxidant activity and functional properties of porcine blood plasma protein hydrolysates (PPH) prepared with Alcalase at 6.2%, 12.7% and 17.6% of degree of hydrolysis (DH) were investigated. The ...PPH showed stronger radical-scavenging ability and possessed stronger Cu
2+-chelation ability and a reducing power compared to non-hydrolysed plasma protein (
P
<
0.05). The antioxidant activity of PPH, indicated by thiobarbituric acid-reactive substance (TBARS) values in a liposome-oxidising system, increased with increasing DH (
P
<
0.05). The Alcalase hydrolysis increased protein solubility from its original 68.46–81.79% (non-hydrolysed) to 82.95–94.94% (hydrolysed) over a broad pH range (3.0–8.0). However, hydrolysis decreased surface hydrophobicity and suppressed emulsifying and foaming capacity of the plasma protein. To identify antioxidant peptide, PPH was subjected to ultrafiltration, ion-exchange chromatography and reverse-phase high performance liquid chromatography (RP-HPLC), and the amino acid sequences of isolated peptides were determined by liquid chromatography/tendem mass spectrometry (LC–MS/MS). The peptide with the strongest antioxidant activity had the amino acid sequence of His-Asn-Gly-Asn. The results indicated that PPH could be used as a novel antioxidant but may be of limited utility as an emulsifying or foaming agent.
This experiment was conducted to assess the antioxidant efficacy of black currant (Ribes nigrum L.) extract (BCE) in raw pork patties during chilled storage. The extracting conditions of frozen BCE ...including ethanol concentrations (0–100%) and extracting times (0.25–12h) were studied. BCE extracted with 40% ethanol for 2h had the highest anthocyanin content, the strongest radical scavenging activities as well as the second strongest reducing power. BCE was condensed and added to pork patties at 5, 10 or 20g/kg. Compared with the control, BCE treatments significantly decreased the thiobarbituric acid-reactive substance values and carbonyls formation and reduced the sulfhydryl loss of pork patties in a dose-dependent manner (P<0.05), which showed that the BCE significantly inhibited lipid and protein oxidation. The BCE-treated patties showed significantly higher redness (P<0.05) than the control. The findings demonstrated strong potential for BCE as a natural antioxidant in meat and meat products.
Display omitted
•Temperature-controlled ultrasound (US) bath was created in our present study.•Meat batters with 50% phosphate reduction were sonicated before cooking.•25 min was the optimal US time ...to eliminate the defects caused by reduced phosphates.•US treatment did not enhance the lipid oxidation of reduced-phosphate frankfurters.•Except for time, constant low temperature control was another crucial factor.
The objective of this study was to evaluate the effect of ultrasound treatments with different durations (15, 20, 25, 30, and 35 min) at a low static temperature (12 °C) controlled by an intelligent temperature control and monitoring system on the quality of 50% reduced-phosphate frankfurters. The results show that without ultrasound treatment, phosphate reduction caused some obvious deficits in the textural properties, sensorial parameters, and oxidative stability of frankfurters. Moreover, 25-min ultrasound treatment could significantly lower the cooking loss and enhance emulsion stability, textural properties, and sensorial parameters of reduced phosphate frankfurters, which was also verified by dynamic water distribution analysis and microstructural observation. Additionally, low constant temperature during ultrasound treatment was another crucial factor in retarding lipid oxidation during storage. Therefore, ultrasound treatment with moderate duration and stable low temperature could be considered a successful approach to obtain healthier reduced-phosphate frankfurters under the “clean label” concept.
PDF