Changes in protein fractions of rainbow trout (Oncorhynchus mykiss) gravads during production and storage

Effect of three unsaturated fatty acids on the protein oxidation and structure of myofibrillar proteins from rainbow trout (Oncorhynchus mykiss)

In this study, the impact of three unsaturated fatty acids (Oleic acid: OA, Eicosapentaenoic acid: EPA, Docosahexaenoic acid: DHA) on the oxidation and structure of rainbow trout myofibrillar protein (MP) was explored. The findings revealed a notable increase in carbonyl content (P < 0.05) and a significant decrease in total sulfhydryl content (P < 0.05) of MP with the concentration increase of the three unsaturated fatty acids. Endogenous fluorescence spectroscopy and surface hydrophobicity analyses showed that unsaturated fatty acids can cause unfolding and exposure of hydrophobic groups in MP. In addition, SDS-PAGE showed that disulfide bonds were associated with MP cross-linking and aggregate size induced by unsaturated fatty acids. Overall, three unsaturated fatty acid treatments facilitated the oxidation of myofibrillar proteins, and the extent of protein oxidation was closely associated with the concentration of unsaturated fatty acids.

Biogenic amines as an indicator of rye leaven quality during production and storage

Rye leaven, the basic constituent of sour rye soup ('żurek' or white borsch), was obtained through three methods of initiating lacto-fermentation of rye flour. Optimal concentrations of NaCl (1.5%) and garlic (0.5%) were selected by utilizing the response surface methodology. During the production and storage of leaven at 10 °C and 20 °C, the secalin proteins of rye flour degraded significantly and the concentration of free amino acids increased, making the rye leaven an environment potentially conducive to the formation of biogenic amines. Putrescine (max. conc: 116.7 mg kg-1) and tyramine (max. conc: 63.4 mg kg-1) were the amines that occurred in the largest amounts in the leavens. The final concentration of histamine (after 150 days of storage) did not exceed 22 mg kg-1. Regardless of the method of initiation of fermentation, the products that contained fewer biogenic amines better retained their sensory characteristics (r ≤ -0.89, p < 0.05) and had a higher number of lactic acid bacteria (r ≤ -0.66, p < 0.05).

Use of mid-infrared spectroscopy for quality monitoring and the prediction of physicochemical parameters of dry fermented chicken sausages enriched with sesame flour

BACKGROUND

This study aimed to investigate the effects of the supplementation of sesame flour in fermented chicken sausages ('S1' containing 800 g kg^-1 chicken fillet, 180 g kg^-1 veal fat and 20 g kg^-1 sesame flour and 'S2' containing 800 g kg^-1 chicken fillet, 160 g kg^-1 veal fat and 40 g kg^-1 sesame flour) compared with control sausages (containing 800 g kg^-1 chicken fillet and 200 g kg^-1 veal fat) on the physico-chemical characteristics, texture, and structure during the fermentation stage.

RESULTS

The physicochemical parameters of samples belonging to the control, S1, and S2 batches were significantly affected by the addition of sesame flour and the fermentation stage. For instance: (i) the lowest protein content was observed for control samples on day 1 (61.4 ± 6.52 g kg^-1 ) whereas the highest level was noted for S2 samples on day 15 (327.5 ± 22.2 g kg^-1 ), and (ii) an inverse trend was observed for the fat content because the lowest content was observed for samples in the S2 batch on day 1 (129.0 ± 5.30 g kg^-1 ) whereas the highest fat content was noted for samples belonging to control batch on day 15 (332.0 ± 1.29 g kg^-1 ). The application of statistical methods to mid-infrared spectroscopy allowed clear discrimination between control, S1, and S2 batches. The addition of sesame flour in the recipes induced some modification in the secondary structure because β-turn levels ranged from 39.30 to 34.50, 36.76 to 34.70, and 38.93 to 34.70 for control, S1, and S2 batches, respectively, throughout the fermentation stage. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed a similar protein profile pattern in the three batches on days 1 and 5, but on day 10 control and S2 batches showed the most intense degradation of myofibrillar proteins.

CONCLUSION

The results demonstrated that mid-infrared spectroscopy coupled with chemometric tools could be used as a rapid screening tool to assess and monitor the quality of dry chicken sausages enriched with sesame flour throughout the fermentation stage. © 2022 Society of Chemical Industry.

Application of ultrasound-assisted cryoprotectant impregnation for improving the storage quality of snakehead fish fillets

In aquatic products companies, saccharides and phosphates are often used to impregnate products to improve their quality. Insignificant impregnation effect is a main problem met in the impregnation process. The effect of ultrasonic-assisted impregnation on the storage quality of snakehead fish fillets at -18°C was studied. For all samples, such parameters as water holding capacity, pH value, salt-soluble protein content, whiteness and cooking loss rate were examined periodically. Furthermore, the changes of moisture distribution and migration in snakehead fish fillets during storage were investigated using low-field nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). The results demonstrated that ultrasonic-assisted impregnation showed better anti-freeze and water holding capacity effects than that of cryoprotectant impregnation alone. Therefore, ultrasonic treatment could be used as an effective way to improve the quality of snakehead fish fillets during the frozen process. This study could provide a broad application prospect in aquatic product processing industry.

Effect of Storage Conditions on the Protein Composition and Structure of Peanuts

Peanuts are important oil crops and plant protein source. This study evaluated the influence of storage temperature (15, 25, and 35 °C) and time (0, 160, and 320 days) on the protein composition and the molecular structure of peanuts through sodium dodecyl sulfate polyacrylamide gel electrophoresis, particle size, total sulfhydryl (-SH) contents, nanostructural characterization, surface morphology microstructure, and spatial distribution of proteins and lipid analysis. Results showed that the basic subunits and disulfide contents of peanut protein were not affected by storage temperature and time. However, the -SH contents decreased significantly (P < 0.05) in all samples except the 15 °C/160 day storage group. The protein particle size and graininess increased when stored at 25 and 35 °C for 160 and 320 days, respectively; however, there was no significant change (P > 0.05) when stored at 15 °C. In addition, significant changes (P < 0.05) on the microscopic morphology and spatial distribution of protein and lipids were observed when stored at 25 and 35 °C for 320 days.

Nucleotide degradation, biogenic amine level and microbial contamination as quality indicators of cold-stored rainbow trout (Oncorhynchus mykiss) gravad

The extent to which the transformation of nucleotides, biogenic amines, and microbiological changes affect the quality and shelf life of vacuum packaged low processed rainbow trout (Oncorhynchus mykiss) gravad during storage at 7 ± 1 °C for 42 days was investigated. Although total viable counts increased slowly up to 6 log CFU g^-1 at the end of storage, coliform bacteria disappeared. The histamine concentration and the biogenic amine index increased up to 45.2 ± 1.62 mg kg^-1 and 100 mg kg^-1 respectively. The highest concentration of inosine monophosphate was achieved in freshly prepared gravad, whereas the hypoxanthine level increased with storage time up to 28 days. Among nucleotide ratios, the G value is more suitable for the determination of gravad quality than K, K_i and H values. Once the gravad obtained the limit of acceptability by the panelists (35 days) the G value rose to 470%.

Changes in properties of white shrimp (Litopenaeus vannamei) protein during thermal denaturation

Changes in white shrimp (Litopenaeus vannamei) protein during thermal denaturation were studied using Raman spectroscopy and isotopic H/D exchange. Denaturation of shrimp protein began after heating for 10 min at 50°C. A decrease in the percentage of α-helices accompanied by an increase in the percentage of β-sheets occurred while the total percentage of disordered structures increased. With extension of the exchange time, the relative intensity of the O-D bond increased, accompanied by a higher relative O-D bond intensity for heated shrimp, compared with unheated shrimp. H/D exchange revealed a higher rate of deuteration kinetics in heated shrimp than for unheated shrimp, especially during the first 2 h, consistent with water loss from denatured white shrimp protein. Physical property changes in muscle tissue can be caused by changes in hydrogen bonding and hydrophobicity during thermal processes.

Effect of ante-mortem hypoxia on the physicochemical and functional properties of white shrimp (Litopenaeus vannamei) muscle stored on ice

The effect of ante-mortem hypoxia on the physicochemical and functional properties of raw and cooked white shrimp was studied. Hue angle was greater ( p ≤ 0.05) for stressed raw shrimp compared to control (greener color); whereas a lower angle was detected for cooked stressed shrimp (redder/orange coloration). In addition, hue angle increased ( p ≤ 0.05) over the ice storage period for control and stressed shrimp (raw and/or cooked). Muscle hardness and shear force showed no differences when comparing control and stressed shrimp (raw and/or cooked). However, during ice storage, shear force increased ( p ≤ 0.05) by 22% and 9% for control and stressed raw shrimp, respectively; in contrast, shear force and muscle hardness decreased for cooked shrimp ( p ≤ 0.05). Control showed more ( p ≤ 0.05) elasticity than stressed cooked shrimp. Stressed raw shrimp showed a water holding capacity 10.8% lower ( p ≤ 0.05) than control. However, during the storage, water holding capacity increased ( p ≤ 0.05) reaching similar values to control after day 4. Muscle protein solubility of stressed shrimp was 31% lower than control; however, no differences ( p > 0.05) were observed after the second day. The thermal stability of myosin ( Tmax) showed differences ( p ≤ 0.05) among control and stressed shrimp, whereas no differences for Δ H were observed. Results showed the influence of ante-mortem hypoxia on the physicochemical and functional properties of white shrimp muscle.