Characterization of lipid oxidation process of beef during repeated freeze-thaw by electron spin resonance technology and Raman spectroscopy

Prediction of Warner-Bratzler shear force, intramuscular fat, drip-loss and cook-loss in beef via Raman spectroscopy and chemometrics

Rapid prediction of beef quality remains a challenge for meat processors. This study evaluated the potential of Raman spectroscopy followed by chemometrics for prediction of Warner-Bratzler shear force (WBSF), intramuscular fat (IMF), ultimate pH, drip-loss and cook-loss. PLS regression models were developed based on spectra recorded on frozen-thawed day 2 longissimus thoracis et lumborum muscle and validated using test sets randomly selected 3 times. With the exception of ultimate pH, models presented notable performance in calibration (R² ranging from 0.5 to 0.9; low RMSEC) and, despite variability in the results, promising predictive ability: WBSF (RMSEP ranging from 4.6 to 9 N), IMF (RMSEP ranging from 0.9 to 1.1%), drip-loss (RMSEP ranging from 1 to 1.3%) and cook-loss (RMSEP ranging from 1.5 to 2.9%). Furthermore, the loading values indicated that the physicochemical variation of the meat influenced the models. Overall, results indicated that Raman spectroscopy is a promising technique for routine quality assessments of IMF and drip-loss, which, with further development and improvement of its accuracy could become a reliable tool for the beef industry.

Interrelationship between myoglobin oxidation and lipid oxidation during the processing of Cantonese sausage with d-sodium erythorbate

BACKGROUND

Pork is used as raw material to produce Cantonese sausage, and 0.5 or 1 g kg^-1 of d-sodium erythorbate is added to the pork meat. In this study the myoglobin oxidation rate, relative metmyoglobin content, heme iron content, redness, pH, free radical content and thiobarbituric acid reactive substance (TBARS) value were measured at different processing times and different content of d-sodium erythorbate.

RESULTS

It was found that d-sodium erythorbate significantly reduced the free radical content and myoglobin and lipid oxidation rates and increased heme iron levels. When d-sodium erythorbate was added to the sausage, the absorption peak of myoglobin porphyrin shifted left, migrating from 414 to 405 nm. At 72 h, with an increase in the d-sodium erythorbate content, a significant negative correlation was identified between heme iron and the degree of redness (P < 0.01).

CONCLUSION

During sausage processing, there are strong correlations among TBARS values, free radical content, metmyoglobin levels, heme iron levels, a* and pH at the same d-sodium erythorbate level. At the same processing time, adding d-sodium erythorbate can slow the rate of myoglobin and lipid oxidation and prevent the discoloration of sausage. © 2019 Society of Chemical Industry.

Evaluation on the oxidative stability of edible oil by electron spin resonance spectroscopy

Evaluation on the oxidative stability of oils, based on the tendency of free radicals production, can be operated by using electron spin resonance (ESR) spectroscopy. Induction Periods (IP) can be determined by Boltzmann equation fitting under accelerated conditions (heated). The IPs were compared with IPs of Rancimat method, and high linear correlation was found between these two methods (r = 0.996 and 0.985 separately), suggesting that ESR method can predict the oxidative stabilities provided by the Rancimatt method. This study indicated that ESR provided a sensitive method to evaluate the oxidative stability of edible oils.

The Role of an Acidic Peptide in Controlling the Oxidation Process of Walnut Oil

Here, the mechanism of action of an antioxidant peptide rich in acidic amino acid residues in controlling lipid oxidation is discussed. Firstly, in the presence of this peptide, the fluorescence intensity of lipid peroxide in samples of walnut oil was very low, indicating that the peptide prevented the formation of lipid peroxides. Secondly, the production of lipid-derived radicals of oil was reduced by 23% following addition of the anti-oxidative peptide. Thirdly, Raman shifts of the lipid with the anti-oxidative peptide showed that acidic amino acid residues of the peptide were involved in delaying lipid oxidation. Finally, seven peptide inhibitors were synthesized with variations to the amino acid sequence of the original peptide, and Glu-Asp was proven to enhance the peptide's superoxide anion radical scavenging activity and decrease the formation of linoleic acid peroxides. Our findings emphasize the potential value of acidic amino acid residues in protecting unsaturated fatty acids from oxidation.

Production of thymol nanoemulsions stabilized using Quillaja Saponin as a biosurfactant: Antioxidant activity enhancement

Thymol oil-in-water nanoemulsions as a potential natural alternative for synthetic antioxidant agents were developed. The nanoemulsions were formulated using Quillaja Saponin bio-surfactant and green solvents including high oleic sunflower oil (HOSO), tricaprylin (TC), and cinnamaldehyde (CA). The 4% thymol nanoemulsions containing TC and HOSO remained stable during long-term storage (at least 30 d). The antioxidant activity (AA) of free thymol and thymol nanoemulsions was compared with butylated hydroxytoluene (BHT) and ascorbic acid. The results obtained from DPPH, FRAP, and CUPRAC antioxidant assays showed a substantial improvement (p < 0.05) of the AA of free thymol through emulsification. The outcomes from the AA of the nanoemulsions in raw chicken breast meat measured by the TBARS assay revealed a significant improvement (p < 0.05) of the AA when thymol was encapsulated. These nanoemulsions may be applicable in the food industry as well as in cosmetic and health care products.

Irregular pacing of ventricular cardiomyocytes induces pro-fibrotic signalling involving paracrine effects of transforming growth factor beta and connective tissue growth factor

AIMS

Atrial fibrillation is the most prevalent sustained arrhythmia associated with arrhythmic ventricular contractions, incident heart failure, increased morbidity and mortality. The relationship between arrhythmic contractions and ventricular remodelling is incompletely understood. The aim of this study was to characterize the influence of irregular contractions on pro-fibrotic signalling in neonatal rat ventricular cardiomyocytes (NRVM).

METHODS AND RESULTS

Neonatal rat ventricular cardiomyocytes were paced via field stimulation at 3 Hz for 24 h. Irregularity was created by pseudorandomized variation of stimulation intervals and compared to regular pacing. Treatment of neonatal cardiac fibroblasts (NCF) with medium of irregularly paced NRVM increased protein expression of collagen I (206 ± 62%, P = 0.0121) and collagen III (51 ± 37%, P = 0.0119). To identify the underlying mechanism, expression of pro-fibrotic connective tissue growth factor (CTGF) and transforming growth factor beta (TGF-β) was assessed. In irregularly paced NRVM, increased protein expression of CTGF (80 ± 22%, P = 0.0035) and TGF-β (122 ± 31%, P = 0.0022) was associated with enhanced excretion of both proteins into the medium. Electron paramagnetic resonance spectroscopy revealed an increased production of reactive oxygen species (46 ± 21%, P = 0.0352) after irregular pacing accompanied by increased 8-hydroxydeoxyguanosine staining (214 ± 53%, P = 0.0011). Irregular pacing was associated with elevated mRNA levels of anti-oxidative superoxide dismutase 1 (25 ± 7%, P = 0.0175), superoxide dismutase 3 (20 ± 7%, P = 0.0309), and catalase (20 ± 7%, P = 0.046).

CONCLUSION

These data demonstrate that irregular pacing is an important inductor of pro-fibrotic signalling in NRVM involving paracrine effects of CTGF and TGF-β as well as increased oxidative stress. Thus, irregularity of the heart beat might directly be involved in the progression of maladaptive remodelling processes in atrial fibrillation.