Effect of Skin Wine Pomace and Sulfite on Protein Oxidation in Beef Patties During High Oxygen Atmosphere Storage

Meat storage in high oxygen atmosphere has been reported to induce protein oxidation reactions decreasing meat quality. The incorporation of antioxidants has been proposed to reduce the extent of these reactions. In this study, the ability of red and white skin wine pomaces as well as sulfites to inhibit protein oxidation were tested in beef patties stored for up to 15 days at 4 °C in a high oxygen atmosphere (70 % O₂ and 30 % CO₂). SO₂ (300 ppm) effectively protected against protein oxidation measured as radical formation by electron spin resonance (ESR) spectroscopy, as thiol loss by the DTNB assay and as myosin heavy chain (MHC) disulfide cross-linking by SDS-PAGE. Pomace from red wine production with a total phenol of 9.9 mg gallic acid equivalent/g protected against protein radical formation and against MHC cross-linking, but not against thiol loss by addition of 2.0 % (w/w) to the beef patties. Pomace from white wine production with a total phenol of 4.0 mg gallic acid equivalent/g only protected against MHC cross-linking. For both types of wine pomace, protein modifications not seen for sulfite addition were observed and were proposed to involve covalent phenol addition to proteins. Red wine pomace may be an alternative to sulfite as a meat additive for protection of beef patties against protein oxidation.     

Effect of green tea or rosemary extract on protein oxidation in Bologna type sausages prepared from oxidatively stressed pork

Bologna type sausages were prepared from oxidatively stressed pork (UV-irradiation, 48 h, 5 °C) using a traditional recipe (control) or the same recipe but added green tea extract (500 ppm total phenolic compounds) or rosemary extract (400 ppm total phenolic compounds). Green tea and rosemary extracts protected against formation of TBARS and protein carbonyls. On the contrary, increased thiol loss and a distinct loss of myosin heavy chain and actin due to polymerization by reducible bonds as determined by SDS-page were found by addition of green tea extract. The enhanced protein polymerization was ascribed to the reaction between quinone compounds from the plant extracts and protein thiol groups to yield phenol-mediated protein polymerization. Analysis by ESR spectroscopy revealed increased radical intensities in sausages added plant extracts, which was ascribed to originate from protein-bound phenoxyl radicals, which may protect against other oxidatively induced protein modifications.     

Dietary citrus pulp improves protein stability in lamb meat stored under aerobic conditions

The antioxidant effects of dried citrus pulp on proteins in lamb meat, when used as a replacement of concentrate in the feed, was studied using meat from 26 male Comisana lambs. The lambs of age 90 days had been grouped randomly to receive one of the three dietary treatments: (1) commercial concentrate with 60% barley (Control, n = 8), (2) concentrate with 35% barley and 24% citrus pulp (Cp24, n = 9), or (3) concentrate with 23% barley and 35% citrus pulp (Cp35, n = 9). Slices from the longissimus thoracis et lomborum muscle were packed aerobically and stored for up to 6 days at 4°C in the dark. The citrus pulp groups, Cp24 and Cp35, significantly decreased protein radicals and carbonyls, and preserved more thiols within six days of storage compared to the Control group. The citrus pulp groups significantly slowed down the rate of protein oxidation, indicating that dietary citrus pulp reduced oxidative changes in meat proteins.     

Thiol oxidation and protein cross-link formation during chill storage of pork patties added essential oil of oregano,rosemary, or garlic

The effect of two levels (0.05% and 0.4%) of essential oil of rosemary, oregano, or garlic on protein oxidation in pork patties was studied during storage under modified atmosphere (MAP: 70% O₂: 20% CO₂: 10% N₂) or under aerobic conditions (AE) at 4 °C. The oxidative stability of the meat proteins was evaluated as loss of thiols for up to 9 days of storage, and as formation of myosin cross-links analyzed by SDS-PAGE after 12 days of storage. Protein thiols were lost during storage to yield myosin disulfide cross-links. Essential oils of rosemary and oregano were found to retard the loss of thiols otherwise resulting in myosin cross-links. Garlic essential oil, on the contrary, was found to promote protein oxidation, as seen by an extreme loss in thiol groups, and elevated myosin cross-link formation compared to control.     

Effect of white grape extract and modified atmosphere packaging on lipid and protein oxidation in chill stored beef patties

The oxidative stability of beef patties added 500 ppm white grape extract (WGE), packed in four different modified atmospheres (MAP) with varying oxygen and carbon dioxide levels (70% or 0% O₂, 30% or 0% CO₂, balanced with N₂ in all four combinations) and stored for up to 9 days (4 °C) was evaluated by a sensory panel, formation of TBARS, formation of protein carbonyl, appearance of myosin cross-links, and thiol loss. Formation of secondary lipid oxidation products, as detected by TBARS, and the rancidity, as perceived by sensory analysis, were inhibited in WGE beef patties independent of MAP compared to control beef patties. The protein carbonyl formation was also reduced in WGE beef patties, but no significant effects were observed in relation to different MAP. Loss of thiol groups in control beef patties was consistent with the formation of myosin cross-linkages. In the presence of WGE, thiol groups decreased faster but showed less myosin cross-link formation compared to control beef patties, indicating that WGE interacts with the thiol groups of the myofibrillar proteins, and thus reduces the cross-link formation in beef patties stored in high-oxygen MA.     

Characterisation of protein-polyphenol interactions in beer during forced aging

Proteins and proteinaceous material were extracted by acetone precipitation of beer that had undergone forced aging through 0 (control), 5 (medium) or 10 (high) heat/chill cycles (60°C 48h/0°C 24h). Size exclusion chromatography analysis of the crude beer extract showed that forced ageing led to a significant increase in binding of phenolic compounds to Protein Z and especially to lipid transfer protein 1 (LTP1). Protein-polyphenol conjugates were also present in high molecular weight (> 100 kDa) and low molecular weight fractions (< 5 kDa), but these conjugates were already present in the fresh beer and were not affected by the forced aging. Treatment of the crude beer extract with sulphite (2 M) dissociated the protein-polyphenol bindings in LTP1 and Protein Z that had been generated during medium forced aging. Identification and quantification of the free, the non-covalently, and the covalently bound phenolic compounds were performed by UHPLC after extraction by methanol, acetic acid, and sulphite, respectively. The amounts of vanillic acid and caffeic acid decreased in the free polyphenol fraction, indicating binding to proteins during forced aging. Epicatechin and quercetin-3-O-glucoside were found to be non-covalently bound during forced aging. Finally, gallic acid, epicatechin, protocatechuic acid, and astragalin were found to be covalently bound already in the fresh beer. © 2020 The Institute of Brewing & Distilling     

Elimination of matrix interferences in biosensor analysis of streptomycin in honey

Analysis of honey for the antibiotic streptomycin, which is not approved for use in apiculture within the European Union, by immunochemical biosensor screening was found to be disturbed by matrix influence related to the color of the honeys, as also known from enzyme-immunoassays. Effect of interfering compounds most likely being glycosides was eliminated by meticulous pH-control followed by ultrafiltration of the dissolved honey samples prior to analysis resulting in a rapid and simple analytical method with a detection limit <10 μg/kg.