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.     

Effects of sesamol, sesamin, and sesamolin extracted from roasted sesame oil on the thermal oxidation of methyl linoleate

This study investigated the effects of lignan compounds extracted from roasted sesame oil, which were sesamol, sesamin, and sesamolin, on oxidation of methyl linoleate (ML) during heating. These compounds were added at 500 or 1000 mg/kg to ML, and α-tocopherol was used as a reference antioxidant. The ML added with lignans or α-tocopherol was heated at 180 °C for 60 min. Thermal oxidation of ML was evaluated by conjugated dienoic acid (CDA) contents, p-anisidine value (PAV), and ML retention. Contents changes of lignan compounds or α-tocopherol in ML during heating were monitored by high-performance liquid chromatography. CDA contents and PAV of samples increased and ML decreased with heating time at 180 °C. Samples added with lignan compounds showed lower CDA contents and PAV but higher ML retention than samples without lignan compounds. The antioxidant activity of sesame oil lignan compounds in ML oxidation during heating tended to be higher than that of α-tocopherol. The contents of lignan compounds in samples decreased with heating time due to their degradation, but the degradation rates were lower than that of α-tocopherol. This study suggested that sesame oil lignan compounds be used as antioxidants in oil at high temperatures for deep-fat frying due to their higher effectiveness and stability than α-tocopherol.     

Direct determination of phenolic compounds and phospholipids in virgin olive oil by micellar liquid chromatography

A simple HPLC method is reported for fast separation and determination of phenolic compounds (tyrosol, caffeic acid, p-coumaric acid and oleuropeina) and phospholipids (phosphatidylethanolamine and phosphatidylcholine) in virgin olive oil samples. The samples were diluted with 2-propanol and injected into the column directly without previous extraction. Samples with an olive oil content of up to 65% were injected without any problems. The analytes were separated on a C-18 column by a micellar mobile phase containing 0.07 M SDS and 2.5% 2-propanol at pH 3, and were detected at 210 nm. Linear calibration curves [r² > 0.997] were obtained with detection limits ranging from 0.052 to 0.16 μg/g and 1 to 8.6% repeatability for the phenolic compounds. Several virgin olive oil samples were analysed and the recovery values were around 110%.     

Antioxidant activity and phenolic content of 16 raisin grape (Vitis vinifera L.) cultivars and selections

Six raisin grape cultivars and 10 new raisin grape selections were analyzed for antioxidant activity (ABTS assay) and for total and individual phenolic compounds. Samples were freeze–dried and values are reported on a dry weight basis. Antioxidant activity across the 16 samples ranged from 7.7 to 60.9 μmol Trolox/g DW, with A95-27 exhibiting the greatest activity. Total phenolic content, determined in gallic acid equivalents using the Folin–Ciocalteau assay, ranged from 316.3 to 1141.3 mg gallic acid/100 g DW and was strongly correlated (r = 0.990) with antioxidant results. Concentrations of individual phenolics were determined by HPLC. trans-Caftaric acid was the predominant compound in all samples. A95-15 contained the lowest concentration (153.5 μg/g DW) of caftaric acid, while Fiesta contained the highest concentration (598.7 μg/g DW). Selections A56-66, A95-15, and A95-27 had much higher levels of catechin (86.5–209.1 μg/g DW) and epicatechin (126.5–365.7 μg/g DW) than the other samples.     

Shelf-life extension of crucian carp (Carassius auratus) using natural preservatives during chilled storage

The effect of the natural preservatives, tea polyphenols and rosemary extract, on microbiological [total viable count (TVC)], chemical [pH, total volatile base nitrogen (TVB-N), K-value and thiobarbituric acid (TBA) values], texture and sensory changes of air-packaged whole crucian carp (Carassius auratus) stored at 4 ± 1 °C was investigated for 20 days. The shelf-life of crucian carp was found to be 7–8 days for untreated group (control), 13–14 days for tea polyphenols group and 15–16 days for rosemary extract treated group according to sensory assessment results, for which the corresponding microbiological assessment also showed an increased shelf-life. Meanwhile, the increases of pH, TVB-N, K-value and TBA values were significantly delayed in both treated groups of samples compared to the control group. Thus, either tea polyphenols or rosemary extract could be used as potential preservatives to extend the shelf-life of crucian carp during chilled storage.     

Effect of drying method on the antioxidant capacity of six Lamiaceae herbs

The present study investigated the changes in total phenols (TP), rosmarinic acid content and antioxidant capacity of six Lamiaceae herbs (rosemary, oregano, marjoram, sage, basil and thyme) after three drying treatments (air-, freeze- and vacuum oven-drying) stored for 60 days at −20 °C and compared to fresh samples. Ferric reducing antioxidant property (FRAP) and oxygen radical absorbance capacity (ORAC) were used as markers for antioxidant capacity. Air-dried samples had significantly (p < 0.05) higher TP, rosmarinic acid content and antioxidant capacity than had freeze-dried and vacuum oven-dried samples throughout the storage period. Fresh samples had the lowest values for the parameters tested. Vacuum oven-drying resulted in higher TP and FRAP values in rosemary and thyme during 60 days of storage than did freeze-drying. In ORAC assay, the difference was significantly higher only in thyme. Storage did not show any effect on the dried samples for the parameters tested.     

Effect of bleeding on lipid oxidation and quality changes of Asian seabass (Lates calcarifer) muscle during iced storage

Lipid oxidation, microbial load and fishy odour development in the slices of bled and un-bled Asian seabass during 15 days of iced storage were comparatively investigated. Bled samples showed the lower peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS) throughout the storage period (P < 0.05). Bleeding effectively lowered the total haem and non-haem iron contents in Asian seabass slices. The release of non-haem iron was pronounced in the un-bled samples during the storage. Solid phase micro-extraction coupled with gas chromatography and mass spectrometric (SPME-GCMS) analysis revealed that the bled samples stored in ice for 15 days contained the lower amount of volatile compounds. Heptanal, the major volatile compound detected in the un-bled samples, was four-fold higher than that of bled counterparts. The contents of aldehydic compounds, including hexanal, octanal, nonanal and nonenal were also higher in the former. Bled samples had the lower fishy odour, compared with the un-bled counterparts during storage (P < 0.05). The lower total viable counts (TVC) and psychrophilic bacterial counts (PBC) were observed in the bled samples, in comparison with the un-bled ones (P < 0.05). Thus, bleeding was a potential means in retarding lipid oxidation, fishy odour development, and microbial growth of Asian seabass slices during storage in ice.     

Composition of rosemary essential oil (Rosmarinus officinalis) as affected by drying method

The influence of the drying method on volatile compounds of Rosmarinus officinalis was evaluated. The drying methods tested were convective (CD) and vacuum-microwave (VMD), as well as a combination of convective pre-drying and VM finish-drying (CPD–VMFD). Rosemary drying kinetics was described by a simple exponential model for CD and VMD, while VMFD kinetics consisted of two periods: linear until a critical point and exponential beyond that point. Volatile compounds of rosemary samples were extracted by steam-hydrodistillation and analyzed by GC–MS. Thirty-four compounds were tentatively identified, with α-pinene, bornyl acetate, camphene and 1,8-cineole being the major components. The total volatiles concentration of fresh rosemary (135 g kg⁻¹) decreased considerably during both CD (87.2 g kg⁻¹) and VMD (61.9 g kg⁻¹). CPD–VMFD was the best option for drying rosemary because the time required was relatively short (30 min), and the aroma quality was good according to both instrumental (100 g kg⁻¹) and sensory analyses.     

Retardation of haemoglobin-mediated lipid oxidation of Asian sea bass muscle by tannic acid during iced storage

Lipid oxidation mediated by haemoglobin from tilapia was monitored in washed Asian sea bass mince with and without added tannic acid (200 and 400 ppm) during 10 days of iced storage. Control samples (without tannic acid) had the highest peroxide value (PV) within the first 2 days and possessed the greater amount of thiobarbituric acid-reactive substances (TBARS) throughout the storage of 10 days (p < 0.05). With addition of tannic acid, the lipid oxidation of washed Asian sea bass mince was retarded, especially when the higher level (400 ppm) was used, as evidenced by lowered PV and TBARS. The retarded formation of volatile lipid oxidation products in the samples with added 400 ppm tannic acid was found. Sensory analysis revealed that samples with added 400 ppm tannic acid possessed lower fishy odour score, compared with the control sample and that with added 200 ppm tannic acid (p < 0.05).     

Retardation of myoglobin and haemoglobin-mediated lipid oxidation in washed bighead carp by phenolic compounds

Antioxidative activities of phenolic compounds (caffeic acid, gallic acid and tannic acid; 200 ppm) in washed mince (pH 6), with added myoglobin (Mb) and haemoglobin (Hb), from bighead carp (Hypophthalmichthys nobilis), during 9 days of iced storage, were studied. Tannic acid exhibited the preventive effect on discolouration of washed mince containing Mb or Hb during storage (P < 0.05). High peroxide value (PV) was found and large amount of, thiobarbituric acid-reactive substances (TBARS) and hexanal were formed in washed mince containing haem proteins, especially Hb. As determined by apo Streptococcal haem-associated protein, Hb had the lower haem affinity than Mb. Phenolic compounds, especially caffeic acid and gallic acid, could lower lipid oxidation induced by Mb or Hb throughout storage (P < 0.05). Prevention of haem release, as well as inhibition of lipid oxidation induced by haem proteins with selected phenolic compounds, should be an alternative means in lowering discolouration and lipid oxidation in fish muscle.     

Effects of vacuum level and microwave power on rosemary volatile composition during vacuum-microwave drying

The influence of the vacuum level and the microwave power on aroma compounds and sensory quality of Rosmarinus officinalis dehydrated by vacuum-microwave (VM) method was evaluated. VM drying kinetics consisted of two periods: linear until a critical point and exponential beyond that point. The time needed to dry rosemary was shorter for high values of microwave power and vacuum intensity. Volatile compounds of rosemary samples were extracted by steam-hydrodistillation and analyzed by GC-MS. Thirty-one compounds were identified, with α-pinene, verbenone and 1,8-cineole being the major components; monoterpenoids were the predominant chemical family. The total quantity of volatiles of fresh rosemary (27.2 g kg⁻¹) decreased during drying, independently of treatments, to a mean of 14.8 g kg⁻¹. Soft conditions of VM drying (low vacuum level and microwave power) are recommended to get the highest concentrations of volatiles and the best sensory quality (e.g. 72-74 kPa and 360 W).     

Changes in strawberry phenolics, anthocyanins, and antioxidant capacity in response to high oxygen treatments

Changes in fruit quality, decay, phenolic and anthocyanin content, and antioxidant capacity of strawberries (Fragaria × ananassa Duch. cv. Allstar) stored under air and high oxygen atmospheres at 5 °C were investigated. Freshly harvested strawberries were placed in jars and ventilated continuously with air or with 40, 60, 80, or 100 kPa O₂ at 5 °C for up to 14 days. Samples were taken initially, and after 3, 7, 10 and 14 days of storage. While fruit quality parameters such as titratable acidity, total soluble solids and surface color were only slightly affected by differing levels of O₂, the higher oxygen concentration treatments significantly reduced decay. Oxygen concentrations higher than 60 kPa also promoted increases in ORAC values, total phenolics and total anthocyanins as well as individual phenolic compounds analysed by HPLC during the initial 7 days of storage. However, this effect diminished with prolonged storage. No significant differences in ORAC values, total phenolics, total anthocyanins, or the individual phenolic compounds were observed among the high O₂ and air-stored fruits after 14 days of storage. These results indicate that high oxygen treatments exert the most effects on fruit quality and antioxidant capacity of strawberry fruit in the first 7 days of storage.     

Relationship between the solubility,dosage and antioxidant capacity of carnosic acid in raw and cooked ground buffalo meat patties and chicken patties

Antioxidant capacity of oil soluble and water dispersible carnosic acid (CA) extracted from dried rosemary leaves using HPLC was evaluated at two different dosages (22.5 ppm vs 130 ppm) in raw and cooked ground buffalo meat patties and chicken patties. Irrespective of total phenolic content, CA extracts reduced (p < 0.05) the thiobarbituric acid reactive substances (TBARS) by 39%–47% and 37%–40% in cooked buffalo meat and chicken patties at lower dosage (22.5 ppm) relative to control samples. However, at higher dosage (130 ppm) the TBARS values were reduced (p < 0.05) by 86%–96% and 78%–87% in cooked buffalo meat and chicken patties compared to controls. The CA extracts were also effective in inhibiting (p < 0.05) peroxide value and free fatty acids in cooked buffalo meat and chicken patties. The CA extracts when used at higher dosage, were also effective in stabilizing raw buffalo meat color.     

Osmotic dehydrofreezing of strawberries: Polyphenolic content, volatile profile and consumer acceptance

We evaluated dehydrofreezing in strawberries in terms of retention of healthy compounds (i.e. polyphenolics) and sensory qualities for direct consumption in substitution of fresh fruit. Different osmodehydration (OD at 30 °C and 5 °C), vacuum osmodehydration (VOD at 30 °C) and immersion chilling freezing (ICF) processes were applied in sucrose syrup. Samples were analyzed for dry matter, soluble solids, pH, titratable acidity, mass transfers, polyphenolic content by HPLC-DAD/MSD, volatile profile by SPME-GC/MSD and consumer acceptance. The results of sensory evaluation, in particular, confirmed the cryoprotective effects of osmotic processes of fruits with respect to untreated frozen control samples. The OD samples at 5 °C presented a water loss to solid gain ratio comparable to OD at 30 °C and VOD samples. Moreover, while osmo-dehydrofreezing at relatively high temperatures caused a slight depletion of phenolic compounds, the samples osmodehydrated at 5 °C showed higher polyphenolic retention. Data on aromatic compounds showed that some compounds increased (e.g. ethanol and acetaldehyde), while others did not appear to be affected by the pre-treatments.     

Effect of tannic acid and kiam wood extract on lipid oxidation and textural properties of fish emulsion sausages during refrigerated storage

Effect of tannic acid (0.02% and 0.04%) and ethanolic kiam wood extract (EKWE) (0.04% and 0.08%) on lipid oxidation and textural properties of fish emulsion sausages during 20 days of refrigerated storage was investigated. Control samples (C) had the highest peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS) value up to day 16 and 8 of storage, respectively. With the addition of tannic acid and EKWE, PV and TBARS values in the sausages were retarded effectively, compared to the control (P < 0.05), especially when the tannic acid and EKWE at higher level were used. At the same level, EKWE showed the lower ability in retarding the lipid oxidation, in comparison with tannic acid. Tannic acid at both levels (0.02% and 0.04%) was also effective in retarding the formation of fishy odour in the samples throughout the storage, compared to the control and EKWE treated samples (P < 0.05). Both tannic acid and EKWE had no detrimental effect on the sensory attributes of sausages. However, EKWE treated sample had lower L^∗ and higher a^∗ and ΔE^∗ values, compared to the control samples (P < 0.05). After 20 days of storage, the sample added with 0.04% tannic acid had higher hardness, gumminess and chewiness, compared with others (P < 0.05). Samples added with 0.04% tannic acid also displayed more compact structure with no visible voids. Furthermore, oil droplets with smaller size were dispersed more uniformly, compared to others. Thus, tannic acid (0.02% and 0.04%) and EKWE (0.08%) were effective in retarding lipid oxidation and fishy odour development as well as could maintain the textural properties of fish emulsion sausages during the refrigerated storage of 20 days.     

β-Sitosterol and campesterol stabilisation by natural and synthetic antioxidants during heating

The aim of this study was to estimate the effect of natural and synthetic antioxidants in protecting phytosterols during heating at 180 °C. Green tea extract, rosemary extract, a mix of tocopherols from rapeseed oil, a mix of synthetic tocopherols, phenolic compounds extracted from rapeseed meal, sinapic acid and BHT were used. After 4 h of heating in oxygen atmosphere β-sitosterol and campesterol oxidation products (7α- and 7β-hydroxysterol, 5α,6α- and 5β,6β-epoxysterol, 7-ketosterol and triols) were estimated by GC. Total content of phytosterol oxidation products in samples ranged from 137 to 374 mg/kg of sample. The effectiveness of antioxidants decreased in the following order: synthetic tocopherols > green tea extract > natural tocopherols from rapeseed oil > rosemary extract > phenolic compounds extracted from rapeseed meal > sinapic acid > BHT.     

Physico-chemical, textural and structural characteristics of sous-vide cooked pork cheeks as affected by vacuum, cooking temperature, and cooking time

This paper describes the influence of different factors on sous-vide cooked pork. Pork cheeks were cooked at different combinations of temperature (60 °C or 80 °C), time (5 or 12 h) and vacuum (vacuum or air packaged). Weight losses were lower and moisture content higher in samples cooked for a shorter time (P = 0.054) and at a lower temperature (P < 0.001). Samples cooked at 60 °C showed more lightness (L*) and redness (a*) (P < 0.001). Lipid oxidation showed an interaction between cooking time and temperature (P = 0.007), with higher TBARs values for samples cooked for 12 h at 60 °C and lower for those cooked for 12 h at 80 °C. Samples cooked at 80 °C for 12 h showed lower (P < 0.05) values for most textural parameters than all the other types of samples. Vacuum packaging showed no influence on any of the studied variables. For the treatments evaluated, cooking temperature × time combination seems to be more important than vacuum packaging in the textural and colour parameters of pork cheeks.     

Enhancement of gel strength of bigeye snapper (Priacanthus tayenus) surimi using oxidised phenolic compounds

Effects of different oxidised phenolic compounds (ferulic acid, OFA; tannic acid, OTA; catechin, OCT and caffeic acid, OCF) at different levels (0–0.25% of protein content) on the properties of gels from bigeye snapper (Priacanthus tayenus) surimi were investigated. Breaking force and deformation of surimi gel varied with types and amounts of oxidised phenolic compounds. Gels added with 0.20% OFA, 0.05% OTA, 0.15% OCF and 0.05% OCT exhibited the marked increases in both breaking force and deformation, compared with the control (P < 0.05). Those increases were associated with lower expressible moisture content. No increases in both breaking force and deformation were observed when ferulic acid without oxygenation at alkaline pH was added, regardless of amount added (P > 0.05). No changes in the whiteness of gel were found with addition of OFA (P > 0.05), but the decreases in whiteness were noticeable as other oxidised phenolics were incorporated (P < 0.05). Different microstructures were obtained among gels with different oxidised phenolics. The physicochemical properties of natural actomyosin suggest that oxidised phenolics could induce conformational changes and the cross-linking through amino groups or the induction of disulphide bond formation. Therefore, the addition of oxidised phenolic compounds at the optimum level could increase the gel strength of surimi gel.     

Biogenic and volatile amine-related qualities of three popular fish species sold at Kuwait fish markets

Three fish species commonly consumed in Kuwait were studied for their total volatile base nitrogen (TVBN) and biogenic amine composition during normal commercial activities at the fish markets. Samples of the fish species Zubaidi or silver pomfret (Pampus argenteus), Hammour or orange–spotted grouper (Epinephelus coioides), and Negrule or grunt (Pomadasys kaakan) were analyzed using steam distillation and high performance liquid chromatography (HPLC) procedures. Fish samples collected in the morning had lower levels of TVBN, ranging from 25.9 mg/100 g to 30.2 mg/100 g compared with the range of 31.2 mg/100 g to 40.9 mg/100 g for samples collected in the evening. Among all three fish species, Zubaidi (Pampus argenteus) showed the lowest TVBN content while Negrule (Pomadasys kaakan) had the highest. Biogenic amine levels were also low in the fish species. The data suggest that fish handling practices at the fish markets in Kuwait do not result in significant abuse of fish temperatures, and that the amounts of volatile and biogenic amines produced during normal activities did not rise to levels indicating fish decomposition.