Assessment of the antioxidant potential of selected plant extracts – In vitro and in vivo experiments on pork

The antioxidant potential of selected plant extracts was assessed in vitro and in vivo experiments on pork. In the in vitro experiment, the anti-oxidative capacity of ethanol–water extract of Melissa officinalis (MW), ethanol–propylene–glycol extracts of M. officinalis (MP), Origanum vulgaris (O) and Salvia officinalis (S) at different dilutions was analysed. Furthermore a 2% essential oil concentrate was added to Origanum (OSi) and Salvia (SSi). In the two in vivo experiments in total 104 Slovak White Meaty pigs were fed with plant extracts (MW and O) at different doses with/without additional vitamin E.     

Salmonella spp. contamination in fresh pork and chicken sausages marketed in Niterói and Rio de Janeiro,Brazil

Fresh sausages are one of the most popular meat products consumed in Brazil. However, the use of contaminated raw material, unhygienic handling during processing, and inadequate storage could be hazardous to consumer’s health, since fresh-sausage processing does not include heat treatment and the product may carry several human pathogens such as Salmonella spp.. In this study, a total of 80 fresh sausages prepared with pork and chicken meat were evaluated regarding Salmonella spp. presence by PCR after selective enrichment and bacteriological culture. Twenty-one sausage samples (27 %) proved to be contaminated with Salmonella spp.. Sixteen (76 %) contaminated samples were detected by PCR combined with enrichment broth culturing, whereas conventional microbiological screening detected only 8 (38 %). In this study, evidence was raised regarding packing conditions of fresh sausages, since it seems that there is no significant difference in Salmonella spp. contamination among samples in their original packing (23 %), wrapped in plastic or unpacked (27 %). Similarly, meat composition seems not to have a determinant influence in contamination, since 20 % of the chicken and 29 % of the pork sausages were contaminated. The contamination rate of Tuscan-type sausages was 37 %, while contamination was found in 21 % of ham sausages, suggesting that the cut of pork did not have a determinant influence in the contamination by Salmonella in fresh sausages. The results shown here indicate that fresh sausages marketed in Niterói and Rio de Janeiro may be contaminated with Salmonella spp., requiring more attention by sanitary authorities in order to assure the safety of this food.     

Effect of dietary α-tocopherol supplementation on color and lipid stability in pork

Myoglobin and lipid oxidation are major causes of quality deterioration in fresh pork. A process to enhance color and lipid stability would prove valuable to the pork industry given the current trend of centralized packaging and distribution to retail markets. Our objective was to determine the effects of dietary α-tocopherol (α-Toc) supplementation on color and lipid stability in ground pork, and loin chops stored in modified atmosphere packaging (MAP). Yorkshire crossbred pigs (n=20) were randomized into two groups and fed diets containing 48 (CON) or 170 mg α-Toc acetate/kg feed (VIT-E) for 6 weeks before slaughter. Plasma α-Toc concentration was measured weekly. Post-slaughter, Boston butt shoulders were ground, formed into patties with or without 1.5% salt, and stored fresh at 4°C for 0, 2, 4, or 6 days, and frozen at −20°C for 45 or 90 days. Pork loin chops were packaged aerobically and stored at 4°C for 0, 2, 4 or 6 days, or in MAP at 4°C for 7, 10 or 13 days prior to Hunter L*,a*,b* and TBARS analyses. α-Toc concentration of longissimus dorsi, psoas major, biceps femoris, semimembranosus and semitendinosus muscles was determined. Plasma α-Toc was greater (P<0.05) in VIT-E animals compared with CON and α-Toc concentrations were greater (P<0.05) in all VIT-E muscles compared with CON. TBARS values of both fresh and salted patties were less in VIT-E than in CON meat following 6 days at 4°C; VIT-E TBARS of salted patties were less (P<0.05) after 45 days at −20°C compared with CON. α-Toc supplementation did not influence (P>0.05) color of aerobically packaged or MAP chops, or of fresh or salted pork patties. α-Toc supplementation reduced TBARS formation in fresh and salted pork but had no significant impact on color.     

Volatiles of the Balkan endemic Daucus guttatus ssp. zahariadii and cultivated and wild-growing D. carota – A comparison study

The hydrodistilled essential oil obtained from the aerial parts of Daucus guttatus Sibth. & Sm. ssp. zahariadii Heywood, an endemic plant species of the Balkan Peninsula, as well as solvent extracts and essential oils from different parts of Daucus carota L. have been analysed by GC and GC–MS and screened for antimicrobial activity against 12 bacterial and two fungal strains. The volatiles of the two plant taxa differed significantly in both their chemical identity and antimicrobial effect. The dominant constituent of D. guttatus oil was apiol (43.3%), which was absent from all samples of D. carota. The diethyl ether extract of D. carota inhibited the growth of the yeast Candida albicans while the oil of D. guttatus at 25 mg/ml had no effect on the growth of the fungal organisms tested. Additionally, the oil of D. guttatus showed prominent antibacterial activity against a pathogenic Corynebacterium pyogenes.     

Novel foods with microalgal ingredients – Effect of gel setting conditions on the linear viscoelasticity of Spirulina and Haematococcus gels

Microalgae represent an alternative and innovative source of natural ingredients that can be used in the development of novel food products. Biologically active compounds (e.g. carotenoids) are naturally encapsulated within microalgal cells, being able to resist harsh technological conditions involved in food technology processes. The aim of this work was to study the effect of adding Haematococcus pluvialis and Spirulina maxima microalgal biomass on the linear viscoelastic behaviour of vegetarian food gels prepared from pea protein, κ-carrageenan and starch. The gelation process was monitored in situ through dynamic oscillatory measurements, under different thermal profile conditions. Increasing temperature (70–90 °C, 5 min) resulted in more structured gels, while the effect of time (5–30 min, at 90 °C) was less pronounced. The effect of heating and cooling rates on gel setting was also studied. Haematococcus gels were highly structured and less dependent on gel setting conditions. Spirulina gels presented lower values of viscoelastic functions than the control (gel matrix without microalgae), but this was overcome when using lower heating/cooling rates.     

Development and validation of a predictive microbiology model for survival and growth of Salmonella on chicken stored at 4 to 12 °C

Salmonella spp. are a leading cause of foodborne illness. Mathematical models that predict Salmonella survival and growth on food from a low initial dose, in response to storage and handling conditions, are valuable tools for helping assess and manage this public health risk. The objective of this study was to develop and to validate the first predictive microbiology model for survival and growth of a low initial dose of Salmonella on chicken during refrigerated storage. Chicken skin was inoculated with a low initial dose (0.9 log) of a multiple antibiotic-resistant strain of Salmonella Typhimurium DT104 (ATCC 700408) and then stored at 4 to 12 °C for 0 to 10 days. A general regression neural network (GRNN) model that predicted log change of Salmonella Typhimurium DT104 as a function of time and temperature was developed. Percentage of residuals in an acceptable prediction zone, from -1 (fail-safe) to 0.5 (fail-dangerous) log, was used to validate the GRNN model by using a criterion of 70% acceptable predictions. Survival but not growth of Salmonella Typhimurium DT104 was observed at 4 to 8 °C. Maximum growth of Salmonella Typhimurium DT104 during 10 days of storage was 0.7 log at 9 °C, 1.1 log at 10 °C, 1.8 log at 11 °C, and 2.9 log at 12 °C. Performance of the GRNN model for predicting dependent data (n=163) was 85% acceptable predictions, for predicting independent data for interpolation (n=77) was 84% acceptable predictions, and for predicting independent data for extrapolation (n=70) to Salmonella Kentucky was 87% acceptable predictions. Thus, the GRNN model provided valid predictions for survival and growth of Salmonella on chicken during refrigerated storage, and therefore the model can be used with confidence to help assess and manage this public health risk.     

Effect of packaging atmosphere and pH on the virulence and growth ofYersinia enterocoliticaon pork stored at 4°C

Growth and virulence of pathogenicYersinia enterocoliticawere investigated on high (pH>6.0) and normal (pH<5.8) pH pork packaged in modified atmospheres and stored at 4°C. Modified atmospheres used in the study were vacuum packaging and saturated CO₂. Pork was packaged in a high gas barrier packaging film and examined over a 30-day period. Phenotypic characteristics were used to detect the presence of the virulence plasmid ofY. enterocoliticaafter exposure to the pork packaging and storage regimen. Phenotypic characteristics ofY. enterocoliticaisolates from pork loin stored at 4°C for 30 days that were studied included Congo red uptake, calcium dependence and autoagglutination in methyl red Voges–Proskauer broth and tissue culture medium. Numbers ofY. enterocoliticaon the lean surface of high pH pork slices increased approximately 2.7logcfucm⁻²when vacuum packaged and stored at 4°C for 30 days. Storage of inoculated normal pH pork in 100% CO₂resulted inY. enterocoliticaremaining in the lag phase over the storage period. Virulence ofY. enterocoliticawas maintained in 25 to 35% of isolates following storage for 30 days at 4°C in vacuum- and CO₂-packaged meats and was not affected by pH of the pork loin.     

Effect of rosemary extract, chitosan and α-tocopherol on microbiological parameters and lipid oxidation of fresh pork sausages stored at 4°C

The effect of rosemary extract, chitosan and α-tocopherol, added individually or in combination, on microbiological parameters and lipid oxidation of fresh pork sausages stored for 20 days at 4 °C was investigated. Microbiological determinations included the enumeration of Enterobacteriaceae, Pseudomonas spp., total viable count, yeasts and moulds and lactic acid bacteria, while pH values were also determined. Lipid oxidation was evaluated through measurement of primary (peroxide value) and secondary (malondialdehyde concentration) oxidation products. Chitosan addition resulted in significant (P ? 0.05) inhibition of microbial growth, while the lowest microbial counts were obtained in the samples containing both chitosan and rosemary, indicating a possible synergistic effect. Chitosan and its combinations with either α-tocopherol or rosemary, and especially the latter combination, showed also the most intense antioxidative effect (P ? 0.05), at least when compared to α-tocopherol alone or the controls, while use of rosemary extract alone had a comparable (P > 0.05) antioxidative effect with chitosan and its combinations. Shelf life of samples containing chitosan was almost doubled compared to the remaining samples. In conclusion, the best antimicrobial and antioxidative effects were obtained from the combination of chitosan with the rosemary extract.     

Effect of heating on the distribution of transforming growth factor-��2 in bovine milk

The objective of this study was to characterize the impact of heat treatments on the distribution of transforming growth factor-beta (TGF-??2) between cream and skim milk and between the casein and whey fractions of skim milk. Skimming removed 45% and 62% of the TGF-??2 from raw and pasteurized milks and only 8% of the total TGF-??2 in skimmed pasteurized milk was found in whey, compared to 37% in whey from raw skimmed milk. The TGF-??2 content of whey decreased as the heat treatment of the milk increased in intensity (thermization > pasteurization > UHT sterilization). Using milk held for 1 or 2 min at temperatures ranging from 57 to 84 °C, it was shown that TGF-??2 in the whey portion decreases at temperatures above 66 °C and becomes undetectable at temperatures higher than 76 °C. Altogether, these data on the heat-induced changes in TGF-??2 content of cream, skim milk, casein and whey reveal a potentially negative impact of certain heat treatments in developing TGF-??2-enriched fractions from milk.     

GC–MS quantification and sensory thresholds of guaiacol in orange juice and its correlation with Alicyclobacillus spp.

Guaiacol is a profoundly negative taint/off-flavour produced by the increasingly common microbial contamination of fruit juices with Alicyclobacillus spp. The objectives of this study included: determining sensory thresholds for guaiacol in orange juice (OJ), developing an analytical method whose detection limits were equivalent to sensory thresholds and determining levels of Alicyclobacillus spp. that would produce detectable levels of guaiacol. A 12 member trained panel was used to establish guaiacol detection and recognition thresholds. Guaiacol ortho and retro nasal detection thresholds in OJ were 0.70 and 0.53 μg/l respectively. Odour recognition threshold was 2.0 μg/l. A SPME GC–MS Selected Ion Monitoring (SIM) procedure was optimised to achieve analytical detection limits of 0.5 μg/l. Optimum guaiacol detection limit was achieved using only responses from m/z 109 and 124. Ion ratios (m/z 109/124) and linear retention index value matching were used to confirm the identification of guaiacol. Quantification was achieved using peak areas from standard guaiacol additions in orange juice between 0.5 and 100 μg/l. Alicyclobacillus growth of 2.2 log CFU/ml in OJ produced just detectable levels (0.7 μg/l) of guaiacol.     

Influence of human gastric juice on oxidation of marine lipids – in vitro study

This study evaluates whether marine lipids can oxidise in acidic stomach environment and whether authentic gastric juice has the potential to act as a pro- or anti-oxidative medium. Oxidation of herring lipids in emulsions and liposomes was followed in in vitro digestion models containing authentic human gastric juice, and compared to models containing hydrochloric acid solution. Peroxide value, concentration of thiobarbituric acid reactive substances and oxygen uptake rate increased in all the models during 2.5 h incubation at pH 4 and 37 °C in darkness. The markers showed no difference between oxidation in gastric juice and hydrochloric acid solution. Gastric juice reduced the prooxidant activity of iron ions measured as oxygen uptake rate, but did not reduce the activity of methemoglobin. Berry juice, green tea, red wine, and caffeic acid reduced oxygen uptake in the acidic environments while coffee, ascorbic acid and orange juice increased oxidation. Beverages accompanying foods containing marine lipids will therefore affect the course of post-prandial lipid oxidation.     

Effect of hydroxypropyl-β-cyclodextrin on the aggregation of (E)-resveratrol in different protonation states of the guest molecule

The aggregation state of (E)-resveratrol was studied in the presence and absence of hydroxypropyl-β-cyclodextrin (HP-β-CD) using absorption and steady-state fluorescence at different pH values. The results revealed that this potent antioxidant shows a monomer/aggregate equilibrium which is dependent on the protonation state of (E)-resveratrol. This equilibrium can be modified by the presence of HP-β-CD, which reduces the aggregation of the (E)-resveratrol molecules, producing individual molecules of the solute and preventing side effects due to aggregation phenomena. At pH values higher than the pK_a1 of (E)-resveratrol, the coexistence of different protonated/deprotonated forms of this antioxidant does not permit the fluorimetric determination of the complexation constant (K_F) of (E)-resveratrol with HP-β-CD. However, when the Hildebrand–Benesi equation was used to calculate this constant at physiological pH, this problem was resolved, with a K_F value of 14490 ± 723 M⁻¹ and the stoichiometry of the complexation process 1:1 for all the cases tested. The results obtained in this paper resolve the contradictory data published about the complexation process of (E)-resveratrol by cyclodextrins.     

Effect of Co γ-irradiation on postharvest quality and selected enzyme activities of Pleurotus nebrodensis

Freshly harvested Pleurotus nebrodensis fruit bodies were exposed to four different doses (0.8-2.0 kGy) of ⁶⁰Co γ-irradiation and various physiological changes associated with postharvest deterioration, as well as the activities of selected enzymes (proteinase, polyphenoloxidase, superoxide dismutase, catalase) thought to play a role in the process of deterioration, were monitored during 22 days of subsequent storage at 4 °C and 65-70% relative humidity. An irradiation dose of 1.2 kGy significantly delayed (by 6-9 days) the onset of fruit body softening, splitting and browning compared with non-irradiated controls and test samples subjected to lower or higher irradiation doses. Irradiation with 1.2 and 1.6 kGy also had a positive effect on other indicators of mushroom tissue senescence, resulting in smaller decreases in soluble protein levels and more protracted increases in proteinase activity. Peak levels of polyphenoloxidase activity, widely recognized as causing postharvest browning of mushroom tissue, were also significantly lower (P < 0.05) in fruit bodies exposed to 1.2 kGy compared with non-irradiated controls. Our data increase our understanding of the effects of γ-irradiation on the biochemical changes associated with postharvest deterioration in P. nebrodensis, and improve the prospects of more targeted strategies for extending the shelf life of both this and other mushrooms.     

Effect of γ-irradiation on antioxidant activity of black pepper (Piper nigrum L.)

Antioxidant activity and EPR investigations of irradiated ground black pepper (Piper nigrum L.) were evaluated. The black pepper was exposed to γ-irradiation at doses from 5 to 30 kGy. The effect of irradiation on antioxidant properties of black pepper extracts was investigated by radical-scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, by determination of reducing power and content of thiobarbituric acid-reactive substances. Some significant changes were observed in creation of thiobarbituric acid-reactive substances (TBARS). Difference between non-irradiated and irradiated samples at the legal European limit dose of 10 kGy reached, on average, 23% and, at the Food and Drug Administration (FDA) 30 kGy limit, 33%. Irradiation affected significantly the DPPH radical-scavenging activity and reducing power of ground black pepper extracts. The γ-radiation treatment of ground black pepper samples observed by EPR, resulted in the production of three paramagnetic species (GI–GIII) characterized by different origin, thermal behaviour and stability. The axially symmetric EPR resonances, GI and GII, were assigned to the carbohydrate radical structures. The spin Hamiltonian parameters of GIII possessed the characteristic features of “cellulosic” radical species. The EPR measurements, performed 20 weeks after the radiation process, confirmed that temperature increase from 298 to 353 K, caused significant decrease of integral EPR signal intensity for γ-irradiated samples (∼40%), compared to the reference (non-irradiated) ground black pepper, where only 13% drop was found. Significant correlation between EPR and thiobarbituric acid methods was assessed by study of antioxidant activity changes in relation to irradiation doses and also in the case of spice storage, between EPR and reducing power methods.     

Effect of 3 lactobacilli on immunoregulation and intestinal microbiota in a β-lactoglobulin–induced allergic mouse model

Milk is one of the earliest and most common allergen sources in the world, with β-lactoglobulin representing a major allergen protein. Numerous studies have reported that probiotics exert antiallergic and anti-inflammatory effects. Here, we examined the effects of 3 strains of Lactobacillus on immunomodulatory functions, intestinal barrier functions, and intestinal microbiota through a β-lactoglobulin–induced allergic mouse model. We found that the oral administration of Lactobacillus plantarum ZDY2013 and Lactobacillus rhamnosus GG suppressed allergic response, attenuating serum IgE and relieving anaphylaxis symptoms. The 3 strains of Lactobacillus could induce T helper (Th) 1 or T regulatory cells to differentiate to inhibit the Th2-biased response for regulating Th1/Th2 immune balance. Furthermore, L. plantarum ZDY2013 and L. rhamnosus GG enhanced intestinal barrier function through the regulation of tight junction. We also found that L. plantarum ZDY2013 and L. plantarum WLPL04 could regulate alterations in intestinal microbiota caused by allergies. In particular, Rikenella, Ruminiclostridium, and Lachnospiraceae UCG-006 were considerably reduced after treatment with L. plantarum ZDY2013 and L. plantarum WLPL04. These results suggested that 3 Lactobacillus strains may serve as an effective tool for the treatment of food allergies by regulating immune and gut microbiota.     

Use of sodium nitrite in salt-curing of Atlantic salmon (Salmo salar L.) – Impact on product quality

Quality changes during processing and quality differences in smoked fillets of Atlantic salmon (4–5 kg) salted with nitrite salt compared to table salted fillets were measured. Quality parameters from right-side fillets dry salted with nitrite salt were compared with the respective left-side fillets treated the same way with table salt. Ten raw right-side fillets were analysed and used as raw material reference. Use of nitrite salt in salt-curing of smoked salmon affected colour to a more reddish hue, tended to increase carotenoid stability and displayed positive effects on NaCl diffusivity. Only slight weight changes and change in texture properties were revealed. The use of nitrite salt displayed no adverse effects like increased content of N-nitrosoamines in smoked products. In fact, significant lower contents of N-nitrosoamines were found in nitrite salted smoked fillets compared to smoked fillets salted with table salt. Relatively high amounts of residual nitrite in nitrite-treated fillets seem to be the most prominent adverse effect caused by the use of nitrite salt in salt-curing of smoked Atlantic salmon.     

Effects of metal ions on growth, β-oxidation system,and thioesterase activity of Lactococcus lactis

The effects of divalent metal ions (Ca²⁺, Mg²⁺, Fe²⁺, and Cu²⁺) on the growth, β-oxidation system, and thioesterase activity of Lactococcus lactis were investigated. Different metal ions significantly influenced the growth of L. lactis: Ca²⁺ and Fe²⁺ accelerated growth, whereas Cu²⁺ inhibited growth. Furthermore, Mg²⁺ inhibited growth of L. lactis at a low concentration but stimulated growth of L. lactis at a high concentration. The divalent metal ions had significant effects on activity of the 4 key enzymes of the β-oxidation system (acyl-CoA dehydrogenase, enoyl-CoA hydratase, L-3-hydroxyacyl-CoA dehydrogenase, and thiolase) and thioesterase of L. lactis. The activity of acyl-CoA dehydrogenases increased markedly in the presence of Ca²⁺ and Mg²⁺, whereas it decreased with 1 mmol/L Fe²⁺ or 12 mmol/L Mg²⁺. All the metal ions could induce activity of enoyl-CoA hydratase. In addition, 12 mmol/L Mg²⁺ significantly stimulated activity of L-3-hydroxyacyl-CoA dehydrogenase, and all metal ions could induce activity of thiolase, although thiolase activity decreased significantly when 0.05 mmol/L Cu²⁺ was added into M17 broth. Inhibition of thioesterase activity by all 4 metal ions could be reversed by 2 mmol/L Ca²⁺. These results help us understand the effect of metal ions on the β-oxidation system and thioesterase activity of Lactococcus lactis.     

Effect of lyoprotectants on β-glucosidase activity and viability of Bifidobacterium infantis after freeze-drying and storage in milk and low pH juices

The benefit of disaccharide protectants for maintaining viability and β-glucosidase activity of Bifidobacterium infantis UV16PR during freeze-drying and storage in different food matrices was investigated. Protectants used were cellobiose, lactose, sucrose and trehalose.     

Inhibitory effect on α-glucosidase by the fruits of Terminalia chebula Retz.

Mammalian α-glucosidase inhibitory activity by Terminalia chebula Retz. fruits was investigated. The aqueous methanolic extract was found to have potent rat intestinal maltase inhibitory activity, whereas neither intestinal sucrase nor isomaltase activity was inhibited by this extract. Using bioassay-guided separation, three active ellagitannins were identified as chebulanin (1), chebulagic acid (2) and chebulinic acid (3) and were shown to possess potent intestinal maltase inhibitory activity, with the IC₅₀ values of 690 μM, 97 μM and 36 μM, respectively. The intestinal maltase inhibitory activities of 2 and 3 were even higher than that of 1,2,3,4,6-penta-O-galloyl-β-d-glucose (PGG) (4, IC₅₀=140 μM), which is a known potent α-glucosidase inhibitor. Comparison of the activities of 1–4, 1,2,3-O-trigalloyl-β-d-glucose (5), neochebulagic acid (6) and corilagin (7) suggested that the positions of chebulloyl and galloyl groups mostly affected the potency. Kinetic studies revealed that 2, 3, and 4 inhibited maltose-hydrolyzing activity of intestinal α-glucosidase, noncompetitively. This is the first report on mammalian α-glucosidase inhibition by 1, 2 and 3 isolated from T. chebula fruits. These results suggest a use of the extract of T. chebula fruits for managing Type 2 diabetes.