In vitro antimicrobial effects of Myristica fragrans essential oil on foodborne pathogens and its influence on beef quality during refrigerated storage

Nutmeg (Myristica fragrans) seed was subjected to the hydro-distillation method to extract its essential oil (NEO). Its main constituents were α-pinene (20.16%), sabinene (14.45%), and β-pinene (13.26%) with great antimicrobial and antioxidant actions. A novel edible coating was then fabricated based on the sage seed mucilage (SSM) and NEO, to ameliorate the quality and shelf-life of beef slices. The NEO-loaded SSM coating was able to significantly decrease the population of total viable count, Escherichia coli, Staphylococcus aureus, psychrotrophic bacteria, and fungi. Moreover, lipid oxidation of beef slices was remarkably suppressed upon the application of bioactive NEO-loaded SSM edible coating, as compared with the control by Day 6. The coated beef sample, especially NEO-rich SSM coated ones perceived a higher consumer acceptance and firmness than the SSM coated and noncoated samples. The SSM edible coating containing NEO could therefore have the potential to control the growth of pathogenic microorganisms and lipid oxidation, and to improve the color stability and sensory properties of meat and meat products.     

The antimicrobial effect of thyme essential oil, nisin, and their combination against Listeria monocytogenes in minced beef during refrigerated storage

The antimicrobial effect of thyme essential oil (EO) at 0.3%, 0.6%, or 0.9%, nisin at 500 or 1000IU/g, and their combination against Listeria monocytogenes was examined in both tryptic soy broth (TSB) and minced beef meat. Thyme EO at 0.3% possessed a weak antibacterial activity against the pathogen in TSB, whereas at 0.9% showed unacceptable organoleptic properties in minced meat. Thus, only the level of 0.6% of EO was further examined against the pathogen in minced meat. Treatment of minced beef meat with nisin at 500 or 1000IU/g showed antibacterial activity against L. monocytogenes, which was dependent on the concentration level of nisin and the strains used. Treatment of minced beef meat with EO at 0.6% showed stronger inhibitory activity against L. monocytogenes than treatment with nisin at 500 or 1000IU/g. All treatments showed stronger inhibitory activity against the pathogens at 10 degrees C than at 4 degrees C. The combined addition of EO at 0.6% and nisin at 500 or 1000IU/g showed a synergistic activity against the pathogen. Most efficient among treatments was the combination of EO at 0.6% with nisin at 1000IU/g, which decreased the population of L. monocytogenes below the official limit of the European Union recently set at 2logcfu/g, during storage at 4 degrees C.     

The antimicrobial effect of thyme essential oil, nisin and their combination against Escherichia coli O157:H7 in minced beef during refrigerated storage

The antimicrobial effect of thyme essential oil (EO) at supplementation levels of 0.3%, 0.6% or 0.9%, nisin at 500 or 1000 IU/g, and their combination, on Escherichia coli O157:H7 was examined in both tryptic soy broth (TSB) and minced beef meat. EO at 0.3% possessed a weak antibacterial activity against the pathogen in TSB, whereas at 0.9% showed unacceptable organoleptic properties in minced meat. Thus, only the level of 0.6% of EO was further examined against the pathogens in minced meat. Treatment of minced beef meat with EO at 0.6% showed an inhibitory activity against E. coli O157:H7 during storage at 10 °C, but not at 4 °C. Treatment of minced beef meat or TSB with nisin at 500 or 1000 IU/g did not show any antibacterial activity against E. coli O157:H7. The combination of EO at 0.6% and nisin at 500 or 1000 IU/g showed an additive effect against the pathogen, which was higher during storage at 10 °C than at 4 °C.     

Evaluation of antibacterial protein with antioxidant activity from Rahnella aquatilis L103 and its effect on beef during refrigerated storage

A strain, Rahnella aquatilis L103, which was isolated from the soil around the roots of mushrooms, produced antibacterial protein though fermentation. This protein has broad antibacterial spectrum towards gram-positive and gram-negative bacteria. The protein has a significant antioxidant capacity on scavenging ABTS^+· (82.5%, 120 μg mL⁻¹), DPPH^· (64.1%, 600 μg mL⁻¹) and OH^· (60.1%, 750 μg mL⁻¹) as well. The protein was considered to be safe within concentration of 150 μg mL⁻¹ as shown by MTT results and was applied to beef refrigerated preservation. The treatment group presented lower total viable counts (TVC), total volatile basic nitrogen (TVB-N), 2-thiobarbituric acid (TBA), meanwhile, higher sensory score and longer shelf life (2 days) compared with the control group (P < 0.05). The results indicated that the protein under safe concentration was beneficial to beef preservation.     

The effect of dietary oregano essential oil on microbial growth of rabbit carcasses during refrigerated storage

The effect of dietary supplementation with oregano essential oil on microbial growth of rabbit carcasses during refrigerated storage was investigated. A total of 45 weaned rabbits were separated into three equal groups with three subgroups each. One group was given the basal diet and served as control and the other two groups were administered diets supplemented with oregano essential oil at levels of 100 and 200 mg/kg diet, respectively (OR100 and OR200 groups). Total viable counts, Pseudomonas spp., lactic acid bacteria, Brochothrix thermosphacta, Enterobacteriaceae and yeast and mould counts, as well as off-odours and appearance of slime were all assessed on rabbit carcasses stored at 3 ± 1 °C for 12 days. The results showed that performance parameters were not affected (p > 0.05) whereas the dietary supplementation with oregano essential oil resulted in lower (p < 0.05) average microbial counts on the carcasses, compared to controls, throughout storage. Dietary supplementation with oregano essential oil at 200 mg/kg was more effective in inhibiting microbial growth compared with 100 mg/kg. Sensory evaluation scores indicated that the carcasses obtained from OR100 and OR200 groups gave a noticeable putrid odour after days 8 and 10, respectively, whereas the control carcasses developed off-odours after the 6th day of storage. Slime formation in the controls was observed after day 6, while the OR100 and OR200 groups were just beginning to show slime after days 8 and 10, respectively.     

Antimicrobial activity of eucalyptus essential oil against Pseudomonas in vitro and potential application in refrigerated storage of pork meat

The objective of this study was to investigate the influence of eucalyptus essential oil (EO) on the Pseudomonas in vitro and application in the pork meat. Eucalyptus oil showed the greatest antimicrobial activity to Pseudomonas among five EOs (tea tree oil, eucalyptus oil, clove oil, mentha oil and garlic oil) in vitro. Eucalyptus oil treatment caused the increasing of membrane permeability and the modifications of ultrastructure and morphology of Pseudomonas spp. and P. aeruginosa. Treatment of refrigerated pork with eucalyptus oil led to a significant decrease P. spp. count, pH, total volatile basic nitrogen and 2‐thiobarbituric acid values, as well as higher sensory scores of custom acceptance than those in control at the end of cold storage. It was conclude that eucalyptus EO is a potential alternative to chemical treatment to control the spoilage and extend the shelf life of refrigerated pork meat.     

孜然精油成分及其抗菌作用

以水蒸气蒸馏法提取孜然籽精油,产率2.6%,用GC-MS联机对精油进行成分分析,检测出28个成分,解析鉴定了占精油99.801%的26个成分,主要成分枯茗醛占总精油含量的39.511%,其次为2-蒈烯-10-醛(17.707%)和3-蒈烯-10-醛(17.542%).对精油和蒸馏后残渣有机溶剂萃取物的抗菌活性研究结果显示:孜然精油具有较强的抑菌作用,抑菌活性大小顺序为米曲霉＞枯草芽胞杆菌＞黑曲霉＞白色葡萄球菌＞大肠杆菌＞根霉;残渣有机溶剂萃取物抗菌活性较精油小.     

肉桂精油抑菌性及其在酱卤牛肉保鲜中的应用

以肉制品中常见的5种食品腐败菌和致病菌为研究对象,重点研究与酱卤肉加工过程相关的不同pH、温度、Na Cl浓度等对肉桂精油抑菌效果的影响,并进行气态防腐试验和酱卤牛肉保鲜实验。结果表明:肉桂精油具有广谱抑菌作用,对受试的5种菌均表现出良好的抑菌作用,其中以枯草芽孢杆菌对肉桂精油最为敏感。肉桂精油与pH存在协同抑菌的作用。在酸性环境中肉桂精油的抑菌性能强烈。肉桂精油与一定浓度范围的Na Cl有协同抑菌效果,且肉桂精油具有良好的热稳定性。气态防腐实验表明:肉桂精油具有良好的挥发性,不与菌体直接接触条件下,在密闭培养皿中对受试菌同样表现出良好的抑菌活性。经肉桂精油浸泡过的酱卤牛肉中微生物的生长受到明显的抑制。     

Evaluation of microbial inactivation and physicochemical properties of pressurized tomato juice during refrigerated storage

Effects of high pressure processing (300-500 MPa/25 °C/10 min) on microbial inactivation and processing qualities of tomato juices during refrigerated storage at 4 °C for 28 days were investigated to compare with those of conventionally thermal processing. Conventionally, thermal processing almost inactivated all the microorganisms and pectolytic enzymes and produced microbially and consistency stable tomato juices; however, they also reduced the color, extractable carotenoids and lycopene and vitamin C compared with fresh juice. During storage, all the pressure processing could improve the extractable carotenoids and lycopene contents compared with fresh juice, and they also retained more vitamin C contents than thermal processing. Although 300- and 400-MPa processing could retain a/b values of tomato juices as fresh juice during storage for 21 and 28 days, 500-MPa processing could improve the color of juices even after storage. Syneresis occurred in the 300- and 400-MPa processing juices by storing for 7 and 14 days; however, viscosity stable juice was produced by 500-MPa processing. Moreover, 400- and 500-MPa processing significantly inactivated microorganisms and the juices were microbially stable during storage. This study demonstrated that 500-MPa processing would be an alternative for conventionally thermal processing for tomato juice with improvement of some processing quality attributes.     

Antioxidant activity of carrot juice in gamma irradiated beef sausage during refrigerated and frozen storage

The antioxidant activity of carrot juice in gamma irradiated beef sausage was studied. Four batches of beef sausage were prepared, in which the first batch was formulated with water as the control. The other batches were formulated with unconcentrated carrot juice, carrot juice concentrated by 35% and 60%, respectively. Samples were irradiated at doses of 0, 3 and 4.5 kGy. Then the extent of oxidation in raw sausages was determined during refrigerated and frozen storage through the determination of peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) for lipid oxidation and carbonyl content for protein oxidation. The raw sausages were sensory evaluated during storage for colour, appearance and odour, while the grilled samples were sensory evaluated for their colour, odour, taste, texture and juiciness post-treatment only. Irradiation and storage significantly increased the PV, TBARS and carbonyl content in the samples formulated with water. The carrot juice significantly decreased the oxidative processes in the samples proportionally to the juice’s concentration. Furthermore, the sausages that were formulated with carrot juice had a high acceptable sensory scores as compared with the control samples.     

Phenolic content and antioxidant activity of donkey milk kefir fortified with sulla honey and rosemary essential oil during refrigerated storage

The aim of this work was to evaluate the phenolic content and antioxidant activity of donkey kefir fortified with sulla honey and rosemary essential oil, during refrigerated storage. The type of flavouring strongly influenced the antioxidant activity of the kefir: rosemary essential oil kefir showed the highest 2,2′‐azino‐bis‐(3‐ethylbenzthiazoline‐6‐sulfonic acid values; sulla honey kefir showed the highest ferric‐reducing antioxidant power values but, at the same time, in both fortified kefirs, the thiol content decreased, probably because of the formation of polyphenol‐protein complexes that would have influence the availability of bioactive components. The antioxidant activity increased significantly during refrigerated storage, showing the highest values after 15 days. Sensory analysis highlighted the fact that the donkey kefir was well accepted by consumers. Addition of sulla honey resulted in the highest acceptability, while addition of rosemary essential oil kefir was less accepted by consumers. This knowledge provides a basis that could lead to the production of fortified donkey kefir with specific nutraceutical characteristics.     

Microbiological and chemical quality of ground beef treated with sodium lactate and sodium chloride during refrigerated storage

The effects of sodium lactate (NaL) and sodium chloride (NaCl), either alone (30 g/kg) or in combination (20+20 g/kg), on the microbiological and chemical quality of raw ground beef during vacuum-packaged storage at 2°C were investigated. The results showed that addition of NaL alone or in combination with NaCl significantly delayed the proliferation of aerobic plate counts, psychrotrophic counts, lactic acid bacteria and Enterobacteriaceae and extended the shelf life of the product up to 15 and 21 days, respectively, versus 8 days only for control. Over the storage time (21 days), NaL maintained the ground beef at almost constant pH, while the pH of control or NaCl-treated samples significantly decreased. Lipid oxidation (TBA value) was not affected by addition of NaL. At storage day 21 however, TBA values of both NaL-treated (0.309) and control (0.318) samples were significantly lower than those of samples treated with NaCl (0.463). The combination of NaCl with NaL significantly reduced the oxidative changes caused by NaCl (0.384 versus 0.463). Therefore, NaL alone or in combination with NaCl could be utilized successfully to reduce the microbial growth, maintain the chemical quality, and extend the shelf life of ground beef during refrigerated storage.     

Effect of Eryngium caeruleum essential oil on microbial and sensory quality of minced fish and fate of Listeria monocytogenes during the storage at 4°C

The present study investigated in vitro antimicrobial activity of Eryngium caeruleum essential oil (EEO) against five foodborne pathogenic bacteria based on microdilution and disk diffusion methods. Moreover, its effects on specific spoilage microorganisms, inoculated Listeria monocytogenes, and its sensory changes in minced fish were evaluated during 12 days of storage at refrigeration temperature. The results showed that Staphylococcus aureus and Escherichia coli were the most sensitive and the most resistant bacteria with a minimum inhibitory concentration of 0.125 and 1 mg/ml, as well as inhibition zones of 15.66 and 11.66 mm, respectively. Regarding the antimicrobial effect of EEO on the microbial profile and inoculated L. monocytogenes, treating with 0.4% EEO caused a significant decrease in the studied microorganisms when compared to the control group (p < 0.05). In addition, considering the sensory evaluation, the best scores were observed for the samples treated with 0.2% and 0.4% EEO. However, none of the groups obtained acceptable scores until the final day of storage except for the color attribute. In general, sensory evaluation and its correlation with microbial counting indicated that the treatment with 0.4% EEO was able to preserve the microbial quality of the minced fish at refrigeration temperature without any undesirable sensory effects.