Effects of Essential Oil Vapour Treatment on the Postharvest Disease Control and Different Defence Responses in Two Mango (<Emphasis Type="Italic">Mangifera indica</Emphasis> L.) Cultivars

The purpose of this study was to investigate the inhibitory effect of essential oils (thyme, clove and cinnamon) in vapour phase against the major fungal diseases of mango in vitro and in vivo. Thyme oil vapour (5 μL/Petri plate) completely inhibited the mycelial growth of Colletotrichum gloeosporioides and Lasiodiplodia theobromae under in vitro condition. Thyme oil vapour at 66.7 μL L^?1 significantly reduced artificially inoculated C. gloeosporioides and L. theobromae in mangoes for 4 days. GC/MS analysis revealed thymol, eugenol and benzofuran, 3-methyl as the dominant compounds in thyme, clove and cinnamon oils, respectively. The activities of defence and antioxidant enzymes including peroxidase, chitinase, phenylalanine ammonia-lyase, β-1,3-glucanase, catalase and superoxide dismutase were enhanced by thyme oil (66.7 μL L^?1) treatment and also help to maintain the phenolic content. Hence, postharvest thyme oil vapour treatment may prove to be an alternative means of controlling disease in mangoes.     

植物复合精油对5种稻谷霉变优势菌株抑菌作用研究

为了研究天然植物精油(百里香、丁香、肉桂)对霉变稻谷的抑菌效果,以5种稻谷霉变优势菌株为受试菌,以霉菌抑菌圈直径大小和最低抑菌浓度（MIC）为指标,通过混料设计方法建立复合精油抑菌模型,结合方差分析得到抑菌效果最佳的植物精油配比。研究结果表明,单一精油抑菌活性对亮白曲霉（A. candidus）,杂色曲霉（A. versicolor）和聚多曲霉（A. sydowii）为肉桂精油>丁香精油>百里香精油;对稻黑孢霉（N. oryzae）为肉桂精油=丁香精油>百里精香油;对布罗克青霉菌（P. brocae）为丁香精油=百里香精油<肉桂精油。当肉桂精油:丁香精油:百里香精油的体积比为55.2%︰26.9%︰17.9%时,3种植物精油对5种菌株抑制效果最佳,复合抑制值大于90.9%。     

Effects of essential oils and oleoresins of plants on ethanol production,respiration and sporulation of yeasts

Ethanol production, respiration, and sporulation of yeasts as effected by essential oils and oleoresins of allspice, cinnamon, clove, garlic, onion, oregano, savory, and thyme were investigated. Essential oils of allspice, cinnamon, and clove had little or no effect on ethanol production by Sacchraromyces cerevisiae. Oils of onion, oregano, savory, and thyme delayed and/or reduced the production of ethanol. Overall, essential oils effectively suppressed ethanol production by Hansenula anomala. At the highest concentrations tested (500 μg/ml), only cinnamon, clove, garlic and thyme oleoresins substantially delayed and/or reduced ethanol production by S. cerevisiae. Most of the essential oils (100 μm/ml) impaired the respiratory activity of S. cerevisiae as evidenced by a reduction in CO₂ production. Thyme oleoresin was the strongest inhibitor. Allspice and garlic oils impaired sporulation by H. anomala. All oils delayed sporulation of Lodderomyces elongisporus).     

Essential oil nanoemulsions: antibacterial activity in contaminated fruit juices

Many human acid tolerant bacterial and fungal pathogens can be transmitted through the consumption of the contaminated fruit juices. We aim to formulate essential oil nanoemulsions (basil, black seed, turmeric, clove & cinnamon), determine their ability to clear contamination by food borne bacterial pathogens from fruit juices. The antibacterial activity of the optimised formulations was tested in the fruit juices against bacterial pathogens causing gastrointestinal tract infections. The minimum bactericidal concentration (MBC) of clove emulsions ranged from 15.6 to 25 μL mL⁻¹. Cinnamon oil emulsion had an MBC ranging between 15 and 31 μL mL⁻¹. At MBC, cinnamon oil emulsions caused a 6log₁₀ decrease in viable counts by 8 h and maintained the sterility of fruit juices for 7 days at ambient temperature. Thus, clove and cinnamon microemulsions can be used as juice additives to control food borne bacterial pathogens and maintain the bacterial sterility of fruit juices.     

Antimicrobial efficacies of essential oils/nanoparticles incorporated polylactide films against L. monocytogenes and S. typhimurium on contaminated cheese

Polylactide based films were formulated by incorporating polyethylene glycol, selected nanopowders (zinc oxide, silver-copper), and essential oils (cinnamon, garlic, and clove) by solvent casting method. Films were tested against three foodborne pathogens (one gram-positive and two gram-negative) for their antibacterial activity. The effectiveness of selected cinnamon oil-based film was ascertained by performing a challenge test with cheese as a food model. In vitro antibacterial efficacies of nanopowders and essential oils were also determined by the decimal reduction concentrations and the minimum bactericidal concentrations for those foodborne pathogens. It was observed that nanopowders exhibited considerably poorer decimal reduction concentrations and minimum bactericidal concentration values in comparison to the essential oils. Silver-copper alloy nanopowders exhibited lower decimal reduction concentrations and minimum bactericidal concentrations values than ZnO against tested pathogens whereas essential oils showed distinct antimicrobial effectiveness against all those pathogens with in vitro decimal reduction concentration values of 87–157 and 77–220 µg/mL for cinnamon and clove oils, respectively. Among the various formulations, it was observed that only essential oils (especially cinnamon and clove) incorporated films exhibited a significant antimicrobial activity against the selected microorganisms. These results indicate that the poor antibacterial activity of the nanopowders and the hydrophobicity of polylactide could be responsible for the ineffectiveness of nanopowders in polylactide based films. Furthermore, the challenge test indicated the polylactide/polyethylene glycol/cinnamon oil film was appropriate to inhibit the growth of L. monocytogenes and S. typhimurium on cheese up to 11 days at refrigerated storage.     

Effects of Essential Oils from Plants on Growth of Food Spoilage Yeasts

Thirty-two essential oils from plants were screened for inhibitory effects on 13 food-spoilage and industrial yeasts. Of these, essential oils of allspice, cinnamon, clove, garlic, onion, oregano, savory, and thyme were most inhibitory. Oils were subsequently tested for their effects on biomass production and pseudomycelium formation of eight genera of yeasts. Garlic oil was a potent inhibitor of yeast growth at concentrations as low as 25 ppm. The oils of onion, oregano and thyme were also strongly inhibitory. Essential oils (100 ppm) had no effect on pseudomycelium production by Candida lipolytica. However, all eight essential oils delayed pseudomycelium formation by Hansenula anomala, whereas six oils stimulated pseudomycelium production by Lodderomyces elongisporus. Cinnamon and clove oils were clearly stimulatory to pseudomycelium production by Saccharomyces cerevisiae.     

Inhibition of Growth and Germination of C. botulinum 33A, 40B, and 1623E by Essential Oil of Spices

Effects of clove, thyme, black pepper, pimenta, origanum, garlic, onion, and cinnamon oils on growth and germination of Clostridium botulinum types 33A, 40B, and 1623E were studied. At 200 ppm, ail oils highly inhibited growth of C. botulinum 33A, 40B, and 1623E. At 10 ppm, inhibitory activity of most oils diminished. By activity on C. botulinum growth, oils could be divided into three categories: (1) very active: cinnamon, origanum, and clove; (2) active: pimenta, and thyme; (3) least active: garlic, onion, and black pepper. Effectiveness on germination was quite different. At 150 and 200 ppm all oils totally prevented germination. At 10 ppm garlic and onion showed higher activity than the others. Spores of 33A were more sensitive than 40B and 1623E.     

Antibacterial properties of plant essential oils

Fifty plant essential oils were examined for their antibacterial properties against 25 genera of bacteria. Four concentrations of each oil were tested using an agar diffusion technique. The ten most inhibitory oils were thyme, cinnamon, bay, clove, almond (bitter), lovage, pimento, marjoram, angelica and nutmeg. The most comprehensively inhibitory extracts were angelica (against 25 genera), bay (24), cinnamon (23), clove (23), thyme (23), almond (bitter) (22), marjoram (22), pimento (22), geranium (21) and lovage (20).     

An integrated strategy to control post-harvest decay of Embul banana by combining essential oils with modified atmosphere packaging

Mature Embul (Musa, AAB) bananas were treated with emulsions of either cinnamon bark or leaf (Cinnamomum zeylanicum) or clove (Syzygium aromaticum) oils to control post‐harvest diseases, packed under modified atmosphere (MA) using low‐density polyethylene (0.075 mm, LDPE) bags, and stored in a cold room (14 ± 1 °C, 90% RH) or at ambient temperature (28 ± 2 °C). The effects of the essential oils on post‐harvest diseases; physico‐chemical properties and organoleptic properties were determined and compared with controls and bananas treated with benomyl. Treatments with cinnamon bark and leaf oils controlled crown rot, whereas clove oil treatment did not affect crown rot development. Treatment with emulsions of cinnamon oils combined with MA packaging can be recommended as a safe, cost‐effective method for extending the storage life of Embul bananas up to 21 days in a cold room and 14 days at 28 ± 2 °C without affecting the organoleptic and physico‐chemical properties.     

Antimicrobial Efficacy of an Array of Essential Oils Against Lactic Acid Bacteria

The essential oils of clove bud, cinnamon bark and thyme, and their individual compounds including allyl isothiocyanate (AIT), carvacrol, cinnamaldehyde, cinnamic acid, eugenol, and thymol were initially assessed for antimicrobial activity against 9 lactic acid bacteria (LAB) species. Carvacrol and thymol were the most inhibitory with MICs of 0.1% (v/v and w/v, respectively). Cinnamaldehyde, cinnamon bark oil, clove bud oil, eugenol, and thyme oil were moderately inhibitive (MICs = 0.2% v/v), while cinnamic acid required a concentration of 0.5% (w/v). AIT was not effective with MICs in excess of concentrations tested (0.75% v/v). The bactericidal capability of the oil components carvacrol, cinnamaldehyde, eugenol, and thymol were further examined against Pediococcus acidilactici, Lactobacillus buchneri, and Leuconostoc citrovorum. Thymol at 0.1% (w/v) was bactericidal against L. citrovorum (>4‐log reduction), but resulted in a 2‐log CFU/mL reduction against L. buchneri and P. acidilactici. Cinnamaldehyde at 0.2% to 0.25% (v/v) was effective against L. citrovorum, L. buchneri, and P. acidilactici, resulting in a >2‐log reduction. All 3 organisms were susceptible to 0.2% carvacrol with >3‐log reduction observed after exposure for 6 h. Eugenol was the least effective. Concentrations of 0.2% and 0.25% (v/v) were needed to achieve an initial reduction in population, >3‐log CFU/mL after 6 h exposure. However, at 0.2%, P. acidilactici and L. buchneri recovered to initial populations in 48 to 72 h. Results indicate essential oils have the capacity to inactivate LAB that are commonly associated with spoilage of shelf stable low‐acid foods.     

Efficacy of plant essential oils as antimicrobial agents against Listeria monocytogenes in hotdogs

The purpose of this study was to evaluate the antimicrobial activity of different plant essential oils against Listeria monocytogenes, both in vitro and in a food system. Essential oils of thyme, clove, and pimenta were found to be most effective, based on disc diffusion experiments. Thyme and clove proved to be highly effective against L. monocytogenes in peptone water (1 g/l) and reduced the bacterial population below detection limits at concentrations of 1 ml/l. Experiments were also carried out in hotdogs of different fat content (zero-, low-, and full-fat) to evaluate the antimicrobial activity of essential oils against L. monocytogenes. Thyme essential oil reduced bacterial populations significantly (P⩽0.05) at 1 ml/l level in zero- and low-fat hotdogs, but not in full-fat hotdogs. At 10 ml/l level it reduced the bacterial population >1.3 log₁₀ cfu/g in zero-fat hotdogs, but was less effective in low- and full-fat hotdogs. Clove essential oil also exhibited antimicrobial activity at 1 ml/l in all hotdogs, and was more effective than thyme at 5 ml/l. However, increasing concentration to 10 ml/l did not result in significant (P⩽0.05) reduction of bacterial population. It is concluded that efficacy of essential oils was reduced in a food system due to interaction with food components.     

Original article: Antifungal activities of cinnamon oil against Rhizopus nigricans,Aspergillus flavus and Penicillium expansum in vitro and in vivo fruit test

The postharvest pathogens such as R. nigricans, A. flavas and P. expansum are the causal agents of jujube or orange fruit, therefore, in vitro and in vivo antifungal activities of cinnamon oil to inactivate these fungi were investigated. Cinnamaldehyde is the main constituent of cinnamon oil. The minimum inhibitory concentrations of cinnamon oil against Rhizopus nigricans, Aspergillus flavus and Penicillium expansum were 0.64% (v/v), 0.16% (v/v) and 0.16% (v/v), respectively. The antifungal activity of cinnamon oil against A. flavus and P. expansum was stronger than that against R. nigricans and the activity was improved with increasing its concentration. In an in vivo study, cinnamon oil with concentrations of 2.0% (v/v) and 3.0% (v/v) showed complete control the growth of fungi in wound‐inoculated Lingwu Long Jujube and Sand Sugar Orange fruits. These results revealed that cinnamon oil has a good potential to be as a natural antifungal agent for fruit applications.     

鲜切西兰花贮藏期病原菌分离鉴定及植物精油对其抑制效果

以‘冬至绿’西兰花为试材,分离、纯化并鉴定鲜切西兰花贮藏期病原菌,筛选出抑制病原菌效果较好的植物精油。通过分离、纯化及致病性实验得到病原真菌菌株AB01,以病原菌内源转录间隔区序列进行进化树分析,鉴定该病原菌为链格孢菌（Alternaria alternata）。选用肉桂、茴香、牛至、丁香、百里香和香茅6 种精油对AB01进行抑菌性实验,通过体外抑菌和活体抑菌筛选出最优的精油种类及含量。结果发现,肉桂精油对AB01的抑菌效果最好,其最低抑菌浓度和最低杀菌浓度分别为0.05 μL/mL和0.15 μL/mL,其次是茴香和牛至精油。0.15 μL/mL肉桂精油用于鲜切西兰花可有效降低花球黄花率和切面褐变率。     

丁香和肉桂挥发油的提取、主要成分测定及其抗菌活性研究

本文采用水蒸汽蒸馏法提取丁香和肉桂的挥发油,并对所得挥发油主要成分进行气相测定,通过体外抗菌试验,比较了这两种挥发油及其主要成分和目前常用化学防腐剂苯甲酸钠和山梨酸钾对金黄色葡萄球菌、大肠杆菌、枯草芽孢杆菌、沙门氏菌和志贺氏菌等5株食品中常见污染菌的抗菌作用。结果表明丁香油中丁香酚含量为78.1%,肉桂油中肉桂醛含量为86.8%;这两种挥发油及其主要成分丁香酚和肉桂醛的抗菌作用均强于两种化学防腐剂,其中肉桂油与其主要成分肉桂醛表现出的抗菌活性最强,最小抑菌浓度(MIC)为200～1600mg/L;仅为苯甲酸钠和山梨酸钾MIC(6400～25600mg/L)的1/64～1/16;丁香油及其主要成分丁香酚的抗菌活性次之,MIC为800～1600mg/L,相当于苯甲酸钠和山梨酸钾MIC的1/16～1/8。     

Prolonging Storage Time of Baby Ginger by Using a Sand‐Based Storage Medium and Essential Oil Treatment

Wilt and rot occur readily during storage of baby ginger because of its tender skin and high moisture content (MC). A storage medium, which consisted of sand, 20% water, and 3.75% super absorbent polymers delayed weight loss and loss of firmness at 12 °C and 90% relative humidity. Microorganisms were isolated and purified from decayed rhizomes; among these, 3 fungi were identified as pathogens. The results of 18S rDNA sequence analysis showed that these fungi belonged to Penicillium, Fusarium, and Mortierella genera. The use of essential oil for controlling these pathogens was then investigated in vitro. Essential oils extracted from Cinnamomum zeylanicum (cinnamon) and Thymus vulgaris (thyme) completely inhibited the growth of all of the above pathogens at a concentration of 2000 ppm. Cinnamon oil showed higher antifungal activity in the drug sensitivity test with minimal fungicidal concentration (<500 ppm against all pathogens). In the in vivo test, cinnamon fumigation at a concentration of 500 ppm reduced infection rates of Penicillium, Fusarium, and Mortierella by 50.3%, 54.3%, and 60.7%, respectively. We recommended cinnamon oil fumigation combined with medium storage at 12 °C as an integrated approach to baby ginger storage.     

生姜贮藏期病原菌分离鉴定及精油抑菌效果

分离、纯化及鉴定生姜贮藏期病原菌,筛选出对抑制病原菌效果较好的精油并验证该精油抑菌效果。通过分离、纯化及致病性实验得到了病原菌菌株ljr4及ljw2。以病原菌18S rDNA序列进行进化树分析,结果表明该两种病原菌分别属于镰刀菌属及被孢霉属。根据病原菌种属选择了6 种精油进行抑菌性实验,结果发现肉桂精油及百里香精油在用量为2 000 μL/L时对病原菌生长抑制率均为100%。在药敏实验中发现肉桂精油比百里香精油抑菌活性更强。肉桂精油对ljr4、ljw2这2 种病原菌最低抑菌用量分别为64、32 μL/L,最低杀菌用量分别为125、500 μL/L。与未熏蒸生姜相比,在贮藏30 d后肉桂精油熏蒸处理分别使接种ljr4及ljw2的生姜感病率下降了59.33%和47.33%。肉桂精油作为生姜贮藏前的熏蒸剂有较好的应用前景。     

Effects of Allspice, Cinnamon, and Clove Bud Essential Oils in Edible Apple Films on Physical Properties and Antimicrobial Activities

ABSTRACT:  Essential oils (EOs) derived from plants are rich sources of volatile terpenoids and phenolic compounds. Such compounds have the potential to inactivate pathogenic bacteria on contact and in the vapor phase. Edible films made from fruits or vegetables containing EOs can be used commercially to protect food against contamination by pathogenic bacteria. EOs from cinnamon, allspice, and clove bud plants are compatible with the sensory characteristics of apple-based edible films. These films could extend product shelf life and reduce risk of pathogen growth on food surfaces. This study evaluated physical properties (water vapor permeability, color, tensile properties) and antimicrobial activities against  Escherichia coli  O157:H7,  Salmonella enterica,  and  Listeria monocytogenes  of allspice, cinnamon, and clove bud oils in apple puree film-forming solutions formulated into edible films at 0.5% to 3% (w/w) concentrations. Antimicrobial activities were determined by 2 independent methods: overlay of the film on top of the bacteria and vapor phase diffusion of the antimicrobial from the film to the bacteria. The antimicrobial activities against the 3 pathogens were in the following order: cinnamon oil > clove bud oil > allspice oil. The antimicrobial films were more effective against  L. monocytogenes  than against the  S. enterica . The oils reduced the viscosity of the apple solutions and increased elongation and darkened the colors of the films. They did not affect water vapor permeability. The results show that apple-based films with allspice, cinnamon, or clove bud oils were active against 3 foodborne pathogens by both direct contact with the bacteria and indirectly by vapors emanating from the films.     

Antibacterial activities of naturally occurring compounds against antibiotic-resistant Bacillus cereus vegetative cells and spores, Escherichia coli, and Staphylococcus aureus

After demonstrating the lack of effectiveness of standard antibiotics against the acquired antibiotic resistance of Bacillus cereus (NCTC 10989), Escherichia coli (NCTC 1186), and Staphylococcus aureus (ATCC 12715), we showed that the following natural substances were antibacterial against these resistant pathogens: cinnamon oil, oregano oil, thyme oil, carvacrol, (S)-perillaldehyde, 3,4-dihydroxybenzoic acid (beta-resorcylic acid), and 3,4-dihydroxyphenethylamine (dopamine). Exposure of the three pathogens to a dilution series of the test compounds showed that oregano oil was the most active substance. The oils and pure compounds exhibited exceptional activity against B. cereus vegetative cells, with oregano oil being active at nanogram per milliliter levels. In contrast, activities against B. cereus spores were very low. Activities of the test compounds were in the following approximate order: oregano oil > thyme oil approximately carvacrol > cinnamon oil > perillaldehyde > dopamine > beta-resorcylic acid. The order of susceptibilities of the pathogens to inactivation was as follows: B. cereus (vegetative) > S. aureus approximately E. coli > B. cereus (spores). Some of the test substances may be effective against antibiotic-resistant bacteria in foods and feeds.     

DPPH free-radical scavenging ability, total phenolic content, and chemical composition analysis of forty-five kinds of essential oils

Forty-five kinds of commonly used essential oils were employed to investigate the DPPH (1,1-diphenyl2-picrylhydrazyl) radical scavenging ability and total phenolic content of major chemical compositions. The free-radical scavenging ability and total phenolic content of cinnamon leaf and clove bud essential oils are the best among these essential oils. One-half milliliter of cinnamon leaf and clove bud essential oils (10 mg mL EtOH) are shown to be 96.74% and 96.12% of the DPPH (2.5ml, 1.52 × 10^-4 M) free-radical scavenging ability, respectively. Their EC50 (effective concentrations) are 53 and 36 (μg mL^-1). One milligram per milliliter of cinnamon leaf, clove bud, and thyme red essential oils were shown to be 420, 480, and 270 (mg g^-1 of GAE) of total phenolic content, respectively. Eugenol in cinnamon leaf and clove bud essential oils (82.87% and 82.32%, respectively) were analyzed by GC-MS. It is clear that the amounts of the phenol compounds in essential oils and the DPPH free-radical scavenging ability are in direct proportion.     

Antimicrobial Wine Formulations Active Against the Foodborne Pathogens Escherichia coli O157: H7 and Salmonella enterica

ABSTRACT:  We developed wine formulations containing plant essential oils and oil compounds effective against foodborne pathogenic bacteria Escherichia coli O157:H7 and Salmonella enterica. HPLC was used to determine maximum solubility of antimicrobials in wines as well as amounts of antimicrobials extracted by wines from commercial oregano and thyme leaves. Activity of essential oils (cinnamon, lemongrass, oregano, and thyme) and oil compounds (carvacrol, cinnamaldehyde, citral, and thymol) in wines were evaluated in terms of the percentage of the sample that resulted in a 50% decrease in the number of bacteria (BA₅₀). The ranges of activities in wines (30 min BA₅₀ values) against S. enterica/E. coli were carvacrol, 0.0059 to 0.010/0.011 to 0.021; oregano oils, 0.0079 to 0.014/0.022 to 0.031; cinnamaldehyde, 0.030 to 0.051/0.098 to 0.13; citral, 0.033 to 0.038/0.060 to 0.070; lemongrass oil, 0.053 to 0.066/0.059 to 0.071; cinnamon oil 0.038 to 0.057/0.066 to 0.098; thymol, 0.0086 to 0.010/0.016 to 0.022; and thyme oil, 0.0097 to 0.011/0.033 to 0.039. Detailed studies with carvacrol, the main component of oregano oil, showed that antibacterial activity was greater against S. enterica than against E. coli and that wine formulations exhibited high activities at low concentrations of added antimicrobials. The results suggest that wines containing essential oils/oil compounds, added or extracted from oregano or thyme leaves, could be used to reduce pathogens in food and other environments.