Department of Crop Production

Seven types of coffee were prepared by four methods. Three of them -simple coffee infusion, preparation in ibrick and moka pot -are very often used to prepare coffee at home. The fourth one -a single-cup filter is typical for Vietnam. Cookware used for each method was made from glass, aluminium, stainless steel and two types of alloys. Amounts of Al leaching to coffee infusions were determined. On average, the highest amount of Al was in coffee infusions brewed in aluminium single-cup filter, and the lowest in infusions prepared by simple extraction. Other brewing methods in combination with different tool materials resulted in similar Al content. The type of brewing method significantly influences the Al content in final infusion. Aluminium content varies in infusions in relation to the method of choice, especially when using single-cup filter. Despite the fact that coffee is considered to be a poor source of Al for humans, in some cases, Al content in infusions can even reach the values reported for tea infusions.

The determination of Al, B, Cu, Fe, Mn, Ni, P, Zn and Ca, K, Mg by inductively coupled plasma optical emission spectrometry (ICP-OES) and flame atomic absorption spectroscopy (FAAS), respectively, in digests and infusions of Hibiscus sabdariffa (petals), Rosa canina (receptacles), Ginkgo biloba (leaves), Cymbopogon citratus (leaves), Aloe vera (leaves) and Panax ginseng (roots) was carried out in this study. Particular attention has been given to Al and heavy metals for the identification of possible raw material contaminants, their transformation into the infusion and for predicting their eventual role in the human diet during daily consumption. Additionally, Ion Chromatography (IC) speciation of Al in the leachates was carried out.

Due to their antimicrobial activity, essential oils (EOs) have potential to alternate conventional food preservatives. Relatively high doses of EOs necessary for microbial growth inhibition indicate that they should be used in combination with other preservation techniques rather than alone. Therefore, new combinations of preservative methods with EOs are still investigated. In our study, oregano, clove, cinnamon, and lemongrass EO vapors were tested in vitro in atmospheric and low pressure against Escherichia coli and Salmonella enteritidis at different times of treatment ranging from 5 min to 4 h. Combination of EO-low pressure shortened up to 48 times the time necessary for total inhibition of microorganism growth compared to the same treatment in atmospheric pressure. Minimal inhibitory times of EOs vapors ranged mostly from 15 to 60 min in low pressure and were equal to or more than 4 h in atmospheric pressure. Possible decrease of MICs of EOs in low pressure was also investigated. Microorganisms demonstrated increased susceptibility to oregano, lemongrass and cinnamon EOs in low pressure e.g. the MIC of cinnamon vapors for S. enteritidis decreased from 512 mL/L to 128 mL/L.

Alkaloidal extracts of seven selected plants of the family Papaveraceae were studied with respect to their activity against six strains of pathogenic bacteria and their alkaloidal fingerprint. Twenty-four alkaloids were determined by GC/MS, and twenty of them identified from their mass spectra, retention times and retention indexes. In the antibacterial assay, three Gram-positive (Enterorococcus faecalis, Staphylococcus aureus and S. hyicus), and three Gram-negative (Escherichia coli, Proteus mirabilis and Pseudomonas aeruginosa) strains were used. The most promising antimicrobial activity was shown by the alkaloidal extract of Macleaya cordata with MIC values of 16 μg/mL for Staphylococcus aureus, 32 μg/mL for Enterococcus faecalis and 64 μg/mL for Staphylococcus hyicus and Escherichia coli. All the tested pure isoquinoline alkaloids were considered inactive within the tested concentrations.

Cronobacter sakazakii and C. malonaticus are opportunistic pathogens that cause infections in children and immunocompromised adults. In the present study, the antibacterial activity of 19 plant-derived compounds, 5 essential oils, and an extract of propolis were assessed against C. sakazakii and C. malonaticus. The effects of most of these antimicrobials have not been reported previously. Both strains were susceptible to thymol, carvacrol, thymoquinone, p-cymene, linalool, camphor, citral, eugenol, and trans-cinnamaldehyde as well as cinnamon, lemongrass, oregano, clove, and laurel essential oils; their minimum inhibitory concentrations varied between 0.1 and 2.0 mg/mL. As an alternative treatment method, vapors of the volatiles were tested as an indirect treatment. Vapors of trans-cinnamaldehyde, eugenol, oregano, and cinnamon essential oils inhibited both tested strains, while vapors of linalool were only active against C. sakazakii. To our knowledge, this study is the first time that the inhibitory activity of the vapors of these compounds and essential oils has been reported against Cronobacter spp.

BACKGROUND: Microbial load can be controlled using either synthetic or natural preservatives. Particular interest has been focused on the potential application of plant essential oils as safer additives for meat. However, there is no published research on the use of essential oils during the meat drying process. This study was focused on enhancing the meat drying process by using oregano essential oil (OEO) to inhibit the growth of bacteria and thus obtain a value-added dried meat product. The sensory response from assessors is presented. RESULTS: It was found that the application of OEO in meat was effective in inhibiting Salmonella enteritidis and Escherichia coli. After 6 h of drying at 55 ∘ C, 2 mL (0.038 mL L −1 air) and 1.5 mL (0.028 mL L −1 air) of OEO were considered as the minimal inhibitory concentrations (MICs) against S. enteritidis and E. coli respectively. Samples treated with 0.75 mL of OEO were more attractive for consumption compared with the control; at a higher concentration of OEO, the sensory quality of the food was affected. CONCLUSION: A value-added dried meat product obtained by using OEO to enhance food safety received an acceptable sensory response from consumers.

Among promising alternative methods to control food spoilage much attention is being paid to the use of essential oils (EOs), and lately also to their activity in vapor phase. Until now, no standard assay exists, and there are many methods used by different authors, but any of them is suitably adapted for fast screening of large quantities of samples. We have modified most commonly used disc volatilization method by using foursection Petri dish (PD, 90 mm diameter), large filter paper disc (85 mm diameter) evenly impregnated with EO and medium containing lid. In comparison to normal disc volatilization method, labor and material needed are several times reduced, while the composition of headspace is more uniform than in case of 6 mm disc, where different volatility of particular compounds could influence the results. Sixty nine EOs were tested for its antimicrobial activity against three bacteria (Staphylococcus aureus, Salmonella enteritidis, Pseudomonas aeruginosa) and three fungi (Alternaria alternata, Aspergillus niger, Penicillium digitatum). Thirty nine EOs inhibited at least one microorganism, Armoracia rusticana and Cinnamomum zeylanicum being the most active, followed by EOs of Eugenia caryophyllata, Origanum compactum, Origanum vulgare, Pimenta racemosa, Thymus serpyllum and Thymus vulgaris inhibiting all six or five microorganisms, respectively. According to our opinion, this method is suitable for screening of large quantities of samples for antimicrobial activity in vapor phase.

Seven types of coffee were prepared by four methods. Three of them-simple coffee infusion, preparation in ibrick and moka pot-are very often used to prepare coffee at home. The fourth one-a single-cup filter is typical for Vietnam. Cookware used for each method was made from glass, aluminium, stainless steel and two types of alloys. Amounts of Al leaching to coffee infusions were determined. On average, the highest amount of Al was in coffee infusions brewed in aluminium single-cup filter, and the lowest in infusions prepared by simple extraction. Other brewing methods in combination with different tool materials resulted in similar Al content. The type of brewing method significantly influences the Al content in final infusion. Aluminium content varies in infusions in relation to the method of choice, especially when using single-cup filter. Despite the fact that coffee is considered to be a poor source of Al for humans, in some cases, Al content in infusions can even reach the values reported for tea infusions.

Antimicrobial volatile substances from plants have become known as a suitable alternative to synthetic pesticides and food preservatives. The study tested the antifungal activity against Aspergillus niger of seven volatile essential oil components from plants-allyl isothiocyanate, carvacrol, cinnamaldehyde, diallyl disulfide, eugenol, thymol, and thymoquinone. To provide long-term effects by controlled release and ease of application, these substances were encapsulated into mesoporous silica material MCM-41 and then compared to the effects of pure substances. Significant antifungal activity was verified in five out of the seven tested substances. These results were correlated with the evaporation rate of pure and encapsulated substances. It has been proven that by encapsulating selected volatiles, excluding sulfur compounds, their long-term effectiveness is ensured by controlled release and easy handling, with positive effects for their antifungal activity.

Increased ingestion of aluminum (Al) can lead to its accumulation in the human body, especially in people with kidney problems. Al is also associated with several nervous diseases and its negative influence on embryo development during pregnancy has been proven in animal models. Hibiscus sabdariffa L. petals are widely used alone or in fruit tea formulas, which are recommended for drinking during pregnancy instead of tea. Its petals can contain similar and even higher amounts of Al as tea, which is a known Al accumulator. Our research investigated whether the regular intake of H. sabdariffa infusion leads to increased burden of Al. Sixteen days of ingestion of H. sabdariffa infusion (c Al = 0.5 mg.L(-1)) led to increased but unbalanced levels (15-86 μg L(-1)) of Al in urine compared to a period when the infusion was not ingested. The highest amounts of Al excreted were observed every third day during the ingestion. Mild health problems, such as nausea and dizziness (which could be r...

Essential oil components (EOCs) are potent natural antimicrobial agents, but their high volatility and reactivity limit their potential applications. Here, we report the preparation of a series of nanomaterials containing EOCs (i.e., allyl isothiocyanate, carvacrol, cinnamaldehyde, diallyl disulphide, eugenol and thymol). The materials were prepared by simple adsorption of the EOCs onto a montmorillonite nanoclay. The antimicrobial activities of these materials were assessed against Aspergillus niger and Staphylococcus aureus as typical models of agricultural fungal pathogens and foodborne bacterial pathogens, respectively. In addition, the activities of the encapsulated EOCs were compared with those of the corresponding free forms with or without Tween-80 in two types of assays: microdilution assays for determining the minimum inhibitory concentration (MIC) and agar-based assays mimicking surface treatment. Enhanced antifungal activity of the encapsulated form was observed for all EOCs. In addition, against S. aureus, the MICs of all EOCs were remarkably lower in encapsulated form than in free form. These results indicate that EOCs encapsulated in low-cost nanoclays have favourable potential as antimicrobials compared with the pure compounds.

The vapor phase of some essential oils proved to have antimicrobial activity. Utilization of the vapor phase of Eos is presently understood as one of the possible alternatives to synthetic food preservatives which could be used in the future. However, testing the vapor phase of EOs against microorganisms causing food-borne diseases (e.g. Salmonella enteritidis or Staphylococcus aureus) or food spoilage is relatively new. Consequently, due to the large number of known EOs, research on their antimicrobial activity is still largely in the phase of in vitro rather than in vivo testing. Moreover, no standard and reliable method for fast screening of a wide range of samples exists. Thus, the aim of this study is to show results concerning tests of the antimicrobial activity of EOs against S. enteritidis or S. aureus, which were conducted by two modifications of the disc volatilization method we developed. The lately developed method has the potential to become widely used for fast screeni...

republic; b department of chemistry of Natural compounds, university of chemistry and technology Prague, Prague, czech republic; c department of crop sciences and agroforestry, czech university of life sciences Prague, Prague, czech republic; d students for the living amazon o.p.s.,

Infections caused by Staphylococcus aureus are a serious global threat, and with the emergence of antibiotic resistance, even more difficult to treat. One of the possible complications in antistaphylococcal therapy represents negative interactions of antibiotics with food. In this study, the in vitro interaction between oxacillin and crude palm seed oil from Astrocaryum vulgare, Cocos nucifera, and Elaeis guineensis against nine strains of S. aureus was determined using the checkerboard method. Lauric acid was identified as a major constituent of all tested oils by gas chromatography. The results showed strong concentration dependent antagonistic interactions between palm oils and oxacillin with values of fractional inhibitory concentrations indices ranging from 4.02 to 8.56 at concentrations equal or higher than 1024 µg/mL of the tested oils. Similarly, lauric acid in combination with oxacillin produced antagonistic action with fractional inhibitory concentration indices ranging fr...

Currently, the negative effects of unified and intensive agriculture are of growing concern. To mitigate them, the possibilities of using local but nowadays underused crop for food production should be more thoroughly investigated and promoted. The soybean is the major crop cultivated for vegetable oil production in Zambia, while the oil production from local oil-bearing plants is neglected. The chemical composition of oils and cakes of a three traditional oil plant used by descendants of the Lozi people for cooking were investigated. Parinari curatellifolia and Schinziophyton rautanenii oils were chiefly composed of α-eleostearic (28.58–55.96%), linoleic (9.78–40.18%), and oleic acid (15.26–24.07%), whereas Ochna serrulata contained mainly palmitic (35.62–37.31%), oleic (37.31–46.80%), and linoleic acid (10.61–18.66%); the oil yield was high (39–71%). S. rautanenii and O. serrulata oils were rich in γ-tocopherol (3236.18 μg/g, 361.11 μg/g, respectively). The O. serrulata oil also h...

Essential oil components (EOCs) such as eugenol play a significant role in plant antimicrobial defense. Due to the volatility and general reactivity of these molecules, plants have evolved smart systems for their storage and release, which are key prerequisites for their efficient use. In this study, biomimetic systems for the controlled release of eugenol, inspired by natural plant defense mechanisms, were prepared and their antifungal activity is described. Delivery and antifungal studies of mesoporous silica nanoparticles (MSN) loaded with eugenol and capped with different saccharide gates—starch, maltodextrin, maltose and glucose—against fungus Aspergillus niger—were performed. The maltodextrin- and maltose-capped systems show very low eugenol release in the absence of the fungus Aspergillus niger but high cargo delivery in its presence. The anchored saccharides are degraded by exogenous enzymes, resulting in eugenol release and efficient inhibition of fungal growth.

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