TY - JOUR A1 - Wiegand, Cornelia A1 - Völpel, Andrea A1 - Ewald, Andrea A1 - Remesch, Markko A1 - Kuever, Jan A1 - Bauer, Janine A1 - Griesheim, Stefanie A1 - Hauser, Carolin A1 - Thielmann, Julian A1 - Tonndorf-Martini, Silke A1 - Sigusch, Bernd W. A1 - Weisser, Jürgen A1 - Wyrwa, Ralf A1 - Elsner, Peter A1 - Hipler, Uta-Christina A1 - Roth, Martin A1 - Dewald, Carolin A1 - Lüdecke-Beyer, Claudia A1 - Bossert, Jörg T1 - Critical physiological factors influencing the outcome of antimicrobial testing according to ISO 22196 / JIS Z 2801 JF - PLOS ONE N2 - Bactericidal materials gained interest in the health care sector as they are capable of preventing material surfaces from microbial colonization and subsequent spread of infections. However, commercialization of antimicrobial materials requires proof of their efficacy, which is usually done using in vitro methods. The ISO 22196 standard (Japanese test method JIS Z 2801) is a method for measuring the antibacterial activity of daily goods. As it was found reliable for testing the biocidal activity of antimicrobially active materials and surface coatings most of the laboratories participating in this study used this protocol. Therefore, a round robin test for evaluating antimicrobially active biomaterials had to be established. To our knowledge, this is the first report on inaugurating a round robin test for the ISO 22196 / JIS Z 2801. The first round of testing showed that analyses in the different laboratories yielded different results, especially for materials with intermediate antibacterial effects distinctly different efficacies were noted. Scrutinizing the protocols used by the different participants and identifying the factors influencing the test outcomes the approach was unified. Four critical factors influencing the outcome of antibacterial testing were identified in a series of experiments: (1) incubation time, (2) bacteria starting concentration, (3) physiological state of bacteria (stationary or exponential phase of growth), and (4) nutrient concentration. To our knowledge, this is the first time these parameters have been analyzed for their effect on the outcome of testing according to ISO 22196 / JIS Z 2801. In conclusion, to enable assessment of the results obtained it is necessary to evaluate these single parameters in the test protocol carefully. Furthermore, uniform and robust definitions of the terms antibacterial efficacy / activity, bacteriostatic effects, and bactericidal action need to be agreed upon to simplify communication of results and also regulate expectations regarding antimicrobial tests, outcomes, and materials. Y1 - 2018 U6 - https://doi.org/10.1371/journal.pone.0194339 SN - 1932-6203 VL - 13 IS - 3 PB - Public Library of Science (PLoS) ER - TY - JOUR A1 - Thielmann, Julian A1 - Kohnen, Stephane A1 - Hauser, Carolin T1 - Antimicrobial activity of Olea europaea Linné extracts and their applicability as natural food preservative agents JF - International Journal of Food Microbiology N2 - The antimicrobial activity of phenolic compounds from Olea (O.) europaea Linné (L.) is part of the scientific discussion regarding the use of natural plant extracts as alternative food preservative agents. Although, the basic knowledge on the antimicrobial potential of certain molecules such as oleuropein, hydroxytyrosol or elenolic acid derivatives is given, there is still little information regarding their applicability for food preservation. This might be primarily due to the lack of information regarding the full antimicrobial spectrum of the compounds, their synergisms in natural or artificial combinations and their interaction with food ingredients. The present review accumulates available literature from the past 40 years, investigating the antimicrobial activity of O. europaea L. derived extracts and compounds in vitro and in food matrices, in order to evaluate their food applicability. In summary, defined extracts from olive fruit or leaves, containing the strongest antimicrobial compounds hydroxytyrosol, oleacein or oleacanthal in considerable concentrations, appear to be suitable for food preservation. Nonetheless there is still need for consequent research on the compounds activity in food matrices, their effect on the natural microbiota of certain foods and their influence on the sensorial properties of the targeted products. KW - Antimicrobial susceptibility KW - elenolic acid KW - food preservation KW - hydroxytyrosol KW - olea europaea KW - oleuropein Y1 - 2017 U6 - https://doi.org/10.1016/j.ijfoodmicro.2017.03.019 SN - 0168-1605 VL - 251 SP - 48 EP - 66 PB - Elsevier BV CY - Amsterdam ER - TY - JOUR A1 - Hauser, Carolin A1 - Senturk Parreidt, Tugce A1 - Kowalska, U. A1 - Suminska, P. T1 - Shelf-life extension of fresh produce by edible coating JF - italian journal of food science N2 - Fresh and fresh-cut produce get a growing share on the worldwide food market as they combine the aspect of convenience food with healthy nutrition. Nevertheless, these nontreated food products bear a risk of microbial contamination with pathogenic microorganisms and have limited shelf-life due to their fresh character and big surface. Edible coatings can comply with several functions to protect those sensitive food products. In this study alginate was used as coating for fresh-cut cantaloupe melon to act as a barrier to water loss and a carrier for antimicrobial hop extracts. For mung bean sprouts chitosan, which is antimicrobial by nature, was used. Both experiments showed that edible coatings can enhance the shelf-life of these products. The edible coatings have to be designed for each produce individually. KW - alginate KW - cantaloupe melon KW - edible coating KW - fresh cut KW - hop extract Y1 - 2016 VL - 2016 IS - 28 PB - Codon Publications ET - 5 ER - TY - JOUR A1 - Kramer, B. A1 - Thielmann, J. A1 - Hickisch, A. A1 - Muranyi, P. A1 - Wunderlich, J. A1 - Hauser, Carolin T1 - Antimicrobial activity of hop extracts against foodborne pathogens for meat applications JF - Journal of Applied Microbiology N2 - Aims: The objective of this study was the fundamental investigation of the antimicrobial efficiency of various hop extracts against selected foodborne pathogens in vitro, as well as their activity against Listeria monocytogenes in a model meat marinade and on marinated pork tenderloins. Methods and results: In a first step, the minimum inhibitory concentrations (MIC) of three hop extracts containing either α- or β-acids or xanthohumol were determined against test bacteria including L. monocytogenes, Staphylococcus aureus, Salmonella enterica and Escherichia coli by a colorimetric method based on the measurement of bacterial metabolic activity. Moreover, the influence of either lactic or citric acid on the antimicrobial activity of the hop extracts was evaluated. The efficiency of hop extracts as a natural food preservative was then tested in a model meat marinade at 2 and 8°C, respectively, and finally on marinated pork. The experiments showed that Gram-positive bacteria were strongly inhibited by hop extracts containing β-acids and xanthohumol (MIC values of 6.3 and 12.5 ppm, respectively), whereas the antimicrobial activity of the investigated α-acid extract was significantly lower (MIC values of 200 ppm). Gram-negative bacteria were highly resistant against all tested hop extracts. Acidification of the test media led to a decrease of the MIC values. The inhibitory activity of the hop extracts against L. monocytogenes was strongly reduced in a fat-containing model meat marinade, but the efficiency of β-acids in this matrix could be increased by lowering pH and storage temperatures. By applying 0.5 % β-acids at pH = 5 in a model marinade, the total aerobic count of pork tenderloins was reduced up to 0.9 log10 compared with marinated pork without hop extract after 2 weeks of storage at 5°C. Conclusions: β-acid containing hop extracts have proven to possess a high antimicrobial activity against Gram-positive bacteria in vitro and in a practice-related application for food preservation. Significance and impact of the study: Antimicrobial hop extracts could be used as natural preservatives in food applications to extend the shelf life and to increase the safety of fresh products. KW - food safety KW - hop extracts KW - meat KW - natural preservative KW - pathogens KW - β-acids Y1 - 2015 U6 - https://doi.org/10.1111/jam.12717 SN - 1364-5072 VL - 118 IS - 3 SP - 648 EP - 657 PB - Oxford University Press (OUP) ER - TY - JOUR A1 - Hauser, Carolin A1 - Peñaloza, A. A1 - Rodríguez, F. A1 - Guarda, A. A1 - Galotto, M.J. T1 - Promising antimicrobial and antioxidant extracts of Murta leaves (Ugni molinae Turcz): Shelf-life extension and food safety JF - Food Packaging and Shelf Life N2 - Murta leaves are known for their beneficial effects since long time. Therefore, the aim of present study was to determine the antimicrobial and antioxidant activity of different extracts from Murta (Ugni molinae Turcz) leaves. Three extracts were obtained from Murta leaves using water or ethanol (50%, v/v) as solvents with different solid-to-solvent-ratios. The extracts were characterized in terms of their antimicrobial activity, antioxidant capacity and total polyphenol content. An extract from 1.5 g of Murta leaves obtained with 20 mL of 50% ethanol showed the highest polyphenol content with 309.4 mg gallic acid/g and the highest growth reduction of Listeria innocua (ATCC 33090), inhibiting 4.9 and 4.8 log cycles after 2 and 24 h of contact, respectively. The ethanolic extract of Murta leaves provides a natural potential antioxidant and antibacterial additive for food production. KW - murta KW - antimicrobial KW - listeria KW - antioxidant KW - polyphenols KW - natural extracts Y1 - 2014 U6 - https://doi.org/10.1016/j.fpsl.2014.01.003 SN - 2214-2894 VL - 1 IS - 1 SP - 77 EP - 85 PB - Elsevier BV CY - Amsterdam ER - TY - CHAP A1 - Hauser, Carolin A1 - Müller, Patrick A1 - Niessen, Jan T1 - Situation und Herausforderungen bei der Detektion und Qualitätssicherung in der Verarbeitung von pflanzlichen Bio Produkten T2 - Angewandte Forschung und Entwicklung für den ökologischen Landbau in Bayern ; Öko-Landbautag 2024 am 24.10.2024 N2 - Um Lebensmittelverluste gering zu halten, werden in der Lebensmittelindustrie Maßnahmen ergriffen, um Lebensmittelsicherheit und -qualität zu überwachen. Dazu werden verschiedene Detektionsmöglichkeiten verwendet. Es wurde untersucht, welche dieser Methoden angewendet werden und welche Qualitätsprobleme verbleiben, die nur schwer oder mit viel Aufwand zu detektieren sind. Zu diesem Zweck wurden quantitative Befragungen mit Industrievertretern der Bio-Branche durchgeführt. Dabei zeigte sich, dass menschliche Detektions-methoden (Sichtkontrolle, Sensorik) immer noch die größte Rolle spielen, auch wenn diese fehlerbehaftet sein können. Auftretende Qualitätsprobleme sind oft produktgruppenspezifisch, während nur schwer oder mit viel Aufwand zu detektierende Probleme Ähnlichkeiten aufweisen. Dies sind v.a. die Detektion von Mykotoxinen, Pestizidrückständen sowie Fremdkörper. Von Befragten geäußerte Wünsche zeigen noch weiteren Forschungsbedarf hinsichtlich einfach zu handhabender Detektionsmethoden. Y1 - 2024 UR - https://www.lfl.bayern.de/mam/cms07/publikationen/daten/schriftenreihe/tagungsband_oekolandbautag_2024.pdf SN - 1611-4159 IS - 5 SP - 131 EP - 135 PB - Bayerische Landesanstalt für Landwirtschaft (LfL) CY - Freising-Weihenstephan ER - TY - JOUR A1 - Senturk Parreidt, Tugce A1 - Schmid, Markus A1 - Hauser, Carolin T1 - Validation of a Novel Technique and Evaluation of the Surface Free Energy of Food JF - Foods N2 - Characterizing the physical properties of a surface is largely dependent on determining the contact angle exhibited by a liquid. Contact angles on the surfaces of rough and irregularly-shaped food samples are difficult to measure using a contact angle meter (goniometer). As a consequence, values for the surface energy and its components can be mismeasured. The aim of this work was to use a novel contact angle measurement method, namely the snake-based ImageJ program, to accurately measure the contact angles of rough and irregular shapes, such as food samples, and so enable more accurate calculation of the surface energy of food materials. In order to validate the novel technique, the contact angles of three different test liquids on four different smooth polymer films were measured using both the ImageJ software with the DropSnake plugin and the widely used contact angle meter. The distributions of the values obtained by the two methods were different. Therefore, the contact angles, surface energies, and polar and dispersive components of plastic films obtained using the ImageJ program and the Drop Shape Analyzer (DSA) were interpreted with the help of simple linear regression analysis. As case studies, the superficial characteristics of strawberry and endive salad epicarp were measured with the ImageJ program and the results were interpreted with the Drop Shape Analyzer equivalent according to our regression models. The data indicated that the ImageJ program can be successfully used for contact angle determination of rough and strongly hydrophobic surfaces, such as strawberry epicarp. However, for the special geometry of droplets on slightly hydrophobic surfaces, such as salad leaves, the program code interpolation part can be altered. KW - contact angle KW - surface energy KW - edible coating KW - image processing KW - drop shape analysis Y1 - 2017 U6 - https://doi.org/10.3390/foods6040031 SN - 2304-8158 VL - 6 IS - 4 PB - MDPI AG CY - Basel ER - TY - JOUR A1 - Maldonado, Alba A1 - Aguilar, Tomas A1 - Hauser, Carolin A1 - Wehnert, Gerd A1 - Söthje, Dominik A1 - Schlachter, Herbert A1 - Torres, Alejandra A1 - Bruna, Julio A1 - Valenzuela, Ximena A1 - Rodríguez-Mercado, Francisco T1 - Ethylene Scavenging Films Based on Ecofriendly Plastic Materials and Nano-TiO2: Preparation, Characterization, and In Vivo Evaluation JF - Polymers N2 - It is known that ethylene plays an important role in the quality characteristics of fruits, especially in storage. To avoid the deterioration of fruits caused by ethylene, titanium dioxide (TiO2) has been used due to its photocatalytic capacity. The aim of this study was to develop films based on two types of biopolymers, Mater-Bi (MB) and poly-lactic acid (PLA), with nanoparticles of TiO2 and to determine their ethylene removal capacity and its application in bananas. First, the films were fabricated through an extrusion process with two different concentrations of TiO2 (5 and 10% w/w). Then, the films were characterized by their structural (FTIR), morphological (SEM), thermal (DSC and TGA), dynamic (DMA), barrier, and mechanical properties. The ethylene removal capacities of the samples were determined via gas chromatography and an in vivo study was also conducted with bananas for 10 days of storage. Regarding the characterization of the films, it was possible to determine that there was a higher interaction between PLA with nano-TiO2 than MB; moreover, TiO2 does not agglomerate and has a larger contact surface in PLA films. Because of this, a higher ethylene removal was also shown by PLA, especially with 5% TiO2. The in vivo study also showed that the 5% TiO2 films maintained their quality characteristics during the days in storage. For these reasons, it is possible to conclude that the films have the capacity to remove ethylene. Therefore, the development of TiO2 films is an excellent alternative for the preservation of fresh fruits. KW - ethylene removers; titanium dioxide; eco-friendly films; shelf life Y1 - 2024 U6 - https://doi.org/10.3390/polym16060853 SN - 2073-4360 VL - 16 IS - 6 PB - MDPI AG ER - TY - JOUR A1 - Maldonado, Alba A1 - Cheuquepan, Paulina A1 - Gutiérrez, Sofía A1 - Gallegos, Nayareth A1 - Donoso, Makarena A1 - Hauser, Carolin A1 - Arrieta, Marina P. A1 - Torres, Alejandra A1 - Bruna, Julio A1 - Valenzuela, Ximena A1 - Guarda, Abel A1 - Galotto, María A1 - Rodríguez-Mercado, Francisco T1 - Study of Ethylene-Removing Materials Based on Eco-Friendly Composites with Nano-TiO2 JF - Polymers N2 - Ethylene is a phytohormone that is responsible of fruit and vegetable ripening. TiO2 has been studied as a possible solution to slowing down unwanted ripening processes, due to its photocatalytic capacity which enables it to remove ethylene. Thus, the objective of this study was to develop nanocomposites based on two types of eco-friendly materials: Mater-Bi® (MB) and poly(lactic acid) (PLA) combined with nano-TiO2 for ethylene removal and to determine their ethylene-removal capacity. First, a physical–chemical characterization of nano-TiO2 of different particle sizes (15, 21, 40 and 100 nm) was done through structural and morphological analysis (DRX, FTIR and TEM). Then, its photocatalytic activity and the ethylene-removal capacity were determined, evaluating the effects of time and the type of light irradiation. With respect to the analysis of TiO2 nanoparticles, the whole samples had an anatase structure. According to the photocatalytic activity, nanoparticles of 21 nm showed the highest activity against ethylene (~73%). The results also showed significant differences in ethylene-removal activity when comparing particle size and type and radiation time. Thus, 21 nm nano-TiO2 was used to produce nanocomposites through the melt-extrusion process to simulate industrial processing conditions. With respect to the nanocomposites’ ethylene-removing properties, there were significant differences between TiO2 concentrations, with samples with 5% of active showed the highest activity (~57%). The results obtained are promising and new studies are needed to focus on changes in material format and the evaluation in ethylene-sensitive fruits. KW - titanium dioxide; photocatalytic activity; ethylene-removing; active packaging; nanocomposites; eco-friendly materials Y1 - 2023 U6 - https://doi.org/10.3390/polym15163369 SN - 2073-4360 VL - 15 IS - 16 PB - MDPI AG ER -