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Antioxidant and antibacterial activity of tea and mate extracts
(Estonian University of Life Sciences, 2026) Meremäe, Kadrin; Raudsepp, Piret; Rusalepp, Linda; Roasto, Mati
Consumers are increasingly interested in natural, plant-based additives as alternatives to synthetic compounds in food products. This study investigated the polyphenolic profiles, total polyphenol content (TPC), total antioxidant capacity (TAC), and antibacterial activity of aqueous and 30% ethanolic extracts of green tea, matcha tea, black tea, and yerba mate. Commercial teas (Camellia sinensis) and mate (Ilex paraguariensis) were purchased in Tartu, Estonia. The tea and mate leaves were powdered (< 1 mm), and extracts prepared with water or 30% ethanol. Polyphenolic compounds were analysed using HPLC-DAD-MS, TPC was quantified as gallic acid equivalents, and TAC was determined spectrophotometrically using the Folin-Ciocalteu method. Minimum inhibitory concentrations (MICs) against Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Campylobacter jejuni were determined by broth microdilution according to the EVS-EN ISO, 20776–1:2020 standard. In total, 28 polyphenolic compounds were detected, including hydroxybenzoic acids, hydroxycinnamic acids, flavanols, flavonols, and tea pigments. Mate extracts were rich in chlorogenic acids, while tea extracts contained higher proportions of flavanols, particularly epigallocatechin, epicatechin gallate, and epigallocatechin gallate. Ethanolic extracts of mate (5.16 ± 0.02 mg GAE/mL) and green tea (4.68 ± 0.08 mg GAE/mL) had the highest TPC, wheras matcha tea (5.50 ± 0.01 mg GAE/mL) and green tea (5.82 ± 0.00 mg GAE/mL) showed the strongest TAC. In aqueous extracts, mate and green tea had the highest TPC (3.02 ± 0.34 and 1.77 ± 0.03 mg GAE/mL, respectively), and the strongest TAC (4.05 ± 0.01 and 3.48 ± 0.10 mg GAE/mL). All extracts inhibited the growth of S. aureus, with MIC values ranging from 0.06 to 0.27 mg GAE/mL, and green tea extracts showed the strongest antibacterial activity. Mate extracts showed similar TAC and antibacterial activity in both aqueous and ethanolic extracts. TAC correlated most strongly with TPC (rS = 0.8), and among individual compounds, epicatechin gallate showed the strongest correlation (rS = 0.6). A moderate negative correlation (rS = − 0.6) between TPC and MICs indicated that higher polyphenolic content was linked to stronger antibacterial activity. In summary, ethanolic extracts of green tea were the most promising for further application in food composition due to their strong antioxidant and antibacterial properties. These findings highlight the potential of tea and mate extracts as natural alternatives to synthetic additives in the food industry.
Do phospholipolysis and bacteria primarily regulate linoleic acid oxidation in fresh meats?
(Estonian University of Life Sciences, 2026) Püssa, Tõnu; Rusalepp, Linda; Meremäe, Kadrin; Sünter, Alar; Raudsepp, Piret; Mäesaar, Mihkel; Anton, Dea; Elias, Terje
The release of polyunsaturated fatty acids (PUFA) from cell membranes by phospholipolysis followed by (per)oxidation, is the major integrated process in the oxidative spoilage of meat. Only free PUFAs are susceptible to oxidation. Rancid meat is an excellent medium for the growth of various microbes, which in turn contribute to the release and oxidation of new PUFA molecules. Due to dominance of linoleic acid (LA) among PUFAs, its oxidation of is the most important in meats. This study is the first attempt to quantitatively describe the oxidation of LA from start to finish, specifically to the toxic secondary oxidation product malondialdehyde (MDA). Oxidation begins after the release of LA from cell membrane phosphatidylcholines (PL), during which lysophosphatidylcholines (LPC) are formed under the catalysis of lipolytic phospholipases A (PLA 1 and 2) (EC 3.1.14). Process continues with combined sequential enzymatic and free-radical formation primary oxidation products called oxylipins (OL), and ends with the formation of secondary oxidation products, mostly various aldehydes, including MDA, which is toxic and mutagenic especially for bacteria. The two main enzymatic routes involved in LA oxidation are lipoxygenase (LOX) and cytochrome P450 oxidase (CYP450) pathways. Experimental. The lipolytic and oxidative processes in minced porcine, bovine, rainbow trout, and chicken meats were modified by six natural additives (powders of apple, black currant, aronia, tomato, garlic, and garden rhubarb (all 2% w/w)). During the 14-day storage at refrigerator temperature, the concentrations of LPCs 1 and 2 and MDA were determined periodically by LC-Q-ToF-MS and HPLC-DAD, respectively. Total counts of aerobic microorganisms and Pseudomonas spp. were estimated using ISO methods. Results. There is no clear correlation between concentration of MDA (or OLs) and LPC, but a zigzag temporal pattern exists that generally reflects the two main (lag- and log-) phases of the growth of aerobic microorganisms and Pseudomonas spp. During the first 1–4(6) days, the content of LPCs and MDA is positively correlated due to the autooxidation of LA. Mostly between days 6–8, the LPC content drops, whereas the production of OLs and MDA continues. The reserve of LPCs from autooxidation is obviously depleted around the 8th day. However, here the log phase of microbial growth starts, providing a fresh supply of LA and other PUFAs. The rapid increase in the content of LPCs and MDA after the 8th day is especially distinct in meat with tomato powder. Plant additives modulate the process by either accelerating or slowing down different phases. The described pattern is best visible in porcine meat, less so in beef and not at all in trout and chicken meats due to the low level of free LA throughout the whole oxidation process. Conclusion: In order to purposefully extend the shelf life of minced meats, in addition to the antibacterial and antioxidant (mostly radical scavenging) effects, the antilipolytic effects of additives should also be taken into account. The research in this topic is ongoing.
10-hydroxystearic acid as a potential quantifiable marker of bacterial contamination in meats
(Estonian University of Life Sciences, 2026) Püssa, Tõnu; Rusalepp, Linda; Meremäe, Kadrin; Sünter, Alar; Raudsepp, Piret; Mäesaar, Mihkel; Anton, Dea; Roasto, Mati
10-hydroxystearic acid (10-HSA) is the major oxygenated derivative of oleic (cis-9-octadecenoic) acid, a monounsaturated n-9 fatty acid (MUFA). The corresponding metabolic reaction, which can be classified as both oxidation and hydration (addition of a water molecule to an isolated double bond), is mainly catalyzed by oleate hydratase (OhyA), a member of flavoenzyme family, These enzymes, classified as hydro-lyases (EC 4.2.1.53) are of interest for industrial applications due to their role in the generation of hydroxy fatty acids, which are used in surfactants, lubricants, and biodegradable polymers. 10-HSA, which can be further oxidized to 10-ketostearic (10- KSA) and 9,10-epoxystearic (9,10-ESA) acids, is produced only by bacteria, such as ruminant species (Selenomonas ruminantum, Enterococcus faecalis, etc) or multiple other bacteria (Staphylococcus, Bacillus, Listeria,, Pseudomonas) that live in various contaminated fresh meats (Radka et al, 2021). Porcine and trout meat do not naturally contain 10-HSA, but beef may contain 10-HSA, which is deposited from the rumen to meat and milk. The corresponding OhyA is not found in ruminant meat. The gene encoding OhyA is found in different bacteria and is involved in processes such as surviving stress, modulating membrane composition, etc. However, Pseudomonas aeruginosa that lacks OhyA, is using other enzyme systems, for example lipoxygenase (LoxA) (Morello et al, 2019). There are multiple chemical and biochemical markers of bacterial levels and activities in meat – pH, enzyme activities (such as of catalase or coagulase), metabolic end products (such as hydrogen sulfide, indole, ammonia, volatile organic compounds (VOC) like histamine). Total volatile basic nitrogen (TVB-N) is another quantifiable indicator of bacterial spoilage. The knowledge that 10-HSA is synthesized only by bacteria inspired us to investigate the utility of this oxylipin as a potential biochemical marker for assessing the level of bacterial contamination in meats. We investigated the formation of 10-HSA in minced porcine, bovine, and rainbow trout meat for 8 or 11 days at refrigerator temperatures by LC-MS/ToF and correlated the results with the CFU/g values obtained by enumeration of total microbial counts of mesophilic aerobic microorganisms and separately of Pseudomonas spp by ISO methods. Results: 10-HSA has a common linear positive correlation with bacterial counts for all three studied meats with R2 = 0.96 between 1 and 8 or 11 days. This phenomenon suggests the presence of various bacteria that may have slightly different slopes of the linear regression, the resulting correlation is a combination of these primary correlations. For Pseudomonas spp, there are separate positive linear correlations for all three meat types. Consequently, we can distinguish the meats by the slope of their regression line. Conclusion: These are the first encouraging results, but further research is needed to prove the suitability of 10-HSA as a novel marker of bacterial contamination of various meats.
The impact of storage conditions on acrylamide formation in vegetable-based products
(Estonian University of Life Sciences, 2025) Jalakas, Sirje; Roasto, Mati; Elias, Terje
The aim of this study was to identify the most commonly cultivated potato, carrot, beetroot, and pumpkin varieties in Estonia and assess acrylamide formation after storage and processing. Data collection involved queries to crop cultivation organizations, farmers, food enterprises, and Statistics Estonia. This resulted a ranking of the most cultivated varieties in Estonia. Selected vegetables were stored at 3 °C and 8 °C for six months, followed by heat treatment to produce vegetable crisps and purees. For vegetable crisps, vegetable slices were fried at 175 ºC for 5 minutes, while purees were prepared using a food processor and autoclaved at 120 ºC for 30 minutes. Acrylamide analysis was performed at the Health Board Tartu Laboratory using an accredited LCMS/ MS method. Sample extraction was conducted using the QuEChERS method. The acrylamide detection and quantification limits (LOD 10–17 μg/kg, LOQ 30–50 μg/kg) were determined based on the food matrix, with an expanded uncertainty of 20%. The results showed that acrylamide levels varied significantly depending on the vegetable variety and processing method. Fried potato products made from varietis with lower reducing sugar content remained below the EU benchmark values, while those with higher reducing sugar content exceeded these values. In potato chips, acrylamide levels exceeded the benchmark regardless of the reducing sugar content. Among vegetable-based crisps, the highest acrylamide levels were detected in carrot crisps, followed by highsugar potato crisps. For purees, the lowest acrylamide concentration was found in a puree made from the pumpkin variety Gold Medal, where levels were below the quantification limit. In contrast, purees made from the Big Mac pumpkin variety and other vegetable purees exceeded the EU reference values (40 μg/kg) for baby food. We found that storage conditions significantly influenced acrylamide formation. Potatoes stored at 3 °C accumulated higher reducing sugar levels, leading to increased acrylamide formation during heat processing. For example, after six months of storage, potato puree from the Birgit variety contained 686 μg/kg acrylamide when stored at 3 °C, compared to 221 μg/kg when stored at 8 °C. A similar trend was observed in the potato Laura variety, where reducing sugar content was 1.5 times higher in potatoes stored at 3 °C compared to 8 °C, resulting in a 1.4 times higher acrylamide level in the processed puree. High increase in acrylamide content was seen for carrots stored at 8 °C, which led to increased reducing sugars and increased acrylamide formation, particularly in the Berlin variety (1354 μg/kg). These findings emphasize the importance of selecting suitable storage temperatures and vegetable varieties to minimize acrylamide formation in processed products, especially for vegetable based infant foods.
Microbial growth inhibition by the use of selected plant powders in minced meat
(Estonian University of Life Sciences, 2025) Roasto, Mati; Meremäe, Kadrin; Mäesaar, Mihkel; Elias, Terje; Anton, Dea; Raudsepp, Piret; Rusalepp, Linda
This study aimed to evaluate the microbial growth inhibition effect of plant powders in minced pork and beef. Additionally, polyphenolic profiles of the plant powders were determined. Pomace powders of berries of blackcurrant, chokeberry, rowan and tomato were used. Additionally the powders of petioles of rhubarb, bulbs of garlic and apples were used. Apple powders were whole apples and apples without seeds. Plant material was dried at 50 °C, then the dried material was milled into a fine powder using a grinder and finally sieved to obtain a fraction of ≤1 mm. The plant powder was added at 2% (w/w) of the minced meat. Fresh minced pork with 28% fat content and minced beef with 18% fat content were used. The minced meats were purchased from a large-scale Estonian meat industry. The total phenolic content of the plant powder extracts in 60% aqueous ethanol was measured spectrophotometrically using the Folin–Ciocalteu method. Two percent of plant powders were added to the minced meats, and a mixer was used to ensure the plant powders were thoroughly incorporated. Pure minced meat was used as the control. The samples were packed in sterile screw-top cups and stored in the refrigerator at 4 ± 2 °C. All analyses were performed in duplicate on days 1, 4, 6, and 8, with additional analyses on days 11 and 14 for the rhubarb samples, which exhibited strong inhibition of microbial growth. Enumeration of aerobic mesophilic microorganisms, yeasts and moulds and presumptive Pseudomonas spp. was performed according to the ISO standards. At all time points, an estimation of pH and water activity was performed. We found that rhubarb powder in minced meat reduced the average total microbial counts by 10-fold, and the counts of Pseudomonas spp., yeasts, and molds by 100-fold compared to the control. Also, samples containing powders, such as blackcurrant, garlic, tomato and chokeberry showed lower total microbial counts than the controls. The low microbial growth inhibition effect was found for rowan berry pomace and apple powders in minced meat. Apart from organic acids, 27 distinct polyphenolic compounds from the classes of anthocyanins, dihydrochalcones, flavanols, flavonols, and hydroxycinnamic acids were tentatively identified in the plant powders. The highest number of polyphenolic compounds (n = 20), were found in blackcurrant, chokeberry and rowan berry powders, followed by rhubarb powder, which contained 16 different compounds. In the present study, rich composition of polyphenols was found in blackcurrant, which also showed good inhibition of microbial growth in enriched minced pork and beef samples. The lower pH and the presence of organic acids in samples can explain the best microbial growth inhibition effect of rhubarb powder. We suggest that plant powders with a rich composition of polyphenols can be applied for the valorization of different foods, both animal and plant-based food products.
Assessment of meat quality (freshness) with a simple device based on the contents of ATP breakdown products. The effect of plant materials on meat preservation
(Estonian University of Life Sciences, 2025) Sünter, Alar; Raudsepp, Piret; Püssa, Tõnu; Anton, Dea; Mäesaar, Mihkel; Rusalepp, Linda; Kuznetsov, Artur; Roasto, Mati
Plant material that could be used as a raw material for bioactive substances is usually discarded as waste from juice production. Therefore, we need knowledge about the possibilities of using residual plant material, for example, in preserving the freshness of meat during storage. The aim of the study was to evaluate the freshness retention of meats during storage in the refrigerator in the presence of various plant residues. Minced meats of chicken, pork, beef and trout were used. The plant additives were garlic (Allium sativum) bulbs, whole and seedless apples (Malus domestica); press residues of blackcurrant (Ribes nigrum) berries, chokeberries (Aronia melanocarpa), rowan berries (Sorbus sp.) tomatoes (Solanum lycopersicum), and rhubarb petioles (Rheum). The plant materials were dried at 50 °C and ground into a fine powder. The amount of powder mixed into the minced meats was 2%. The experiment lasted 14 days in a refrigerator at 4 °C. Samples were taken daily to analyze the freshness of the meat. One of the best ways to assess meat quality is to monitor the change in the breakdown products of adenosine triphosphate from adenosine triphosphate (ATP) > adenosine diphosphate (ADP) > adenosine monophosphate (AMP) > inosine monophosphate (IMP) > inosine (Ino) > hypoxanthine (Hx) > xanthine > uric acid. In AS Ldiamon, a cheap and simple device was developed to estimate the concentration of ATP and its breakdown products in meat samples. The operation of this instrument is based on well-known gel filtration principle, where the movement of smaller molecules (ATP degradation products) slows down during the run through the column. This device allows measuring the relative amounts of products that increase duringstorage. To correlate our results with information published, HPLC (Agilent 1100 series liquid chromatograph) was used as a second step to estimate the inosine monophosphate (IMP), inosine (Ino) and hypoxanthine (Hx) content of the samples. Fractions obtained by gel filtration, containing compounds below 5 kDa were stored at -20°C until further HPLC analyses. Best plant additives to keep meat freshness were press residues of tomato, blackcurrant and rhubarb. Both apples and garlic were less effective.
Polyphenolic content, antibacterial and antioxidative properties of some berries and their influence on inosine monophosphate formation in minced pork
(Università degli Studi di Milano Statale, 2024) Sünter, Alar; Meremäe, Kadrin; Rusalepp, Linda; Roasto, Mati; Anton, Dea; Püssa, Tõnu; Kuznetsov, Artur; Raudsepp, Piret
Introduction: Total polyphenol content (TPC), antibacterial and antioxidative properties [1] of chokeberry, blackcurrant, and rowan berries and their press residues were alnalysed together with meat taste enhancing inosine monophosphate (IMP) formation [2] during 14 days of storage of the minced pork, enriched with these berry powders.
Growth dynamics of microorganisms in rainbow trout marinated with fruit and berry pomaces
(Estonian University of Life Sciences, 2024) Roasto, Mati; Mäesaar, Mihkel; Anton, Dea; Rätsep, Reelika; Elias, Terje; Meremäe, Kadrin
In recent years, there has been an increasing trend in food technology to increase the use of various plant-origin materials including fruit, and berry pomaces, a by-products of juice production, in the composition of food of animal origin. This is mainly because of potential health benefits of plant derived bioactive components to human health. Also, this is in good agreement with the principles of the circular bioeconomy. The use of berry pomaces reduce the food waste and provides added value to the final products. The aim of the study was to evaluate the effect of apple, black currant, rhubarb or tomato pomace aqueous extracts containing marinades on the growth dynamics of microorganisms in raw rainbow trout within the determined study period. Fresh rainbow trout (Oncorhynchus mykiss) fillets were purchased from a local fish farm. The pomaces were obtained after juicing of the apples (Malus domestica Borkh.), black currants (Ribes nigrum L.), rhubarbs (Rheum rhaponticum L.) and tomatoes (Lycopersicon esculentum Mill.). Aqueous pomace extracts were prepared in a ratio of 1:10 (w/v), calculated for a solids content of 10%. The pomace extracts were pasteurized at 80 ºC for 20 minutes, sealed airtight in glass bottles and cooled. Finally for each pomace extract the 3% sugar, 3% salt, 1% acetic acid and 0.25% citric acid were added to obtain the marinade. Enumeration of aerobic mesophilic microorganisms, yeasts and moulds, presumptive Pseudomonas spp., and L. monocytogenes was performed according to the ISO standards. The challenge test in accordance with the technical guidance document (version 4 of 1 July 2021) of the European Union Reference Laboratory for L. monocytogenes was carried out to determine the growth potential (δ) of L. monocytogenes in marinated fish samples. It was found that in most of the samples the number of aerobic mesophilic microorganisms increased during the 22-day study period. However, interestingly in all samples, there was a decrease in the number of Pseudomonas spp. from 3.42 log10 cfu/g to 1.00 log10 cfu/g. Also, the numbers of moulds and yeasts were low in all tested samples throughout the study period remaining between 1.00 and 2.95 log10 cfu/g. The growth potential of L. monocytogenes was lower than 0.5 log10 cfu/g in all tested samples during the 15-day challenge period, which means that the marinated product did not support the growth of L. monocytogenes. Comparing the results of initial and final numbers of L. monocytogenes, a tenfold decrease in the average counts of the pathogen was counted in the black currant pomace, followed by the apple pomace and rhubarb pomace fish samples. Within the entire study period, the lowest average numbers of L. monocytogenes were observed in the black currant pomace containing fish samples compared to the control. On the final day of the durability study, day 15, the lowest growth potential of L. monocytogenes was found for black currant pomace and apple pomace containing marinated fish samples. The use of apple, black currant, rhubarb and tomato pomaces in marinades can ensure a sufficiently long and microbiologically safe shelf-life for the marinated raw rainbow trout products.
Furan content in commercial baby foods produced in Estonia
(Estonian University of Life Sciences, 2024) Jalakas, Sirje; Mäkelä, Susanna H. M.; Roasto, Mati; Elias, Terje
The aim of this study was to analyse the Estonian surveillance data on furan content in baby food. Organic baby food pouches were collected under surveillance program of the Agriculture and Food Board in 2021 and 2022. Baby foods were collected from Estonian retail markets. Materials included eighteen commercial organic baby food pouches samples from 2021 and twenty samples from year 2022. Products were categorized to the following groups: vegetable-based baby foods, vegetable-meat based baby foods and fruits-based baby foods. Analyses were performed in Eurofins WEJ Contaminants GmbH laboratory, in Germany. The determination of furan in foodstuffs was done by gas chromatographic headspace analysis (headspace GC/MS) according to JCFU4, CON-PV 00572 (2021-03) HS-GC-MS method. Quantification limit was 5 μg kg-1. Furan contents of baby foods of various compositions were different. In 2021 and 2022, a total of 38 infant food samples were analysed for furan content. The majority of samples analysed were fruit-based infant foods (n = 27), with fewer vegetable-based samples (n = 3) and vegetable meat based food samples (n = 8). The highest average furan levels were found in vegetable meat-based infant foods (120 μg kg-1). In contrast, fruit-based infant foods had an average furan level of 7.40 μg kg-1. From the category of fruit-based foods, the highest furan content was detected in Lingonberry-blueberry-rye porridge. In these products the furan content was 17 and 25 μg kg-1, respectively. The main components added to cereal-based infant foods were fruits, but since cereal-based ingredients were also added, their furan content was slightly higher than that of purely fruit-based infant foods. Difference was found between fruit- and vegetable-based baby food groups. Vegetable-based infant foods had an average furan level of 43 μg kg-1. All fruit-based samples contained similar amount of furan (SD ± 4.6). Both vegetable-based and vegetable-meat-based groups had high dispersion between the data indicating that they contain furan in very different amounts (SD ± 36.81 and ± 67.78). Based on the results of statistical comparison between studied food groups, it can be concluded that there was significant difference (P < 0.05) between the furan content of each baby food group. The highest median was in the vegetable-meat-based group and the least was in the fruit-based group. Vegetable-based foods usually require higher temperatures and/or longer cooking times, which potentially increases the furan formation. Vegetable- and vegetable-meat-based food groups contained higher amounts of furan compared to fruit-based food groups. The furan content of these three food groups were compared and a significant difference was found. In this study, the highest furan content was in the vegetable-meat-based food group. Furan formation in baby foods is a significant safety concern and strategies to reduce the formation of furan should be addressed.
Relationships between the effects of plant additives on linoleic acid oxidation and microbial growth in minced pork
(Estonian University of Life Sciences, 2024) Püssa, Tõnu; Rusalepp, Linda; Meremäe, Kadrin; Anton, Dea; Raudsepp, Piret; Roasto, Mati
Peroxidation of polyunsaturated fatty acids (PUFA), especially unconjugated linoleic (9,12- octadecadienoic) acid and microbial degradation of various constituents are the main integrated processes of spoilage of muscle foods. Peroxidation of linoleic acid in meat occurs through the combination of enzymatic and free radical mechanisms, the most important oxidation enzymes being lipoxygenase (LOX) and cytochrome oxidase P450 (CYP450). The aim of this study was to describe the relationship between these two processes in minced pork in the presence of nine plant-derived additives. Powders of freeze-dried apple (Malus domestica), also without seeds, blackcurrant (Ribes nigrum), rhubarb (Rheum rhaponticum), tomato (Lycopersicon esculentum), chokeberry (Aronia melanocarpa), garlic (Allium sativum), and rowan berries (Sorbus aucuparia) were mixed with fresh minced pork (2% w/w) and stored at 6 °C during 8 or 14 days. Samples were taken at days 1, 4, 6, 8 and additionally at days 11 and 14 for rhubarb. Enumeration of aerobic mesophilic microorganisms, yeasts and moulds, and presumptive Pseudomonas spp. was performed according to the ISO standards. The main primary oxidation products of linoleic acid (oxylipins) were quantified by LC-MS performed on a 1290 Infinity system liquid chromatograph coupled to 6450 Q-ToF mass spectrometer (Agilent Technologies, Germany). Concentration of malondialdehyde (MDA) as a main secondary oxidation product of linoleic acid was estimated using 2-thiobarbituric acid reactive substances (TBARS) method on an Agilent 1100 series LC-UV/Vis chromatograph. All additives inhibited the growth of tested microorganisms compared to meat, but to different extents. Blackcurrant (BC) powder had both high antioxidant and antimicrobial activity. The antioxidant activity of BC is mainly due to the free radical scavenging and LOX inhibiting effect of polyphenols of the anthocyanin group, there are various hypotheses about the mechanisms of the BC`s strong antimicrobial effect. Chokeberry (CB), with higher anthocyanins content, showed lowest MDA value, but had lower antimicrobial activity than BC. Rowan berries, which contained less anthocyanins than CB or BC, also had lower antioxidant capacity, but moderate antimicrobial activity. Garlic and rhubarb had by far the lowest antioxidant activity, showing the highest values of both MDA and total oxylipins already at days 4 and 6, respectively. However, these additives were most effective in inhibiting microbial growth that could be caused by MDA and oxylipins. According to the literature, MDA is also synthesized by the corresponding bacterial enzymes. As an efficient cross-linker of macromolecules such as DNA, MDA is particularly toxic to microorganisms. Removal of seeds significantly reduced the antibacterial and antifungal activity of apples, while maintaining high antioxidant capacity. Apparently, seedspecific substances such as furocoumarins or phloretin, which have no antioxidant effect, are responsible for the antimicrobial effect of apples. Seedless tomato significantly inhibited linoleic acid oxidation, while like seedless apple, was relatively powerless against microorganisms. Considering both antioxidant and antimicrobial effects, it is difficult to achieve reasonable extension of the shelf life of minced pork when combined with a single plant.
Minimal inhibitory concentrations, polyphenolic prophile and antioxidative properties of the extracts of selected berries and their pomaces
(Estonian University of Life Sciences, 2024) Raudsepp, Piret; Meremäe, Kadrin; Rusalepp, Linda; Roasto, Mati
The aim of the study was to establish minimal inhibitory concentrations (MIC) of the aqueous vs 30% aqueous ethanolic extracts of Aronia melanocarpa (Michx.) Elliott i.e. chokeberry (CB), Ribes nigrum L. i.e. blackcurrant (BC), and Sorbus aucuparia L. i.e. rowan berries (RB) and the corresponding pomaces (+P) against bacterial species L. monocytogenes, S. aureus, E. coli, and C. jejuni. Polyphenolic prophile and antioxidative properties of the extracts were also determined. Aqueous extracts and 30% aqueous ethanolic extracts were prepared of the powders of dried berries and corresponding pomaces in the ratio 1:20 (w/v). The extracts were chromatographically analyzed using a 1290 Infinity system (Agilent Technologies, Germany), coupled to an Agilent 6450 Q-TOF mass spectrometer equipped with a Jetstream ESI source and to an Agilent 1290 Infinity Diode Array Detector. The minimal inhibitory concentration (MIC) values of the extracts were determined against tested bacteria by the broth microdilution method in 96-well microplates, according to the EVS-EN ISO 20776- 1:2020 guidelines. Analyses of antioxidative properties (AO) of plant extracts were performed using the DPPH free-radical-scavenging method on an Infinite 200 Pro M Plex plate reader instrument (Tecan Austria Gmbh, Austria). The total content of polyphenols (TCP) was significantly (P < 0.05) higher in the ethanolic extracts than in the aqueous extracts. The TCP of plant extracts was in descending order as follows: CB > CBP > BC > BCP > RB > RBP in etahnolic, whereas in aqueous extracts the order was different: CB > BC > CBP > RB > BCP > RBP. The berry pomaces contained 60 – 70% of the polyphenols of the corresponding berries. The sensitivity of tested bacteria to the extracts of berries and berry pomaces starting from the most sensitive bacteria was as follows: S. aureus > L. monocytogenes > E. coli ≈ C. jejuni. No correlation was established between TCP and antibacterial (AB) properties of the plant extracts. The antioxidative properties in extracts with both solvents from highest to lowest were as follows: CB > CBP > BC > BCP ≈ RB > RBP. The AO properties were significantly (P < 0.05) higher in the ethanolic extracts than in the aqueous extracts. TCP correlated strongly positively with AO, both in aqueous (r = 0.92) and in 30% ethanolic extracts (r = 0.93). The extracts of CB and BC berries and berry pomaces had higher TCP, they also had better AB and AO properties compared to RB and its pomace. Among studied plant extracts TCP did not correlate with MIC values, indicating that other compounds besides polyphenols e.g. organic acids can cause the AB effect in the studied plant extracts. As berry pomaces, left over from juice pressing contain 60 – 70% of the TCP of corresponding berries, they should be further used as a source of beneficial compounds and not discarded as waste.
Sensory properties of rainbow trout in marinade with apple, black currant, rhubarb and tomato pomaces
(Estonian University of Life Sciences, 2024) Anton, Dea; Meremäe, Kadrin; Kerner, Kristi; Tepper, Marek; Rätsep, Reelika; Püssa, Tõnu; Roasto, Mati
New product development and experiments with new flavours, at the same time combining different plant-based materials, are preferred, but also sensory characteristics have a particular significance for consumer preference. The colour and appearance of a product are noticed first and are very important to determine the purchase decision of the customer. The aim of the study was to evaluate the effect of the used fruit and berry pomaces on the sensory quality of marinated rainbow trout. The fresh rainbow trout (Oncorhynchus mykiss) fillets originating from Estonian fish farm were cut into 2 x 4 cm pieces with equal thickness. Marinating process was performed at temperature 6 ±1°C in plastic boxes covered with lids, with fish and marinade solution ratio 1:1. The marinade contained pasteurized aqueous extracts of the apple, black currant, rhubarb or tomato pomace, sugar (3%), salt (3%), acetic and citric acid (1% and 0.25%, respectively). The control marinade solution consisted of water instead of pomace aqueous extract. Twelve assessors assessed the sensory properties rating the samples for the appearance of the marinade, appearance of the flesh, odour, flavour, aftertaste, texture and overall acceptance on a 9-point hedonic scale (1—dislike extremely and 9—like extremely). Intensity levels of saltiness, acidity and consistency were evaluated on a 5-point Justabout- Right (JAR) scale. The appearance, colour, odour and flavour of the flesh depended on the pomaces used in the marinade. The appearance of the marinade without pomace (control), the appearance of the flesh, the odour, flavour and overall acceptance of the sample was scored with the highest points; a good taste and the soft texture were highlighted. The assessors least liked the appearance of the marinade with rhubarb and the unusual purple colour of the flesh in the marinade with black currant pomace. The lowest scores for overall acceptance were given to the samples with apple pomace due to an unusual apple taste. The apple pomace gave a strong apple odour and flavour, which some assessors considered unusual, peculiar and too sweet, while others liked it. The highest points for juiciness and aftertaste were given to the fish in the rhubarb pomace marinade. The black currant turned the fish an unusual dark purple colour, adding acidity and a peculiar sour berry flavour that the assessors found surprisingly good. The rhubarb pomace gave the marinade a pinkish colour, added acidity, made the flesh consistency quite soft and gave the product a delicate sour odour. The appearance of the marinade with tomato pomace was a bit more orange than the others. The flesh had a soft consistency, was slightly sour and had a good tomato odour and flavour that most assessors liked. The JAR results showed positive acceptance of all products. However, the JAR scores showed that the assessors were not satisfied with the consistency of the flesh in the rhubarb marinade sample. The assessors would have liked a bit more saltiness and less acidity in the samples with rhubarb and black currant pomaces. In the case of consistence, the results differed among the marinades being most of the cases close to “just about right”. The sensory properties of the marinated fish depended on the used pomaces. The sensory properties of all tested samples were acceptable. Addition of the rhubarb, tomato and black currant pomaces affected positively the “saltiness” level being almost “just about right”. It can be concluded that adding sour pomaces to marinades could help reduce the usage of salt in the marinades.
The Impact of extracellular vesicles from commercially available milk on Staphylococcus aureus growth
(Estonian University of Life Sciences, 2024) Bhattacharya, Deep; Sapugahawatte, Dulmini Nanayakkara; Midekessa, Getnet Balcha; Kodithuwakku, Suranga; Roasto, Mati; Ekanayake, Gayandi; Fazeli, Alireza
The increasing prevalence of antibiotic resistance in Staphylococcus aureus poses a significant threat to both animal and human health. Milk, recognized for its potent antibacterial components that enhance offspring immunity, serves as a promising avenue for combating this challenge. Extracellular vesicles (EVs), which facilitate intercellular communication, offer the potential for targeted antimicrobial delivery and insights into hostpathogen interactions. With a lipid bilayer structure and encapsulation of various biomolecules including proteins, RNAs, and DNAs, EVs present a rich area for investigation. The following research aimed to isolate EVs from pasteurized and unpasteurized milk whey (industry byproduct) by Tangential Flow Filtration (TFF) system and check the effect of EVs on the growth of S. aureus ATCC 25923. The bacteria were co-cultured with milkderived EVs, namely pasteurized (P), concentrated pasteurized (CP) and unpasteurized (UP) industry whey at 1x107, 1x106, and 1x105 Colony Forming Units per millilitre (CFU/ml). Bacterial growth was tracked by measuring absorbance at 620 nm over 24 hours at 37°C. Phosphate buffer solution (PBS) with bacteria served as the negative control and all analyses were conducted in triplicate at the biological level, with each biological replicate comprising three technical replicates. The successful enrichment of EVs from various fractions of industrial whey was achieved, with their size and morphology aligning with previously reported characters of TFFderived milk EVs. Notably, these EVs exhibited the capability to impede the growth of S. aureus ATCC 25923. Although the observed inhibition of S. aureus growth was statistically insignificant (P=0.02, Sudent's t-test), confirmation using bacterial growth inhibition through CFU reduction assay is essential. This study highlights the significance of industrial whey as a vital source of EVs, providing a sustainable solution for waste repurposing with inherent antimicrobial properties. These findings highlight a promising avenue for continued exploration in this burgeoning field.
Inhibitory Effects of Chlorella vulgaris Algasomes on Listeria species Growth and Biofilm Eradication
(Serbian Society for Extracellular Vesicles, 2024) Sapugahawatte, Dulmini Nanayakkara; Godakumara, Kasun; Ekanayake, Gayandi; Bhattacharya, Deep; Midekessa, Getnet Balcha; Roasto, Mati; Bai, Renu Geetha; Kikas, Timo; Andronowska, Aneta; Fazeli, Alireza
Antimicrobial resistance is rising, diminishing the efficacy of synthetic antimicrobials. Natural alternatives, like extracellular vesicles (EVs), show promise against pathogens. This study investigates EVs from Chlorella vulgaris spent medium (algasomes) on Listeria monocytogenes, focusing on growth, biofilm formation, and eradication.
Effective suppression of Staphylococcus aureus ATCC 25923 growth through periodic dosing of pasteurized milk-derived extracellular vesicles
(Universidad de Burgos, 2024) Sapugahawtte, Dulmini Nanayakkara; Godakumara, Kasun; Mäesaar, Mihkel; Ekanayake, Gayandi; Midekessa, Getnet Balcha; Prasadini, Madhusha; Kodithuwakku, Suranga; Roasto, Mati; Andronowska, Aneta; Fazeli, Alireza
There is rising interest in extracellular vesicles (EVs) as natural antimicrobials against food spoilage and ensuring food safety. These membrane-bound particles exhibit bioactive properties, making them intriguing for scientific exploration. Our investigation outlines the antimicrobial efficacy of pasteurized cattle milk-derived EVs against Staphylococcus aureus, offering novel insights into natural antimicrobial agents for addressing microbial food quality and safety.
Plants – antioxidants or antibacterials or both in meat
(Institute of Agrifood Research and Technology, 2025) Raudsepp, Piret; Püssa, Tõnu; Sünter, Alar; Meremäe, Kadrin; Anton, Dea; Rusalepp, Linda; Mäesaar, Mihkel; Roasto, Mati
The use of plant powders as natural preservatives in the composition of meat can be an alternative to traditional products, because by adding plant materials, we can not only extend the shelf life, but also increase the content of fiber and bioactive compounds in meat products. In the present study, selected plant materials were used to test their antimicrobial and antioxidative properties in minced pork. Plant materials were powders of berry pomaces of blackcurrant, aronia, and tomato fruits, and pomace of petioles of rhubarb. Powders of garlic cloves and apples were also used.
Kõlblik kuni või Parim enne : [esitlus]
(Eesti Maaülikool, 2025) Roasto, Mati
Ettekanne teaduspraktilisel seminaril "Toidu säilimisaegade määramine ja toidu raiskamise vähendamine" Regionaal- ja Põllumajandusministeeriumis, Tallinn, 29.09.2025.
Innovative strategies utilizing extracellular vesicles from whey and algae spent media to combat biofilms of bovine mastitis pathogens
(Estonian University of Life Sciences, 2024) Sapugahawatte, Dulmini Nanayakkara; Godakumara, Kasun; Mäesaar, Mihkel; Ekanayake, Gayandi; Bhattacharya, Deep; Midekessa, Getnet Balcha; Kodithuwakku, Suranga; Roasto, Mati; Bai, Genu Geetha; Kikas, Timo; Andronowska, Aneta; Fazeli, Alireza
Bovine mastitis, a global dairy cattle disease, impacts animal health, milk quality and public health due to its zoonotic potential. Staphylococcus aureus, Streptococcus agalactiae (GBS), and Escherichia coli are the key mastitis-causing pathogens. This study examined whey and algae spent media-derived extracellular vesicles (EVs) effects on in-vitro biofilm formation.
Utilizing potato peel-derived extracellular vesicles: a new approach to combat Bacillus cereus ATCC 11778
(Estonian University of Life Sciences, 2024) Ekanayake, Gayandi; Sapugahawatte, Dulmini Nanayakkara; Godakumara, Kasun; Midekessa, Getnet Balcha; Roasto, Mati; Andronowska, Aneta; Bhat, Rajeev; Fazeli, Alireza
Extracellular vesicles (EVs) have emerged as a potent means of intercellular communication in recent years. Being membrane-bound biological nanoparticles, EVs are capable of transporting labile biochemicals between cells affecting the physiological and pathological conditions of target cells.
Antibacterial and antibiofilm activity of potato (Solanum tuberosum cv. Laura) peel-derived extracellular vesicles against Bacillus cereus ATCC 11778
(Universidad de Burgos, 2024) Ekanayake, Gayandi; Sapugahawatte, Dulmini Nanayakkara; Godakumara, Kasun; Midekessa, Getnet; Roasto, Mati; Andronowska, Aneta; Bhat, Rajeev; Fazeli, Alireza
Bacillus cereus is commonly found in many foods and known for causing foodborne illness. Due to their spore-forming and biofilm-forming nature and contamination capability these bacteria are presenting a large challenge to the food industry. The bacterium has become increasingly resistant to multiple drugs necessitating novel preventive strategies. One promising solution is the use of plant-derived extracellular vesicles (EVs), specifically from potato peels, which carry complex bioactive cargos with potential antibacterial properties. Our research explores the effectiveness of these plant-derived EVs against both planktonic phase cells and biofilms of B. cereus ATCC 11778.

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