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Propolis (bee glue), a valuable biological mixture produced by European honey bees (Apis mellifera L.), is widely used as a remedy in traditional and alternative medicine, as an effective food biopreservative and as a nutritional value enhancer. The present study aimed to investigate eighty propolis samples collected from all twenty-eight districts of Bulgaria in the period of 2020–2022 in order to determine their physicochemical properties as well as their antioxidant and antimicrobial potential. The raw propolis samples exhibited brown or green colour depending on the climatic zone from which they are collected and pH values from 4.82 to 5.87, while the moisture content ranged between 0.98% and 2.97%. The total phenolics content (TPC) and total flavonoids content (TFC) varied from 63.14 mg GAE/g to 737.27 mg GAE/g, and from 29.22 mg QE/g to 234.17 mg QE/g, respectively. The propolis samples demonstrated significant antioxidant potential determined by DPPH and FRAP methods, from 18.56 mM TE/g to 1598.66 mM TE/g and from 82.28 mM TE/g to 1208.81 mM TE/g, respectively, whose values showed a positive correlation (r2) with the TPC and TFC. The results from the antimicrobial screening revealed that the methanolic propolis extracts in concentration of 20 mg/ml exhibited the highest inhibitory effect on the Gram-positive bacteria such as Micrococcus luteus 2YC-YT, Bacillus subtilis ATCC 6633, Staphylococcus aureus ATCC 25923, Listeria monocytogenes NBIMCC 8632 and Listeria innocua ATCC 33090.

The development of functional foods providing health benefits above the basic nutritional needs is of growing interest to the food industry. This research aimed to: design fresh prebiotic cheese spreads enriched with agave inulin (AI), thyme (Thymus callieri Borbás ex Velen.) and hawthorn fruit (Crataegus monogyna Jacq.) as plant sources of biologically active compounds; observe the physicochemical and microbiological changes in the cheese during storage at 4°C for 35 days; evaluate the sensory characteristics of the new functional products. Therefore, five experimental groups of fresh cheese spreads were prepared – a control; 1% AI + 0.2% thyme; 2% AI + 0.2% thyme; 1% AI + 0.4% hawthorn fruit and 2% AI + 0.4% hawthorn fruit. During the storage, pH in all experimental groups gradually decreased (reaching values between 4.17 and 4.25 on the 35th day), which corresponded to the increasing titratable acidity (reaching values from 146.30°T to 152.51°T on the 35th day). The application of thyme and hawthorn fruit did not reduce the total plate count (mesophilic aerobic and facultative anaerobic microorganisms) and yeasts; however, during the storage period the addition of agave inulin stimulated the growth of lactic acid bacteria in the treated samples compared to the control.

The current study focuses on evaluating the enzyme inhibition (acetylcholinesterase, α-amylase, α-glucosidase, pancreatin lipase), antioxidant, and antimicrobial activities of the "Modesto" apricot, "Stanley" plum, and their hybrid the "Stendesto" plum–apricot. The "Stendesto" is the only successful plum–apricot hybrid in Bulgaria. A spectrophotometric approach was used to evaluate the antioxidant activity following four complementary assays (DPPH, ABTS, FRAP, and CUPRAC). The "Stendesto" plum–apricot revealed its enhanced antioxidant potential compared to its parental lines. Apart from the free phenolics extraction, two other techniques (alkaline and acid hydrolysis) were applied to reveal the biological potential of the studied fruit. Not only free but also bound phenolic extracts were able to inhibit α-glucosidase and acetylcholinesterase, while none of the extracts inhibited lipase or α-amylase. None of the apricot extracts had antimicrobial activity, while the other fruit had limited antimicrobial activity. The proposed results undoubtedly reveal that hybrid fruits possess enhanced biological activity compared to their parents. This is a first comprehensive evaluation of hybrid fruits with reference to parental lines. This makes them an interesting research topic that should be better explored. [ABSTRACT FROM AUTHOR]

At present, there are no data in the scientific literature on studies aimed at characterizing Passiflora caerulea L. growing in Bulgaria. The present study aimed to investigate the metabolic profile and elemental composition of the leaves and pulp of this Passiflora, as well as to evaluate the antioxidant, antimicrobial and anti-inflammatory activities of its leaf and pulp extracts. The results showed that the pulp predominantly contained the essential amino acid histidine (7.81 mg g−1), while it was absent in the leaves, with the highest concentration being tryptophan (8.30 mg g−1). Of the fatty acids, palmitoleic acid predominated both in the pulp and in the leaves. A major sterol component was β-sitosterol. Fructose (7.50%) was the predominant sugar in the pulp, while for the leaves, it was glucose—1.51%. Seven elements were identified: sodium, potassium, iron, magnesium, manganese, copper and zinc. The highest concentrations of K and Mg were in the pulp (23,946 mg kg−1 and 1890 mg kg−1) and leaves (36,179 mg kg−1 and 5064 mg kg−1). According to the DPPH, FRAP and CUPRAC methods, the highest values for antioxidant activity were found in 70% ethanolic extracts of the leaves, while for the ABTS method, the highest value was found in 50% ethanolic extracts. In the pulp, for all four methods, the highest values were determined at 50% ethanolic extracts. Regarding the antibacterial activity, the 50% ethanolic leaf extracts were more effective against the Gram-positive bacteria. At the same time, the 70% ethanolic leaf extract was more effective against Gram-negative bacteria such as Salmonella enteritidis ATCC 13076. The leaf extracts exhibited higher anti-inflammatory activity than the extracts prepared from the pulp. The obtained results revealed that P. caerulea is a plant that can be successfully applied as an active ingredient in various nutritional supplements or cosmetic products. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the composition of wild Rosa canina (Kiustendil region, 2022) and cultivated rosehips Plovdiv-1 (Gotse Delchev region, 2022). The results demonstrated that the cultivated rosehips possessed more fibers and minerals, and were more abundant in polyunsaturated fatty acids. The Plovdiv-1 rosehips were characterized by lower fat content and more pronounced antioxidant properties. The wild type had higher vitamin C content. The morphological characterization indicated that the fruits of cultivated rosehips were longer, with less seeds and hairs. The results of the antimicrobial activity tests demonstrated that both methanol extracts possessed significant inhibitory activity against Micrococcus luteus 2YC-YT, moderate inhibitory effect on Bacillus subtilis ATCC 6633, Listeria monocytogenes NBIMCC 8632, Escherichia coli ATCC 25922, Proteus vulgaris ATCC 6380, Pseudomonas aeruginosa ATCC 9027, and low inhibitory activity against Bacillus amyloliquefaciens 4BCL-YT, Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 19433, Salmonella enteritidis ATCC 13076, Salmonella typhimurium NBIMCC 1672 and Klebsiella pneumoniae ATCC 13883. The extracts did not show antifungal activity, except against Rhizopus sp. and Fusarium moniliforme ATCC 38932, in which the inhibitory activity was low. The obtained results showed that cultivated rosehips are promising for supplementing various types of food products. [ABSTRACT FROM AUTHOR]

Propolis (bee glue) is a resinous substance produced by honeybees (Apis mellifera L.) from different plant sources, which possesses a wide range of biological activities, health benefits, and a great potential as a natural preservative in the foods and cosmetic products. The present study aimed to investigate the effects of propolis extracts added as biopreservatives in a cosmetic product (hand cream). For this purpose, four experimental groups were prepared - an untreated hand cream (control) and hand creams with addition of three types of 2% propolis extracts (designated as P1, P2, and P3, respectively). The samples were stored at room temperature (23 0C) and under controlled accelerated conditions (-15 0C and 42 0C) for 28 days. During the storage period, physicochemical analyses (determination of pH by potentiometric method) and microbiological analyses (determination of the total plate count, yeasts, fungi and pathogenic microorganisms by pour-plating and spread-plating methods) according to the Bulgarian State Standards were performed at 7-day intervals. The results demonstrated that the storage under different temperature conditions for 28 days did not significantly influence the physicochemical parameters and organoleptic characteristics of the hand cream with and without the addition of propolis extracts. The results from microbiological analyses showed that the addition of 2% propolis extracts significantly reduced the total plate count (mesophilic aerobic and facultative anaerobic microorganisms) in the treated samples compared to the control during the storage period. Yeasts, fungi and pathogenic microorganisms were not detected in any of the samples for the whole storage. Based on the estimates from this research, we can conclude that propolis is a biological product that can be applied as a promising natural preservative in cosmetic preparations improving their shelf life, quality and safety. [ABSTRACT FROM AUTHOR]

Pediococci are lactic acid bacteria widely used as starter cultures in the food industry, which produce lactic acid and bacteriocins (pediocins) possessing significant antilisterial potential. This research aimed to investigate the antimicrobial activity of three Pediococcus strains (Pediococcus pentosaceus, Pediococcus acidilactici and Pediococcus damnosus) against three Listeria strains (Listeria monocytogenes, Listeria innocua and Listeria ivanovii) to determine the growth characteristics and kinetic parameters during the process of co-cultivation at 37 ± 1°C. The results demonstrated that P. pentosaceus possessed a bacteriostatic effect on L. monocytogenes, but a bactericidal effect on L. innocua and L. ivanovii, and on the 60-th h no viable cells of both pathogens were detected. P. acidilactici demonstrated a strong bactericidal effect on the three Listeria strains, as L. monocytogenes was completely inhibited on the 48-th h and L. innocua and L. ivanovii were inhibited on the 60-th h of co-cultivation. In contrast, P. damnosus showed only a bacteriostatic effect on the three pathogens tested. Therefore, the strains P. pentosaceus and P. acidilactici can be successfully applied in the food industry as biopreservatives and as means to improve the food safety by inhibition of Listeria spp., which are among the most common pathogens in food products of animal origin. [ABSTRACT FROM AUTHOR]

Nowadays, the increasing consumer's demands for fresh and minimally processed foods without chemical additives attracted the research attention on some novel methods in food industry and use of natural compounds as alternative of chemical preservatives. As a unique natural product obtained from beekeeping, propolis possesses a wide range of biological activities and health benefits that can be used in food production and biopreservation. Propolis (bee glue) is a sticky resinous substance that is collected and processed by honey bees (Apis mellifera L.) from various plant sources such as flowers, leaf buds and tree exudates, and serving as a building and defensive material in their hives. This review discusses the trends in application of propolis as a safe, innovative and promising approach to quality improvement and natural preservation of different food products. The broad antimicrobial spectrum of propolis against spoilage microorganisms and foodborne pathogens offers a great variety of applications in food industry for biopreservation of meat, fish and poultry products, eggs, milk and dairy products, perishable fruits, vegetables, fruit juices and other beverages. In addition to its antimicrobial potential, the strong antioxidant properties of propolis can contribute to increase the nutritional value of the products or to retard the lipid oxidation and protein degradation of processed foods. For this purpose, propolis can be added directly to the food matrix in the form of an extract, to be applied on the surface of the product as a bioactive film or edible coating, or to be included in the composition of food biopackaging materials, thus preventing the food spoilage and enhancing the storage life of the food products. The present study on the applications of propolis in the food industry worldwide and its valuable properties reveals the potential of this natural product as a food additive, as a functional food ingredient, and as a prospective food biopreservative agent prolonging the shelf-life and improving the quality of food products. [ABSTRACT FROM AUTHOR]

Propolis is a complex honey bee product known for its antioxidant potential and antimicrobial activity, widely used as a food biopreservative and food additive. The object of the current research was to investigate the effects of carboxymethyl cellulose (CMC) edible coatings applied alone and in combination with a propolis extract on the quality parameters and storage life of fresh blueberries during refrigerated storage for 20 days. For this purpose, three experimental groups were prepared: blueberries without coating (control group), blueberries with 1%CMC coatings and blueberries with 1% CMC coatings+1% propolis extract (CMC+P). During the storage, the physicochemical and microbiological parameters of the experimental groups were evaluated. The use of CMC and CMC+P coatings reduced the weight loss by 1.13% and 1.67% in comparison with the control group on the 20-th day of storage. A significant decrease in decay percentage was found, which was in the great extent in the CMC+P coated fruit compared to the CMC coatings and the control fruit. The CMC and CMC+P edible coatings did not affect the TSS levels, the decreasing TA and increasing pH values. The application of CMC and CMC+P coatings did not cause a protective effect on the lowering values of total phenolic and anthocyanin contents in both treatments, but exhibited a positive influence on the antioxidant activity in the coated blueberries. During the entire storage period, propolis containing edible coatings (CMC+P) reduced the bacterial, yeasts and fungal counts, visibly expressed by a reduction in decay incidence in comparison with the uncoated and CMC-treated fruit. Therefore, the application of propolis in the composition of edible coatings can be considered as an effective approach for improving the postharvest quality and prolonging the storage life of fresh blueberries. [ABSTRACT FROM AUTHOR]

An important step in the development of successful technological schemes for production of yogurt and other functional foods is the selection of appropriate Lactobacillus strains with useful properties that are resistant to antibiotics and bacteriocins. In the present study eleven Lactobacillus strains were isolated from fourteen homemade Bulgarian and Italian yogurts. The isolates were identified as Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus) by 16S rDNA sequence analysis. The results from comparative 16S rRNA gene sequence-based phylogenetic analysis revealed 92-99% pairwise similarity of the isolates to the reference L. bulgaricus strains. The antimicrobial activity, antibiotic susceptibility and nisin resistance of the isolated L. bulgaricus strains were examined. Bulgarian L. bulgaricus strains 3-BG, 5-BG and 8-BG were characterized by highest antimicrobial activity against the Gram-positive bacteria Staphylococcus aureus ATCC 25923, Listeria monocytogenes NBIMCC 8632, Listeria ivanovii ATCC 19119, Listeria innocua ATCC 33090, Enterococcus faecalis ATCC 19433 and Enterococcus faecuim ATCC 19434. L. bulgaricus 8-BG was active also against the Gram-negative bacteria Pseudomonas aeruginosa ATCC 9027, Proteus vulgaris ATCC 6380, Salmonella enteritidis ATCC 13076, Salmonella abony NTCC 6017 and Escherichia coli ATCC 25922. In contrast, Italian L. bulgaricus strains demonstrated low antimicrobial activity. Bulgarian L. bulgaricus strains showed moderate sensitivity or resistance to most of the antibiotics used in the screening, while Italian L. bulgaricus strains were sensitive. Bulgarian L. bulgaricus strains 1-BG and 6-BG were resistant to 10 and 13 of a total of 24 antibiotics tested, respectively. Nisin resistance test showed that 10 of a total of 11 L. bulgaricus strains were highly sensitive to nisin (MIC values varying from 0.078 mg/mL to 0.156 mg/mL), except of Italian strain L. bulgaricus 6-IT which was resistant to nisin. [ABSTRACT FROM AUTHOR]

Bacteriocins are antimicrobial peptides of bacterial origin, which are widely used in the food industry as biopreservatives. Bacteriocins are safe, do not alter the organoleptic characteristics of food and can be applied directly in purified form or indirectly by in situ production in different food matrices. The aim of the current research was to apply a bacteriocin from Bacillus methylotrophicus strain BM47 in fresh tomato juice, and to evaluate the effects of the bacteriocin singly and in combination with pasteurization on the physicochemical and microbiological characteristics of tomato juice. To conduct the study, four experimental groups of tomato juice were prepared: non-pasteurized; non-pasteurized with a bacteriocin; pasteurized and pasteurized with a bacteriocin, which were stored under refrigeration conditions (4 °C and 75% relative humidity) for 24 days. During the storage, all experimental groups were observed for decay and fungal growth, and samples for physicochemical and microbiological analyzes were taken at 4 days interval. From the physicochemical parameters the total soluble solids (by refractrometric method), titratable acidity (by titration method), pH, organic acids (by high pressure liquid chromatographic analysis), total phenolic content (by spectrophotometric method), total chlorophylls and carotenoids content (by spectrophotometric method) and antioxidant activity (by DPPH free radical-scavenging method) were determined. From the microbiological parameters the total plate count of mesophilic aerobic and facultative anaerobic microorganisms (by colony-count technique on plate count agar at 30 °C) and the number of yeasts and fungi (by colony-count technique on chloramphenicol glucose agar at 25 °C) were determined. The results showed that pasteurized tomato juice with and without addition of a bacteriocin retained lower titratable acidity and higher levels of total soluble solids, compared to non-pasteurized groups. Throughout the storage period, pasteurized tomato juice with and without addition of a bacteriocin kept lower concentrations of citric and fumaric acids, compared to non-pasteurized samples with and without addition of a bacteriocin. The bacteriocin application and pasteurization did not affect the lowering total phenolic content, total chlorophylls and carotenoids, but helped to maintain higher values of antioxidant activity during the entire storage period. The results from the microbiological analysis demonstrated that bacteriocin treatment, especially in combination with pasteurization reduced the total plate count (bacteria) and yeasts in tomato juice. The same treatment effectively inhibited the fungal growth in both pasteurized groups, and no signs of fungal decay were observed until the end of the storage period. Therefore, the application of a bacteriocin from Bacillus methylotrophicus strain BM47 in combination with pasteurization could be considered as a promising approach for biopreservation and improvement of the storage life of fresh tomato juice. [ABSTRACT FROM AUTHOR]

Bacteriocins are biologically active compounds of proteinaceous nature synthesized by a large number of microorganisms, including members of bacterial genus Bacillus and lactic acid bacteria (LAB). The broad antimicrobial spectrum of bacteriocins against various spoilage and pathogenic microorganisms stimulated the research efforts for their investigation and potential application in different branches of food industry as natural preservatives. The promising antimicrobial activity of bacteriocins makes them suitable for application as biopreservatives and alternatives of chemical preservatives in dairy industry for production of fermented or non-fermented milk products. Therefore, the aim of the present study was to evaluate the antifungal effect of a bacteriocin isolated from Bacillus methylotrophicus strain BM47 and the possibilities for its application as a potential biopreservative of traditional Bulgarian yogurt. The results demonstrated that the addition of a purified bacteriocin in dose of 1 AU/mL of milk led to significant reduction of the fungal spores and mycelial growth of the indicator microorganism Penicillium sp. in the yogurt, without a change of its organoleptic properties, and biochemical and microbiological parameters during the 4-week period of storage. [ABSTRACT FROM AUTHOR]

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Antibacterial and antifungal activities are characteristic features of many representatives of the genus Bacillus, in particular of the non-pathogenic species Bacillus subtilis. By using the classical agar-well diffusion method, we investigated the influence of the culture conditions and the composition of the culture medium on the antimicrobial activity of Bacillus subtilis strain 46/H1 against the filamentous fungi Fusarium oxysporum and Aspergillus flavus. The fungal suspensions were preliminarily inoculated in the agar media, whereas the cell-free supernatant, the cell biomass and the culture liquid of B. subtilis 46/H1 were pipetted into the wells. The influence of the cultural conditions on the inhibitory activity of B. subtilis 46/H1 was determined by cultivation in agar media with pH ranging between 5.0 and 8.0, at temperature 25°c and 30°c. The influence of the composition of culture medium on the inhibitory activity of B. subtilis 46/H1 was determined by changing the carbon and nitrogen sources. After 72 hours of incubation, the antimicrobial effect was determined by measuring the diameter of the zones of inhibition around the wells. The antimicrobial activity of B. subtilis 46/H1 against both fungal species was higher at temperature of cultivation 30°c. The change of the carbon and nitrogen sources in the standard culture medium led to an increase in the inhibitory effect, which was stronger against the fungus Fusarium oxysporum and almost insignificant against the second test-microorganism - Aspergillus flavus. In addition, the antifugal activity against Fusarium oxysporum was higher after changing the nitrogen source than after the change of the carbon source. [ABSTRACT FROM AUTHOR]

The antimicrobial activity of Leuconostoc lactis BT17, isolated from a spontaneously fermented cereal beverage (boza) against some test microorganisms (Escherichia coli ATCC 25922, Salmonella sp. and Klebsiella pneumoniae) was determined by co-culturing of the strain Leuconostoc lactis BT17 with each of the test microorganisms under static conditions. It was found that the strain Leuconostoc lactis BT17 inhibited the growth of the test microorganisms and no viable cells of Escherichia coli, Salmonella sp. and Klebsiella pneumoniae were detected at the 48-th hour of the co-culturing. The reduction of the number of viable cells in the mixed populations was a result of the produced lactic acid by Leuconostoc lactis BT17 in the culture medium, which modify the conditions unlikely to growth of the test microorganisms. [ABSTRACT FROM AUTHOR]