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In today’s dynamic development of food technologies it becomes necessary to study alternative sources of starch to replace the traditionally used ones. Characteristics such as granule size, gelling properties, retrogradation and rheology are fundamental for the selection of starch in the food industry. The aim of the present study is to investigate the possibilities for application of an emmer starch in food industry by comparing its main properties with two other cereal starches, isolated from rice and wheat. The results showed that the emmer starch had a similar granule size and structure, with increased amylose content as the wheat starch. This was also the reason for the similar gelling and retrograde properties as wheat starch. In terms of retrogradation, the highest results showed emmer starch and the lowest - rice starch. Emmer starch had the lowest onset temperature of gelatinization, and the peak temperature of gelatinization was 76.3°C. The starch gel obtained with emmer starch has the lowest viscosity but the most shear resistance compared to that with wheat and rice starch.

Wort-based beverages produced by lactic acid fermentation showed high nutritional value and functional properties but their flavor was not well accepted by consumers. Therefore, raspberry (Rubus idaeus L) seed oil in concentration of 0.0375% (v/v) was used in order to improve beverage flavor and to increase its biological value. Fermentation was carried out in bottles (static conditions) and in a stirred tank bioreactor (dynamic conditions) at 25°C. The effect of raspberry seed oil addition was investigated by measuring the content of lactic acid bacteria cells, the pH, the phenolic compounds and the antioxidant activity of the beverages with raspberry seed oil addition and the control sample without oil addition. Results showed that stirring increased fermentation rate but led to a decrease in the phenolic compounds content and the antioxidant activity of the beverages produced. Nevertheless, all beverages can be classified as functional because the concentration of lactic acid bacteria was over 107 cells/mL. Our results indicated that functional lactic acid wort-based beverage with improved biological value and flavour can be produced in static fermentation by adding 0.0375% raspberry seed oil.

Sourdough starter development includes examination of potential strains of lactic acid bacteria (LAB), propionic acid bacteria and yeasts, selection of suitable strains, development of combinations and examination of the relationships between the strains in each combination, selection of symbiotic combinations and their industrial probation to determine their qualities. Three sourdough starter combinations from selected lactobacilli (homo- and heterofermentative species) or selected lactobacilli and propionic acid bacteria were developed. The dynamics of the concentration of viable cells of the strains and the sourdough acidity in the back-slopping process up to the 96th hour were monitored. The rheological properties of the starter sourdoughs were characterized. The main dough obtained with sourdough was stronger, more elastic, the pieces of bread were taller. The developed sourdough starters were tested in the production of wheat, wheat-rye, spelt and spelled bread. The finished bread loaves had softer and lighter crumb, and pleasant and characteristic lactic acid aroma. It has been shown that the different bread types obtained with symbiotic starter sourdoughs had longer shelf life and increased microbiological safety. The best starter combination as well as the optimum concentration of starter sourdough for prevention of bacterial and fungal spoilage for each bread type has been determined.

Bacillus amyloliquefaciens M is a non-pathogenic microorganism with probiotic properties isolated from mineral waters in the village of Yabаlkovo, Haskovo region, for inclusion in the composition of probiotics and probiotic foods. It has high antimicrobial activity against pathogenic bacteria, causing food toxic infections and intoxications, as well as against saprophytic microorganisms - bacteria and fungi, which makes it suitable as a biological preparation for plant protection. In order to perform these functions, it is necessary to obtain a spore concentrate. The composition of the nutrient medium for the cultivation and sporulation of the strain has been determined: MP nutrient broth with the addition of salts, in which the strain grew well and a high sporulation rate of 99% was achieved. Cultivation in a bioreactor has been carried out and the time to achieve a high degree of sporulation has been determined. The kinetic parameters of growth and sporulation of Bacillus amyloliquefaciens M in aerobic batch cultivation with a high concentration of spore forms have also been determined. It has been shown that the sporulation process in this strain starts after 12 h from the cultivation start.

A Lactobacillus strain was isolated from rose blossom of Rosa damascena Mill. and it was identified as belonging to the species Lactobacillus helveticus by the application of physiological-biochemical (API 50 CHL) and molecular-genetic methods (sequencing of the 16S rRNA gene). The presence of a number of probiotic properties of L. helveticus 2/20 was investigated. The strain exhibited high antimicrobial activity against pathogenic microorganisms that cause food toxicoinfections and intoxications. L. helveticus 2/20 survived in the simulated conditions of the gastrointestinal tract – pH = 2 and pepsin, pH = 4.5 and pancreatin and pH = 8 and pancreatin, as well as in the presence of up to 0.3% bile salts, retaining a significant concentration of viable cells. It has been shown that L. helveticus 2/20 cells begin multiplying after removing the extreme conditions. The strain allowed bioreactor cultivation and freeze-drying of the obtained concentrates, with the concentration of active cells in the lyophilic preparations exceeding 1012 cfu/g. The kinetic parameters of the batch cultivation process in a bioreactor with stirring and the maximum growth rate were determined, revealing the possibilities for scaling up of the fermentation process from laboratory to industrial conditions, as well as its management. After further research on the probiotic properties of L. helveticus 2/20, it can be included in the composition of probiotics and functional foods.

Batch cultivation in a laboratory bioreactor with stirring of the lactobacilli strains with probiotic properties Lacticaseibacillus casei ssp. casei G17 and Lacticaseibacillus casei ssp. rhamnosus G16 isolated from pink blossom of Rosa damascena Mill was conducted. The changes in the concentration of viable cells were monitored. The growth kinetics was modeled applying the classic and modified logistic curve model and the maximum specific growth rate (μm) of the studied strains was determined. The classical model of the logistic curve showed higher μm for Lacticaseibacillus casei ssp. casei G17 - 0.133 h-1, compared to Lacticaseibacillus casei ssp. rhamnosus G16 - 0.120 h-1, while the modified logistic curve model predicted comparable maximum growth rates of 0.105 h-1 and 0.101 h-1 for Lacticaseibacillus casei ssp. casei G17 and Lacticaseibacillus casei ssp. rhamnosus G16, respectively. Lacticaseibacillus casei ssp. casei G17 was characterized by a shorter induction period (τa = 0.72 h) and a higher adaptation rate constant (k0 – 0.390 h-1) compared to Lacticaseibacillus casei ssp. rhamnosus G16 (τa=1.66 h; k0=0.110 h-1). The established kinetic parameters show that Lacticaseibacillus casei ssp. rhamnosus G16 needs the addition of growth factors in the fermentation medium that will help to optimize its composition for scaling up the fermentation process.

An interesting property for many probiotic strains is to exhibit antimicrobial activity against pathogenic microorganisms. Therefore, the antimicrobial activity of the potentially probiotic strain Lactobacillus acidophilus L12 against Escherichia coli, Staphylococcus aureus and Salmonella sp. was examined in vitro through co-culturing of Lactobacillus acidophilus L12 with each of the pathogenic strains for 72 h. When cultured individually, all strains reached a final population always exceeding 1012 cfu/mL. When co-cultured with each of the pathogenic strains Lactobacillus acidophilus L12 population always exceeded 1012 cfu/mL, while the bacterial population of the pathogenic strains was reduced in a strain-specific manner. Lactobacillus acidophilus L12 demonstrated the highest inhibitory activity against the two Staphylococcus aureus strains, followed by the two E. coli strains, and the two Salmonella sp. strains tested. The kinetics of the co-culturing process of Lactobacillus acidophilus L12 with each of the test pathogenic strains was modelled using the logistic curve model. The obtained results show the strong antagonistic activity of the potentially probiotic strain Lactobacillus acidophilus L12, thus making it a promising candidate for inclusion in the composition of probiotic preparations and functional probiotic foods.

The antimicrobial activity of potentially probiotic strains is important for their possible application in the development of successful strategies for bio-preservation of different foods. The antimicrobial activity of the potentially probiotic strain Lactobacillus plantarum L4 against the pathogenic bacteria Salmonella abony; Staphylococcus aureus; Escherichia coli and the phytopathogenic fungi Aspergillus niger and Aspergillus flavus was determined using agar-diffusion assay with wells. Lb. plantarum L4 exhibited high antagonistic activity against all test microorganisms included in the study, which was due not only to the production and accumulation of lactic acid and other organic acids, but also to the production of other bioactive substances. The bioactive substances were then submitted to the action of different enzymes. This allowed to observe that they have protein nature, suggesting that they are likely bacteriocins or bacteriocin-like substances. The substances produced by Lb. plantarum L4 did not lose their antimicrobial activity during heat treatment at temperatures above 100 °С for 15 min and they exhibited high inhibitory activity against the test-microorganisms when pH ranged between 4 and 7. After further examination of the properties of the produced antimicrobial compounds, Lb. plantarum L4 can be used in the development of strategies for bio-preservation of different food products.

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]

Background. The bio-preservation of food products using various natural ingredients and metabolites from various types of beneficial microorganisms released during targeted fermentation is a method that simultaneously has a preservative effect on the food product and provides a model of its composition in order to ensure its functional and health properties. This double effect can be achieved by incorporating ingredients with proven preservative and functional effects into the food product, such as essential oils from various plant species and probiotic bacteria. The aim of the present research was to study the synergistic effect of selected probiotic lactic acid bacteria (LAB) and essential oils with high antimicrobial activity against pathogenic and spoilage microorganisms for the bio-preservation of chocolate mousse food emulsion. Materials and methods. The susceptibility of the selected probiotic strain Lactobacillus plantarum D2 to different concentrations of the selected lemon or grapefruit essential oil was examined using the disc-diffusion method. Nine chocolate mousse variants were prepared with the inclusion of free or immobilized cells of the probiotic strain L. plantarum D2 and/or lemon or grapefruit zest essential oils. The chocolate mousse variants were stored for 20 days in refrigerated conditions, and changes in the concentration of viable lactobacilli cells, the pH and the microbiological purity were monitored in accordance with standard requirements by taking samples on the 0th, 5th, 10th, 15th, and 20th days of storage. An organoleptic evaluation of the chocolate variants was performed on the 0th day. Results. Concentrations of up to 1% lemon or grapefruit essential oil did not affect the growth of the probiotic strain L. plantarum D2, which revealed opportunities for their joint application for the bio-preservation of food emulsions. The obtained chocolate mousse variants were characterized by preserved organoleptic characteristics and microbiological safety. Free or immobilized probiotic L. plantarum D2 cells applied alone or in combination with lemon or grapefruit essential oils provided bio-preservation of the food emulsions, maintaining a high concentration of viable cells (106-107 cfu/g) during storage under refrigerated conditions for 20 days. Conclusion. The combined application of free or immobilized probiotic LAB and lemon or grapefruit essential oils resulted in better bio-preservation results than in the use of probiotic LAB or essential oils alone, thus suggesting a synergistic effect between the two bio-preservative agents. Moreover, the obtained chocolate mousse emulsions can be classified as functional foods and the chocolate mousse food matrix can successfully be used as a vehicle for delivery of probiotic LAB to a wide range of food consumers. The obtained results and the developed successful bio-preservation strategy for the production of chocolate mousse food emulsions would provide grounds for the future selection of other probiotic lactobacilli strains, essential oils and synergistic combinations of them for the development of successful bio-preservation strategies for other types of food and beverage products. [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]

Introduction. The aim of the present work was to substantiate for production of low and non-alcoholic beer by changing the wort composition by replacing part of the malt with unmalted barley. Materials and methods. Industrial malt and non-malted barley were used. The alcohol fermentation was carried out using free and alginatechitosan encapsulated top-fermenting yeast strain Saccharomyces cerevisiae S-33. The mashing regime included two pauses - 30 min at 50 °C and 60 min at 77 °C. The aldehydes were determined according to the bisulfite method, the ester concentration was determined by ester saponification with NaOH. Metabolites were determined after simple sample distillation of the beer. Results and discussion. The wort extract decreased with the increase in the quantity of non-malted barley. In the selected mashing process, the fermentable sugars varied from 3.4 to 4.17% and accounted for about 50% of the laboratory wort extract. Use of 20% barley as adjunct led to a decrease in wort extract by 10% but it did not significantly affect viscosity. A major drawback of the use of non-malted barley is the increase in the laboratory wort filtration time. Filtration time was within 60-75 minutes when the adjunct was up to 20%. It was selected to replace 20% of the malt with unmalted barley. Wort in semi-industrial conditions with the thus selected quantitative malt/barley ratio was produced (8.03% (w/w) extract and fermentable sugar content of 3.7%.). The resulting wort was subjected to alcoholic fermentation at 10 °C for 7 days with free and immobilized cells, and for each variant the fermentation kinetics were determined. The process with free cells was relatively slow and in the first 2-3 days up to 0.4% of alcohol was accumulated, which corresponds to a fermentation rate of 11%. Changes occurred in secondary metabolism - increased ester production, normal higher alcohol formation and weak carbonyl compounds synthesis. In the immobilized cells, the fermentation start was also delayed. The actual process started after the 4th day, the fermentation quickly caught up with the free cell fermentation. As a result, more alcohol (about 0.7% w/w) was accumulated in the laboratory beer, thus enabling its classification as low-alcohol beer, and, fewer metabolites accumulated in the beer, which, in combination with the low fermentation temperature, had a negative effect on the taste profile. Conclusions. Technological regimes for production of low alcohol and non-alcoholic beer have been selected on the basis of analysis of wort sugars, as well as on a study of fermentation kinetics at low temperatures with free and immobilized yeast cells. [ABSTRACT FROM AUTHOR]

Three different kinetic models - Monod's model, Monod's model with substrate inhibition, and Monod's model with substrate and product inhibition were developed for studying of beer fermentation with free and immobilized cells at different main fermentation and maturation temperatures. The most accurate model was Monod's model with substrate and product inhibition. It showed that maturation temperature had no effect on primary metabolism but it affected significantly the secondary metabolites production. In regard to carbonyl compounds and esters, the increase in maturation temperature led to different trends for free and immobilized cells. Regarding the higher alcohols, the increase in maturation temperature resulted in increase in their yield coefficients for both immobilized and free cells. A sensory evaluation of beers produced with free and immobilized cells were also carried out and the results showed similar results for two beer types. [ABSTRACT FROM AUTHOR]

This study aims to investigate the chemical composition, antioxidant, and antimicrobial activity of Citrus aurantium L zest essential oil. The identification of the chemical compounds was done using chromatography analysis. The antioxidant activity was studied by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. Results showed that the main components of the essential oil were limonene (85.22%), β-myrcene (4.3%), and α-pinene (1.29%). Regarding the DPPH radical scavenging ability, the zest essential oil showed higher activity than limonene. The antimicrobial activity of the essential oil against pathogenic [Staphylococcus aureus NBIMCC 3703, Salmonella sp. (clinical isolate), Pseudomonas aeruginosa NBIMCC 1390, Bacillus subtilis NBIMCC 1208, Escherichia coli NBIMCC 3702] microorganisms by disc-diffusion method was examined. Gram-positive bacteria were more sensitive to the oil (inhibition zones being between 9 and 12.5 mm) and the minimum inhibitory concentration was more than 600 ppm; Gram-negative bacteria were less sensitive. The obtained essential oil displayed promising results for its application as a biopreservative agent. [ABSTRACT FROM AUTHOR]

Background. In recent years, increasing health awareness in consumers has motivated breweries to expand their beverage ranges with products with increased biological value. The aim of the present research was to develop probiotic wort-based beverages with grapefruit or tangerine zest essential oil addition. Materials and methods. Wort was produced with 60% Pilsen malt, 20% Vienna malt and 20% Caramel Munich II malt with and without the addition of 0.05% (v/v) grapefruit or tangerine essential oils. It was inoculated with the probiotic yeast strain Saccharomyces cerevisiae var. boulardii Y1. Fermentations were carried out at a constant temperature of 10°C for 5 days. The dynamics of the extract, the alcohol content and the concentration of viable cells were monitored daily. The total phenolic content, phenolic acid and flavonoid phenolic compounds were determined because of their antioxidant activity. The antioxidant activity was determined by radical scavenging assay (DPPH) and ferric reducing antioxidant power (FRAP). A descriptive organoleptic evaluation of the final beverages was performed. Results. The essential oils inhibited yeast growth to some extent at the beginning of the fermentation, even at a concentration of 0.05% (v/v), which resulted in lower alcohol content in the beverages with essential oil addition. Nevertheless, at the end of fermentation the concentration of viable cells was almost equal in all the beverages. Tangerine essential oil addition led to the highest content of phenolics, of which phenolic acids predominated. Therefore, the highest antioxidant activity of the beverage with tangerine essential oil can be ascribed to phenolic acids. The results of the sensorial evaluation also showed that the panel had preference towards the beverage with tangerine essential oil. Conclusion. The combination of essential oil and the probiotic yeast strain resulted in beverages with higher biological value than the beverages produced with the probiotic strain alone. The results obtained will be used for optimisation of process variables in the production of pilot-scale wort-based probiotic beverages with essential oil addition. [ABSTRACT FROM AUTHOR]