Lactic Acid Bacteria Cultures Research Articles

Impact of buffering capacity on the acidification of wort by brewing-relevant lactic acid bacteria

Acidified wort produced biologically using lactic acid bacteria (LAB) has application during sour beer production and in breweries adhering to the German purity law (Reinheitsgebot). LAB cultures, however, suffer from end product inhibition and low pH, leading to inefficient lactic acid (LA) yields. Three brewing-relevant LAB (Pediococcus acidilactici AB39, Lactobacillus amylovorus FST2.11 and Lactobacillus plantarum FST1.7) were examined during batch fermentation of wort possessing increasing buffering capacities (BC). Bacterial growth was progressively impaired when exposed to higher LA concentrations, ceasing in the pH range of 2.9–3.4. The proteolytic rest (50°C) during mashing was found to be a major factor improving the BC of wort. Both a longer mashing profile and the addition of an external protease increased the BC (1.21 and 1.24, respectively) compared with a control wort (1.18), and a positive, linear correlation (R2 = 0.957) between free amino nitrogen and BC was established. Higher levels of BC led to significant greater LA concentration (up to +24%) after 48 h of fermentation, reaching a maximal value of 11.3 g/L. Even higher LA (maximum 12.8 g/L) could be obtained when external buffers were added to wort, while depletion of micronutrient(s) (monosaccharides, amino acids and/or other unidentified compounds) was suggested as the cause of LAB growth cessation. Overall, a significant improvement in LA production during batch fermentation of wort is possible when BC is improved through mashing and/or inclusion of additives (protease and/or external buffers), with further potential for optimization when strain-dependent nutritional requirements, e.g. sugar and amino acids, are considered. Copyright © 2017 The Institute of Brewing & Distilling

Ability of lactobacilli isolated from traditional cereal-based fermented food to produce folate in culture media under different growth conditions

Folates are essential vitamins (B9). Lactic acid bacteria (LAB) can be used to increase the folate levels in foods during fermentation. Here, 151 LAB strains isolated from fermented food were screened for folate production. Folates were extracted by heat treatment coupled with enzymatic extraction. Total, extra- and intracellular folate were quantified by microbiological assay. Most Lactobacillus plantarum and Lactobacillus fermentum strains synthesized folate, Pediococcus pentosaceus strains consumed folate, and Pediococcus acidilactici strains either consumed or produced. Seven strains were further examined for their ability to synthesize or consume folate during growth in rich folate medium (MRS) and folate-free medium (FACM). For most strains, the differences observed in MRS were attenuated in FACM. L. fermentum 8.2 and L. plantarum 6.2 produced the highest levels of folates in MRS (97 and 93 ng·mL−1) and FACM (29 and 44 ng·mL−1). In most cases, production reached a maximum from 9 or 11 h to 24 h. Incubations in FACM with mixed LAB cultures showed that folate production is not additive. We demonstrated how biosynthesis of folate by LAB depends on species, strains, and is highly influenced by time and medium composition. Characterized LAB strains can be further explored for novel folate bio-enriched functional food.

English

In this study, the potential use of sweet whey as a base medium for lactic acid bacteria culture and its effect on the technological characteristics of lactobacilli was evaluated. Bacteria were grown on raw or deproteinized whey supplemented with different amounts of yeast extract and/or tomato juice. Results obtained showed that biomass production on whey supplemented with yeast extract was higher than those observed with tomato juice. Whilst, supplementation by either whey, tomato juice or yeast extract increased significantly the growth of both lactic acid bacteria, the performance was in the same range as that on a modified MRS medium. Additionally, acidification and proteolytic activities resulting from control and modified MRS medium were of comparable values. The present investigation demonstrates that sweet whey can be used as an alternative substrate for lactic acid bacteria cultural purposes and provide opportunity to make a new growth medium with low cost.   Key words: Acidification, bacterial growth, Lactobacillus, proteolytic activity, sweet whey, tomato juice, yeast extract.

Dietary supplements based on selenium containing culture of lactic acid bacteria

The article describes the role of selenium in the humankind being. The analysis based on the published data shows that the biological synthesis is a perspective way to obtain an organic form of selenium, which can be used in dietary supplements. The ability of lactic acid bacteria (Lactobacillus acidophilus 412/307)to accumulate inorganic forms of selenium (selenites, selenates), turning them into organic forms, with purposeful trace element enrichment of culture medium is described in the article. The main organic forms of selenium, which are being used in the process of biotransformation from its inorganic forms by microorganisms, have been reorganized. The relationship between the increasing of concentrations of sodium selenite in the culture medium and the growth of biomass of lactic acid bacteria was established. It was found the depressing effect of increasing concentrations of sodium selenite on optical density rate. It was estabilished the optimal conditions for the maximum accumulation of selenium containing culture of lactic acid bacteria. The influence of selenium concentration on the lactic acid bacteria biomass accumulation was determined also by changing the values of optical density. Due to the obtained data, the selenium containing dietary supplement «Selenolakt» was created. The main microbiological indicators that characterize the quality of the obtained product are given. The content of organic form of selenium in products reaches –195 ± 1 mkg/g.

Spray-dried adjunct cultures of autochthonous non-starter lactic acid bacteria

Spray-drying of lactic cultures provides direct-to-vat starters, which facilitate their commercialization and use. However, this process may alter the metabolic activity and deteriorate technological features. In this work, we assessed the influence of spray-drying on the survival and aroma production of two strains of mesophilic lactobacilli: Lactobacillus paracasei 90 and Lactobacillus plantarum 91, which have already been characterized as good adjunct cultures. The spray-drying was carried out using a laboratory scale spray and the dried cultures were monitored during the storage for the survival rate. The dried cultures were applied to two cheese models: sterile cheese extract and miniature soft cheese. The influence on the carbohydrate metabolism and the production of organic acids and volatile compounds was determined. Both strains retained high levels of viable counts in the powder after drying and during the storage at 5°C for twelve months. In addition, they also remained at high level in both cheese models during incubation or ripening. Similar profiles of carbohydrate fermentation and bioformation of volatile compounds were observed in the cheese extracts for each of the strains when tested as both fresh and dried cultures. In addition, the ability of Lb. paracasei 90 to increase the production of acetoin and diacetyl remarkably in cheese models was also confirmed for the spray-dried culture.

Perubahan Komposisi Kimiawi Produk Yogurt dengan Penambahan Kalsium Karbonat pada Kultur Starter Campuran

Mixed lactic acid bacteria culture is commonly used in yogurt production. In the present study, two lactic acid bacteria (Lactobacillus bulgaricus and Streptococcus thermophillus) was used as starter culture. Calcium carbonate was added to the starter culture to increase the quality of mixed starter culture of L. bulgaricus and S. thermophillus with ratio of 4:1. The present study was directed to investigate the chemical composition of mixed starter culture with and without calcium carbonat addition. Furthermore, the effect of each starter culture on yogurt product chemical composition was also examined. The pH, lactose, soluble protein and acid content was determined as chemical composition parameters. For starter culture without calcium carbonate addition, the yogurt has pH, lactose, soluble protein and acid content of 4.18–4.39, 4.18–4.39% w/v, 2.88–4.36% w/v and 0.82–0.99% w/v, respectively. While for starter culture with calcium carbonate addition, the yogurt product has pH, lactose, soluble protein and acid content of 4.26–4.37, 1.47–1.75% b/v, 3.42–4.95% w/v and 0.86–1.11% w/v, respectively. Addition of 0.05% w/v calcium carbonate to mixed starter culture gave effect on lactose consumption, where it still can convert lactose to lactic acid up to 45 days of storage. Furthermore, the yogurt product made with starter culture with calcium carbonate addition has higher soluble protein content compared to yogurt made with starter culture without calcium carbonate addition

Effects of Lactobacillus plantarum Strain OLL2712 Culture Conditions on the Anti-inflammatory Activities for Murine Immune Cells and Obese and Type 2 Diabetic Mice.

Studies on the health-promoting effects of lactic acid bacteria (LAB) are numerous, but few provide examples of the relationship between LAB function and culture conditions. We verified the effect of differences in culture conditions on Lactobacillus plantarum OLL2712 functionality; this strain exhibits anti-inflammatory activity and preventive effects against metabolic disorders. We measured interleukin-10 (IL-10) and IL-12 production in murine immune cells treated with OLL2712 cells prepared under various culture conditions. The results showed that the IL-10-inducing activities of OLL2712 cells on murine immune cells differed dramatically between OLL2712 groups at different culture phases and using different culture medium components, temperatures, and neutralizing pHs. In particular, exponential-phase cells had much more IL-10-inducing activity than stationary-phase cells. We confirmed that the Toll-like receptor 2 (TLR2) stimulation activity of OLL2712 cells depended on culture conditions in conjunction with IL-10-inducing activity. We also demonstrated functional differences by culture phases in vivo; OLL2712 cells at exponential phase had more anti-inflammatory activity and anti-metabolic-disorder effects on obese and diabetic mice than those by their stationary-phase counterparts. These results suggest that culture conditions affect the functionality of anti-inflammatory LAB.IMPORTANCE While previous studies demonstrated that culture conditions affected the immunomodulatory properties of lactic acid bacteria (LAB), few have comprehensively investigated the relationship between culture conditions and LAB functionality. In this study, we demonstrated several culture conditions of Lactobacillus plantarum OLL2712 for higher anti-inflammatory activity. We also showed that culture conditions concretely influenced the health-promoting functions of OLL2712 in vivo, particularly against metabolic disorders. Further, we characterized a novel mechanism by which changing LAB culture conditions affected immunomodulatory properties. Our results suggest that culture condition optimization is important for the production of LAB with anti-inflammatory activity.

Use of Psychrotolerant Lactic Acid Bacteria (Lactobacillus spp. and Leuconostoc spp.) Isolated from Chinese Traditional Paocai for the Quality Improvement of Paocai Products.

To improve the quality of Chinese traditional Paocai, two psychrotolerant lactic acid bacteria (LAB) strains were isolated from Paocai, and the quality of Chinese Paocai product using these two strains as starter cultures was compared to a control sample fermented with aged brine at 10 °C. The results suggested that the physicochemical and sensory features of Paocai fermented with psychrotolerant LAB were more suitable for industrial applications. The nitrite content of Paocai fermented with psychrotolerant LAB was 1 mg/kg, which was significantly lower than that of the control Paocai (P < 0.05). Low-temperature fermentation with the starter cultures of psychrotolerant LAB could effectively prevent overacidity and over-ripening of the Paocai products. Additionally, Paocai fermented with psychrotolerant LAB harbored relatively simple microbial flora as revealed by polymerase chain reaction-denaturing gradient gel electrophoresis. This study provides a basis for improving the quality of Chinese traditional Paocai and the large-scale production of low-temperature Chinese traditional Paocai products.

Дослідження впливу складу захисного середовища на збереження життєздатності ліофілізованих бактерій L. lactis та L. plantarum, виділених із традиційної карпатської бринзи

Вивчено вплив складу захисних середовищ на збереження життєздатності та технологічні властивості ліофілізованих бактерій штамів L. lactis та L. plantarum. Для досліджень обрано білково-вуглеводне та сахарозо-желатозне середовища. Об’єктами досліджень були чисті культури молочнокислих бактерій (МКБ): L. lactis SB 16, L. lactis SB 44, L. plantarum SB 5, L. plantarum SB 7, L. plantarum SB 17, виділені на попередніх етапах роботи із традиційної бринзи, виготовленої у непромислових умовах Карпатського регіону України. Культури бактерій ідентифіковано із використанням класичних мікробіологічних і сучасних молекулярно-генетичних методів (RAPD-PCR, RFLP-PCR, секвенування гену 16S рРНК). Чисельність мезо- і термофільних лактобактерій визначали шляхом посіву на середовище MRS. Молокозсідальну активність монокультур визначали за зміною кислотності молока. Процес сублімаційного сушіння біомаси, змішаної із відповідною кількістю захисного середовища, здійснювали із використанням сублімаційної сушарки «Alpha 1,2 LD Plus». За визначеною експериментальним шляхом кількістю загиблих під час сушіння клітин встановлювали Рівень Збереження Життєздатності (РЗЖ) різних видів і штамів. Встановлено, що за своїми кріопротекторними властивостями кращим для сушіння клітин досліджених монокультур є сахарозо-желатозне середовище, яке забезпечує високий РЗЖ, особливо для L. lactis SB 16 (кількість загиблих під час сушіння клітин становила 9,2%) та L. plantarum SB 17 (кількість загиблих під час сушіння клітин становила 9,9%). Проведено порівняльне дослідження РЗЖ різних видів МКБ за різних умов зберігання. Встановлено, що усі штами молочнокислих бактерій, за винятком штаму L. lactis SB 16, протягом зберігання у знежиреному молоці за температури (+6) °С через місяць втрачають від 4 до 15% життєздатних клітин. Термін зберігання штамів L. lactis та L. plantarum у сухій культурі становить 6 міс.

Antagonistic effects of three lactic acid bacterial strains isolated from Nigerian indigenous fermented Ogi on E. coli EKT004 in co-culture

E. coli is one of the major pathogenic bacteria that cause diarrhoea in human. Traditional fermented foods, e.g. Ogi, has been used indigenously to treat diarrhoea. This study was aimed at investigating the antagonistic activity of selected lactic acid bacteria (LAB) isolated from three varieties of ogi against multidrug resistant E. coli EKT004. Antibiotic susceptibility of the tested E. coli EKT004 strain to ofloxacin, gentamycin, cefuroxime, ceftazidine, lincomycin, oxacillin, cloxacillin, cefotaxime, ciprofloxacin, and nitrofurantoin was tested by disc diffusion method. E. coli EKT004 was co-incubated in two different experiments with Weissella paramesenteroides, Lactobacillus plantarum, and L. fermentum that have been previously isolated from Ogi. An 8 h old E. coli was introduced into an overnight culture of LAB and a fresh E. coli was inoculated into overnight culture of LAB. Viable count of pathogen at 0 h and after 24 h co-incubation at 37 °C was observed. The tested E. coli EKT004 was resistant to cefuroxime, ceftazidime, lincomycin, oxacillin, cloxacillin, and cefotaxime. The tested LAB isolates have a broad spectrum of activity against E. coli EKT004 used for the study with a decrease of 6–8 log of E. coli as compared with the control. These results indicate a direct effect of lactic acid bacterial strains on multidrug resistant E. coli strain.

Nondairy beverage produced by controlled fermentation with potential probiotic starter cultures of lactic acid bacteria and yeast

This work aimed to develop a nondairy fermented beverage from a blend of cassava and rice based on Brazilian indigenous beverage cauim using probiotic lactic acid bacteria (LAB) and yeast. The indigenous strains Lactobacillus plantarum CCMA 0743 (from cauim) and Torulaspora delbrueckii CCMA 0235 (from tarubá), and the commercial probiotic, L. acidophilus LAC-04, were used as starter cultures in single and co-cultivations. The bacteria populations were around 8.0 log (CFU/mL) at the end of all fermentations as recommended for probiotic products. Higher residual starch contents were noted in the single LAB cultures (10.6% [w/w]) than in co-cultures (<6% [w/w]), showing that co-culture may help the digestibility. For all different assays (single and co-culture), lactic acid was the main organic acid detected (>1.6g/L) and ethanol was lower than 0.5% (w/v) consisting in a non-alcoholic beverage. The assays containing yeast showed the highest antioxidant activity (around 10% by DPPH and ABTS methods). Therefore, a nondairy fermented beverage was successfully obtained, and the co-culture of LAB and T. delbrueckii could increase the product's functional properties.

Diffusible substances from lactic acid bacterial cultures exert strong inhibitory effects on Listeria monocytogenes and Salmonella enterica serovar enteritidis in a co-culture model

BackgroundFood-borne infections cause huge economic and human life losses. Listeria monocytogenes and Salmonella enterica serovar Enteritidis are among the top ranking pathogens causing such losses. Control of such infections is hampered by persistent contamination of foods and food-processing environments, resistance of pathogens to sanitizing agents, existence of heterogeneous populations of pathogens (including culturable and viable but non-culturable cells) within the same food items, and inability to detect all such pathogens by culture-based methods. Modern methods such as flow cytometry allow analyses of cells at the single cell level within a short time and enable better and faster detection of such pathogens and distinctions between live and dead cells. Such methods should be complemented by control strategies including the use of beneficial bacteria that produce metabolites capable of inhibiting food-borne pathogens. In this study, broth cultures of lactic acid bacteria (LAB) isolated from fermented milk were tested for production of substances capable of inhibiting L. monocytogenes and S. Enteritidis in co-culture with LAB by assessment of colony-forming units (CFU) and live:dead cell populations by flow cytometry.ResultsThe LAB isolates belonged to the species Lactococcus lactis, Enterococcus faecalis and Enterococcus faecium. Some LAB were effective in inhibition. Plating indicated up to 99% reduction in CFU from co-cultures compared to control cultures. Most of the bacteria in both cultures were in the viable but non-culturable state. The flow data showed that there were significantly higher dead cell numbers in co-cultures than in control cultures, indicating that such killing was caused by diffusible substances produced by the LAB cultures.ConclusionThis study showed that metabolites from selected local LAB species can be used to significantly reduce pathogen load. However, conditions of use and application need to be further investigated and optimized for large-scale utilization.

LACTIC ACID BACTERIA AND YEAST DIVERSITIES IN SPONTANEOUSLY FERMENTED MILLET SOURDOUGHS

The lactic acid bacteria (LAB) and yeast diversities in spontaneously fermented pearl millet (Pennisetum glaucum) and finger millet (Eleusine coracona) sourdoughs were investigated. Pearl and finger millet grains were processed into flour and used in spontaneous sourdough fermentation. LAB and yeast cultures were isolated, screened and identified based on morphological, biochemical and sugar utilisation pattern using API 50CHL and API 20 AUX kits. Titratable acidity, pH and Temperatures of sourdoughs developed were also monitored. Titratable acidity and Temperature increased with increasing days of fermentation and conversely the pH. and mesophilic bacterial count followed that of a normal bacterial growth curve. Dominant LAB and yeasts in pearl and finger millet spontaneously developed sourdoughs were Lb. plantarum, Lb. plantarum 1, Pediococcus pentosaseus, Lb. pentosus, and Saccharomyces cereviasiae. However, Candida milleri was found in pearl millet sourdoughs. The dominant cultures in millet sourdoughs could find applications as starter cultures if improved sourdough quality is desired.

Starter cultures of lactic acid bacteria for special diet products

Abstract From fresh and fermented vegetables (cucumber, sauercraut, eggplant), cereals (wheat, rice), legumes (soy) 37 cultures of lactic acid bacteria were isolated. Based on biochemical characteristics, MALDI-TOF MS protein profiling and 16S rRNA gene sequencing they were identified as representatives of Lactobacillus, Lactococcus, Leuconostoc, Pediococcus and Enterococcus genera. Six members of Lactobacillus genera and two members of Leuconostoc genera actively producing EPS were selected for further investigation as components of starters for production of special dietetic foodstuffs.

Analyses of Dynamics in Dairy Products and Identification of Lactic Acid Bacteria Population by Molecular Methods

Lactic acid bacteria (LAB) with different ecological niches are widely seen in fermented meat, vegetables, dairy products and cereals as well as in fermented beverages. Lactic acid bacteria are the most important group of bacteria in dairy industry due to their probiotic characteristics and fermentation agents as starter culture. In the taxonomy of the lactic acid bacteria; by means of rep-PCR, which is the analysis of repetitive sequences that are based on 16S ribosomal RNA (rRNA) gene sequence, it is possible to conduct structural microbial community analyses such as Restriction Fragment Length Polymorphism (RFLP) analysis of DNA fragments of different sizes cut with enzymes, Random Amplified Polymorphic DNA (RAPD) polymorphic DNA amplified randomly at low temperatures and Amplified Fragment-Length Polymorphism (AFLP)-PCR of cut genomic DNA. Besides, in the recent years, non-culture-based molecular methods such as Pulse Field Gel Electrophoresis (PFGE), Denaturing Gradient Gel Electrophoresis (DGGE), Thermal Gradient Gel Electrophoresis (TGGE), and Fluorescence In-situ Hybridization (FISH) have replaced classical methods once used for the identification of LAB. Identification of lactic acid bacteria culture independent regardless of the method will be one of the most important methods used in the future pyrosequencing as a Next Generation Sequencing (NGS) techniques. This paper reviews molecular-method based studies conducted on the identification of LAB species in dairy products.

Development of technology of sour cream product with increased shelf life

A characteristic feature of sour cream products is the production of recombined cream, obtained from natural cow milk raw materials, dry skimmed milk and / or substitutes, dry cream and / or substitutes, vegetable protein and milk fat substitute, with the addition or Without the addition of milk processing products by ripening with pure cultures of lactic acid bacteria with or without the addition of stabilizers, flavorings, preservatives and for direct use as food. The use of dairy fat substitutes in dairy products has long been practiced by manufacturers. Advantages of a substitute for milk fat in front of milk fat are obvious: the composition does not include cholesterol, which does not increase the risk of heart disease; Contains unsaturated fatty acids, which are useful for the body and are quickly absorbed; adding a substitute for improved product consistency; A substitute is cheaper than natural milk fat, as a result of which the final product is more affordable. Products based on a substitute for milk fat are shown to people suffering from diabetes, hypertension or lactose intolerance. The production of the sour cream product was carried out according to the standard technological scheme with addition of the operation of introducing the chitosan solution before the fermentation stage. Grounded structure and rational ratio to the chitosan solution formulation sour cream product. It is proved that the introduction of a solution of chitosan into the composition of the sour cream product leads to a more stable and long-lasting preservation of the quality and safety indicators of products and an increase in their shelf life. It is possible to implement the results obtained in industrial conditions.

Brewery Wastes Reuse for Protease Production by Lactic Acid Bacteria Fermentation

This study evaluated the use of three solid brewery wastes: brewer's spent grain, hot trub and residual brewer's yeast, as alternative media for the cultivation of lactic acid bacteria to evaluate their potential for proteolytic enzyme production. Initially, a mixture experimental design was used to evaluate the effect of each residue, as well as different mixtures (with the protein content set at 4%) in the enzyme production. At predetermined intervals, the solid and liquid fractions were separated and the extracellular proteolytic activity was determined. After selecting the best experimental conditions, a second experiment, factorial experimental design, was developed in order to evaluate the protein content in the media (1 to 7%) and the addition of fermentable sugar (glucose, 1 to 7%). Among the wastes, residual yeast showed the highest potential for the production of extracellular enzymes, generating a proteolytic extract with 2.6 U/mL in 3 h. However, due to the low content of the fermentable sugars in the medium, the addition of glucose also had a positive effect, increasing the proteolytic activity to 4.9 U/mL. The best experimental conditions of each experimental design were reproduced for comparison, and the enzyme content was separated by ethanol precipitation. The best medium produced a precipitated protein with proteolytic activity of 145.5 U/g.

Effect of Magnesium Acetate on the Antimold Activity of Lactobacillus

The antimold activity of lactic acid bacteria (LAB) is used in food biopreservation. The aim of this study was to evaluate the effect of magnesium acetate added to de Man Rogosa Sharpe (MRS) medium on the antimold activity of three LAB strains ( Lactobacillus plantarum , Lactobacillus brevis , and Lactobacillus fermentum ) against molds contaminating food ( Aspergillus oryzae , Aspergillus niger , Penicillium chrysogenum , Fusarium avenaceum , and Rhizopus arrhizus ) and their ability to produce organic acids (acetic acid, lactic acid, and phenyllactic acid). The antimold activity of LAB strains was evaluated using the overlay method, and the concentration of the organic acids was determined with the gas chromatography technique. Changes in viable cell counts and the pH of LAB culture also were monitored over a 48-h period. The results show that the growth inhibition of all the molds (except R. arrhizus ) was higher in LAB strain cultures on MRS with magnesium acetate agar than on MRS agar, and inhibition increased over the 48 h. Magnesium acetate added to MRS broth stimulated the production of acetic acid by all LAB strains in the first 8 h and slightly stimulated the production of lactic acid by L. plantarum during the first 24 h. No adverse effect of magnesium acetate on growth of LAB strains was noted. The results confirm that magnesium acetate enhances the antimold activity of LAB strains.

Evaluation of the potential use of probiotic strain Lactobacillus plantarum 299v in lactic fermentation of button mushroom fruiting bodies.

The available literature does not provide data on the application of probiotic strains in mushroom processing. The aim of the study was to evaluate the potential to use the L. plantarum 299v strain with documented probiotic properties in the process of lactic fermentation of button mushroom fruiting bodies (Agaricus bisporus). Fresh button mushroom fruiting bodies and cultures of lactic acid bacteria L. plantarum Ib and a probiotic strain L. plantarum 299v were the material analysed. Sensory evaluation was performed with a 5-point scale, an instrumental method of colour measurement based on the CIA L*a*b* scale, total phenolic compounds were determined with the Folin method, antioxidant properties were assayed with the DPPH radical test, and reducing power was determined using the FRAP method. After a week-long lactic fermentation, the pH value in the samples declined to a level of 3.6 (L. plantarum Ib) and 3.75 (L. plantarum 299v); these values persisted or decreased slightly during the period of maturation of the fermented samples under refrigeration. Fermented mushrooms were assigned high grades in the organoleptic evaluation. The colour analysis revealed significant changes in the values of the L*a*b* parameters in the fermented product, in comparison with fresh mushrooms. Blanching contributed to a significant decrease in the content of total phenolic compounds in the mushroom fruiting bodies and to a decline in antioxidant activity. Mushrooms fermented with the probiotic strain were characterised by higher phenolic compound content and higher antioxidant activity. L. plantarum 299v strain with documented probiotic properties can be applied in fermentation of button mushroom fruiting bodies. Products obtained with the use of both strains were characterised by good sensory properties. The type of strain used in the lactic fermentation of mushroom fruiting bodies had an effect on the phenolic compound content and antioxidant properties of the final product.

Composition, proteolysis, and volatile profile of Strachitunt cheese

Strachitunt, a blue-veined Italian cheese, received the Protected Designation of Origin (PDO) label in 2014. Its unique technological feature is represented by the dual-curd method of production. Strachitunt is produced from raw bovine milk with or without the inoculation of natural starter cultures of lactic acid bacteria, and the addition of secondary cultures of mold spores is not permitted by the product specification. Physico-chemical properties, proteolysis, and volatile profile of Strachitunt were investigated in 10 cheese samples (ripened for 75 d) made throughout spring 2015 and provided by the main cheese maker. Overall, composition parameters showed a large variability among samples. Cheese was characterized by an acid paste (pH 5.46) and a lower extent of proteolysis compared with other blue-veined varieties. The main chemical groups of volatile organic compounds were alcohols and esters, whereas ketones represented only a minor component. The erratic adventitious contamination by mold spores of the cheese milk, the unique dual-curd method of cheese-making, and the large time variability between the piercing time and the end of ripening could be highlighted as the main causes of both the distinctive analytical fingerprint and the scarce standardization of this blue-veined cheese.