Evolution of fermenting microbiota in tarhana produced under controlled technological conditions

Fermented cereal soup with artichoke (Cynara scolymus L.) bracts: volatile profile, functional, powder and sensory properties

BACKGROUND

Artichoke (Cynara scolymus L.) bracts are agricultural wastes formed during artichoke processing. Artichoke bracts are used in fermented cereal soup tarhana to replace 10%, 20%, and 30% of wheat flour and functional, powder, sensory properties and volatile compounds of tarhana samples were investigated.

RESULTS

The use of artichoke bracts in tarhana increased total (8.37-17.17 g/100 g) and insoluble dietary fiber (5.84-14.09 g/100 g), total phenolic content (2.88-3.62 mg GAE/g), and antioxidant activity (3.07-3.86 μmol TE/g) values. Replacement of wheat flour by artichoke bracts resulted in lower L*, a*, and b* values. While water absorption capacity increased, oil absorption capacity and emulsifying activity were not affected by artichoke bracts replacement. Artichoke bracts replacement in tarhana influenced powder characteristics as, decrease in bulk density, increase in Carr index, wettability, and dispersibility values. Volatiles from terpene are most abundant (64.47-27.17 mg/kg) in tarhana containing artichoke bracts, followed by volatiles from ester (42.91-25.85 mg/kg). Limonene was the main volatile compound of tarhana samples.

CONCLUSION

Sensory acceptable tarhana was obtained when up to 30% artichoke bracts were used as wheat flour replacer in tarhana. The contribution to sustainability was achieved, and a healthier tarhana rich in dietary fiber was obtained by using artichoke bracts in tarhana. © 2023 Society of Chemical Industry.

Evaluation of the variations in chemical and microbiological properties of the sourdoughs produced with selected lactic acid bacteria strains during fermentation

•

Chemical, microbiological and VOCs profile showed the relevance of starter addition.

•

MiSeq Illumina confirmed that Lactobacillus spp. constituted the major LAB group.

•

Fructilactobacillus sanfranciscensis was the most isolated LAB species.

•

Rapid acidifying LAB strains should be preferred for sourdough production.

•

Number of VOCs increased in sourdoughs produced with starter culture.

This research aimed to analyze variations in chemical properties, microbiological characteristics and generated volatile organic compounds (VOCs) profile during sourdough fermentation. Sourdoughs were collected from different cities in Turkey at two different times and lactic acid bacteria (LAB) in the samples were identified with culture-independent and culture-dependent molecular methods. According to culture-dependent methodology, thirteen LAB species were identified. Lactobacillus spp. were identified as the major group according to MiSeq Illumina analysis. Technological potential of commonly isolated LAB species was evaluated. Due to high frequency of isolation, Fructilactobacillus sanfranciscensis and Lactiplantibacillus plantarum strains were better investigated for their technological traits useful in sourdough production. Experimental sourdoughs were produced with mono- and dual-culture of the selected strains and chemical properties and microbiological characteristics, as well as VOCs profile of the sourdoughs, were subjected to multivariate analysis which showed the relevance of added starter, in terms of acidification and VOCs profile.

The influence of backslopping on lactic acid bacteria diversity in tarhana fermentation

Tarhana is produced at batch systems in which the microbiota has changed accordingly to the microbial load from ingredients. In order to stabilize the microbiota, the effects of backslopping carried out under different temperature regimes (25 and 30 °C), pH (3.70 and 4.00) and inoculation rates (5, 10 and 15%) on lactic acid bacteria (LAB) diversity were determined in tarhana dough. LAB and Total Aerobic Mesophilic Bacteria (TAMB) numbers increased in all tarhana dough samples subjected to backslopping. Temperature and pH significantly affected the microbiological diversity of tarhana whereas the different inoculation rates did not. Tarhana dough showed complex tarhana microbiota following backslopping at pH 4.00 independently on the temperature applied. When backslopping was carried out at pH 3.70 and 25 °C, tarhana microbiota stabilized and became steady after several cycles. The LAB species found in all dough samples after the final backslopping were Lactobacillus plantarum, Lactobacillus alimentarius and Lactobacillus brevis which were able to carry out the fermentation in all conditions tested. In order to obtain a stable presence of LAB populations at industrial level for tarhana production, this work showed that backslopping is recommended at pH 3.70 and 25 °C with any inoculation ratios.

Characterization of Pediococcus acidilactici PFC69 and Lactococcus lactis PFC77 Bacteriocins and Their Antimicrobial Activities in Tarhana Fermentation

Tarhana is a traditional cereal product fermented by lactic acid bacteria (LAB) and yeast strains that has gained special interest recently as an infant nutrition. Tarhana contains wheat flour, yogurt, and various vegetables that might create a microbiological toxicological risk, especially for Bacillus cereus and Staphylococcus aureus. In this study, characterization of the metabolites responsible for antibacterial activity of Pediococcus acidilactici PFC69 and Lactococcus lactis PFC77 strains obtained from tarhana was performed, and antibacterial effects were detected against B. cereus ATCC 11778 and S. aureus ATCC 29213 during the fermentation. A total of 12,800 AU/mL antibacterial activity was observed for the supernatants of the PFC69 and PFC77 strains that were found to be stable at high temperature and in low pH conditions and sensitive to proteases, suggesting the antimicrobial metabolite is a bacteriocin. These bacteriocins were further purified and their molecular sizes were determined as 4.5 and 3.5 kDa, respectively. Importantly, inoculation of PFC69 and PFC77 to tarhana dough significantly decreased B. cereus ATCC 11778 and S. aureus ATCC 29213 amounts from the fifth day of fermentation compared to the control dough samples. P. acidilactici PFC69 and L. lactis PFC77 strains were concluded as bioprotective cultures for tarhana and these strains were offered for other cereal-based fermentations.

Biocontrol ability and action mechanisms of Aureobasidium pullulans GE17 and Meyerozyma guilliermondii KL3 against Penicillium digitatum DSM2750 and Penicillium expansum DSM62841 causing postharvest diseases

Epiphytic yeasts were isolated from different cultivars of apples and lemons and identified by a combination of PCR-RFLP of 5.8S rRNA region and sequencing of D1/D2 domain of the 26S rRNA gene. Among 69 isolates, Aureobasidium pullulans GE17 and Meyerozyma guilliermondii KL3 strains showed the greatest antagonistic activity against two significant apple and lemon postharvest pathogens, Penicillium expansum DSM62841 (blue mold) and Penicillium digitatum DSM2750 (green mold), after preliminary screening. Yeasts were applied as single and mixed cultures with two different cell concentrations of 10⁶ and 10⁸ cells/ml in the present study. It was determined that antagonistic activity of two yeast strains studied emerged with a combination of several mechanisms of action including competition for space and nutrients, production of volatile organic compounds (VOCs), secretion of extracellular lytic enzymes and inhibition of fungal spore germination. The highest inhibition of mycelial growth on P. expansum DSM62841 and P. digitatum DSM2750 (83.4% and 74.7%, respectively) was achieved by utilization of single culture of A. pullulans GE17. Otherwise, the application of mixed culture at the ratio of 10⁸ cells/ml inhibited spore germination of both pathogens from 86% to 95%. Results of this study suggest that an increase in yeast cell concentrations positively affected their biocontrol activity against blue and green molds. According to the results, employing single culture of M. guilliermondii KL3 did not exhibit effective antagonistic activity against blue and green molds. However, utilization of A. pullulans GE17 alone and mixed culture showed succesfull controlling against both P. expansum DSM62841 and P. digitatum DSM2750.

Structural and technological characterization of ropy exopolysaccharides produced by Lactobacillus plantarum strains isolated from Tarhana

Exopolysaccharide producing starter cultures enable manufacturing "clean labeled" foods with improved textural and nutritional properties. The structural and technological analyses were performed on the ropy exopolysaccharides of six Lactobacillus plantarum. The incubation temperature, time and pH affected the exopolysaccharide production and high exopolysaccharide was produced in the presence of sucrose and maltose. The viscosity of exopolysaccharide was high at acidic conditions except PFC311E that showed viscous at neutral pH. Lactobacillus plantarum strains produced between 120 and 400 mg/L exopolysaccharide in which the highest was observed at L. plantarum PFC311. Exoploysaccharides were degraded over 300 °C except PFC311E that degraded at 295.7 °C. The NMR analyses revealed that the exopolysaccharides were synthesized by α1-6, α1-3 and α1-4 bonds with glucose, galactose and fructose moieties. In conclusion, L. plantarum PFC311 produced ropy exopolysaccharide with different structural, rheological and thermal properties and reveals potential to be used in food industry.

The effect of fermentation time on the volatile aromatic profile of tarhana dough

Tarhana is a traditional food produced by fermentation of a dough prepared by mixing wheat flour, yoghurt, tomato, paprika, onion and mint. The fermentation of mixture of natural products gives the tarhana an aromatized desired food characteristic. Therefore, we aimed to determine the effects of fermentation time at home and commercial scale on the aromatic volatile profile of tarhana. In this respect, nine different tarhana dough samples were prepared at home and commercial scale and analysed for volatile and organic acid composition during fermentation which were then evaluated by principal component analysis. In all dough samples, the lactic, succinic and acetic acids were the most produced organic acids while the amounts of ketones decreased, and the alcohols, in particular the esters, increased within fermentation. Particularly, ethyl-lactate and ethyl-acetate increased significantly as well as ethyl-caprylate, ethyl-capronate and ethyl-hexanote responsible for fruity and flower flavour were also accumulated. Tarhana doughs were clustered in two main groups after five days of fermentation with principal component analysis and these clusters remained stable until the end of fermentation. As a conclusion, fermentation time determines the desirable tarhana by ensuring the formation of aromatic volatiles particularly esters. It is necessary to ferment tarhana for at least five days in order to obtain typical aromatic properties.

Lactobacillus plantarum with Functional Properties: An Approach to Increase Safety and Shelf-Life of Fermented Foods

Lactobacillus plantarum (widespread member of the genus Lactobacillus) is one of the most studied species extensively used in food industry as probiotic microorganism and/or microbial starter. The exploitation of Lb. plantarum strains with their long history in food fermentation forms an emerging field and design of added-value foods. Lb. plantarum strains were also used to produce new functional (traditional/novel) foods and beverages with improved nutritional and technological features. Lb. plantarum strains were identified from many traditional foods and characterized for their systematics and molecular taxonomy, enzyme systems (α-amylase, esterase, lipase, α-glucosidase, β-glucosidase, enolase, phosphoketolase, lactase dehydrogenase, etc.), and bioactive compounds (bacteriocin, dipeptides, and other preservative compounds). This review emphasizes that the Lb. plantarum strains with their probiotic properties can have great effects against harmful microflora (foodborne pathogens) to increase safety and shelf-life of fermented foods.

Evaluation of microbial consortia and chemical changes in spontaneous maize bran fermentation

Sustainable exploitation of agro-industrial by-products has attracted great interest in cereal bran valorization. In this research, a polyphasic approach has been carried out to characterize maize bran at microbiological and chemical level during a sourdough like fermentation process, in order to enhance its technological and nutritional properties. Autochthonous microbiota was isolated at different refreshment steps and subjected to identification and molecular characterization. Fermentation was characterized by a rapid increase in lactic acid bacteria and yeasts, with a co-dominance, at the initial stage, of Weissella spp., Pediococcus spp. and Wickerhamomyces anomalus. At the end of the fermentation, a natural selection was produced, with the prevalence of Lactobacillus plantarum, Lactobacillus brevis and Kazachstania unispora. This is the first time that a specific association between LAB and yeasts is reported, during the maize bran fermentation process. Enzymatic activities related to this microbial consortium promoted a "destructuration" of the fiber fraction, an increase in soluble dietary fiber and a reduction of phytic acid content. Our data also evidenced a noticeable increment in ferulic acid. The results obtained indicate that fermentation processes represent an efficient biotechnological approach to increase nutritional and functional potential of maize bran. Moreover, the characterization of microbiota involved in natural fermentation process will allow the selection of specific biotypes, with appropriate metabolic and enzymatic activities, to conduct "tailored" fermentation processes and improve brans or whole-meal flours from both nutritional and technological points of view.

Composition of volatile aromatic compounds and minerals of tarhana enriched with cherry laurel (Laurocerasus officinalis)

Different concentrations of cherry laurel pulp (0, 5, 10, 15 and 20%) were used to produce tarhana samples. Volatile aromatic compounds and minor mineral content were investigated. Volatile aromatic compounds were analyzed by using GC-MS with SPME fiber and minor mineral values were evaluated with inductively coupled plasma optical emission spectrometer. The statistical analysis showed that addition of pulp affected volatile aromatic compounds and minor mineral content significantly. Thirty five volatile aromatic compounds were found in tarhana samples. The octanoic acid from acids, benzaldehyde (CAS) phenylmethanal from aldehydes, 6-methyl-5-hepten-2-one from ketones, octadecane (CAS) n-octadecane form terpenes, ethyl caprylate from esters and benzenemethanol (CAS) benzyl alcohol from alcohols had the highest percentage of volatile aromatic compounds. Tarhana samples were rich source of Mn, Cu and Fe content.

Comparison of lactic acid bacteria diversity during the fermentation of Tarhana produced at home and on a commercial scale

In this study, lactic acid bacteria diversity during the fermentation of homemade and commercially prepared Tarhana, a traditional fermented cereal food from Anatolia, was determined and compared. The isolates collected from Tarhana dough were differentiated according to their (GTG)₅ profiles and then identified using 16S rDNA and pheS gene sequences. The variation of lactic acid bacteria during fermentation was also screened using PCR-DGGE. Commercially prepared Tarhana dough was fermented with higher Lactobacillus spp. diversity than homemade Tarhana dough. Lactobacillus casei, L. alimentarius, L. fabifermentas, and L. paralimentarius were identified differently from the fermentation of commercially prepared Tarhana dough. PCR-DGGE analysis revealed that L. plantarum was the main strain for homemade Tarhana, whereas L. brevis and L. alimentarius were observed in commercially prepared Tarhana dough fermentation. In conclusion, L. plantarum, L. brevis and L. alimentarius can be useful as a potential starter culture for the industrial production of Tarhana.

The Impact of Different Lactic Acid Bacteria Sourdoughs on the Quality Characteristics of Toast Bread

The effect of sourdough inoculated with three novel single strains of lactic acid bacteria (LAB) (Lactobacillus casei jQ412732, Lactobacillus plantarum jQ301799, and Lactobacillus brevis IBRC-M10790) as well as mixed strains was evaluated on the quality characteristics of Toast bread. Antifungal properties of sourdoughs due to organic acid production were measured by HPLC, and storability was evaluated by thermal and textural analysis in days 1, 3, and 6. Despite the impact of sourdough concentration on microbial preservation, no significant effect was observed in the case of enthalpy reduction. Mixed LAB strains showed the best results in reducing the enthalpy and hardness of bread as well as better microbial preservation by producing the highest amount of organic acids, justified by sensory panelists. Among single strains, L. casei gave better results in reducing hardness and staling rate of bread. Scanning Electron Microscopy micrographs of bread also showed the differences.

Microbial, chemical and sensory properties of shalgams made using different production methods

BACKGROUND

Shalgam is a traditional Turkish lactic acid fermented beverage. This study examined the microbial, chemical and sensory characteristics of shalgams produced by various methods.

RESULTS

Different production methods using traditional method (dough fermentation and carrot fermentation), direct method (without dough fermentation) and with the addition of starter cultures were applied to produce shalgams. The final amounts of total acidity as lactic acid (6.33-9.22 g L(-1)), pH (3.42-3.55), the counts of lactic acid bacteria (7.43-7.74 log CFU mL(-1)), total mesophilic aerobic bacteria (7.03-7.46 log CFU mL(-1)), yeasts (6.96-7.50 log CFU mL(-1)) and non-Saccharomyces yeasts (4.21-5.19 log CFU mL(-1) ) were found. Lactobacillus plantarum and then Lb. buchneri were the most frequently isolated bacteria in shalgam samples. Sensory evaluation of shalgams showed that sample produced using traditional method with starter additions obtained highest scores.

CONCLUSION

This study showed that addition of starter lactic acid bacteria cultures improved the quality of shalgams. Analysis of the results indicated that the direct method for the production of shalgam is not preferable. The data obtained can be useful for industrial shalgam producers.

Determination of mould and aflatoxin contamination in tarhana, a Turkish fermented food

Tarhana is a popular traditional Turkish cereal-based fermented food product mainly produced at home or at home-scale level. Some certain mould species can grow even at low moisture and pH values and produce aflatoxins in food. This study was conducted to determine aflatoksin levels in tarhana. For this purpose, a total of 138 tarhana powder samples were collected from bazaars in Istanbul and analyzed for aflatoxins, mould contamination, and some physco-chemical parameters. As a result, 32 out of 138 tarhana samples (23.2%) were found to be contaminated with aflatoxins in the range of 0.7–16.8 μg/kg, whereas 29 samples contained Aflatoxin B1 (AFB1) ranging from 0.2–13.2 μg/kg. All samples (100%) contaminated with moulds in the range of 1.4 × 10¹ –5.8 × 10⁷cfu/g. The average pH, moisture and a_w results were detected as 3.82, 12.71%, and 0.695, respectively.