Effects of fermentation time and storage on the water‐soluble vitamin contents of tarhana

Changes in water‐soluble vitamins were investigated in tarhana dough during fermentation and in tarhana stored under a variety of conditions for up to 6 months. The contents of riboflavin (P < 0.01), thiamin, niacin, vitamin B₆ and folic acid (P < 0.05) increased significantly during fermentation. The thiamin, riboflavin, niacin, vitamin B₆ and folic acid contents of tarhana dough were 4.80, 1.85, 7.68, 15.30 and 2.25 mg kg^?1 respectively at the beginning of fermentation and increased to 10.15, 5.15, 24.04, 19.35 and 6.10 mg kg^?1 respectively at the end of fermentation. Thiamin, riboflavin and folic acid contents were significantly affected (P < 0.01) by storage type and period, but niacin and vitamin B₆ contents were not affected (P > 0.05). The water‐soluble vitamin contents of tarhana stored wet were higher than those of tarhana stored dry. Drying resulted in a 24% reduction in riboflavin content and an 86% reduction in folic acid content. Copyright © 2007 Society of Chemical Industry     

腐乳源酵母分离鉴定及其极性脂质分析

从豆腐酸浆及毛坯中鉴定了23个分离菌株,测定了其脂肪酶酶活并利用超高效液相串联质谱对其中7个菌株的脂质进行了分析。结果表明,指纹图谱中包含2种鞘氨醇、16种酰胺、22种酯类和3种脂肪酸。其中,马克斯克鲁维酵母SP-1和挪威毕赤酵母SP-5中植物鞘氨醇、N,N-二甲基鞘氨醇的相对含量最高。此外,嗜酒假丝酵母ATW-1、库德里阿兹威毕赤氏酵母SP-4和阿米塞毕赤氏酵母Y的酯类化合物比较丰富,且其细胞结合型脂肪酶酶活力也比较高,PCA分析进一步表明这3个菌株脂质组成具有较大的相似性,表明酵母菌中丰富的代谢酯类物质可能与细胞结合型脂肪酶之间存在密切联系。     

Effect of sourdough starter and fungal proteases on gluten content and sensory properties of tarhana

In this study, gluten degradation during prolonged tarhana fermentation was monitored in a traditional dough as well as in dough containing sourdough starter, peptidase additives and combination of both. Gluten content, determined using the sandwich ELISA assay method, was reduced significantly in the first 5 days of fermentation for all formulations. After 30 days into fermentation, approximately 15% and 20% reduction of gluten was observed in the traditional dough and sourdough starter added dough, respectively. In enzyme supplemented formulations, the mean gluten levels were below 20 ppm by 20 days of fermentation. Results showed that proteolytic enzyme addition to the dough mix can potentially render long fermented tarhana a food which conforms to regulations set forth for gluten-free foods, even though wheat flour is one of the main production ingredients. Sensory evaluation of the 30 day fermented tarhana samples revealed differences in sourness and odour properties of the products.     

Characterization of Osmotolerant Yeasts and Yeast‐Like Molds from Apple Orchards and Apple Juice Processing Plants in China and Investigation of Their Spoilage Potential

Yeasts and yeast‐like fungal isolates were recovered from apple orchards and apple juice processing plants located in the Shaanxi province of China. The strains were evaluated for osmotolerance by growing them in 50% (w/v) glucose. Of the strains tested, 66 were positive for osmotolerance and were subsequently identified by 26S or 5.8S‐ITS ribosomal RNA (rRNA) gene sequencing. Physiological tests and RAPD‐PCR analysis were performed to reveal the polymorphism of isolates belonging to the same species. Further, the spoilage potential of the 66 isolates was determining by evaluating their growth in 50% to 70% (w/v) glucose and measuring gas generation in 50% (w/v) glucose. Thirteen osmotolerant isolates representing 9 species were obtained from 10 apple orchards and 53 target isolates representing 19 species were recovered from 2 apple juice processing plants. In total, members of 14 genera and 23 species of osmotolerant isolates including yeast‐like molds were recovered from all sources. The commonly recovered osmotolerant isolates belonged to Kluyveromyces marxianus, Hanseniaspora uvarum, Saccharomyces cerevisiae, Zygosaccharomyces rouxii, Candida tropicalis, and Pichia kudriavzevii. The polymorphism of isolates belonging to the same species was limited to 1 to 3 biotypes. The majority of species were capable of growing within a range of glucose concentration, similar to sugar concentrations found in apple juice products with a lag phase from 96 to 192 h. Overall, Z. rouxii was particularly the most tolerant to high glucose concentration with the shortest lag phase of 48 h in 70% (w/v) glucose and the fastest gas generation rate in 50% (w/v) glucose.     

Influencing cocoa flavour using Pichia kluyveri and Kluyveromyces marxianus in a defined mixed starter culture for cocoa fermentation

The potential impact of aromatic and pectinolytic yeasts on cocoa flavour was investigated using two defined mixed starter cultures encompassing strains of Pichia kluyveri and Kluyveromyces marxianus for inoculating cocoa beans in small scale tray fermentations. Samples for microbial and metabolite analysis were collected at 12–24 hour intervals during 120 h of fermentation. Yeast isolates were grouped by (GTG)₅-based rep-PCR fingerprinting and identified by sequencing of the D1/D2 region of the 26S rRNA gene and the actin gene. Pulsed Field Gel Electrophoresis (PFGE) was conducted on isolates belonging to the species P. kluyveri and K. marxianus to verify strain level identity with the inoculated strains. Furthermore, Denaturing Gradient Gel Electrophoresis (DGGE) was performed to follow yeast and bacterial dynamics over time including the presence of the bacterial inoculum consisting of Lactobacillus fermentum and Acetobacter pasteurianus. Yeast cell counts peaked after 12 h of fermentation with the predominant species being identified as Hanseniaspora opuntiae and Hanseniaspora thailandica. P. kluyveri and K. marxianus were found to compose 9.3% and 13.5% of the yeast population, respectively, after 12 h of fermentation whilst PFGE showed that ~ 88% of all P. kluyveri isolates and 100% of all K. marxianus isolates were identical to the inoculated strains. Despite never being the dominant yeast species at any stage of fermentation, the un-conched chocolates produced from the two inoculated fermentations were judged by sensory analysis to differ in flavour profile compared to the spontaneously fermented control. This could indicate that yeasts have a greater impact on the sensory qualities of cocoa than previously assumed.     

A Traditional Turkish Fermented Cereal Food: Tarhana

Tarhana has a long history. According to historical records, it was first produced by Turkish people in Middle Asia and afterwards it spread out to different parts of the world. It is a fermented cereal-based food and can be simply defined as a mixture of yoghurt, cereal flours, yeast, different vegetables, herbs, and spices. After the mixing process, tarhana dough is fermented for 1 to 5 days and immediately dried. Both lactic acid bacteria (LAB) and yeast fermentations occur simultaneously during tarhana production. Therefore, tarhana has sour and acidic taste with yeast flavour as well. It is sun-dried at the home-made level or oven-dried of the commercial level. Several types of tarhana can be classified depending upon processing method or raw materials used. Low moisture (6–10%), low pH (3.5–5.0), and components (organic acids, bacteriosin, etc.) formed in fermentation have bacteriostatic effect on pathogens and spoilage microorganisms during long term storage (1–2 years) and enhance shelf life. Since tarhana is a good source of B vitamins, minerals, organic acids, and free amino acids, and since it is a product of LAB and yeast fermentation, it may be considered a functional and probiotic food.     

Comparison of lactic acid contents between dried and frozen tarhana

The lactic acid content of tarhana produced with different dough treatments was determined. Trials were performed to see the effects of different parameters on organic acid produced during fermentation. In these trials, fermentation time, yogurt content and preservation method parameters were varied. Increasing fermentation time had a significant effect on lactic acid formation as well as total organic acid content of tarhana (p < 0.01). In the samples of tarhana with 50% yogurt, total acidity increased 29.9% in the first 48 h of fermentation. During the subsequent 48 h the increase was only 3.6%. Lactic acid increased 17.7% during the first 48 h followed by an increase of 3.1% during the next 48 h of fermentation in these same samples. On the other hand, when yogurt content was increased from 50% to 75%, total acidity in the first 48 h was 17.0% greater than the samples with 50% yogurt. There was also a 20.2% increase in lactic acid as well.     

Effect of Select Parameters of the Sourdough Rye Fermentation on the Activity of Some Mixed Starter Cultures

The effect of select parameters (i.e., rye flour ash content, temperature, and dough yield) of the sourdough fermentation on the fermentation activity of different starter cultures (lactic acid bacteria Lactococcus lactis ssp. Lactis, Weissella confusa, Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus helveticus, and yeast Kluyveromyces marxianus subsp. Marxianus) was determined. The major metabolic end products of fermentation (D, L-lactic acid, acetic acid, ethanol and glycerol) and the evolution of total phenolic content and folic acid during bread making were measured. Lactobacillus helveticus and Kluyveromyces marxianus allowed obtaining sourdoughs with the highest lactic acid/acetic acid ratios. The mixed starter culture with Lactococcus lactis and Saccharomyces cerevisiae generated the most important quantities of D/L lactic acid. The maximum values of ethanol concentration were obtained in case of the sourdoughs from whole rye flour fermented at lower temperature (30°C) with mixed starter cultures containing Sacchomyces cerevisiae. The fermentation process and type of starter culture are also tools to increase the bioactive compounds, enabling the increase of the phenolic content of the sourdough.     

Probiotic potential of Saccharomyces cerevisiae and Kluyveromyces marxianus isolated from West African spontaneously fermented cereal and milk products

The yeast species Saccharomyces cerevisiae and Kluyveromyces marxianus are associated with fermentation of West African indigenous foods. The aim of this study was to characterize potential probiotic properties of S. cerevisiae and K. marxianus isolates from the West African milk products lait caillé and nunu and a cereal-based product mawè. The strains (14 in total) were identified by 26S rRNA gene sequencing and characterized for survival at gastrointestinal stress (bile salts and low pH) and adhesion to Caco-2 intestinal epithelial cells. Selected yeast isolates were tested for their effect on the transepithelial electrical resistance (TEER), using the intestinal epithelial cell line Caco-2 and for maintenance of intracellular pH (pH_i) during perfusion with gastrointestinal pH (3.5 and 6.5). All tested yeasts were able to grow in bile salts in a strain-dependent manner, exhibiting a maximum specific growth rate (μ_max) of 0.58–1.50 h⁻¹. At pH 2.5, slow growth was observed for the isolates from mawè (μ_max of 0.06–0.80 h⁻¹), whereas growth of yeasts from other sources was mostly inhibited. Yeast adhesion to Caco-2 cells was strain specific and varied between 8.0% and 36.2%. Selected strains of S. cerevisiae and K. marxianus were able to maintain the pH_i homeostasis at gastrointestinal pH and to increase TEER across the Caco-2 monolayers, indicating their potential to improve intestinal barrier functions. Based on overall results, strains of K. marxianus and S. cerevisiae from mawè exhibited the highest probiotic potential and might be recommended for further development as starter cultures in West African fermented products.     

A Traditional Turkish Fermented Cereal Food: Tarhana

Tarhana has a long history. According to historical records, it was first produced by Turkish people in Middle Asia and afterwards it spread out to different parts of the world. It is a fermented cereal-based food and can be simply defined as a mixture of yoghurt, cereal flours, yeast, different vegetables, herbs, and spices. After the mixing process, tarhana dough is fermented for 1 to 5 days and immediately dried. Both lactic acid bacteria (LAB) and yeast fermentations occur simultaneously during tarhana production. Therefore, tarhana has sour and acidic taste with yeast flavour as well. It is sun-dried at the home-made level or oven-dried of the commercial level. Several types of tarhana can be classified depending upon processing method or raw materials used. Low moisture (6-10%), low pH (3.5-5.0), and components (organic acids, bacteriosin, etc.) formed in fermentation have bacteriostatic effect on pathogens and spoilage microorganisms during long term storage (1-2 years) and enhance shelf life. Since tarhana is a good source of B vitamins, minerals, organic acids, and free amino acids, and since it is a product of LAB and yeast fermentation, it may be considered a functional and probiotic food.     

Tarhana as a traditional Turkish fermented cereal food. Its recipe, production and composition

As a fermented product tarhana is the dry form of yogurt-cereal mixture and represents an important part of the diets of many people in Turkey. It is prepared by mixing wheat flour, yogurt, yeast and a variety of cooked vegetables (tomatoes, onions, green pepper etc.), salt, and spices (mint, paprika) followed by fermentation for one to seven days. Generally one part yogurt is mixed with two parts of wheat flour (w/w). In commercial production there are two methods for tarhana making. First method is called straight method and ingredients in the recipe is mixed and kneaded, fermented, dried and finally sieved. Second method is called sour dough method that contains three steps, each one has a different recipe. Throughout fermentation lactic acid bacteria and yeast give the characteristic taste and flavour of tarhana by producing lactic acid, ethanol, carbondioxide and some other organic compounds. Organic acids composed in fermentation period lower the pH (3.4-4.2), and low moisture content (6-10%) is a poor medium for pathogens and spoilage organisms. The nutrient content of tarhana depends upon yogurt and flour ratios as well as some other ingredients, and it is also considered to be a useful high-protein dietary supplement with average 15% protein content. Addition of set yogurt due to high dry matter content and baker's yeast increase protein content and enhances it's amino acid composition.     

Production of Bioingredients from Kluyveromyces marxianus Grown on Whey: An Alternative

Whey waste is a major problem for the dairy industry. Finding alternative means to reduce its pollution potential and produce high value-added bioingredients has been attempted by many researchers. Kluyveromyces marxianus var. marxianus is a dairy yeast that produces β-galactosidase, allowing for whey fermentation. Also, K. marxianus has been proposed as a source of: (1) oligonucleotides, used as flavor enhancers in food products; (2) oligosaccharides, used as prebiotics to stimulate the growth of Bifidobacterium sp. in the animal and human intestines; and (3) oligopeptides, immunostimulators added to dairy products that are released in the wort after whey protein proteolysis. Fed-batch fermentation can be used as an alternative process to avoid increases in lactose concentration and prevent the catabolite repression of the respiratory enzyme synthesis during aerobic fermentation, thus allowing for high biomass yields. The relevance of these factors on yeast fermentation of whey is summarized in this critical review.     

Effect of different ingredients on the fermentation activity in tarhana

Tarhana is a fermented wheat flour–yoghurt mixture which is widely consumed in Turkey. Baker's yeast is also involved in the fermentation. In this study, fermentation activity of tarhana was investigated by monitoring the lactic acid bacteria and yeast population when the level of salt and amount of yoghurt used were varied. Fermentation activity was high during the first day of fermentation. Microbial counts dropped below the initial counts at the end of a 4-day fermentation. Fermentation activity of tarhana prepared without salt was found to be higher than the tarhana samples prepared with salt.     

Viability and Performance of Pure Yeast Strains in Frozen Wheat Dough

Freezing and subsequent storage of wheat doughs containing Saccharomyces cerevisiae, S. fructuum or Candida boidinii after undergoing a bulk fermentation step, reduced the viability of yeasts, depending on the species. Freezing and storage of doughs without bulk fermentation had no effect on viability. Gassing power was affected most by frozen storage, depending on storage time and species. Changes in acidification capability were small, and only significant for total titratable acidity. Changes in sugars and leavening were closely related. Results showed that the use of less active yeast species (S. fructuum), with high freezing tolerance in frozen dough processes would be of practical interest.     

Microbiology and biochemistry of natural fermentation of coconut palm sap

The micro-organisms appearing during natural fermentation of coconut sap were identified and the physical and chemical changes occuring in the sap were studied by analysing samples collected at intervals of time during the traditional fermentation process.A total of 166 isolates of yeasts and 39 isolates of bacteria were identified. Seventeen species of yeasts belonging to eight genera were recorded. The largest number of isolates (72%) belonged to genera Candida, Pichia and Saccharomyces. Saccharomyces chevalieri was the most dominant yeast species and accounted for 35% of the total isolates. Seven genera of bacteria were isolated. The predominant Genera was Bacillus. Others included Enterobacter, Leuconostoc, Micrococcus and Lactobacillus.The major physical, chemical and microbiological changes occurring in the fermenting sap indicated that a natural fermentation of coconut sap consist of an initial lactic acid fermentation, a middle alcoholic fermentation and a final acetic acid fermentation. It also appeared that activities brought about by micro-organisms of early phase helped the activities of the micro-organisms in each of the later phases.     

Influence of starter culture combinations of<Emphasis Type="Italic"> Lactobacillus fermentum</Emphasis>,<Emphasis Type="Italic"> Saccharomyces cerevisiae</Emphasis> and<Emphasis Type="Italic"> Candida krusei</Emphasis> on aroma in Ghanaian maize dough fermentation

Various combinations of Lactobacillus fermentum, Saccharomyces cerevisiae and Candida krusei were investigated as starter cultures for the fermentation of the Ghanaian maize dough. The four combinations used were each yeast species with L. fermentum, both yeast species together, and both yeast species together with L. fermentum. Maize dough fermented spontaneously was also used as control. The aroma profile, acidity values and sensory characteristics of all dough samples were compared. Using Principal Component Analysis (PCA), the aroma profiles of the dough samples could be separated into five distinct groups based on the type of fermentation. Fermentations where S. cerevisiae and C. krusei were combined produced the highest concentrations of aroma compounds, particularly esters, but were judged as having the lowest acceptability scores. A more balanced profile that included alcohols, carbonyls, esters and acids was obtained with the combination of L. fermentum and C. krusei, which produced fermented dough with a high sensory score comparable to spontaneous fermentations. Combinations of L. fermentum and S. cerevisiae produced high concentrations of ethanol and fusel alcohols. Lactic and acetic acid concentrations were highest with the combined use of all three starter cultures.     

Selection and molecular characterization of wine yeasts isolated from the ‘El Penedès’ area (Spain)

A study of the microbiota present during the wine fermentation of five grape varieties from the ‘El Penedès’ area (Spain) was carried out to select autochthonous yeast strains for industrial wine production. In this study we identified members of the genera Candida, Dekkera, Hanseniaspora, Kluyveromyces, Torulaspora, Zygosaccharomyces and Saccharomyces in wine fermentation microbiota. Strains of Saccharomyces cerevisiae, as responsible agents of the alcoholic fermentation, were considered for a selection protocol. In this work we applied different enological criteria for selection, but previously we have characterized and differentiated Saccharomyces isolates by molecular methods to reduce the number of strains to analyse. Three strains were selected to conduct fermentations according to their characteristics. Finally, using mitochondrial DNA restriction analysis we demonstrated that the autochthonous selected strains are important contributors to the wine fermentation.     

Optimization of Tannase Production and Improvement of Nutritional Quality of Two Potential Low-Priced Plant Feedstuffs under Solid State Fermentation by Pichia kudriavzevii Isolated from Fish Gut

An autochthonous tannase yielding yeast strain Pichia kudriavzevii (GU939629), isolated from the gut of an Indian major carp (mrigal), Cirrhinus cirrhosus, has been used for extracellular tannase production and subsequent processing of two plant feedstuffs, Groundnut oil cake (GOC) and Pistia leaves (PL), under solid state fermentation (SSF). Of the two plant materials studied, GOC supported maximum tannase activity (0.82 ± 0.024 U/gds) degrading 94.1% of the initial tannin content, whereas SSF resulted in 0.68 ± 0.02 U/gds tannase activity and 89.1% tannin degradation through the use of PL as substrate. Following SSF for 15 d with optimized culture conditions, analysis of proximate composition revealed that there was significant increase (t-value significant at P < 0.05) in the contents of crude protein, lipid, minerals (Na, K, Ca, Mg, Zn, Fe, Cu, Mn, P), free amino acids and fatty acids; along with reduction in the contents of the other antinutritional factors, for example, crude fiber, phytic acid, and trypsin inhibitor. The results indicate that there is ample scope for further research to appraise potential application of gut microbiota for tannase production, as well as processing of low-cost plant feedstuffs for prospective use as feed ingredients for improved fish protein production.     

Identification of yeasts and evaluation of their distribution in Taiwanese Kefir and Viili starters

The objective of the present study was to investigate yeast communities in kefir grains and viili starters in Taiwan through conventional microbiological cultivation and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The DNA sequencing was used as a validity technique to ensure that all isolates within each group belonged to just one species, and to confirm the identified results of PCR-DGGE. Results indicated that a combination of conventional microbiological cultivation with PCR-DGGE and sequencing could successfully identify 4 yeast species from both types of cultures in Taiwan. Kluyveromyces marxianus, Saccharomyces turicensis, and Pichia fermentans were found in Taiwanese kefir grains with a distribution of 76, 22, and 2%, respectively, whereas Klu. marxianus, Saccharomyces unisporus and P. fermentans were identified in viili starters corresponding to 58, 11, and 31% of the total cell counts, respectively. Furthermore, the culture-independent method was applied to identify the yeast species using DGGE. Only 2 yeast species, Klu. marxianus and S. turicensis, were found in kefir grains and 2, Klu. marxianus and P. fermentans, in viili starters. These results suggest that in samples containing multiple species, PCR-DGGE may fail to detect some species. Sequences of yeast isolates reported in this study have been deposited in the GenBank database under accession nos. DQ139802, AF398485, DQ377652, and AY007920.     

Biochemical characteristics,virulence traits and antifungal resistance of two major yeast species isolated from kefir: Kluyveromyces marxianus and Saccharomyces unisporus

Kefir yeasts were investigated for their possible virulence using an in vitro system. Unweighted pair group method with arithmetic mean (UPGMA) cluster analysis of 46 biochemical traits showed that all kefir isolates formed clusters distinct from Candida albicans. No isolate showed N‐acetylglucosaminidase activity, which is involved in resistance against host immune systems. All Kluyveromyces marxianus isolates formed pseudohyphae and grew at 42 °C, whereas Saccharomyces unisporus isolates did not. None of the kefir yeasts had proteolytic or haemolytic activities. All K. marxianus isolates were susceptible to fluconazole, whereas S. unisporus isolates were classified as resistant.