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.     

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.     

Diversity and Stability of Yeast Species During the Fermentation of Tarhana

Tarhana is a traditional cereal-based fermented food produced with a mixture of yoghurt and flour. The main microbiota in the fermentation of tarhana is yeast, together with lactic acid bacteria. In this study, the yeast microbiota of home-made tarhana (HMT) and plant-type tarhana (PTT) dough samples was evaluated and compared during fermentation. Culture-dependent LSU and ITS-5.8S rDNA sequence analysis of yeast isolates collected during the tarhana dough fermentation clarified 45 selected isolates representing different clusters. These yeast isolates displayed high homologywith species Pichia kudriavzevii (11), Candida glabrata (11), Candida humilis (10), Saccharomyces cerevisiae (7), Kluyveromyces marxianus (4), Kazachstania servazzi (1), and Kazachstania unispora (1). Additionally, both culture-dependent and PCR-Denaturated Gradient Gel Electrophoresis (PCR-DGGE) analyses showed that S. cerevisiae, P. kudriavzevii and K. marxianus were abundant in the fermentation of HMT dough samples whereas P. kudriavzevii, C. humilis, and C. glabrata dominated the PTT dough samples. It was concluded that tarhana fermentation was accomplished with the presence of a wide variety of yeast species that mainly included P. kudriavzevii in both HMT and PTT dough samples.     

酵母与乳酸菌的相互作用模式及其在发酵食品中的应用研究进展

酵母与乳酸菌作为被广泛应用的微生物在发酵食品的生产过程中起着举足轻重的作用,二者在发酵体系中的作用方式直接决定了产品的品质。研究发酵体系中酵母-乳酸菌间的相互作用模式有助于揭示微生物与食品功能的关系,对发酵进程的正向调控具有重要意义。本文综述了酵母与乳酸菌在发酵过程中发生的协同/拮抗作用、营养代谢产物交换、群体感应及生物膜包被等相互作用模式,探讨了酵母-乳酸菌相互作用对改善发酵食品风味质构、缩短发酵周期、提升产品益生特性等的积极作用。最后,对酵母-乳酸菌作为组合发酵剂进行强化发酵的应用前景进行了总结与展望。     

Analysis of improved nutritional composition of bee pollen (Brassica campestris L.) after different fermentation treatments

Microbial fermentation as an excellent food processing technology has been used for improving the flavour and nutritional feature of food material. In this study, we compared the differences in the nutrient profile of bee pollen (rape bee pollen, Brassica campestris L., BP) fermented with different species of microbes, such as lactic acid bacteria (LAB), yeast, and the two mixed. Based on the nutritional components and multivariate statistical analysis, yeast fermentation has more advantage for BP than fermentation with LAB or mixed microbes. The yeast-fermented BP has an 83.5% reduction in fructose and 87.4% reduction in glucose, while phenolic compounds, oligopeptides and fatty acids were increased by 9.3%, 68.8% and 18.2%, respectively, compared with the BP without fermentation. The contents of riboflavin, nicotinic acid, nicotinamide and free amino acids in the pollen fermented by yeast were 2.4, 39.6, 4.6 and 4.8 times higher than those in raw BP, respectively. Additionally, in the fermentation process, wall-breaking pollen showed more advantages in the transformation of nutrients, free amino acid increased by 11% at least, more low molecular weight peptides produced and nicotinic acid and nicotinamide increased by 7% at least, compared with fermented BP. Taken together, these results showed that BP with yeast fermentation has great potential in obtaining high available nutritional products.     

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.     

Antimicrobial activity of weak acids in liquid feed fermentations, and its effects on yeasts and lactic acid bacteria

BACKGROUND: The efficacy of weak organic acids in the control of yeasts in pig liquid feed was studied taking into account the effects on lactic acid bacteria (LAB) responsible for beneficial fermentation. RESULTS: The yeast population in pig liquid feed was taxonomically identified. Kazachstania exigua, Debaryomyces hansenii and Pichia deserticola dominated the fermentation in liquid feed and whey. Pichia deserticola was found in whey and foaming liquid feed and dominated the fermentation after incubation. The sensitivity of the isolates against weak acids was measured in culture medium as well as in fermented and non‐fermented liquid feed. Formic acid and potassium sorbate successfully reduced the growth of yeasts in all media without interfering with LAB development. Both of these organic acids showed an increased antifungal effect when used in liquid feed fermented by a Lactobacillus plantarum strain. CONCLUSION: The loss of energy, reduced palatability and other practical problems due to the high growth of yeasts in fermented liquid diets can be reduced by organic acids without affecting lactic acid fermentation. Copyright © 2011 Society of Chemical Industry     

Overview of Sourdough Technology: from Production to Marketing

Sourdough is a type of dough fermented by yeast and lactic acid bacteria (LAB) used as sponge dough in bread making. Sourdough may have four classifications according to the fermentation type and the technological process used. On sourdough type I, the fermentation of yeasts and LAB present in the flour occurs spontaneously whereas in type II, fermentation occurs after the inoculation of a starter culture. Type III is simply type II sourdough dehydrated and type IV is a mixture of type I and type II sourdough, produced on laboratory scale. With LAB’s growth during fermentation, pH decreases with subsequent hydrolysis of starch and protein, favoring the growth of yeasts. The yeast in turn, releases amino acids during autolysis, contributing to the growth of LAB. Due to this synergistic growth of LAB and yeasts, the products obtained from sourdough show more concentration of flavor, more elastic dough, and a longer shelf life than bread fermented only by yeast. Although, the benefits of this technology, using sourdough, is present just in a few countries, where it is also possible to obtain the dehydrated sourdough starters, for domestic use, in local supermarkets. Due to its fermentative process complexity, this paper presents updated information about the fabrication process of sourdough, main factors affecting this process, benefits of sourdough use for bakery products, and the varieties of dehydrated sourdough commercially available throughout the world.     

Analysis of organic acids in Chinese raisin tree (Hovenia dulcis) peduncle and their changes in liquid fermentation process

Chinese raisin tree (Hovenia dulcis) peduncle is a wonderful food material for fermented food for high contents of sugars and a variety of organic acids. The organic acids in the fresh peduncle, fermented wine, and vinegar were identified and quantified by HPLC, and changes in biochemical parameters and organic acids in the fermentation process were studied. Skin-on fermentation was carried out in the alcoholic fermentation, and 9 identified organic acids fluctuated by physical or biochemical reactions during the alcoholic fermentation. Submerged fermentation was carried out in the acetic fermentation. It took 72 h to finish the 1^st cycle of acetification with the titratable acidity 5.42%(w/v), and 30 h to finish the 2^nd cycle. The contents of acetic acid, formic acid, and α-ketoglutaric acid increased, while the rest identified organic acids decreased in the acetification process. The fermentation developed in this study appeared to be a practical processing method for Chinese raisin tree peduncles.     

原汁苹果醋中的有机酸

以苹果汁为原料 ,采用液态酒精发酵和醋酸发酵法制作苹果醋 ,采用反相高效液相色谱法分析苹果醋中有机酸 ,研究了苹果品种、醋酸菌种、醋酸发酵方法及过程对有机酸的影响。认为苹果酸是苹果醋中的主要有机果酸 ,其与液态粮食醋有机酸组成的差别主要体现在苹果酸、酒石酸和乳酸的含量上 ,苹果品种是影响原汁苹果醋中有机酸的种类和含量主要因素 ,醋酸菌在醋酸发酵过程中有代谢各种有机酸的作用 ,发酵方法会影响醋酸菌对有机酸代谢作用的程度 ,试验中所采用的 5种醋酸菌在醋酸发酵过程中通过消耗苹果酸、乳酸、琥珀酸 ,而产生和积累柠檬酸。     

Oxidative Stability of Lipids Rich in EPA and DHA Extracted from Fermented Scallop Ovary

A novel seafood paste was developed by the fermentation of scallop ovary using rice malt (koji) and yeast culture. Chemical analysis of the product showed the formation of high level of free amino acids and organic acids during the fermentation. The product color and flavor resembled to Japanese traditional soybean miso. The contents of total lipids (TLs) extracted from the fermented products were ranged from 9.18% to 11.59% or 11.38% to 13.57%/dry sample weight. Although the TL was rich in oxidatively unstable polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), little decrease was found in these PUFAs during the fermentation, showing the high oxidative stability of the TL from the fermented scallop ovary. Moreover, the oxidative stability of the TL extracted from the fermented products increased with increasing the fermentation time. This would be mainly due to the formation of lipid soluble antioxidants such as tocopherols, which might be derived from yeast used for fermentation.     

Improving the quality of Sichuan pickle by adding a traditional Chinese medicinal herb Lycium barbarum in its fermentation

Sichuan pickle is a traditional Chinese food fermented mainly by lactic acid bacteria (LAB). In this study, effect of adding Lycium barbarum on Sichuan pickle fermentation was investigated using kinetic modelling and correlation analysis. It was found that L. barbarum addition not only increased the amount of LAB, the total acid content and antioxidant capacity, but also improved the organoleptic quality and reduced nitrite content of the pickle considerably. Model‐based analyses revealed that L. barbarum addition increased the growth rate and decreased the death rate of LAB. The increase in antioxidant capacity of the pickle, especially the phenolics, can at least partly be attributed to its transferring from the L. barbarum. Correlation analysis results suggest that the nitrite reduction in pickle is closely related with pH value decrease and the increase in acids, and LAB, yeast and acids may all make contribution to the antioxidant capacity of the pickle.     

CHEMICAL COMPOSITIONS OF TRADITIONAL TARHANA HAVING DIFFERENT FORMULATIONS

Cereal‐based fermented foods play an important role in the diets of many people in Asia, Africa, the Middle East and some parts of Europe. Containing cereal and animal‐based nutrients, richer with fermentation products, produced with yeast and lactic acid bacteria, tarhana is a type of soup having a delicious and desired taste. It is a good source of protein and vitamins and therefore is used largely for feeding children and the elderly. Because there is no standard production method, the nutritional properties of tarhana strictly depend on ingredients and their ratios in the formulation. In this research, the compositions of 21 tarhana samples collected from different locations in Turkey were examined. Moisture, ash, salt, protein, crude fat, acidity degree and reducing sugar values of the samples changed between 9.35 and 66.4, 1.36 and 9.40, 0.62 and 9.01, 6.77 and 28.55, 0.43 and 15.78, 1.7 and 40.7, and 0.22 and 1.85%, respectively. The nutritional importance of tarhana is the improvement of the basic cereal protein diet by adding dairy protein in a highly accepted form. Like tarhana, indigenous fermented foods that enhance health properties should receive much more attention that they deserve.     

不同酵母菌株发酵蓝莓酒有机酸的动态变化研究

试验以野生蓝莓为原料,利用不同酵母菌株发酵生产蓝莓酒,采用高效液相色谱(high-performance liquid chromatography,HPLC)法测定9种有机酸在发酵过程中的含量变化。结果显示,不同酵母菌株发酵过程中9种有机酸的含量有着明显的差异,且发酵各个阶段的9种有机酸的总含量变化趋势也有所不同。前发酵结束时,3株菌发酵的蓝莓酒体中9种有机酸含量均高于初始发酵醪液,其中GF3最高,为初始发酵醪液的6倍~7倍,T1、FK3-2非常接近,为初始发酵醪液的3倍左右。后发酵结束时,T1和FK3-2发酵的酒体中有机酸含量几乎没有差别,而GF3发酵酒体中有机酸含量最高,是其他两株菌株的两倍以上。3株菌株后发酵结束时酒体中9种有机酸的含量均比初始发酵醪液高,且均低于主发酵结束时的含量。     

Isolation and characterization of lactic acid bacteria from jiang‐sun (fermented bamboo shoots), a traditional fermented food in Taiwan

BACKGROUND: In this study, lactic acid bacteria (LAB) were isolated, characterized and identified from jiang‐sun (fermented bamboo shoots; a traditional fermented food in Taiwan). Samples were collected at seven time intervals from a fixed fermenting bucket during the fermentation process of jiang‐sun and its initial ingredients, dochi (fermented soybeans) and bamboo shoots. RESULTS: A total of 57 LAB cultures were isolated; 42 cultures were isolated from jiang‐sun samples and 15 cultures were isolated from dochi and bamboo shoots. These isolates were characterized phenotypically and then divided into three groups (A–C) by restriction fragment length polymorphism analysis and sequencing of 16S ribosomal DNA. Alteration of microbial populations during the fermentation process was observed. While various LAB were found in the dochi and bamboo shoots, it was mostly replaced by Lactobacillus plantarum after 1 day of fermentation. Furthermore, the antibacterial activities of the isolates were determined, and one Enterococcus faecium strain showed inhibitory activity against all the indicator strains. CONCLUSION: Results suggest that L. plantarum is the main LAB present during the fermentation of jiang‐sun. To our knowledge, this is the first report describing the distribution and varieties of LAB that exist in the jiang‐sun fermentation process. Copyright © 2010 Society of Chemical Industry     

Evolution of fermenting microbiota in tarhana produced under controlled technological conditions

The purpose of this study was to evaluate the evolution of lactic acid bacteria (LAB) and yeasts during the fermentation of tarhana produced with some pasteurised ingredients and carried out at 30 and 40 °C. The chemical parameters were those typical for tarhana production. Coliform bacteria were not detected during fermentation, while LAB and yeasts were in the range 10⁷-10⁸ colony forming units (CFU) g⁻¹. Plate counts showed an optimal development of both fermenting microbial groups and the differences in cell concentrations were not significant (P > 0.05). LAB were isolated during fermentation and grouped on the basis of phenotypic and polymorphic characteristics. LAB isolates were identified by a combined genetic approach consisting of 16S/23S rRNA intergenic spacer region (ITS) and partial 16S rRNA gene sequencing as Pediococcus acidilactici, Lactobacillus plantarum and Lactobacillus brevis. Hence, the pasteurisation of the vegetable ingredients, excluded wheat flour, enhanced the hygienic conditions of tarhana without influencing the normal evolution of LAB. However, the fermentation at 40 °C favoured pediococci, while the production at 30 °C was mainly characterised by lactobacilli. Yeasts, identified by the restriction fragment length polymorphism (RFLP) of the 5.8S ITS rRNA gene, were mainly represented by the species Saccharomyces cerevisiae in both productions.     

乳酸菌耐盐分子机制研究进展

乳酸菌广泛应用于食品和发酵行业。在酱油、熏肉、泡菜等发酵食品的生产过程中,乳酸菌的生长常受到 高盐浓度的影响。盐胁迫引起的渗透压变化会引起乳酸菌细胞结构损伤,导致细胞生理代谢活动紊乱甚至死亡。因 此,乳酸菌在盐胁迫条件下生存、生长和代谢的能力在食品发酵过程中是非常重要的。本文就乳酸菌的耐盐机制进 行阐释,以期为乳酸菌科学研究及食品发酵工业应用提供参考。     

Probiotic potential of lactic acid bacteria from fermented Malaysian food or milk products

This study investigated the probiotic characteristics of lactic acid bacteria (LAB) isolated from 14 Malaysian fermented food or milk products. In total, 22.3% (121 of 542) of the LAB isolated from the local fermented products exhibited antibacterial activity against Micrococcus luteus. Twelve LAB that demonstrated better antibacterial activity against M. luteus as compared to a commercial strain Lactobacillus casei strain Shirota (LABPC) were selected for further characterisation. Based on 16S rRNA gene sequence, the LAB were identified as pediococci (seven) and lactobacilli (five). All 12 LAB showed bile tolerance, but only eight were acid tolerant at pH ≥ 3.0. The highest level of adhesion to HT‐29 cells was observed among the Lactobacillus sp. LAB 1 and 10. The LAB also showed antimicrobial activity against Escherichia coli and Staphylococcus aureus through the production of organic acids. LAB isolated from Malaysian fermented food and milk products, especially fermented tapioca, contains potential probiotic candidates.     

Characterization of flavour and volatile compounds of fermented squid using electronic nose and HPMS in combination with GC-MS

The present study investigated the flavour characteristics and key volatile components of fermented squid (Dosidicus gigas) as well as their formation mechanism by three different starter cultures of lactic acid bacteria (LAB) and natural squid. The sensory assessment, volatile compounds, as well as the amino acids of the mixed fermented squid were detected using pickled brine as samples of fermented squid. A total 88 types of volatile compounds were found in four samples by 0–72 h of fermentation. After fermentation by LAB, the volatile compounds of squid showed that the fermented squid with different started cultures differed mainly in terms of numbers of alcohols, ketones, and esters. Furthermore, the amounts of volatile compounds among three starter cultures were also obviously different. Gas Chromatography-Mass Spectrometer (GC-MS) analysis indicated that the mixed fermentation process contained relatively higher (+)-limonene (11.71%) (lemon scent) and 3-hydroxy-2-butanone (5.72%) (creamy taste). These compounds were not detected in the control group. The main flavour compounds of nonanal and 2, 4-decadienal were gradually reduced. Meanwhile, 2, 3-butanedione, 2-heptanone, 2-pentylfuran, and nonanoic acid are the key flavour components. The total principal component is 94.01%, which were clarified by electronic nose in combination with principal components analysis. After mixed fermentation by LAB, the total amino acid (TAA) content reached 85.36 g/100 g, which was almost twice the amount of the control, especially in aspartate, glutamate, and threonine. Our results indicated that LAB has obvious effects on deodorization and flavour promotion during the fermentation of squid. This study provided an important basis for the further development and utilization of squid.