Browsing by Subject "Wettbewerbsfähigkeit"

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Impact of process parameters on the sourdough microbiota, selection of suitable starter strains, and description of the novel yeast Cryptococcus thermophilus sp. nov.
(2013) Vogelmann, Stephanie Anke; Hertel, Christian
The microbiota of a ripe sourdough consists of lactic acid bacteria (LAB), especially of the genus Lactobacillus, and yeasts. Their composition is influenced by the interplay of species or strains, the kind of substrate as well as the process parameters temperature, dough yield, redox potential, refreshment time, and number of propagation steps (Hammes and Gänzle, 1997). As taste and quality of sourdough breads are mainly influenced by the fermentation microbiota, intense research has been focused on determination of sourdough associated species and search for new starter cultures. In recent years, economic competition pressure and new consumer demands have led to steady research for new cereal products, especially with health benefit or for people suffering from celiac disease. For these reasons, alternative cereals like oat and barley (both toxic for celiac disease patients) as well as the celiac disease compatible cereals rice and maize, sorghum and millets, the pseudocereals amaranth, quinoa and buckwheat as well as cassava got into the focus of interest. However, information about the microbiota of sourdoughs fermented with buckwheat, amaranth, quinoa, oat or barley is not available except for the following recent studies: a study about the microbiota of amaranth sourdoughs by Sterr et al. (2009), a study about barley sourdough by Zannini et al. (2009), a study about oat sourdoughs by Huettner et al. (2010) and a study about buckwheat and teff sourdoughs by Moroni et al. (2011). The microbiota of sourdoughs from the other mentioned cereals as well as cassava was multiply characterised but not systematically. Fermentation conditions were partly not clearly defined, and identification of species was often based on physiological criteria only, known to be insufficient for the exact classification of LAB. Thus, in this thesis, the influence of the process parameters substrate, temperature, refreshment time, amount of backslopping dough as well as the interplay between the different species or strains were examined and potential starter strains were selected. In Chapter III, the effect of the substrate on the sourdough microbiota was examined and suitable starter cultures for fermentation of non-bread cereals and pseudocereals were selected. Eleven different flours from wheat, rye, oat, barley, millet, rice, maize, amaranth, quinoa, buckwheat and cassava were inoculated with a starter mixture containing numerous LAB and yeasts. Sourdoughs were fermented at 30 °C and refreshed every 24 hours until the microbiota was stable. Species were identified by PCR-DGGE as well as bacteriological culture and RAPD-PCR, followed by 16S/26S rRNA sequence analysis. In these fermentations, the dominant yeast was Saccharomyces cerevisiae; Issatchenkia (I.) orientalis was only competitive in the quinoa and the maize sourdough. No yeasts were found in the buckwheat and the oat sourdough. The dominant LAB species were Lactobacillus (L.) paralimentarius in the pseudocereal sourdoughs, L. fermentum, L. helveticus and L. pontis in the cereal sourdoughs, and L. fermentum, L. plantarum and L. spicheri in the cassava sourdough. Competitive LAB and yeasts were inserted as starters for a further fermentation using new flours from rice, maize, millet and the pseudocereals. After ten days of fermentation, most of the starter strains were still dominant, but L. pontis and L. helveticus could not compete with the other species. It is remarkable that from the numerous starter strains which all were adapted to or isolated from sourdoughs, only a few were competitive in these fermentations; but if, then in most cases in a lot of different flours. In Chapter IV, the effects of the exogenous process parameters substrate, refreshment time, temperature, amount of backslopping dough as well as competing species on the two microbial associations L. sanfranciscensis ? Candida (C.) humilis and L. reuteri ? L. johnsonii ? I. orientalis were examined. Both associations had previously been found to be competitive in sourdough (Kline and Sugihara, 1971a; Nout and Creemers-Molenaar, 1987; Gobbetti et al., 1994a; Garofalo et al., 2008; Böcker et al., 1990; Meroth et al., 2003a). 28 sourdough batches were fermented under defined conditions until the microbiota was stable. Dominant LAB and yeasts were characterized by bacteriological culture, RAPD-PCR and 16S/26S rRNA gene sequence analysis. The process parameters for the association L. sanfranciscensis ? C. humilis could be defined as follows: rye bran, rye flour or wheat flour as substrate, temperatures between 20 and 30 °C, refreshment times of 12 to 24 hours and amounts of backslopping dough from 5 to 20 %. In addition, the association was predominating against all competing lactic acid bacteria and yeasts. The association L. reuteri ? L. johnsonii ? I. orientalis was competitive at temperatures of 35 to 40 °C, refreshment times of 12 to 24 hours and the substrates rye bran, wheat flour and rye flour, but only with sufficient oxygen supply. Cell counts of I. orientalis fell rapidly under the detection limit when using high amounts of doughs (small ratio of surface to volume) and refreshment times of 12 hours. The fermentations depicted in Chapter III and IV give new information about the influence of process parameters on the sourdough microbiota. The studies show that the sourdough microbiota is markedly influenced by the process parameters and kind and quality of substrate. The competitiveness of a single LAB or yeast is strain specific. Interactions between microorganisms also play an important role. However, for the search for suitable starter strains, it would be beneficial to know the reasons, why a single LAB or yeast strain is better adapted to specific process parameters or substrates than others. One of the starter sourdoughs used for fermentation I described in Chapter III was a sourdough made from cassava flour, inoculated with several LAB. No yeast had been inserted, but several yeasts were isolated from the ripe sourdough, which are supposed to originate from the cassava flour. An unknown yeast species constituted 10 % of the isolated yeasts which is described as novel species Cryptococcus thermophilus sp. nov. in Chapter V. This yeast is characterized by budding on small neck-like structures, no fermentative ability, growth at 42 °C and without vitamins, a major ubiquinone of Q-10, as well as the production of green or blue fluorescent substances in the growth medium. It is distinct from related species by the ability to assimilate raffinose and cadaverine, the inability to assimilate soluble starch, xylitol, galactitol, butane-2,3-diol, sodium nitrite and lysine, and the inability to produce starch-like substances. The closest relatives are the yeasts belonging to the Cryptococcus humicola complex.
The Competitiveness of the Sugar Industry in Thailand
(2007) Arjchariyaartong, Wuttipong; Zeddies, Jürgen
Thailand is now firmly established as one of the world?s leading sugar exporting countries. During 1995/96 to 2005/06, sugar exports ranged between 2.3 and 5.1 million tons and averaged 3.80 million tons per year. For this reason, sugar cane production is one of the major economic sectors in Thailand. There are several activities involved in the production process such as sugarcane growing, sugar milling, credit banking, exportation, etc. The sugar production activities provide significant full time and temporary employment in sugar factories, sugar transformation, transportation and exports. Therefore, the study of sugar cane and sugar industry?s competitiveness is important, especially with the increasing liberalisation of the world market. Based on the above considerations, this thesis has key objectives as follows: 1. To study the structure of sugarcane and sugar production in Thailand. 2. To analyse costs and returns of sugarcane and sugar production in Thailand. 3. To examine the competitiveness of the sugar industry and identify indicators of competitiveness. 4. To describe strategies of sugarcane growers and sugar factories for improving competitiveness. The methodology applied for the farm sampling is based on the concept of typical farm approach. Farm types are determined by sugarcane experts taking into consideration: location of farm, farm size, sugarcane area and share of rain-fed and irrigated area. The first category of farms was chosen to represent the size that is close to the statistical average. The other types defined represent larger farms to allow the exploration of potentials for economies of size in the region. Management levels on the typical farms are above average. The sugar factories were categorized by region, industry group and crushing capacity. Firstly, the structure of sugar cane production in Thailand can be described as follows. Sugar cane is grown all over the country. The total cane area amounted to 6.34 million rai in 2004/05. The most important regions of sugar cane production are the Northeastern, the Central and the Northern region. The total cane production amounted to 47.82 million tons in 2004/05 with an average yield of 7.54 tons/rai. Secondly, the structure of the sugar industry in Thailand can be described as follows. Within the total number of 46 sugar factories, there are 4 large factories with a crushing capacity of more than 24,000 tons of cane crushed per day, 16 medium size factories (12,000-24,000 tons/day), and 26 small size factories (< 12,000 tons/day). Thirdly, the sugar market in Thailand can be described as follows. The total sugar production amounted to 7 million tons in 2003/04. With a share of domestic consumption of 27.8%, only around 2 million tons of sugar is used for domestic consumption. The rest of around 5 million tons of sugar is exported to the world market, mostly to Asia. The wholesale prices for the domestic market are annually fixed by the government to around 12 Baht/kg in the average. Fourthly, the results of sugarcane farms can be concluded as follows. The analysis of sugarcane costs of production has shown that the total production costs of sugarcane farms for the first ratoon are highest and then decrease in the second and third ratoon. The farms in the Central region have higher average production costs (4,245 Baht/rai) than the cane growers in the Northeast (4,130 Baht/rai) and in the North (3,725 Baht/rai). Low labor costs, especially harvesting costs of around 1,142 Baht per rai, are the predominant reason for the lower cost structure of the farms in the Northeastern region. Fifthly, the results of the sugar factory analysis can be concluded as follows. The five investigated factories are one large factory with a crushing capacity of more than 23,000 tons of cane per day, and four small factories with a cane crushing capacity of less than 12,000 tons/day. Although most of the cane suppliers are small size farmers, the majority of cane comes from medium and large farms. The sugar sales are depending on the type of sugar and the market channel and range from 14 Baht/kg to 18 Baht/kg. The average distance of sugarcane transport is around 53.33 km for sugarcane which is purchased from sugarcane farmers. The closer the sugarcane fields to the factory are the higher is the competitiveness of the sugar factory. The productivity analysis of the sugar industry shows that factory C possesses an advantage with respect to the quantities of total sugar production per rai in production year 2002/03 and 2003/04. The result of ranking the sugar factories according to their competitiveness shows that factory C has an advantage in the total quantity of sugar production per rai. Factory E had the highest advantage in the extraction rate of sugar per ton of sugar cane and gained the highest profit of sugar production. However, factory B has the highest ability to produce sugar with the lowest costs per kg and factory D was the leader in reducing costs of sugar production in Baht per rai. In the summary, the score over all indicators of competitiveness shows that factory E has the highest score. Therefore, factory E has been ranked to be the most competitive factory, followed by factory B, factory D, factory A, and factory C respectively. Finally, this study provides suggestions and policy recommendations for sugarcane farms and sugar factories in four areas. First, sugarcane productivity per rai is still low in Thailand, therefore research and development is necessary in the field of optimization of the production process and breeding of new sugarcane varieties. Second, enough water and access to irrigation system is very important for sugarcane planting, so the government should help to provide these facilities for the farmers. Third, the sugar industry should differentiate their sugar products in order to increase the value added of sugar production. This will help sugar factories in case of encountering the situation of low prices of sugar. Fourth, due to increasing energy costs, sugar factories should get support in acquiring alternative energies and reducing other costs of production by research and development.