Thesis (doctoral)--University of Helsinki, 2005. / Includes bibliographical references. Also available on the World Wide Web.

In an effort to mimic the continuous protein matrix found in gluten-containing breads, the effects of the enzyme microbial transglutaminase were tested in gluten-free (GF) sourdough breads containing five different GF flours: chickpea, brown rice, white rice, oat, and quinoa. The utilization of transglutaminase in GF sourdough bread applications was shown to improve some of the final bread characteristics of GF breads. White and brown rice GF sourdough loaves at 24 hours showed a 28% and 13% decrease in crumb firmness with the addition of 2 U/g dough, respectively. Quinoa-GF sourdough breads at 24 hours showed a 6% increase in specific volume with the addition of 1 U/g dough. Oat and chickpea-GF sourdough loaves did not show improvements in loaf quality with mTG addition. SDS-PAGE analysis revealed that white rice, brown rice, quinoa, and chickpea proteins are adequate substrates for mTG activity, while oat proteins, without the addition of exogenous proteins, lack the characteristics suitable for mTG action.

Microbial contamination and survival during storage of bread are a cause of both health concerns and economic losses. Traditional fermentation systems were studied as sources of lactic acid bacteria (LAB) with antagonistic potential against foodborne pathogens and spoilage organisms, with the aim to improve the safety and shelf life of bakery products. The antagonistic activity of four types of buttermilk (BM) products fermented with Lactococcus lactis subsp. lactis was evaluated against a number of pathogenic bacteria to select the best fermented-BM for application as bio-preservatives in bread crumpets, showing up to 9 µg/ml of nisin equivalent antimicrobial activity. These food ingredients could be suitable to be used in crumpet formulations, BM fermented with Lc. lactis subsp. lactis and nisin influenced the quality and shelf life of crumpets; the pH value and firmness of products with fermented BM was lower and the acidity and springiness was higher than for unfermented BM treatment and control withouth additive. The nisin and fermented BM treatment had beneficial effects on the pore size and colour in comparison with the control, and improved microbial shelf life by 2 days. Commercial and traditional sourdough and bread samples (n=18) were collected to assess the diversity of LAB strains and potential properties when applied to dough and bread. DGGE followed by sequencing showed that Lactobacillus was the predominant genus in the studied sourdoughs. Lb. plantarum and Lb. brevis strains accounted for 69% of the 32 isolates, out of which 10 were amylolytic and 12 had proteolytic activity. Most were also good acid producers after 24 h at 30°C. Some LAB strains presented a strong in vitro inhibitory activity against five indicator strains, showing potential as starter cultures to ferment sourdough. In subsequent experiments, the properties of 24 sourdoughs were evaluated, and one of them, fermented with Lb. plantarum (SIN3) yielded low pH value, high lactic acid production, and suitable microbial growth, and was selected for further bread making performance trials. The bread with fast fermentation and high sourdough concentration (FFHSD) had a lower pH, higher acidity and increased the quality attributes with significantly better shelf life comparing to the other treatments during the storage period. Sensory evaluation demonstrated that fast-fermented breads were more acceptable than the slow-fermented counterparts. Bread prepared with high level (18%) of sourdough fast-fermented with the selected culture (SIN3) had a good eating quality and shelf life. The approach of this study is likely to yield feasible improvements of the current methods of preparation of baking goods.

The process of fermentation in products of bakery is the most important step and it is, in turn, responsible for the aroma of bread, because during this stage the aromatic and volatile compounds which we identify as the characteristic odor of the product are produced.The development of natural yeast is a difficult methodology and requires several steps of maintenance. Considering this aspect as well as the production that the aim of this work was to produce a lyophilized natural yeast, added different concentrations of trehalose, monitoring the physico-chemical and microbiological aspects involved during its manufacture performing analyzes to study cellular viability, the effects involved in the process of freezing and lyophilization and apply this product in bread type sourdough to evaluate the sensory and shelf life aspects. It was produced three types of lyophilized natural yeast, one without addition (FNL 0) of trehalose, one with the addition of 10% (FNL 10) and other with the addition of 15% (FNL 15). The counts (log CFU.g-1) of lactic acid bacteria and of molds and yeasts acid before and after the lyophilization process showed that trehalose has protected the cells of the microorganisms, enabling the lyophilization process, with significant differences (p<0,05) in the treatments with higher concentrations (10 and 15%) of this compound. From the lyophilized natural yeast, breads of sourdough type were elaborated to evaluate the physico-chemical, microbiological and sensory before a treatment with commercial yeast aspects. The results indicated a microbiological inhibition of bacteria and of fungi in treatments made with lyophilized natural yeast in different concentrations of trehalose, showing averages statistically (p<0,05) lower than in commercial breads with yeast. In the sensory evaluation, the breads with lyophilized natural yeast using 15% trehalose (FNL 15) obtained a reasonable concept by trained panel of tasters. / O processo de fermentação em produtos de padaria é a etapa mais importante e é, por sua vez, responsável pelo aroma do pão, pois durante essa etapa são produzidos os compostos aromáticos e voláteis aos quais identificamos como o odor característico do produto. O desenvolvimento de fermento natural é uma metodologia difícil e necessita de várias etapas de manutenção. Tendo em vista esse aspecto bem como o de produção que o objetivo deste trabalho foi produzir um fermento natural liofilizado, adicionado de diferentes concentrações de trealose, monitorando os aspectos físico-químicos e microbiológicos envolvidos durante sua fabricação realizando análises para estudar a viabilidade celular, os efeito envolvidos no proceso de congelamento e liofilização e aplicar esse produto em pão tipo sourdough para avaliar os aspectos sensoriais e de vida de prateleira. Produziu-se três tipos de fermento natural liofilizado, um sem a adição (FNL 0) de trealose, um com a adição de 10% (FNL 10) e outro com a adição de 15% (FNL 15). As contagens (log UFC.g-1) de bactérias ácido láticas e de bolores e leveduras antes e depois do processo de liofilização mostraram que a trealose protegeu as células dos microrganismos, viabilizando o processo de liofilização, com diferenças significativas (p<0,05) nos tratamentos com maior concentração (10 e 15%) desse composto. A partir dos fermentos naturais liofilizados, pães tipo sourdough foram elaborados para avaliar os aspectos físico-químicos, microbiológicos e sensoriais e comparados com pães fabricados com fermento comercial. Os resultados indicaram uma inibição microbiológica de bactérias e de fungos nos tratamentos fabricados com fermento natural liofilizado nas diferentes concentrações de trealose, apresentando médias estatisticamente (p<0,05) menores que nos pães com fermento comercial. Na avaliação sensorial, os pães com fermento natural liofilizado utilizando 15% de trealose (FNL 15) obtiveram um conceito razoável pelo painel treinado de provadores.

Due to the high cost of wheat importation in countries where the climatic conditions do not favour its cultivation, alternative sources of bread baking flour are required. Maize is a suitable alternative because it is by far the most important crop produced in Africa. However, it lacks gluten, the protein that is formed in wheat dough which is responsible for the desirable quality attributes (high loaf volume, soft and open crumb structure) of wheat bread. Therefore the need arises to improve maize bread quality. The effects of three types of non-wheat bread methods on the quality of maize bread were investigated. The first was a traditional sourdough method used in Lesotho for making steamed bread. This involved addition of spontaneously fermenting sorghum malt sourdough (equivalent to 15% of the total maize flour) and pre-gelatinization of the starch in the maize flour with boiling water. The second was a Food and Agriculture Organization method which involved pre-gelatinization of the starch in 10% of the maize flour by cooking. The third method was a modern gluten-free sourdough method which involved fermenting 75% of the maize flour with a multiple strains starter culture or Lactobacillus plantarum plus the natural flora in the maize. The modern sourdough method produced maize bread with a more open crumb structure and a significant increase in loaf volume compared to the other methods. This was probably related to the high percentage of fermented maize flour in the recipe, which was probably sufficient to modify the dough properties satisfactorily enough to impact positively on the maize bread quality. Based on these findings, the modern sourdough method was investigated further. Maize sourdoughs were prepared (as described) and compared to chemically acidified maize dough. Sourdough maize bread had an approx. 25-26% increase in loaf volume and a more open crumb structure with large gas cells. This showed that the maize bread quality improvement was not due to low pH. Confocal laser scanning microscopy revealed a cohesive dough structure in the sourdoughs. Larger cells and a more uniform crumb structure were also observed in maize breads with maize sourdough. This indicated an improvement in the maize dough properties with sourdough. Differential scanning calorimetry showed that maize sourdough had a slightly lower peak temperature than straight maize dough, an indication of starch modification. Rheological analysis showed that maize sourdough had a shorter relaxation time, an indication that it was less elastic. Strain sweep analysis revealed that maize sourdoughs had the lowest elastic modulus, also indicating a less elastic dough. Temperature sweep analysis showed an initial less elastic dough and a final high tan delta, suggesting that the maize dough could withstand gas expansion pressure during baking without crumbling. The dominant lactic acid bacteria in the sourdoughs were identified as L. plantarum. In the two sourdoughs, the L. plantarum present were gram-positive, catalase negative and exhibited proteolytic activities. However, only the L. plantarum in the multiple strains starter culture fermented maize sourdough exhibited amylolytic activities. It is proposed that proteolytic activity of the L. plantarum degraded the endosperm protein matrix and hydrolysed the proteins soluble in the dough liquid, thereby allowing increased accessibility of water to the starch granules. It is further proposed that the amylolytic activity of the L. plantarum slightly hydrolysed the starch granules, increasing water absorption by the starch granules. It is proposed that improvement in maize bread quality by sourdough fermentation is due to starch modification (increase water accessibility and water absorption by the starch granules due to the proteolytic and amylolytic activities of the dominant lactic acid bacteria in the sourdoughs) which made the dough less elastic. This in-turn improves the ability of the dough to trap and withstand the pressure of the expanding carbon dioxide in the fermenting dough and bread. / Thesis (PhD)--University of Pretoria, 2014. / gm2015 / Food Science / Unrestricted

Neste trabalho, foi realizado um estudo sobre a produção de pães de fermentação natural ou “sourdough”, baseado na hipótese que este processo possa apresentar papel bem definido na melhoria do sabor, da estrutura de pão, na estabilização ou aumento dos níveis de vários compostos bioativos, retardamento da biodisponibilidade do amido (baixo índice glicêmico) e no aumento da biodisponibilidade de minerais.. Elaborou-se pães que foram produzidos via fermentação “sourdough” utilizando os microrganismos Kluyveromyces marxianus, Dekkera bruxellensis e Lactobacillus plantarum como cultura de partida. A partir de sete amostras resultantes de um delineamento de mistura Simplex-Centróide, determinou-se o volume especifico dos pães e o pH, acidez e as células viáveis durante a fermentação “sourdough”. Observou-se que pão produzido com Lactobacillus plantarum foi o que apresentou o menor volume específico e a mistura entre K.marxianus e L. plantarum exerceu influência positiva, acarretando o maior volume específico. Durante a fermentação “sourdough” houve redução dos valores de pH e aumento da acidez. Através da análise sensorial verificou-se a boa aceitabilidade para os pães produzidos com a mistura entre D.bruxellensis e K.marxianus e para a mistura entre os três micro-organismos. Estes resultados indicam que o tipo de cultura de partida influência nos parâmetros de qualidade dos pães avaliados. No entanto, novos estudos, envolvendo outras variáveis do processo de fermentação “sourdough” devem ser feitos para melhor avaliação. / In this work it was studied the formulation and production of natural-fermentation breads, also known as “sourdough”, based upon the fact that this process may play a well-defined role in the improvement of flavor, the structure of bread, in the stabilization or increase of the levels of several bioactive compounds, the bioavailability of slow starch (low glycemic index products), and in improving the bioavailability of minerals in this highly consumed product. Breads were produced by fermentation "sourdough" using Kluyveromyces marxianus, Dekkera bruxellensis, and Lactobacillus plantarum as starting cultures. The seven samples derived from a design mix-Simplex Centroid determined the specific volume of breads and pH, acidity, and viable cells during fermentation "sourdough." It was observed that bread produced with Lactobacillus plantarum presented the lowest specific volume, while the mix of K.marxianus and L.plantarum exerted positive influence, leading to the high specific volume. During fermentation "sourdough" there was a reduction in the pH and an increase in acidity. For the sensorial analysis, there was high acceptability for the bread produced with the mixture of D. bruxellensis and K. marxianus and the mix between the three microorganisms. These results indicate that the type of starting culture have strong influence on the quality of bread parameters evaluated. However, further studies involving other process variables fermentation "sourdough" must be carried out in order to better understand this technical product.

Neste trabalho, foi realizado um estudo sobre a produção de pães de fermentação natural ou “sourdough”, baseado na hipótese que este processo possa apresentar papel bem definido na melhoria do sabor, da estrutura de pão, na estabilização ou aumento dos níveis de vários compostos bioativos, retardamento da biodisponibilidade do amido (baixo índice glicêmico) e no aumento da biodisponibilidade de minerais.. Elaborou-se pães que foram produzidos via fermentação “sourdough” utilizando os microrganismos Kluyveromyces marxianus, Dekkera bruxellensis e Lactobacillus plantarum como cultura de partida. A partir de sete amostras resultantes de um delineamento de mistura Simplex-Centróide, determinou-se o volume especifico dos pães e o pH, acidez e as células viáveis durante a fermentação “sourdough”. Observou-se que pão produzido com Lactobacillus plantarum foi o que apresentou o menor volume específico e a mistura entre K.marxianus e L. plantarum exerceu influência positiva, acarretando o maior volume específico. Durante a fermentação “sourdough” houve redução dos valores de pH e aumento da acidez. Através da análise sensorial verificou-se a boa aceitabilidade para os pães produzidos com a mistura entre D.bruxellensis e K.marxianus e para a mistura entre os três micro-organismos. Estes resultados indicam que o tipo de cultura de partida influência nos parâmetros de qualidade dos pães avaliados. No entanto, novos estudos, envolvendo outras variáveis do processo de fermentação “sourdough” devem ser feitos para melhor avaliação. / In this work it was studied the formulation and production of natural-fermentation breads, also known as “sourdough”, based upon the fact that this process may play a well-defined role in the improvement of flavor, the structure of bread, in the stabilization or increase of the levels of several bioactive compounds, the bioavailability of slow starch (low glycemic index products), and in improving the bioavailability of minerals in this highly consumed product. Breads were produced by fermentation "sourdough" using Kluyveromyces marxianus, Dekkera bruxellensis, and Lactobacillus plantarum as starting cultures. The seven samples derived from a design mix-Simplex Centroid determined the specific volume of breads and pH, acidity, and viable cells during fermentation "sourdough." It was observed that bread produced with Lactobacillus plantarum presented the lowest specific volume, while the mix of K.marxianus and L.plantarum exerted positive influence, leading to the high specific volume. During fermentation "sourdough" there was a reduction in the pH and an increase in acidity. For the sensorial analysis, there was high acceptability for the bread produced with the mixture of D. bruxellensis and K. marxianus and the mix between the three microorganisms. These results indicate that the type of starting culture have strong influence on the quality of bread parameters evaluated. However, further studies involving other process variables fermentation "sourdough" must be carried out in order to better understand this technical product.

Neste trabalho, foi realizado um estudo sobre a produção de pães de fermentação natural ou “sourdough”, baseado na hipótese que este processo possa apresentar papel bem definido na melhoria do sabor, da estrutura de pão, na estabilização ou aumento dos níveis de vários compostos bioativos, retardamento da biodisponibilidade do amido (baixo índice glicêmico) e no aumento da biodisponibilidade de minerais.. Elaborou-se pães que foram produzidos via fermentação “sourdough” utilizando os microrganismos Kluyveromyces marxianus, Dekkera bruxellensis e Lactobacillus plantarum como cultura de partida. A partir de sete amostras resultantes de um delineamento de mistura Simplex-Centróide, determinou-se o volume especifico dos pães e o pH, acidez e as células viáveis durante a fermentação “sourdough”. Observou-se que pão produzido com Lactobacillus plantarum foi o que apresentou o menor volume específico e a mistura entre K.marxianus e L. plantarum exerceu influência positiva, acarretando o maior volume específico. Durante a fermentação “sourdough” houve redução dos valores de pH e aumento da acidez. Através da análise sensorial verificou-se a boa aceitabilidade para os pães produzidos com a mistura entre D.bruxellensis e K.marxianus e para a mistura entre os três micro-organismos. Estes resultados indicam que o tipo de cultura de partida influência nos parâmetros de qualidade dos pães avaliados. No entanto, novos estudos, envolvendo outras variáveis do processo de fermentação “sourdough” devem ser feitos para melhor avaliação. / In this work it was studied the formulation and production of natural-fermentation breads, also known as “sourdough”, based upon the fact that this process may play a well-defined role in the improvement of flavor, the structure of bread, in the stabilization or increase of the levels of several bioactive compounds, the bioavailability of slow starch (low glycemic index products), and in improving the bioavailability of minerals in this highly consumed product. Breads were produced by fermentation "sourdough" using Kluyveromyces marxianus, Dekkera bruxellensis, and Lactobacillus plantarum as starting cultures. The seven samples derived from a design mix-Simplex Centroid determined the specific volume of breads and pH, acidity, and viable cells during fermentation "sourdough." It was observed that bread produced with Lactobacillus plantarum presented the lowest specific volume, while the mix of K.marxianus and L.plantarum exerted positive influence, leading to the high specific volume. During fermentation "sourdough" there was a reduction in the pH and an increase in acidity. For the sensorial analysis, there was high acceptability for the bread produced with the mixture of D. bruxellensis and K. marxianus and the mix between the three microorganisms. These results indicate that the type of starting culture have strong influence on the quality of bread parameters evaluated. However, further studies involving other process variables fermentation "sourdough" must be carried out in order to better understand this technical product.

Résumé confidentiel / Résumé confidentiel

Inledning: Surdeg är idag en trend som fångats av många och de flesta bagerier ochdagligvarubutiker säljer bröd som kallas för surdegsbröd. Ett traditionellt surdegsbröd är ettbröd där surdegen används som enda hävningsmedel i brödet. Syfte: Syftet var att undersöka skillnader i sensoriska egenskaper, utifrån ettkonsumentperspektiv, samt GI-värde mellan surdegsbröd, jästbröd och bröd bakat på bådesurdeg och jäst. Material och metod: Metoderna som användes var två olika konsumenttester för att bestämmaskillnader mellan de tre bröden, och en in vitro-metod för att bestämma GI-värde. Resultat: Resultatet visade att konsumenter känner skillnad mellan surdegsbröd och jästbrödoch mellan surdegsbröd och bröd bakat på både surdeg och jäst men däremot inte mellanjästbröd och bröd bakat på både surdeg och jäst. Den syrliga smaken i surdegsbröd minskar ombrödet bakas på både surdeg och jäst. GI-mätningen genom in vitro-metoden visade att brödetbakat på både surdeg och jäst hade lägst GI medan surdegsbrödet hade högst. Slutsats: Ett bröd bakat på både surdeg och jäst är mer likt ett jästbröd än ett surdegsbröd. In vitro-metoden är inte den mest tillförlitliga för att undersöka skillnader i GI för justsurdegsbröd samtidigt som surdegsbrödets pH-värde kan ha varit för högt för att kunna sänkabrödets GI-värde. Inga slutsatser kunde därför dras från GI-mätningen. / Introduction: Sourdough is today a trend that has been caught by many and most bakeries andgrocery stores sell bread called “Sourdough bread”. Traditional sourdough bread is bread wherethe sourdough is used as only leavening agent. Purpose: The purpose was to examine differences in sensory attributes, from a consumerperspective, and glycemic index between sourdough bread, yeast bread and bread baked withboth sourdough and yeast. Material and Method: The methods used were two different consumer tests to determinedifferences between the three breads, and an in vitro-method for determining the glycemicindex. Result: The results showed that consumers can sense the difference between sourdough breadand yeast bread and between sourdough bread and bread baked with both sourdough and yeastbut not between yeast bread and bread baked with both sourdough and yeast. The sourish tasteof sourdough bread decreases if the bread is baked with both sourdough and yeast. Theglycemic index measurements by the in vitro-method showed that the bread baked with bothsourdough and yeast had the lowest glycemic index value whilst the sourdough bread had thehighest. Conclusion: Bread baked with both sourdough and yeast more resembles yeast bread thansourdough bread. The in vitro-method is not the most reliable for examining differences inglycemic index value for sourdough bread meanwhile the pH-value of the sourdough breadmay have been too high to be able to lower the glycemic value of the bread. No conclusionscould therefore be made from the glycemic index measurements.