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Production of Yogurt Under High Pressure: Effect on Fermentative Process and Yogurt Characteristics = = Producao de iogurte sob alta pressao: efeito no processo fermentativo e nas caracteristicas do iogurte.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Production of Yogurt Under High Pressure: Effect on Fermentative Process and Yogurt Characteristics =/
Reminder of title:	Producao de iogurte sob alta pressao: efeito no processo fermentativo e nas caracteristicas do iogurte.
Author:	Lopes, Rita Pinheiro.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
Description:	173 p.
Notes:	Source: Dissertations Abstracts International, Volume: 81-11, Section: B.
Contained By:	Dissertations Abstracts International81-11B.
Subject:	Food science. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=27933764
ISBN:	9781658480406

Production of Yogurt Under High Pressure: Effect on Fermentative Process and Yogurt Characteristics = = Producao de iogurte sob alta pressao: efeito no processo fermentativo e nas caracteristicas do iogurte.
Lopes, Rita Pinheiro.

Production of Yogurt Under High Pressure: Effect on Fermentative Process and Yogurt Characteristics =Producao de iogurte sob alta pressao: efeito no processo fermentativo e nas caracteristicas do iogurte. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 173 p.

Source: Dissertations Abstracts International, Volume: 81-11, Section: B.

Thesis (Ph.D.)--Universidade de Aveiro (Portugal), 2018.

This item must not be sold to any third party vendors.

Fermentation under non-conventional conditions has gained prominence in the last years, due to the possible process improvements. Food fermentation under sub-lethal pressures is one of such cases, and may bring novel characteristics and features not only to fermentative processes, but also to the final food products. In this work, yogurt production was used as a case-study of this approach and the effect of variation of both pressure (10-100 MPa) and temperature (25-50 ºC) during fermentation was studied. Initially, a preliminary study was performed aiming the development of strategies to reduce the experimental time and resources during the work. Then, a kinetic study was conducted, evaluating lactic acid production and lactose consumption over fermentation time. Fermentative rates were highly dependent on the fermentation conditions used, with the increase of pressure slowing down yogurt fermentation and higher rates achieved at 43 ºC. But, interesting features were obtained at 10 MPa, where pH variation profiles were similar to those of atmospheric pressure (0.1 MPa) at almost all temperatures tested. In particular, fermentation at 10 MPa/43 ºC presented the optimal conditions, where yield and efficiency of lactic acid production during fermentation were improved relatively to fermentation at 0.1 MPa - 1.40 gP gS -1 of yield and 75 % of efficiency at 10 MPa against 0.79 gP gS -1 and 40 % at 0.1 MPa, respectively. In addition, the final yogurts produced were analyzed regarding their microbiological and physical properties, and differences were observed between yogurts. In the case of starter cultures, it was found that their growth is affected by the fermentation conditions used during yogurt production: fermentations at 35 and 43 ºC lead to final microbial counts higher than 8.00 log10 (CFU g-1), while counts between 3.00 and 6.50 log10 (CFU g-1) were obtained after the fermentations at 50 ºC. Comparing both starter cultures, Streptococcus thermophilus was more sensitive to the combination of high temperature and high pressure than Lactobacillus bulgaricus. Regarding physical properties of the gel network, both syneresis and texture were influenced by the variations of the fermentation conditions. In this case, the yogurts fermented at 10 MPa presented characteristics more similar to the yogurts produced at 0.1 MPa (syneresis levels similar to control samples and a firm texture without being excessive). A comparative metabolomic study was performed to analyze the metabolites present on the yogurts produced. Several differences were observed in the metabolite accumulation, including aromatic compounds, organic acids and alcohols, all products of yogurt fermentation. The main difference was verified on the compounds responsible for butter-like flavor in yogurt, with diacetyl being present in higher amounts on 0.1 MPa yogurts, while higher amounts of acetoin were obtained on 10 MPa yogurts. These differences can be reflected in the sensorial perception of yogurts, where 10 MPa yogurts can present a softer flavor than yogurts produced at 0.1 MPa. Overall, variation of pressure and temperature during food fermentations can be used not only to regulate the fermentation kinetics, but also to produce a final product with different characteristics. As a consequence, the processes can be modulated to improve food quality and expand the consumer choices of the fermented product. Therefore, this work opens the possibility of applying these type of strategies on a wide range of food fermentative processes, with potential to create and develop new food products.

ISBN: 9781658480406Subjects--Topical Terms:

3173303
Food science.
Subjects--Index Terms:

Yogurt production

Production of Yogurt Under High Pressure: Effect on Fermentative Process and Yogurt Characteristics = = Producao de iogurte sob alta pressao: efeito no processo fermentativo e nas caracteristicas do iogurte.
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245 1 0 $a Production of Yogurt Under High Pressure: Effect on Fermentative Process and Yogurt Characteristics = $b Producao de iogurte sob alta pressao: efeito no processo fermentativo e nas caracteristicas do iogurte.
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300 $a 173 p.
500 $a Source: Dissertations Abstracts International, Volume: 81-11, Section: B.
502 $a Thesis (Ph.D.)--Universidade de Aveiro (Portugal), 2018.
506 $a This item must not be sold to any third party vendors.
520 $a Fermentation under non-conventional conditions has gained prominence in the last years, due to the possible process improvements. Food fermentation under sub-lethal pressures is one of such cases, and may bring novel characteristics and features not only to fermentative processes, but also to the final food products. In this work, yogurt production was used as a case-study of this approach and the effect of variation of both pressure (10-100 MPa) and temperature (25-50 ºC) during fermentation was studied. Initially, a preliminary study was performed aiming the development of strategies to reduce the experimental time and resources during the work. Then, a kinetic study was conducted, evaluating lactic acid production and lactose consumption over fermentation time. Fermentative rates were highly dependent on the fermentation conditions used, with the increase of pressure slowing down yogurt fermentation and higher rates achieved at 43 ºC. But, interesting features were obtained at 10 MPa, where pH variation profiles were similar to those of atmospheric pressure (0.1 MPa) at almost all temperatures tested. In particular, fermentation at 10 MPa/43 ºC presented the optimal conditions, where yield and efficiency of lactic acid production during fermentation were improved relatively to fermentation at 0.1 MPa - 1.40 gP gS -1 of yield and 75 % of efficiency at 10 MPa against 0.79 gP gS -1 and 40 % at 0.1 MPa, respectively. In addition, the final yogurts produced were analyzed regarding their microbiological and physical properties, and differences were observed between yogurts. In the case of starter cultures, it was found that their growth is affected by the fermentation conditions used during yogurt production: fermentations at 35 and 43 ºC lead to final microbial counts higher than 8.00 log10 (CFU g-1), while counts between 3.00 and 6.50 log10 (CFU g-1) were obtained after the fermentations at 50 ºC. Comparing both starter cultures, Streptococcus thermophilus was more sensitive to the combination of high temperature and high pressure than Lactobacillus bulgaricus. Regarding physical properties of the gel network, both syneresis and texture were influenced by the variations of the fermentation conditions. In this case, the yogurts fermented at 10 MPa presented characteristics more similar to the yogurts produced at 0.1 MPa (syneresis levels similar to control samples and a firm texture without being excessive). A comparative metabolomic study was performed to analyze the metabolites present on the yogurts produced. Several differences were observed in the metabolite accumulation, including aromatic compounds, organic acids and alcohols, all products of yogurt fermentation. The main difference was verified on the compounds responsible for butter-like flavor in yogurt, with diacetyl being present in higher amounts on 0.1 MPa yogurts, while higher amounts of acetoin were obtained on 10 MPa yogurts. These differences can be reflected in the sensorial perception of yogurts, where 10 MPa yogurts can present a softer flavor than yogurts produced at 0.1 MPa. Overall, variation of pressure and temperature during food fermentations can be used not only to regulate the fermentation kinetics, but also to produce a final product with different characteristics. As a consequence, the processes can be modulated to improve food quality and expand the consumer choices of the fermented product. Therefore, this work opens the possibility of applying these type of strategies on a wide range of food fermentative processes, with potential to create and develop new food products.
520 $a Recentemente, as fermentacoes sob condicoes nao convencionais tem vindo a ganhar destaque na literatura, devido as possiveis melhorias que podem trazer para os processos fermentativos. Por exemplo, quando aplicada a fermentacoes alimentares, esta abordagem pode resultar em novas caracteristicas tanto do processo fermentativo, como tambem dos generos alimenticios produzidos. Desta forma, a producao de iogurte foi utilizada, neste trabalho, como um caso de estudo, onde o efeito da variacao da pressao (10- 100 MPa) e da temperatura (25-50 ºC) durante a fermentacao foi estudado. Numa fase inicial, foi realizado um estudo preliminar para desenvolver estrategias para reduzir o tempo e os recursos experimentais no decorrer do trabalho. De seguida, a producao de acido lactico e o consumo de lactose foram analisados ao longo do tempo de fermentacao, de modo a estudar a cinetica do processo de fermentacao. Verificou-se que o consumo de substrato e formacao de produtos sao muito dependentes das condicoes utilizadas na producao de iogurte, com o aumento da pressao a diminuir a velocidade de fermentacao, com a fermentacao a ser mais rapida a 43 ºC. No entanto, as fermentacoes a 10 MPa apresentaram os resultados mais interessantes (do ponto de vista da velocidade do processo), uma vez que os perfis fermentativos foram semelhantes ao do controlo (fermentacao a pressao atmosferica, 0.1 MPa) para todas as temperaturas testadas. Mais especificamente, a fermentacao a 10 MPa/43 ºC correspondeu as condicoes otimas para a producao de iogurte, onde o rendimento e a eficiencia de producao de acido lactico foram melhorados relativamente a fermentacao a 0.1 MPa - rendimento de 1.40 gP gS -1 e eficiencia de 75 % a 10 MPa versus 0.79 gP gS -1 e 40 % a 0.1 MPa, respetivamente. Para alem disso, algumas caracteristicas dos iogurtes finais foram tambem avaliadas e foram detetadas diferencas entre eles. No caso das bacterias acido-lacticas, o seu crescimento durante o processo fermentativo foi afetado pelas condicoes de fermentacao, resultando em cargas microbianas diferentes. Por exemplo, foram observadas cargas microbianas superiores a 8.00 log10 (CFU g-1) no final das fermentacoes a 35 e 43 ºC, enquanto que nas fermentacoes a 50 ºC apenas foram observadas cargas microbianas entre 3.00 e 6.50 log10 (CFU g-1). Comparando as duas bacterias starter, Streptococcus thermophilus foi mais sensivel a combinacao de altas pressoes e temperaturas do que Lactobacillus bulgaricus. Quanto as propriedades fisicas do iogurte, a variacao das condicoes fermentativas teve impacto tanto na sinerese como na textura dos iogurtes. Os iogurtes fermentados a 10 MPa apresentaram as caracteristicas mais semelhantes aos iogurtes controlo, sendo caracterizados por niveis semelhantes de sinerese e uma textura firme sem ser excessiva. De modo a comparar os metabolitos presentes nos diferentes iogurtes produzidos, foi tambem realizado um estudo metabolomico. Neste estudo, foram detetadas varias diferencas na acumulacao de metabolitos correspondentes a produtos da fermentacao responsavel pela producao de iogurte, tais como compostos aromaticos, acidos organicos, alcoois, entre outros. No entanto, a principal diferenca foi verificada nos compostos responsaveis pelo aroma amanteigado do iogurte, visto que quantidades superiores de diacetilo foram detetadas nos iogurtes produzidos a 0.1 MPa, enquanto que maiores quantidades de acetoina foram detetadas nos iogurtes produzidos sob pressao. Estas diferencas podem refletir-se na percecao sensorial dos iogurtes, podendo traduzir-se num sabor mais suave nos iogurtes produzidos a 10 MPa. Em suma, a variacao da pressao e temperatura durante a fermentacao de diferentes alimentos pode ser utilizada nao so para regular a velocidade fermentativa do processo, mas tambem para produzir um genero alimenticio com caracteristicas diferentes. Desta forma, os processos fermentativos podem ser adaptados de modo a melhorar a qualidade alimentar e expandir as escolhas dos consumidores. Este trabalho abre entao a possibilidade de aplicar este tipo de abordagens a uma grande variedade de processos fermentativos alimentares, podendo assim ajudar na producao e desenvolvimento de novos produtos alimentares.
590 $a School code: 5890.
650 4 $a Food science. $3 3173303
650 4 $a Agricultural engineering. $3 3168406
650 4 $a Chemical engineering. $3 560457
653 $a Yogurt production
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710 2 $a Universidade de Aveiro (Portugal). $3 1256647
773 0 $t Dissertations Abstracts International $g 81-11B.
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791 $a Ph.D.
792 $a 2018
793 $a English
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