بررسي تنوع زيستي ميكروبي سه نوع خمير ترش بومي منطقه اصفهان

چكيده انگليسي :

Biodiversity of Lactic Acid Bacteria in Native Isfahan Wheat Sourdoughs Vahide Saidi V saidi@ag iut ac ir Date of Submission 3 3 2012 Department of Food Science and Technology Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisors Dr S Soleimanian Zad soleiman@cc iut ac irDr M Sheikh Zeinoddin zeinodin@cc iut ac irAbstract Fermentation is a process which is generally taken place by enzymes or microorganisms Cereal fermentations using sourdough as natural leavening agent retained more attention in thelast years largely because of the many advantages sourdough offers over baker s yeast Sourdough fermentation is one of the oldest examples of application of food biotechnology infood production Sourdough is a mixture of flour and water that is fermented with lactic acidbacteria and yeasts and the microbial populations present in the fermented dough are used in theproduction of backery products Based on usual principle used in artisanal or industrialprocesses sourdoughs have been grouped into three types based on fermentation time temperature propagation frequency and baker s yeast addition The microorganisms usuallyoriginate from flour dough ingredients and environment Sourdough is used for the productionof sourdough bread classical bread snacks pizza and sweet backed products Sourdoughfermentations improve dough properties including volume texture flavour and traditionalvalue of the bread retared staling process of bread and protect bread from mould and bacterialspoilage Morever endogenous factors in cereal products carbohydrates nitrogen sources minerals lipids and free faty acids and enzyme activities and process parameters temperature dough yield oxygen fermentation time and number of sourdough propagationsteps markedly influence the microflora of sourdough and the features of leavened backedgoods The aim of this study was to preserve the genetic resources of indigenousmicroorganisms of Iran and also to identify microorganisms that are involved in traditionalbread processing The presence of lactic acid bacteria in 43 samples of traditional sourdoughcollected from diffrenet regions of Esfahan were evaluated The identify of isolated lactic acidbacteria was firstly assayed using morphological characteristics and biochemical tests Thebacterial and yeasts species to identify lactic acid bacteria in the culture medium was used byMRS PDA M17 to detect the presence of lactic acid bacteria were tested for Gram reaction catalase activity spore formation Co2 production from glucose and ability to grow in MRSbroth at 10 and 45 C in stationary tubes on various types of colonies were isolated from samplestaken At microbial groups Lactobacillus plantarum Lactobacillus rossiae Lactobacillusamylovorus Lactobacillus brevis Lactobacillus agilis Lactobacillus alimentarius Lactobacillus casei Lactobacillus fermentum Lactobacillus hilgardi Lactobacillus reuteri Leuconostoc mesenteroides Leuconostoc pentosaceus Leuconostoc dexterinicum andSaccharomyces cerevisiae were identified Further microbial characteristics was performed withmolecular techniques using recA gene Their DNA replication products on agarose gel stainedband in the range 318 bp to Lactobacillus plantarum that is created Results obtained usingrecA gene revealed that 23 of lactobacilli isolates classified as Lactobacillus plantarum Key words Sourdough Lactic acid bacteria Yeast Lactobacillus plantarum

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بررسي تنوع زيستي ميكروبي سه نوع خمير ترش بومي منطقه اصفهان

باكتري هاي اسيد لاكتيك , مخمر , لاكتوباسيلوس پلانتاروم