Differences in microbiological, physic-chemical and sensory properties of conventional versus sourdough bread (Master thesis)

Κάτση, Παυλίνα

The objective of this study was to differentiate bread was prepared using baker’s yeast and sourdough on a qualitative and quantitative basis. For this purpose bread was prepred using baker’s yeast and soydough respectively. Microbiological analysis (TVC, lactic acid bacteria, Enterobacteriaceae, yeast – moulds and B. cereus) was performed on the two different types of bread. In addition, pH was measured as well as total titratable acidity (TTA). Additionally, their aromatic profile was studied with the SPME-GC/MS technique. Texture profile analysis (TPA) was carried out using an Instron dynamometer. Finally, organoleptic evaluation was carried out concerning the appearance, texture, taste and aroma of bread. Sampling was carried out at two-day intervals from day 0 to day 8 for the yeast bread samples and from day 0 to day 18 for the sourdough bread samples. The experiment was terminated when samples were no longer organoleptically acceptable to the consumer. The results showed that the shelf life of bread increased from 5 to ten days when sourdough was used. The microbiological growth was suppressed due to the acidic environment of sourdough bread and thus microbiological shelf life increased. For total mesophilic bacteria, reached 7 log cfu/g on the 7th – 8th day of storage for yeast bread, while for sourdough bread, it did not exceed the value 4 log cfu/g until the end of storage (day 18). pH and acidity measurements indicated that sourdough bread is more acidic. pH and acidity values (in mlNaOH 0.1N) for sourdough bread were between 6.71 - 6.36 and 7.9 - 8.7 respectively, while for yeast bread between 5.7 - 5.5 and 4 - 6.75 respectively. SPME-GC/MS analysis of flavor compounds showed that the main compounds detected in both breads are: ethanol, hexanol, hexanal, 1-octene-3-ol, heptanal, hexane, nonalanine, 3-methylbutanal, 3-methylbutanol, 2-methylbutanol, 2-methylpropanol and benzaldehyde. Acetic acid and furfural were detected only in the sourdough bread. Texture analysis showed that sourdough bread is harder, less elastic and more consistent than yeast bread. Organoleptically, sourdough bread has a richer aroma and sour taste according to the panelists’ comments. Chromatographic analysis mainly showed the presence of acetic acid, which is absent from yeast bread as it derives from lactic acid fermentation.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
Subject classification: Ψωμί
Keywords: Ψωμί,Προζύμι,Χρόνος ζωής,Ποιότητα,Bread,Sourdough,Shelf-live,Quality
URI: http://olympias.lib.uoi.gr/jspui/handle/123456789/29133
Appears in Collections:Διατριβές Μεταπτυχιακής Έρευνας (Masters)

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