Accelerated shelf life tests of wheat tortillas A study of microbial and textural deterioration in wheat tortilla

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dc.contributor.authorNilsson, Fredrik
dc.contributor.departmentChalmers tekniska högskola / Institutionen för biologi och biotekniksv
dc.contributor.departmentChalmers University of Technology / Department of Biology and Biological Engineeringen
dc.date.accessioned2019-07-03T14:55:45Z
dc.date.available2019-07-03T14:55:45Z
dc.date.issued2018
dc.description.abstractThis study tried to shorten the time required for shelf life studies in product development of wheat tortillas, by developing accelerated shelf life test (ASLT) models for microbial and textural shelf life. ASLTs speed up product degradation by exposure to extreme environmental conditions and in this case were temperature and relative humidity (RH) used. The samples were divided into four storage groups: 3°C and 70% RH, 20°C and 30% RH, 27°C and 80% RH as well as 40°C and 80% RH. Texture was determined with a fold/roll-method, an instrument and by a sensory panel. Microbial concentrations were determined by a laboratory company. Gas composition inside the bags, tortilla pH, water content and water activity were measured to determine possible links to the shelf life. It was not possible to calculate an ASLT model for the microbial growth because of unknown starting number of microbes. The microbial tests however showed that a high temperature and humidity caused the number of bacteria to rapidly increase above what is considered acceptable. Microbial ASLTs thus seem possible, but more tests with a lower detection limit are needed to create a model. To avoid bad taste from nonpathogenic bacterial growth, consumers are recommended to avoid storing the tortillas in high temperature and/or humidity. Textural ASLTs also seem possible in regards of rollability and foldability, but more tests are needed to precisely determine the accelerating factor. Stickiness and translucency seems to deteriorate much slower than rollability and foldability under normal storage conditions. It is therefore suggested to be enough to check that freshly baked tortillas meet the quality requirements of stickiness and translucency. Tortillas seemed to lose textural quality at the same rate, or slower, in refrigerator compared to room conditions. Longer shelf life studies are therefore suggested, to verify if this is the case. If so, storage in a refrigerator could possibly prolong shelf life of wheat tortillas. Changes in the modified atmosphere inside the bags seems to correlate with textural degradation. A study with atmospheric air instead would therefore be interesting as an attempt to determine if it retards textural degradation in wheat tortillas.
dc.identifier.urihttps://hdl.handle.net/20.500.12380/256239
dc.language.isoeng
dc.setspec.uppsokLifeEarthScience
dc.subjectMiljövetenskap
dc.subjectLivsmedelsteknik
dc.subjectEnvironmental Sciences
dc.subjectFood Engineering
dc.titleAccelerated shelf life tests of wheat tortillas A study of microbial and textural deterioration in wheat tortilla
dc.type.degreeExamensarbete för masterexamensv
dc.type.degreeMaster Thesisen
dc.type.uppsokH
local.programmeBiotechnology (MPBIO), MSc
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