Baker's Yeast Quality Evaluation for Repacking and Storage under ...

GenusShapeSporeformingMotilitytestO/F testCatalasetestoxidizestestGrowth inairGramstrainJournal of Applied and Industrial Sciences, 2013, 1 (2): 6-15, ISSN: 2328-4595 (PRINT), ISSN: 2328-4609 (ONLINE)Questionnaire: Results of the questionnaire made aboutBaker’s Yeast selling in Khartoum North were illustrated inTable (11) for one hundred shopkeepers.Data AnalysisResults were analyzed statistically and the analysis ofvariance was performed (at P ≤0.05 level) to determine thedeterioration in CFU/gr, yeast activity, specific volume andsensory evaluation of yeast samples with time consumed inroom temperature and refrigerator, organoleplic test andquestionnaire raw data. Examination the significant differencesusing Least Significant Difference (LSD) test to separate themeans [29].III. RESULTS AND DISCUSSIONThe yeast strains studied were coded and noted in Table (1).The rheological characteristics of wheat flour used arepresented in Table (2).Table 2.Rheological Analysis of the Wheat FlourParameterResultWater absorption (%) 64.2Dough, Stability (min) 7.2Dough, Development time (min) 5.7Water absorption of wheat flour was found 64.2% whichlies within the range of 58.6% to 65.1% of Canadian flours,and similar develop time (5.7 minutes) reported [30]. Recentknowledge about the roles of water in the manufacture of freshand frozen yeasted dough was reviewed [10].The stability ofdough was found 7.2 minutes which found less than 17.2minutes [31]. In terms of dough strength determined byFarinograph, the flour used was generally designated as strongwheat flour. The characteristics of the flour used were ofstandard baking quality. The results of gluten index, wet glutenand dry gluten that shown in Table (3), were 71.35%, 38.3%and 12.9% respectively. The gluten index was found lowerthan 80%, which represents the standard good quality breadflour [32].Table 3.Gluten Quantity and qualityParameterResultWet gluten% 38.3Dry gluten% 12.9Gluten index% 71.35The viable counts as CFU/gr of the yeast factory sealedpackages were presented in Table (4).Table 4.The Viable Counts of Yeasts A, B and C as CFU/Gand the Total Bacterial Contamination of Factory SealedPackage.SampleViablecount(CFU/g)Graycolonies(count/g)Bacterial countsYellowcolonies(count/g)8Total(count/g)A 1.3 x 10 10 2.2 x 10 2 1.5 x 10 2 3.7 x 10 2B 1.1 x 10 10 3.2 x 10 3 - 3.2 X 10 3C 1.5 X 10 10 1.0 X 10 4 - 1.0 x 10 4Where: A: Saf-instant. B: Fermipan . C: MauripanThe CFU/gr for samples A, B and C, were found to be1.3X10 10 /gr, 1.1X10 10 and 1.5X10 10 gr, respectively. Onegram of baker’s yeast should contain about 3X10 10 CFU/gr[33] and [34]. This means that, the viability of samples understudy was lower than the theoretical value for about onedecimal. One gram of baker’s yeast should contain not lessthan 10 billion 1X10 10 CFU/gr. [35]. Accordingly, the yeastsamples under study before storage can be considered as goodquality yeasts. In fact, a colony may be formed from more thanone yeast cell. It is therefore important to be careful if onewants to judge the viability of yeast from their CFU/gr, onehas to know their activity as well. The three commercialbrands of yeast were tested for contamination with bacteria.The bacteria associated with samples were isolated accordingto their color and shape of the colonies as shown in Table (5).Actually, two different colonies were found associating withsamples. One colony group was yellowish in color while theother colony group was grayish. The yellowish coloniescontaminating baker’s yeast samples were tentativelyidentified as Bacillus spp. The gray colonies were tentativelyidentified as Staphylococcus spp. as presented in Table (5).Table 5. Isolates of Bacterial Genera Contaminating the Factory Sealed PackagesColonyYellowColonies+ve +ve -ve +ve F +ve +ve Rod BacillusGrayColonies +ve +ve -ve +ve F -ve -ve Cocci Staphylococcus