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

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Journal of Applied and Industrial Sciences, 2013, 1 (2): 6-15, ISSN: 2328-4595 (PRINT), ISSN: 2328-4609 (ONLINE)Where: O/F means Oxidation – FermentationBacillus spp. was found dominant and contaminating allsamples at different levels. Counts of Bacillus spp. were2.2X10 2 , 3.2X10 3 and 1X10 4 CFU/gr for sample A, B and C,respectively. Staphylococcus spp. were found contaminatingamount [36]. Active dry and compressed Baker’s yeast sold inEgypt were tested for contamination; faecal coliforms,Salmonella, Bacillus cereus and Staphylococcus aureusdetected indicated that, Backer’s yeast could represent notablesample B merely at a level of 1.5X10 2 CFU/gr. Coliform hazards to humans and may be cause for public healthbacterium and Salmonella genera were not found concerns [37].contaminating yeast samples. The total bacterial contamination Fermentation time means the time needed to produce onecounts were 3.7X10 2 , 3.2X10 3 and 1.0X10 4 for samples A, B thousand Cm 3 of carbon dioxide by the yeast sample inand C, respectively. Bacterial contamination of the yeastsamples in their factory sealed packages were foundacceptable according to the Sudanese standards. As stated bySaudi Standards and Meteorology Organization; SSMO [36],the total bacterial contamination should not exceed 1X10 4colonies per one gram of baker’s yeast and the Coliforms andSalmonella spp. must not be found. Accordingly, the testedminutes. The fermentation time indicates the yeast activity i.e.the faster yeast strain reached the required volume of carbondioxide, the more active it is. The three yeast samples weretested for their activity as described before and results arepresented in Table (6). Yeast sample C was the fastest, sampleA was moderate and sample B was delayed 45 minutes toproduce the required amount of gas.yeast brands were originally contaminated but in an acceptableTable 6: Fermentation Time and Specific Volume of Loaves Produced By Factory Sealed Package.Sample Fermentation time for production 1000Cm 3 CO 2 (minutes)Loaves specific volume(cc/g)43 4.80AB 45 4.70C 35 4.88Where: A: Saf-Instant. B: Fermipan. C: Mauripan.9Fermentation time has converse relation with the viability.Sample C which had the highest CFU/gr was the best inviability and activity. This can be explained by the fact that themore number of viable cells count, the more capability of yeastfermentation. The fermentation time before storage will beconsidered as a reference time for further investigations whenchanges of the fermentation time for the samples in storage[38].The specific volume of the loaves raised containing yeastsamples at zero time of the storage were 4.80, 4.70 and 48 cc/gfor sample A, B and C, respectively. These results are shownin Table (6). The values agreed with the result reported by[39] who reported 4.75 cc/gr and better than the result of3.67cc/gr reported by [11] and Food Research Centre Criteria[40]. The mentioned values were in the range between 3.5 and4.0 cc/g expected for good quality yeast. However, all yeastsamples under study were found of good quality before thebeginning of storage period. The results before storage will betaken as a reference for samples in storage. The intensity of thechanges during storage depends on temperature [9]. Six yeastsamples were used to study the deterioration of yeast viabilityin storage. Three of these samples were stored at roomtemperature. The other three samples were stored inrefrigerator temperature. The results are presented in Table(7).At zero time of the storage, sample A recorded 1.3X10 10CFU/gr. After one week of storage, at room temperature, thevalue has dropped to 8.1X10 9 CFU/gr, while after four weeksit has dropped to 9.1X19 8 CFU/gr. This value is within thecritical value of acceptability. After five weeks, the yeastsample in storage became of poor quality.In comparison with the same yeast strain stored in therefrigerator temperature, significant differences (at P ≤0.05level) were observed between samples A stored at roomtemperature and A-1 stored in the refrigerator. The CFU/gr ofsample A stored at room temperature has decreased morequickly than that of sample A-1 stored in the refrigerator. Nosignificant differences (at P≥0.05 level) between the CFU/grvalues of sample B and C in storage at room temperature wereobserved. Both samples became of poor quality, in theirviability basis, after about seven weeks. No significantdifferences (at P≥0.05 level) between the CFU/gr values of thethree samples stored in the refrigerator were noticed. Allsamples A-1, B-1 and C-1 became of poor quality after abouttwelve weeks. That means the repacked yeast can be stored atroom temperature for maximum of four weeks. This period canbe extended to ten weeks in the refrigerator without ignoringthe importance of the conventional handling.
Journal of Applied and Industrial Sciences, 2013, 1 (2): 6-15, ISSN: 2328-4595 (PRINT), ISSN: 2328-4609 (ONLINE)Table (7).The Viable Count of Yeast Samples A, A-1, B, B-1, C and C-1 Stored for 14 Weeks.10Storageduration(week)Samples CFU/gA A-1 B B-1 C C-11 8.1 x 10 9 9.1 x 10 9 8.0 x 10 9 8.4 x 10 9 8.6 x 10 9 1.2 x 10 92 7.2 x 10 9 8.6 x 10 9 7.1 x 10 9 8.2 x 10 9 8.2 x 10 9 1.0 x 10 93 6.0 x 10 9 8.1 x 10 9 5.3 x 10 9 7.6 x 10 9 7.7 x 10 9 9.8 x 10 94 9.1 x 10 8 7.2 x 10 9 3.2 x 10 9 6.7 x 10 9 6.3 x 10 9 8.9 x 10 95 6.2 x 10 8 6.0 x 10 9 1.5 x 10 9 5.4 x 10 9 4.8 x 10 9 8.1 x 10 96 5.0 x 10 8 4.9 x 10 9 8.8 x 10 8 8.6 x 10 9 1.2 x 10 9 7.8 x 10 97 1.7 x 10 8 3.4 x 10 9 6.1 x 10 8 3.1 x 10 9 8.1 x 10 8 7.2 x 10 98 7.4 x 10 7 1.3 x 10 9 4.1 x 10 8 2.2 x 10 9 4.3 x 10 8 6.3 x 10 99 2.1 x 10 7 9.1 x 10 9 1.6 x 10 8 1.0 x 10 9 1.9 x 10 8 5.1 x 10 910 8.2 x 10 6 7.3 x 10 9 9.1 x 10 7 9.7 x 10 8 71 x 10 7 3.9 x 10 911 3.1 x 10 6 9.8 x 10 8 7.5 x 10 7 8.2 x 10 8 1.9 x 10 7 2.7 x 10 912 9.4 x 10 5 8.1 x 10 8 4.6 x 10 7 6.7 x 10 8 8.3 x 10 6 1.2 x 10 913 1.6 x 10 5 7.6 x 10 8 9.1 x 10 6 4.9 x 10 8 2.1 x 10 6 8.1 x 10 814 6.5 x 10 4 6.5 x 10 8 7.3 x 10 5 3.0 x 10 8 8.5 x 10 5 7.7 x 10 8Note: A, B and C yeast samples were stored at room temperature at (30-35°C) and A-1, B-1 and C-1 yeast samples were stored inrefrigerator at (7-10°C).The Fermentograph was used to determine the activity of theyeast samples with the time consumed by each yeast sample toevolve 1000 cc of carbon dioxide. The results were presentedin Table (8). The time consumed by each yeast sample toproduce the certain amount of gas increased with the storagetime. Samples stored at the room temperature havedeteriorated more rapidly than those stored in the refrigerator.There are significant differences in activity (at P≤0.05 level) ofsample A and A-1. The same findings were found of samplesB, B-1, C and C-1. The activity deterioration is more rapidunder aerobic conditions and at room temperature because themaintenance requirements of the yeast increase under suchconditions. The activity results, obtained in this study, are inagreement with the results of [33] who grouped the yeast inthree groups according to their gas generation. Yeasts needless than 60 minutes for dough rising are of good quality.Yeasts need 60-100 minutes are moderate and yeasts needover 100 minutes are of poor quality. The deteriorationpercentage of each sample was calculated as describedpreviously.As shown in Figures 1, 2 and 3, sample A which stored atroom temperature, had 300% deterioration percentage by theend of 14 weeks storage period. Sample B condition wassimilar to sample A while sample C reached almost 350% ofits deterioration activity. The deterioration percentage ofsample A-1 after 11 weeks, was similar to the deteriorationpercentage of sample A stored for six weeks. After 11 weeks,sample B-1 had the same value as sample B when 5 weeksstorage at room temperature. Sample C-1 had the similarresults as sample C after five weeks storage.Baking properties of bread component for each yeast samplewere assessed by measuring the specific volumes of bakedbread. The specific volume represented the leavening ofbaker’s yeast because it increased in proportion to theresidential gassing power in the dough. The specific volumesof the bread before and after storage were compared
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