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

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

Journal of Applied and Industrial Sciences, 2013, 1 (2): 6-15, ISSN: 2328-4595 (PRINT), ISSN: 2328-4609 (ONLINE)Table (8). Time in Minutes Needed To Produce 1000 Cm 3 CO 2 during Storage of Samples A, A-1, B, B-I, C and.C-111Storageduration(week)Samples (Minutes)A A-1 B B-1 C C-11 48 46 50 48 38 362 51 49 56 50 41 393 62 50 66 54 49 424 75 51 89 56 54 495 81 52 98 57 67 516 90 53 116 59 72 527 102 55 121 60 88 548 111 59 128 62 100 569 121 65 133 68 108 5710 129 80 141 88 120 6411 140 92 153 97 127 8012 151 98 168 103 140 9513 162 102 176 108 152 9814 175 108 187 114 160 103Note: Samples A, B and C stored at room temperature (30-35°C). Samples A-1, B-1 and C-1 stored in refrigerator (7-10°C)Fig.1: The Deterioration percentage of sample A Stored at room temperature (30 o - 35 0 C) and sample A-1 (stored in refrigerator7 o - 10 0 C)Deterioration % = F.T. of yeast sample in storage - F.T. of yeast sample before storageF.T. of yeast sample before storage,Where: F.T.: Fermentation Time

Deterioration(%)Journal of Applied and Industrial Sciences, 2013, 1 (2): 6-15, ISSN: 2328-4595 (PRINT), ISSN: 2328-4609 (ONLINE)123503002502001501005001 2 3 4 5 6 7 8 9 10 11 12 13 14Storage time (w eek )Fig. 2: The deterioration percentage of sample B stored at room temperature (30 o - 35 o C) and sample B-1 stored in refrigerator(7 o - 10 o C)Fig. 3: The deterioration percentage of sample C stored at room temperature (30 o - 35 o C) and sample C-1 stored in refrigerator(7 o - 10 o C)At zero time of the storage, samples A, B and C had similarspecific volumes ranging between 4.70 and 4.88 cc/gr. Duringthe period of storage yeast samples behavior were summarizedin Table (9). The specific volume values exhibited significantdecreases (at P< 0.05 level) with the storage. The specificvolumes of bread containing the yeast strains stored at theroom temperature for one week, dropped to 4.80, 4.71 and4.61 cc/gr for the samples C, A and B, respectively. Aftereight weeks storage, these values were drop to 3.35, 3.21 and3.17 cc/gr for samples C, A and B, respectively and theserecords indicated poor quality bread. Similar findings werefound with the samples stored in the refrigerator for elevenweeks of storage. The bread containing yeast strains stored inrefrigerator had higher specific volumes than that containingyeast strains stored at the room temperature. These resultsindicated that, the yeasts stored at room temperature, in opencontainers, gave poor bread quality after seven weeks ofstorage. Whereas, the yeasts stored in the refrigeratortemperature gave poor quality bread after eleven weeks ofstorage. One possible reason for this is that, baker’s yeast issusceptible to deterioration during storage, as a result ofdecreasing in the viable counts, and does not retain sufficient

Journal of Applied and Industrial Sciences, 2013, 1 (2): 6-15, ISSN: 2328-4595 (PRINT), ISSN: 2328-4609 (ONLINE)leavening ability after storage. The suggestion in this work isto consider the values of specific loaf volumes expected fromgood quality yeast are ranging between 3.5 and 4.8cc/gr.13Fluted pumpkin seed flour, when substituted up to 20% levelin bread making give acceptable loaf volume quality 1.75-2.80cm [41]Table (9). Specific Volume of the Loaves Containing Baker's Yeast Samples A, B, C, A-1, B-1 and C-1 stored for 14 weekStorageduration(week)Samples (cc/g)A A-1 B B-1 C C-11 4.71 4.75 4.61 4.64 4.81 4.832 4.52 4.62 4.50 4.49 4.57 4.683 4.36 4.47 4.29 4.31 4.42 4.524 4.14 4.23 4.01 4.13 4.19 4.385 3.83 4.12 3.81 4.05 3.92 4.286 3.68 4.04 3.61 3.93 3.74 4.157 3.44 3.98 3.35 3.82 3.48 4.078 3.21 3.90 3.17 3.72 3.35 3.979 3.19 3.81 3.10 3.61 3.29 3.6510 3.04 3.67 2.98 3.44 3.11 3.6111 2.82 3.36 2.71 3.21 2.87 3.4712 2.71 3.17 2.62 2.95 2.78 3.2813 2.48 3.01 2.41 2.82 2.54 3.1214 2.26 2.80 1.15 2.69 2.36 2.97Where: A, B, C.: yeast samples stored at room temperature (30-35°C) and A-1, B-1 And C-1: yeast samples stored inrefrigerator (7-10°C)During dough fermentation gluten maturation occurs,promoting extensibility and gas retention. These characteristicsprovide volume, texture, aroma, taste and colour to the doughand bread [8]. Therefore, dough quality is fundamental toobtain high quality bread. Patents on baker’s yeast withimproved characteristics such as aromatic or nutritiveproperties confirms recent interest for a very wide range oftailored –made yeast-based ingredients for bakery application[5]. At zero time of the storage, both external and internalcharacteristics of the bread, made with the yeast samples, wereevaluated. The results presented in Table (10), show highlyacceptable organoleptic quality of bread. In various storagetimes, the bread sensory evaluation results showed that, thecolor of the crumb was found stable as light yellow colour,whereas crust color, texture, taste and aroma were significantly(at P< 0.05 level) decreased with the time. It can be concludedthat bread with improved sensory characteristics can beobtained by using yeast with good leavening and flavourformation abilities. Salt-stressed Backer’s yeast made thebread softener and significantly improved sensory propertiesfor aroma, taste and overall acceptability [42].Questionnaire results were presented in Table (11).Hundred percent of all groceries are not selling compressedyeast or any Sudanese made yeast, while 100% and 20% ofsmall and large groceries, respectively sell the baker’s yeast inrepacked polyethylene plastic bags. More than 80% of theshopkeepers in large and small groceries had no idea about thebaker’s yeast, whether it is a living microorganism or not.They deal with baker’s yeast as a type of baking power. It wasnoticed that there is no information on the labels of the factorypacked yeast telling the sellers how to handle or store theyeast. In addition, there is no restriction given to them to avoidselling part of the factory-sealed packages

Journal of Applied and Industrial Sciences, 2013, 1 (2): 6-15, ISSN: 2328-4595 (PRINT), ISSN: 2328-4609 (ONLINE)Table (10) Organoleptic Assay of Bread Containing the Yeast Samples14Parameter Sample Crust Colour Crumb Colour Texture Taste AROMA OverallAcceptanceSample A B.S 4.7 a 4.4 a 4.3 a 4.7 a 4.2 a 4.3 aSample B B.S 4.2 a 4.6 a 4.3 a 4.6 a 4.4 a 4.7 aSample C B.S 4.5 a 4.5 a 4.7 a 4.7 a 4.4 a 4.7 aSample A I.S 1.8 b 4.2 a 1.2 c 1.8 b 1.2 c 1.1 cSample B I.S 2.1 b 4.3 a 1.3 c 1.5 c 1.5 b 1.1 cSample C I.S 1.6 c 4.1 a 1.2 c 1.7 c 1.9 b 1.3 cSample A-1/ I.S. 2.4 b 4.5 a 1.9 b 1.4 c 2.0 b 1.3 cSample B-1/ I.S. 3.1 b 4.2 a 2.0 b 1.6 c 2.1 b 1.2 cSample C-1/ I.S. 2.5 b 4.4 a 1.8 b 1.5 c 2.1 b 1.5 cMeans scores with the superscript letters are not significantly different at P>0.05 level.Score obtained indicated the following: 5 = Excellent. 4 = Very good. 3 =good. 2 = fair. 1 = Not accepted.Where: B.S: Sample of bread containing yeasts before storage and I.S: Samples of bread containing yeasts during storage.Table (11) Results of Questionnaire Made About Baker's Yeast Selling in Khartoum North AreaDescription Small Groceries (%) Large Groceries (%)Selling dry instant yeast 90 00Selling compressed yeast 00 00Selling locally made yeast 00 00Selling saf- instant yeast strain 90 100Selling mauripan yeast strain 20 70Selling fermipan yeast strain 10 20Selling other strains 10 40Repacking yeast in small bags 100 20Idea about Sudanese factory 20 10Idea about yeast is a livingmicroorganism (correct)2010IV. CONCLUSIONSThe Following conclusions were drawn from this study:1. All baker ’ s yeast samples tested were originally ofgood quality.2. The practice of repackaging of yeasts in smallamounts caused a depression in bread volumes,specific loaf volumes and sensory evaluation scoresof the bread.3. Storing repacked packages at room temperature wasfound to affect the quality of the yeasts samplesnegatively. This effect was also noticed in thesamples stored in the refrigerator but quite slowly.4. The practice of repacking in plastic bags and badstorage of the yeasts contribute to bad quality breadproduction.5. The bad quality of bread found in the markets may bedue to using baker's yeast stored in inept conditions.V. REFERENCES[1] Ministry of commerce.(1993) Sudanese Yeast and FermentationFactory, Al-Hassahesa; Personal communication.[2]. Hamad, S. H. (1989). Screening of Yeast Associated with Foodfrom the Sudan and their possible Application for Single Cell Proteinand Ethanol Production. Ph. Dissertation, Sudan, Berlin.[3] Lodder, J.; Sloaff, W. C. H. and Kreger. Van, R. I. (1956). Theclassification of yeast. In ''The chemistry and Biology of yeast''. (A.H. Cook edit.). 1-57. Academic Press Inc.Publishers, New York.[4] Rose, A. H. and Harrison, J. S. (1969). “The Yeast.” AcademicPress Inc. London.[5] Gèlinas, P (2009). Inventions on baker’s yeast strains andspecially ingradients. Recent Pat. Food Nutr. Agric., Vol (1), pp,104-132.[6] Yerushaml. L. and volesky, B. (1981). ExperimentalBioenergetics of Saccharomyces cerevisiae in Respiration andFermentation. Biotech and Bioeng., XXIII : 2373-2390''.[7] Jay, J. M. (1992). Modern food Microbiology. Fourth edition.Published by Van Vostrant Reinhold, New York.[8] Calvel, R.; Wurtz, R. L.; and MacGuine, J. J. (2001). “The Tasteof Bread.” Aspen, MD (2001).[9] Pejin, D. J; Grujic, O. S; Pejin, J. D and Kocic-Tanackov, S. D(2009). Effect of yeast storage temperature and flour composition onfermentative activities of backer’s yeast. Zbornik Matice srpske zaprirodne nauke (116) 305-313.[10] Loveday, S. M; Huang, V. T; Reid, D. S and Winger, R. G(2012). Water dynamics in fresh and frozen yeasted dough. Crit. Rev.Food Sci. Nutr, Vol 52 (5), pp 390-409.

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