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Nutrition & Food ScienceSugar utilization behavior of yeast (Saccharomyces cerevisae) types and doses on bread

qualityFaqir Muhammad Anjum Muhammad Zubair Sabir Muhammad Issa Khan Imran Pasha

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To cite this document:Faqir Muhammad Anjum Muhammad Zubair Sabir Muhammad Issa Khan Imran Pasha, (2010),"Sugar utilization behavior of yeast (Saccharomyces cerevisae) types and doses on bread quality", Nutrition & FooScience, Vol. 40 Iss 4 pp. 395 - 402Permanent link to this document:http://dx.doi.org/10.1108/00346651011062041

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Faqir M. Anjum, Imran Pasha, Kashif Ghafoor, M. Issa Khan, M. Ali Raza, (2008),"Preparation of sourdoughbread using a blend of bacterial culture and baker's yeast", Nutrition & Food Science, Vol. 38 Iss 2 pp.146-153 http://dx.doi.org/10.1108/00346650810863028

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Sugar utilizatiobehavior o

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Nutrition & Food Scie

Vol. 40 No. 4, 2

pp. 395-

# Emerald Group Publishing Lim

0034-6

DOI 10.1108/00346651011062

Sugar utilization behavior ofyeast (Saccharomyces cerevisae )

types and doses on bread qualityFaqir Muhammad Anjum, Muhammad Zubair Sabir,

Muhammad Issa Khan and Imran Pasha National Institute of Food Science & Technology, University of Agriculture,

Faisalabad, Pakistan

Abstract

Purpose – The yeast Saccharomyces cerevisae is the most important ingredient of leavened productsand is best known for its characteristic physiological property: the rapid fermentation of sugar toethanol and carbon dioxide. The purpose of this paper is to exploit this feature to determine the effectof three commercially available yeast types: Instant, Dried, and Fresh on sugar utilization during the

fermentation process and bread quality.Design/methodology/approach – Three commercially available yeast types – Instant, Dried, andFresh were used at three levels, i.e. 0.50, 0.75 and 1.00 percent in order to assess sugar utilizationduring the fermentation process and bread quality after baking.Findings – The rate of utilization of glucose was much faster than fructose and sucrose. Instant yeast at1.00 percent exhibited maximum sugar utilization during the fermentation process. It also contributed toimproving the bread texture, loaf volume, grain texture, crust and crumb color. Dried and Fresh typescould not depict any significant difference in their sugar utilization behavior and bread quality. The resultsindicated that yeast quality as well as quantity is one of the major indices of bread quality.Practical implications – The findingsof the research can be used by bakers in order to selectthe properyeast type and its level for production of quality bread. It also gives an idea about sugar type best suitedfor bread production.Originality/value – The paper describes unique research work, as both yeast types, along with theirlevels, are tested for their fermentation capacity on different types of sugars, as fermentation is animportant step in bread making.

Keywords Fermentation, Sugar, Bakery products

Paper type Research paper

IntroductionYeast is amongst one the most important ingredient of the bread, mainly responsiblefor carrying out fermentation activities, thus converting sugars into CO2 and ethanol.The preferable sugars for yeast are simple sugars because the yeast readily utilizesthem. Yeast exhibits a variable preference to different sugars, namely sucrose(converted to glucose and fructose by yeast invertase or sucrase), glucose, fructose andmaltose (converted to glucose by yeast maltase). Yeast also determines the end product

quality through its fermentation behavior. Commercial baking plants select the yeastaccording to its performing behavior towards loaf volume, proofing, and fermentationtime and bread textural characteristics such as crust color, grain texture and overallacceptability. Fresh yeast would be yellow brown to gray in color, springy to touch andbreak easily. The average composition of Fresh yeast is 15 percent protein, 10 percentcarbohydrates, 0.5 percent fat, 2.8 percent mineral matters and 68-73 percent moisturecontent. The fresh and dry yeast maintain its activity best at 32-34 F (Sultan, 1969).

The simple sugars, glucose and fructose are consumed by yeast during fermentationprocess. The simpler sugars are produced by the action of enzymes on larger molecules of sucrose, maltose, starch and other complex carbohydrates. The yeast contains yeast

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Calcium propionate 0.25 percentImprover 0.20 percent

Sensory evaluation

Bread prepared was evaluated by a panel of highly trained judges for the sensoryparameters i.e. bread internal and external characteristics by using the method of Matz(1960).

Statistical analysisData obtained from different parameters were subjected to statistical analysis asdescribed by Steel et al. (1997).

Results and discussionFlour used for bread preparation by using different types of yeast was also analyzedfor the chemical as well as its rheological properties. The chemical analysis of flourshown in Table I(a) depicted that moisture content in the flour was 8.59 percent, protein10.06 percent, crude fat 0.96 percent and crude fiber was 0.52 percent. Moisture contentof flour was lower as commercial wheat flour was used in the research study in themonths of May-June. Different results for the flour composition as he used a purevariety ‘‘Inqalab’’ in his research study while in our study the flour may be mixture of variety as flour was obtained from local market (Qamar, 1994).

Dough rheology is an important parameter from the baker’s standpoint as it tellsabout the dough behavior in mixing, fermentation and subsequent baking process. It alsocontributes to the volume and texture of the bread. Wheat cultivars grown in Pakistanare generally medium strong (Anjum et al., 2000). Farinograhpic study revealed thatflour absorbs 60 percent water for its proper mixing and to convert into dough. Doughremains stable for 7 min during the process of mixing as shown in Table I(b). Farinogram

indicated that flour under study contain sufficient protein to prepare good quality bread.

TablePhysico-chemiccharacteristics

wheat flo

Constituents % age

(a) Chemical composition of wheat flour Moisture content 8.59Crude protein content 10.06Crude fat content 0.96Crude fiber content 0.52Total ash content 0.62

Farinograph characteristics % age/min

(b) Physical characteristics of wheat flour Water absorption 60%Arrival time 1 minDough development time 2 minDeparture time 8 minDough stability 7 minTolerance index 40 BUSoftening of dough 80 BU

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In the process of dough fermentation small amount of organic acids are also producedin addition to ethyl alcohol and CO2. Organic acid produced during the process of fermentation includes lactic acid, propionic acid, succinic acid, fumaric acid andpyruvic acid. Acetic acid is the most prevalent among all. As dough maturation

progresses and fermentation precedes the dough become richer in organic acids andthis increase in acidic content ultimately lower the pH of the dough. Low pH of thedough enhances the aroma and keeping quality of the bread. Dough pH exhibits ainverse pattern in relation to the yeast doses. Increasing yeast doses lowered the pH byincreased fermentation in dough. Yeast generally exhibits considerable tolerance to pHbut shows ceasing activity at pH 2.00 or 8.00. At yeast level of 1 percent highest pHvalue (6.2) was found for Fresh while lowest value (5.05) was observed for Instantbrand. Instant yeast at 1 percent in fermented samples showed maximum decline withcomparison to Dried and Fresh. Maximum sugar utilization was executed by Instantyeast as shown in Table II. The sugar utilization performances of other yeasts werelower and exhibit higher level for dough pH. Titratable acidity (TTA) of dough alsovaries with pH of dough, as for lower pH value the TTA will be higher and opposite the

case for higher value of pH as shown in Table II.Sugar utilization behavior was determined by using HPLC. During the process of

fermentation sucrose contents of dough decreases with the increase in fructose andglucose contents of the dough as shown in Figures 1-3. These results indicate that sucrosecontents are readily decomposed into simpler sugars. Level of sucrose in dough containingyeast at a level 0.5 percent were 0.1908 mg/ml for Instant and 0.1846 mg/ml for Dried whilea value of 0.1471 mg/ml for Fresh (Figure 1). These values for sucrose level decreasesduring fermentation to 0.1642 for Instant, 0.1564 for Dried and 0.1579 for Fresh. Glucosequantity in dough after 1 h fermentation containing 1.0 percent yeast was observed to be0.3915 mg/ml, which after 2 h fermentation reduced to 0.2073 mg/ml. It suggest thatduring 1 h process of fermentation Instant yeast utilizes 0.1842 mg/ml glucose, which ismaximum value for glucose consumption as compared to others two types of yeast as

shown in Figure 1.

Table II.Effect of fermentationand proofing on pH andTTA of bread dough

Yeast (%) Yeast type Samples pH TTA

0.5 Instant Proofed 6.18 0.50Fermented 5.85 1.40

Dried Proofed 6.17 0.65Fermented 5.84 1.30

Fresh Proofed 6.20 0.50Fermented 5.85 1.40







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Dried yeast used at level of 0.5 percent consumed 0.2765 mg/ml glucose during 1 hfermentation and this level is reduced 0.2551 after 2 h fermentation time. Dried yeast in1 h fermentation consumed 0.0514 mg/ml of glucose (Figure 2). When the yeast levelwas increased to 1.0 percent the per hour glucose utilization recorded 0.0800 mg/ml. Byobserving the glucose utilization rates indicated at 0.5 and 1.0 percent yeast doses, thedata clearly showed that when the concentration of yeast in a sugar containing solutionis increased it subsequently triggers the sugar utilization. The minimum utilization

Figure Utilization of sucrose different types of yeas

Figure Utilization of glucose different types of yeas

Figure Utilization of fructose

different types of yeas

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was observed for Fresh yeast as shown in Figure 2. Its glucose utilization rates were0.0100 mg/ml/h when its quantity is 0.5 percent. Even at higher concentration of theyeast in the solution its consumption did not increase significantly.

Fructose contents were higher in 2 h fermentation irrespective of type and dose of

the yeast as indicated in Figure 3. Hence, a variable pattern of yeast in the utilization of sugars was observed. The use of 1.0 percent yeast exhibited maximum reduction in theglucose contents. Amore et al. (1989) fermented glucose and fructose separately; theiruptake profile indicated that both are used at same time. Fermentation conducted in themedium showed that sucrose is utilized at slow rate while glucose is utilized at twicethe rate of fructose. Preferential uptake of glucose took place by the inversion of sucrose into glucose and fructose by the action of invertase enzyme.

Yeast types also affect the loaf volume significantly with maximum volume 529 forInstant yeast while lowest volume 486 was found for Dried yeast. Fresh yeast give loaf volume between the volume of Instant and Dried. As for interaction of treatment and yeasttype is concerned, minimum volume was found for Dried at a level of 0.5 percent andmaximum volume was found for Instant at a level of 1.0 percent. Results as shown in Table

III indicated that volume of loaf increases with increase in the yeast level. However, yeastbrand Instant show better results as compared to other brands in context of loaf volume.

Moisture loss from the loaf of bread was determined after every 24 h during storageof 96 h. It is evident from results regarding moisture loss as given in Table IV that 0.5percent Dried yeast showed maximum loss in moisture during storage. In contrastInstant yeast at a level of 0.5 percent showed minimum loss in moisture contents of thebread loaf as compared to Instant and Fresh. Higher dose levels of Instant also showminimum moisture loss in moisture content, which is desirable attribute in bread asmoisture keeps the bread loaf soft and maintains its freshness.

Bread prepared by using different types of yeast at variable doses was presentedto a panel of judges for the sensory evaluation. Bread was evaluated for bothexternal and internal characteristics by the panel of judges and mean scoresobtained by different parameters are given in Table V. It is evident from the results

Table IV.Moisture loss from breadafter every 24 h(g)

Yeast concentration Yeast type 24 h(g) 48 h(g) 72 h(g) 96 h(g)

0.5% Instant 1.16 1.27 1.29 1.31Dried 1.61 1.82 1.84 1.86

Pak Maya 1.47 1.69 1.24 1.76

0.75% Instant 1.17 1.29 1.35 1.35Dried 1.94 2.17 2.26 2.26

Pak Maya 1.65 1.91 2.00 2.01

1.00% instant Instant 1.88 1.98 2.05 2.13Dried 2.00 2.20 2.28 2.37

Pak Maya 2.0 2.20 2.28 2.38

Table III.Volume of breadprepared by differentyeast types

Yeast typesTreatments

0.5% 0.75% 1.00%

Instant 490 547 550Dried 401 541 517Pak Maya 430 540 532

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of sensory evaluation that yeast types and dose level affect the crust color andcharacteristics of crust along with loaf volume. Symmetry of bread and evenness of bake are not affected by the yeast types and yeast dose levels. Internalcharacteristics like grain, bread taste and texture are significantly affected by theyeast types and dose levels. Bread aroma among the internal characteristics showednon-significant results with respect to yeast levels and yeast types. Internal andexternal characteristics are not affected y the interaction of yeast levels and yeasttypes. However, Instant yeast as compared to two other brands gave better resultsin respect of bread character and further that yeast at a level of 1.0 percent gavebetter results for different quality attribute of bread.

We can conclude from this study that yeast types have different behavior on sugarutilization and acidity during fermentation and proofing process. Consequently yeasttypes differences also reflect the quality.

References

AACC (2000), Approved Methods of the American Association of Cereal Chemists , The AmericanAssociation of Cereal Chemists, Inc., St Paul, MN.

Amore, R., Wilhelm, M. and Hollenberg, C.P. (1989), ‘‘The fermentation of xylose – an analysis of

the expression of Bacillus and Actinoplanes xylose isomerase genes in yeast’’, Applied Microbiology and Biotechnology, Vol. 30, pp. 351-7.

Anjum, F.M., Lookhart, G.L. and Walker, C.E. (2000), ‘‘Electrophoretic identification of hard white

spring wheats grown at different locations in Pakistan in different years’’, Journal of the

Science of Food and Agriculture, Vol. 80, pp. 1155-61.

Matz, S.A. (1960), Bakery Technology and Engineering , The AVI Pub. Inc., Westport, CT.

Matz, S.A. (1996), Bakery Technology and Engineering , CBS Pub. and Distributors, NewDelhi.

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Reed, G. (1982), ‘‘Production of bakers’ yeast’’, in Reed, G. (Ed.), Industrial Microbiology, AVIPublishing Company, Westport, CT, pp. 593-633.

Table Sensory evaluation

bread prepared by usindifferent types of yea

Characters

TreatmentsInstant Dried Pak Maya

0.50% 0.75% 1.00% 0.50% 0.75% 1.00% 0.50% 0.75% 1.00%

Color of crust 4.0 6.0 7.0 3.0 5.0 6.0 2.90 5.0 6.0Symmetry 4.0 4.0 4.0 4.0 3.8 4.0 4.0 4.3 3.9Evenness of bake 2.0 2.0 2.0 2.0 2.0 2.1 2.0 2.0 2.0Characters of crust 2.0 2.0 3.0 1.0 1.0 2.0 1.0 1.0 2.0Grain 10.0 11.0 13.4 9.0 10.0 12.3 9.0 10.4 12.0Color of crumb 8.0 8.0 7.9 8.0 8.0 7.9 8.0 8.0 8.0Aroma 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0Taste 17.0 18.0 16.0 16.0 17.0 15.0 15.9 17.0 14.9Bread texture 12.0 13.0 14.0 11.0 12.0 13.0 11.0 12.0 13.0Acceptability 7.3 8.0 8.4 6.7 7.4 7.8 6.7 7.4 7.8

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Steel, R.G.D., Torrie, J.H. and Dickey, D. (1997), Principles and Procedures of Statistics, 3rd ed.,McGraw-Hill Book Co. Inc., New York, NY.

Sultan, W.J. (1969), Practical Baking , The AVI Pub. Inc., Westport, CT.

Torbjorn, L. and Hagernal, B.H. (1989), ‘‘Fermentation of lingo cellulose hydrolysis with yeast

and xylose isomerase’’, Enzyme and Microbial Technology, Vol. 11, pp. 583-89.

Corresponding authorMuhammad Issa Khan can be contacted at: [email protected]

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