The Open Microbiology Journal




ISSN: 1874-2858 ― Volume 13, 2019

Organoleptic Analysis of Doughs Fermented with Yeasts From A Nigerian Palm Wine (Elaeis guineensis) and Certain Commercial Yeasts



Boboye B*, Dayo-Owoyemi I, Akinyosoye F. A
Department of Microbiology, Federal University of Technology, P. M. B. 704, Akure, Ondo State, Nigeria

Abstract

Yeasts isolated from a freshly tapped palm wine obtained from Akure, Nigeria were identified as Schizosaccharomyces pombe, Saccharomyces cerevisiae, Debaryomyces hansenii, Geotrichum lactis and Zygosaccharomyces rouxii. Each of the isolates was used to ferment wheat flour dough and baked. Sensory analysis of the doughs was carried out on leavening, texture, aroma, taste and appearance. Saccharomyces cerevisiae performed best in leavening the dough while Debaryomyces hansenii produced doughs with the best taste and aroma. Appearances of the doughs made with all the isolated yeasts did not differ significantly (P<0.05) from that of the dough that lacked yeast.

Key Words: A Nigerian palm wine, Yeasts, Sensory properties of dough.


Article Information


Identifiers and Pagination:

Year: 2008
Volume: 2
First Page: 115
Last Page: 119
Publisher Id: TOMICROJ-2-115
DOI: 10.2174/1874285800802010115

Article History:

Received Date: 31/7/2008
Revision Received Date: 05/8/2008
Acceptance Date: 11/8/2008
Electronic publication date: 17/9/2008
Collection year: 2008

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© Dayo-Owoyemi et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided thework is properly cited.


* Address correspondence to this author at the Department of Microbiology, Federal University of Technology, P. M. B. 704, Akure, Ondo State, Nigeria; E-mail: boboye_b@yahoo.com




INTRODUCTION

Palm wine is an alcoholic beverage produced by the natural fermentation of the sap of various palm trees. Among the palms used are coconut (Cocus nucifera), oil palm (Elaeis guineensis), date palm (Phoenix clotifera) and raphia palm (Raphia hookeri) [1Okagbue RN. A note on the leavening activity of yeasts associated with palm wine J Appl Bacteriol 1988; 64: 235-40.]. The unfermented sap is a clean, sweet, colourless syrup containing about 10-12% (w/v) sugar, which is mainly sucrose [2Ogbulie TE, Ogbulie JN, Njoku HO. Comparative study on the shelf life stability of palm wine from Elaeis guineensis and Raphia hookeri obtained from okigwe, Nigeria Afr J Biotechnol 2007; 6(7): 914-22.]. Upon fermentation by the natural microflora, the level of this sugar decreases as it converts to alcohol and other products whereas the sap becomes milky white due to the increased microbial suspension resulting from the prolific growth of fermenting organisms [3Obire O. Activity of yeast species in palm sap obtained from three areas in Edo state, Nigeria J Appl Sci Environ Manage 2005; 9: 25-30.].

Previous study on the microbiology of Elaeis guineensis have incriminated several bacteria and yeast flora to be involved in the fermentation process [2Ogbulie TE, Ogbulie JN, Njoku HO. Comparative study on the shelf life stability of palm wine from Elaeis guineensis and Raphia hookeri obtained from okigwe, Nigeria Afr J Biotechnol 2007; 6(7): 914-22.]. Ezenroye and Okerentugba [4Ezenronye OU, Okerentugba PO. Genetic and physiological variant of yeasts selected from palm wine Mycopathologia 2001; 15(2): 85-9.] reported the genetically and physiologically different isolated yeasts from palm wine. These variants include nine species of Saccharomyces cerevisiae, three Candida species, one Schizosaccharomyces species and one Kluyveromyces species.

Literatures have shown that bakers have used palm wine as a cheap alternative dough-leavening agent. Palm wine is able to raise dough because it harbours many yeast species. However, fermented baked dough produced using palm wine as a substitute for baker’s yeast is usually characterized by a sharp sour taste, pronounced palm wine flavour and short shelf life (Personal communication in 2007 with Kole, Kole bakery, Akure, Ondo State, Nigeria). This sour taste and short shelf life could be attributed to the large number of microbial flora, particularly the lactic acid bacteria present in palm wine [5Frazier WC, Westhoff DC. Food Microbiology In: New Delhi: Tata McGraw-Hill publishing Company Limited 1995; pp. 384-96.] that produce metabolites undesirable for bread production.

Elaeis guineensis harbours many yeast species [2Ogbulie TE, Ogbulie JN, Njoku HO. Comparative study on the shelf life stability of palm wine from Elaeis guineensis and Raphia hookeri obtained from okigwe, Nigeria Afr J Biotechnol 2007; 6(7): 914-22.]. Although considerable amount of work has been done in characterizing the yeast strains present in palm wine, there are only few information available on the leavening ability of the yeasts. Also, the location or environment where the palm wine is can determine the exact type of yeasts present in the drink. Therefore, this work was designed to isolate and identify yeasts present in palm wine freshly tapped in Akure, Nigeria and determine the dough leavening ability of these yeasts. The organoleptic properties of the doughs made with these microbes were investigated.

MATERIALS AND METHODOLOGY

Microbial Analysis

A 1 mL aliquot of freshly tapped palm wine was aseptically collected from an Ijoka farm, Akure, Nigeria. The sample was serially diluted 100 folds after which 1 mL was pour-plated [6Harrigan WF. Laboratory methods in food microbiology In: San Diego Carlifornia: Academic Press 1998; pp. 36-84.] in triplicate using PDA containing 0.1% (w/v) lactic acid. The plates were placed at 30°C ± 2°C for 48 – 72 hours. After good growth of the colonies, distinct colonies were purified on fresh PDA by streaking. Each colony was confirmed to be yeast by examining it under a light microscope using oil immersion objective after staining with lactophenol-in-cotton-blue dye. Pure isolates were placed on PDA slants and stored at 4°C until needed.

The yeasts isolate were characterized based on their cultural characteristics (colony shapes, pigment, elevation, edge and surface appearance). Biochemical characterization of the isolates was done by testing for ability of the yeasts to ferment and assimilate sugars, utilize nitrate, form pellicle, spore, pseudomycelium and mycelium according to the methods of Harrigan, Olutiola et al., Barnett et al. and Fawole & Oso [6Harrigan WF. Laboratory methods in food microbiology In: San Diego Carlifornia: Academic Press 1998; pp. 36-84.-9Fawole MO, Oso BA. Laboratory manual in microbiology 3rd ed 2001; 102-50.].

Cultivation of Yeast Isolates for Dough Fermentation

The yeasts isolated were cultured separately at 25°C ± 2°C in peptone broth medium containing 20% (w/v) glucose and lactic acid at concentration of 0.2% in 1 litre conical flask equipped with air locks. The set-up was agitated continuously for 72 hours in rotary shaker regulated at 150 rpm. After good growth was observed, the biomass concentrate for each yeast species was obtained by centrifuging it in an MSE centrifuge machine at 12,168 x 103 g for 10 min. The yeast concentrates were washed sufficiently with sterile distilled water after which they were resuspended in sterile distilled water. The same procedure was applied to the commercial yeasts (Saf-instant and STK Royal) used as controls.

Determination of Fermentative Ability of the Yeasts

All the yeast isolates were used to ferment dough in order to test their fermentative ability. Samples of dough were prepared as described by Cauvian and Young [10Cauvian SP, Young L. Technology of bread making In: London: Blackie Academy and Professional 1998; pp. 210-35.]. Each dough sample contained wheat, flour, salt, water, sugar and fat. All the ingredients were properly mixed. Each yeast isolate (1.41x 109 Cfu/mL) was used to ferment the dough. Baker’s yeast (STK Royal and Saf- instant) were used separately as positive control yeasts to ferment the dough. Another set of dough formulation that did not contain any yeast sample was prepared as the negative control. The dough samples were left to ferment at room temperature at 37°C ± 2°C for about 1 hour. The doughs were baked in an oven for 1 hr at 200°C.

Comparative Analysis of the Baked Dough Samples

The baked dough samples were subjected to sensory analyses by using panel of 26 enlightened judges to evaluate the following physical parameters namely: leavening, taste, texture, appearance and aroma. Five points grade was used in the analysis starting with Excellent =5, Very Good = 4, Good = 3, Satisfactory = 2 and Poor = 1.

Analysis of Data

All data obtained from sensory evaluation were subjected to statistical analysis by using Analysis of Variance and DUNCAN Multiple Range Test. Significance of variations in the analyzed data was tested at 95% confidence limit.

RESULTS AND DISCUSSION

Five morphologically different yeast strains namely Schizosaccharomyces pombe, Debaryomyces hansenii, Geotrichum lactis, Saccharomyces cerevisiae and Zygosac-charo-myces rouxii were obtained from the freshly tapped palm wine (Table 1). The quantity and complexity of yeasts isolated from the palm wine used in this study is in agreement with the findings of Ezenronye and Okerentugba [4Ezenronye OU, Okerentugba PO. Genetic and physiological variant of yeasts selected from palm wine Mycopathologia 2001; 15(2): 85-9.].

Table 1.

Morphological and Biochemical Characteristics of the Yeasts Isolated from Palm Wine in Akure, Nigeria




The complexity and variation in species of yeasts isolated is related to the fact that the yeasts originate from several sources such as the tapping container (which may retain some yeasts) and from the tapping environment. Furthermore, palm wine contains a high level of sucrose (10-12%). This high sugar level favours the growth of yeasts. It further gives credence to the general belief held in the early days of research that yeasts are found in sugary substances [11Phaff HJ. Isolation of biotechnological important organisms from nature In: New York: Oxford Press 1990; pp. 384-5.].

The organoleptic properties of doughs fermented with the various yeast isolates are presented in Figs. 1-5. The figures show that they compared well with doughs produced using commercial yeasts (Saf–instant and STK Royal) in all sensory attributes tested (leavening, texture, aroma, taste and appearance). All the isolates showed fermentative ability as depicted by their leavening activities (Fig. 1). Mean ratings of the leavening activities of the yeasts range between 2.33 (Zygosaccharomyces rouxii) and 2.83 (Saccharomyces cerevisiae). This corresponds to good leavening abilities on the sensory scale used at significant level of P<0.05.

Fig. (1)

Dough leavening activities of the various yeasts isolated from palm wine.



Fig. (2)

Texture of baked doughs made with the various yeasts isolated from palm wine.



Fig. (3)

Aroma of baked doughs made with the various yeasts isolated from palm wine.



Fig. (4)

Taste of baked doughs made with the various yeasts isolated from palm wine.



Fig. (5)

Appearance of baked doughs made with the various yeasts isolated frompalm wine.



The analysis of variance (ANOVA) shows that one of the commercial yeasts (Saf-instant) did not differ significantly from Schizosaccharomyces cerevisiae and Debaryomyces hanseni (P<0.05) in its leavening performance. The commercial yeasts STK Royal and Saf-instant had mean leavening activities of 2.70 and 2.40 respectively while the negative control (dough which lacked yeast) scored 2.29.

When compared with the negative control, the data showed that the isolated yeasts increased the size of doughs which they fermented considerably. This confirms the basis of using palm wine as a substitute for baker’s yeast by some bakers. The result is supported by the abilities of the yeasts to ferment sugars especially glucose and fructose, the break down of which brings about the release of carbon dioxide that causes dough to rise. The highest leavening activity recorded for S. cerevisiae indicates that it is the best biological wheat dough leavener obtained in this work because it performed better than the two commercial yeasts used as controls. The result is in agreement with the findings of Somiari and Udoh [12Somiari RI, Udoh AE. Evaluation of the performance of yeasts isolated from sap of Elaeis guineensis in dough leavening J Food Niger 1993; 1: 34-44.] and Adenaike et al. [13Adenaike O, Ameh JB, Whong CMZ. Comparative studies of the fermentative capacity of baker’s yeast and local yeast strains (Saccharomyces species) isolated from fermented beverages Book of Abstracts for the Annual Conference of Nigerian Mycological Society 2006; 18-9.] who reported that Saccharomyces species isolated from palm wine were found to be the best in leavening wheat dough.

The mean texture ratings obtained for the doughs fermented with the yeast isolates range between 2.84 (S. cerevisiae) and 2.14 (Zygosaccharomyces rouxii) (Fig. 2). This score range falls within good on the sensory scale used. The texture score recorded for S. cerevisiae followed the same trend as its leavening activity since the highest texture score was obtained for it. Olorunfemi and Adetuyi [14Olorunfemi OB, Adetuyi FA. Isolation of baking yeasts from naturally fermented pineapple J Food Agric Environ 2005; 3(1): 115-7.] reported a similar finding. Geotrichum lactis had the next high score for texture (2.82) followed by Debaryomyces hansenii and Schizosaccharomyces cerevisiae at 2.56 and 2.40 ratings respectively. Generally, the texture ratings of doughs fermented with these yeasts are at very close range to their leavening activity ratings, thus suggesting that besides causing dough to rise, the yeasts have improved the texture of the doughs they fermented. This confirmed the statement of Corriher [15Corriher S. Yeast crucial role in bread making Fine Cooking 2001; 43: 80-1.] that expansion of dough due to the carbon dioxide produced by yeasts leads to a characteristic porosity and texture of fermented baked dough. The low leavening activity and texture ratings of the negative control (dough which lacked yeast) confirms the effect of yeast on the fermented baked doughs.

Doughs fermented with the yeasts showed varying acceptance levels of aroma (Fig. 3). Debaryomyces hansenii produced dough with the best aroma (3.16). This was followed by Saccharomyces cerevisiae, Schizosaccharomyces pombe, Zygosaccharomyces rouxii and Geotrichum lactis with aroma ratings of 2.91, 2.80, 2.67 and 2.65 respectively. All the yeasts produced doughs with aroma ratings comparable with those of the commercial yeasts. The good and very good ratings of aroma indicate that the yeasts were able to produce compounds such as carbonyls, aldehydes and ketones that have imparted appealing flavours into the doughs.

The mean taste and appearance scores obtained for the dough fermented with the isolated yeasts and those of the commercial yeasts as well as the dough which lacked yeast range between 2.87 and 3.32 for taste and 2.76 and 3.17 for appearance (Figs. 4 and 5). The taste and appearance of the positive control did not differ significantly from the negative control. This means that the appearance and tastes of fermented doughs after baking may not be totally dependent on yeast activity, rather on the ingredient formulation as all the dough samples contained the ingredients in equal proportion. Hence, the iso-lated yeasts produced doughs with acceptable sensory attributes of taste and appearance with no significant difference from the commercially available yeasts.

In conclusion, this work has shown that palm wine contains yeasts that can produce baked doughs with good sensory attributes that compares favourably with commercial yeasts used for baking. The yeasts isolated from palm wine have shown considerable leavening activity.

ACKNOWLEDGEMENTS

The authors are grateful to G.F. Hassan in the Department of Crop, Soil and Pest Management of the University for his assistance to use relevant facilities and provision of some materials for this work. Akharaiyi, F. C. ensured that the bench work of this project was successful.

REFERENCES

[1] Okagbue RN. A note on the leavening activity of yeasts associated with palm wine J Appl Bacteriol 1988; 64: 235-40.
[2] Ogbulie TE, Ogbulie JN, Njoku HO. Comparative study on the shelf life stability of palm wine from Elaeis guineensis and Raphia hookeri obtained from okigwe, Nigeria Afr J Biotechnol 2007; 6(7): 914-22.
[3] Obire O. Activity of yeast species in palm sap obtained from three areas in Edo state, Nigeria J Appl Sci Environ Manage 2005; 9: 25-30.
[4] Ezenronye OU, Okerentugba PO. Genetic and physiological variant of yeasts selected from palm wine Mycopathologia 2001; 15(2): 85-9.
[5] Frazier WC, Westhoff DC. Food Microbiology In: New Delhi: Tata McGraw-Hill publishing Company Limited 1995; pp. 384-96.
[6] Harrigan WF. Laboratory methods in food microbiology In: San Diego Carlifornia: Academic Press 1998; pp. 36-84.
[7] Olutiola PO, Famurewa O, Sontag HG. An introduction to general microbiology: a practical approach In: Heldelberg: Published by Heideberger Verlagsanstalt and Druckerei GmbH 1991; pp. 42-.
[8] Barnett JA, Payne RW, Yarrow D. Yeast characteristics and identification In: London: Cambridge University Press 2000; pp. 100-21.
[9] Fawole MO, Oso BA. Laboratory manual in microbiology 3rd ed 2001; 102-50.
[10] Cauvian SP, Young L. Technology of bread making In: London: Blackie Academy and Professional 1998; pp. 210-35.
[11] Phaff HJ. Isolation of biotechnological important organisms from nature In: New York: Oxford Press 1990; pp. 384-5.
[12] Somiari RI, Udoh AE. Evaluation of the performance of yeasts isolated from sap of Elaeis guineensis in dough leavening J Food Niger 1993; 1: 34-44.
[13] Adenaike O, Ameh JB, Whong CMZ. Comparative studies of the fermentative capacity of baker’s yeast and local yeast strains (Saccharomyces species) isolated from fermented beverages Book of Abstracts for the Annual Conference of Nigerian Mycological Society 2006; 18-9.
[14] Olorunfemi OB, Adetuyi FA. Isolation of baking yeasts from naturally fermented pineapple J Food Agric Environ 2005; 3(1): 115-7.
[15] Corriher S. Yeast crucial role in bread making Fine Cooking 2001; 43: 80-1.

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