yeasts in foods and beverages: impact on product quality and safety

Yeasts in foods and beverages: impact on product qualityand safetyGraham H Fleet

The role of yeasts in food and beverage production extends

beyond the well-known bread, beer and wine fermentations.

Molecular analytical technologies have led to a major revision of

yeast taxonomy, and have facilitated the ecological study of

yeasts inmanyotherproducts. The mechanismsbywhichyeasts

grow in these ecosystems and impact on product quality can

now be studied at the level of gene expression. Their growth and

metabolic activities are moderated by a network of strain and

species interactions, including interactions with bacteria and

other fungi. Some yeasts have been developed as agents for the

biocontrol of food spoilage fungi, and others are being

considered as novel probiotic organisms. The association of

yeasts with opportunistic infections and other adverse

responses in humans raises new issues in the field of food safety.

AddressesSchool of Chemical Sciences and Engineering, The University of

New South Wales, Sydney, New South Wales, Australia

Corresponding author: Fleet, Graham H ([email protected])

Current Opinion in Biotechnology 2007, 18:170–175

This review comes from a themed issue on

Food biotechnology

Edited by Christophe Lacroix and Beat Mollet

Available online 1st February 2007

0958-1669/$ – see front matter

# 2007 Elsevier Ltd. All rights reserved.

DOI 10.1016/j.copbio.2007.01.010

IntroductionThe impact of yeasts on the production, quality and safety

of foods and beverages is intimately linked to their

ecology and biological activities. Recent advances in

understanding the taxonomy, ecology, physiology, bio-

chemistry and molecular biology of yeasts have stimu-

lated increased interest in their presence and significance

in foods and beverages. This has led to a deeper under-

standing of their roles in the fermentation of established

products, such as bread, beer and wine, and greater

awareness of their roles in the fermentation processes

associated with many other products. As the food industry

develops new products and processes, yeasts present new

challenges for their control and exploitation. Food safety

and the linkage between diet and health are issues of

major concern to the modern consumer, and yeasts have

emerging consequences in this context. On the positive

side, there is increasing interest in using yeasts as novel


probiotic and biocontrol agents, and for the nutrient for-

tification of foods. On the negative side, food-associated

yeasts could be an under-estimated source of infections

and other adverse health responses in humans.

Two books, entirely devoted to the occurrence and

significance of yeasts in foods and beverages, have

recently been published [1��,2��] and another includes

several chapters on food spoilage yeasts [3]. These pub-

lications demonstrate the expanding academic and indus-

trial interest in the field. This article reviews recent

developments in understanding the ecology and biology

of yeasts in foods and beverages and discusses how these

impact on product quality and safety.

New analytical toolsThe ability to isolate, enumerate and identify yeasts to

genus, species and strain levels is fundamental to under-

standing their occurrence and significance in foods and

beverages. Although cultural procedures remain basic to

these needs, molecular methods are making the study of

yeast ecology much more attractive and convenient than

ever before [4�,5].

Yeast taxonomy and species identification

Whereas the identification of new yeast isolates once

required the laborious completion of 80 to 100 morpho-

logical, biochemical and physiological analyses, this task is

now quickly achieved by DNA sequencing. The DNA

sequences of the genes encoding the D1/D2 domain of the

large (26S) subunit of ribosomal RNA are known for all

yeast species, and the sequence of the ITS1-ITS2 region of

rRNA, as well as other genes, is known for many. These

sequence–phylogenetic data have led to a complete revi-

sion of yeast taxonomy, and the description of many new

genera and species [6�]. Although sequencing of ribosomal

genes is now the accepted method for yeast identification,

restriction fragment length polymorphism (RFLP) analysis

of the ITS1-ITS2 region is a less expensive, faster alterna-

tive, and databases containing the results of such analyses

have been established for food yeasts [5].

Nucleic acid probes and real-time PCR detection methods

have been described for some species, such as Saccharo-myces cerevisiae, Brettanomyces bruxellensis and Zygosacchar-omyces bailii [4�,5,7], and a novel probe-flow cytometric

assay has been reported for various Candida species [8].

Strain differentiation

The distinctive character of many breads, beers and wines

can be linked to particular strains of S. cerevisiae used in

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http://dx.doi.org/10.1016/j.copbio.2007.01.010

Yeasts in foods and beverages Fleet 171

the fermentation [9]. Consequently, differentiation of

yeasts at the subspecies level is an important require-

ment. Molecular methods developed for this purpose

include pulsed-field gel electrophoresis (PFGE) of chro-

mosomal DNA and PCR-based methods such as random

amplification of polymorphic DNA (RAPD), amplified

fragment length polymorphism (AFLP), RFLP, and pro-

filing of microsatellite DNA. A simpler, faster method is

based on RFLP analysis of mitochondrial DNA, where no

PCR amplification of DNA is required [4�,5,10]. These

methods are not only useful for quality assurance typing

of yeast starter cultures and spoilage species, but they

have been used to reveal the ecological complexity of the

yeast flora associated with many food and beverage fer-

mentations. For example, it is now known that the

fermentation of wine, cheese, meat sausages and other

products not only involves the successional contributions

from many different species of yeast, but successional

growth of numerous strains within each species also

occurs [11,12�].

Culture-independent analysis

Most branches of microbial ecology now accept that viable

but non-culturable species occur in many habitats, includ-

ing foods and beverages. Detection of these organisms

requires extraction and analysis of the habitat DNA. One

approach that is finding increasing application is PCR in

conjunction with denaturing gradient gel electrophoresis

(DGGE) or temperature gradient gel electrophoresis

(TGGE). Total DNA is extracted from the food, and yeast

DNA is specifically amplified using PCR and primers

targeting regions of rDNA. The yeast DNA is then

resolved into amplicons for individual species by DGGE

or TGGE. These amplicons are extracted from the gel and

their species identity determined through sequence

analysis. PCR-DGGE/TGGE has been applied to analyse

the yeast communities associated with grapes, wine, sour-

dough, cocoa bean, coffee bean and meat sausage fermen-

tations [4�,5,13�,14,15]. There is good agreement in the

results obtained by cultural and PCR-DGGE/TGGE

methods, although in some cases species that were not

identified by agar culture were recovered by PCR-DGGE

— suggesting the presence of non-culturable flora. How-

ever, the reverse also occurs, where PCR-DGGE has not

detected yeasts that were isolated by culture. Many factors

affect the performance of PCR-DGGE/TGGE analyses

and further research is required to understand and optimize

the assay conditions [4�,13�].

Molecular understanding of the yeastresponseAs yeasts grow in foods and beverages, they utilize carbon

and nitrogen substrates and generate a vast array of

volatile and non-volatile metabolites that determine

the chemosensory properties of the product and its appeal

to the consumer. Some yeasts produce extracellular pro-

teases, lipases, amylases and pectinases that also impact


on product flavour and texture. The biochemistry of these

reactions and their linkage to product quality are gener-

ally well known [16��]. Now, genomic studies using

sequence, DNA array, and proteomic analyses enable

the linkage of these responses to the expression and

regulation of individual genes [17�]. Only a few such

studies have been performed with food and beverage

yeasts, and these have yielded interesting new insights.

For example, during wine and beer fermentations,

S. cerevisiae exhibits sequential expression and regulation

of many genes associated with carbon, nitrogen and sulfur

metabolism, as well as other genes required to tolerate

stresses such as high sugar concentration, low pH, ethanol

and nutrient deficiency [17�,18,19]. Genomic analyses

also give molecular explanations of the remarkable

tolerance of some yeasts to the extremes of high salt and

sugar contents in some foods (e.g. Debaryomyces hansenii in

cheese brines, Zygosaccharomyces rouxii in sugar syrups and

fruit juice concentrates), and to organic acid preservatives

in other foods (e.g. Z. bailii in salad dressings and soft

drinks) [20�].

Beyond brewing, baking and wine yeastsAlthough research on the contribution of S. cerevisiae to

beer, bread and wine fermentations continues to be a

focus, there is expanding interest in the role of yeasts in

other products [12�].

It is now well recognized that yeasts make important

contributions to the process of cheese maturation, where

various strains of D. hansenii, Yarrowia lipolytica, Kluyver-omyces marxianus and S. cerevisiae frequently grow to high

populations. They contribute to the development of

cheese flavour and texture through proteolysis, lipolysis,

utilization of lactic acid, fermentation of lactose and auto-

lysis of their biomass [21]. In a similar way, D. hansenii,Y. lipolytica and various Candida species affect flavour,

texture and colour development in fermented salami style

sausages and country cured hams [15,22]. Many breads,

especially sour dough varieties, are still produced by

traditional fermentation processes where no commercial

strains of baker’s yeast are added. Although indigenous

strains of S. cerevisiae are prominent in many of these

fermentations, other yeasts are significant and include

Saccharomyces exiguus, Candida milleri, Candida humilis,Candida krusei (Issatchenkia orientalis), Pichia anomala, Pichiamembranifaciens and Y. lipolyitica. These yeasts grow in

cooperation with lactic acid bacteria, giving distinctive

flavours to the final product [23].

High-value cash crops such as cocoa beans and coffee

beans also undergo processes that involve the action of

yeasts [24]. Coca beans must be fermented to generate

the precursors of chocolate flavour, and various species of

Saccharomyces, Hanseniaspora, Candida, Issatchenkia and

Pichia contribute to the process [14,25]. Coffee beans

are processed to remove pulp and other mucilaginous


172 Food biotechnology

materials that surround the seeds, and species of Candida,

Saccharomyces, Kluyveromyces, Saccharomycopsis, Hansenias-pora, Pichia and Arxula have been associated with these

fermentations [26]. A vast array of traditional fermented

foods and beverages are produced in African, Asian and

South American countries from raw materials such as

maize, wheat, cassava, rice, soy beans and fruit. Fermen-

tation is essential in contributing to the quality, safety and

nutritional value of these products. Aspects of their

microbial ecology are just starting to emerge, and demon-

strate important contributions from numerous yeast

species [27,28�].

Collectively, the ecological studies of yeasts in products

other than beer, bread and wine are providing the knowl-

edge base for developing a new generation of yeast starter

cultures, beyond S. cerevisiae.

Microbial interactions and biocontrolYeasts rarely occur in food and beverage ecosystems as

single cultures. Exceptions occur in highly processed

products where spoilage outbreaks by single, well-

adapted species are known: for example, Z. rouxii in high

sugar products [29].

Generally, most habitats are comprised of a mixture of

yeasts, bacteria, filamentous fungi and their viruses, and

product quality is determined by the interactive growth

and metabolic activity of the total microflora. Even within

yeasts themselves, there can be significant species and

strain interactions that impact on the population dynamics

of the ecosystem. The diversity and complexity of these

microbial interactions is just beginning to emerge

[11,30,31].

A network of yeast–yeast interactions occurs in most

ecosystems, and is observed in fermentations of wine,

cheese, meat, and cocoa beans. These interactions mani-

fest themselves as the successive growth and death of

different yeast species and strains within each species, as

the fermentation progresses. The mechanisms under-

lying these ecological shifts are numerous. Explanations

include the different rates of nutrient transport and

uptake by the different species and strains, their sensi-

tivities to metabolic end products (e.g. ethanol), and

responses to killer toxins [11]. Cell–cell interactions

might also occur through the production of quorum sen-

sing molecules [32�] and unexplained spatial phenomena

[33�]. Defining the metabolic outcomes of these inter-

actions and their impact on product quality remains a

greater challenge, as demonstrated by the interactive

effects of S. cerevisiae and Saccharomyces bayanus strains

on the chemical composition and flavour of wines [34].

Interactions between yeast and bacteria are often seen as

the inhibitory effects of yeasts on bacteria through etha-

nol production; however, the relationships are much


broader than this. The death and autolysis of yeast cells

releases vitamins and other nutrients that stimulate the

growth of important flavour-enhancing bacteria, such as

the malolactic bacteria in wine fermentations [11,31],

staphylolcocci, micrococci and brevibacteria during

cheese maturation [21], and lactic acid bacteria during

sour dough fermentations [23]. Ethanol, produced by

yeasts during cocoa bean fermentations, stimulates the

growth of acetic acid bacteria that oxidize the ethanol to

acetic acid. This acid is essential for killing the cocoa

beans (seeds) and triggering endogenous bean metab-

olism that generates the precursors of chocolate flavour

[24,25]. Some yeasts utilize the organic acids that occur in

cheeses, fruit products and salad dressings, causing an

increase in product pH and growth of spoilage and patho-

genic bacteria [30]. Some bacteria are antagonistic

towards yeasts. Excessive growth of lactic acid bacteria

and acetic acid bacteria on grapes produces acetic acid and

other substances that inhibit the growth of yeasts in grape

juice, causing stuck or sluggish wine fermentations and

loss of process efficiency [11,31].

Interactions between yeast and fungi have not been

widely studied, except in the context of biocontrol. Fun-

gal growth on wine grapes produces substances that

inhibit the growth of yeasts during grape juice fermenta-

tion [11]. By contrast, some yeasts improve the growth of

Penicillium spp. during the maturation of cheeses [35].

Several species within the genera Candida, Pichia, Metsch-nikowia, Cryptococcus and Pseudozyma have strong antifun-

gal properties mediated through the production of lytic

enzymes, toxic proteins, toxic fatty acids and ethyl

acetate, and have potential for the biocontrol of fungi.

Commercial preparations of some species are now avail-

able for the pre- and post-harvest control of fruit, veg-

etable and grain spoilage fungi [36,37].

Yeasts and food safetyAs part of daily life, humans consume large populations of

yeasts without adverse impact on their health. Unlike

bacteria and viruses, yeasts are rarely associated with

outbreaks of foodborne gastroenteritis, intoxications or

other infections. Nevertheless, caution is needed, and

further research on this topic is required [38�].

Significant ‘lay’ literature connects the dietary intake of

yeasts with a range of gastrointestinal, respiratory, skin,

migraine and even psychiatric disorders. Overgrowth of

yeasts in the gastrointestinal tract might contribute to the

development of these disorders, but immune reactions to

yeast cell wall polysaccharides and responses to yeast-

produced amines and sulfur dioxide could also occur. The

connection between yeast, the human response and food

is largely based on dietary observations. If foods sus-

pected to contain yeasts or their products are removed

from the diet, the adverse responses disappear, but return

when such foods are reintroduced [38�,39].



Yeasts are not aggressive, infectious organisms, but some

species such as Candida albicans and Cryptococcus neoformansare opportunistic pathogens that cause a range of muco-

cutaneous, cutaneous, respiratory, central nervous system

and organ infections, as well as general fungemia [40].

Individuals with weakened health and immune systems

are at greatest risk, and include cancer, AIDS and hospi-

talized patients, and those undergoing treatment with

immunosuppressive drugs, broad spectrum antibiotics

and radio- chemotherapies. The greater frequency of such

individuals in the community has led to increased reporting

of yeast infections. Moreover, an increasing number of

yeast species has been implicated, including many found in

foods (e.g. S. cerevisiae, C. krusei, C. famata, P. anomola,Rhodotorula spp. [38�,41]. Infections caused by S. cerevisiaeare notable because of its extensive use in the food indus-

try, and infections with this yeast have been reported in

immunocompetent individuals [42��,43]. It is thought that

hospitalized patients become exposed to high levels of

yeasts through the biofilms they form on catheters and

other invasive devices, and that these yeasts probably

originate from the hands of hospital workers and the foods

brought into the hospital environment [38�]. More research

is needed to establish stronger linkages between the role of

foods in contributing to yeast infections. Information is

needed on the survival and growth of yeasts throughout the

gastrointestinal system, the potential for yeasts to translo-

cate from the gastrointestinal tract to the blood system, and

the general occurrence of yeasts ‘in the hospital and health

care environments. The circumstances whereby a non-

pathogenic yeast, such as S. cerevisiae, becomes pathogenic

also require investigation.

Probiotic and other health benefitsProbiotics are viable microorganisms that are beneficial to

consumers when ingested in appropriate quantities.

Although certain species of lactic acid bacteria are pro-

minent as probiotic organisms, there is increasing interest

in yeasts as probiotics [38�,44�,45]. S. cerevisiae var bou-lardii has been used for many years as an oral biother-

apeutic agent for treating a range of diarrheal disorders.

This species colonizes the intestinal tract where, in a

probiotic function, it combats diarrhoea-causing bacteria

[44�,46]. Food carrier systems for this yeast need to be

developed for its commercial application as a probiotic,

but technical obstacles have been encountered. When

incorporated into some products, it caused gassy, etha-

nolic spoilage and off-flavours [47,48]. Of greater concern,

are reports of fungemia infections caused by S. boulardii[42��,43]. Other yeasts mentioned as potential probiotics

include D. hansenii, Kluy. marxianus, Y. lipolytica, I. orien-talis, P. farinosa and P. anomala, but further research is

required [38�]. Yeasts are increasingly used as probiotics

in the livestock and aquaculture industries [38�].

Yeast products, principally derived from S. cerevisiae, have

been used for many years as ingredients and additives in


food processing. These products include flavourants,

enzymes, antioxidants, vitamins, colourants and polysac-

charides [49,50]. Three points are worthy of mention.

First, many of these products are prepared from yeast

cells after they have been processed by autolysis. Despite

its commercial significance, molecular understanding of

yeast autolysis is still very limited and more research is

needed to optimize this process [51,52]. Second, most

products are derived from S. cerevisiae. The yield and

range of products could be increased by screening for

their presence in other yeast species and strains, as

demonstrated for the vitamin folic acid [53], cell wall

polysaccharides [54] and autolysates [55]. Finally, there

remains undiscovered bioactivity and functionality in

yeast products. Whereas the glucan polysaccharides from

the walls of S. cerevisiae were originally valued for their

water-binding and rheological functionalities, it is now

recognized that they can stimulate the immune system,

lower serum cholesterol, exhibit antitumour activity, and

adsorb substances such as mycotoxins [38�,49].

ConclusionsAdvances in molecular technologies have provided new

analytical tools for studying the diversity and biological

activities of yeasts associated with food and beverage

production, although more research is still required on

the ecology and activities of yeasts in products other than

beer, bread and wine. The interactions between yeasts and

the ecosystems in which they occur provide another area

for future study; yeasts form interactions with other species

and strains, along with bacteria, other fungi, protozoans and

their viruses, but as yet these relationships remain poorly

described and understood. Interest in the public health

significance of yeasts in foods and beverages is also increas-

ing, in both positive and negative contexts. Again, we are

likely to see future developments in this regard.

UpdateDebaryomyces hansenii is one of the most significant yeasts in

food and beverage production, and this is highlighted in a

recent review of its phylogeny, ecology, physiology, mol-

ecular biology and its biotechnological potential [56]. As

mentioned in the conclusion, yeast interactions between

themselves and with other organisms have implications for

food quality and safety, and further research is needed on

these topics. Aspects of yeast cell interactions have been

considered in a recent review that discusses their under-

lying molecular mechanisms, how they impact on growth

and survival and how they affect pathogenicity [57].

References and recommended readingPapers of particular interest, published within the annual period ofreview, have been highlighted as:

� of special interest�� of outstanding interest

1.��

Boekhout T, Robert V (Eds): Yeasts in Food. Beneficial andDetrimental Aspects. Behr’s Verlag; 2003.


174 Food biotechnology

Comprenhensive discussions of yeasts in foods and beverages — anemphasis is placed on commodities.

2.��

Querol A, Fleet GH (Eds): Yeasts in Food and Beverages. Springer;2006.

Comprehensive discussions of yeasts in foods and beverages – emphasison ecology and biology of yeasts.

3. Blackburn C (Ed): Food Spoilage Microorganisms. CRC Press;2006.

4.�

Beh AL, Fleet GH, Prakitchaiwattana C, Heard GM: Evaluation ofmolecular methods for the analyses of yeasts in foods andbeverages. In Advances in Food Mycology. Edited by HockingAD, Pitt JT, Samson RA, Thrane U. Springer; 2006:69-106.

Reviews and lists recent literature on molecular methods used for theanalysis of yeasts in foods and beverages.

5. Fernandez-Espinar JT, Martorell P, de Llanos R, Querol A:Molecular methods to identify and characterise yeasts infoods and beverages. In Yeasts in Food and Beverages. Editedby Querol A, Fleet GH. Springer; 2006:55-82.

6.�

Kurtzman CP, Fell JW: Yeast systematics and phylogeny –implications of molecular identification methods for studies inecology. In Biodiversity and Ecophysiology of Yeasts. Edited byRosa CA, Peter G. Springer; 2006:11-30.

Outlines the most recent changes to yeast classification and taxonomy,based on DNA sequencing and phylogenetic analyses.

7. Rawsthorne H, Phister T: A real-time PCR assay for theenumeration and detection of Zygosaccharomyces bailii fromwine and fruit juices. Int J Food Microbiol 2006, 112:1-7.

8. Page BT, Kurtzman CP: Rapid identification of Candida speciesand other clinically important yeast species by flow cytometry.Appl Environ Microbiol 2005, 43:4507-4514.

9. Fleet GH: Saccharomyces and related genera. In Food SpoilageMicroorganisms. Edited by Blackbrun C. CRC Press; 2006:306-335.

10. Schuller D, Valero E, Dequin S, Caseal M: Survey of molecularmethods for the typing of wine yeast strains. FEMS MicrobiolLett 2004, 231:19-26.

11. Fleet GH: Yeast interactions and wine flavour. Int J FoodMicrobiol 2003, 86:11-22.

12.�

Romano P, Capece A, Jespersen L: Taxonomic and ecologicaldiversity of food and beverage yeasts. In Yeasts in Food andBeverages. Edited by Querol A, Fleet GH. Springer; 2006:13-53.

Good overview of diversity and roles of yeasts in fermented foods andbeverages.

13.�

Prakitchaiwattana J, Fleet GH, Heard GM: Application andevaluation of denaturing gradient gel electrophoresis toanalyse the yeast ecology of wine grapes. FEMS Yeast Res2004, 4:865-877.

Provides a critical discussion of merits and limitations of the use of DGGEfor analysing yeasts in foods and beverages.

14. Nielsen DS, Hanholt S, Tano-Debrah K, Jespersen L: Yeastpopulations associated with Ghanaian cocoa fermentationanalysed using denaturing gradient gel electrophoresis(DGGE). Yeast 2005, 22:271-284.

15. Cocolin L, Urso R, Rantsiou K, Cantoni C, Comi G: Dynamics andcharacterisation of yeasts during natural fermentation ofItalian sausages. FEMS Yeast Res 2006, 6:692.

16.��

Swiegers JH, Bartowsky EJ, Henschke PA, Pretorius IS: Yeastand bacterial modulation of wine aroma and flavour.Aust J Grape Wine Res 2005, 11:139-173.

Comprehensive, well illustrated review of the biochemical production offlavour and aroma compounds by microorganisms in foods and beverages.

17.�

Bond U, Blomerg A: Principles and applications of genomicsand proteomics in the analysis of industrial yeast strains. InYeasts in Food and Beverages. Edited by Querol A, Fleet GH.Springer; 2006:173-213.

Good, basic introduction to yeast genomics and its applications in foodand beverage fermentations.

18. Varela C, Cardenas J, Melo F, Agosin E: Quantitative analysis ofwine yeast gene expression profiles under winemakingconditions. Yeast 2005, 22:369-383.


19. Brejning J, Arneborg N, Jespersen L: Identification ofgenes and proteins induced during the lag and earlyexponential phase of lager brewing yeasts.J Appl Microbiol 2005, 98:261.

20.�

Tanghe A, Prior B, Thevelein JM: Yeast responses to stress.In Biodiversity and Ecophysiology of Yeasts. Edited by Rosa CA,Peter G. Springer; 2006:175-195.

Good, general review of the biology and practical significance of thestress responses in yeasts.

21. Addis E, Fleet GH, Cox JMC, Kolak D, Leung T: The growth,properties and interactions of yeasts and bacteria associatedwith the maturation of Camembert and blue-veined cheeses.Int J Food Microbiol 2001, 69:25-36.

22. Samelis J, Sofos JN: Yeasts in meat and meat products. InYeasts in Food — Beneficial and Detrimental Aspects. Edited byBoekhout T, Robert V. Behr’s Verlag; 2003:239-265.

23. De Vuyst LD, Neysens P: The sourdough microflora:biodiversity and metabolic interactions. Trends Food SciTechnol 2005, 16:43-56.

24. Schwan R, Wheals AE: Mixed microbial fermentationsof chocolate and coffee. In Yeasts in Food — Beneficialand Deterimental Aspects. Edited by Boekhout T,Robert V. Behr’s-Verlag; 2003:429-449.

25. Ardhana M, Fleet GH: The microbial ecology of cocoabean fermentations in Indonesia. Int J Food Microbiol 2003,86:87-99.

26. Masoud W, Cesar LB, Jespersen L, Jakobsen M: Yeasts involvedin fermentation of Coffee arabica in East Africa, determined bygenotyping and by direct denaturing gradient gelelectrophoresis (DGGE). Yeast 2004, 21:549-556.

27. Aidoo KE, Nout MJR, Sarkar PK: Occurrence and function ofyeasts in Asian indigenous fermented foods. FEMS Yeast Res2006, 6:30-39.

28.�

Nout MJR: Traditional fermented products from Africa,Latin Amercia and Asia. In Yeasts in Food — Beneficialand Detrimental Aspects. Edited by Boekhout T,Robert V. Behr’s-Verlag; 2003:451-473.

Demonstrates the diversity and significance of yeasts in many productslittle known to western consumers.

29. Stratford M: Food and beverage spoilage yeasts. In Yeasts inFood and Beverages. Edited by Querol A, Fleet GH. Springer;2006:335-380.

30. Viljoen B: Yeast ecological interactions. Yeast-yeast, yeast-bacteria, yeast-fungi interactions and yeasts as biocontrolagents. In Yeasts in Food and Beverages. Edited by Querol A,Fleet GH. Springer; 2006:83-110.

31. Alexandre H, Costello PJ, Remize F, Guzzo J, Guilloux-Benatier M:Saccharomyces cerevisiae – Oenococcus oeni interactions inwine: current knowledge and perspectives. Int J Food Micorbiol2004, 93:141-154.

32.�

Hogan DA: Quorum sensing: alcohols in a social situation.Curr Biol 2006, 16:R457-R458.

Novel discussion of the concept of quorum sensing and its mechanismsin yeast biology.

33.�

Arneborg N, Siegumfeldt H, Andersen GH, Nissen P, Daria VR,Rodrigo PJ, Gluckstad J: Interactive optical trapping shows thatconfinement is a determinant of growth in a mixed yeastculture. FEMS Microbiol Lett 2005, 245:155-159.

Novel use of laser optical technology to demonstrate that spatialphenomena might affect yeast cell–cell interactions.

34. Howell K, Cozzolino D, Bartowsky E, Fleet GH, Henschke PA:Metabolic profiling as a tool for revealing Saccharomycesinteractions during wine making. FEMS Yeast Res 2006,9:91-101.

35. Hansen TK, van der Tempel T, Cantor MD, Jakobsen M:Saccharomyces cerevesiae as a starter culture in mycelia.Int J Food Microbiol 2001, 69:101-111.

36. Fleet GH: Yeasts in fruit and fruit products. In Yeasts in Food —Beneficial and Detrimental Aspects. Edited by Boekhout T,Robert V. Behr’s-Verlag; 2003:267-287.



37. Passoth V, Fredlund E, Druvefors UA, Schnurer J: Biotechnology,physiology and genetics of the yeast Pichia anomala.FEMS Yeast Res 2006, 6:3-13.

38.�

Fleet GH, Balia R: The public health and probiotic signficanceof yeasts in foods and beverages. In Yeasts in Food andBeverages. Edited by Querol A, Fleet GH. Springer; 2006:381-398.

First major review of positive and negative public health issues relating toyeasts in foods and beverages.

39. Eaton TK: Moulds, yeasts, ascospores, basidiospores,algae and lichens: toxic and allergic reactions.J Nutrit Environ Med 2004, 14:187-201.

40. Hazen KC, Howell SA: Candida, Cryptococcus and other yeastsof medical importance. In Manual of Clinical Microbiology 8th

edition. Edited by Murray PR. American Society for Microbiology;2003:1693-1711.

41. Hobson RP: The global epidemiology of invasive Candidainfections – is the tide turning? J Hosp Infect 2003,55:159-168.

42.��

Enache-Angoulvant A, Hennequin C: Invasive Saccharomycesinfections: a comprehensive review. Clin Inf Dis 2005,41:1559-1568.

A thorough review and discussion of human infections caused by S.cerevisiae — an industrial yeast not normally considered to be a risk tohuman health.

43. de Llanos R, Querol A, Peman J, Gobernado M,Fernandez-Espinar MT: Food and probiotic strains from theSaccharomyces cerevisiae species as a possible origin ofhuman systemic infections. Int J Food Microbiol 2006,110:286-290.

44.�

van der Aa Kuhle A, Skovgaard K, Jespersen L: In vitro screeningof probiotic properties of Saccharomyces cerevisae varboulardii and foodborne Saccharomyces cerevisiae strains.Int J Food Microbiol 2005, 101:29-40.

Provides a good discussion of issues related to the use of yeasts asprobiotic organisms.

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47. Lourens-Hattingh A, Viljoen BC: Growth and survival of probioticyeast in dairy products. Food Res Int 2001, 34:791-796.

48. Heenan CN, Adams MC, Hosken RW, Fleet GH: Survival andsensory acceptability of probiotic microorganisms in anon-fermented frozen, vegetarian dessert. Lebensm WissTechnol 2004, 37:461-466.

49. Dawson KA: Not just bread or beer: new applicationsfor yeast and yeast products in human health andnutrition. In Nutritional Biotechnology in the Feed and FoodIndustry. Edited by Lyons TP, Jaques FA. Nottingham UniversityPress; 2002:225-232.

50. Abbas CA: Production of antioxidants, aromas, colours,flavours and vitamins by yeasts. In Yeasts in Food andBeverages. Edited by Querol A, Fleet GH. Springer; 2006:285-334.

51. Zhao J, Fleet GH: Degradation of RNA during the autolysis ofSaccharomyces cerevisiae produces predominantlyribonucleotides. J Ind Microbiol Biotechnol 2005, 32:415-423.

52. Alexandre H, Guilloux-Benatier M: Yeast autolysis in sparklingwine – a review. Aust J Grape Wine Res 2006, 12:119-217.

53. Hjortmo S, Patring J, Jastrebova J, Andlid T: Inherent biodiversityof folate content and composition in yeasts. Trends Food SciTechnol 2005, 16:311-316.

54. Nguyen TH, Fleet GH, Rogers PL: Composition of the cell wall ofseveral yeast species. Appl Microbiol Biotechnol 1998,50:206-212.

55. Lukondeh T, Ashbolt NJ, Rogers PL: Evaluation ofKluyveromyces marxianus as a source of yeast autolysates.J Ind Microbiol Biotechnol 2003, 30:52-56.

56. Breuer U, Harms H: Debaryomyces hansenii — anextremophilic yeast with biotechnological potential.Yeast 2006, 23:415-437.

57. Palkova Z, Vachova L: Life within a community: benefit to yeastlong term survival. FEMS Microbiol Rev 2006, 30:806-824.


yeasts in foods and beverages: impact on product quality and safety

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