When was yeast first used in bread baking

The yeast floated to the top of the beer and was skimmed off and put into stone bottles. Bakers cold-buy their yeast from a local brewery or make a.

The basis for most of these ferments was a mash of grain, flour or boiled potatoes. Hops were often included to prevent sourness. Salt-rising bread was made from a starter of milk, cornmeal and, sometimes, potatoes.

The term ''salt-rising'' referred to the practice of nesting the bowl of starter in a bed of heated salt to keep it warm overnight. A little salt also was added to the starter to delay the bacteria growth that might sour the milk. For frontier families, sourdough was the most important possession after the Bible. Not only was it used to make bread, flapjacks and biscuits, but it could be used to fill cracks in the log cabin, treat wounds, brew hooch and feed the dogs.

Areas that require attention include functional differences between MAL loci, the effect of copy number variation on fermentation dynamics, and strain optimization to allow co-metabolism of glucose and maltose. Better understanding of these characteristics could lead to shorter fermentation times, and increased bread volume for industrial producers. Saccharomyces cerevisiae experiences extreme osmotic shock during dough fermentation and commercial yeast processing Aslankoohi et al.

In the face of hyperosmotic conditions, cells lose water due to the osmotic gradient formed between both sides of the cell membrane, and growth is halted Hohmann et al. This can result in decreased viability and decreased fermentation capacity, which manifests in longer proofing times and smaller loaves. Thus, managing osmotic stress is a fundamental property of strains used in bread baking.

Saccharomyces cerevisiae responds to osmotic stress through strong upregulation of AQR1 , a membrane transporter for amino acid excretion during restrictive growth conditions Aslankoohi et al.

Glycerol prevents water loss by balancing intracellular osmolarity so it more resembles the environment Sasano et al. Glycerol homeostasis is managed through the high-osmolarity glycerol HOG pathway, a mitogen-activated protein kinase MAPK pathway central in stress-activated response and signaling Hohmann, ; Brewster and Gustin, Individual genes within the HOG pathway exhibit different evolutionary rates between or within lineages of fungi, with osmosensory genes upstream of HOG1 evolving more rapidly Nikolaou et al.

For example, the osmosensing transmembrane receptors MBS2 and SLN1 have high nucleotide diversity, and a branch-site model test to detect selection acting on two Chinese rice wine strain branches is suggestive of adaptation to osmotic stress caused by high sugar in rice wine Li et al.

In contrast, there is some evidence that osmotic adaptation to high sugar dough is not a defining feature of bakery strains, and instead, osmotolerance is variable across both commercial baking strains and non-bakery strains Bell et al. Whether the bakery strains that can ferment in high sugar dough do so as a result of selection on osmo-receptors has not yet been examined.

How fast strains can respond to osmotic stress, and whether the response is maintained or not, may impact dough fermentation dynamics. One study found that baking strains of another yeast, Torulaspora delbrueckii , responded faster to osmotic stress, with a faster increase in glycerol levels, out performing two commercial S.

The T. This may represent another trait that could be further optimized in S. Genes involved in glycerol homeostasis are some of the most differentially upregulated genes during the onset of dough fermentation and are essential for yeast growth in dough Aslankoohi et al.

GPD1 , the first enzyme in the synthesis pathway of glycerol, is key in glycerol content and successful dough fermentation Albertyn et al. GPD1 has thus been a target for genetic manipulation to modulate glycerol accumulation.

Deletion of GPD1 results in decreased glycerol concentration, reduced CO 2 production, and delays in dough fermentation Aslankoohi et al. Overexpression of GPD1 , on the other hand, can increase fermentation rates in high-sugar dough and improve dough gas retention, although improvements are more stark for laboratory strain backgrounds than bakery strain backgrounds Barrett et al.

This is suggestive that some baking strains are indeed better adapted to dough conditions, and produce dough with better gas retention, due to higher base levels of glycerol amongst other selected traits. The glycerol proton symporter STL1 is also significantly upregulated upon the start of dough fermentation. STL1 is part of a glycerol uptake system that imports glycerol from the environment to increase internal glycerol concentrations Ferreira et al.

Stl1 functions together with the glycerol export protein Fps1 to control intracellular glycerol content and modulate glycerol leakage into the dough Oliveira et al. Some glycerol leakage is beneficial, as it softens and relaxes the dough, increasing its ability to contain CO 2 and thus increasing overall dough rise Aslankoohi et al.

However, excessive glycerol in dough can have a negative effect on bread aroma and taste Olsson and Nielsen, Glycerol levels also affect the shelf-life of finished loaves Barrett et al. In addition to osmotic stress, baking yeast are subject to a variety of other stressors, particularly related to industrial manufacturing and distribution processes. For example, frozen dough is used to provide easier access to fresh-baked bread for consumers while balancing labor conditions for bakers and allowing for greater geographic distribution of products Hsu et al.

Typical baking strains fail to retain leavening ability following freezing, and thus cryotolerant strains have been isolated from natural environments, or developed through genetic modifications in the lab Hino et al. Much of the attention in freeze tolerant baking strains has focused on the naturally occurring cryoprotectants trehalose and proline, which protect cells from a variety of stresses including osmotic stress, freezing, dehydration, and heat shock Shima et al.

Trehalose and proline accumulation allow commercial baking yeast to survive processing and distribution either in dehydrated, dry yeast or frozen in pre-made dough Sasano et al. We address current knowledge of trehalose and proline accumulation in dough in turn, below. Trehalose is a sugar composed of two glucose molecules linked at their 1-carbons.

The cellular concentration of trehalose is balanced by the relative rates of its synthesis and degradation. High levels of trehalose are strongly correlated with high levels of stress tolerance Attfield, , however, the trehalose content in commercial baking strains varies considerably Lewis et al. Deletion of one or both NTH1 and ATH1 increases trehalose concentrations and gassing power of frozen doughs, with the NTH1 deletion providing the most freeze protection.

This has made NTH1 a common target for creation of freeze-tolerant baking strains Shima et al. The amino acid proline functions in stress response across many organisms Csonka and Hanson, ; Delauney and Verma, Proline stabilizes proteins and membranes, lowers the T m of DNA, and scavenges reactive oxygen species ROS , which is believed to be a main killer of yeast in osmotic, drying, and freezing stress Samuel et al.

However, proline is not naturally elevated in response to these stressors in S. Nevertheless, researchers have demonstrated that synthetically increasing S. Other efforts have shown that different alleles of the genes MPR1 and MPR2 , which detoxify the toxic proline analog azetidinecarboxylate, also are involved in proline accumulation and mitigating desiccation stress and cryotolerance Nomura and Takagi, ; Sasano et al. Intriguingly, efforts to simultaneously increase levels of both trehalose and proline have yielded higher tolerance to oxidative and freezing stresses and improved the fermentation ability in dough after being frozen compared with the singular accumulation of proline or trehalose Sasano et al.

This work suggests that proline and trehalose protect yeast cells from short-term and long-term freezing effects, respectively, and is an interesting area for further pursuit which could be beneficial to the frozen dough industry. The sensory qualities of bread, such as aroma and taste, are essential metrics of quality for consumers, and are strongly influenced by volatiles and secondary metabolites produced by yeast Schieberle and Grosch, ; Frasse et al.

Variation in aromas may relate to the adaptive diversification of yeast strains and species in as much aroma compounds play important physiological and ecological roles in yeasts, including regulation of growth, communication, and signaling to insect vectors Richard et al.

The attraction of insect vectors has been shown to mediate important yeast life history traits including outcrossing and dispersal Reuter et al. As a result, non-human animals may be important in engendering the diversity and abundance of aromas produced among yeast strains.

Recent studies support the hypothesis that domestication of S. Different sourdough and commercially available baking strains of S.

The more influential aroma compounds include alcohols, aldehydes, ketones e. Typically, ethyl acetate has an aroma similar to pineapple, diacetyl and acetoin are buttery, alcohols and aldehydes provide floral and sometimes fruit notes, and esters, particularly saturated esters, are fruity in nature Fingolfn Practically Science, Combined, these molecules provide the aromatic qualities of each loaf, and can be quantified and analyzed to detect variation across strains.

One such study assessed aromas produced by seven different S. While not all compounds had such ranges, the variety of aroma concentration would provide each bread with a unique aroma profile, or lack thereof Aslankoohi et al. This is compounded by the fact that different compounds have different odor detection thresholds ODT , or the concentration at which the human nose can detect it in water. Indeed, one strain was found to have significantly less of almost all aroma compounds tested, meaning the bread would have less distinct scent compared to bread prepared with one of the other commercial baking yeasts, as it would only have aromas from the flour and maillard reaction from the baking process.

Improving flavor and aroma in baked products is an active area of research, and includes a variety of techniques including experimental evolution, gene modifications and exploiting natural diversity Dzialo et al. Current commercial baking strains are not optimized for all desired baking and processing traits, as industry often uses strains due to historical reasons Steensels et al.

Some common categories where additional optimization is needed include: increased fermentation capacity in sweet doughs, resistance to salt toxicity, better storage survival frozen and dried , enhanced sensory qualities such as taste, aroma, and texture, synthesis of beneficial and functional metabolites such as antioxidants, phenols, xanthophyll, and anthocyanins, and microbial stability Becker et al. Past and current efforts to meet these demands are summarized here through efforts to exploit natural diversity bioprospecting and genetic modification of existing strains bioengineering.

Bioprospecting generally describes the search for new strains or species with beneficial characteristics that could be leveraged in industry. Bioprospecting of S. Potential sources for baking strain bioprospecting can be generally divided into wild and man-made environments. Insects represent another promising potential source for yeast bioprospecting in natural environments, with insect-isolated yeasts already proving to be viable options in bioethanol production, beer, and other industrial uses Urbina et al.

This could be especially relevant for the baking industry, as wild-yeast fermented breads like sourdough, injera, Indian flatbreads, and Chinese steamed bread are teeming with microbial diversity Zhang et al.

The S. Sampling from worldwide wild-yeast fermented breads, with a focus to increase representation from Africa, Asia, and South America, should be a priority for finding desirable baking strains in the future. Bioprospecting and bioengineering should not be considered mutually exclusive, but generally, bioengineering takes a more direct method in creating strains with beneficial phenotypes.

Here, we will also use this term to encompass traditional breeding techniques. Somewhat surprisingly, selective breeding has not been heavily employed for industrial yeast strain improvement, despite the genetic and phenotypic variation present see reviews Steensels et al.

Certainly there are challenges to traditional crosses, industrial S. Large scale screening for desirable traits in bread baking also presents practical challenges, like the ability to phenotype many individual crosses for fermentative traits and aroma compounds.

Despite these obstacles, the genetic mapping of complex traits in S. There have been a few efforts to cross in useful traits for production of beer Nikulin et al. New genetic editing techniques that allow for the successful completion of meiosis in normally sterile hybrids Bozdag et al. Finally, genetic modifications through gene deletions, allele replacements, and the insertion of new genetic materials have been successfully used to create baking strains with better fermentation dynamics and stress tolerance.

We have highlighted many studies in this review that have utilized genetic modifications to better understand how individual genes or pathways contribute to desirable and undesirable traits in bread baking. However, moving these modified strains from research labs to the bakery presents major hurdles. Industrial use of genetically engineered organisms in food is illegal or highly regulated in most countries Steensels et al.

In this regard, other common techniques like mutagenesis and directed laboratory evolution may hold more applicable potential. These methods have been applied to wine Bellon et al. A future that exploits natural variation through bioprospecting, traditional crosses, and directed laboratory evolution may help meet both consumer and baker preferences.

There are clear desires of bakers and consumers for more flavorful, nutritious breads, and bakers need strains that show increased osmotolerance, cryotolerance, and desiccation resistance without the loss of fermentation capacity. In this review, we have outlined the genetic and phenotypic diversity of S.

We note that many researchers have documented variation in traits important for baking, including maltose utilization, trehalose content, glycerol content, aroma compounds, freeze tolerance, osmotolerance, and fermentation metrics like total CO 2.

Most of these studies have only used a small handful of strains, which suggests we have only surveyed a portion of the phenotypic variation that may exist. With many more isolates being collected from home, artisanal, and commercial bakers, there is an opportunity to better understand the evolutionary history of baking strain domestication and molecular evolution and selection on gene variants; map genetic loci contributing to complex traits; and develop better baking strains.

We conclude with the following outstanding questions that can serve as a guide for future research. Why are interspecies hybrids repeatedly found in beer and wine, but not bread?

What is the genetic diversity and biogeography of S. Are there molecular signatures of selection in baking strains? Do signatures of domestication differ between fermented breads from different cultures? CL and CSH were responsible for the writing and editing of this manuscript. RD and AM were responsible for the editing of this manuscript. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Aguilera, J. Albertyn, J. GPD1, which encodes glycerolphosphate dehydrogenase, is essential for growth under osmotic stress in Saccharomyces cerevisiae, and its expression is regulated by the high-osmolarity glycerol response pathway.

Alizadeh, P. Purification and biochemical characterization of the ATH1 gene product, vacuolar acid trehalase, from Saccharomyces cerevisiae. FEBS Lett. Arranz-Otaegui, A. Archaeobotanical evidence reveals the origins of bread 14, years ago in northeastern Jordan. Aslankoohi, E. PLoS One. Baking Ancient Egyption Bread Baking Ancient Egyption Bread. Google Scholar. Attfield, P. Aviles, G. Faced with flour and yeast shortages, bakers get creative.

Baik, M. Cereal Chem. Baker, E. Evolution of a novel chimeric maltotriose transporter in Saccharomyces eubayanus from parent proteins unable to perform this function. PLoS Genet. Barnett, J. A history of research on yeasts 2: Louis Pasteur and his contemporaries, — Yeast 16, — Barnhart, R. Wilson Company , Barrett, A. Becher, P. Yeast, not fruit volatiles mediate Drosophila melanogaster attraction, oviposition and development.

Becker, J. Bekatorou, A. Production of Food Grade Yeasts. Food Technol. Bell, P. Comparison of fermentative capacities of industrial baking and wild-type yeasts of the species Saccharomyces cerevisiae in different sugar media.

Bell, W. Characterization of the kDa subunit of yeast trehalosephosphate synthase and cloning of its gene reveal its identity with the product of CIF1, a regulator of carbon catabolite inactivation. Bellon, J. Newly generated interspecific wine yeast hybrids introduce flavour and aroma diversity to wines.

Benjaphokee, S. Highly efficient bioethanol production by a Saccharomyces cerevisiae strain with multiple stress tolerance to high temperature, acid and ethanol. Bigey, F.

They are reharvested after the fermentation process, resulting in continuous genetic selection according to the indoor brewing environment. The different strains of beer yeast can determine the flavor of, for instance, a lager versus an ale. Wine yeasts, on the other hand, spend most of the time outside in and around vineyards, resulting in more hybridization with wild yeasts.

Please consider downloading the latest version of Internet Explorer to experience this site as intended. Attention, at-home bakers: Three surprising things you might not know about yeast February 18, Understanding the biology behind S. Another highly-recommended brand came from Hull. Today yeasts are produced and exported all over the world.

They are reliable and of high strength, work fast and can be bought dried or compressed. It all started in an Egyptian culture over years ago Finally, here's a thought: one gram of yeast contains 20,,, twenty billion single-celled living micro-organisms. Not Panicking Ltd is not responsible for the content of external internet sites. It has been compiled and recompiled many times and under many different editorships.

It contains contributions from countless numbers of travellers and researchers. Write an entry Read more. The History of Bread Yeast Content from the guide to life, the universe and everything.

Ancient Egypt We don't know when or how the first leavened bread occurred 1 ; only that the first records of any sort of bread are in ancient Egyptian hieroglyphs. The Development of Science in Europe The exact nature of yeast - where it comes from and what it is - remained a mystery for millennia. Strange Tales In England in the - 9 Brewers Book of Norwich , the name for barm was goddisgoode because it was made by the blessing of God. The Commercial Production of Yeast Yeast became more standardised when distillation of baking yeast was first developed in the midth Century.

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Oct 21,