MR. Pramod B. Thatte
SAF YEAST Co., Mumbai
3000 years before our times Egyptians and Babylonians knew how to make and use sour dough to make leaven bread and wines. The era of “mysterious fermentation” lasted very long till 1860 when famous French scientist Louis Pasture identified yeast as the microorganism responsible for alcoholic fermentation. Up to 18th century yeast for bread making was obtained from beer making process either bottom deposited yeast or top floating yeast was collected and used. In 1780 Dutch distillers put in market first baker yeast specially designed for bread. The process was passed on from Holland to Germany and in 1825 foundation of first baker yeast factory was established at Lucke. The yeast manufacturer Tebbenhof made the first compressed yeast using filter press around 1867. In 1872 Max DE Springer from Vienna founded in France first grain based yeast factory at Lille. With rapid advancement in scientific knowledge and technological development in 1883 Emile Hansen from Carlsberg laboratory introduced pure culture technique that improved further the quality of yeast. In 1892 continuous separation machines (separators) were brought in service in Berlin. Till all these years a blend of malt, barley and root stock(beet) was used for yeast cultivation. Research from 1900 to 1935 helped to develop replacement of old substrate by molasses supported by addition of other salts to supply nitrogen and phosphorus made process easy and less expensive. The real modern yeast manufacturing using continuous addition of nutrient and use of allied equipment like separators, filter-press that improved washing of yeast and separation from wort was established in Germany in 1915 and in Denmark in 1919.
My purpose of briefly reviewing the history of yeast making was essential as modern yeast production process is one of the most successful biotech industry and is still based on these principles and has advanced in to a hi-tech industry with progress in our engineering capabilities, like efficient cooling system, efficient oxygen transfer designs of fermenters, cleaning in place systems, efficient pump designs. Hygienic designing of large vessels has helped in scaling up of operations in economical way in addition better understanding chemistry of raw material, and yeast biology has tremendously helped us in making rapid advancement in yeast production.
Modern Yeast industry
It is single largest commercially produced microorganism in terms of quantity ( metric tons) in the world .
World production figure more than three million tons in 2012.
Indian story of yeast industry started with a small unit at Uran near Mumbai way back in 1974-75 by Shaw Wallace Group Co. Called Indian Yeast Co. It is no more in operation. Presently India produces around 85-90,000 tons of yeast per year at five factories directly or indirectly own by two groups. and market demand is partly met by imports mainly from China, Turkey and some other countries.
The major groups engaged in production of yeast and yeast based derivatives in the world are
- Associated British foods Plc( UK),
- Alletech Inc( Canada),
- Angle yeast co( china),
- Cher Hansen A/s( Denmark),
- Lallemand Inc( Canada),
- Lesaffre group( France),
- Oriental yeast( Japan)
- Royal DSM( Holland),
- Liber GMBH( Germany)
Commercial yeast — Presentation
Every gram of commercial live yeast has millions of live cells, and each cell acts as power house of activity. One gram of compressed bakers yeast has 2 x 1010 CFU/gm.
Available as cream yeast This product has 18-20 % dry matter and used extensively in Europe, America where large automated bakery plants are operated, consuming several tons of wheat flour per shift. Cream yeast is easy to handle, can be stored, chilled and transferred using pumps saves on packing material, labour costs and ease of use in automated systems. Bio-ethanol plants also consume large quantity of yeast in cream form as they are highly automated. Yeast cream requires storage in chilled condition good hygienic storage system and has shelf life of about 5-7 days.
Compressed yeast The product has 28-33% dry matter. Available in form of 25gm/500gm/1000gm cakes resembling bricks in shape are most suitable for home baking, small and medium size bakeries. Product can be stored in refrigerator for 10-15 days without significant loss of activity
Crumbled yeast mass This yeast is sometimes also demanded by bulk users yeast cake in uneven or extruded in form of fine particles is packed in 20-25 kg bags and supplied , It is easy to weigh accurately and suitable for machine feed operations. The product has characteristics similar to compressed yeast in terms of activity and shelf life
Active dry yeast This product was developed to overcome problem of refrigerated storage and relatively short shelf life of compressed yeast The product is in form of medium to fine globules/ granules having 92-95% dry matter. Normally it is used in remote areas where fresh yeast is not available and refrigeration facility is absent. This production process involves carefully drying extruded yeast cell mass under controlled condition in roller drum dryers or fluidized bed driers , Process of drying over longer period results in some loss of activity, but the main advantage is 3-4 months of shelf life at ambient temperature ,no need of refrigeration. The product is normally paced in tins of various sizes or in poly jars of 12-15 kg.Product is suitable for bakeries using long duration fermentation process of bread making in remote areas.
Instant dry yeast It is a dry yeast with very high dry matter ( 96-97%) is produced in form of fine vermicelli dried at low temperature under controlled conditions and packed under vacuum. The activity of yeast is very good, and like fresh compressed yeast start its function in dough almost immediately and so called “ Instant Yeast “ The fine vermicelli gets dispersed easily in the dough and so acts fast on dough. It has long shelf life and can be safely store at ambient temperature for up to two years. This product has replaced large market of active dry yeast.
Depending on type of substrate on which it has to function three main categories of yeast are available in all above formats.
(i) Lean dough yeast for no sugar or low sugar ( up to 5%) dough mainly products like sandwich breads, pizza bases, French bread etc.
(ii) The other variety is yeast for high to very high sugar dough where sugar in bread preparation is as high as 30 -35 %.
In North India it is lean dough yeast while in east and south India it is sweet dough yeast. The yeast produced for sweet dough yeast is having very high osmo-tolerance.
(iii) Yeast for distillery purpose is quite different from these two as it has high osmo-tolerance, high alcohol tolerance, and better adopted to function a relatively higher temperature.
Testing of yeast products
Yeast products (containing live yeast) suitable for baking and distillery industry are not described in food codex and thus do not have fixed standards. In Food Safety and Standards Authority of India ( FSSAI), at present there are no standards for bakers, distillers, wine yeast. ISI has established a standard for baker’s yeast but ISI marking of yeast products is not compulsory. There are no standards prescribed in developed countries or in EU countries either. Here it is the customer that sets up standard and decides if quality is right or not.
Chemical and Microbiological testing
Though there are no official standards for yeast based products all products based on live yeast are thoroughly tested for certain common chemical parameters like moisture content, protein content, ash content, and for microbiological quality especially for total bacterial count and wild yeast count( any yeast other than strain inoculated is treated as wild yeast) lower levels of these contaminant indicate good hygienic manufacturing practices. Though baking temperature normally kills almost all the organisms including yeast ,bakers yeast in various forms is also tested for and absence of pathogenic organisms like Salmonella, E.coli, Fecal coliform, Staphylococcus aureus, Listeria species etc. As once grown and separated from medium yeast is not subjected to any heat treatment, neither it has got any preservatives like other food products. Presence of above mentioned pathogens indicates post harvest contamination from handlers or rodents and if present may risk life of bakery staff who handles yeast. Here I must mention that bakers yeast, wine yeast or distillers yeast are not sterile products. From two angles one is all of them contain millions of yeast cells that is the product itself and secondly though yeast is produced under very hygienic condition, the production conditions cannot be described as sterile and some bacteria especially lactic acid tolerant one and some yeast also grow in the fermenter to some extent and they account for other microbial flora in yeast.
Testing Functional capacity/ fermenting capacity
The main function of baker’s yeast in bread dough is production of carbon dioxide using glucose and maltose normally present in bread wheat flour, and sugars added to bread recipe as an ingredient. There are several methods of testing gassing power of yeast ,this is the most important test in deciding quality and market acceptability of product. The quantity of gas produced on standardized wheat flour dough within fix time interval is the most important test and batches after batches of commercial yeast should always produce minimum fixed amount of gas during fixed interval of time under standard conditions. This ensures that in bakeries bread production period for batch after batch is maintained more or less constant.
For distillers yeast the rate at which it ferments the substrate weather it is diluted molasses, grain hydrolysates, or fruit juices, and extent to which it can accumulate and tolerate alcohol in fermented wort is critical, with minimum of residual sugars left in the wort in shortest period of time and this is tested in lab
Application/utilization of Yeast
Production of baked goods- largest and most well known world wide application
Alcoholic fermentation’s– Mainly for production of ethanol from beet and cane molasses and cane/ beet juice, using grain hydrolysates especially corn, millet’s,wheat,and rice, tubers like potato,cassava,sweet potato ,and latest substrate being cellulose.
Wine industry,- Making wine from grapes, and several other fruits like apples etc and finally many a times distilled out to make specialized branded products.
Prepared foods- Yeast hydrolysates, Yeast extracts rich in nucleotides are extensively used as natural flavoring substances replacing mono-sodium Glutamate and those flavors originating from meat and animal proteins
Food supplements,- Yeast is rich source of proteins,B group vitamin’s , and fiber and finds wide application as rich nutrient supplement in form of inactivated flaked yeast. In fact during last century yeast tablets was popular recommendation for those needing vitamins supplements when pure form of vitamin preparations were not avalible.
Animal feed- yeast has shown excellent probiotic action. Feeding of selected strains of yeast have shown improved productivity in ruminants ( dairy cattle cows,buffalo’s, sheep) with increased milk yield and improvement in fat content of milk, better weight gain in animals raised exclusively for meat production purpose, In poultry it has shown beneficial effect both in broilers and layer birds. In case of broilers it helps better food conversion ( weight gain) and reduced use of antibiotics for protection. In case of layers in addition improved health and better egg production is observed. This is one of the major innovative application of yeast that has been well established in last thirty years or so. Yeast cell wall is rich in beta glucan which stimulates non specific immunity in animals and so yeast cell wall extract rich in beta-glucan is being used in feed and nutrient supplement to bust non specific immunity.
Pharma and bio-pharma Industry Yeast extract is a reach source of balanced nutrient and is extensively used as safe ingredient in media for cultivation of various microorganisms and tissue culture work importance of yeast extract increased many folds with mad cow disease scare.
In very recent years beta-glucan rich products are being marketed as part of cosmetics and in anti-aging skin preparations
Production of enzyme Invertase, glutathione , enzymatic conversion process for production of epihydrine and sudo-epihydrine
In recent times yeast isolated from Antarctica continent are being extensively explored for production of wide range of extra cellular alph amylase,lipase, xylenase, protease etc. Being able to operate at relatively low temperature is a very attractive commercial application in wide range of industries.
Other major yeast based products are yeast extract,yeast autolysate, yeast beta glucan, food supplement vitamin enriched yeast, yeast with high Selenium and chromium enrichment, in cosmetic.
For production of molecules of commercial interest e.g is in synthesis of Artemisinim- a precursor for Malaria drug.
Yeast base cancer fighting technology is in advance stage( Apolife), vaccine production ( rabies), Insulin production.
Yeast is prime target for research in similar applications as it has several advantages over other similar hosts like E. coli, CHOCELLS, Pichia yeast, due to easy secretion/separation of recombinant proteins of interest.
Proven safety for thousands of years, multipal applications, relative ease of propagation, and abundance in nature has attracted attention of yeast as a group of microorganism of choice to play with.
Bakers yeast “Saccharomyces cervisiae” is a power full research tool because of its ability to quickly map a phenotype producing gene to a part of yeast genome. In 1986 international group of scientist from 92 laboratories from countries such as UK, USA, Canada, Japan, France have successfully done gene mapping of this yeast species. The bakers yeast has 6000 genes across 16 chromosomes. Opening new opportunities to study and exploit the commercial potential of this microorganism
Challenges in front of yeast Industry
Unlike many other industries the yeast industry has so far not experienced negative growth rates and industry is expected to be five billion US dollar industry by 2016. There is increasing demand for yeast and yeast based products from all over the world. The potential for expansion in India is very large with countries own demand and export potential from neighboring countries. As one of the largest cane sugar producer country, India has sufficient supply of cane molasses which is the main raw material for yeast industry. But capital cost of setting up yeast manufacturing plant is very high as practically all equipment is made in high grade stainless steel, power requirement is also very high as large volume of liquids are handle using high power pumps auto-matted control systems, separation and packing systems. Raw molasses is produced only in three months during cane crushing season and so needs to be stored, It is a rich source of biotin a essential vitamin for yeast growth, it also contains other B group vitamins, sugars and other assimilable carbon substances, nitrogen sources and very large number of micro-nutrients which are essential for good growth of yeast but The effluent generated with molasses as main raw material is high BOD and COD effluent requiring complex, elaborate and expensive treatment equipment and facilities. Several attempt have been made to produce yeast using other carbon substrates to overcome the problem of high BOD colored effluent generated by cane / beet molasses, as raw material., Starch hydrolysates, glucose, cane sugar, cane and beet juice, and even surplus ethanol has been tried on pilot plant scale and to some extent on commercial scale. All these substrates need supplementing with mineral and vitamins to much larger extent than cane molasses, finished product is almost three times costly and thus un-economical and so up till now they are not raw material of choice for yeast production. During aerobic propagation of yeast the exhaust air has also several compounds that ultimately needs scrubbing prior to discharge of exhaust air. In recent years environmental effect of every industrial activity is being considered for its effect on carbon emission. One kg of compressed yeast is equivalent to 734 gm equivalent of carbon dioxide emission.
Making high quality yeast at low cost to meet continuously changing needs of baking industry, reducing carbon foot print and pollution control are biggest challenge in front of Indian and global yeast industry.
MR. Pramod B. Thatte ( Not Dr.),
Student of CHM college 1973 B.Sc. 1973 passing out batch. He did his M.Sc. from POONA University and joined then K.M.KUNDANINI College of pharmacy Ulhasnagar as teaching staff in 1975.
Left in 1976 to join Bharatiya Agro Industries Foundation at their Foot and Mouth Viral vaccine. He worked on primary cultures of lamb and bovine kidney,chick and duck embryo fibro-blast. Continuous cell lines like BHK-21, PK, MVPK, Vero. And their mass production in roller bottles and suspension culture for virus propagation. He had opportunity to experiment with lab animals like mice, rabbits, hamsters, guinea pigs and calfs. He had under gone advance training at Research center of I.N.R.A (France) during fellowship from Government of France, for more than a year. On returning he was responsible for Production of Brucella cotton strain-19 live vaccine, “Brucella Rose Bengal” diagnostic antigen was first time developed for use in India along with multiple diagnostic antigens for testing of cattle. Initiated and standardized Bulk cultivation of Mycobacterium Bovis to manufacture Tuberculin. Introduced micro-triter kits based complement fixation test for brucellosis, .
He joined SAF YEAST Co. in 1982, then a member of Lesaffre Group France the world’s leader in Yeast products. He has worked in several laboratories in France, Belgium, Denmark, UK. He visited bakeries and distilleries all over in India, Burma, SRI Lanka for market development and problem solving, He has made presentations on yeast at CFTRI MYSORE, American Institute of Baking – Indian affiliate, Regional Development councils, Baking Industry forums, and yeast conferences.
Presently he works as Director Technical with the same company.