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Bread A Biotech Processes


Biotechnology is rapidly making valuable contribution to well being of our daily life . Bread has emerged as  one of the most common, widely accepted food material world over,  because of its balanced nature of nutrients,ease of mass scale manufacturing technology, convenience ,and freely available main raw material the wheat flour.

In a good sandwich bread a customers look for softness, attractive golden brown crust, snow white crumb, good mould free shelf life , large volume, more number of slices in a standard pack,  all at a very attractive price.

A bread manufacturer has to take in to consideration all requirements of the customer in addition he has to keep costs under control and also makes profits on invest made and accumulate money for future expansion.

Do you know the contribution of biotechnology in making high quality of your daily bread?

While wheat flour, water, salt, sugar accounts for more than ninety five percent of  bread mass, remaining three to four percent ingredients are  the  key ingredients that convert these humble daily used food ingredients in to appetizing  bread. Many of these quantitatively  minor ingredients  play major role in bread making and are produced by bio-tech processes.

These ingredients include bakers yeast, enzymes, certain chemicals like ascorbic acid and vinegar, starter cultures also known as sour dough starters. Let us learn about them in more detail.

Bakers yeast– It is the key ingredient and acts as leavening/ fermenting agent responsible for gassing effect in wheat flour dough and plays important role in volume, taste and  desired fine honeycomb like structure of bread crumb. Technical name of bakers yeast is  Saccharomyces cerevisiae, it is the single largest and most commonly used biotechnology product world over.  Selected strains of Saccharomyces cerevisiae are propagated in yeast factories under controlled conditions and distributed to bread manufacturing establishments in various forms depending on local conditions and scale of operation of these units. The most frequently used form of bakers yeast in India is compressed yeast. Commercially yeast is available in form of pump able slurry ( cream yeast),or a long shelf life dry product like active dry yeast, instant yeast etc. Commercial compressed yeast has around billion live yeast cells  per gram of commercial product ,each cell capable of functioning like a mini autonomous unit,.

When yeast is mixed with  bread flour,water,salt and variable quantity of sugar  along with other ingredients like bread improvers in a mixer for short duration a homogeneous lump of these ingredients is forms which is called bread dough. During dough making process the sugars from wheat flour and sucrose added as ingredient rapidly goes in  to solution and thus become available for yeast to start its function. Enzymes present in yeast cells attack, glucose,fructose,maltose,sucrose present in its environment and start producing carbon dioxide slowly, during the same time the gluten present in wheat flour absorbs moisture and due to mixing effect become elastic with en trapped starch particles forming a complex matrix. The gas produced by yeast gets entrapped in this elastic matrix and slowly bread dough starts growing in volume and structure of dough becomes spongy in due course of time. The yeast cells work as catalyst and are capable of producing carbon di oxide from sugars for long time if sugar supplies are uninterrupted. Damaged starches produced in wheat milling process  are vulnerable to attack by amylotic enzymes which hydrolyze starches to simple sugars. But normal bread flour is unable to supply enough of simple sugars for continuous gas production by yeast unless assisted by suitable enzymes. We will discuss about these enzymes in detail in further narration.

When bread recipes have high sugar content, high osmotic pressure exerts negative effect on yeast activity. Bulk production and wide distribution of bread in modern times demands incorporation of preservatives in bread recipe.These preservatives have common antibacterial,anti fungal activity. This ingredients also affect  normal activity of yeast. These commercial problems are overcome by yeast manufacturers by following certain process  innovation while propagating yeast it self, making yeast more osmo tolerant and tolerant to action of preservatives. Thus yeast plays major role in bread making process.

The dosage of yeast is in the range of 2-4% on flour weight / basis, higher dosage is mainly  used in sweet dough breads with sugar content in the range of 20-28 %

Enzymes- Enzymes are basically proteins that have catalytic properties and even in very small dosage ( parts per million, or in simple terms milligrams per kg.)  play important role in industrial bread making process.

Grain based enzymes– Wheat when harvested under normal climatic condition has very limited enzymes ,these enzymes are called cereal amylase’s and are provided by nature to start new life cycle of wheat plant when wheat seed is sown in soil.. The bakers used wheat or barley malt in commercial process for long years to improve their bread quality. Wheat or barley is cleaned soaked in water to hydrate grains which in tern are stored under clean, controlled temperature conditions to allow sprouting to take place, the controlled sprouted grain’s are dried and made in to flour, these flours have rich contains of beta amylase’s. In breads with very low sugars  recipes these flours were used to boost yeast activity and to get attractive golden brown color to bread loves.,  Commercial malting is a bio-tech process now more commonly used in beer raw material manufacture than in bread. These enzymes in malt remain active even at relatively high temperatures and pose problem in commercial bread making process and so when used in breads ,they  need very good control on dosage and dough processing. In recent years with easy availability of  a range of microbial enzymes  used of malt in bread making has reduced significantly.

Microbial enzymes– The enzymes suitable for baking industry come mainly from two classes of microbes fungi and bacteria. Fungal enzymes are more popular, due to attractive side enzyme activity it offers  apart from main enzyme. All these enzymes are product of  now well established biotech  industry. Let us see various classes of enzymes that are useful in bread making process.

Alpha amylase’s- Mainly produced from fungal strains are the first and still the most extensively used enzymes in bread manufacturing industry. These enzymes in very low dosage on flour weight basis attack damaged starch particles that have hydrated during dough making process and generate mixture of maltose and glucose in the dough permitting un interpreted  substrate for gas production by yeast, a step that  is essential for raising of bread. The peculiarity of fungal enzymes is they get inactivated by heat at around 60 0C, which is achieved in early stages of bread baking in the oven, permitting easy means of controlling enzymatic activity On the other hand bacterial enzymes are more heat stable and are not used for same purpose, but  are some times  found useful in very low dosage to get property of keeping bread soft for longer time.

Hemicellulase/ Xylenases Wheat flour contain non cellulose no-starch polysaccharide commonly referred to as hemicelluloses and pentosans are part of hemicelluloses. They are soluble and non soluble depending up on the polymerization, having main chain of D-xylose with side chain of arabinose. The pentosans are frequently conjugated with important wheat protein gluten. The use of hemicellulose enzymes results in hydrolysis of large part of insoluble pentosans.These resulting smaller chain polymers become soluble fractions having gelling properties, that helps to absorb more water,reduce dough stiffness, these enzymes also improve gas retention of dough by removing pentosans that are cross linked to gluten proteins and help to form better network of gluten which in terms improves CO2 retention capacity of dough,the over all results is improved bread volumes,good oven spring,better machine-ability of dough( operational advantage), crumb softness.

Amyloglucosidase -This enzyme attacks damage starch chains and cleave off glucose molecules which is directly used by yeast for gas production

Lipases- Commercially special lypases with dual action on polar lipids naturally present in wheat flour, when added to dough are able to hydrolyze both phospholipids (0.4-.0.6%)in to lyso phospolipids and galactlipids in to galactomonoglycerides. These two modified lipid fractions of wheat flour act like commonly used fat based emulsifiers such as DATEM and SSL, that help in conditioning of dough,helping increase in loaf volume,softer crumb and improve related bread characteristics.

Glucose oxidase- A reinforcement  or strengthening of wheat dough and an improvement of bread quality can be obtained with addition of glucose oxidase, the enzyme modifies gluten proteins ( gliadins and glutenins) through the formation of disulfide and non di sulfide cross-link resulting in to strengthening of gluten structure which in terms improves gas retention in dough. Potassium bromate a chemical that has been banned in bread making process recently can be replaced by using glucose oxidase in combination with  other enzymes.

Asperginase- During recent years potentially carcinogenic substance called acrylamide is focus of attention.At high temperature of bread baking( 220+/- 5 0C) reaction of amino acid aspargine with sugars like glucose takes place resulting in to formation of this compound. Use of enzyme asperginase converts aspargin to aspartic acid thus reducing  90 % formation of harmful acrylamide in breads being baked.

Cellulases- High fibre breads are becoming popular and Ray breads also fall in same class cellulase has been found useful in improving dough properties . High fiber  like bran in whole wheat flour, or Ray flour face difficulties while processing as these fractions reduces gluten matrix  strength  , the non starch polysaccharide like cellulose, hemicellulose,beta glucan,mannans,gluco and galactomannans form complex with proteins and ferulic acid , cellulse with side activity of hemicellulase is found useful to improve gas retention properties of such dough.

Bio-tech based chemicals

Ascorbic acid  Is a product derived from combination of bioteh process and chemical synthesis and is the most extensively used aaddtive in bread process . A common cyclical acid is most common cyclical reduction- oxidation agent used as improver in bread dough. In the manufacturing process one step of converting sorbitol to sorbose is carried out using bacterium acetobacter Suboxidans, in fact research is in advance stages to make process in lesser steps using bio-tech systems. Ascorbic acid is efficient as it changes/ moves the alpha amylase thermal optimum of activity towards lower temperature and inactivate enzyme at the starch converting temperature,reducing the accumulation of dextrins during bread baking. In presence of oxygen including dough development stage, ascorbic acid reduces the _SH groups, during first minutes of kneading, these groups are oxidised to SS- disulphide linkages. This leads to the improvement of the dough resistance and elasticity of bread dough resulting in better bread.

Vinegar-Acetic acid- Vinegar is produced  in two steps first conversion of sugars to ethanol followed by oxidation to acetic acid. Traditionally vinegar’s were produced from sweet fruit juices and were used in bread process to arrest bacterial spoilage.  Large quantity of ethanol produced by distilleries using molasses as feed stock for fermentation is frequently converted to acetic acid by chemical process. Chemically produced acetic acid has replaced vinegar in bread to a great extent due to cost consideration.

Sour dough starters- Sour dough starter are commercial preparations containing selected specially adopted strains of Lactobacillus and acid tolerant bakers yeast grown under controlled condition in free flowing flour batter.It is of particular importance in baking ray based breads where yeast alone cannot give satisfactory results.. In comparison with only yeast raised breads sough-er dough based products have distinctively tangy or sour taste, due mainly to the lactic acid produced by lactobacilli. The actual inocolum, known as “ starter” or Le vain is essentially an ancestral form of preferment,used by old time bakers when high quality yeast in desired quantity was rarely available. A sourdough starter is a stable symbiotic culture of bacteria and yeast present in a mixture of flour and water. The traditional sour dough are rich in Saccharomyces exiguusor Candida milleri symbiotically with Lactobacillus sanfranciscensis. Breads made with sour dough starters give a denser finished product, better shelf life without external additive and has typical aromatic acidic taste.Such breads are popular in some countries in Europe and in part of USA.

Commercial starters are not available in India but world over they are available in tetra-pack delivered through cold chains.

Note – Most of the enzymes and ingredients mentioned in the above article are permitted for use in bread in India by FSSAI ( Food safety and standards authority of India), please refer local legal requirement in other countries.

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