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= Enzyme Application in Bakery Industry. (by Tanvi Mathur ;1840629; 5BCZ) =

Enzymes are biochemically proteins that function as catalysts. They bring about chemical changes within biological systems. Hence these enzymes have found a wide variety of commercial application. When the use of enzymes in the bakery industry is discussed, they are utilized to improve dough rheology, crumb softness and gas retention in the manufacture of baked products such as bread, pastries and biscuits.

Primary Constituents of Baked Goods
The typical ingredients in the formulation of baked goods are sugar, eggs, wheat flour, fats emulsifiers, milk, starch and at times even water.

Out of these, wheat flour is one of the most important ingredients and is constituted of starch, gluten, lipids, non-starch polysaccharides and enzymes.


 * Starch is a glucose polymer that is composed of amylose and amylopectin. It is used as a thickener, emulsion stabilizer, water binder, fat substitute and a gelling agent. Therefore, it is used for making baked goods such as bread.


 * Gluten protein is made from monomeric gliadins and polymeric glutenins. Gluten when present in dough provides viscosity, extensibility, elasticity and water absorption capacity to the dough.


 * In dough systems lipids are classified into starch lipids and non-starch lipids based upon their solubility in solvents of different polarities. Lipids are generally use as surfactants and shortening agents in baking.


 * Cereal non-starch polysaccharides are composed of arabinoxylans, β-glucan and arabinogalactan- peptides. Of them, arabinoxylans are form the largest fraction of non-starch polysaccharides in the cell walls of many cereals. Thus, in baking they are important as they give structural integrity to certain baked goods.

Enzyme Application in Bakery Industry
Enzymes are utilized as:


 * Dough Conditioners


 * Fermentation enhancers


 * Anti-Staling agents or crumb softeners.

Dough Conditioners
Enzymes that are used as dough conditioners modify and improve the overall process and quality of dough processing and baked products, respectively. These enzymes are specifically used to replace chemical solutions that were previously used to improve baked good quality.

The following enzymes are used as dough conditioners:

Hydrolases
When considering the bakery industry, hydrolases such as α-amylases are to catalyse the cleavage of starch which contain α-1,4-glycosidic linkage between the amylose and amylopectin chains. The final products of this enzymatic action are oligosaccharides of varying lengths with α-configuration and α-limit dextrins (branched oligosaccharides). These dextrins are further used to make fermentable sugars by enzymes under the category of fermentation enhancers.

It has been observed that when increased levels of reducing sugar is used as the substrate, the products achieved are those as seen in Maillard reaction. These products tend to intensify the crust colour of baked items and improve bread flavour.

These enzymes also improve the gas-retention properties of fermented doughs. They also reduce the dough viscosity during starch gelatinization that improves the volume and softness of the baked item.

Proteases
Proteases may be endopeptidases or exopeptidases. The common proteases that are found in wheat and rye flours are aspartic proteases and carboxypeptidases. These enzymes are found to active in acidic pH and also aspartic protease of wheat are partly linked with gluten.

Proteases are used at a commercial scale in order to reduce the mixing time during dough preparation of bread, crackers and waffles.

However, they ensure that the dough uniformity is not lost. When then are mixed in the blend, they undergo partial hydrolysis, making the dough easy to knead.

Additionally, proteases can affect dough rheology. They do so by regulating the gluten network. This they do so by carrying out proteolysis of the peptide bond within gluten. The direct effect of this being that the shrinkage that was seen of dough or paste after moulding and sheeting was significantly reduced and thus the spread ratio of cookies for instance was optimal.

Hemicellulases
Hemicellulases are a group of enzymes that carry out catalytic activity upon hemicelluloses which are a group of polysaccharides that consist of xylan, xylobiose, arabinoxylan and arabinogalactan.

The most important hemicellulase when it comes to the bakery industry is xylanase or endo-1,4-β-xylanase, which catalyses the endohydrolysis of 1,4-β-D-xylosidic linkages in xylan and arabinoxylan.

In baking industry usually those xylanases are used that can remove insoluble arabinoxylans that interfere with the gluten network while at the same time retain the soluble arabinoxylans. The primary effect seen is the increased dough stability and enhanced viscosity of the same. The dough therefore becomes flexible, easy to handle and thus stable.

Additionally, the loaf volume increases, and the crumb becomes softer.

It has also been seen that this enzyme is also used to improve the quality of biscuits, cakes etc.

Lipases
Lipases, also known as triacylglycerol acyl hydrolases, are known to hydrolyse triacylglycerols (TAG) into monoacylglycerols (MAG), diacylglycerols (DAG), glycerol and free fatty acids.

These lipases were introduced in three generations into the bakery industry market. The first-generation lipases were introduced into the market in 1990. This generation enzymes improve dough rheology, strength and stability alongside improving the machinability of the same. These also give a softer crumb. The second-generation lipases act on TAG, phospholipids and diacylglycerols, simultaneously. The result, more polar lipids get produced. These lipids tend to increase the dough volume and its better stability to mechanical stress. Also, the bread crumb structure is better than that of first gen lipases.

The third-generation lipases are the most modern set of lipases and compared to other two, works efficiently in high speed mixing processes. It has a lesser affinity for short chain fatty acids which hence prevents rancid or off-flavour formation in baked products that have been stored for a while. They also increase the gluten network, which increases the wall thickness, loaf volume and crumb structure while reducing the cell density of high fibre white bread.

Transglutaminases
Transglutaminases are utilized to modify food proteins by cross-linking. As a result, a textured product that is baked goods with a good interlaced structure are developed. Additionally, the lysine within the food proteins is protected which is an essential amino acid as per dietary intake.

It is also essential since it forms heat and water-resistant films which improve the elasticity and the water holding capacity of the dough.



Glucose oxidase
Glucose oxidase belong to a class of enzymes called oxidoreductases. This enzyme catalyses the oxidation of glucose to form hydrogen peroxide and gluconic acid. Thus, this enzyme is successful in removing residual glucose and oxygen in food. The result is that the shelf life of the baked goods increases. Thus, it contributes towards anti-microbial properties.

This enzyme tends to increase the disulfide cross-linking and under certain conditions promotes the gelative oxidation of the gluten matrix. This confers good gas retention, high bread volume, fine crumb structure and dough machinability.

Furthermore, glucose oxidase is now being used as an alternative oxidizing agent to chemicals such as potassium bromate that was traditionally used in baking owing to its carcinogenic nature.



Lipoxygenase
Lipoxygenase is an oxidoreductase that is commonly known as linoleate. This enzyme is mainly added to baked items, to improve their final quality. Most commonly they are added to bleach pigments in dough which are basically soya flour. By adding this enzyme, a whiter loaf and crumb is achieved. Also, they improve dough rheology by co-oxidizing the wheat flour proteins of the dough by strengthening the gluten network. This ultimately enhances proofing and baking which thus improves the loaf volume. Thus, these enzymes are used as substitutes to chemical additives.

Fermentation Enhancers
Once the dough has been made the next step is to prove it and thus allow the dough to ferment. These steps can happen simultaneously. Therefore, yeast fermentation is an essential step in the baking process as one of the final products of fermentation is carbon dioxide gas that cause the dough to rise. Yeast fermentation involves the following chronological order of enzymes:

First β-amylase digests starch and dextrins to give dextrins and maltose, respectively. Then the enzyme maltase breaks down the maltose further into glucose molecules that yeast can ferment to produce alcohol and carbon dioxide utilizing zymase.

However, for sugars such as sucrose, they cannot be fermented using maltase. For them, the enzyme invertase acts upon them which digests the sucrose into glucose and fructose. These simple sugars are then acted upon by zymase that convert these simple sugars into alcohol and carbon dioxide.

Anti-Staling Agents or Crumb Softeners
It has been observed that many baked goods after a certain period of time tend to become firm and hard. Often the term “Stale “is used to describe such items.

Enzymes are therefore used as anti-staling agents to increase the longevity of baked items. A direct effect of this is that the crumb of baked goods is no longer hard.

Some of the enzymes use as anti-staling agents are as follows:


 * Maltogenic amylase is a commonly used anti-staling agent. It optimizes the activity of other amylases in the dough mix. By this, the levels of fermentable and reducing sugars increase in the mix which make the crumb softer. Thus, they indirectly contribute to the softening of the crumb . The reason why this enzyme is used is that it is very heat-stable compared to other amylases such as those of fungal origin. Additionally, it deactivates upon baking so that there is activity of this enzymes in biological systems.


 * Laccase is another enzyme that contains copper within its structure. This enzyme catalyses the oxidation of phenolic compounds. It is a key enzyme that is utilized to form a strong arabinoxylan network in the dough concerned. It thus improves the crumb structure and softness and at the same time reduces the stickiness of the dough.

Future trends
As enzymes have replaced chemical additives and have thus taken over the bakery industry, now research is being carried out as to how their activity can be optimized under different temperature and pH ranges.

This is being achieved through protein engineering and by the creation of recombinant proteins from Genetically Modified Organisms (GMOs).

This has helped in studies on psychrophilic enzymes that work optimally under low temperature conditions. Studies show that these enzymes enhance mixing and proofing activity of dough.

Another study shows that recombinant enzymes that have been isolated from GMOs works quite efficiently as an anti-staling on breads at desired low pH.