BREAD PROCESSING

  BREAD PROCESSING 

INTRODUCTION

Bread is a combination of flour and water that has been baked. Over the years, its production has become increasingly more complex with a multitude of additions ranging from fruit to nuts, and many different kinds of flours. Bread is a staple food in many countries, with cultural significance. With common sayings such as “the bread winner,” it has become one of the most important parts of the world’s diet.

Traditionally, the term “bread processing” was used by high-speed bakers to assess the contribution of moulding or makeup stages of dough to the manufacture of bread.

Today, it’s a broader term describing the overall manufacturing process of breads and buns. It consists of a series of steps including mixing, fermentation, makeup, proofing, baking, cooling, slicing and packaging. Due to their critical role, these processes must be carefully operated to meet pre-set conditions and specifications.¹

THE PRODUCTION PROCESS OF BREAD

The process of making bread has five steps:

1.     Mixing – This is the combination of all of the ingredients, typically wheat flour, water, leavening, salt, and fat. The dough is allowed to mix until it is one product.

2.     Shaping – This is when artisan bakers, or machines, shape the dough into the desired shape and size.

3.     Proofing – Proofing allows the it to rise and develop the desired crumb structure.

4.     Scoring – Before baking, it must be cut so that the shape is not distorted as the bread expands in the oven

5.     Baking – Baking is the actual cooking of the bread. It is done in many types of ovens and varies greatly depending on type.

6.     The following block diagram shows the production steps in bread processing using different dough systems.

There are many types of breads including fruit, quick, rye, and any other addition a baker deems necessary. Typically, bread is 60-75% water by weight, depending on the desired consistency. Bread also usually has fat added at a level of 3% in order to soften the texture, and support the development of gluten. Lastly, salt is added to almost all formulas in order to enhance flavor and strengthen the development of gluten yielding a higher quality product for consumers.

Bread is used in many ways throughout the world and has varying nutritional values. Typically, it is a low protein and fat food that is high in carbohydrates. Whole grain breads have many natural vitamins and minerals in them, though most white breads are fortified with similar minerals. By law, calcium, iron, thiamin, and niacin are added to all brown and white flours in the United States. Many countries make some types using wheat and additions of their own native starchy plants, giving different flavors and nutritional values.

The style and type of bread dictates the dough system to use as well as the processing conditions during mixing, makeup and baking. A baker would not like to produce ciabatta with a close crumb structure, or to produce a loaf of white pan bread with an open crumb structure and texture like a ciabatta.

All steps in bread processing are important for a successful operation, but most bakers would agree that the three truly vital process steps are mixing, fermentation and baking. They are commonly described as the heart and cornerstone of bread making operation and can also determine the finished product characteristics, both internally and externally.

Mixing: The objective is the blending and hydration of dry ingredients, air incorporation and gluten development for optimum dough handling properties. Variables to monitor and control include mixing time, energy input, dough temperature:

• Mixing time: a function of flour strength, its protein, damaged starch and non-starch polysaccharides and bran particles content. Other factors include mixer speed, mixing arm design, dough size in relation to mixer capacity, adequacy of refrigeration system (dough temperature) and delayed sugar/fat/salt addition.
• Mixing equipment: vertical (planetary), spiral (open and closed for vacuum mixing), horizontal, continuous (open and closed).
• Process specifications: 9–15 minutes at high speed in horizontal mixers. Final dough temperature should be 76–82°F (25–28°C).²

Fermentation: The objective is yeast growth, production of CO₂, ethanol and organic acids, development of flavors and aromas, and modification of dough handling properties. Variables to monitor and control include fermentation time, temperature, titratable acidity (TTA), pH, microbial count:

• Fermentation time: controlled by the temperature of dough, sponge, starter or pre-ferment, hydration level (free water), pH, osmotic pressure, yeast food (amino acids, minerals, fermentable sugars) and yeast level (or lactic acid bacteria count).
• Fermentation equipment: troughs in fermentation room, closed tanks, open tanks, benches.
• Process specifications: 1–20 hours (at room conditions), depending on dough system used. The temperature in fermentation rooms is typically set between 75–85°F (24–29°C) with a relative humidity (RH) of 60–80%.

Makeup: Makeup stage mainly encompasses four operations:

1.     Dividing

2.     Rounding

3.     Intermediate proofing

4.     Sheeting and moulding

The divider cuts bulk dough into single pieces of proper weight (with as little stress exerted on dough as possible) so that these can be rounded and rested prior to taking their final shape. The divider must process the entire dough load quickly to prevent excessive gassing that creates scaling errors.

The sheeter and moulder encompass the sheeting stage, curling chain, pressure board, and guide bars. These influence the gas bubble structure, shape and length of the dough piece to place in the pan. The moulder should be adjusted to achieve the desired shape with a minimum amount of pressure and stress on the dough to avoid damaging cell structure obtained during mixing and fermentation.

Baking: The objective is to convert raw dough into bread, set structure of product, crust and crumb formation, kill-step and shelf-life extension. Variables to monitor and control include temperature, time (governed in continuous ovens by conveying speed). Other relevant variables include heat flux (burners), humidity (dampers) and air velocity or flow.

• Baking time: controlled by oven temperature, conveying speed, initial (proofed dough) and final product temperature, heating pattern, bake loss, product load and formulation.
• Baking equipment: direct-fired oven, indirect-fired oven, electric oven, rack oven, reel oven, conveyorized, tunnel, hybrid and impingement oven.
• Process specifications: 10–20 minutes at 400–420°F (204–216°C) (heating pattern in different ovens must be equivalent for comparable results).

 

MACHINES / PLANTS USED IN BAKING BREAD

1.     Dough mixer: Dough mixer is a kind of food machine. Main function of it is to mix flour, water and other materials evenly. There are vacuum dough mixer and spiral dough mixer. This machine mainly consists of mixing tub, hook, driving device, control panel and machine seat.

2.      Dough divider machine: Dough divider machine can divide the dough into specified dough block evenly. Block and weigh the dough according to the requirements of specification. It is one of necessary combination models to realize the automation of bread forming production line. It is crucial to realize automatic feeding and processing, also can help save labor force.

3.      Dough pressing machine: Dough pressing machine is a kind of automatic dough kneading machine that takes place of traditional manual dough kneading way. By compressing with counter rotating rollers the dough was kneaded with plasticity and extensibility in a certain thickness. It can achieve continuous dough pressing, and improve extensibility and smoothness of the dough by s-shaped continuous folding and pressing. It is equipped with automatic dusting system, and output dough thickness of pressing rollers is adjustable.

4.      Dough Trimming Machine: Dough Trimming Machine is a kind of combination machine which connects the dough pressing machine and forming machine. The main function of the Dough Trimming Machine is dividing and thimming the pressed dough and conveyor it to the forming machine. Main function of it is automatic segmentation and dough belt shaping.

5.      Bread Forming Machine Mainframe: Through the extension of two pressing rollers and sheeting devices to make the dough more glossy and make dough quality more stable. Finally, through a mainframe pressing roller, the dough will fall on the mainframe conveyor belt, and the dough will be rolled into strips by the bread roller device and auxiliary wheel. The Bread Forming Machine Mainframe can be equipped with filling machine and shutter cutter machine to produce a variety of characteristics and shapes of bread.

6.      Blade Cutting Machine: If you want to produce cut block products you can add cutting equipment. The cutting length can be adjusted by the machine, and the cutting blade can also be replaced for different shapes of bread.

7.      Automatic Tray-arranging Machine: Usually for food enterprises requiring scaled production, they prefer automatic tray arranging of food with machinery. You could choose or set different arranging or alignment ways according to quantity, diameter, arranging way of food product and other parameters, and the food products can be aligned onto the baking pans automatically and accurately.

In the process of bread production, there are many items to be noted, each items can affect the quality of bread, from the raw and auxiliary materials processing to the final bread forming, so it is very important to choose proper production machinery & equipment, and do a good job of production process control.

MAJOR CONSTRAIN IN THE PRODUCTION OF BREAD

• Inadequate gluten in flour.
• Misappropriate quantities and inferior quality of raw material.
• Poor diastatic activity of flour.
• Improper time and temperature of fermentation, proofing and baking.
• Wrong methods of manipulation of dough i.e. knocking-back, cutting and moulding.
• Inadequate cooling of bread.

 

 

REFERENCES

1.     Zhou, W. Bakery Products Science and Technology, 2nd edition, John Wiley & Sons, Ltd, 2014, pp. 475–507.

2.     Cauvain, S.P. Technology of Bread making, 3rd edition, Springer International Publishing Switzerland, 2015, pp. 147–212.