Information about biscuits, cookies and crackers

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1. GENERAL DESCRIPTION:

1.1 General Flowsheet of biscuits, cookies and crackers production

Biscuit Production.jpg

Figure 1: Flow sheet diagram of manufacturing, Literature: Caballero, B., Finglas, P., Trugo, L.: Encyclopedia of food science and nutrition


1.2 Description of techniques, methods and equipment


The word ‘biscuit’ means different things to different people. In America, the word describes a chemically leavened (baking powder) bread-type product, the nearest equivalent in New Zealand being a scone. Products known as biscuits here, and in the United Kingdom, are called ‘cookies and crackers’ in the USA.

In France, Switzerland and Italy, a great quantity of simple, plain biscuits are made by large manufacturers. Many varieties are also made by bakers. Biscuits which require more work and a degree of decoration are referred to as ‘Petit Fours Secs’. Others include ‘Tea Fancies’, which if made small would be referred to in France as ‘Les Petits Gateaux Sec’ or in the UK as ‘Fancy Biscuits’.

Biscuits differ from other baked cereal products such as bread and cakes by having a low moisture content. Bread typically has 35 – 45% moisture, cake, 15 – 30%, and biscuits, 1 – 5% moisture. This low moisture content ensures that biscuits are generally free from microbiological spoilage and have a long shelf life if they are protected from absorbing moisture from damp surroundings or atmosphere. Biscuits have relatively high energy density compared with other baked goods.

The main ingredients used for biscuit manufacture are wheat flour, fat and sugar. Water, which is present in flour at about 14% by weight of sample (that is 14% of the flour is water), is also required at the dough mixing stage, along with other ingredients such as sugar syrups, but these are largely removed during the baking process. Water does, however, play an important role in biscuit making.

Classification can also be based on the method of processing
  • Sheeting and cutting (used for making crackers)
  • Rotary molding (used for short doughs which require a not too sticky consistence)
  • Wire cutting (also used for short doughs)
  • Depositing (used for soft doughs)
Crackers made from hard doughs

Crackers are characterized by their low level of fat and sugar. They are often used as a base of a savory topping such as cheese or tomato. They can further be subdivided into those that are fermented, including soda crackers, saltines and cream crackers and those that are chemically leavened like the snack crackers.

Soda crackers

They have their name from the sodium bicarbonate which is added to the dough. Their shortening content is about 8%. Normally they are quite dry and bland.

Saltines

They are a smaller and more dainty type of soda crackers with an increased amount of shortening.

Cream crackers

Despite their name they content no cream. They have just a slightly higher fat content than soda crackers (12-18%). They have a final moisture content of 3-4% which is relatively high for a cracker. Because of the increased fat content the cracker is quite soft and will not crumble.

Snack or savory crackers

They are sprayed with hot oil as they leave the ovens. Also a topping is applied before baking to add flavour. Typical toppings include herb, cheese, salt and/or chicken. The crackes can also be decorated with small seeds such as poppy or sesame. Usually they contain also some sugar which also adds flavour and texture. Normally they are chemically leavened, but they can also be made from fermented doughs.

Sweet and semisweet biscuits made from hard doughs

The dough of this kind of crackers has higher contents of sugar and fat. Unlike cracker doughs it is chemically leavened.

Biscuits or cookies made from short doughs

The vast majority of worldwide consumed biscuits and cookies are made from short doughs. The range of size, shapes, flavours and ingredients is huge, but some consistent requirements exist. The used flour is usually weak and the proportions of fat and sugar can range up to 100 and 200% of flour weight. The two main processes for forming short dough biscuits are rotary molding and wire cutting.

Biscuits and cookies made from soft doughs

Soft doughs are typically rich in fat (65-76% of flour weight) and sugar (35-40%). Weak flour is used and mixing is in a two-stage process. Often rich and expensive ingredients are used in soft doughs such as almonds, coconut flour or cocoa.


The basic steps in manufacturing are
1. Dough mixing

The raw materials are received in bulk and are automatically metered into dough mixers. Small ingredients (eg. salt) are added by hand. The processes are accomplished with three principal types of mixers: vertical spindle mixers, horizontal drum mixers and continuous mixers.

2. Formation

The forming step is specific to each product type. There are three processes used to form cookie and cracker dough:

  • Cutting or stamping
  • Rotary molding
  • Extruding
3. Backing

Baking usually takes places in tunnel ovens. The ovens themselves may be direct or indirect fired, gas or electric and vary in length and band width. The backing time and temperature depend on the nature of the dough.

4. Cooling

After baking biscuits are cooled by conveying them around the plant for a set of time period.Also the Biscuits can be made by 4 methods the melting method eg:Gingerbread, the rubbing in method , where the biscuits are usually rolled out and cut in shapes, the creaming method eg: Choco chip cookies, whisking method eg:Fortune cookies.


1.3 Temperature ranges and other parameters


Bakery Biscuits.png

Table 1: manufacturing-processes in 190-chocolate-and-chocolate-flavoured-coatings, Biscuit Doctor.

1.4 Benchmark data


Bakery Biscuit Energy.png

Table 1: Energy Consumption, Literature: Energy efficiency improvement and cost saving opportunitieas for the bakign industry.Eric Masanet,Peter Therkelsen and Ernst Worrell


2. CHANGES IN PROCESSES:

2.1 Preheating in Baking Oven

2.1.1Changes in Energy Supply for unique Technology
2.1.1.1 Existing Heat/Cool Technology

The oven is preheated with hot water

2.1.1.2Changes in Distribution of the Heat/Cool System

Water is replaced by Air

2.1.1.3 Optimisation of the Heat/Cool System

This preheating can be performed by The Air-cooled heat exchanger which is a device for rejecting heat from a fluid or gas directly to ambient air. When cooling both fluids and gases, there are two sources readily available,with a relatively low cost, to transfer heat to air and water.The obvious advantage of an air cooler is that it does not require water, which means that equipment requiring cooling need not be near a supply of cooling water. In addition, the problems associated with treatment and disposal of water have become more costly with government regulations and environmental concerns. The air-cooled heat exchanger provides a means of transferring the heat from the fluid or gas into ambient air, without environmental concerns, or without great ongoing cost. [Source: Basics of Air cooled Heat Exchangers: Amercool Manufacturing Inc.]


2.2 Mist Fermentation

2.2.1Changes in Energy Supply for unique Technology
2.2.1.1 Existing Heat/Cool Technology

No use of Ultrasonic smokescreen generator

2.2.1.2Changes in Distribution of the Heat/Cool System
2.2.1.3 Optimisation of the Heat/Cool System

Small droplets are created through ultrasound that produces a mist for the fermentation process.This results in improved heat conductivity of the end product without drying out too much.Energy saving during baking (energy saving 17%) Ultrasonic smokescreen generator during fermentation allows a 17% energy saving. Investment costs are between 4000 to 12000 Euros [ Source: Energy-saving mist technology available on industrial scale By Oliver Nieburg]


2.3 Combination of microwaves with halogen lamp heating

2.3.1Changes in Energy Supply for unique Technology
2.3.1.1 Existing Heat/Cool Technology

Coventional Baking Oven

2.3.1.2Changes in Distribution of the Heat/Cool System
2.3.1.3 Optimisation of the Heat/Cool System

The ‘halogen lamp- microwave combination oven combines the browning and crisping of halogen lamp heating with the time saving advantages of microwave heating. This oven is called as Advantium oven and is produced by GE. Halogen lamp microwave combination baking has been used in bread baking and It has reduced the conventional baking time of breads by about 75 per cent ( Keskin et al., 2004) Specific volume and colour values of bread baked in a halogen lamp microwave combination oven were comparable with that of conventionally baked breads but weight loss and firmness values of those breads were higher as seen in the Table. Breads baked in the microwave oven had the highest specific volume. This can be explained by significant internal pressure which might result in a puffing effect and high volume. The increase in halogen lamp power reduced specific volume and increased weight loss, firmness and colour values of breads in halogen lamp microwave, combination baking. [Source: Emerging Technologies for Food Processing By Da-Wen Sun]


2.4 Proofing in Bakeries

2.4.1Changes in Energy Supply for unique Technology
2.4.1.1 Existing Heat/Cool Technology

The temperature of the proofer oven is generally about 40 degrees Celsius with a relative humidity of 70-80 percent. Heat required for this part of bread baking is typically produced using steam from gas fired boilers. This is a high energy consuming and expensive way of heating the proofing oven.Loaves of bread are baked in the main oven at temperatures of 300 to 400 degrees Celsius. Excess oven exhaust gases are released into the atmosphere as wasted heat.

2.4.1.2Changes in Distribution of the Heat/Cool System

Heat pipes are devices which provide effective heat transfer. They operate by evacuating air and replacing it in part with a fluid such as water. When hot exhaust gases from the baking oven come in contact with the pipe containing the liquid, the liquid first boils and then condenses in cooler parts of the pipe, thereby transferring energy as latent heat. The heat extracted is fed directly into the proofer oven, conserving energy while providing air free of contamination.

2.4.1.3 Optimisation of the Heat/Cool System

The temperature range of the baking oven's flue gas ranges from 300 to 350 degrees Celsius. The waste heat available ranges from 70-80kW and the proofing oven requires energy between 20-45kW. With an air velocity for the system of 1.5 metres per second and an heat exchanger effectiveness of around 65 percent, the waste heat recovery system was able to supply all the heat needed by the proofing oven, thus eliminating the need for any natural gas heating.


Baking Proofing.png

Figure 2: Proofing with Heat Exchanger in Bakeries

The heat exchanger was manufactured locally from steel pipes charged with distilled water. The RMIT research team supervised the manufacturing process to ensure that the equipment would withstand the high temperature and corrosive environment of the baking oven's exhaust gases. Based on annual saving of 500GJ per year for one shift, cost of natural gas at $4 per GJ, and boiler efficiency of 70 percent, the pay back period is less than 3.5 years. For a three shift operation, the pay back period is reduced to 1.5 years.


2.5 Vacuum Baking

2.5.1Changes in Energy Supply for unique Technology
2.5.1.1 Existing Heat/Cool Technology

Conventional baking process was performed using an oven at 180, 190,200oC for different times up to 15 min.vacuum baking process was performed using a vacuum oven at 160, 180, 200 oC and at 500 mbar for different times up to 17 min.

2.5.1.2Changes in Distribution of the Heat/Cool System
2.5.1.3 Optimisation of the Heat/Cool System

Vacuum baking allows production of biscuits with very low PC content linked to the lighter colour of the biscuit due to a lower degree of desired Maillard reaction which also results in different sensorial profiles.It is a new technology to produce biscuits with lower acrylamide levels as a result of the effect of lower temperaturesThe principle of vacuum baking was to decrease pressure in the oven,to decrease boiling point of water during baking. Baking under vacuum allowed us to decrease cooking temperature without retarding the drying process, because moisture evaporation was accelerated under vacuum. Reducing atmospheric pressure in the oven by half enables to decrease ,baking temperature by 20oC with approximately same drying rate.

Vacuum baking is expected to have up to 50% energy saving vs conventional oven Low pressure baking concept has been validated. First tests showed that an energy reduction by 50% can be expected meanwhile the moisture lost was reduced by at least 30% and the bread volume was increased by 20% vs reference.[Source:PROMETHEUS]


2.6 Waste Heat recovery from biscuit oven stacks

2.6.1Changes in Energy Supply for unique Technology
2.6.1.1 Existing Heat/Cool Technology
2.6.1.2Changes in Distribution of the Heat/Cool System
2.6.1.3 Optimisation of the Heat/Cool System

Biscuit manufacturing involves high temperatures for baking .Various type of ovens are available for baking bakery products . Heat recovery can be done for biscuit oven which has 5 - 6 zones basically in indirect Oven .As temperatures are very high ( 400-500degc) on feed end these stacks are then joined to a common duct which collects heat from these stacks with help of blower and then these flue gases is passed onto the last zone which requires low temperature . This temperature is as low as 180- 200 deg c can be attained by circulating flue gases collected in common duct from these stacks .This eliminates need of one burner all together at coloring zone or last zone .Fuel is saved by implementing this kind of arrangement . 15 ltrs-20ltrs /hr can be saved.


2.6 System for building heating and domestic water heating with the Waste heat from flue gas, baking steam and refrigeration system (With controller, boiler as a heat reserve

2.6.1Changes in Energy Supply for unique Technology
2.6.1.1 Existing Heat/Cool Technology
Steam Condensor of the series SK for all oven types with separate steam exhauster.
2.6.1.2Changes in Distribution of the Heat/Cool System
2.6.1.3 Optimisation of the Heat/Cool System
NET steam condensers are specially designed for heat recovery from the baking fumes developed. With these devices, the high heat of condensation of Water vapor are recovered in steam condensors.Their performance is higher, the higher the concentration of the water vapor and the lower the temperature of cooling water.However, they are not suitable for flue gas or exhaust air from fume hoods.The heat recovery steam from the baking supplies with NET smoke-condensators generally have a higher heat capacity than the Heat recovery from the exhaust of the oven burner.
The steam condensator of several juxtaposed ovens, in a common steam condenser is used. This is not only

cost-effective than separate steam condensers for each furnace, but leads also in a more uniform heat output, because in practice, the programs of the individual furnaces are shifted in time.For the connection of several ovens with the steam condensers to become three inputs supplied.Because of their extremely low flow resistance of the vapor can upon the opening the slider on the oven to escape freely. With a suitable selection of the correct type the baking result is not affected.

The recovered steam from the baking heat can be very good for heating be used by hot water and floor heating. For storage

this heat is a separate buffer memory or the lower portion of Layers of memory required. NET steam condensers are available in different sizes for different large plates supplied. For different installation situations all types supplied in two versions:

• execution left with inputs on the left side and
• Execution with right inputs on the right side
For furnaces with a lower vapor contents, there are special steam condensators. To this end, in individual cases, the time Course of temperature, vapor content and flow are measured. By the laws of nature-related regulation of the heat capacity is overheating NET steam condensators excluded.Removable lid allows for easy and fast cleaning with water. NET steam condensers have no moving parts. They are made of stainless steel with high nickel content (so-called. V4A steel) and have a long service life.
With this arrangement, the exhaust heat sources, steam and Chiller their temperature level corresponding to different levels of Buffer allocated and thereby optimally utilized.The upper portion of the memory at a higher temperature provides the Building heating system, the entire memory provides the heat for the heating of the Drinking water in a fresh water module. In this way, the heat well used at a lower temperature in the lower region of the memory.For increased demand in heat a boiler to reload the buffer memory is upper area provided.The regulation of the storage charge pump is a good stratification of heat in Storage and saves power for driving the pumps.

Figure 3: System for building heating and domestic water heating with the Waste heat from flue gas, baking steam and refrigeration system

(With controller, boiler as a heat reserve)



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