Extrusion Technology In Food Processing.ppt 396s6p

Extrusion technology in food processing

Points to be covered

 Introduction

 Advantages of extrusion  Principle of extrusion  Classification of extrusion

 Different parts of extruders  Characteristics of extruded product  Factors affecting extrusion cooking  Case study

What is extrusion? Extrusion is a modern (HTST) cooking process in which heat transfer, mass transfer, pressure changes, and shear are combined to produce effects such as  Mixing  Cooking  Sterilization  Texturizing  puffing  Kneading  Shearing  Shaping  Forming It is very import technology in manufacturing of pasta, ready to eat cereals, snacks and pet food.

History of extrusion

Extruded foods

Advantages of extrusion  Adaptability Full-fill the demand of customers for new verities of product.  Product characteristics Variety of products having different shape, color, texture and appearance can be produced.  Energy efficient Low moisture cooking and lees re-drying needed.  Low cost We can save about 19% of raw materials, 14% labor and 44% capital investment.  Less space More compact and less space requirement than any other cooking technique.

Popularity of extrusion cooking  Versatility A wide range of product by changing the ingredients, operating conditions and die.  Cost High productivity at lower cost.  Productivity Continuous operation with high output.  Product quality It is an HSTS method and coked products retain most of the heat sensitive components.  Environment friendly

Produce lesser significant process effluents.

Principle of extrusion cooking

Cont.  Raw materials are allowed into the extruder barrel, the screw(s) then convey the food along with it.  Down the barrel, smaller flights restrict the volume and increase the resistance to movement of material  As it moves further along the barrel, the screw kneads the material into semi-solid, plasticized mass.  Food is heated above 100ºC, the process is known as extrusion cooking or hot extrusion.

 Creation of heat due to shear friction and addition of external heat cause gelatinization of starch.  Finally ed through one or more restricted dies at the discharge end, expands to final shape and cool quickly.

Classification

By Direction • Direct/Indirect • Forward/Backward

By Operating temperature • Hot • Cold

By Equipment • Horizontal • Vertical

Direct & Indirect Extrusion  Direct: The material is placed in a container and driven through the die by the ram.

 Indirect: In this method, the die remains stationary and the container with the billet moves.

Forward & Backward Extrusion  Forward: Feed is forced to flow in the same direction as the ram.

 Backward: Feed is forced to flow in the opposite direction to the ram movement.

Hot extrusion It is at in a high temperature nearly 50-75% of the boiling point of the product to be extruded.

In addition to the usual benefit to the heat processing, extrusion offers the possibility of modifying the functional properties of food ingredients. The extruder is viewed as a continuous chemical reactor processing biopolymers and food mixes at high temperatures (up to 250°C) for relatively short residence times (usually 1-2 min). Pressure can be as 25MPa. .

Cold extrusion In this process, the product is extruded without cooking or distortion of the food. The extruder has a deep-flighted screw, which operates at a low speed in a smooth barrel, to knead and extrude the material with little friction. Used in preparation of hot dog, pasta, pastry dough and some types of confectionary etc.

Pasta Processing

Different parts of extruders  Feed section The portion of the screw which accepts food materials at feed port. It assures sufficient martial moved or conveyed down the screw.  Compression section The portion of the screw between the feed and metering section. Food ingredients are normally heated, worked into continuous dough mass and partially cooked in elevated pressure and temperature.  Metering section A portion near discharge section with shallow flights. The metering section continuously feed the die with Material at constant pressure.

Cont.  Feeder

Provides a uniform delivery of materials which are often sticky and non-free-flowing. It regulates the rate/pressure of the flow.

 Barrel or sleeves The barrel is divided into feeding, kneading section. They are often jacketed to permit circulating of

steam or superheated oil for heating and cold water or air for cooling.  Screw The most important component which conveys the materials.

Cont.

Cont.  Die or nozzle It has two main functions: to give shape and provide resistance. It can be of various design and number of orifices. It increases pressure, residence time and energy input.  Cutting mechanism Must permit obtaining the final product with uniform size

and the product size is determined by the rotation seeped of cutting blades. The mechanism can be vertical or horizontal.

Characteristics of extruded products  Degree of expansion on exit from the extruder The sudden release of pressure when exiting the extruder causes water to flash off and help the product to expand.  Bulk density The density of the final product depends upon the nature of the solid material as well as the amount of the airspace within the product.  Mechanical properties Physical and rheological properties determine the characteristics of the extruded products. These may be characterized by hardness or crispiness or may be expressed as the fundamental parameters as elastic modulus.  Internal moisture The arrangement of the components of the extruded products leads to the physical properties described above. The state of starch, whether partially or completely gelatinized, in the final product strongly influences the physical characteristics.

Cont.  Protein Quality Nature of extruded proteins depends on the extruder operating conditions such as temperature profile. High heat treatment causes denaturation of many proteins, that influence physical characteristics such as viscosity.  Starch Characteristics Properties of starch in an extruded product that influence the quality characteristics such as water solubility index, water absorption index and enzyme susceptibility. All these depend upon the operating parameter of the extruder as well as the quality of the materials used.

Factors affecting extrusion cooking  Rheological properties of the materials used  Process temperature  Process pressure

 Diameter of die apparatus  Shear rate  Moisture content

 Feed rate  Screw speed  Screw design

Case study: Effects of cold extrusion process on thiamine and riboflavin contents of fortified corn extrudates. Objective: To produce fortified corn extrudates by conventional and cold extrusion techniques at different barrel temperatures and feed moisture contents. To study the effects of process variables on thiamine and riboflavin contents by highperformance liquid chromatography(HPLC) as well as expansion index, bulk density, SEM properties of these extrudates produced from fortified corn extrudates.

Materials and Instruments  Corn flour  Methanol (HPLC grade)  Potassium hexacyanoferrate  Water(HPLC grade)  Sodium hydroide  Sodium acetate trihydrate  Sulphuric acid

 Takadiastase enzyme  Twin screw extruder  HPLC

Methods Extrusion process Sample preparation: Corn flour was enriched with Vitamin B using a Vitamin Premix (DSM Nutritional Products Europe Ltd., Switzerland) The premix was diluted with several steps to achieve the reasonable and uniform level of mixing without concentrated pockets of premix.

Extrusion methods applied  Conventional extrusion process: Extruded in twin screw extruder with a 25:1 screw to diameter ratio. The equipped die size is 3mm. Water was injected into the feed system to adjust the moisture content to 20% and 25 %. The temperature variations that are taken are 80,110 and 130°C.

 Cold extrusion process with CO2 gas injection:

Barrel temperature was maintained at 80°C. CO2 was injected to the barrel with 1MPa pressure through a valve.

Experiments Other measurements are  Moisture content

 Expansion index and Bulk density  SEM analysis  Thiamine and riboflavin content

 Chromatographic determination  Analytics method validation

Results: At different temperature and moisture content corn flour extrudates

Results: SEM analysis

Results: expansion index and bulk density Type of extrusion

Convectional extrusion

Cold extrusion

Barrel temperature (°C)

Feed moisture content (%)

Expansion index

Bulk density

80

20

3.87

0.068

80

25

2.52

0.159

110

20

3.52

0.064

110

25

1.86

0.148

130

20

2.46

0.075

130

25

1.86

0.116

80

20

2.12

0.194

80

25

1.87

0.208

Results: Thiamine and Riboflavin content at different temperature and moisture content Type of extrusion

Convectional extrusion

Cold extrusion

Barrel temperature (°C)

Feed moisture content (%)

Thiamine (μg/ml)

Riboflavin (μg/ml)

80

20

11.4

15.2

80

25

13.3

15.3

110

20

8.2

15.0

110

25

12.7

14.7

130

20

6.3

15.1

130

25

10.5

10.2

80

20

12.2

15.7

80

25

13.8

15.7

Conclusions  Cold extrusion process with CO2 gas injection makes it possible to modify the structure of extrudates from fortified corn flour.

 The use of decreased barrel temperatures enables a higher retention of heat labile vitamins and high-temperature transformations to be carried out in the extruder in combination with structure creation other than by steam.  better structure formation could be obtained by carbon dioxide injection as well as the increase in retention of heat sensitive micronutrients like thiamine.

Cold extrusion advantages and disadvantages over hot extrusion Advantages:  Lack of oxidation  Higher strength due to cold working  Closer tolerances  Good surface finish  Good mechanical properties due to severe cold working as long as the temperatures created are below the recrystallization temperatures  Cleaner work environment Disadvantages:  Higher lubrication cost  Higher loads  Limited state complexity  Limited deformation

References  Berna Bilgi Boyaci, Jay-Yoon Han, M. Tugrul Masactiogclu, Sueda Cleik. (2012). Effects on cold extrusion process on Thiamin and riboflavin contents of fortified corn extrudates. Journal of food chemistry, 132:2165-2170.  Frank A. Manthey, Saujanya R. Yalla, Todd J. Dick, and Mohammud badarauddin. (2004). Extrusion properties and cooking quality of sphagetti containing Buckwheat bran flour. Journal of cereal chemistry, 81(2):232-236.  J. Abecasis, R. Abbou, M. Chaurand, M.-H. Morel, P. Vernoux. (1994). Influence of extrusion conditions on Extrusion Speed, Temperature, Pressure in the Extruder and on Pasta quality. Journal of cereal chemistry, 71(3):247-253.  Maud petitot, Joel Abcasis and Valeria Micard. (2009). Structuring of pasta components during processing: impact on starch and protein digestibility and allergenicity. Trend in food science & technology, 20:521532.  Nilofar Athar, Allan Hardcare, Grant Taylor, Suzanna Clark. (2006). Vitamin retention in extruded food products. Journal of food composition and analysis, 19:379-383.  Ranjit Bordoloi, Subha Ganguly. (2014). extrusion technique in food processing and a review on its various technological parameters. Indian Journal of Scientific Research and Technology, 2(1):1-3.

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