Applications of extrusion in encapsulation technology

Presented by SYED AASIF MUJTABA14pft012

Extrusion technology: introduction

• Operation of shaping a dough like material by forcing it through a restriction/die.• Widely used in FPI.• In food extrusion, the food material is

forced to flow under one/more varieties of conditions of mixing, heating & shear through a die designed to form/puff the dry ingredients.• A food extruder is a device used to cook,

form, mix, texturize, shape & restructure the food ingredients.

Types of food extrusion processCold Extrusion Hot Extrusion

• process at room temperature/ slightly elevated temperature.•No thermal energy addition.•Specific shape products (pasta, pastry dough, candy pieces, meat products). •Low pressure extrusion is used to produce,eg. liquorice , fish pastes, surimi and pet foods. •No oxidation takes place. • Good mechanical properties (temp. are below the re-crystallization temp.)

•Above 100*C.•Also called extrusion cooking.•Thermal energy addition.•Widely used to produce a range of products(variety of low density, expanded snack foods and RTE puffed cereals •HTST process (microbial contamination and inactivates enzymes)

Functions of extrudersAgglomeration Degassing

Dehydration Expansion

Gelatinization Grinding

Homogenization Mixing

Pasteurization & sterilization Protein denaturation

Shaping Shearing

Texture alteration Thermal cooking

Unitizing

EncapsulationDefined as a process to entrap active agents within a carrier material (wall material)A useful tool to improve delivery of bioactive molecules and living cells into foodsA technology in which the bioactive components are completely enveloped , covered and protected by a physical barrierA technology of packaging solids liquds or gaseous materials in small capsules that release their contents at controlled rates over Produced particles usually have diameters of a few nm to a few mmEncapsulation technology is now well developed and accepted within the pharmaceutical, chemical, cosmetic, foods and printing industries. In food products, fats and oils, aroma compounds and oleoresins, vitamins, minerals, colorants, and enzymes have been encapsulated

The substance that is encapsulated may be called the core material, the active agent, fill, internal phase, or payload phaseThe substance that is encapsulating may be called the coating, membrane, shell, carrier material, wall material, capsule, external phase, or matrix.

Two main types of encapsulatesThe reservoir type: • has a shell around the active agent. • This type is

also called capsule, single-core, mono-core or core-shell typeThe matrix type • The active agent is much more dispersed over the carrier material; it can be in the form of relatively small droplets or

more homogenously distributed over the encapsulate. • Active agents in the matrix type of encapsulates are in general also present at the

surface (unless they have an additional coating)

The main purposes of encapsulation

stabilize an active ingredient

control its release rate

and convert a liquid formulation into a solid which is easier to handle

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Protective shell specifications

maximal protection against environmental conditions, during processing or storage under various conditions

not to react with the encapsulated material

have good rheological characteristics at high concentration if it is needed

have easy work ability during the encapsulation

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Materials used for encapsulationPolysaccharides

• Starch and their derivates – amylose, amylopectin, dextrins, maltodextrins, polydextrose, syrups and cellulose and their derivatives

Plant extracts

• gum Arabic, galactomannans, pectins and soluble soybean polysaccharides

Marine extracts

• carageenans and alginate

Proteins

• milk and whey proteins are caseins, gelatin and gluten.

Lipids

• fatty acids and fatty alcohols, waxes (beeswax, carnauba wax, candellia wax), glycerides and phospholipids.

Microbial and animal polysaccharides

• dextran, chitosan, xanthan and gellan

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The reasons why to employ an encapsulation technology?

• provide barriers between sensitive bioactive materials and the environment • mask bad tasting or smelling, • stabilize food ingredients or increase their bioavailability • provide improved stability in final products and during processing.• less evaporation and degradation of volatile actives, such as aroma • mask unpleasant feelings during eating, such as bitter taste and astringency of polyphenols • prevent reaction with other components in food products such as oxygen or water • immobilize cells or enzymes in food processing applications, such as fermentation process

and metabolite reduction processes • improve delivery of bioactive molecules (e.g. antioxidants, minerals, vitamins, phytosterols,

lutein, fatty acids, lycopene) and living cells (e.g. probiotics) into foods • modification of physical characteristics of the original material for (a) allow easier handling,

(b) to help separate the components of the mixture that would otherwise react with one another, (c) to provide an adequate concentration and uniform dispersion of an active agent

Extrusion in encapsulation• exclusively for the encapsulation of volatile and unstable flavors in glassy carbohydrate matrices • this process has the very long shelf life imparted to normally oxidation-prone flavor compounds, such as citrus oils, because atmosphere gases diffuse very slowly through the hydrophilic glassy matrix, thus providing an almost impermeable barrier against oxygen. • Carbohydrate matrices in the glassy states have very good barrier properties and extrusion is a convenient process enabling the encapsulation of flavors in such matrices • allows the encapsulation of heat-sensitive material, such as Lactobacillus acidophilus, which cannot be achieved in a typical carbohydrate matrix because of the much higher processing temperatures typically used. • The very low water content in the extruding mass prevents the degradation of the enzyme even at high temperatures for short periods of time

Equipment In the feed zone, a low pressure is generated to homogenize the feeding. In the subsequent zone(s), a gradual increase in pressure is achieved via the screw

design to melt, further homogenize, and compress the extrude. In the final part of the barrel, a constant screw design helps to maintain a continuous

high pressure to ensure a uniform delivery rate of molten material out of the extruder. The barrel is also divided into sections to allow for section-controlled variation in

temperature. Addition of the active ingredient might be in the mixing/dispersing zone of the extruder

at about halfway to minimizes the residence time of the active ingredients At the end of the barrel, a “pre die” and “die head” determine the shape of the final

product (e.g., sheets, ropes or threads). It can be equipped with a chopper/cutter to obtain granular extrudates.

Extrusionadvantages• very long shelf life• Resistance to oxidation• for heat sensitive materials(bacteria & enzymes)

disadvantages• Cost in use• Increase in carbohydrate in food• Large particles (500-1000 μm)• Limited range of shell material

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Flavor encapsulation• Encapsulation of flavors consists in protecting a flavoring agent or a

mixture of molecules with a dedicated envelope. Encapsulation can limit the degradation or loss of flavor during the various product processes and storage. The envelope can also provide functional properties, such as a controlled release of aromatic molecules in a given environment like water (if flavored tea), mouth (solid food: candy, toothpaste

The encapsulation of flavors via twin screw melt extrusion• the remarkable properties of distributive and dispersive mixing of the

twin screw extruder are used to encapsulate flavors continuously.• The matrix powder is first metered into the extruder and then conveyed

and mixed by the screws. By use of viscous dissipation and controlled heating, the powder is melted and transformed into a viscous dough. Aromatics, usually in liquid form, are then accurately introduced into a barrel module during the process: the screw configuration is adjusted to disperse the small droplets of liquid flavors into the molten matrix and distribute them regularly throughout the mass. Temperature and screw shear should be controlled to secure the new homogeneous mixture at a specific and stable viscosity and avoid aggregation of the small droplets

Applications of encapsulated flavors• Extruded encapsulated flavors are used as ingredients in the food industry for

applications such as rapid preparations for desserts, cakes and biscuits, tea bags, loose tea, coffee, instant drinks and confectionery.• The advantages of twin-screw extrusion for encapsulating flavours• Continuous and precise processing with reduced manufacturing costs without

producing effluents• A secured and easily installed compact processing unit• A wide range of flavors and combinations of matrices• Excellent dispersion in the protective matrix• Ability to control the flavors dispersion parameters• Highly-efficient protection, enabling long storage and shelf life  (2 to 3 years

very long shelf life

a few months for unencapsulated citrus oils

1 year for spray dried flavors

5 years for extruded flavor oils

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Fish oil encapsulation

• Fish oil can be encapsulated into a formable mixture by using an extruder with one or more screws in a continuous process .the extrusion process is done at a relatively low temperature (below 30°c)and low pressures (500 – 5,000 K pa) • This can be achieved by using relatively high amounts of plasticizer .

First,emulsions using proteins ,gum or modified matrix (composed of malto-dextrin) by melt extrusion to enhance the storage stability.

Extrusion of probioticsExtrusion is the oldest and most common methods widely used to form microcapsules of hydrocolloid gel matrices due to its ease, simplicity, low cost and gentle condition , ensuring high level of entrapped probiotics.

The mixture of hydrocolloid solution (such as alginate and carrageenan) and the suspension of probiotic cultures is extruded through a syringe needle as droplets into a hardening solution such as calcium chloride.

The size and shape of the beads were influenced by many factors as the needle diameter, distance between needle and hardening solution as well as the surface tension of the hardening solution.

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• This method produced the beads size of 2-5 mm , affecting to sensory characteristics of the applied food products. • Nevertheless, the microencapsulated probiotics were

well protected in the beads against the harmful condition of simulated gastric and intestinal juices as well as in food products

Centrifugal extrusionCentrifugal extrusion is another encapsulated

technique that has been investigated and is currently used by some vitamin manufacturers for the encapsulation of vitamin A.

The device used in this encapsulation technique consists of a concentric feed tube through which coating material and core material are pumped separately to the many nozzles mounted on the other surface of the device. Core material flows through the center of the tube; coating material flows through the other tube.

The entire device is attached to a rotating shaft such that the head rotates around its vertical axis. As the head rotates, the core material and coating material are co-extruded through the concentric orifices of the nozzles as a fluid rod of core sheathed in coating material.

Centrifugal force impels the rod outward, causing it to break into tiny particles. By the action of surface tension, the coating material envelops the core material, thus accomplishing encapsulation. The capsules are collected on a moving bed of fine-grained starch, which cushions their impact and absorbs unwanted coating moisture. Particles produced by this method have diameters ranging from 150 to 2000 µm