- Whole or ground spices are unhygienic since they are contaminated with a heavy load of saprophytic and thermophilic bacterial spores, moulds and yeasts (102-107/g). Gamma irradiation serves as an effective means of reducing bacterial load in natural spices.
- A dose of 3 to 10 KGY can reduce the viable cell count to an acceptable level of <104/g and the flavour quality remains unaffected.
Liquid water-soluble emulsion
- The oil or oleoresin can be extracted in glycerol. isopropanol, propylene glycol, etc. Although the extraction is poor, the shelf-life of the emulsion is generally better.
- Solubilised spices are prepared by mixing them with a polysorbate ester (Tween 80) or by emulsifying them with plant gums.
Encapsulated flavours
- One way by which the loss of volatiles can be obviated is to encapsulate the flavouring components by using an impermeable shell, which locks in the aromatics and thereby considerably increases their shelf-life.
- Encapsulation is essentially a method of providing a 'wall' material around the 'core' flavour, thus protecting the flavour from deterioration/oxidation. In this technique liquid droplets/particles are trapped in a continuous film of a polymer-celled wall material.
- The selection of the wall material is governed by its final end use.
- There are several methods of encapsulation like spray drying, molten extrusion, molecular inclusion, gelatin coating, spray cooling, etc.
- Encapsulated flavours are particularly useful in dry mixes and convenience foods.
Spray drying
- This is the most widely used method for the encapsulation of flavours.
- The method involves two unit operations, viz., emulsification of the spice flavour with an aqueous solution of plant gum/modified starch and dehydration in a suitable drying chamber.
- The 'core' flavour is homogenised with gum/starch solution and the emulsion is pumped in controlled amounts to the spray dryer's centrifugal atomiser.
- The dried particles are carried away in the stream of air and separated in a cyclone collecting chamber.
- There are several processing parameters which decide the product quality.
- These are viscosity of the emulsion, flavour load, degree of homogenisation, in-feed temperature, in-feed flow rate, operating variables of the spray dryer, etc.
Molten extrusion
- Otherwise known as Sunkist fixation method, this was originally employed for the encapsulation of citrus flavours.
- Extrusion as applied to flavour encapsulation means that a flavour emulsion is forced through a die.
- A mixture of glycerol and corn syrup solids is heated to a molten state and cooled to a semiplastic mass when the essential oil is added and emulsified.
- The hot emulsion is extruded into a cold solvent when the filaments or standards harden.
- These filaments are impact-broken, separated from the solvent, dried under vacuum conditions and suitably packed after the incorporation of an anti-caking agent.
Molecular encapsulation
- The encapsulation occurs on a molecular basis with beta-cyclodextrin.
- The reaction between beta-cyclodextrin and a suitable guest molecule takes place in a solution.
- Unlike spray drying, molecular inclusion techniques have the disadvantage that some of the chemical constituents cannot be encapsulated.
- The use of beta-cyclodextrin is approved of by some countries like Japan, Hungary and the Netherlands.
Spray cooling
- A variant of the spray-drying process is known as 'spray cooling'.
- The product is prepared by blending an essential oil/oleoresin with a fatty carrier (hydrogenated fat).
- It is formulated for use in products such as mayonnaise, bakery, etc.
- In the hydrogenated fat, the product may be in the form of a solid block, which must be melted before use or it may be spray coated to obtain a free-flowing powder.
- To obtain a spray-cooled spice, the blend of spice oil/oleoresin and the fatty carri,er is melted to 45-120°C and atomised in a stream of chilled inert gas (nitrogen) when minute fatty globules are formed and instantly 'set', thereby protecting the entrapped flavour.
- An antioxidant may be added to delay the onset of rancidity on storage.
- The use is limited to fatty products such as dry cake mixes, potato chips, etc., since it is water insoluble. Other methods of encapsulation do not find use in food applications.
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