Instantization of Milk

Instantization, Agglomeration,Types,Features,SPRAY DRYING AGGOMERATION, REWET AGGLOMERATION,Techniques, PEEBLES PROCESS,CHERRY-BURREL PROCESS,BLOW-KNOX PROCESS,NIRO/ANHYDRO AGGLOMERATOR, Instantizing of powders

1. INSTANTIZATION OF MILK AND MILK PRODUCTS M.Meenakshi Assistant Professor, Department of Microbiology, Sri Ramakrishna College of Arts & Science for Women, Coimbatore

2. INSTANTIZATION OF MILK AND MILK PRODUCTS Powdered milk or dried milk is manufactured dairy product made by evaporating milk to dryness.One purpose of drying milk to preserve it, milk powder has a far longer shelf life than liquid milk and does not need to be refrigerated , due to its low moisture content. Another purpose is to reduce its bulk for economy of transportation. The historic development started with the pioneering research of Mr. David D. Peebles in the beginning of the fifties, and instantized non-fat dry milk was marketed from 1954. The principle of instantization is the agglomeration of individual spherical milk particles into clusters and the conversion of lactose from the glass into a microcrystalline form which makes the powder more wettable and less hygroscopic. In the instantization process, the surface of milk powder particles are humidified, or the particles are only partially dried during manufacturing, so that the surface is tacky and partial crystallization of lactose leading to formation of microcrystals occurs before the particles are redried . This produces a clustering of the particles in loose spongy aggregates of low density (known as agglomerates / conglomerates / granulates ) which flow freely and disperse readily in cold water, as water penetrates the spongy structure of these aggregates and allow them to sink and disperse. The principal purpose of agglomeration, also called instantizing , is to improve the rate and completeness of the reconstitutability of dry milk products. Small single particles dissolve instantly in water. Powder consisting of small particles is, however, difficult to disperse. Big particles are easy to disperse in water, but dissolve only partially. Agglomeration is a result of wet and/or semi-dry particle collision with size >125 µm. Control is achieved by returning dry fine powder to the wet spray during different stages of spray drying. Mastering the agglomeration techniques is the art of modern spray drying. Plant operation and economics are other important parameters.

3. INSTANTIZATION INSTANTIZATION OF DRIED MILK: Instantization refers to the process by which dried milk and milk products are made instant-soluble. PURPOSE: The chief purpose of instantizing is to improve the rate and completeness of the reconstitutability of dry milk and milk products. The instantizing process affects wettability, sinkability , dispersability and solubility of the particles; however, total solubility is not improved. PRODUCTS: Mainly applied to skim milk powder/non-fat dried milk. However, whole milk powder and other milk fat containing dry dairy products are also being instantized . FACTORS INFLUENCING INSTANTIZATION: Dry milk that is manufac­tured especially for instantization usually yields the best results. Moisture content and particle size should be as uniform as possible. A minimum of fine particles, less than 20 µM in diameter, is desired, while particles in the range of 25 to 50 µM are preferred. The skim milk powder for agglomeration should be low in fat content. Low heat or medium heat skim milk powder is normally used, since high heat skim milk powder shatters much more easily in handling after instantization .

4. FEATURES OF AGGLOMERATION Wetting of the surface of the particles with steam, atomized water, or a mixture of both (in a tube or chamber); Agglomeration, which occurs because the parti­cles collide with each other due to turbulence, and adhere to each other to form clusters ( in a tube or chamber or cyclone  Re-dry­ing with hot filtered air (in a chamber or cyclone or deck); Cooling; Sizing to eliminate the very large agglomerates and the very small particles, and packaging .

5. BASIC DIAGRAM THAT DESCRIBES THE PROCESS OF CREATING AGGLOMERATED PARTICLES VIA SPRAY DRY PRINCIPLES.

6. TYPES OF AGGLOMERATION The instantizing process has been applied to dry whole milk and other milk fat containing dry dairy products with only limited improvement in reconstitutability resul The process may be carried out using either of these two methods: Spray Drying Agglomeration Rewet Agglomeration Spray drying aggomeration During the spray drying process, the aim is to produce particles with a big surface/mass ratio, i.e. small particles. The reconstitution in water of a powder consisting of small particles is however difficult and requires intensive mixing in order to disperse the powder, before it is totally dissolved. Bigger particles exhibit a better dispersion, but the solubility is negatively affected during the drying operation. By agglomeration both a good dispersion and a complete solution are obtained. The milk fat adversely affects wettability because of its hydrophobic property. Rewet agglomeration Since many powders may become instant by the mere agglomeration, many processes have been developed during the past years to agglomerate ordinary powders consisting of single spray particles usually produced in plants with pneumatic conveying system.

7. TYPES OF AGGLOMERATION PROCESS Major systems of instantization of milk powders are Peeble process, Cherry- Burrel process, Blow-Knox process and Niro agglomerator . Each varies in equipment and details. The general features in common are:Wetting of the surface of powder particles with steam, atomized water or a mixture of both.Agglomeration whereby the particles collide due to turbulence and adhere to each other forming clusters.Redrying with hot air Cooling and sizing to eliminate the very small particles and very large agglomerates . PEEBLES PROCESS:  The powder pneumatically enters the agglomeration chamber. The particles are wetted to 10-15% moisture in the turbulent air-stream zone and form agglomerates. These fall into the next zone or chamber which re-dries them by means of filtered air at 110-121oC. The product is cooled, sized with rollers, screened and packaged. The fine particles are returned to be recycled through the agglomeration process. CHERRY-BURREL PROCESS:  This process consists of delivering dried milk at a uniform rate by air, screw or vibrator to a horizontal tube. Wetting and agglomeration takes place in the most rapidly moving air-product mixture, which passes into the cyclone. During wetting, the moisture of milk powder increases to 6-8%. Air returns from the top of the cyclone to recycle and the clusters drop into a filtered hot-air stream at 132-149oC. The product, while moving into the second cyclone, is dried by this air. The air is exhausted from the top of the cyclone and the product clusters descend into a horizontal shaker through which cooling reduces the temperature from 71-82oC to 37-38oC. The sifter removes the fine particles. The clusters pass through sizing rolls and are sifted and packaged.

8. TYPES OF AGGLOMERATION PROCESS BLOW-KNOX PROCESS:   Dried milk is measured by a rotary-feed valve into a line and fed pneumatically into a small agglomerate tube. An alternative system uses a vibrating trough to control product entry into the agglomerating tube. Steam wets the particles to about 7% moisture as they fall between two jets. Ambient air entering through radial slots in the agglomerating tube maintains the turbulence necessary for the formation of aggregates. The agglomerated product drops onto a conveyer belt for conditioning and transport to deck-type vibrating re-driers. Dried agglomerates are screened after they pass between sizing rolls. Fine particles are reprocessed through the system . NIRO/ANHYDRO AGGLOMERATOR:   It is an attachment fixed to the bottom of the vertical-type drying chamber. Milk is dried to about 9% moisture content in the drying chamber. A vibrator transports the product from the drier to the inlet of the Niro agglomerator that consists of three sections.In the first section, agglomeration takes place; in the second section, redrying with hot air; and in the third, the product is cooled to room temperature. Very fine mesh screens convey the product through the three sections. Air that passes up through the screens goes out carrying the fine particles from the top of the agglomerator . Fine particles are returned to the drying chamber

9. INSTANTIZATION OF MILK AND MILK PRODUCTS Processing a powder mix so it dissolves instantly in a liquid is enhanced when a surface active agent is included. Instantizing is a term that describes various processes that make a powdered product "instant." That is, instant in the sense that it has good reconstituting properties so it disperses or dissolves quickly when added to a liquid . Instant dairy-based products include powdered mixes such as chocolate drink, coffee whitener, infant formula, nonfat dry milk and protein drinks . When powders rewet too quickly, a gel layer forms, preventing liquid from penetrating the powder particles . The result in both scenarios is that the powders remain on the surface of the liquid. In other words, they do not readily dissolve.

10. INSTANTIZATION OF MILK AND MILK PRODUCTS Reconstituting properties affect consumers' perception of quality, as consumers expect drink mix to dissolve immediately. They also impact food and beverage manufacturers, who require consistency and ease in handling. Instantizing of powders is a complex matter because of the range in properties of the different types of materials that can be instantized , as well as the varying properties of the liquids into which the instantized powders are dispersed. For example, some powders are hydrophobic (e.g., whole milk powder), having a large amount of free-surface fat that forms a barrier and prevents liquid from penetrating it. Others are hydrophilic, or water-loving (e.g., protein powders), and rewet too quickly on the surface.

11. INSTANTIZATION OF MILK AND MILK PRODUCTS To further complicate the process, it is often desirable to have powders that have the flexibility of being able to be dispersed in liquids with different properties. For example, with some beverage mixes, the same powder might be dissolved in cold or hot water, in cold nonfat milk (solids present), in cold whole milk (fat and solids present), in hot milk or even into high solids mixtures such as those used to make smoothies. This poses quite a challenge. Whey protein powders are particularly challenging systems to instantize , as whey proteins vary in particle size, shape and surface properties. Thus, with whey protein powders, seldom will the same powder dissolve in all liquid systems. In fact, when deciding how to instantize whey protein powders, it is important to keep in mind that process is often application specific. Finally, finished product quality depends on what type of instantizing process is actually used. In almost all cases, the instantizing process is optimized when a surface active ingredient is used, as surface active agents greatly enhance reconstituting properties.

12. INSTANTIZATION OF MILK AND MILK PRODUCTS There are two basic steps for improving powder rewetting properties-agglomeration and lecithination . Agglomeration imparts a coarse, porous structure to powders. Agglomeration relies on capillary forces within the cavities to allow the liquid to penetrate. As the granule sinks, the bridges formed during agglomeration dissolve and the product disintegrates . During the lecithination process, the powder is coated with a surface active agent that compensates for either the swelling of hydrophilic surfaces Surface active agent selection is critical to the desired performance for the finished product .. For example, you can improve the wetting time of a powder with 5% free surface fat by approximately 70% if you choose the correct type of lecithin. The wetting time is also maintained over a longer period of storage time. By choosing a high-performance lecithin product, we can increase the wettability at 6 months by 80%. To determine the best type of surface active agent for the product and process, it is important to work closely with your ingredient supplier to optimize the process.

13. AGGLOMERATING AND INSTANTIZING These processes have allowed the manufacturing of milk powders with better reconstitution properties, such as instantized skim milk powder.  Agglomeration Mechanism : Powder is wetted with water or steam. The surface must be uniformly wetted but not excessively. The powder is held wet over a selected period of time to give moisture stability to the clusters which have formed. The clusters are dried to the desired moisture content and then cooled (e.g., fluid bed). Dried clusters are screened and sized to reduce excessively large particles and remove excessively small ones. The agglomeration process causes an increase in the amount of air incorporated between powder particles. More incorporated air is replaced with more water when the powder is reconstituted, which immediately wet the powder particles. 

14. AGGLOMERATING TECHNIQUES REWET METHODS: This method uses powder as feed stock. An example is the ARCS Instantizer . Humidified air moistens powder, which causes it to cluster. It is re-dried and wetted. The clustered powder is then exposed to heated, filtered, high-velocity air. The dried clusters are then exposed to cooled air on a vibrating belt. It is then sized (pelleted to uniform size) and the fines are removed.  STRAIGHT THRU PROCESS: A multi-stage drying process produces powders with much better solubility characteristics similar to instantized powder. This method uses a low outlet temperature which allows higher moisture in powder as it is taken from spray drier with excess moisture removed in the fluid bed. The powder fines are reintroduced to the atomizing cloud in the drying chamber

15. METHODS OF PERFORMING AGGLOMERTION DROPLET AGGLOMERATION In the droplet agglomeration process, the powder particles are wetted with droplets of liquid atomized by means of a nozzle or a rotary atomizer while suspended in air. The powder may either be introduced around the rotary atomizer or the nozzle by means of gravity or pressure air conveying, or from below by means of pressure conveying. The droplet agglomeration process is especially used for powders containing fat such as whole milk powder and powders with a high content of sugar such as cocoa-milk-sugar mixtures. If cold-water instant whole milk powder is produced, a lecithin dosing equipment is installed between two Vibro -Fluidizers. However, the final product quality will never be as good as that produced on a drying plant equipped with fines return, fluid beds and lecithin dosing equipment. SURFACE AGGLOMERATION In the surface agglomeration, either steam or warm moist air with a high relative humidity is used as the moistening agent. The surface of the individual dry particles is wetted due to condensation of the water vapour on the colder particles, whereby the stickiness required for the agglomeration is created. The subsequent agglomeration will take place, if the particles are exposed to sufficient mechanical impact. The warm humid air is usually made by spraying steam into warm air at a given temperature to obtain a relative humidity of 100%. The surface agglomeration is mainly used for skim milk powder when large agglomerates are aimed at. The final product properties depend to a great extent on the raw material used for the rewetting

16. REFERENCES https:// onlinelibrary.wiley.com/doi/10.1002/9781118406281.ch1 http://ecoursesonline.iasri.res.in/mod/page/view.php?id=5662#:~:text=The%20principle%20of%20instantization%20is,more%20wettable%20and%20less%20hygroscopic.& text=Big%20particles%20are%20easy%20to,water%2C%20but%20dissolve%20only%20partially . https:// www.dairyfoods.com/articles/83032-instantizing-dairy-foods https:// www.agricultureinindia.net/dairy-science/dried-milk/dried-milk-instantization-packaging-storage-and-keeping-quality/20320