- Just immersion: Here the Aloe leaves are just dumped into the water with no further action, they could then be manually removed out of the vat or mechanically by means of a conveyor.
- Forced agitation: This is a variation in which the tank has high pressure water jets that create a whirlpool in the soaking tank. The advantage of using this system is that dirt and other foreign material is removed in a more efficient way.
- Manual brushing: Here leaves are hand picked and brushed as they are pulled out of the soaking tank, then they are placed into a conveyor. The advantage of this type of treatment is that it is very gentle on the leaves, and removal of dirt and foreign material is optimal. Also, this can work as an inspection/rejection point. The downside is the higher labor cost.
After leaves are soaked and pre-cleaned they are moved by a conveying system. This can consist of a conveyor belt, stainless steel mesh or polypropylene conveying system. Some companies also use a fluid conveying system, in which the leaves are placed in a canal with water that is being pumped so that the flow moves the leaves along.
Just before the leaves receive the final wash and rinse, they are mechanically brushed. The brushers have plastic brushes that pick the leaves up from the conveyor and press them against two or more brushes giving a cleaning action on every side of the leaves. The purpose for this step is to remove dirt and other foreign material from the surface of the leaves. Depending on the capacity of the plant one or several simultaneous lines of brushes can be installed. Usually the material of choice for these brushes is soft plastic, which vigorously removes unwanted material from the surface of leaves while being gentle enough to prevent injury to the leaf.
This is where the final wash of the leaves occur. The function of this wash is to do the final cleaning to the leaf before entering the manufacturing facility. Options for this step include the use of sanitizing agents such as Chlorine, Quaternary ammonium salts and others. The tank can be made of stainless steel, fiber glass or concrete. This process can also be a two-stage final rinse, first in a sanitizing solution and second in a final rinse with water to remove the sanitizing agent.
Inspection TableLeaves must have an acceptance specification. At this point, the leaves get inspected individually as they enter the process. Leaves that do not meet specs are rejected here. Layout for this station is usually a conveyor that feeds leaves coming from the rinse tank into the table. It has a conveyor to carry waste out and either a series of tables or conveyors to carry the leaves to the next processing step.
It is important at this step to reject any leaves with evident injuries, cuts, or lesions in order to avoid contamination of the product downstream. Tips, tails, and spines are usually cut off the leaves by hand at this stage, so again the layout is such that would accommodate enough people to perform these duties. Typically 6 to 8 people can process 1000 Kg of leaves through this step.
After leaving the inspection table, the aloe leaves goes to the filet machine. The filet machine is a device used to separate the rind from the inner gel of the leaf. The name comes from the resemblance of the inner gel to a fish fillet. An alternative to the use of this machine is to hand-fillet the leaf. The advantage of using a machine is the lower cost of operation in terms of labor, but a disadvantage is that the yield may go down as compared to hand filleting.
All the insoluble rind and fibers goes to waste once the process has finished. This is organic waste, however and can be composted and recycled in the farm.
Whether the aloe leaves are coming off of the conveyor (whole leaf process), or the filets are coming out of the filet machine (aloe filet process), the grinder is where they are both headed. There are specific grinder designs for the mincing of whole leafs of aloe. This machine grinds by impact, then sieves thru a screen with a hole size about 5mm in diameter. The most used type of grinder used in the aloe industry is a hammer mill, with non-swiveling hammers. This type of grinder is the preferred type when processing whole leaf aloe. The intention of this process is to extract the liquid contained in the aloe leaf. Typically the tips and tails are removed before this step. The particle size is controlled by the size of a mesh placed at the bottom of the grinder.
Shell and Tube Heat Exchanger
Shell and tube heat exchangers consist of a bundle of parallel sanitary tubes with the ends expanded in tube sheets. The bundle is contained in a cylindrical shell. Connections are such that the tubes can contain either the product or the media, depending upon the application. The major limitation is that they cannot be used to regenerate, but they can transfer lots of heat due to the surface area.
Recently extracted Aloe is a very viscous liquid so very commonly subject to an enzymatic treatment aimed at reducing the viscosity. Most commonly used enzyme is Cellulase, which is commercially available from a variety of sources. Enzymatic reaction usually takes two to four hours at room temperature. The enzyme, usually in liquid form is added to the vat, mixed and let to react. Typical ratio of use is 20 grams of enzyme for 100 grams of aloe solids in the gel.
Agitated Jacket Tanks
A jacketed tank is a tank with an outer jacket designed to contain heating or cooling media. Product is heated or cooled while being mixed, blended or agitated. A dimple jacketed tank utilizes a simple heat transfer element. First, the heating element is created by pressing a dimpled profile into a flat sheet of stainless steel. This dimpled sheet, referred to as an embossing, is then spot welded to the non contact side of a stainless steel tank to create a flow passage for the heating or cooling media. The end result is a fully welded heat transfer element that is extremely thin (approximately ½" overall thickness). The coils can remain exposed, or they can be covered with an insulation material and then covered with a sheet of stainless steel. Jacketed tanks are not thermally efficient and they cannot be used in a continuous operation.
The Pulper/Finsher is used to remove the insoluble fiber resulting from crushing either the whole leaf or the inner gel fillet. This device usually has a rotating part that is either an endless screw or paddles that push the mixture against a screen. The liquid goes thru the screen and the insoluble fiber is pushed to the end of the machine. The screen can have several different pore sizes, typically ranging from 800 to 500 microns. This machine serves its purpose as a coarse filter very efficiently and quickly.
Charcoal and DE
Aloe vera contains a series of chemical compounds from the family of phenols, particularly anthraquinones. The most common of them is Aloin. These compounds have a potent laxative effect when ingested, so the allowed amounts in finished products is small. The origin of these compounds is the rind of the leaf, being completely absent in the inner fillet gel. Even though inner fillet gel is being produced, contamination with anthaquinones coming from the rind is virtually impossible, and in the case of whole leaf aloe, the amount of antraquinones is very high. The amount of these compounds needs to be controlled and one very effective way by using activated charcoal. This can be accomplished by adding activated charcoal to a tank and then removing the charcoal by filtration or by pumping the liquid thru a column that contains the activated charcoal.
Plate and Frame Filter
This step in the process may consist of a single filter or a series of them. The purpose of this step is either to remove the charcoal added in the previous step or to remove unwanted insoluble fiber. Filtering aids can be used here to facilitate filtration. Most typical types of filters used here are filter presses, however other types of filters have been used as well.
This is a thermal treatment aimed at reducing the bioburden of the product. Typically Aloe contains a natural flora of microorganisms. These once the leaf has been crushed start to reproduce rapidly, so at a later stage of the process the population needs to be reduced to assure stability of the final product. Reduction of microbial population can be achieved using a thermal treatment such as pasteurization. Typical reduction of population is 4 orders of magnitude.
There are mainly three types of pasteurization done today:
LTLT: The acronym stands for Low Temperature Long Time. In this configuration the whole batch is placed in a tank where is heated typically to 140 F (60C) for 30 minutes.
HTST: High Temperature Short Time. This configuration is a continuous process in which the product is heated very quickly (30-60 seconds) in a heat exchanger to temperatures of 170F (77C) and the temperature is held for a brief period of time, 1 to 2 minutes. Then the product is chilled back to room temperature or a little above. HTST systems use a heat recovery system called regeneration in which the hot product is used to exchange heat with the incoming product. This way it self cools and transfers that energy to the incoming product. If necessary or if the desired final temperature of the product is lower than room temperature, and additional section of the heat exchanger is added and water from either a cooling tower or a process chiller is used to further cool the product.
UHT: Ultra High Temperature. This configuration is also a continuous process that works in a very similar fashion as the HTST, but the fluid here is heated to an even higher temperature, 230F (110C) but heat transfer is done very fast, 2 – 5 seconds, and the peak temperature is only held for a fraction of a second.
The boiler provides steam as a source of energy for process heating. It is used for the pasteurization and evaporation operations, as well as a source of heat to produce hot water for formulation and for cleaning. Boilers are usually sized by their steam producing capacity, and by the pressure at which the steam is delivered. The higher the pressure, the higher the energy delivered per pound of steam.
Four Effect Evaporator 4X
In order to increase stability and also to improve efficiency in storage and transportation, it is desirable to concentrate Aloe. Final products that are currently marketed in the liquid form range from 5 times concentrated (5X) to 40X. However since Aloe is sensitive to heat, the concentration must be carried out at the lowest possible temperature. There are numerous designs of evaporators that work under high vacuum to facilitate water evaporation at low temperature. It is also important here to maximize heat transfer efficiency to lower the operational cost of the unit, therefore several evaporation chambers are placed in series and the hot evaporated gases from the first go to heat the second and so forth. This is called a multiple effect evaporator. The more the effects, the more efficient the operation. Typical operating temperature is about 140F (60C).
The Aloe concentrate most marketed today is the powder form. This product is known as 200X powder from aloe inner gel fillets or 100X powder from whole leaf aloe. Final evaporation must also be performed at low temperature to preserve the natural components of Aloe. This is especially important once the aloe solids become more concentrated since they are more suitable to chemically react between each other.
Spray dryers work by converting the Aloe concentrate into a very fine mist of droplets. The droplets form in a conical shaped chamber when the concentrate encounters flow of warm dry air. This then causes the drops to become so small that it increases the surface to volume ratio of the drop facilitating evaporation. The droplets are suspended inside the chamber until they become more dense due to the evaporation. They then fall to the bottom of the chamber in a powder form and collected.
Two types of devices are currently used to make the fine mist of droplets. One is a very high pressure valve in which the liquid is force by pressure (2000psi) to go through a very small orifice which causes the liquid to spray out in a very fine mist. The other consists of a rotating disk on which a stream of liquid is dropped. The centrifugal force of the spinning disk then jets out the liquid, converting it into a fine mist. Rotation of the disk must be very fast, 10,000 rpm typically. Most disks use an air driven turbine to do this.
Vari-Speed Positive Pump
Positive displacement pumps are used to transport fluids from one place to another in the processing facility. These pumps are required for filtering, since the pressures at which they operate are higher.
Diaphragm pumps are used to move fluids with high solids content. Usually they are compressed air actuated. They are very useful in hazardous environments.