The answer in a word is “No.”

Bacterial and yeast cells are very slippery and malleable. They can very easily slip and slide through the rotor/stator actions with little or no significant damage.

If you want to break up bacteria or yeast cells, then the only two ways to do so would be with a sonicator or with what is called a “high pressure/high shear” homogenizer. The sonicator produces high frequency sound waves from which the bacteria cannot “run and hide from,” and it causes them to break apart. The high-pressure unit forces the sample containing bacteria through a very small orifice, and the combination of the high pressure and being forced through the small orifice causes the bacteria to literally burst open.

If you want to isolate bacterial cells from a sample containing cell wall materials that encapsulate the bacteria, then use the POLYTRON in the isolation procedure to obtain viable bacterial or yeast cells.

The major concern here: Honey and syrup are very thick and generally in their natural states, you cannot homogenize them because the generator simply cannot adequately draw the products through the rotor/stator. While they are flowable, sometimes the only way to get such products homogenized is to use an in-line system with a pump to force the product into the rotor/stator. Therefore, I am not much concerned about the broth or soup, but it will take a bit more thought for the honey and syrup applications. Salad dressings and mayonnaise also don't concern me that much with a normal batch KINEMATICA POLYTRON homogenizer. The question is a matter of percentages—if honey and syrup are the minor applications and the others mentioned are the major ones, then I would be prepared to make a rather straightforward recommendation. If the majority of applications is syrup or honey, then the recommendation would not be so straightforward and would require more thought. Obviously we have production machines that have enough torque to turn a rotor in the honeys or syrups, but they would not be suitable for your laboratory bench.

No matter what, I would most probably recommend the POLYTRON Model PT 6100 since it is able to handle the more viscous products (excluding honey and syrup). I would also recommend the use of one of the W generators to handle the fibrous materials. Model PT 6100 has a 1,600-W motor that is adequate for large-scale laboratory applications as you are describing.

For a volume of 1 L to 2 L, then I would suggest the 3030/2W. Its volume range is about 100 ml to 3,000 ml.

If it is just emulsions—I consider your points 1 and 3 the same type of application—then whether to go with a /2 or /4 generator would be based on the development of the viscosity of the product during processing. I generally prefer to use the /2 as it requires less torque to turn and results in a higher speed of the rotor—this also results in production of emulsions due to the higher speed being better able to reduce particle sizes. I would most likely stay with the 30-mm size generator, just not the W style for routine procedures.

If you have a lot of work in the 5-L range, then I would recommend using a 40-mm generator.

If most of your applications are in the honey or syrup viscosity range, Model PT 6100 is not the unit for your application. You might then be better off considering Model PT 7000 or PT 36-60 due to the higher torque motors (they would also accept the same style of generators for Model PT 6100). All the generators for Model PT 3100 can also be use on Model PT 6100.

The following applications are for Models PT 2100, PT 3100 and PT 6100.

Pharmaceuticals

• Manufacture, R&D, or sample preparation for testing of
  • Tablet coatings
  • Cough syrups
  • Creams and lotions
  • Ophthalmic and contact lens solutions
• Mixing of sterile or aseptic ingredients
• Assay of pharmaceutical products, such as disintegrating tablets or caplets prior to analysis

Cosmetics and toiletries

• Dispersion and hydration of Carbopol®, a polymer commonly used for emulsifying, stabilizing, thickening, etc. in cosmetics
• Manufacture or R&D of
  • Suntan lotions or creams
  • Cosmetic creams and lotions
  • Nail varnishes

Chemical

• Dispersion of titanium dioxide (white pigment used for paints)
• Production and R&D of
  • Paper coatings (include pigments and other additives)
  • Pesticides
  • Polymer and pigment dispersions in textile manufacture
  • Ink jet coding and marking and printing inks
• Quicker and better mixing and dispersing of calcium carbonate used in paper production

Food

• Production or testing of
  • Tomato sauces and ketchup
  • Salad dressings
  • Flavor emulsions
  • Yogurt premixes
  • Baby milk and mayonnaise
• Sample prep for aflotoxin testing

Carbopol® is a registered trademark of B. F. Goodrich Company.

Cleaning of POLYTRON Generators

• All POLYTRON Generators must be completely cleaned after each use
• Never allow chemicals to dry on a generator
• Always neutralize strong acids and bases
• Always store generators dry (i.e. rinse with ethanol)
• Always clean generators IMMEDIATELY after using any of the following chemicals or chemical types:
  Acetic acid, bisulfites, chloroacetic acid, chromic acid, concentrated solutions of halide salts (i.e. NaCl, KBr, etc.), formic acid, guanidinium salts, hydrochloric acid, phosphoric acid, sulfuric acid, water-soluble sulfide

Cleaning and disinfecting generators for POLYTRON Benchtop Homogenizer Models

Cleaning

1. Run the generator in a suitable solvent, water, or detergent solution for approximately 1 minute at 1/2 power; repeat at least 2 times
                                 OR
   Immerse the lower portion of the generator in an ultrasonic bath, following the directions of the bath manufacturer
   NOTE: DO NOT immerse the coupling/ball bearing assembly in any liquid.
2. Run the generator in clean water for approximately 30 seconds at maximum speed; repeat 2 times
3. Run the generator in absolute ethanol for 25 seconds at maximum speed; repeat 3 times

   Disinfecting

   POLYTRON Generators may be disinfected with commercially available disinfectants. It is recommended that the generator be cleaned after disinfecting to prevent the disinfectant from drying on the generator.
   NOTE: DO NOT immerse the coupling/ball bearing assembly in any liquid.

Sterilizing generators for POLYTRON Benchtop Homogenizer Models

Autoclaving

POLYTRON Generators may be autoclaved under standard conditions, i.e. 121°C, 15 psi, for 15 minutes.
NOTE: Due to the lubricant in the ball bearing, it is recommended that generators be placed in an upright position for autoclaving.

Cleaning and disinfecting generators for POLYTRON Handheld Homogenizer Models

Please refer to the POLYTRON Homogenizer Instruction Manual for generator disassembly instructions.

Cleaning and Disinfecting

1. Generator parts may be cleaned chemically, by manual scrubbing, or in an ultrasonic bath
2. Generator parts should be completely dried or rinsed with absolute ethanol Sterilization Generator parts may be sterilized under standard conditions in an autoclave, i.e. 121°C, 15 psi, 15 minutes.

POLYTRONs spin at a maximum speed of 27,000 or so rpm, but until you can put that into “human terms,” it is a meaningless term. The quoted speed is the motor speed, not the actual speed of the rotor where all the homogenization occurs. Rotor speeds will differ based on the diameter of the generator and once you see those speeds, then you can better understand why a smaller generator is less efficient than a larger one.

Having the rotor speed in mph will show why the POLYTRONs reduce particle sizes as effectively as they do. Also, as is apparent in the table below, a motor speed of 27,000 rpm gives very different rotor speeds depending on the size of the rotor!

Generator diameter	Speed in mph at 10,000 rpm	Speed in mph at 20,000 rpm	Speed in mph at 27,000 rpm
5 mm	6	12	16
7 mm	8	16	23
10 mm	12	24	32
20 mm	24	48	65

The equation is (rpm x 3.14 x rotor diameter)/26.8 = rpm in mph.

The higher the tip or rotor speed, the smaller the particle sizes, and the less time that is required for treating any given sample. Now you see why it may take longer for a smaller generator to achieve the same result as a larger one does in a shorter time.

There has always been a question regarding how deep to immerse the generators into a solution. Here is the general rule of thumb and the consequences for not doing so.

The standard generators that have the long, open slots in the sides can be immersed up to the top of the lower slot or roughly half way up the generator.

The foam-reducing generators, which are becoming more predominant and are characterized by having a set of holes at the bottom and top, can only be immersed up to the lower set of holes. You should immerse them no deeper—especially with the 5- and 7-mm generators.

Why? The distance between the rotor and stator is so small in these smaller generators that you will have capillary action of the liquid between the rotor and stator. This will lead to liquid getting up into the upper bearing or portion of the generator and either leading to the bearing being compromised or, worse yet, the liquid getting into the motor.

The reason for the upper set of holes is to minimize, as much as possible, the capillary action from occurring, but it cannot eliminate it, especially with the 5- and 7-mm sizes.

You have a bit more leeway with the 10-, 12- and 20-mm generators. Since there is more room between rotor and stator, there is less likelihood of capillary action occurring. Even with these generators, do not go above those lower holes. If you need more immersion depth, then opt for one of the generators with the long slots.

Never run the generator dry.

Why? The lower bearing needs lubrication and that lubrication comes from the circulating liquid of the sample. If that lubrication is not present, the bearing will be damaged and have to be replaced. This is why you always need the liquid up to the lower set of holes of the generator.

How do you know if the lower bearing is damaged?

Usually you can take the generator, hold it upside down and tap it with your finger. If you hear a lot of rattling, then there is a good possibility that the lower bearing is damaged. If the generator is not an EasyCare, it needs to be sent to the office for repair.

There has always been a somewhat on-going debate regarding when to use one style generator over the other. The literature seems to make a clear distinction between the three different rotor/stator combinations. Keep in mind that most of the generators you use are of the /2 variety and for good reason:

• /2 for routine homogenizations and/or dispersions (most of the motors only accommodate this style of generator)
• /4 for production of emulsions and dispersions
• /6 for production of finest emulsions and dispersions

Just a couple of definitions here as well:

1. Emulsions are “dispersions” of two immiscible liquids (i.e., oil and water) that stay suspended and do not separate.
   Dispersions are “dispersions” of a liquid and solid such that the solid particles stay suspended and do not readily separate or precipitate out.

In order to create either one of the above, you have to have sufficiently high rotor speeds to break down the particles small enough so that they will stay suspended. Remember, as you add rotor and stator teeth, you also add drag to the motor that will mean slower rotor speeds even if the sample is only water.

Slower rotor speed means less efficient processing or not as fine particles within a given time period. This ultimately results in failure to produce the desired “dispersion.”

How can you keep rotor speeds sufficiently high? Increase the wattage or torque of the motor to overcome the drag that is created by the generator teeth. This is the reason why most /4 and /6 generators are listed with Model PT 6100 rather than Model PT 3100. Only Models PT 3100 and PT 6100 should be used for emulsion or dispersion production.

If you want to produce an emulsion or dispersion in a very fluid, water-like medium, then use the /2 or /4 with Model PT 3100. Your preference should be to use the /2. The /4 could be used, but it would be infinitely better to then use Model PT 6100.

If you want to produce an emulsion or dispersion in a liquid with some degree of initial viscosity, then start with a /4 or /6 generator used only with Model PT 6100. The higher wattage motor will be the only way to maintain the proper rotor speed for any length of time. The drag on Model PT 3100 motor will be too significant for proper rotor speed and safe motor operation. You may be forced to back all the way down to a /2 just to have enough speed to break up the particles—it may take longer, but at least you will get the desired result!

Are any of the generators for one model able to be used on another model?

The answer is that there are some generators that can be used interchangeably and others that cannot. Below is a list of all the units and the generators that can be used with them.

All generators for these three models can be used interchangeably

• PT 1200 E
• PT 1300 D
• PT 1600 E

All generators for these two models can be used interchangeably.

• PT 3100
• PT 6100

However, it is not advisable to use Model PT 6100 generators on Model PT 3100, but using Model PT 3100 generators on Model PT 6100 is allowable. The thing to know is that the coupling is the same for both models.

One-way interchangeability with the coupling

• PT 10/35
• PT 3100

The generators for Model PT 10/35 along with the PTA coupling permit their use with Model PT 3100. The reverse is not true and never will be. You cannot use a Model PT 3100 generator on Model PT 10/35.

No interchangeability with any other model

• PT 2100

There are currently two styles of generators for Models PT 10/35, PT 3100 and PT 6100. One style is referred to as the standard and the other as foam reducing. What are the real differences and when should one be used over the other?

The standard generator shown above has the slots allowing you to readily see the rotating shaft and to easily and thoroughly clean and inspect the generator. This generator will most likely create more aerosols during processing due to the open slots and the exposure of the sample to the rotating shaft. Keep in mind that the sample is being drawn in from the bottom of the generator and out through the sides of the stator teeth as shown in the drawing below.

Most of us have thought that there is a significant introduction of air through the slots. Not so, as for this to happen the sample would have to be drawn from the top down through the shaft into the generator.

The foam-reducing generator, shown above, is a solid stator tube with usually two to four holes in the tube. The 5-, 7- and 10-mm generators have four holes in them. The two at the top are there to eliminate or minimize capillary action of the sample traveling up between the rotor and stator into the upper ball bearing and motor. The two lower holes are to promote adequate lubrication of the lower bearing from the sample circulation. This generator will most likely create fewer aerosols during processing because the rotating shaft is “covered up” and thus there is less exposure of the sample to the rotating shaft.

Both styles of generators will give you equally efficient homogenizations.

When to use one over the other?

First of all, most of the generators for Models PT 1200 E, PT 1600 E and PT 2100 are only available as “foam-reducing” models, thus making any discussion of the two styles a mute point.

Second, if you have a sample that is difficult to clean, use an EasyCare^® model. However, all of the generators for Model PT 10/35 are not EasyCare and cannot be taken apart for cleaning. The standard generators are more easily cleaned and can be visually inspected for their cleanliness.

Third, if you want to do a homogenization in a closed vessel or environment, then there is only one choice—the foam-reducing model. You will also need one of the standard tapered fittings to properly seal off the homogenization from the environment. The same applies for EasyCare models.

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