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Quotes - Engineering - SalesFrozen dessert mix
Milk with everything in it
Ice cream mix is 10 to 16 percent fat, 10 to 12 percent milk solids-not-fat, 12 to 16 percent sugar and up to 0.5 percent stabilizer: 36 to 42 percent total solids. It behaves that way in an exchanger: 50 to 150 cP cold, fouling faster than any fluid milk product because sugar and protein caramelize together on a hot wall, and shear-thinning. The PMO puts it at 175 F for 25 seconds, or 155 F for 30 minutes in the vat.
The parent page covers the yogurt mix pasteurizer. Ice cream mix is a different fluid.
Pasteurizing, homogenizing and cooling a high-solids mix
The mix pasteurizer
Mix is blended at 100 to 120 F, where powders dissolve and fat melts, so the regenerator has less to do than on milk and the heating section more. From 110 F to 175 F the wall is where the trouble is: sugar and milk protein form a harder, browner deposit than milk fouling, fastest in the last 15 degrees. HeatX sizes the heating section with 25 to 30 percent more area than the same lift on milk, on wide-gap plates or in a tube-in-tube.
The 25 second hold is timed on the mix. At 175 F the mix is 5 to 10 cP, three to five times milk, so a holding tube that is turbulent on milk can be transitional on mix and the fastest particle moves toward 2 times mean. A plant that runs both on one frame carries two timed settings.
Where the homogenizer goes
Mix is homogenized hot, at 145 to 175 F, because the fat is liquid and the emulsifier active, so the homogenizer sits between the heating section and the holding tube on nearly every line. The exchanger then sees the homogenizer's pressure: a two-stage unit at 2,000 and 500 psi has a pulsing suction, and the section upstream needs a rating a gasketed frame can just cover and a tube-in-tube covers without thought.
Homogenizing after the hold is done on some lines under PMO rules. HeatX lays out the pasteurizer for whichever position the plant's reviewer has approved.
- Section upstream of the homogenizer rated for suction pulsation
- Timing pump remains the timing pump; the homogenizer does not set the flow
Cooling to the aging tank
After the hold the mix is regenerated against the incoming blend, then cooled on chilled water and glycol to 36 to 40 F and pumped to an aging tank for 4 to 24 hours while the fat crystallizes and the stabilizer hydrates. The cooler sees viscosity climb from 10 cP at 100 F to 100 cP at 40 F, and the shear-thinning mix runs thicker still in the outer channels of a plate pack. Wide-gap plates at 2 to 3 ft/s are the floor; premium mix goes to a 1.5 inch tube-in-tube glycol cooler.
The glycol stage must not freeze the wall. Mix with 15 percent sugar freezes around 27 F; glycol at 20 F at low flow lays a frozen layer a plate pack cannot shed. Glycol at 25 to 28 F and enough area is the design. Aging, freezing and the rest of the ice cream line are covered on our ice cream mix processing page.
The common mistake
Running mix on the fluid milk pasteurizer with the setpoint turned up. Milk plates at 3 mm gap foul with mix in two hours, the holding tube is transitional on mix and short by a third, the homogenizer's pressure sits on a section rated for milk, and the cooler channels and delivers 48 F mix to an aging tank that spends four hours getting it to 40 F. Every one of those is a design item on a pasteurizer built for mix.
Send the mix formula or solids and fat, the flow, the setpoint, the homogenizer position, the aging tank temperature and the utilities. Call and talk it through with an engineer: 1-805-484-2992
Ice cream mix process conditions
Mix is thin when hot and heavy when cold, and the rows below reflect both ends of that range. Set them against your recipe and batch or continuous setup, and send the stabilizer level when you request a quote.
| Condition | Detail |
| Product | Ice cream, frozen yogurt, sherbet and soft-serve mix; 25 to 42 percent solids |
| Flow range | 1,500 to 25,000 lb/h continuous; 300 to 1,500 gallon vats for batch |
| Temperatures in / out | Blend at 100 to 120 F in; 175 to 180 F setpoint; 36 to 40 F out |
| Hold | 25 seconds at 175 F continuous; 30 minutes at 155 F in the vat |
| Utility | Hot water at 180 to 185 F; chilled water then propylene glycol at 25 to 28 F |
| Approach | 5 to 8 degrees on heating; 8 to 10 on glycol |
| Viscosity | 5 to 10 cP at 175 F; 50 to 150 cP at 40 F |
| Construction | Wide-gap plate for standard mix; tube-in-tube for premium and high-stabilizer mix |
| Finish / class | 3-A, 316L, 32 Ra; EPDM or nitrile gaskets |
| CIP | Warm rinse, caustic with surfactant, acid; 4 to 8 hours between |
Common FAQs
175 F for 25 seconds continuous, or 155 F for 30 minutes in a vat, under the PMO frozen dessert provisions. Some jurisdictions accept 180 F for 15 seconds.
Sugar and protein together at a wall above 165 F form a hard, brown deposit, and mix has three times the solids to feed it. A small approach, extra area and velocity stretch a two hour run to six or eight.
Between the heating section and the holding tube on most lines, so the mix is homogenized at 145 to 175 F with the fat liquid. The heating section is rated for the suction pulsation.
To about 44 F. Getting to 36 to 40 F for the aging tank needs propylene glycol at 25 to 28 F on the last stage. Colder glycol freezes mix on the wall.
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