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Quotes - Engineering - SalesYogurt fruit prep, jam, fruit fillings, compote
Sugar changes everything about the wall
A strawberry fruit preparation for yogurt is 45 to 55 Brix with whole or halved berries; a jam is 60 to 68 Brix with pectin set; a bakery filling is 50 to 60 Brix with starch. At those sugar levels the product is 1,000 to 20,000 cP, it caramelizes on a wall above about 240 F, and the fruit pieces are softer than anything on a soup line.
The duties are cooking or pasteurizing the prep at 185 to 205 F, holding it long enough for the fruit to reach temperature, and cooling it to 90 F for hot fill or 70 F for aseptic filling into the yogurt plant's bag-in-box.
Cooking, holding and cooling a high-sugar fruit product
Why high Brix products burn on
Sugar at 50 to 65 Brix has a boiling point elevation of several degrees and a caramelization threshold not far above 240 F at the wall. In a plate or a narrow tube the film against a steam-heated surface reaches that temperature long before the bulk does, and the caramel that forms is hard, brown and insulating. The only cure is to keep the wall temperature under the threshold by heating with hot water at a 15 to 25 degree approach and by getting the coefficient from tube length rather than driving force.
The viscosity makes the coefficient poor to begin with, 20 to 40 Btu/h-ft2-F on a 10,000 cP prep in laminar flow, so a fruit prep heater for 20 gpm is long, 150 to 250 feet of 2 or 3 inch tube in several passes.
Cooking and holding with fruit pieces
A yogurt fruit prep is pasteurized rather than cooked: heated to 185 to 195 F, held 2 to 5 minutes so the center of a strawberry half reaches temperature, and cooled to 70 to 90 F for aseptic filling. The hold is validated on temperature at the center of the largest piece, not on residence time alone. Jam is cooked in a kettle or vacuum pan, so its exchanger is mostly a cooler.
Velocity in the tubes is held to 0.5 to 1.5 ft/s. Faster than that a soft fruit piece shears at the bends and arrives as puree. The pump is a low-shear rotary lobe or progressing cavity type. Fruit and vegetable duties beyond preparations and jams are covered on our fruit and vegetable processing pages.
Cooling without setting the product
Cooling is where the pectin set and the viscosity climb both arrive at once. A jam at 195 F is perhaps 1,000 cP; at 90 F it is 20,000 cP and starting to gel. Tower water at 85 F in one step sets the product on the first tube. The cooler is staged: tempered water at 150 F first, then 110 F, then tower water, with the approach on each stage held to 20 to 30 degrees so the product cools evenly across the bore rather than freezing at the wall while the center is hot.
Where the product has to reach 40 F, or where it sets hard at the target temperature, a scraped-surface unit takes the last stage; a tube-in-tube cannot cool a gelled jam.
The common mistake
Cleaning a jam line by running caustic straight into a tube full of cold product. The caustic hits solid jam and the pump dead-heads. Every high-Brix CIP starts with a hot water melt-out at 160 to 180 F until the return runs clear, then caustic, then acid. Send the Brix, the viscosity at cook and at fill temperature, the piece size and the temperatures in and out. Call and talk it through with an engineer: 1-805-484-2992
Fruit preparation and jam process conditions
Sugar level, particle size and wall temperature drive every row below. Check your recipe against them, then send the Brix, the largest piece and your hot water supply so the heater can be sized.
| Condition | Detail |
| Product | Fruit prep 40 to 55 Brix; jam 60 to 68 Brix; fillings with starch; 1,000 to 20,000 cP; pieces to 1/2 inch |
| Flow range | 5 to 60 gpm |
| Temperatures in / out | Cook 185 to 205 F; hot fill at 185 F; yogurt prep cooled to 70 to 90 F |
| Hold | 2 to 5 minutes at 190 to 200 F so the center of the largest piece reaches temperature |
| Utility | Hot water 215 to 225 F; tempered water then tower water on the cooler; glycol only on chilled product |
| Approach | 15 to 25 degrees on the heater; 20 to 30 degrees staged on the cooler to avoid a set on the wall |
| Construction | Single tube-in-tube 2 to 3 inch bore; corrugated tube on smooth jam |
| Finish / class | 316L, 32 Ra product side; food-grade drainable; 3-A on dairy-bound fruit prep |
| CIP | Hot water melt-out, caustic 1.5 percent at 170 F, acid for pectin and calcium; every 8 hours |
Common FAQs
Not with pieces, and not above about 2,000 cP without them; the channel is too narrow and a pectin set blocks the pack. Tube-in-tube with staged cooling is the standard, scraped surface for a product that gels.
Plain tubes with a 2 to 3 inch bore, 0.5 to 1.5 ft/s, long-radius jacketed bends and a low-shear pump. Corrugated tubes and high velocity turn whole fruit into puree.
Juice has to hold the fluid at temperature for seconds. Fruit prep has to bring the center of a 1/2 inch berry to 190 F, which takes over a minute of conduction, so the hold is 2 to 5 minutes and validated on the piece.
Hot water at a 15 to 25 degree approach instead of steam, a wall under 240 F, and tube length for area. Once caramel starts on a steam-heated wall it insulates the tube and gets worse, not better.
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