Tunnel, hot-fill or cold chain? Picking the kill step for your drink.
Your drink's pH says whether it can be shelf-stable. The kill step decides how it gets there, and what that does to flavor, package and cost.
By Sam Ronkin · November 12, 2026 · 6 min read
Guide 01 covered the pH 4.6 line. At or below it, C. bot can't grow, but yeast, mold and acid-tolerant bacteria still can. Left alone they ferment sugar, swell cans and turn a drink sour. The kill step is the point in production that deals with them, and with the pathogens that can survive in an acid drink.
A high-acid drink has three practical routes. Two use heat and give a shelf-stable product. The third skips the heat and keeps the drink cold for its whole life.
Tunnel pasteurization: heat it in the package
The drink is filled cold and sealed. The closed cans or bottles then ride a slow belt through a tunnel where water sprays warm them, hold them at temperature, and cool them back down. Because the package is already sealed, nothing can get back in afterward.
How the dose is counted
Brewers measure heat treatment in pasteurization units. One PU is one minute at 140°F (60°C), and each degree above that counts for more: a minute at 154°F (68°C) is worth about 14 PU. Tunnels can be built to deliver from 5 to 2,500 PU, depending on what the drink needs. Published figures put standard-strength beer at roughly 10 to 14 PU and alcohol-free beer at 41 to 83, because alcohol and hops do part of the work. A sweet drink with no alcohol has fewer of those hurdles, and leftover sugar is what ferments in the can.
The same dose can be reached at a lower temperature over a longer time, or hotter and faster. For flavor, hotter and faster usually wins: heat damages flavor and color more slowly than it kills microbes, so a short, hot process does less harm for the same kill. Carbonated cans push the other way. Pressure inside a sealed can climbs with temperature, so carbonated drinks are held cooler for longer to stay inside the can's limit.
Lower and longer, or hotter and shorter
Hold time needed
2.5 PU per minute at this temperature
Minutes to reach the same dose
Hot-fill: heat it before the package
Here the drink is heated first, usually to 180 to 200°F, and filled while still hot. The liquid's own heat treats the inside of the bottle and the cap. The closure is steamed as it goes on, or the bottle is tipped so hot product touches it. After a short hold the bottle is cooled, and the shrinking liquid pulls a vacuum that locks the lid down.
Acid foods tolerate this because the heat needed is modest. Published minimums for foods at pH 4.1 or below run from 12.7 minutes at 140°F down to six seconds at 180°F. Low-acid foods need 240 to 250°F under pressure, which is retort territory.
Hot-fill has two limits. It can't be used for carbonated drinks, because hot liquid won't hold CO2. And the package has to take the heat and the vacuum, which means glass, cans or heat-rated plastic.
Cold chain: skip the heat, keep it cold
Some drinks lose what makes them special when heated: fresh juice, some teas, anything sold on a just-made taste. These can be filled cold and kept refrigerated from the plant to the customer's fridge. Cold slows spoilage but stops nothing, so shelf life is shorter and every warm hour in a truck or on a dock counts against it.
High pressure processing extends that life. Sealed bottles go into a vessel of cold water at up to 87,000 psi, which inactivates most vegetative bacteria without heat. Pressure at these temperatures does not inactivate bacterial spores, so HPP drinks still ship and sell refrigerated. The package has to flex to pass the pressure along, so glass bottles and cans can't be used.
Side by side
| Tunnel | Hot-fill | Cold chain | |
|---|---|---|---|
| Carbonated? | Yes, up to the can's pressure limit. Still drinks too | Still drinks only | Either |
| Package | Cans and glass | Glass, cans or heat-rated plastic | Most packages; HPP needs flexible plastic |
| Heat on flavor | Moderate heat for many minutes | High heat, cooled soon after the hold | None |
| Storage | Room temperature | Room temperature | Refrigerated, start to finish |
| What drives cost | Tunnel time sets line speed | Heavier, heat-rated packaging | Cold freight, cold storage, shorter dating |
Which route fits your drink?
How Palate Pack runs it
Cans go through our tunnel, carbonated or still. Still drinks in glass are hot-filled. Each product runs to its own scheduled process from a process authority, and we run pH and Brix checks on every batch.
We'll tell you early if a drink is a poor fit for either line. A fresh-pressed juice that can't take heat belongs with a cold-chain or HPP producer, and it's better to know that before buying packaging.
FAQ
Will pasteurization change the taste?
Somewhat. Heat speeds up the chemical changes that happen slowly on a shelf: aromas can fade and the drink can taste less fresh. Run a heated sample before locking the recipe.
Can I use the same settings another brand uses?
No. The dose depends on your pH, sugar, juice content, package and what could grow in that mix. Two lemonades can need different processes.
Does HPP make a drink shelf-stable?
No. HPP products are distributed refrigerated because pressure leaves bacterial spores intact.
Can preservatives replace the kill step?
Sometimes. Soft drink makers commonly use potassium sorbate and sodium benzoate, and some processes are built around them. A process authority has to approve that route, and it changes your label.
Next: Guide 03, the process authority and your scheduled process.
Not sure which route your drink needs?
Tell us what it is, the package you want and where it will sell. We'll tell you which line it fits.
Start your projectSources
- Master Brewers Association of the Americas, Food Safety Bite No. 5: Pasteurization (2024). PU definition and formula.
- Jurado and Michalski, Why tunnel pasteurize new and emerging beverages?, Brewers Journal. Tunnel zones and PU range.
- NC State Extension, Processing acid and acidified foods. Hot fill at 180°F or above; steam capper or inversion.
- University of Georgia Extension, Preserving acidified foods using the hot-fill-hold process (C 1328-03). 180 to 200°F fill range.
- Kansas State Research and Extension, Hot-fill-hold process for acid and acidified foods (MF3671). Time and temperature minimums at pH 4.1 or below; retort temperatures; vacuum seal; preservatives.
- Ohio State University Extension, High pressure processing of foods (FST-FABE-1001). Pressure, spores, packaging and refrigerated distribution.
- Escarpment Laboratories, Pasteurization. PU figures for standard and alcohol-free beer, after Rachon and colleagues.
- BevSource, Beverage Preservation 101: tunnel pasteurization vs. hot filling. Carbonation limits and packages for each method.
- Farber, The science of exploding beer cans, Brewing Industry Guide. Can pressure and temperature.
- Messer, Liquid nitrogen dosing for beverage containers. Pressurizing still drinks.
- e-PG Pathshala, Thermal death time curves. Why hotter and shorter protects quality.
This guide is general education, not a process determination. Every product needs its own evaluation and scheduled process from a qualified process authority.