Ready-to-drink coffee and concentrates

Why black coffee is harder to bottle than fruit juice

Sourced

Food regulators sort sealed foods by acidity, because acidity decides which organisms can grow in them. United States regulations define a low-acid food as one with a finished pH above 4.6 and a high water activity, and an acid food as one with a natural pH of 4.6 or below. Low-acid foods sealed in airtight containers fall under rules written for canning, which require a process scientifically shown to destroy the organisms that matter.

Coffee tastes sharp, and it is still on the low-acid side of that line. One study of cold brew measured a starting pH of 5.88; another recorded coffees between 4.27 and 5.92. Most black coffee therefore sits above 4.6, which is why a shelf-stable coffee drink cannot simply be bottled like lemonade. Adding milk moves it further in the same direction.

The regulations themselves do not mention coffee. Applying their definitions to it is our reading of them, and how any particular product is classified is a matter between its maker and the regulator.

Three ways a coffee drink is made to keep

Sourced

Sterilised and sealed, kept at room temperature

The drink is heated enough to be commercially sterile, either in its sealed container or before filling. In aseptic packaging the regulations describe a sterilised, cooled product filled into pre-sterilised containers and sealed in an atmosphere free of microorganisms. This is what allows a can or carton to be stored warm until opened.

Pressure-treated, kept cold

High-pressure processing uses pressure in place of heat. In one study, cold brew treated at 600 megapascals for three minutes showed a reduction of more than a million-fold in three added pathogens, with none detectable for at least 90 days. The authors note that they did not examine spore-forming bacteria, which is why such products are normally sold chilled.

Simply brewed and chilled

Fresh cold brew from a café tap or a small producer may have had no treatment beyond refrigeration. It is a perishable food with a short life, and its safety rests on clean equipment and a cold chain.

What this means for cold brew made at home

Sourced

The research is more reassuring than alarming, with conditions. In a 42-day study of bottled cold- and hot-brewed coffee kept refrigerated, no bacterial growth was detected at any point; the authors concluded that shelf life was limited by flavour going stale and not by microbes, and attributed that to the scarcity of nutrients in black coffee, its acidity and compounds in the coffee itself. That coffee was brewed and bottled under laboratory hygiene.

Two other findings set the limits. When researchers deliberately added E. coli, Listeria and Salmonella to cold brew, the bacteria did not multiply, but they were still detectable after 60 days in the fridge: coffee does not grow these organisms, and it does not reliably kill them either. And when a German food-control laboratory tested commercial cold brews, two samples, 9 per cent of them, carried a raised microbial load: one of spoilage organisms and one of presumptive Bacillus cereus, in a cold brew that had been stored for five days.

The practical reading is that black cold brew is a low-risk food made risky by what touches it. Clean the vessel and filter properly, keep the brew cold from start to finish, and do not top up an old batch with a new one. Adding milk, cream or sugar removes most of the protection, so add them to the glass and not the jug. A university food-safety centre that has run this kind of trial gives households the same advice in plainer words: wash your hands and everything the coffee touches, and keep the brew in the fridge. In its trials the organisms it added never grew, but most took nine to twelve days to die off and Bacillus cereus lasted more than thirty, so a brew contaminated on the day it was made stays contaminated.

The only official figure read for this page is a rule for businesses, not households. Wisconsin's food regulator treats cold brew made without a heat step as a food that needs temperature control: a café must brew, hold and serve it at 41°F (5°C) or below and date-mark it for no more than seven days. It also limits cold brew sealed in a keg, or under nitrogen, to 48 hours without an approved safety plan, because a sealed, oxygen-free container is where botulism becomes a concern.

That is a ceiling set for trained staff with inspected equipment, and it is reasonable to treat it as a ceiling at home too, not a target. Makers of home brewers suggest their own figures, which are advice about flavour, and flavour is in any case the first thing to go.

What a concentrate is, on a label and in a recipe

Sourced

In everyday use a concentrate is any coffee made strong enough to need diluting. Cold brew concentrate is steeped with a high proportion of coffee; others are brewed hot and reduced or brewed under pressure. They are not interchangeable in flavour, and the word says nothing about how strong a given bottle is.

European law is more precise about a related product. The directive on coffee extracts defines liquid coffee extract as a product obtained from roasted coffee using only water, containing between 15 and 55 per cent coffee-based dry matter. It may be called concentrated only above 25 per cent, its label must state the minimum dry-matter content, and any sugar, which is capped at 12 per cent, must be named beside the product name. Those figures describe industrial extracts. A home cold brew concentrate is far more dilute than that and is not what the directive is about.

For buying, the useful consequence is that a regulated extract tells you how concentrated it is. A bottle that only says concentrate and gives a dilution suggestion is asking you to trust the suggestion.

Diluting a concentrate without guessing

CoffeeHQ explanation

1. Start from the maker's ratio. It is the only information about that bottle you have. Mix one small glass at the stated dilution before changing anything.
2. Change the water, not the concentrate. If it is too strong, add water to the same measure of concentrate; if too weak, use less water next time. Moving one quantity makes the next glass predictable.
3. Count ice and milk as dilution. Ice melts into the drink and milk replaces water. A concentrate diluted correctly and then poured over ice ends up weaker than intended, so dilute a little less when either is going in.
4. Judge strength and flavour separately. Dilution changes how strong the drink is and nothing else. If a concentrate tastes harsh or flat at every dilution, water will not fix it.

The cold brew calculator does the arithmetic for a target glass size and strength.

Caffeine, sugar and what the label owes you

Sourced

Caffeine in bottled coffee varies with the coffee, the recipe and above all the size of the container, and many products do not state it. European labelling law is part of the reason: the rule that requires a high-caffeine warning on drinks above 150 milligrams per litre specifically exempts drinks based on coffee or tea whose name includes the word. A canned coffee can exceed that level without saying so.

Sugar is the larger difference between products. Black bottled coffee has almost none, and sweetened milk coffees can contain a great deal; the nutrition panel is the only reliable guide.

Neighbouring products it is confused with

CoffeeHQ explanation

• Instant coffee — The same kind of extract taken further: the liquid is dried to a powder or granules of at least 95 per cent coffee solids, which keeps without refrigeration because there is no water left in it.
• Nitro cold brew — Cold brew with nitrogen dissolved in it for texture. The gas changes how it feels to drink and does nothing to preserve it; from a tap it is a fresh, perishable product, and a sealed keg is the case food regulators watch most closely.
• Iced coffee — Coffee brewed hot and then chilled. Bottled products labelled either way may be made by either route, and the label is not always a description of the method.

What to do next

• How to make cold brew — The method itself: proportions, steeping time and how to keep the equipment clean.
• Cold-brew batch and dilution calculator — Works out how much water a concentrate needs for the glass and strength you want.
• Caffeine estimator — For a rough sense of what a serving contributes when the bottle does not say.
• Instant coffee explained — The dried form of the same extract, and how it is made.