pH Testing for Acidified Foods: Meters, Method, Records

For an acidified food, a sauce, pickle or salsa made safe by adding acid, pH testing is how you show each batch reached the pH your scheduled process requires, which must be 4.6 or lower. Use a pH meter, not strips, unless the product's pH is 4.0 or below, because FDA's method only allows color strips at that level. Calibrate the meter with a pH 4.0 buffer before you test, blend the sample, test it between 20 °C and 30 °C, ideally 25 °C, and record the reading, the temperature, the meter check and who did it, for every batch. Keep those records three years. In the example below, two hot sauce batches read well under their limit and a third reads over it, is held, re-acidified as the process allows and released. Below is the meter, the method, the records, what to do when a reading is high, and a free pH log.

The short version

• The scheduled process sets your pH limit; it must be 4.6 or lower, and is often set below that.
• Use a pH meter; strips are only allowed when the pH is 4.0 or lower.
• Choose a meter that reads to 0.01, with temperature compensation and a probe that suits your product.
• Calibrate before testing with a pH 4.0 buffer, and check it with a second buffer.
• Blend a sample to a paste and test at 20 °C to 30 °C.
• Record every batch: reading, temperature, meter check, initials, and what you did if it was over.
• TaroStack flags a reading over the limit as the batch is recorded and holds the batch. More below.

Meter or strips

FDA's method for acidified foods is a potentiometric one, a pH meter with a glass electrode; color indicators, including paper strips, may be used instead only when the pH is 4.0 or lower (21 CFR 114.90). A hot sauce with a limit of 4.2 is above that, so it needs a meter.

The method

The method describes standardizing with a pH 4.0 buffer, testing between 20 °C and 30 °C with 25 °C the optimum, and notes that most meters are accurate to about 0.1 pH unit (21 CFR 114.90). That accuracy is one reason a process authority sets a limit with a margin below 4.6. How a process authority sets the limit and the rest of the scheduled process is in process authority letter.

A pH log, worked through

Windward Roots, the made-up taro business I use in these examples, makes a chili pepper water hot sauce whose scheduled process, in this example, sets a finished pH of 4.2 or lower:

The October 8 batch used a new supplier's peppers. It was held, re-acidified as the scheduled process allows, retested and released, and the record shows all of it. FDA requires the finished equilibrium pH of 4.6 or lower to be reached and kept, in accordance with the scheduled process (21 CFR 114.80); what your process says to do with a batch over its limit is what you follow. How the sauce itself is costed and planned is in hot sauce business plan.

When a reading is high

Acidified food processors keep processing, deviation and pH records for three years (21 CFR 108.25). How to run a hold and a release is in hold and release procedure. This is general information, not legal advice.

Get the pH log

Download the pH log. The Calibration sheet records each meter check and flags a buffer reading more than 0.05 off; the Batches sheet records each batch's reading against its limit, marks it pass or over in red, flags a sample tested outside 20 °C to 30 °C, and has columns for the action, the retest and who released it. It's an ordinary Excel file with no macros, and it works in Google Sheets, LibreOffice and Numbers.

Where this stops working

The log is a sheet by the meter. On a busy day, the reading is written on a scrap and copied later, or not at all; the limit isn't on the sheet, so 4.31 looks fine to someone who doesn't know the process says 4.2; and the over-limit batch goes into the same rack as the others, because nothing separates it.

How TaroStack does it

TaroStack puts the limit on the batch, flags a reading over it the moment it's recorded, and keeps the held batch apart.

The limit, on every batch. Batch record forms are filled in as the batch is recorded, with your own fields: the pH reading, the sample temperature, the meter check and initials. Number fields carry units and limits, so a pH over your process's limit is flagged when it's entered, and the flag is marked reviewed with what was done about it.

The held batch, apart. A batch waiting on a retest can sit on hold, apart from stock you can sell, until someone releases it. The recipe is versioned, so a change is recorded as a new version, the cue to take it back to your process authority.

And the records keep. Every batch is a permanent record with its lot, its readings, its ingredient lots and who made it, searchable long past three years, and one report walks any lot to the customers who got it. TaroStack keeps the records; it doesn't write your scheduled process.

Lots, holds, recalls, recipes with versions and batch records with limits are on every plan, from $49 a month. The first 30 days are free, with no credit card. If you'd like a hand setting up, ask, and we'll do it with you.

Questions people also ask

Can I use pH strips for hot sauce?

Only if the sauce's pH is 4.0 or lower. FDA's method allows color indicators at that level; above it, use a pH meter.

What pH meter should I use for food?

One that reads to 0.01 pH, compensates for temperature, takes a two-point calibration, and has a probe suited to your product, such as a spear tip for thick sauces.

How do I calibrate a pH meter for acidified foods?

Before testing, standardize it with a pH 4.0 buffer near 25 °C, then check it against a second buffer. Record the check with the batch's readings.

How long do I keep pH records?

Acidified food processors keep processing, deviation and pH records for three years under FDA's rules.