Yogurt is acidic and cultured, which protects it, but it's a refrigerated food and its shelf life ends three ways. Yeasts and molds, the usual spoilers of a cultured food, slowly grow in the cup; the cultures keep working, so it gets more sour; and whey separates on top. Warm handling speeds all three, so the cold chain from the cooler to the store matters as much as the recipe. In the example below, a Wisconsin yogurt maker's cups passed every test through day 28, and they say use by 21 days, a 25% margin. Below is what ends yogurt's shelf life, the study, storage, the date, and a free template.
The short version
- Yeast and mold are the spoilers to test for.
- Yogurt keeps getting more sour as the cultures work.
- Whey separation shows age and rough handling.
- Keep it cold from the cooler to the store.
- Run a real-time study with lab counts and leave a margin.
- Print a "Use by" date and "Keep refrigerated".
- TaroStack gives every batch its date from the shelf life you set. More below.
What ends its shelf life
| What ends it | What happens | What slows it |
|---|---|---|
| Yeast and mold | Counts climb; a swollen lid or spots | Clean filling; cold storage |
| Sourness | The cultures keep acidifying | Cold storage; a short date |
| Whey separation | Liquid pools on top | Gentle handling; stir instructions |
| Opening | Air and spoons bring in mold | "Eat within 7 days of opening" |
The yogurt's year is in yogurt business plan, and cups and lids in how to package yogurt for sale.
How it's stored
| Stored | In the example's tests | On the label |
|---|---|---|
| Sealed cup, refrigerated at 34 to 38°F | Passed every test through day 28 | Use by 21 days |
| Opened, refrigerated | Not part of the study | "Eat within 7 days of opening" |
| Left out warm | Not part of the study | "Keep refrigerated" |
The opened line is the maker's instruction, cautious on purpose.
An example: a shelf life study
Prairie Hollow Creamery, the made-up yogurt maker in Mount Horeb, Wisconsin, I use in these examples, kept cups of plain high-protein yogurt from one batch at 36°F, sent two to a lab at each pull and tasted two more:
| Test | Pass if | Day 0 | Day 7 | Day 14 | Day 21 | Day 28 | Day 35 |
|---|---|---|---|---|---|---|---|
| Yeast and mold, CFU per gram | at most 10 | 0 | 0 | 1 | 3 | 8 | 40 |
| Flavor score, 1 to 9 | at least 6 | 9 | 9 | 8 | 7 | 6 | 4 |
| Whey separation, 1 to 5 | at most 2 | 1 | 1 | 1 | 2 | 2 | 3 |
| All pass? | Pass | Pass | Pass | Pass | Pass | Fail |
Everything passed through day 28; at day 35 yeast and mold passed the limit and the flavor turned too sour. Taking a 25% margin off day 28 gives 21 days. How the pulls and margin are planned is in shelf life testing.
The date on the label
Yogurt carries a "Use by" date with "Keep refrigerated". In California, food made from July 1, 2026 that shows a date uses "BEST if Used by" for quality or "USE by" for safety, in sell by date law, and how to write the date is in best by date format.
Get the template
Download the yogurt shelf life study template. One sheet: the product, the lot tested, the day it was made, how it's stored and the margin to leave; then each test with its limit and the result at each pull. It marks each pull pass or fail, finds the last day everything passed, takes the margin off, and gives the shelf life for the label and the date for a batch made today. It's an ordinary Excel file with no macros, and it works in Google Sheets, LibreOffice and Numbers.
Where this stops working
Three-week yogurt moves fast. Four flavors, cases at a distributor and twenty stores, and a hot loading dock in July: someone has to date each batch and send the oldest out first, with enough days left for each store.
How TaroStack does it
TaroStack gives every batch its date from the shelf life you set, and sends the oldest out first.
Dates from the shelf life. Each cup of yogurt carries its shelf life in days, and each batch's lot gets its production date and the date that follows from it.
First-expired-first-out. Orders take the oldest lots first by default, and a distributor can be set to take only stock with enough days left.
What's coming up. A forecast shows what will expire unsold and what it costs, and anything thrown out is recorded with its reason, expired or spoiled, so waste shows by item.
| The job | Spreadsheet | In TaroStack |
|---|---|---|
| The date on a batch | Worked out by hand | From the shelf life, on the lot |
| Which batch goes out first | Dates on tape | First-expired-first-out |
| Stock with enough days for a distributor | Checked by hand | The customer's shelf-life rule |
| What expired last month | Not counted | Waste by reason |
Lots, dates, first-expired-first-out and the expiry forecast 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.