A shelf life study is a plan and a record: which product and lot you're testing, how it's stored, the days you'll pull samples, the tests at each pull with the limit each must meet, and the results. The shelf life is the last day every test passed, less a margin, and that becomes the best-by date on the label. The template below is for a real-time study, where samples are kept the way customers will keep them and tested over the full life, which is slower than an accelerated study but needs no modeling to believe. In the example below, a lilikoi butter passes every test through day 56 and fails on taste at day 70; with a 10% margin, the label says 50 days. Below is how to plan the study, the example filled in, how to set the date, and a free template.
The short version
- Test one lot, made the usual way, stored the way customers will store it.
- Choose pull days that cover the life you hope for, and a little beyond.
- Test what fails first for your product: taste, texture, color, pH, water activity, microbes.
- Write each test's limit before you start, as "at least" or "at most".
- The shelf life is the last day every test passed; take a margin off it.
- Keep the study with the product's records, and repeat it when the recipe or packaging changes.
- TaroStack puts the best-by date on every lot from the item's shelf life and sends the oldest out first. More below.
Planning the study
| Decide | In the example |
|---|---|
| Product and package | Lilikoi butter, 8 oz sealed jar |
| Lot | One lot, LB-0901, made September 1 the usual way |
| Storage | Refrigerated, 34 to 38°F, as customers will keep it |
| Pull days | Day 0, 14, 28, 42, 56 and 70 |
| Samples | Enough jars for every pull, plus spares |
| Tests | Taste, texture and color scores; pH; yeast and mold by a lab |
| Limits | Scores at least 6 of 9; pH at most 4.2; yeast and mold at most 100 CFU/g |
| Margin | 10% off the last passing day |
The tests are the ones that tell you when this product stops being good: a dry snack fails on texture and moisture, a sauce on flavor and pH, a refrigerated spread on taste and microbes. The limits in the example are its own, set with its lab. Whether your product needs a process authority's review, and what limits apply to an acidified food, are questions for process authority letter and pH testing for acidified foods. How real-time and accelerated studies differ is in shelf life testing.
The results
| Test | Limit | Day 0 | Day 14 | Day 28 | Day 42 | Day 56 | Day 70 |
|---|---|---|---|---|---|---|---|
| Taste, 1 to 9 | At least 6 | 8 | 8 | 7 | 7 | 6 | 5 |
| Texture, 1 to 9 | At least 6 | 8 | 8 | 8 | 7 | 7 | 6 |
| Color, 1 to 9 | At least 6 | 9 | 9 | 8 | 8 | 7 | 6 |
| pH | At most 4.2 | 3.6 | 3.6 | 3.7 | 3.7 | 3.7 | 3.8 |
| Yeast and mold, CFU/g | At most 100 | 10 | 10 | 10 | 20 | 40 | 150 |
| All tests pass? | Pass | Pass | Pass | Pass | Pass | Fail |
Day 70 fails on taste and on yeast and mold. Day 56 is the last day everything passed.
Setting the date
| Step | Result |
|---|---|
| Last day everything passed | 56 days |
| Less a 10% margin | 50 days |
| Best-by date | Made on + 50 days |
The margin covers what the study can't: a warm delivery van, a fridge door opened all day, a lot that's a little different. Some makers round down to a week, here 49 days, so the date is easy to work out. Then write the result into the product's records with the study attached, and put it on the label in the format your customers read; how is in best by date format.
When to run it again
Repeat the study when the recipe changes, when the packaging changes, when the process changes (a new cooker, a new filling temperature), and when a buyer asks for a longer date than you have evidence for. A study from three recipe versions ago doesn't support today's label.
Get the template
Download the shelf life study template. Type the product, lot, storage and margin, then each test with its rule and limit and the result at each pull; it marks each pull Pass or Fail, finds the last passing day, takes the margin off, and gives the shelf life and a best-by 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
The study sets the number; the kitchen has to use it on every lot. A best-by date worked out by hand on each batch is a date someone gets wrong, a lot made on a Friday ends up dated from Monday, and the shop that asked for 60% of the shelf life left on delivery gets jars with a third. The study is in a folder; the dates are on stickers.
How TaroStack does it
TaroStack turns the study's number into a date on every lot, and keeps the lots in order.
Dates from the item, on every lot. Each item carries its shelf life, and every batch goes into a lot with its production and best-by dates. Lot labels print with the code and the date, and a GS1-128 barcode carrying the use-by date and lot when the item has a GTIN.
Results kept with the lot. Custom fields can sit on batch records and on lots, so a study's pull results, or a release check, are recorded where the lot is. A batch can sit on hold until it's checked.
And the dates, used. Stock goes out first-expired-first-out by default, a customer's days-of-shelf-life rule is kept with the customer and applied when an order is picked, and a forecast shows what will expire unsold and what it's worth. Lots close to their date show in your alerts.
| The job | Folder and stickers | In TaroStack |
|---|---|---|
| Best-by on each lot | Worked out by hand | From the item's shelf life |
| The study's results | In a folder | Fields on the lot or batch record |
| A shop's shelf-life rule | Checked by eye | Applied at picking |
| What's about to expire | A look round | Alerts and the expiry forecast |
Lots and expiry, lot labels, custom fields on batches and lots, and first-expired-first-out 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.