The shelf life on a label is given for one temperature: a product marked eight days at 4 °C is calculated on the assumption that it spends those eight days at 4 °C. If part of the chain ran at 8 °C, the days left shrink, and by roughly how much can be estimated with the Q10 coefficient.
According to USDA Agriculture Handbook 66, the rate of biological reactions rises 2 to 3 times for every 10 °C, and the typical Q10 for fruit and vegetables between 0 and 10 °C is 2.5 to 4.0. The rate ratio is Q10 raised to the power of the temperature difference divided by ten. If the product travelled at 8 °C instead of 4 °C, the difference is 4 degrees and the exponent 0.4:
| Q10 | Spoilage rate | Eight-day life becomes |
|---|---|---|
| 2.5 | 1.44 times | about 5.5 days |
| 3 | 1.55 times | about 5.2 days |
| 4 | 1.74 times | about 4.6 days |
This calculation does not replace laboratory work: Q10 varies with the product, the dominant spoilage organism and the packaging, the handbook itself notes that Q10 changes with temperature, and a firm shelf life needs a microbiological study. Most decisions in the field, though, call for a ranking: which batch ships first, which goes to markdown early, whether a load that travelled warm is accepted. That needs a temperature record along the route; without one there is no estimate.
