The Spoilage Index.
Did you know every food has its own "spoilage smell" you can actually measure? My sensor sniffs the gases food gives off as it goes bad. The line going DOWN means more bad-food gases. Once it crosses the red dotted line, the alarm goes off. These are real numbers from my own kitchen experiments. Not from a textbook.
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Cooked Rice (Basmati, 100g)
Spoiled24h sealed jar · room temp 24°C · MQ4
39.5 Fresh kΩ6.7 Spoiled kΩ83% % drop -
Milk (whole, 2% fat)
Spoiled48h sealed glass · room temp 23°C · MQ4
30.0 Fresh kΩ8.4 Spoiled kΩ72% % drop -
Sourdough Bread (21d past Best By)
Spoiled6h test · room temp · MQ4
28.0 Fresh kΩ9.1 Spoiled kΩ67% % drop -
Strawberries (vinegar-washed)
Stable7-day fridge test · 4°C · MQ4
24.8 Fresh kΩ23.5 Spoiled kΩ5% % drop -
Yogurt (plain, 1wk past Best By)
Stable12h sealed cup · fridge · MQ4
27.0 Fresh kΩ22.8 Spoiled kΩ16% % drop -
Bananas (countertop, ripening)
Spoiled5-day natural ripening · MQ4
26.5 Fresh kΩ7.2 Spoiled kΩ73% % drop
What each food puffs out as it goes bad
I read a bunch of food science papers, and then I checked the actual smells with my sensor. Turns out each kind of food has its own "fingerprint" of gases, kind of like every food has its own bad-breath. Here's what I found:
| Food | Main spoilage gases | When release starts | Fresh → spoiled kΩ |
|---|---|---|---|
| Cooked rice & pasta | EthanolAcetaldehydeDiacetyl | 6–18 hours sealed | 39.5 → 6.7 kΩ |
| Milk & dairy | Lactic acid VOCsAcetone | 12–24 hours sealed | 30.0 → 8.4 kΩ |
| Bread & baked goods | EthanolMold VOCs (1-octen-3-ol) | 1–6 hours past visible mold | 28.0 → 9.1 kΩ |
| Strawberries & berries | Ethyl acetateEthanol | 4–12 hours unwashed | 24.8 → 23.5 kΩ (vinegar-washed: stable) |
| Yogurt & curd | AcetoneDiacetyl | 24–72 hours past date in fridge | 27.0 → 22.8 kΩ (stable) |
| Bananas (ripening) | EthyleneEsters | 24–72 hours countertop | 26.5 → 7.2 kΩ |