Food date labels explained
title: Food Date Labels Explained: Best Before, Use By, Sell By — What They Really Mean
Walk into any kitchen and you’ll see them — stamped dates on milk cartons, canned beans, pasta boxes, and deli meat. Yet most consumers can’t tell you whether “Best Before” means the food is unsafe, or whether “Sell By” is meant for them or the store. The confusion isn’t trivial: according to the USDA and WRAP, an estimated 20% of consumer food waste — roughly 90 billion pounds annually in the US alone — stems from misunderstanding date labels. That’s food thrown away that is still perfectly safe to eat. From an industrial food science perspective, date labels represent the intersection of microbiology, chemistry, and sensory science. A date printed on a package isn’t an arbitrary guess — it’s the result of shelf-life studies that involve microbial challenge testing, accelerated aging protocols, and trained sensory panels. Understanding what these dates actually encode can save you money, reduce waste, and help you distinguish between a quality decline and a genuine safety hazard.
Table of Contents Toggle
The Three Main Types of Food Date Labels
Best Before / Best If Used By Use By Sell By
Quality vs. Safety: The Critical Distinction The Science Behind Date Determination: How Shelf-Life Testing Works
1. Microbial Challenge Testing 2. Accelerated Shelf-Life Testing (ASLT) 3. Sensory Evaluation Panels
Date Labels by Food Category: What the Dates Really Mean
Dairy Products Meat and Poultry Canned Goods Dry Goods (Pasta, Rice, Flour, Cereal) Frozen Foods
The Spoilage Cascade: What Happens After the Date Global Comparison: Date Label Regulations Worldwide How to Assess Food Safety: The Limits of Sensory Tests The Future of Food Dating: Beyond Printed Dates Practical Takeaways Scientific Literature References Scientific Literature References
The Three Main Types of Food Date Labels
Despite widespread belief, most food date labels in the United States are not federally regulated (infant formula is the sole exception). The FDA and USDA provide guidance, but manufacturers largely determine their own dating systems. Here’s what the three most common labels actually mean:
Best Before / Best If Used By
This is a quality indicator, not a safety indicator. A “Best Before” date tells you when the manufacturer believes the product will be at its peak flavor, texture, and nutritional quality. After this date, the food may experience:
Gradual flavor degradation (volatile aroma compound loss) Texture changes (starch retrogradation in baked goods, moisture migration in dry products) Minor vitamin degradation (especially light-sensitive vitamins like riboflavin and vitamin C) Color fading (pigment oxidation in packaged foods)
Critically, none of these changes make the food unsafe. The FDA explicitly states: “With the exception of infant formula, if the date passes during home storage, a product should still be safe and wholesome if handled properly until spoilage is evident.” This applies to canned goods, dry pasta, cereals, chips, crackers, and shelf-stable products — which can often be consumed months or even years after their Best Before date with only minor quality degradation.
Use By
This IS a safety indicator. The “Use By” date is the last date recommended for the use of the product while at peak safety. It applies to highly perishable foods where spoilage organisms can reach dangerous levels relatively quickly. If a food has passed its Use By date, the official recommendation is to discard it — even if it looks and smells fine — because pathogenic bacteria (Salmonella, Listeria monocytogenes, pathogenic E. coli) do not always produce detectable odors or visible changes. Use By dates are most commonly found on:
Fresh meat and poultry Fresh fish and seafood Deli meats and prepared salads Soft cheeses (especially those made from unpasteurized milk) Fresh dairy products (milk, cream, yogurt) Chilled ready-to-eat meals Infant formula (the only federally mandated date label)
Sell By
This is for the retailer, not the consumer. The “Sell By” date tells the store how long to display the product for inventory management purposes. It assumes the consumer will continue to store and use the product at home for a reasonable period after purchase. The FDA advises that consumers should buy the product before the Sell By date, but the product is still safe to consume after that date — typically for several days (for refrigerated items) to much longer (for shelf-stable goods). A critical industrial insight: Supermarkets pull products from shelves at the Sell By date not because they’ve spoiled, but because they need to maintain inventory turnover and quality perception. Much of this pulled food is still perfectly edible — which is why food rescue organizations can legally collect and distribute it.
Quality vs. Safety: The Critical Distinction
This is the single most important concept in food date label literacy. Let’s break it down in industrial food science terms:
Aspect Quality Decline (Best Before) Safety Hazard (Use By)
Cause Physical/chemical changes, non-pathogenic spoilage Pathogenic microbial growth or toxin production
Detectable? Usually — stale taste, texture change, color fade Often NOT detectable by smell or sight
Timeframe Days to years depending on product Hours to days for perishables at abuse temperature
Temperature sensitivity Accelerated but not catastrophic Highly temperature-dependent (exponential bacterial growth)
Reversible? Some changes can be reversed (e.g., refreshing stale bread by reheating) Never — bacterial toxins cannot be “cooked out”
The takeaway: Best Before is about “will it taste good?” — Use By is about “will it make me sick?” Confusing the two leads to both unnecessary food waste (throwing out safe food that’s past Best Before) and potential health risks (consuming food past Use By because it “looks fine”).
The Science Behind Date Determination: How Shelf-Life Testing Works
Food manufacturers don’t guess at shelf-life. They conduct rigorous testing programs — collectively known as shelf-life studies — to determine the appropriate date to print on each product. There are three primary methodologies:
1. Microbial Challenge Testing
This is the gold standard for determining safety-based dating. The food product is deliberately inoculated with known quantities of target pathogens — typically Listeria monocytogenes , Salmonella spp., pathogenic E. coli , or Clostridium botulinum — and stored under controlled conditions. At regular intervals, samples are tested for pathogen survival and growth using selective agar plating, PCR, or enrichment culture methods. The key metric: lag phase duration — the time it takes for the microbial population to exit its adaptive period and begin exponential growth. For refrigerated products, challenge tests are run at multiple temperatures (typically 4°C, 7°C, and 10°C) because research shows that average home refrigerator temperatures range from 4°C to 7°C, significantly higher than the ideal 0–2°C. The date is set at the point where pathogens would reach 1 log CFU/g growth under realistic worst-case conditions.
2. Accelerated Shelf-Life Testing (ASLT)
For quality-based dating on shelf-stable products (where microbial safety isn’t the limiting factor), manufacturers use accelerated shelf-life testing. Products are stored at elevated temperatures (typically 30°C, 37°C, and 45°C) and humidity levels to accelerate chemical degradation reactions. The Q10 principle — that reaction rates approximately double for every 10°C temperature increase — allows scientists to project the shelf-life at normal storage conditions from high-temperature data. For example, if a cracker’s texture becomes unacceptably stale after 12 weeks at 37°C, and the Q10 for starch retrogradation in that matrix is ~2, the projected shelf-life at 20°C (room temperature) would be approximately 12 × 2^(1.7) ≈ 36–40 weeks. The manufacturer would then set a Best Before date of around 8–9 months, applying a safety margin.
3. Sensory Evaluation Panels
Even with all the instrumental analysis — GC-MS for volatile compounds, texture analyzers, color spectrophotometers — the final arbiter of quality is human perception. Trained sensory panels (typically 8–12 panelists) evaluate products at regular intervals throughout the projected shelf-life, scoring attributes like appearance, aroma, flavor, texture, and overall acceptability on standardized scales. The “end of shelf-life” is defined as the point where a statistically significant percentage of panelists rate the product below the “acceptable” threshold. This is why “Best Before” dates are conservative: manufacturers need to guarantee that even the most sensitive consumer won’t detect quality degradation before that date. Well-calibrated sensory panels ensure this.
Date Labels by Food Category: What the Dates Really Mean
Dairy Products
Milk typically carries a “Sell By” or “Use By” date 10–21 days after pasteurization, depending on pasteurization method (HTST at 72°C for 15 seconds vs. UHT at 135°C for 2–5 seconds). UHT milk in aseptic packaging can last 6–9 months unopened without refrigeration. Pasteurized milk stored at ≤4°C is typically safe for 5–7 days after the printed date if it shows no off-odors, though psychrotrophic bacteria like Pseudomonas fluorescens — which can grow at refrigeration temperatures — will eventually produce lipolytic and proteolytic enzymes that create bitter, soapy, or fruity off-flavors.
Meat and Poultry
Fresh meat carries a “Use By” date based on the growth rate of spoilage organisms (primarily Pseudomonas spp., Brochothrix thermosphacta , and lactic acid bacteria) under aerobic refrigeration. Ground meat has a shorter shelf-life than whole cuts because grinding distributes surface bacteria throughout the product matrix, dramatically increasing the surface area available for microbial growth. Ground beef, even well-refrigerated, should be consumed or frozen within 1–2 days of purchase, regardless of the printed date. The industrial standard for ground beef at retail is a 2–5 day display life from packaging at 0–2°C.
Canned Goods
Canned foods are perhaps the most misunderstood category. Properly processed and sealed cans are commercially sterile — all spoilage organisms and their spores have been killed. The “Best Before” date on canned goods (typically 1–5 years from manufacture) refers exclusively to quality factors : color changes, texture softening, and gradual vitamin degradation (especially thiamine and vitamin C). From a safety standpoint, commercially canned food at the correct pH and water activity can remain safe to eat for decades — as long as the can integrity is maintained (no rust, dents at seams, bulging, or leakage).
Dry Goods (Pasta, Rice, Flour, Cereal)
With water activity typically below 0.60, dry goods cannot support microbial growth. The “Best Before” date reflects lipid oxidation in whole-grain products (brown rice, whole wheat flour — where rancidity develops over months due to unsaturated fatty acids in the germ) and moisture migration that can cause textural changes. White rice and dried pasta, both with aw ~0.40–0.50, are effectively non-perishable for years when stored in sealed containers away from moisture and pests.
Frozen Foods
Frozen foods carry a “Best Before” date because freezing doesn’t kill all microorganisms — it simply suspends their metabolic activity. At commercial freezing temperatures (-18°C or below), enzymatic activity is drastically slowed but not completely halted. Over months, freezer burn (sublimation of water from the food surface, causing dehydration and lipid oxidation) degrades texture and flavor, but the food remains safe. The USDA states that frozen food stored continuously at 0°F (-18°C) is safe indefinitely — the date is purely a quality recommendation.
The Spoilage Cascade: What Happens After the Date
Food spoilage is not a binary event — it’s a cascade. Understanding this cascade is key to making informed decisions about post-date food:
Lag Phase (hours to days) — Spoilage organisms are present but not yet multiplying significantly. The food appears, smells, and tastes normal. For refrigerated products at correct temperature, this can extend days beyond the Use By date. Early Growth Phase — Bacterial populations reach 10³–10⁴ CFU/g. Subtle changes begin: slight off-odors (from volatile organic compounds like dimethyl sulfide, trimethylamine, ammonia), minor texture changes (proteolysis softening muscle tissue). The food may still appear acceptable to consumers. Mid-Spoilage Phase — Populations reach 10⁵–10⁶ CFU/g. Definite spoilage indicators: slime formation (extracellular polysaccharides from Pseudomonas), discoloration (myoglobin oxidation in meat, chlorophyll degradation in vegetables), pronounced off-odors, gas production (blown packs from heterofermentative LAB or Clostridium spp.). Advanced Spoilage — Populations exceed 10⁷ CFU/g. The food is visibly, olfactorily, and texturally unacceptable. Some spoilage organisms at this density can produce biogenic amines (histamine, cadaverine, putrescine) that may cause adverse reactions, though these are distinct from pathogenic infection.
The critical insight: Spoilage organisms are generally not the ones that make you sick. The bacteria that cause obvious spoilage (Pseudomonas, Shewanella, Lactobacillus) are different from the pathogenic bacteria that cause foodborne illness (Salmonella, Listeria, pathogenic E. coli). You can smell spoilage — you cannot smell Salmonella. This is both comforting (spoiled food usually announces itself) and alarming (pathogen-contaminated food can be undetectable).
Global Comparison: Date Label Regulations Worldwide
Date labeling systems vary dramatically by country, adding to consumer confusion — especially for imported foods:
Region System Safety Label Quality Label Regulation
United States Voluntary (except infant formula) “Use By” (recommended) “Best If Used By” FDA/USDA guidance, not mandate
European Union Mandatory dual system “Use By” (date de durabilité) “Best Before” (date de durabilité minimale) Regulation (EU) No 1169/2011
United Kingdom Similar to EU “Use By” “Best Before” UK Food Information Regulations 2014
Canada Mandatory on prepackaged “Expiration Date” (for specific categories) “Best Before” Safe Food for Canadians Regulations
Australia / NZ Mandatory for “Use By” “Best Before” FSANZ Standard 1.2.5
Japan Dual labels “消費期限” (Shōhi Kigen — consume by) “賞味期限” (Shōmi Kigen — best taste by) Food Labeling Act
China Single label system “保质期” (bǎo zhì qī — shelf-life) (Combined — indicates end of guaranteed quality period) GB 7718-2011
The EU’s mandatory dual-label system is widely regarded as the gold standard for clarity. By legally distinguishing between safety (“Use By”) and quality (“Best Before”), it empowers consumers to make informed decisions. The US system, by contrast, relies on voluntary industry adoption of standardized wording — a situation the FDA has been working to improve, with mixed results.
How to Assess Food Safety: The Limits of Sensory Tests
Many consumers rely on the “sniff test” to determine if food is still good. From an industrial food science perspective, this is a useful but incomplete tool. Here’s what sensory evaluation can and cannot tell you:
Test What It Detects What It CANNOT Detect
Smell Volatile spoilage compounds (amines, sulfides, short-chain fatty acids, ketones) from spoilage bacteria Pathogenic bacteria (Salmonella, Listeria, pathogenic E. coli), norovirus, hepatitis A virus, botulinum toxin (odorless and tasteless)
Visual Mold colonies, discoloration (oxidation/enzymatic browning), slime, gas production (blown packaging), liquid separation Bacterial contamination below 10⁶ CFU/g, early-stage mold (hyphae invisible to naked eye), mycotoxins in apparently normal grains
Touch/Texture Slime formation, excessive softening, unusual stickiness Pathogen presence, histamine in fish (scombrotoxin has no impact on texture)
The industrial rule of thumb: If a high-risk food (meat, poultry, seafood, dairy, prepared meals) is past its Use By date, discard it regardless of sensory evaluation. For low-risk foods past Best Before (canned goods, dry goods, frozen foods, high-acid condiments), sensory evaluation is a reasonable screening method — but it should be combined with knowledge of the specific food’s spoilage mechanisms.
The Future of Food Dating: Beyond Printed Dates
The printed date label is a crude tool — it assumes constant temperature storage and identical product handling from factory to consumer. In reality, a milk carton that spent 2 hours at 25°C during transport has a very different spoilage trajectory than one kept continuously at 2°C, even though both carry the same printed date. Several emerging technologies aim to solve this:
Time-Temperature Indicators (TTIs): These labels change color based on cumulative time-temperature exposure. They use enzymatic or polymerization reactions that proceed at rates proportional to food spoilage kinetics, providing a dynamic, product-specific freshness indicator rather than a fixed date. Commercial TTIs like 3M MonitorMark and VITSAB are already used in pharmaceutical and some food cold chains. Intelligent Packaging with Gas Sensors: Embedded sensors detect volatile spoilage markers — CO₂ (microbial respiration), amines (protein degradation), ethylene (fruit ripening) — and trigger a visible color change when these exceed threshold levels. Researchers at MIT and the University of Strathclyde have demonstrated pH-sensitive film sensors that change color in the presence of ammonia released by spoiling meat. Blockchain Traceability: By recording every temperature data point from farm to fork on an immutable distributed ledger, blockchain enables true “dynamic dating” — the printed date adjusts based on the actual handling history of that specific package. IBM Food Trust and Walmart’s blockchain pilot have demonstrated this in commercial settings. QR-Enabled Dynamic Dates: A QR code on the package links to a real-time database that provides the consumer with a freshness assessment based on the product lot’s microbiological test data, storage history, and current date. Danish startup Too Good To Go has prototyped this concept for reducing retail food waste.
Practical Takeaways
Best Before = Quality. Past date? Check it. Smells fine, looks normal, tastes okay → it’s probably fine. (Exception: high-risk foods with Use By dates should be respected.) Use By = Safety. Past date? Don’t risk it. Pathogens are undetectable by senses. Discard. Sell By = Retail inventory. Ignore it. Buy before it if you want maximum home shelf-life, but it’s not a safety indicator. Canned and dry goods: The date is highly conservative. Properly stored cans and dry goods can last years beyond their Best Before dates. Frozen food: Safe indefinitely at proper temperatures (-18°C or below). Date is quality only. Temperature is everything: A product stored at 2°C will last dramatically longer than the same product stored at 7°C — even with the same printed date. Your refrigerator temperature matters more than you think.
The printed date on your food is not a switch that flips at midnight — it’s a cautious estimate based on conservative assumptions about storage conditions. By understanding the science behind these dates, you can make smarter decisions: wasting less safe food, while avoiding the genuinely hazardous products that could make you sick. For a deeper understanding of the spoilage mechanisms that dates are designed to predict, see our guides on What Makes Food Go Bad, the critical difference between microbial and chemical spoilage, and the foundational role of water activity (aw) in food stability.
Scientific Literature References
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