Pasteurization is a heat-treatment process that destroys pathogenic microorganisms in food and beverages (especially milk, juice, beer, wine, and eggs) while preserving flavor and nutritional value as much as possible.
1. History
- Developed by Louis Pasteur and Claude Bernard in 1862–1864
- Originally created to prevent wine and beer from souring
- First applied to milk in the late 1800s to reduce tuberculosis and other milk-borne illnesses
2. Purpose of Pasteurization
- Kill or inactivate pathogenic bacteria (Salmonella, E. coli O157:H7, Listeria, Campylobacter, Mycobacterium tuberculosis, Coxiella burnetii, etc.)
- Greatly reduce spoilage microorganisms (extends shelf life)
- Maintain most sensory and nutritional qualities
Note: Pasteurization is not sterilization. Some harmless bacteria and heat-resistant enzymes remain.
3. Common Pasteurization Methods
| Method | Temperature | Time | Typical Products | Notes |
|---|---|---|---|---|
| Low-Temperature Long-Time (LTLT) / Vat / Batch | 63 °C (145 °F) | 30 minutes | Milk, cream, ice-cream mix (small scale) | Traditional method, still used by some artisanal producers |
| High-Temperature Short-Time (HTST) | 72 °C (161 °F) | 15–20 seconds | Most commercial milk, juice | Standard industrial method |
| Higher-Heat Shorter-Time (HHST) | 85–94 °C | 1–3 seconds | Milk, cream | Used for longer shelf-life products |
| Ultra-High Temperature (UHT) / Ultra-Pasteurization | 135–150 °C | 2–5 seconds | Shelf-stable milk, cream, some juices | Sterilizes the product → months of shelf life without refrigeration |
| Flash Pasteurization (beer/w) | 71–74 °C | 15–30 seconds | Beer, wine, cider | Preserves fresh flavor better than filtration alone |
4. Pasteurization Units (PU) – Beer & Juice
1 PU = 1 minute at 60 °C (140 °F)
Formula (simplified): PU = t × 1.393(T − 60)
- Juice: usually 50–300 PU
- Craft beer: 15–30 PU (minimal pasteurization)
- Large breweries: 100+ PU for shelf stability
5. Home & Small-Scale Pasteurization
Milk (Vat method at home)
- Heat milk to exactly 63 °C (145 °F)
- Hold for exactly 30 minutes (stir gently)
- Cool rapidly in ice water to below 4 °C (40 °F)
Juice / Cider
- Heat to 71–75 °C (160–167 °F)
- Hold for 15–30 seconds
- Hot-fill into sterilized bottles or rapid-cool
Tip: Use a good digital thermometer and a sous-vide controller for precise home pasteurization.
6. Legal Requirements (Examples)
- USA (FDA): Grade A milk must be HTST (72 °C × 15 s) or equivalent
- EU: Milk for direct consumption must be at least 72 °C × 15 s
- Apple juice/cider (FDA): 5-log reduction of pertinent pathogen (usually Cryptosporidium parvum) → typically 71 °C × 6–25 s depending on pH
7. Effects on Nutrition & Flavor
| Component | Effect of HTST/UHT |
|---|---|
| Vitamin C | 10–20% loss (juice) |
| B vitamins (thiamine, B12) | Minor loss in HTST, 10–20% in UHT |
| Whey proteins | Denature >80 °C → affects yogurt culture activity |
| Enzymes (lipase, phosphatase) | Inactivated (phosphatase test = proof of proper pasteurization) |
| Flavor | HTST: minimal “cooked” taste UHT: noticeable cooked/maillard notes |
8. Alternatives to Thermal Pasteurization
- High-Pressure Processing (HPP) – 600 MPa, cold
- Pulsed Electric Fields (PEF)
- UV irradiation
- Microfiltration + cold storage
- Cold plasma, ozone, etc. (emerging)
9. How to Test if Something is Properly Pasteurized
- Alkaline Phosphatase test (milk) – negative = properly pasteurized
- Peroxidase test (distinguishes HTST vs UHT)
- Microbiological plating (pathogens & total count)
10. Pasteurization Table (2025)
| Food / Beverage | Method | Temp / Pressure | Key Pathogens | Shelf Life (ref.) | Common Brands / Notes |
|---|---|---|---|---|---|
| Milk (standard) | HTST | 72 °C × 15–20 s | Listeria, Salmonella, E. coli, Campylobacter | 16–21 days | Most supermarket milk worldwide |
| Milk (vat / small dairy) | LTLT | 63 °C × 30 min | Same as above | 14–21 days | Cream-top, some artisan dairies |
| Milk (ultra-pasteurized / UHT) | UHT | 135–150 °C × 2–8 s | Near-sterile | 6–12 months (unopened, room temp) | Parmalat, Organic Valley shelf-stable, Horizon cartons |
| Milk (ESL – Extended Shelf Life) | HHST + microfiltration | 85–127 °C × 1–4 s | Same as HTST + spore reduction | 30–90 days | fairlife, a2 Milk (some markets), European “fresh-longer” milk |
| Orange juice | HTST | 70–95 °C × 15–60 s | E. coli, Salmonella | 60–90 days | Tropicana, Simply Orange |
| Apple cider | UV or HTST | 71 °C × 6 s or UV | E. coli O157:H7 | 30–60 days | Many craft ciders use UV |
| Beer (macro) | Flash / Tunnel | 60–72 °C × 15–30 s | Wild yeast, spoilage | 12–18 months | Budweiser, Heineken |
| Liquid eggs | HTST | 60–64 °C × 3.5 min | Salmonella | 45–90 days | Egg Beaters, store brands |
| In-shell eggs | Warm-water | 60 °C × 6–14 min | Salmonella | 60 days | Davidson’s Safe Eggs |
| Cold-pressed juice | HPP | 600 MPa × 3–6 min | All pathogens | 45–120 days | Evolution Fresh, Suja |
| Almonds (USA) | Steam or PPO | 80–100 °C steam | Salmonella | Years | All California almonds since 2007 |
| Spices | Steam / Irradiation | 100–120 °C steam | Salmonella, E. coli | Years | McCormick, frontier co-op |
| Oysters | HPP | 300–600 MPa | Vibrio | 18–21 days | “Pasteurized” oysters (raw taste) |
| Pickles / hot sauce | Hot-fill | 85–95 °C × 30 s | Yeast & molds | 2+ years | Vlasic, Tabasco |
11. Frequently Asked Questions
- Is raw milk safer than pasteurized?
- No. Raw milk causes hundreds of outbreaks yearly (CDC data). Pasteurization eliminates dangerous pathogens while keeping most nutritional value.
- Can I re-pasteurize milk?
- Technically yes, but repeated heating increases cooked flavor and vitamin loss.
- Does pasteurization kill all viruses?
- Most common foodborne viruses (norovirus, hepatitis A) are inactivated, but some heat-resistant viruses may survive UHT.