How many days does milk keep once opened? What about yoghurt and cheese?
This answer is a draft. It stays unpublished until legal review and source verification are complete.
"I opened the milk two days before its best-before date; how long can I drink it?" "What about yoghurt opened a week ago?" Dairy is used every day, yet many people do not know how long it keeps after opening. The date on an unopened pack and the number of days after opening are two different things, and Japanese milk has a few particularities of its own. Here is the sorting.
Guide after opening
| Dairy product | After opening (fridge, 10°C or below) | Storage tips | Signs it has gone off |
|---|---|---|---|
| Milk (UHT, carton) | 2–3 days | The door pocket swings in temperature, so store at the back of the fridge. Do not drink from the carton. Close the spout | Sour smell, separation or lumps, curdles when heated |
| Low-temperature pasteurised milk (63–65°C for 30 minutes) | 1–2 days after opening; a short date even unopened | As above | As above |
| Long-life milk (shelf-stable) | Refrigerate after opening, 2–3 days | Room temperature until opened | As above |
| Plain yoghurt (large tub) | 3–4 days | Serve with a clean spoon; do not eat from the tub. Liquid on top (whey) is normal | Mould, pink or yellow discolouration, alcohol smell, strong sourness |
| Drinking yoghurt, single-serve yoghurt | Same day once opened | — | — |
| Processed cheese (slices, 6P wedges) | 2–3 weeks (individually wrapped pieces count as unopened) | Wrap tightly in cling film | Mould, dried and hardened |
| Natural cheese (mozzarella, camembert, brie) | A few days to 1 week. Mozzarella in water 2–3 days | Cling film plus a sealed container | Mould other than the natural white rind; strong ammonia smell |
| Hard cheese (parmesan, cheddar) | 2–4 weeks | Cling film plus a sealed container. Mould can be cut away with a 2.5 cm margin (see our separate article) | — |
| Butter | About 1 month after opening (fridge). 3–6 months frozen | Keep in the foil wrapper, away from strong-smelling foods | Yellowing surface, rancid smell |
| Fresh cream | 2–3 days after opening | Close the spout and store upright | Separation, sourness |
| Condensed milk | 2–3 weeks | Clean spoon | Discolouration, crystallisation |
| Infant formula (powder) | 1 month after opening (tin). Once made up, use within 2 hours; discard leftovers | Dry place; extra hygiene for infant formula | — |
- Best-before vs use-by: most milk carries a "best-before" date (賞味期限, shōmi kigen: the date for best quality; unopened milk is often still drinkable a little past it), while low-temperature pasteurised milk and the like carry a "use-by" date (消費期限, shōhi kigen: do not drink after it). Both assume an unopened pack; once opened, the table above takes precedence.
- Why not the door pocket: the temperature rises every time the door opens, and can be 3–5°C higher than the body of the fridge. Milk and yoghurt go at the back; use the door for condiments.
- Pasteurisation methods: UHT (ultra-high temperature, 120–150°C for 2–3 seconds) accounts for more than 90% of Japanese milk. LTLT (low temperature, 63–65°C for 30 minutes) tastes closer to fresh milk but keeps for less time. "Whole" (成分無調整), "low-fat" (低脂肪) and "processed milk" (加工乳) are separate categories unrelated to pasteurisation.
- Leftover milk you have drunk from: bacteria from the mouth get in and it can turn sour by the next day. Pour into a glass.
- Freezing: milk separates when frozen and is not suitable for drinking after thawing (fine for cooking). Butter, hard cheese and pizza cheese freeze well.
- Children and pregnant women: some natural cheeses (unpasteurised imported soft cheeses) carry a Listeria risk, so pregnant women should check for a "heat-pasteurised" label. Japanese processed cheese and most Japanese natural cheese are made from heat-pasteurised milk.
- Dairy food poisoning: the main causes are long storage after opening, leaving dairy at room temperature (lunch boxes, in the car) and drinking from the container. There are also warnings about school-lunch milk left at room temperature in summer.
[Verify] The after-opening figures are general guides from makers and the industry body (Japan Dairy Industry Association). Check the pasteurisation-method shares and the Listeria warning against MHLW and Dairy Association material.
Misunderstanding 1｜Within the best-before date, it is fine even after opening
The best-before date is a guarantee for the unopened pack; once opened, 2–3 days is the guide. Finish it soon, whatever the date.
Misunderstanding 2｜UHT milk keeps longer even after opening
Only the unopened shelf life is longer; once opened, airborne bacteria get in and it is the same as any other milk.
Misunderstanding 3｜Yoghurt is fermented, so it cannot go off
Bacteria other than the lactic-acid bacteria, and moulds, do grow. 3–4 days after opening, with a clean spoon. Discard if there is mould, discolouration or an alcohol smell.
Misunderstanding 4｜Milk belongs upright in the fridge door pocket
The door pocket swings in temperature and is unsuitable for milk and yoghurt. Put them at the back of the fridge.
Misunderstanding 5｜Liquid on top of the yoghurt means it has gone off
The liquid on top (whey) is normal separation, and it is nutritious too. Stir it in. The signs of spoilage are mould, discolouration and smell.
---
Sources
- Japan Dairy Industry Association [一般社団法人日本乳業協会], "Storing milk and dairy products: Q&A" [牛乳・乳製品の保存方法とQ&A]
https://www.nyukyou.jp/dairy/
- Consumer Affairs Agency, "Food labelling: use-by and best-before dates" [食品表示：消費期限と賞味期限]
https://www.caa.go.jp/policies/policy/food_labeling/
- Ministry of Health, Labour and Welfare (MHLW), "Listeria food poisoning (cautions for pregnant women and older people)" [リステリアによる食中毒（妊婦・高齢者への注意）]
https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/shokuhin/syokuchu/
⚠️ Editorial note: the source URLs above were identified by search. Our working environment cannot reach go.jp domains, so the contents have not been checked against the text. Verify every source before publication and record who checked it and when.
About this article
What we share here are ideas and everyday practices passed down among people living in Japan, together with general information drawn from public sources. They are not official recommendations, and they are not professional instruction. Practices vary between households and regions.
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