This product is good for five days if kept in the fridge.
It will last for 5 days if you keep refrigerated.
Both of these phrases informs the person that the product will not go off if it is kept refrigerated (in the fridge). We call things that have gone past their expiry date - gone off.
"Euw, this milk has gone off" - It would smell horrible and probably make us gag.
"This doesn't taste right, I think it's gone off".
これらのどちらの表現も、この商品は要冷蔵保存と言う事を伝えています。
賞味期限の切れたものを "gone off"（悪くなる）と言います。
【例】
"Euw, this milk has gone off"
（うぇ、この牛乳腐ってる）
- これはひどい臭いで吐き気がしたりします。
"This doesn't taste right, I think it's gone off"
（変な味がする！これ腐ってると思う）
This product will last five days if kept refrigerated.
If you keep this product in the fridge, it will stay good for at least five days.
Many products nowadays have to be kept refrigerated in order to stay fresh.
"This product will last five days if kept refrigerated."
'to last' = this means to remain fresh and edible (in terms of foodstuffs)
"If you keep this product in the fridge, it will stay good for at least five days."
'to stay good'= this means to stay fresh and have a good quality that can be eaten
"Oh no! I didn't put the milk in the fridge, now it's gone bad and smells awful!"
'to go bad'= when a food product is expired and no longer can be eaten, when it starts to rot.
最近では多くの製品が新鮮さを保つために冷蔵される必要があります。
【例文】
"This product will last five days if kept refrigerated."（この商品は冷蔵で5日間持ちます）
'to last'とは、新鮮で食べられる状態を保つという意味です（食品の場合）。
"If you keep this product in the fridge, it will stay good for at least five days."（この商品は冷蔵庫に入れておけば、少なくとも5日間もちます）
'to stay good'とは、新鮮さや食べられる良い質を保つという意味です。
"Oh no! I didn't put the milk in the fridge, now it's gone bad and smells awful!"（牛乳を冷蔵庫に入れなかったら、もう悪くなってひどい臭いになってしまった！）
'to go bad'とは、食品の賞味期限が切れたり、腐り始めてもはや食べられなくなったことを意味します。
This product will keep for an extra 5 days in the fridge
This product will keep for 5 days if refrigerated
When talking about keeping/storing food then you have to be careful as you could make yourself ill if something isn't stored correctly so you should tell someone how to store the item
'in the fridge' means to place the item in the fridge
'refrigerated' means to be cold when stored in the fridge
食べ物は正しく保管しないと、健康に関わることになるかもしれません。ですから、保存方法について伝えた方が良いです。
'in the fridge'は「冷蔵庫の中に」という意味です。
'refrigerated'は「冷蔵庫で保管された」という意味です。
The product will last for five days if kept refrigerated.
The above sentences are different ways to say the same thing to a customer. If you would like to emphasize the need for the product to be cold/cool, you can use the phrases, "in the fridge," "kept refrigerated," or "in the refrigerator." If you would like to emphasize the life expectancy of the product, you can use the phrases, "it will last for," "it is good for," "it's usable for," "it will expire after," and then state the time period (five days).
上記の文章は同じことを異なる言い方で言っています。
その商品を冷やす必要があることを強調したいなら、次のフレーズが使えます。
"in the fridge"（冷蔵庫で）
"kept refrigerated"（冷蔵庫で保管して）
"in the refrigerator"（冷蔵庫で）
その商品の“寿命”を強調したいなら、次のフレーズが使えます。
"it will last for"（～の間持つ）
"it is good for"（～の間持つ）
"it's usable for"（～の間使える）
"it will expire after"（～の間持つ）
この後に期限（5日）を伝えます。
You can keep this food for a working week if you refrigerate it.
This food will not last long if you do not refrigerate it. If you do it will last 5 days or more.
The working week is something that lasts for 5 days in most countries. And in saying that the food would not last the working week the person in London would understand that it means 5 days.
"This food will not last long if you do not refrigerate it. If you do it will last 5 days or more.
This is giving the full description of what is happening with the food it is saying that it will spoil if it not put into the fridge. Then the opposite information is given.
"working week"（一週間の労働時間）は、ほとんどの国で5日間です。
"You can keep this food for a working week" と言うと、ロンドンの人はそれが5日間のことだと理解します。
----
"This food will not last long if you do not refrigerate it. If you do it will last 5 days or more."
（この食べ物は冷蔵庫に入れないと長く持ちません。冷蔵庫に入れると、5日間かそれ以上持ちます）
これは状況を完全に説明しています。冷蔵庫に入れないと長く持たないと伝えて、その反対の状況についても説明しています。
The expiry date of this product is five days from now
You should consume this product within 5 days
Probably, in a confectionary store, if you want to give details of the 'best before' date, it is advisable just to state the facts as in the first example sentence above.
If you want to give more personal advice, then the second sentence may be more appropriate.
If it is a refrigerated or frozen item then it is probably not necessary to mention that it should be kept in a fridge. That is obvious! Eg: milk, yogurt, cheese etc.
イギリス 
アメリカ合衆国 
