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I just went on a well recognised cooking website for a salad recipe and it said that the salad dressing can only be stored for 48hrs as it has raw garlic in it and keeping it any longer can have disastrous results.

I looked it up and google tells me raw garlic I oil can cause botulism, however, in a dressing it is also half vinegar. Is this enough to keep for longer?

I grew up with my Mum making a salad dressing consisting of raw garlic, half apple cider vinegar half olive oil honey salt and pepper and we would use it over a month.

Is this not generally a safe thing to do? If the dressing is half vinegar does that keep it safe to eat for longer?

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    Is there something in there to cause it to emulsify, or does the garlic end up just sitting in one of the liquids (presumably the vinegar as that's denser than oil)?
    – Chris H
    2 days ago
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    If somebody would like to answer: Please note that our site, as with other SE network sites, does not accept opinion-based answers. Thus we are required to answer food safety questions strictly according to safety regulations from authorities like the FDA. If you can't provide such information, and only suggest whether you personally would consider it safe, please refrain from posting.
    – rumtscho ♦
    yesterday

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A pH of less than 4.6 is enough to inhibit the growth of the bacteria that produce botulinum toxin. Your safest route would be to get some test strips and measure the pH of your dressing. For comparison, and in general (but test yours), vinaigrettes range from 3.6 - 4.2. This, combined with refrigeration dramatically reduces risk. Even so, most recommendations suggest using well within a week.

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    There are a couple of issues with your answer. First of all, the pH of 4.6 should only be used in a commercial setting, where rigorous quality and hygiene standard are followed, and where high quality, calibrated pH testing equipment is used. It's typically recommended that home users aim for a pH of 4.0 or lower, in order to have a safety margin. The other issue is that when using standard pH test strips, the colour of what is being tested can interfere with the reliability of the reading, as can using them to test oil. If you test oil, you should use strips specifically for use with oil.
    – Hollis Hurlbut
    17 hours ago
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Indeed, garlic in oil has been responsible for botulism cases. Sufficient acidity would prevent growth of Clostridium botulinum, but it is not entirely clear whether your salad sauce is sufficiently acidic. Additionally, and perhaps more importantly, the acid may not penetrate the cloves properly so that the bacterium can still grow inside of a clove.

In commercial foods, this is prevented by acidifying the garlic. According to a publication by the University of Idaho1, this can be reproduced at home. The paper describes the procedure in detail. The basic idea is:

  • Use a table spoon of citric acid in 2 cups of water to produce a 3% solution.
  • Add 2/3 of a cup garlic which is peeled and chopped to pieces not larger than 1/4 inch and mix.
  • Let the mix sit at room temperature for 24 hours.
  • Drain and use in an oil of your choice.

This procedure lowers the pH of the garlic pieces sufficiently to prevent growth of botulinum. Even in pure oil, let alone in a vinaigrette, the garlic would be safe to store at room temperature. Additional refrigeration would add an extra layer of safety and extend shelf life in general as well.

1 The article is probably based on this scientific paper.

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