I've been reading some FB posts about Vinegar that is used for pickling, The author (may be in the US) says that vinegar manufactures have reduced the acidity percentage in some vinegars from the standard 5% used for pickling to 4%.
"On Sept. 9, I shared a Facebook post about the lower acidity of vinegar that some manufacturers are selling and whether it's safe to use for canning purposes. The post indicated that instead of the standard acidity of 5%, there is also vinegar with 4% acidity being sold. I contacted the National Center for Home Food Preservation (
https://nchfp.uga.edu/#gsc.tab=0) and promised I would let you know what they had to say:
"Here is our official statement regarding vinegar:
"The National Center for Home Food Preservation acknowledges the concerns raised by consumers regarding the use of 4% vinegar acidity for canning. We would like to provide the following important points for your consideration if you have utilized vinegar in your home canning practices:
"Recipe Recommendations: It is crucial to note that all our recipes, including those
from the National Center for Home Food Preservation (NCHFP) and the United States
Department of Agriculture (USDA), were extensively tested and recommended the use of vinegar with 5% acidity. Currently, it is strongly advised against using vinegar with lower acidity levels (<5%), as it may not be sufficiently strong to ensure the safety of the canned products. Always remember to check the vinegar label for its acidity level.
"Evaluating Canned Food Products: If you have used vinegar with lower acidity
(less than 5%) in your canned food products and you followed a validated recipe, we
recommend considering the following:
i) If your canned food has been preserved for less than 24 hours using 4%
vinegar, it is advisable to store the jars in the refrigerator to maintain the
safety and quality of the product.
ii) If your canned food has been preserved for more than 24 hours using 4%
vinegar, it is advisable to discard the product.
"Please remember that ensuring the safety of your home-canned products is of utmost importance. Following tested and approved recipes, including the use of recommended vinegar acidity, is crucial for maintaining the safety and integrity of the preserved foods.
"If you can't find 5% vinegar locally, we would suggest trying to find some to order online."
Just a heads up to check the % before using any vinegar for your pickles. It would be heart-breaking to go to all the effort of growing, preparing and pickling veg for it to unsafe to eat.
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This should be a conversation starter!
, do you offer him a coffee? Asking for a friend 
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