I've been making my own mincemeat for a few years and usually use it all up, but I've still got 2/3 of a jar left from last year. It's in a clip lock Kilner jar and has been in the fridge since it was opened. I don't think I can see any mould and it still smells great, but would you use it? If it was unopened with no air gap at the top I wouldn't hesitate, but just not sure with it being open and a bit used. If it makes a difference it was an adaptation of Mary Berry's recipe which uses butter rather than suet, and it's got a good glug of whiskey in it.