The best way to "fix" late blowing is to avoid it in the first place. The clue here is the large horizontal slits, which are not like the round eyes that you see in Swiss. To me that's a dead giveaway for late blowing. This is caused by contamination from a gas producing bacteria, usually a Clostridium. While this is not pathogenic, it obviously causes physical defects and often produces off flavors. Clostridium is a natural soil inhabitant, so the first line of defense is CLEANLINESS. Be sure that your counter top, vat and all utensils are clean and sanitized. Avoid any environmental influences like open doors or windows, dogs in the kitchen, other people "peeking" into the cheese vat, etc. Air movement from fans or HVAC (especially with dirty filters) can blow contaminants into the vat. As mentioned in many other threads, you can use sodium nitrate (saltpeter), but there are also adjunct cultures that will naturally inhibit Clostridium and other contaminants.
