This requires a bit of grinding because the later quests do not require mincemeat and it will not really be needed by that point. The best method to get a large amount of unripe fruit is to constantly water and harvest the stomach tree until it produces sap. Use that sap to have all trees get unripe fruit. Then, use your shears to harvest all of it. Use your broom to collect all the meat. Your meat grinder will gain lots of experience fast. Having thirty birds will also help. Collect the meat regularly or the meat grinder will stop producing more.