Do not salt meat or ground meat before freezing; salt speeds up fat rancidity in frozen meat and shortens its quality life in the freezer. The effect is more noticeable in ground meat because grinding exposes more of its fat and surface to air. Freeze meat without salt and season it after thawing. If you freeze salted and seasoned meatball mixture, use it sooner.
A freezer stops most bacteria from multiplying, but it does not stop every change inside meat. Even in the freezer, fat slowly reacts with air and can develop a stale, bitter smell and taste over time. Salt is one of the substances that speeds up this reaction. A piece of meat salted before freezing develops this smell sooner than an unsalted piece. The meat remains safe, but its flavor deteriorates when cooked, and seasoning will not cover that taste. The rate of change also depends on the temperature: it slows considerably in a freezer kept at −18°C / 0°F or colder, and speeds up in a freezer whose door is opened often and whose temperature fluctuates.
Ground meat is most susceptible to this change. During grinding, the meat is broken up, the fat is dispersed, and more surface area is exposed to air. Unsalted ground meat retains its quality in the freezer for 3–4 months, while raw mixture seasoned with salt and spices lasts 1–2 months; salted raw products such as sausage also have a shorter freezer life for the same reason. Salt added to ground meat too early also dissolves proteins and makes the mixture paste-like; this texture becomes even more pronounced in salted mixture that has been frozen and thawed.
So the method is simple: freeze ground meat and cuts of meat without salt, divided into portions and packed in bags with the air removed. If you flatten ground meat into a thin layer in the bag, it freezes and thaws faster. Thaw it in the refrigerator. Add salt to thawed meat based on how many minutes remain before cooking; add salt to ground meat while preparing the meatball mixture, just before shaping it. Cook ground meat thawed in the refrigerator within one to two days.
If you want to prepare meatballs ahead and freeze them, there are two options. First, prepare and shape the mixture with salt and spices, freeze the pieces separately on a tray, then transfer them to a bag; cook these meatballs within 1–2 months. Second, freeze the mixture without salt and knead in the salt after thawing; this allows longer storage but requires kneading the mixture one more time. Whichever option you choose, label the bag with the date and whether it contains salt.
The same rule applies to marinated meat. You can freeze meat marinated with salt and spices, but use it sooner than unsalted cuts, within one to two months. Remember that the salt in the marinade continues to act on the surface of the meat while it thaws; meat left marinating for a long time may have a spongy surface after thawing. For the best result, freeze meat without salt, marinate it after thawing, and start counting the marinating time from then.