Cataloging
If the surface has already dried out and the pig kidneys begin to smell slightly unpleasant, they should be discarded. Even if no further changes are visible on the surface, the decomposition process could have already begun.
The nutritional value of pig kidneys is high. They contain a lot of vitamins A, C, and D. The iron content is also very high. Unfortunately, pig kidneys also contain a lot of cholesterol and have a high purine content. Additionally, the risk that they may be contaminated with heavy metals or medications is higher than in pork muscle meat. Therefore, it is generally advisable to buy controlled organic products when purchasing organs and only use kidneys from young pigs.
The recommendations for maximum consumption frequency of organs vary according to source, ranging from once a week to once a month. People who need to watch their cholesterol levels and those prone to gout should be very careful with the consumption of pig kidneys and, if at all, only eat small portions.
Storage
Since organs generally have a high water content and kidneys are no exception, they are quickly spoilable. It is therefore very important to buy fresh kidneys and process them as soon as possible on the same day. If it is unavoidable to store fresh kidneys overnight, they should first be stored in liquid - milk or water - and secondly kept as cool as possible. The correct place in the refrigerator is directly above the vegetable compartment, towards the back.
Frozen storage is possible but not particularly recommended. Organs react very sensitively to temperature fluctuations, and the taste and consistency change through freezing. Before freezing, the kidneys must be prepared for cooking.
Cooking
Pig kidneys are prepared by frying or grilling. First, they need to be prepared: cut them in half lengthwise, thoroughly wash them, and remove both the inner ureters, which can be recognized as tubes, and the white skins. After that, let them soak for 30 to 60 minutes. Adding a splash of vinegar or lemon juice to the water will make the kidneys more tender. This effect is further enhanced if they are then soaked in milk for half an hour. Unlike beef kidneys, pig kidneys do not need to be blanched before cooking.