Rabbi Joseph B. Soloveitchik ate generic cheeses without certification. Isaac Klein's tshuva authorized the use of cheese made from non-kosher rennet, and this is widely practised by observant Conservative Jews and Conservative institutions. Eggs The eggs of kosher birds are kosher. Eggs are considered pareve despite being an animal product. Blood found in eggs Occasionally blood spots are found within an egg, which can affect the kosher status of the egg. The halacha varies depending on whether or not there is a possibility of the egg being fertilized. If the egg may have been fertilized, the Rishonim and Shulchan Aruch suggest a complex set of rules for determining whether the egg may be eaten; among these rules, if blood appears on the yolk, the entire egg is forbidden. To avoid the complexity of these rules, R' Moshe Isserles records a custom not to eat any such eggs with blood spots. If the egg was definitely unfertilized (laid by a hen kept isolated from roosters), many authorities (including Rabbis Moshe Feinstein and Ovadiah Yosef) rule that one may remove the blood spot and then eat the remainder of the egg. This is the case nowadays, when battery eggs form the majority of available produce. Regarding the question of whether one must check an egg for blood spots, the Shulchan Aruch rules that one may eat hard-boiled eggs where checking is impossible. R' Moshe Isserles adds that checking is not required, but that a custom exists to check eggs if they are cracked during the daytime (when blood could be seen). A contemporary Ashkenazi authority writes that while "halacha does not require" checking supermarket-bought eggs, "there is a minhag" to do so. Nevertheless, eggs are not checked in commercial settings where doing so would be expensive. Gelatin Gelatin is hydrolysed collagen, the main protein in animal connective tissue, and therefore could potentially come from a non-kosher source, such as pig skin. Gelatin has historically been a prominent source of glue, finding uses from musical instruments to embroidery, one of the main historic emulsions used in cosmetics and in photographic film, the main coating given to medical capsule pills, and a form of food including jelly, trifle, and marshmallows; the status of gelatin in kashrut is consequently fairly controversial. Due to the ambiguity over the source of individual items derived from gelatin, many Orthodox rabbis regard it as generally being non-kosher. However, Conservative