The Conservative and Orthodox movements differ with regard to the kashrut of certain food additives.
Because of the chemical changes that take place during processing, the Committee on Jewish Law and Standards (CJLS) has determined that many additives are so totally reconstituted that they may be considered a totally new food (davar ḥadash) and that their origins are therefore no longer of concern (CJLS Responsa 1980–1990, pp. 286–289).
Among the chemical additives considered kosher and pareve by the Rabbinical Assembly are: dextrose, mono-and diglycerides, lactate, lactic acid, lecithin, pepsin, polysorbate 80, propylene glycol, sodium stearoyl-2-lactylate, and sorbitol.
Should one find an additive of unknown origin in a product without a hechsher, it is best to consult a rabbi for advice.
One specific food impacted by the kashrut of additives is cheese, specifically focusing on rennet, an additive which helps the cheese to curdle.
The Committee on Jewish Law and Standards of the Rabbinical Assembly has determined that commercially made cheeses, unless they are mixed with non-kosher ingredients, can be considered kosher even without a hechsher because the rennet or microbial rennet are a totally new food, as noted above (Klein, p. 306).
Yet another difference between many Conservative and Orthodox rabbis in the area of kashrut involves gelatin.
Gelatin is made from dried hide, bones, horns, and hoofs, which are not edible in an unprocessed state. Because the process that reduces them to gelatin essentially creates a new entity, many Conservative rabbis permit the use of gelatin, even without a specific hechsher, in food products (Isaac Klein, “The Kashrut of Gelatin,” in Responsa and Ḥalakhic Studies, pp. 71–88).
Adapted with permission from The Observant Life.