Irui can only kasher the outer layer of a kli. Hot water poured against a cold kli is an example of חם לתוך צונן (hot onto cold) of which we say (Pesachim 76a) תתאה גבר ואדמיקר ליה בלע. The bottom surface succeeds in cooling down the water but not before the water succeeds in kashering the topmost layer.
In the early twentieth century, Belgian colonists in the Congo noticed that the Congolese were careful to store elephant meat in papaya leaves. Intrigued, they found that the papaya leaves, besides protecting the meat, tenderized it. Laboratory analysis demonstrated that a particular enzyme, called papain, was the agent of the process.
Rabbi Eli Gersten
When a cold item is placed onto a hot surface, Halacha tells us to view the cold item as though it were hot, even though the item remains cold. Conversely, if a hot item is placed on a cold surface, we view the hot item as becoming cooled down. However, in this case we say that until it cools down, there is a kdei klipa transfer of ta’am. This concept is brought in the Gemara Pesachim (76a) and referred to as ta’tah gavar (the bottom surface overpowers).
Judaism teaches that we are to enjoy the beauty, benefits, and bounty of creation. However, when it comes to overeating, Judaism is clear that too much of a good thing is a bad thing.
If one does not understand the process involved in creating a granola bar, one could study the ingredient panel a hundred times and still not be able to answer the above question. However, through our access to the companies that produce these bars we are privy to information that is important in resolving this issue.
Questions of bishul akum surface all the time, and it is important when reviewing products and ingredients to be mindful of the issues of bishul akum. The following are some recent issues that have been discussed in the office relating to bishul akum.
A summary of the OU’s position about using bitul in Kosher food productions.
Mailbox י”ז תמוז אשר במהרה יתהפך לנו ליום שמחה כבוד הרבנים החשובים שליט”א תמוה לי קצת הנושא אודות חשש בישול גוים – כי ראיתי הרב בעלסקי שליט”א כותב שכל מתחלה נעשה הבישול רק כדי לעשות ממנו דבר שאינו עולה על שלחן מלכים אז אין כאן חשש בישול עכו”ם [וזה ההיתר שנוקטים האו יו ברייז קריספיס, […]
When this plant was first set up as a kosher facility, it was known that they had a non-kosher plant that produces assorted products on the same campus. Of course, the issue of steam return condensate was brought up. It turned out that condensation from the non-kosher factory was not being returned to the boiler so there was no problem to certify the kosher division.
A basic phenomenon in chemistry plays a crucial role in industrial kashrus. When two chemicals react with one another, one will be used up before the other. The chemical used up first is called a “limiting reactant” and the chemical which is not used up is an “excess reactant”. Often the excess reactant is recovered, purified, and used again in another production.