“You mean that I have to wait SIX HOURS after I eat cheese before I can eat meat??” Well, often yes. The Remo (Shulchan Aruch Yoreh Deah 89:2) states that the minhag is to wait after eating hard cheese before partaking of meat, just as one waits after meat before dairy; this minhag has become accepted practice for Ashkenazim. (See Chochmas Adam 40:13.)

What is the reason for this chumra (stringency)? Poskim point to the reasons for waiting after eating meat before consuming dairy foods and apply these reasons to the case of hard cheese (before meat) as well. According to Rashi (Chullin 105a d.h. “Assur”), one must wait after eating meat before partaking of milk due to the residual aftertaste of meat left in one’s mouth as a result the meat’s fattiness. According to the Rambam (Hilchos Ma’achalos Asuros 9:28), the rationale for waiting after meat before dairy is due to the likelihood of meat stuck in one’s teeth (“basar bein ha-shinayim”); any such meat requires time to dislodge or disintegrate before one subsequently consumes dairy food. (See Beis Yosef Orach Chaim 173, Aruch Ha-Shulchan Yoreh Deah 89:11, Taz Yoreh Deah 89 s.k. 4.)

Not all authorities concur to the custom of waiting after eating hard cheese before eating dairy. The Tur and Shulchan Aruch omit this restriction entirely, and the Maharshal (quoted by the Shach, Yoreh Deah ibid. s.k. 17) dismisses it as “minus” (heresy), arguing against it and noting that the Gemara (Chullin 105a) specifically states that there is no need to wait at all after consuming cheese before then partaking of meat. However, the Gra (ibid. s.k. 11) writes that the Zohar in Parshas Mishpatim endorses the position of the Remo, and the Gra takes issue with the Maharshal’s contention that the Remo contradicts the Gemara’s statement that one may eat meat after cheese, explaining that the practice to refrain from hard cheese before meat is a chumra akin to other personal chumros practiced by the Amoraim and recorded in the sugya in Chullin. In fact, the Beis Yosef himself (Tur Orach Chaim 173) invokes the Zohar and endorses the practice of waiting after (hard) cheese, and he also quotes the Mordechai (Chullin siman 687), who noted that the Maharam would wait before partaking of meat after he ate (hard) cheese due to the likelihood of cheese residue stuck in the teeth, similar to the rationale of the Rambam noted above.

What is the waiting period after hard cheese?
After eating meat, there is a machlokes as to how long one must wait before consuming dairy products. The Shulchan Aruch (YD 89:1) is of the opinion that the waiting period is six hours, and the Remo (ibid.) also advises that one wait this period, although he references various other prevalent opinions and customs, such as waiting one hour. (German Jews traditionally wait three hours, while Dutch Jews wait only one hour.)

The various opinions and resultant minhogim as to how long one must wait after eating meat before consuming dairy revolve around Mar Ukva’s statement in the Gemara (Chullin 105a), that upon eating meat he would wait “until the next meal” to partake of cheese. The question is how one should understand the break period of “until the next meal”. It may be short or long, depending upon how one defines the day’s meals and the relationship between them; Mar Ukva’s practice may also not have mandated any waiting period, as any real break between meals may suffice. These are the issues upon which the above machlokes and customs hinge.

The poskim are clear that the waiting period after consuming hard cheese before then eating meat is identical to the waiting period after eating meat before one wishes to partake of dairy foods. (See Taz 89:4, Aruch Ha-Shulchan 89:11, Chochmas Odom 40:13. However, see Shach 89:16.) Thus, one should follow his personal custom regarding waiting after meat for the purpose of waiting after hard cheese.

A most critical question, however, is what constitutes hard cheese (for the purpose of waiting) according the Remo. Is all cheese which we refer to as “hard” included in this category? The answer is a clear “no”.

The Shach (YD 89 s.k. 15) and Taz (ibid. s.k. 4), among other major early poskim, explain that cheese is considered to be hard for the purpose for waiting if it is six months old (or if it has developed holes, done via worms in the old days - see Aruch Ha-Shulchan ibid.).

It should be noted that the six-month period is apparently not absolute. This is emphasized by some contemporary poskim, for the Shach (ibid.) writes that, “In general, six month-old cheese is classified as hard”. The Shach seemingly posits that six months is an approximate estimation of when cheese is categorized as hard for the purpose of waiting – it is not a hard rule or a rigid shiur. (It must also be kept in mind that the Beis Yosef referenced above refers to waiting after “cheese” – period. He does not stipulate that it must be aged or the like. Apparently, any firm cheese which can stick to the teeth is included in the chumra, according to the Beis Yosef.)

There are three basic positions among American poskim (and the kashrus agencies which they guide) regarding how to determine which types of cheese require one to wait after consuming them before then partaking of meat:

1) Some poskim advance a quite conservative position in categorizing hard cheese. These poskim look exclusively to the cheese’s texture and only require a waiting period for cheese which is so brittle such it shreds or grates when cut, unable to be sliced. The vast majority of cheeses do not fit into this category; Parmesan is the only common cheese which meets this extremely-limited definition of hard cheese.

2) Other poskim and kashrus agencies take a totally different approach. They hold that if cheese is six months old, it requires a waiting period, regardless of the cheese’s texture (or taste). In fact, these poskim and agencies assure (by use of production-date codes) that the consumer is knowledgeable of the date of manufacture of any cheese they certify so that the consumer can easily determine when the product has become six months old. These poskim and agencies are aware that the date of manufacture is especially relevant for cheese with a long shelf-life. Many varieties of cheese (e.g. Muenster, Provolone, some types of Cheddar) are not always aged by their manufacturers for significant periods of time. However, these cheeses may become six months old or more by the time they arrive on the consumer’s table, as they are well-preserved and are able to remain fresh for extended durations. These poskim and agencies advise that one wait before eating meat after consuming such unintentionally-aged cheese, whereas other poskim and kashrus agencies do not endorse a waiting period in such cases.
Consultations with dairy and cheese experts have revealed that cheese indeed continues to “ripen” (develop) even after it is packaged, but the extent and quality of such ripening depend on a variety of conditions, including the type of cheese, storage temperature and moisture level, as well as method of packaging.
Those who are machmir to wait after all cheese which is six months old, even if the cheese reaches the six-month period incidentally while sitting on a supermarket shelf, point to the ongoing ripening process even after packaging. Those who do not require waiting after such cheese hold that the rate of ripening after packaging is insignificant, as – if ripening after packaging would affect the cheese in any serious way, noticeably transforming the texture or taste – the manufacturer would not be able to sell stable and predicable product, for the ability of the cheese to ripen so as to materially change it would be present once the cheese leaves the factory. Although it is true that one can retain many non-aged cheeses well past their expiration dates and thereby cultivate a truly ripened, highly-enhanced product, this latter position points to the fact that cheese eaten within its expiration date is expected by the manufacturer to retain its qualities and characteristics as at the time of sale, when the cheese was surely not aged (for six months).

3) A third, arguably more complex but quite textually-grounded approach, is that (a) cheese which must be aged for approximately six months in order to attain proper very firm texture, and (b) cheese of any age which has a potent aftertaste, are categorized as hard cheeses for the purpose of waiting after their consumption. Thus, a three-month aged cheese may subject one to a waiting period if its aging endows the cheese with a very pungent flavor (resulting in a strong aftertaste) which it would not possess were it aged for a lesser duration, and cheese which must be aged at the cheese factory for around six months in order to be considered to be that specific variety of cheese, both necessitate waiting after their consumption before eating meat. (Since the “six-month” aging period is likely really an estimate reflective of significant hardening, and earlier poskim have posited that a cheese’s lingering aftertaste due to its fattiness is a factor in having to wait after eating it, this position does not adopt an exact number of months for which a cheese must be aged in order to require a waiting period, as each cheese must be evaluated by the two factors above.) On a practical level, this approach mandates waiting after Romano cheese (among others), as it cannot be made unless it ages for five to seven months (which meets the six-months approximation), while a cheese which does not need such aging but has nonetheless aged on a supermarket shelf for six months or longer would not necessitate waiting.

The truth is that many cheeses undergo several phases of aging. These cheeses are initially left to sit for one day to several weeks in order for whey (excess liquid) to drain and for the curd (cheese mass) to dehydrate and stiffen, as a metamorphosis from a loose, moist curd to a dry, firm one occurs. The second phase of aging is when these cheeses develop their unique taste profiles and harden to much stiffer textures. Cheeses which must age and ripen during this second phase for approximately six months to a degree which significantly hardens them as necessary, and cheeses which are aged for even shorter durations during this phase in order to brings out extremely powerful taste, are those which this approach addresses.

It should be kept in mind that, cheese which is intended for conversion to cheese powder often does not require prolonged aging periods, as firm texture is not necessary and taste can be artificially developed in shorter periods by use of lipase and other enzymes and flavor agents. Furthermore, different sub-varieties of cheese of the same cheese type can be aged for vastly different amounts of time. These differences reflect divergent grades of the same variety of a specific cheese, as determined by its aging. (See list of cheese aging for such differences in aging periods of the same type of cheese. Fresh mild cheddar is aged for two months, while old, sharp cheddar can be aged for years; the same holds true for Provolone and other cheeses, each of which offers various grades of aging.)

An exception to the practice of waiting after aged hard cheese should likely be made for Feta, a Greek rennet-set cheese which is cured in brine (salt-water solution) for a period that ranges from a two months to six months. Unlike other types of aged cheese, feta is not exposed to air during its curing, and its texture is not excessively hard. It is therefore, possible that feta would not be considered a hard cheese for purposes of waiting six hours, even if it is cured for six months. As there is no halachic literature on the subject, one should ask his personal moreh hora’ah if any waiting period is advised.

What is the din if hard cheese is melted? There is a well-known approach of the Yad Yehuda (YYK 89:30), who asserts that melted cheese is not subject to the Remo’s chumra. Some apply this ruling to all melted cheese (e.g. Parmesan cheese melted onto pizza), while others contend that the Yad Yehuda’s position only pertains to cheese melted into food (e.g. lasagna), whereas hard cheese melted onto food and melted cheese which is not integrated to become part of another food remains subject to the Remo’s waiting period. Others apply the Yad Yehuda’s position to all cheese which has been melted, even if it has become re-hardened by the point of consumption (as is the case with American cheese, which is basically cheddar that is melted and mixed with additives, and is then re-hardened).

Furthermore, not all poskim concur with the Yad Yehuda’s leniency. This author has been told by students of Rav Dovid Feinstein shlita that Rav Feinstein does not accept the Yad Yehuda’s position at all. (The great exception for melted cheese as advanced by the Yad Yehuda is absent in the classicial poskim and halachic codes.) It is thus clearly necessary to consult one’s posek as to how to deal with the matter.

Here are some common cheeses and the lengths of time for which they are aged:
Bleu: 2-4.5 months
Brie: 3-6 weeks
Camembert (French-made): 3-5 weeks
Cheddar: 2 months to 2 years or longer
Colby: 1-3 months
Edam: 3 months
Emental (Swiss Cheese-Switzerland): 6-14 months
Feta (from cow milk): brined 2-3 months
Feta (from goat or sheep milk): brined 3-6 months
Gouda: 3 months
Gruyere: 7 weeks-3 months
Monterey: 2 months
Mozzarella: 30 Days
Muenster: 5-7 weeks
Parmesan: 10-24 months or more
Provolone: 3-12 months
Romano: 5-12 months
Swiss Cheese/American-Made: 3-4 months