Reference for Chullin 197:18

אין בהן להעלות במאה ואחד אלא במאי לאו בששים

With regard to what did they say that every [substance of terumah] which leavens, or flavours, or is mixed with [common food], must be treated with stringency? It is with regard to homogeneous substances. [And with regard to what did they say that every substance of terumah which leavens etc.] must be treated with leniency as well as with stringency? It is with regard to heterogeneous substances. And in the next clause it reads: With regard to heterogeneous substances there is leniency as well as stringency - thus if crushed beans [of terumah] were cooked with lentils [of common food] and they impart a flavour [to the lentils], the whole is forbidden, whether there was so little [of the beans] as to be neutralized in a hundred and one or not.<span class="x" onmousemove="('comment',' This is the standard quantity for neutralizing terumah in any mixture, derived from Num. XVIII, 29; cf. Sifre on that verse. The rule here is one of stringency for even though there were a hundred and one times as much lentils as the beans of terumah, the mixture is forbidden because of the flavour that is still perceptible.');">¹³</span> If they do not impart a flavour [to the lentils] they are permitted, whether there was so little [of the beans] as to be neutralized in a hundred and one or not.<span class="x" onmousemove="('comment',' This is a rule of leniency in that the standard of a hundred and one is not insisted upon in the case where the flavour of the terumah substance is not perceptible. This lenient rule applies only to a mixture of heterogeneous substances, but in the case of a mixture of homogeneous substances conditions of stringency always obtain; and in order that a mixture of homogeneous substances be permitted, two conditions are essential, first the absence of any flavour of the terumah substance, and secondly the requisite standard of a hundred and one; v. infra.');">¹⁴</span> Now in the case where there was not so little [of the beans] as to be neutralized in a hundred and one, is it not to be assumed [that there was little enough to be neutralized] in sixty?<span class="x" onmousemove="('comment',' And in such a case the mixture would be permitted provided that the flavour of the terumah substance was not perceptible. Hence it is evident that the standard of neutralization where the flavour is not perceptible is sixty-fold, contra R. Dimi who quoted R. Samuel b. R. Isaac.');">¹⁵</span> -

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