Next in the line of preparations ahead of Onam day, come Puliinji and Kalan. Both are prepared one or two days in advance. Preparation for Kalan begins atleast one week in advance, as the curds used must be sour. So, the left over curds of each day is kept separately for a few days, so that they will be sour by the time Kalan is prepared. A commenter on the earlier Kalan recipe post, had asked about curds separating while boiling it. The trick of curds not separating while boiling lies in using sour curds. Even in warm weather the curds do not go bad, the thick curds settles down and if there is any water content, it can be poured out. This thick sediment does not go stale, even for a week. In the olden days, when refrigerators were not around, gallons of curds were prepared and kept aside for preparation for Kalan for
big feasts like marriages. In colder weather, curds should necessarily be kept in room temperature at least for 3 - 4 days.