Why laddus are offered as prasadam to Lord Vishnu(i.e Lord Venkateswara) in Tirumala? Is there any reason or story behind this tradition.
Laddu prasadam at tirumala temple is very famous. In fact there is a geographical patent taken by Tirumala Tirupati Devasthanam(TTD). There is no reference of laddu offering to the lord in puranas. But it is said that specific timings and recipes to cook prasadams are there in vaikhanasa agama which is followed at Tirumala.
Lord Venkateshwara is known as naivedya priya meaning who is fond of offerings. Actually, Laddu is not the only prasadam at Tirumala. Besides this many prasadam like different types of rice offerings like pulihora, curd rice, different types of pongali, ravva kesari, butter, curd etc., are offered. In addition to these prasadams, kadambam, dosa made with black gram, ksheerannam, vada, rice made with pepper etc are offered to the lord at different timings starting from suprabhata seva performed early in the morning. Offering prasadams to lord started many centuries ago. In the olden days, there were not many facilities on tirumala and there was no food facilities to the devotees who visit tirumala. Then the rulers who were devoted for the service of the lord made huge amount of donations only for prasadams. As there was no food facility for the pilgrims, these were distributed among them in large scale. This prasadam was called Tiruppongam. Later many prasadams were introduced at lord's temple like appam, manoharapadi, atirasam, sukheeyam etc., But only vada was fit for preserving for a long time. Later in early 19th century, the government started distributed boondi as sweet prasadam to devotees. This was older form present laddu. This prasadam was perfect for distributing and remains fresh for a longer time when compared to other offerings. Later due to increase of facilities at tirumala and devotees visiting tirumala also increased. That boondi changed to laddupadi prasadam.
All these prasadams will be prepared at a place called potu constructed according to vastu which is near Vakula devi's shrine who is the foster mother of Lord Venkateshwara. It is believed that Vakula devi inspects whether all prasadams are prepared properly through a window. These offerings are prepared by specially appointed brahmins not wearing a shirt while preparing. There are 3 types of laddu prepared at temple.
- aasthanam laddu given only to VIP's and VVIP's[made only at special occasions].
- kalyanothsavam laddu given to devotees performing kalyanotsava seva to the lord.
prokkam laddu given to all devotees.
Some prasadams are cooked on fire place according to Vaikhanasa agama. Other prasadams which are offered to the lord are not available to sale. They are distributed to the devotees after having the darshanam of the Lord. Some other are given to devotees performing some special sevas and to VIP's. This may be a reason of fame for Laddu prasadam.
Source: This video in Telugu. Similar information was said by TTD chief priest Ramana Dikshitulu in other video but was not available on the internet.