One should not partake anything before Tiruvaradhanam. The Madhyanika period starts around 10.30 in the morning, so one can perform Madhyanikam at that time and proceed to do Tiruvaradhanam. All these can be completed by 11.30 a.m. Those who are not healthy shall do them slightly ahead of time. If one has to take medicine in the morning, they can offer Perumal milk or fruits in the morning and can partake them. Those who are fit can wait until 11 am and partake food after Ijjyai.
Food that is cooked during evenings and nights should also be offered to Perumal before partaking it.
There are certain discomforts in carrying food during a long journey, hence it is generally not permitted; if there are no other means then one can hygienically carry roti by covering the tiffin box in a cloth.