Purim And Shmitta

Sholom from Sanhedria asks:

My wife usually sends her delicious vegetable quiches for mishloach monos.
This year, the vegetable ingredients have kedushas shvi’is. Is it
permitted to use kedushas shvi’is produce for mishloach monos?

One may not use kedushas shvi’is to
pay debts. The reason is that it looks like trading sh’mittah produce,
which is forbidden. If one “borrows” fruits or vegetables from a neighbor
who is particular that one pays it back and would claim repayment if it is not
made voluntarily, then one may not repay with sh’mittah produce. This
is an example of repaying a debt with sh’mittah produce. If the
recipient always returns what she borrows but the lender would not claim it from
her, repayment may be made with sh’mittah produce.

There are two ways in which sending mishloach monos could be viewed as
repaying a debt. (a) There is a halachic obligation to send two gifts of food
items to one person. (b) If you are sending mishloach monos to a person
who has already sent you mishloach monos in order to avoid his becoming
upset with you since you did not return his show of good will. Concerning (a),
it is known that the Steipler Gaon was particular not to use sh’mittah
produce for the first mishloach monos that he sent on Purim since he was
thereby fulfilling his basic mitzvah obligation. As to (b), there are
those who forbid using sh’mittah produce to “repay” mishloach
received from another person (see Tzofnas Paneach on the Rambam,
Hilchos Megillah 2:15 and Torah Lishmoh No.153).