Well recapture of Eastern Ukraine probably didn’t bring much food anyway but increased population to feed. But I guess we do not have numbers how much food supplies they gained by liberation of Eastern Ukraine. Especially as Easter Ukraine was liberated in second half of 1943. Whatever grew there was already eaten by Germans. With Manstein implementing Scorched Earth policy during retreat Soviets actually needed to feed more population then before.
Substantial portions were recovered in the early weeks of 1943 so I don't think Manstein was able to do much with regards to scorched earth given the planting season had yet to happen. North Caucasus, however, was recovered in full in time for the aforementioned planting and thus probably explains why overall Soviet production only declined by 1% despite the Potato crop failures in the Ural region.
The Bread of Affliction: The Food Supply in the USSR during World War II, by William Moskoff -
"The central fact behind the increased importance of the collective farm market was the drastic drop in food production, especially in 1942 and 1943, and the diminished proportion that went to the civilians. In 1943 overall agricultural production was only 38 percent of the 1940 level. In 1943, however, the Red Army began to recapture agricultural areas of the Ukraine, Belorussia, and the Caucasus and by the next year, 1944, agricultural output had risen to 54 percent of the 1940 level. Not surprisingly, the collapse of the food economy led to astonishing increases in prices. The most rapid
rate [Emphasis by author] of increase in prices took place in 1942 and began to taper off in mid-1943."
As you can see, the moment the
Heer pushes the Soviets out of Ukraine and claim the Caucasus, the food situation begins to collapse; it is only halted due to the successes of the Soviet counter-offensives in the Winter, which reclaim much of the aforementioned territory. Without the reclamation, the situation would undoubtedly get worse and wasn't sustainable as is, given that starvation deaths were beginning to mount in '43 with production what it was.