It sounds difficult to make a definitive statement based on the findings of the referenced paper:
"Overall, the vitamin content of the frozen commodities was comparable to and occasionally higher than that of their fresh counterparts. β-Carotene, however, was found to decrease drastically in some commodities."
"Overall, the vitamin content of the frozen commodities was comparable to and occasionally higher than that of their fresh counterparts. β-Carotene, however, was found to decrease drastically in some commodities."
It was occasionally lower, too.