Meta-Analysis of Studies on Vitamin C Contents of Fresh and Processed Fruits and Vegetables

The effects of processing and preand post-harvest handling on nutritional contents, vitamin C in particular, of fruits and vegetables have been extensively researched and well documented. While fresh produce is not subjected to nutrition deterioration inevitable in chemical and thermal processing, nutrient reduction due to suboptimal storage conditions and time can be substantial. Processed produce, on the other hand, incurs minimal post-harvest damage, but is subjected to damage due to chemical and thermal processing. The extent and prevalence of the resulting deterioration in vitamin C in selected fruits and vegetables have been demonstrated by many studies. While limited attempts were made to reconcile the literature findings for selected fruits and vegetables, none was made to generalize the separate findings to make inference regarding the entire category of fruits and vegetables. The objective of this review is to assimilate the literature findings to derive statistical inference concerning the comparison of vitamin C contents in fresh and non-fresh fruits and vegetables. The relevant literature was reviewed to identify publications that assess the vitamin C contents of all forms of fresh and non-fresh fruits and vegetables. Metaanalytic techniques were used to assimilate the findings and statistical analysis was conducted using mixed effects model. The results show no statistical difference between the vitamin C contents of fresh and processed fruits and vegetables. No statistically significant difference is detected, when repeating the analysis for separate processing types–frozen, canned, and juiced. The results are robust to different specifications of the statistical model.