What methodological flaw in one comparison study likely caused artificial leaching of folates and Vitamin C?

Placing samples in an ice-water bath post-cooking before freezing.

Nutrient analysis comparisons between cooking methods can be invalidated by procedural errors, as highlighted in one discussion concerning microwave, boiling, and pressure cooking results. The specific flaw noted was that the pressure-cooked samples were subjected to an extra step not applied to the other samples: they were placed into an ice-water bath for five minutes immediately after cooking, prior to being frozen for analysis. Because water-soluble nutrients—such as folates and Vitamin C—readily dissolve in water, this post-cooking soak artificially induced leaching specific to that preparation group. This extra immersion likely skewed the data, suggesting a greater nutrient loss attributable to pressure cooking than what would have occurred under standard laboratory conditions where only the cooking liquid was discarded.