Using the orchard-to-fork approach in designing nutritional trials: the apple phenolics case

Nutritional trials often yield inconsistent results due to the lack of standardised study designs, especially when evaluating the health benefits of fruits and vegetables. Apple phenolics, linked to various health benefits, have particular challenges in human nutritional studies due to compositional changes influenced by factors like fruit maturity, growing conditions, tissue type, and processing methods. This study applied an 'orchard-to-fork' approach to evaluate Monty's Surprise apple phenolics in the skin and flesh, controlling for harvest procedures, fruit maturity, and seasonal impact. It further assessed processing methods to preserve phenolic content, with the goal of developing a standardised material for dietary intervention trials. Monty's Surprise apples were collected over two seasons following standardised harvesting protocols and various fruit maturity parameters (firmness, starch pattern, and total soluble solids) were controlled and measured for various apple sizes. Phenolic content in the skin and flesh was analysed with LC-HRAM-MS and compared across seasons. The impacts of processing (pureeing, air drying, and slicing) on phenolic content were also evaluated. Cold storage for four weeks reduced maturity variability across apple sizes. Monty's Surprise apple skin (5270.49 ± 214.95 mg kg^-1 FW) had significantly (p < 0.0001) higher phenolic concentrations than the flesh (863.69 ± 12.71 mg kg^-1 FW), with procyanidins as the main phenolic group. No seasonal impact was observed. Pureed apples retained significantly higher phenolics compared to sliced or dehydrated samples. Monty's Surprise apple is a rich source of health-beneficial phenolics, and pureeing effectively preserves these compounds. This study offers guidance for the development of standardised apple material for dietary intervention trials to more accurately investigate the health benefits of apples.