Thermal and non-thermal processing of red-fleshed apple: how are (poly)phenol composition and bioavailability affected?

The present study evaluated the impact of different thermal (infrared-drying, hot air-drying and purée pas-teurization) and non-thermal (freeze-drying) processing technologies on red-fleshed apple (poly)phenoliccompounds. We further investigated the processing effect on the (poly)phenol bioavailability in a crossoverpostprandial study where three subjects consumed three apple products (freeze-dried snack, hot air-driedsnack and pasteurized purée). (Poly)phenolic compounds present in the apple products and their biologicalmetabolites in urine were analyzed using liquid chromatography coupled to mass spectrometry (UPLC-MS/MS). When comparing different processes, infrared-drying caused important losses in most of the apple(poly)phenolics, while hot air-drying and purée pasteurization maintained approximately 83% and 65% oftotal (poly)phenols compared with the freeze-dried snack, respectively. Anthocyanins in particular weredegraded to a higher extent, and hot air-dried apple and pasteurized purée maintained respectively 26%and 9% compared with freeze-dried apple snack. The acute intake showed that pasteurized purée exhibitedthe highest (poly)phenol bioavailability, followed by hot air-drying and freeze-dried snack, highlighting theimpact of processing on (poly)phenols absorption. In conclusion, for obtaining affordable new red-fleshedapple products with enhanced (poly)phenol bioavailability, purée pasteurization and hot air-drying representviable techniques. However, to obtain a red-fleshed apple snack with high anthocyanin content, freeze-drying is the technique that best preserves them.

This study was supported by the Spanish Ministry of Industry, Economy and Competitiveness (MINECO) through the AGL2016-76943-C2-1-R and AGL2016-76943-C2-2-R projects (co-funded by the Agencia Estatal de Investigación (AEI) and the European Regional Development Fund (ERDF)); Iziar A. Ludwig was supported by the Spanish Ministry of Industry, Economy and Competitiveness (Juan de la Cierva, FJCI-2014-20689) and 2017PMF-POST2-19 The Martí I Franqués Research Grants Programme Universitat Rovira i Virgili (Reus, Tarragona, Spain); and Silvia Yuste through a grant by the University of Lleida. In addition, the authors are grateful to NUFRI SAT (Mollerussa, Lleida, Catalonia, Spain) for providing the red-fleshed apples.