Intestinal and colonic bioaccessibility of phenolic compounds from fruit smoothies as affected by the thermal processing and the storage conditions

Abstract

The effects of the thermal treatment (70 °C for 2 min) and the refrigerated storage (5 °C for 28 d) of a fruit smoothie made of strawberries (40 %), orange juice (20 %), apple (10 %) and banana (10 %) on the microbiological quality, pH and soluble solid contents, color parameters, vitamin C, phenolic compound and antioxidant capacity contents, and on the total in vitro bioaccessibility (intestinal plus colonic) of phenolic compounds were studied. The thermal treatment and the refrigerated storage controlled the microbial load; and did not induce changes in the pH and soluble solid contents of the smoothies. Smoothies were slightly whiter after pasteurization and slightly darker, less red, and less yellow at the end of the refrigerated storage. Ascorbic acid was degraded by the thermal processing and during the storage by up to 50 % at 28 d, and its evolution was modeled by first-order kinetic. Thermal treatment did not produce degradation of the phenolic compounds, nor in the antioxidant capacity of smoothies, and neither elicited change in the intestinal and colonic bioaccessibility of the phenolic compounds. Anthocyanin's retentions declined after 15 days of storage, being around 40% for perlargonidin-3-O-glucoside and pelargonidin-3-O-rutinoside, and non-detectable for cyanindin-3-O-glucoside at day 28. The rest of the phenolic compounds were maintained unchanged during storage. Despite of the degradation of the anthocyanins and other polyphenols over the storage time, their bioaccessibility was not affected during the storage, indicating a possible increase in the extractability and solubility of these compounds from the food matrix by the gastrointestinal system. Anthocyanins were the most abundant phenolic compounds in the smoothies but were those with the lowest total bioaccessibility (≈1.6%). Hence, this work remarks the importance of investigating not only the content and profile of the phenolic compounds as affected by thermal processing and through the storage but also the impact on their bioaccessibility.

Keywords: Anthocyanins; Ascorbic acid; Colonic bioaccessibility; Intestinal bioaccessibility; Mild temperature-long time (MTLT) thermal treatment.