III.5. EVALUATION STUDIES OF PERSIMMON PLANT (DIOSPYROS KAKI) FOR PHYSIOLOGICAL BENEFITS AND BIOACCESSIBILITY OF ANTIOXIDANTS BY IN VITRO SIMULATED GASTROINTESTINAL DIGESTIONMartínez-Las Heras, R., Pinazo, A., Heredia, A., Andrés, A. Food Chemistry 214: 478-485 (2017) ABSTRACTThis study aims to analyze the antioxidant benefits from persimmon leaf tea, fruit and fibres taking into account their changes along gastrointestinal digestion. The evolution of polyphenols, flavonoids and antioxidant capacity was studied using the recent harmonized in vitro protocol published by Minekus et al. (2014). The digestion was performed with and without digestive enzymes. Results showed aqueous leaf extract was richer in antioxidants than the fruit or the extracted fibres. Nevertheless, persimmon-leaf antioxidants were more sensitive to the digestive environment. In general, the oral conditions greatly affected the antioxidants, while gastric digestion led to slight additional losses. The intestinal step enhanced polyphenols and flavonoids solubility coming from the fruit and fibres. Additionally, the presence of digestive enzymes positively contributed to antioxidant release throughout digestion. Finally, the bioaccesibility of polyphenols, flavonoids and antioxidant activity of persimmon fruit were 1.4, 1.0 and 3.8 times higher than in aqueous leaf extract.

The presence of antioxidant compounds and therefore the antioxidant capacity of persimmon leaves and their extracts have been reported by many authors. Furthermore, it is known that both the method of drying and the temperature at which this process takes place substantially affect the properties of the final product. However, there are no studies in the literature that examine how drying variables can affect the quality of persimmon leaves, especially as refers to preservation of their antioxidant properties. Therefore, the aim of this paper was to compare some antioxidant properties of aqueous extracts of persimmon leaves obtained under different drying methods (shade drying, hot air drying at 100 and 180 °C, and freeze drying) and infusion conditions (70, 80 and 90 °C for 1, 3, 5, 60 and 1440 min). The results in terms of total phenol content, flavonoids and antioxidant capacity indicated that air drying at 100 °C would be the optimal process for the stabilization of persimmon leaves, and their subsequent use in brewed beverages. Likewise, the best conditions of aqueous extraction in order to maximize the extractability of antioxidant compounds corresponded to 90 °C for 60 min. A short experiment performed in this study confirmed that small persimmon leaves (axial axis: 9±1 (cm); equatorial axis: 7.0±0.9 (cm)) had around 9% more flavonoids, and 7% more total phenolic content and antioxidant capacity than the large ones (axial axis: 17±2 (cm); equatorial axis: 10±1 (cm)).

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Martínez Las Heras, R.; Heredia Gutiérrez, AB.; Castelló Gómez, ML.; Andrés Grau, AM. (2014). Moisture sorption isotherms and isosteric heat of sorption of dry persimmon leaves. Food Bioscience. 7:88-94. http://hdl.handle.net/10251/64444. BET, GAB and Caurie. The Halsey, Smith, GAB and BET models were found to be the most suitable for describing the sorption curves. The isosteric heat of sorption of water was determined from the equilibrium data at different temperatures. It decreased as moisture content increased and was found to be a polynomial function of moisture content. MOISTURE SORPTION ISOTHERMS AND ISOSTERIC HEAT OF SORPTION OF DRY PERSIMMON LEAVES Martínez

Persimmon, given its current surplus production, could be an alternative source for the extraction of certain interesting ingredients for the food industry and human health, such as fibre. Thus, the aim of this study was to analyse the influence of hot air and freeze-drying, as well as the particle size of fibre extracted from persimmon peels or pulp on their physicochemical, antioxidant, hydration and emulsifying properties, compared to commercial fibres (from peach, lemon, orange and apple). The results showed that both freeze-dried persimmon pulp and freeze-dried peel had better hydration properties and oil holding capacity than other fibres analysed, although the swelling capacity was higher for lemon fibre. Freeze-dried persimmon peel fibre showed higher values of emulsion stability than commercial fibres. Finally, the antioxidant activity of the smallest sized persimmon peel fibre obtained by freeze-drying was higher than that for lemon, orange and peach fibre.