Abstract
The vast majority of fruits and unprocessed vegetables, have a very short shelf life, mainly due to its high-water activity. Drying technology is an effective process, used to increase the shelf life of these products. It also can provide an effective method of consumption of fruits in food products. In this study, the influence of the maturation stage and drying method on the phenolic compounds and antioxidant activities of Japanese grape pseudo-fruits (Hovenia dulcis T.) were studied. The centesimal composition, reducing sugars and nonreducing sugars, ratio, color, phenolic compounds and antioxidant activity by oxygen radical absorbance capacity (ORAC) of the unprocessed pseudo-fruits, at different maturation stages (immature, in maturation and mature), were analyzed. Two drying methods were employed in the pseudo-fruits (oven with air circulation and freeze drying) obtaining flour from which moisture content, instrumental color, phenolic compounds and antioxidant activity were determined. The unprocessed pseudo-fruits of Japanese grape showed significant content of phenolic compounds at the early stages of maturation and high antioxidant capacity when mature (at the final stages of maturation). In addition, they showed a high content of fibers and sugars, and can be used as raw material in the food industry. After dehydration, the freeze-drying process provided a more stable color, because this process minimizes the enzymatic browning reactions, and preserved a greater number of phenolic compounds. The antioxidant activity, however, showed to be associated with the drying method, being higher in the flour obtained from lyophilized immature pseudo-fruits.
Highlights
This study aimed to evaluate the chemical composition, the content of phenolic compounds and the antioxidant activity of pseudo-fruits of Japanese grape harvested at different maturation stages, as well as to verify whether the oven-drying methods with forced air convection and freeze-drying affect the chemical characteristics of the flour produced from these pseudo-fruits
The pseudo-fruits were sent to the Laboratory of Food Quality of the Santa Catarina State University (UDESC), Campus Pinhalzinho, where they were cleaned by removing branches and leaves, sanitized with a 200 ppm sodium hypochlorite solution for 15 min, rinsed under drinkable running water, and the excess water was removed using paper towels
Characterization of unprocessed pseudo-fruits of Japanese grape Table 1 shows the results of the analyses of unprocessed pseudo-fruits at three stages of maturation (R1, R2 and R3)
Summary
Its blossoming occurs between August and February and its fructification from March to October. Its pseudo-fruit is a small dry rounded capsule containing from 2 to 4 seeds attached to a dark brown stalk, which is fleshy, juicy and rich in sugar when ripe (Bampi, Bicudo, Fontoura, & Ribani, 2010). Its leaves and pseudo-fruits have been used in traditional medicine from East Asian countries, where several studies have been conducted, showing their potential anti-inflammatory effect (Park et al, 2016; Choi, Woo, Ham, & Lee, 2017) and their hepatoprotective, antioxidant, antimicrobial, and antidiabetic properties (Hyun, Eom, Yu, & Roitsch, 2010; Liu, Qiang, Sun, & Du, 2015; Kim et al, 2017)
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