The appropriate use of avocado seed waste after industrial processing could reduce the problem of overconsumption and food waste in accordance with the “zero waste” concept. The presented study evaluates the physicochemical and bioactive properties of avocado seed and its possible use in functional food design, for example, cereal snacks in the form of cookies. The profile of polyphenol and lutein content was determined by chromatographic methodology, and the phenolic compounds content and antioxidant properties of the avocado seed powder were determined using spectrophotometric methods. The chemical composition (content of protein, carbohydrates, fiber, fat) and physicochemical properties, i.e., water activity, water holding capacity, and solubility in water of avocado seed powder, were examined. According to the fiber content (21.6 g/100 g) and bioactive compounds present in the avocado seed powder (content of phenolic 62.1 mg GAE/1 g, antioxidant potential (122.4 mmol Trolox/100 g), and low solubility in water (16.2%), it could be considered a valuable additive to cereal snacks. Our designed cereal products with various amounts of added avocado seed powder (6%, 12%, and 18%) showed that 6% added powder promoted an almost five-fold increase in the polyphenol content and four-fold higher antioxidant potential of the snacks compared to the control samples. In addition, the lowest level addition of avocado seed powder increased the dietary fiber content of the product to 4%; hence, they adhered to the nutrition claim of “source of fiber” in accordance with Regulation (EC) No. 1924/2006.
Exotic fruits, which are becoming more and more popular in European countries, contain seeds, which are an unused and useless byproduct of fruit processing. Research conducted in recent years suggests that these unused waste products can be a source of nutrients and bioactive compounds in much more concentrated amounts than those found in the flesh of the fruit. Research on the physicochemical properties and the content of bioactive compounds in fruit seeds may allow the assessment of the possibility and purposefulness of their wider application in the production of functional food. Therefore, the aim of this study was to determine the physicochemical and bioactive properties of exotic, tropical fruit seed powders, such as mango (Mangefiera indica L.) and rambutan (Nephelium lappaceum L.) seeds, obtained by convective drying (CD) and sublimation drying (FD). In the tested powders, the water-holding capacity and water solubility were determined, the color was measured using the ‘electronic eye’ instrumental method, the taste profile was determined using the ‘electronic tongue’, and the content of selected bioactive compounds—such as tannins (titration method), total polyphenols and antioxidant activity was also determined using the spectrophotometric method. It was found that the studied powders were characterized by low water-holding capacity (1.2–1.6 g/1 g of powder), low solubility in water (9.5–17.4%), neutral color and varied taste profile, depending on the origin of the tested powder. Rambutan seed powders were characterized by a more bitter taste with a higher umami-flavor intensity compared to mango seed powders, which showed a more intense acidic and sweet taste. The conducted research shows that the applied methods of powder production, i.e., drying (to similar aw values) by convection vs. sublimation, had a much greater impact on changes in the content of bioactive compounds than on the tested physicochemical parameters. The freeze-dried seed powders were characterized by a higher content of polyphenolic compounds and a higher antioxidant activity than convection-dried seed powders. Considering the high content of polyphenols and high antioxidant activity, the studied powders may find applications in the production of dietary supplements and in the design of functional foods. Due to the low water solubility index, mango and rambutan powders can be used in the design of products where particle sensitivity is indicated. The use of the investigated exotic fruit seed powders, i.e., mango and rambutan, may not only be beneficial for nutritional reasons, but also may contribute to the reduction of post-production waste, in line with the recently widespread “zero waste” trend.
In recent years, there has been an increase in consumer interest in functional foods enriched with health-promoting ingredients, which include dietary fiber. Therefore, the present study investigated the functional properties of fruit fiber preparations, i.e., cocoa, chokeberry, and apple fiber preparations, then designed wheat bakery products, kaiser rolls, with these fibers and evaluated the designed products. The fiber preparations selected for the study were evaluated for water binding properties (WHC), solubility (WSI), total polyphenol content, and antioxidant activity using a spectrophotometric method. In the designed bakery products, the weight losses occurring during baking were determined, specific mass, and hardness were evaluated, and sensory evaluation was carried out using a descriptive method. The tested fiber preparations showed varying water solubility, ranging from approximately 17% for cocoa fiber to approximately 30% for chokeberry one. The highest values, both in polyphenol content and antioxidant properties, were characteristic for chokeberry fiber, at 7.0 mg GAE/1 g and 10.1 Trolox/100 g, respectively, while the lowest values were for apple fiber (1.6 mg GAE/1 g, 3.6 Trolox/100 g). Baked products, kaiser rolls, with the proportion of the tested preparations at a lower addition level (3% flour replacement) had more favorable sensory characteristics than those containing a higher proportion of fiber (6% flour replacement). Considering all the tested fiber preparations, the rolls with the addition of chokeberry fiber preparation were the most favorable in terms of sensory characteristics. As the proportion of apple and cocoa fiber preparations in the rolls increased, the hardness and intensity of the bitter taste also increased. The designed bakery products could be a valuable addition to the assortment of semi-confectionery breads (yeast doughs), where the unfavorable bitter taste could be masked by the addition of, e.g., dried fruits (cranberries, raisins), nuts, sunflower seeds, or fruit filling.
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