Bioactive and Physicochemical Properties of Exotic Fruit Seed Powders: Mango (Mangefiera indica L.) and Rambutan (Nephelium lappaceum L.) Obtained by Various Drying Methods

Abstract

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.

A review: extraction, phytochemicals, and biological activities of rambutan (Nephelium lappaceum L) peel extract

“…found that the total phenolic content of freeze drying was 278.33 mg/g dw, which was significantly higher than those of oven drying. These results showed that freeze drying could obtain a higher retention of bioactive components and bioactivities, which was in accordance with previous conclusions ( Harnkarnsujarit and Charoenrein, 2011 ; Siol et al., 2022 ).…”

Investigating the Water Relations in Aqueous Extract Powders of Mango (Mangifera indica) Peel and Seed Waste for Their Use in Food Matrices as a Value-Added By-Product

“…By effectively managing and leveraging fruit waste, through methods such as recycling, composting, or extracting valuable substances, one can mitigate the environmental and economic impacts of surplus fruits. This approach promotes resource efficiency, minimizes waste, and promotes a more sustainable agricultural system in regions heavily involved in fruit production [ 9 ] by using surplus stocks as a resource to obtain valuable compounds for the formulation of new products and promoting an appropriate natural cycle of materials [ 10 ].…”

In Situ Inactivation of Selected Bacillus Strains in Brewer’s Spent Grain during Fermentation by Lactococcus lactis ATCC 11454—The Possibility of Post-Production Residues Management

“…They are also aware that the agriculture or food industry sector produces an excess of post-production waste, hence they are more and more open to food produced with the use of post-production raw materials [ 7 ]. Food design with the use of post-production raw materials is currently developing rapidly and concerns both post-production residue plant-origin [ 8 , 9 , 10 ] as well as animal-origin [ 11 , 12 ]. This is in line with the current zero waste or less waste trend [ 13 ].…”