Tsegay et al. 2025 — Toxicological qualities and detoxification of fruit by-products: review
This review synthesizes toxicological data for by-products (peels, pomace, seeds) from the most globally produced fruits as of 2022 (bananas, watermelons, apples, oranges, grapes, mangoes, pineapples, avocados, and citrus), covering heavy metals (As, Cd, Co, Cr, Ni, Pb, Hg), mycotoxins, anti-nutritional factors, and pesticide residues. The review emphasizes that valorization of these by-products requires characterization and mitigation of toxicants before use in food, pharmaceutical, or cosmetic products. Key findings include that pineapple skin contained Pb beyond the maximum limit of 0.02 mg/100 g (0.64 mg/100 g dry weight was reported), while fruit by-products such as orange peel, watermelon rind, banana peel, apple pomace, strawberry pomace, and grape pomace showed Pb below 0.1 µg/L. Current detoxification trends (washing, fermentation, enzymatic processing) are reviewed alongside novel functional food applications.
Key numbers
Hazard quotient ranges reported for fruit by-products (from cited literature, not primary data): As 2.71–11.38, Cd 0.60–3.32, Cr 0.81–3.18, Co 0.03–0.09, Cu 0.09–0.26, Ni 0.08–0.34, Pb 0.83–2.23 (mg/kg, cited source not specified in text — these exceed HQ=1 thresholds, indicating individual-study concerns in contaminated contexts).
Pineapple skin Pb: 0.64 mg/100 g (dry weight basis) — above WHO maximum 0.02 mg/100 g for edible parts of crops.
Fruit by-products where Pb was insignificantly detected (below 0.1 µg/L): orange peel, watermelon rind, banana peel, apple pomace, strawberry pomace, grape pomace.
Banana peel (M. sinensis, fresh): alkaloid 0.66 g/100 g, oxalate 37.0 g/100 g, phytate 2.78 g/100 g, saponin 6.57 g/100 g.
WHO monthly intake limits referenced: Al <0.2 mg/100 g; As and Pb 0.21 mg/100 g; Cd 0.25 mg/100 g.
Fruit waste percentages: bananas ~35%, apples ~25–30%, grapes ~20%, mangoes ~40–60%, citrus ~50–70%, avocados ~21–30%, pineapples ~35–46%.
Methods (brief)
Narrative review. No primary measurements; synthesizes published literature on the highest-production global fruits (FAOSTAT 2022). Evidence quality varies widely across cited studies. Heavy metal data are drawn from secondary sources reporting concentrations in peels, seeds, and pomace specifically. Peer-reviewed: received October 2024, accepted March 2025.
Limitation: This is a secondary synthesis review (evidence tier B). Heavy metal concentrations for by-products are not systematically tabulated with sample sizes, methods, or LODs from primary studies; individual claims require verification against primary literature. Hazard quotient ranges cited without clear attribution to specific studies.
Implications
Certification: Pineapple peel has elevated Pb in dry-weight measurements; relevant if pineapple-derived ingredients (core extract, fiber concentrate) are used. Processing that incorporates peel fractions requires monitoring.
Courses: Useful for illustrating the distinction between whole-fruit contamination profiles and by-product (peel, pomace, bran) profiles — by-products often concentrate metals relative to edible flesh. The fruit-processing industry’s valorization trend increases the relevance of by-product metal content.
App: Not directly applicable for ingredient-level risk estimation; review does not provide matrix-specific ppb values in a form usable for quantitative app modeling. Use as context for derivative ingredient pages where peels and pomace are used as food ingredients.