Nutritional composition, polyphenolic content and biofunctional potential of household tea waste leaves for sustainable food utilization

Abstract

Tea is one of the world’s most consumed beverages, yet its preparation generates millions of tonnes of spent leaves annually that are often discarded despite retaining valuable bioactive compounds. Here, we investigate the nutritional composition, antioxidant capacity, and antimicrobial potential of household tea residues under contrasting infusion conditions. Commercial green teas were brewed at low (20–25 °C, 12 h) and high (60–100 °C, 3–5 min) temperatures to simulate domestic practices. Cold-brew residues preserved higher levels of protein (≈20.5–21.0 g/100 g DW), dietary fiber (≈45–46% DW), and polyphenols (≈106–109 mg GAE/g DW), along with stronger antioxidant retention (>90% of baseline DPPH, ABTS, FRAP) and broader antimicrobial activity, particularly against Staphylococcus aureus. In contrast, hot-brew residues showed progressive depletion of phenolics (down to 85 mg GAE/g DW) and diminished radical-scavenging and antibacterial capacity, while lipid peroxidation markers (TBARS) nearly doubled at 100 °C. These findings reveal a dual role of infusion temperature: enriching the beverage but depleting the residue, with consequences for valorization potential. From a circular bioeconomy perspective, cold-brew residues represent superior substrates for high-value recovery of antioxidants, fiber, and antimicrobials, whereas hot-brew residues may require advanced extraction or redirection to lower-value applications. By linking household practices to waste valorization, this work reframes tea residues as a nutrient-rich biomass stream that can be leveraged for functional foods, nutraceuticals, and sustainable bioproducts